SLA 3D Printers

First introduction

Stereolithography 3D printers, or SLA for short, have become the second most popular type of printer after FDM printers, these will be explained in the other part of this courses on 3D printers. The reason for their popularity is quite simple; the quality and detail that these printers enable simply cannot be beaten by classic fused deposit modelling printers, or FDM for short. Their prices are also really affordable now and the resin itself, while not as cheap as most filament, isn’t too expensive either. This makes it a product that most people can have at home today and gives it more and more popularity.

Practical relevance

– This is what you will need the knowledge and skills for

After this module, you’ll understand how a SLA 3D printer works and how to turn a computer design into a finished piece.

Overview of learning objectives and competences

In this module, you’ll learn how to setup the machine by calibrating the build platform, changing resin, etc. You’ll also learn how to prepare a file by slicing it in a slicer software then sending it to the machine. You’ll then learn how to take that piece and finish it by removing supports, cleaning and curing it. You’ll also learn how to troubleshoot problems on your prints or the printer and how to fix them. Then how to maintain your 3D printer to keep it running well for a long time.

Required skills for this module

Basic computer skills and 3D conception skills learnt in module 10: 3D Conception

Introduction

In this part you’ll learn how a 3D SLA printer works, the different types of SLA printers and the applications this 3D printing technology is used for.

The SLA in SLA printing stands for stereolithography. Behind this complicated word is a pretty simple concept: An ultraviolet light source is emitted under a vat full of resin. This light source will draw a layer of the print while a build plate holds the print in place. The build plate then moves up for the next layer to be drawn. This operation repeats until the whole print is finished.

Because of the resin used, SLA printing is often simply called “Resin printing”. I’ll use both terms interchangeably but they’ll mean the same thing.

Let’s go into more details about how the process works. The explanation started with “An ultraviolet light source”. This vague term was used because this light source can be created from different types of technology which will create the different kinds of resin printers:

Laser SLA
As its name indicates, it’ll make the use of a laser and a mirror to redirect and draw the layer into the resin. It’s sometimes simply called a SLA printer.

DLP-SLA
DLP stands for Digital Light Processing. In this second technology, a projector is placed under the vat to project the layer all at once in the form of a pixelated image. It’s often just referred to as a DLP printer.

M-SLA
M-SLA, or Masked-SLA uses a LED array as the light source masked by an LCD screen to create the shape of the layer also as a pixelated image. Also sometimes called an LCD printer.

Note that some people might use “SLA” to just reference Laser SLA and not all 3 different resin printing technologies. I’ll be using it in this course to reference resin printing as a whole and use “Laser SLA” when specifically talking about it. Laser SLA technology is pretty different from DLP or M-SLA. These last two will work with a grid of pixels. A single of those will then determine the smallest part that can be. With a laser the smallest part will be the diameter of that laser. Another way this impact printing is the grid of pixels is going to be the limit in terms of definition on the print but the laser one will be able to make smoother edges.

The drawback of those laser SLA prints will be the longer timer to print as the layers get bigger where DLP or M-SLA printers will take the same amount of time per layer regardless of the size. 

For example, if you only have one figurine on your build plate, the Laser SLA printer might take only 2 to 3 seconds to draw the layer where a DLP or M-SLA printer will take 8 seconds. However, if you copy this figurine and print eight of them at the same time, the Laser SLA printer will now take 16 to 24 seconds to draw a single layer as it needs to draw the figure 8 times now while the DLP and M-SLA printers will still only take 8 seconds per layer as it’s displayed all at once.

Laser SLA printers are also a lot more expensive than DLP or M-SLA printers.

DLP and MSLA printing, while similar, still differ in the way light arrives from the pixels under the vat.

For the DLP printers the projector will have the same resolution regardless of how big the layer that needs to be printed is. This means the smaller the layer will be, the more details the piece will have. Which also means the edges of a bigger layer will be of lower quality.

You can divide the size of each print by the resolution of the projector to know the size of each of the pixels.

With the M-SLA printers, the LCD screen has a consistent resolution all over the screen. This means regardless of how big or where the objects are placed. Smaller objects won’t benefit from higher details while bigger pieces won’t have edges issues like a DLP printer.

 

Picture by Lévi Ponsard

Speaking of details, let’s now talk about the main reasons why you should choose this 3D printing technology. The big advantage of SLA printing is the quality of detail it offers compared to FDM printing. The layers are much smaller and the way they are connected makes them almost invisible to the human eye. This precision in details can give different applications. First, in the medical sector, it can be used more specifically in dental applications with special resins.

Picture by Eduard Tanga

Secondly, jewellery is another application where the fine details of SLA printing can be shown off. Jewellery printed with SLA can be used as a demonstration of what a finished piece will look like. These jewellery pieces can also be printed with a resin that can be cast and then metal can be used to cast the finished piece directly.

Picture by Lévi Ponsard

Prototyping and engineering are also a third application for which SLA printing can be used. Since the result is finer than with FDM printing, parts that require higher precision in terms of tolerance can also be prototyped with SLA printers. Miniatures and sculpture models are a main driver too when it comes to SLA printing as the quality and details of these SLA prints can give you amazing results. This is a very popular use of those printers for regular users.

Picture by Luca Depolo
Picture by Marina Grigorivna

Security Measures

In this part you’ll learn how to engage with a SLA 3D printer in a safe manner.

Before we start working with the printer, there are some precautions to take. Even though an SLA printer does not get hot or have sharp blades, it does not mean that working with these printers is harmless. The main danger actually doesn’t come from the printer itself but from the material used for printing, the resin. Direct physical contact with the resin needs to be avoided. Wearing adequate gear is a requirement as not all spills will be avoidable. Nitrile gloves and safety glasses.

Picture by Lévi Ponsard
Picture by Alex from 1up-crafts

On top of direct contact with the resin in its liquid form, the fumes emitted by it are also unhealthy to breathe. The printer should be in a well ventilated room as well as not being a living room. Some printers will have an activated carbon filter to reduce the toxicity of the fume but these will decay over time and need replacement. External ventilation can also be added on the printer to evacuate the fumes elsewhere.

Setting Up the Software

In this part you’ll learn how to use a slicing software to turn a 3D design into a 3D printer readable file.

As explained in the introduction, SLA printing works by displaying an image of each layer. These images first need to be generated. To generate these you’ll need two things; a 3D file and an SLA slicer. The SLA slicer is a software that will take your 3D model and allow you to position, resize, add support and then slice the model into the set of images that will be used by the printer itself. The SLA slicer we’ll be using here is Lychee Slicer 3 which has a free version available to download on its website. 

https://mango3d.io/lychee-slicer-for-sla-3d-printers/

The latest version at the time of writing is 3.6.0 and will be the one used in these explanations. However, if your version differs, or if you’re even using a different slicer software, each part will be explained in generalities and could be applied to any SLA slicer. We’ll be using Lychee Slicer because it allows us to export files to most SLA printers on the market as well as being a very solid free software.

When you first launch the software, you’ll be asked to create an account. This will allow you to save your settings onto your account.

If you activate the “3D print history” option in the next step, you can also fall back on your print history to restore settings that worked well if you did not save them.

We should now arrive at the printer selection. You can select the specific printer you’re using here. Each printer needs some specific settings such as its size that have already been added on Lychee Slicer.

I’ll search for the Anycubic Photon S as it’s the printer that’ll be used during this course. You should, of course, select the printer that you’re going to use here. You’ll be able to change this later on or add new printers as well.

It will now load into the layout’s step:

Here’s a quick rundown of the interface:

In the top left, in red, we have the main menu, from there you’ll be able to import files, save the scene, undo an action, change the printer, and much more.
In the top middle, in yellow, we can see the different steps for the preparation of our file. Each step will have its own interface, we’re in the layout mode right now.
On the top right, in green, there’s a navigation gizmo, it’ll allow us to quickly control the navigation.
On the middle left, in cyan, we have all the tools that are dependent on the current step.
In the bottom left, in blue, we have a status report with the currently selected printer, the different printing settings as well as an estimated printing time once it has been calculated.
In the bottom middle, in pink, the current tool’s settings are available, these will also change for each selected tool.
And in the middle of the screen, we have a 3D preview of the build area as well as the models.

Talking about this 3D preview, the first thing to learn in any 3D software is how to navigate efficiently.

As said earlier, we do have a navigation gizmo at the top right of the screen but we can also use the mouse to navigate easily around the 3D preview.

If you hold right click anywhere in the 3D preview, you’ll be able to turn around the build area.
The middle mouse button, when held, will allow you to pan the camera left and to right and up and down.
Scrolling the mouse’s wheel will allow you to move the camera forward or backward.

 

You should practice by moving around the build area using all 3 types of movements. If you end up lost in the void, the navigation gizmo can take you right back to your build area. Simply click on the little home icon next to the navigation gizmo:

There’s more you can do with the navigation gizmo that I’ll let you explore on your own.

Let’s now import a 3D file into our slicer. You can simply drag and drop your file from a file explorer or use the import button on the main menu.

Important

File type: Do not forget you can’t import any kind of files. You’ll need a supported file format such as a STL, OBJ or 3MF to cite a few. You can see the full list of supported files when going into the “import” menu. You can find out how to export your file to a supported format in Chapter 10 of this learning material: 3D Design.

If you don’t have any file right now, you can use the little bird in lychee’s own library. Now that we have a 3D file imported, we can modify and edit it in many ways. The first thing you might want to do with your models is moving them around. To do so, you’ll have to activate “Move” in the tools. Once the tool has been activated, you can simply click and drag your model around the build plate. You can also use the gizmo to move on a specific axis or use the tool settings to move it precisely.

You can also use the tool settings for special movements’ shortcuts such as “Centre” which will centre the model in the middle of the build plate. “On Platform” will lower or lift the model such that the bottom is exactly on the build platform. This can be very important as without anything being in contact with the platform, the first layer won’t adhere to the build platform and the print will fail.“Arrange All” is more useful once you have multiple models on the build platform as it’ll automatically arrange them such that they’re tidily packed while also not overlapping.

Original File Position” will use the origin point of the 3D model and offset the model the same way in Lychee Slicer. This is only going to be useful in very specific scenarios where you need things to be placed a very specific way and have already set that up inside of your 3D design tool.

The next thing you might want to do is a rotation. To do so you’ll have to activate “Rotate” in the tools.

Once the tool has been selected, you can use the gizmo on your model to rotate on specific axes, relative to the camera or on all axes at the same time. Same as for moving, you can also use the tool’s settings to specify an angle on the axis you want to rotate your model.

There’s two extra options under the 3 axis. Reset Rotation” will simply reset all the rotations back to 0. Auto orientation” will automatically try to rotate the model to the easiest possible position to print. This however won’t take into account how the model will be affected visually by this orientation. I would avoid using this for models that have visual details you want to keep. We’ll learn how to orientate our models correctly later.

You might have noticed already, but there’s actually several tools hidden behind the rotate tool. You might have even selected one of those instead of rotate. On Plate” is probably one of the most useful ones as it allows you to select a specific face on your model then Lychee will automatically rotate your model to lay that face flat on the build plate. O2O”, short for object to object, allows you to select a point on an object “A” then another point on an object “B”. The object “A” will then move and orient itself from the first point selected onto the other object on the second point selected. This can be useful to assemble different parts together. Auto orientation” and “Reset” are the same options as the ones found in the tool’s settings for “Rotate”.

This is a good moment to now talk about how you should be orientating your models. There’s 4 main factors that you should think about when you’re choosing the rotation:

1. Difficulty or ease of the printing process.

To understand why some orientation might be harder than others, we’ll have to go back to some details on how the process works. For the light to be able to get to the resin, the bottom of the vat is made of an FEP film. When a layer solidifies, it’s sitting in-between the FEP film and either the build plate, if it’s the first layer, or the previous print layer. The next step is the building plate needs to move back up to detach the layer from the FEP film and also let the resin slide down under for the next layer. This detachment means that for every layer printed, there’ll be a contest for which side the layer will stick to.

The FEP film is not as sticky as the build plate or the resin itself so for most situations, the printing should stick on the right side. However, depending on the model, the previous layer could have a pretty low surface area compared to the one being printed. In that case the printed layer will have very little surface to stick on the previous layer while having a much bigger one on the FEP film, this difference can be big enough to remove the resin sticking advantage and leave the layer at the bottom of the vat. If this happens, the print will fail. The orientation of your model can help prevent those huge differences in layer’s surface area.

2. Visual fidelity of the printed model.

When printing with resin, most prints will require the use of a support structure to print correctly. Each of those supports will have to directly connect to your print. That support contact will have to be removed after the print but can leave some mark and will also not allow for details to be printed at that exact spot. For this reason you should also think about the orientation of your model so that the least important bits will be toward the build plate and get the supports.

3. Length of the printing.

For DLP and M-SLA technology, the main factor for how long a print is how tall it is. The orientation can change how tall the print is and greatly affect the printing time as well. As you can see on the example below, you can save over an hour on the same model simply by laying it down.

4. And lastly, how big of an area does this orientation take?

With resin printers, a big limiting factor is often the printing area. Depending on the orientation of your model you’ll take more or less space on the printing plate. Taking less area can mean you’ll be able to print more models at the same time if needed.

After moving and rotating your model, the last of the 3 main operations is scaling to change the size. To do so select “Scale” in the tools. 

Once the tool is selected, you can use the gizmo to scale the model in one, two or all three axes. You can also use the tool’s settings to precisely input the size through a relative amount from the model’s original size through percentages or through absolute size values. The lock icon on the left, when closed, will keep your model proportional by automatically adjusting the other two axes while you modify one. You can click on it to deactivate the option if you wish to control each axis separately.

The “Reset Scale” button will reset back to the default size of your model while the “Fit To Bed” one will enlarge your model as big as it can possibly fit on your build platform. To duplicate your models, you can use the “Copy” tool. This will bring the tool settings next to it. From here, you can set the number of copies you want as well as if you want Lychee to automatically arrange all the models after the copy. The “Mirror” tool allows you to mirror your models on either of the 3 axes.

One of the tools I skipped over, “Arrange”, is a combination of the move and rotate tools to make arranging models faster. Once activated you’ll be able to move your models on the Y and X axis as well as rotate them on the Z axis. You can also use the tool’s settings which also comes with the same “Arrange All” feature as in the move tool.

There’s more things that can be done in the layout step, such as repairing model issues, the object lists, measuring but also the “Magic” tool. The magic tool, in short, allows you to automate a lot of different steps into a single click. You can see all these steps in the screenshot below:

Instead of just using the magic tool, we’ll go over each of the steps automated by the magic tool manually to get a better understanding. As you can see it can also do an auto orientation of our models which we already covered. So now that we’re done with the layout step, let’s go on to the prepared one. By hovering over the button, you can also see what you’ll be able to do in that step. As it says the main things we’ll be able to do in this step is adding supports, raft as well as hollowing our models. Once you click on it, you’ll be able to see the set of tools on the left will change and the tool settings will now appear on the right side.

You can also see a new sliding bar appear on the right side. This is the “Layer clipping”. It’ll allow you to clip parts of your model to see each individual layer. It’s a very important tool to manually check the printing process and spot any problem. You can slide the circle up and down to preview the model up to that point as well as the current layer. You can also click on the layers to manually change to a specific layer or to go up and down a single layer with the arrow keys.

Let’s now get into one of the biggest and most important of the tools, support.

To understand the importance of support, let’s remember the printer’s process. The view inside of Lychee is actually inverted to how it’ll come out of the printer. Don’t forget that the build platform is actually facing down and the print will appear down from it. This is very important as it means that any part of the model that isn’t connected in some way toward the build platform will simply sit at the bottom of the vat. This also means that anything that’ll be printed there will then be blocked by it. This will at best result in a deformed print and at worst, which is really likely, a fully failed print past that layer. So not only every part of the model needs to be attached, it also means that the model’s weight also needs to be supported as gravity is trying to pull it down.

The third thing to also keep in mind is the same idea that was talked about for the orientation of our models. The surface area of a printed layer should never be too big compared to the previous layer that is holding on to it to be able to get detached from the FEP film and stick to the rest of the print. While orientation of your model can be a great way to help with this, support can help as well.

Now that we have some basic ideas to keep in mind for the creation of supports, let’s actually start creating some. If it’s not selected yet, select the “Support” tool.

You can now see the tool settings appear on the right. The support tool’s settings are divided into two parts, the supports’ shape and the support’s placement.

In the supports’ shape, you can modify how each support will look. You can modify their shape and the size of the different parts.

The “Shape Type” allows you to switch the shape, the different shapes are actually blocked behind the paid version of the software but they’re not all that useful as the cone will provide one of the best overall shapes for any kind of situation.

You can then change the “Diameter”. This will change how large the base of the support is. The larger the support, the more it holds itself together and the heavier it can hold a model. The disadvantage is that, of course, more resin is consumed to be printed.

Next, the “Tip diameter” is the part directly in contact between the model and the support. The bigger it is, the stronger the support will hold onto the model while also leaving a bigger mark when being removed.

Finally, the “Tip length” will change how long the cone that comes out of the base of the support is. This doesn’t have as much impact as the two other settings but increasing it can give the tip a more consistent diameter for longer length.

To help you quickly choose those sizes, Lychee comes with sizes presets:

  • Light will create very thin supports, these are good for miniature making as they won’t leave much of a mark on the printed model. They’ll, however, be too weak to hold much bigger prints.
  • Medium is a good middle ground for most prints and will be the one I use for this small bird I’m printing.
  • Heavy should only be used for much bigger and heavier prints if you need the extra strength to hold such weights as they’ll use the most resin and leave the biggest marks.

Practical Tip
I strongly recommend that you start with one of these 3 presets and then change them slightly if necessary. These default settings should cover most situations you find yourself in.

Now that we know which kind of supports we should be using, let’s look at how to actually place those supports on our model. You can actually just click somewhere on your model to place a support at that spot.

However, adding the full support structure manually will both take a very long time and is likely to leave you with some problems such as leaving parts unsupported or not having enough support to hold the whole model to name a few. This is why the second part of the support settings exist to automate and streamline this process.

As you can see at the top, this part actually has 5 different tabs. The first one, “auto” will allow us to automatically create a support structure for the whole model. It usually does a very good job and can mostly be relied on. You can retouch, add or delete some supports if necessary.

There’s two sliders that you can directly change in this window but also more if you click on the little cogwheel next to “Auto Supports”. We won’t go over those here but we’ll talk about each of the concepts in the “manual” tab so you can understand and edit them if need be.

Supports Density” as its name indicates, will allow us to change the density of supports by adding more or less support. A higher density means that the model will be supported better but will also come at the cost of more used resin as well as adding more contact points onto your model.

For this model, either the low or normal options are more than enough as the model is very small and light.

Search for ground” will set how far away the supporters try to go to attach themselves to the build platform instead of coming out of the model itself. Connecting to the ground means there will be only one contact point on the model instead of two but going out too far away to find ground can weaken the supports and fail to print.

I’ll stay with the default settings of normal density and 20 mm. We can now click on “Generate Automatic Support”. Lychee will then go through several steps. You can observe the result of each of these steps as they appear on your model.

Once Lychee has done the calculation, it’ll give you a report on every step it took to build the support structure. It’s good to understand each line here as it’ll allow you to spot issues as well as getting a good idea for all these concepts.

50 supports added” simply refers to the number of supports Lychee added to your model.

 

4 supports were not placed due to not finding a place to go” refer to spots Lychee thought supports were needed but weren’t able to be placed. If this number is higher than 0, it’s a good idea to check your model to see if there isn’t any obvious spot that still needs some support. You’ll be able to add some back from the “manual” tab.

3 island supports added”. Islands are a very important concept in SLA printing. An island is any part of the model that, at the time it’ll be printed, isn’t connected to the build platform through the rest of the model or a support structure. It’s imperative that every island is being supported.

In this example, even if the left part of this model is attached to the rest, at the time of printing it, it’s a separated island and will need to be supported one way or another.

0 island supports were not placed due to not finding a place to go”. As it was just explained, no island should be not supported, so if this number is ever above 0, you’ll need to find those islands and deal with them. The tab “island” will help you spot them.

15 supports optimised”. Optimised supports make the use of a nearby support structure to use the same base as them instead of starting from the build platform.

72 bracings added”. Branches refer to the small diagonal bits that are added in-between supports. These are an integral part of creating a solid support structure. Without them, each support stands on its own and is very weak but adding braces in-between them, will multiply their strength.

Let’s now have a look at the support structure that was automatically generated on our model.

Overall it looks really decent but I’ll be adding a few more supports in the part that seems to be in need. To do so, as we learned earlier, I can just click wherever I think support is needed. I’ll also switch to the second tab in the support placements, “manual”.

From this menu, we have some extra options to help with manually putting down supports. The mirror one can be very useful if your model is mirrored on one axis so you can place one support and its mirror one will automatically be placed too.

The “parent” button does the support optimization that was done automatically earlier. And the “bracing” button will add braces where you need some. We’ll use those two buttons after we’re done adding extra supports. On your model itself, you might have noticed some parts now appear in a yellow and orange checker.

These parts are what Lychee considers “overhangs” as the angle of those faces are starting to be really low and likely to need support. However, it doesn’t instantly mean that parts with the yellow and orange checkers won’t be able to be printed correctly without support. Lychee start displaying faces this way from a 45° angle or lower. In this model, a lot of these displayed overhangs are just barely 45° or lower and also don’t extend very far, which is why I won’t need to add extra supports on those.

Here’s what my support structure looks like after adding and removing supports.

I’ll quickly go over the “island” tab and skip the last two as they’re not as needed right now. From here, you can search for any islands that’s left on your model, show them and then add supports to remove them.

Let’s now go onto the second tool of the preparation step, “Raft”. Once selected we can see a bunch of different raft pre-sets appear on the right. So what is a raft good for? 

At first hand, it might seem like an unnecessary addition to the printing process that’ll use more resin than we need but it actually has a few pretty important uses. The main one is to create a large uniform area of contact onto the build plate, this will both help to adhere to the build plate as well as solidify the support structure. However you need to be wary of creating too large of a solid area as you might run into warping issues. We’ll talk about those later.

The second big usage of the raft is to create an easier-to -remove structure from the build plate once the printing has been completed. I won’t go to every single one of them, you can check those on your own. I’ll be using the very last one as it allows me not to waste too much resin by following the shape closely while also having a very nice bevel on the edges to remove it from the build plate.

The third and last tool in preparation is the “hollow” tool. This hollow tool will allow us to hollow out our model as well as create holes on our model. There’s 2 main advantages to hollowing your model.

  • The main one is saving on resin, the bigger your model is, the more resin you’ll be able to save by hollowing it.
  • Hollowing your model can also help with the printing process. The hollowed out layers will have a smaller surface area which will help them not stick to the FEP film as much. However a hollowed print can create a pressure difference creating a suction effect which can make it actually stick even harder than without any hollowing. We’ll talk about how to fix that in the “Holes” part. 

Other things to take into account when hollowing your model is that it’ll be lighter and if you’re using translucent resin, the interior infill and shell might be visible. If you’re using translucent resin and want the inside of the model to be fully solid or you want your model to have its full weight, then you can keep hollowing turned off. Now that you can make a decision on hollowing out your model, let’s see how to actually do it. Once the hollow tool is activated, you can navigate to the “Hollowing 2D” in the tool’s settings.

To hollow your model, simply turn on the hollowing by clicking the on switch. You can then change the shell’s thickness as well as how much infill you want and the size of the cylinder used in the infill. Infill will probably be needed for most models to keep a good structural integrity of your print but also to support the interior roofs of the model during the printing process. You can use the layer clipping to have a good view of what the current settings will do on your model.

Now that our print is hollow, let’s talk about holes. Holes play two important roles in resin printing.

First, as we’ve seen when talking about hollowing, this hollowing can create a suction effect. As the print is lowered onto the FEP film to print the next layer, there’ll be a pressure difference between the inside and the outside of the print. This pressure difference will create a suction effect which will make it harder to detach the print from the FEP film. By adding holes at the bottom of your print. Air can freely flow in and out of the print creating no pressure differences and removing the suction effect.

The second positive impact of adding holes is the possibility to drain uncured resin left inside the model. The downside is that you now have holes on your print. For this very reason, and since the holes should be placed as early as possible in the printing process, you should also take this into account with how your model is oriented. You can also use some of the resin to fill the hole and then use the UV light that’ll be used in the post processing to cure that extra resin.

Now that we know why and where we should be adding holes, let’s open the “Holes” tab. From here you can select which shape you want your holes to be as well as the diameter of the hole and the penetration for how far it’ll dig into the model.

The diameter depends mostly on the viscosity of the resin you’re using as more viscous ones will need a bigger hole to drain out. 1.5 to 3 mm should be more than enough for most resin used in M-SLA and DLP printers. Laser-SLA printers often use much more viscous resin that might need up to 5mm holes to drain properly.

The penetrating length only has to be long enough to ensure that you get through the entire shell. However, make sure you don’t choose too big a value and come out the other side. Once you’ve selected your values correctly, you can start placing holes on your model. As said earlier, placing them as soon as possible in the printing process will allow air to flow as soon as it needs to and avoid any suction effect.

Here’s where I’ll place them on this model. Two holes is usually all you need to keep a good airflow and easy drainage. You’ll only need more than two holes if the model is shaped in a way that can create different pockets of suctions that aren’t directly connected at the start of the print. Don’t forget to check the layer clipping again to see what you’re cutting into with those holes. You should also go back to island detection in the support tool to make sure the holes you created didn’t create any island.

Now that we are done with the “Prepare” step. Let’s move onto the “Export” step. This step is all about previewing the printing process with different tools then exporting it to our 3D printer and more. This step works a bit differently than the other, the tools are simply just all different ways to preview the process while the “tool’s settings” will remain the same export options.

With the first preview function “Split” you can switch between the view of the whole model, the view below the selected layer and the view above the layer.

I’m not going to go over every single preview mode here, you can simply try them by yourself by selecting each tool then going up and down the layer clipping. Once you’ve tried those quickly, let’s go straight to the exporting options:

As you can see, there’s 3 sub-menus in here to export different things.

  • The first one, “Slice” are the slicing options where we’ll be able to configure the printing and export the file we’ll use on the SLA 3D printer.
  • The second one, “Export 3D” allows us to export our model to an .obj or .stl file. This allows for further retouching on any 3D design software or simply to share a model with the support structure already made for it.
  • The last one, “Export Scene” , will save a scene file specifically made for Lychee; this will save every setting that was set for this specific scene.

Let’s take a deeper dive into the Slice options. The name “slice” comes from the action performed to create the print file. The slicer software must slice the model to create an image of each layer. The first thing visible in the Slice options is the “Print Time”. This print time is an estimate made from the printer selected, the resin settings as well as the model’s size. Secondly, you can change the “Printer”. We should already have this set up correctly, but it’s a good idea to make sure you have the right one selected on this screen and change it if needed.

Third one is going to be the big one. “Resin” is going to allow us to change all the printing settings. Let’s click on it to open the printing settings. A new window will open with both the printers and resins settings.

Let’s focus on the “Resin – Printing Settings”. From here we can:

  • Add New Resin”, which will add a new resin profile that we can quickly use again later.
  • Import” allows us to import resin profiles that we previously had exported or downloaded from the internet.
  • Export” which will export our resins profiles so we can share them and import them into another account.
  • Edit” to edit a previously added or imported resin profile.

Let’s go straight to “Add New Resin” to view and understand all the settings. This will open yet another window with community resin profiles but also the ability to set a profile from scratch.

These community made profiles are actually a very good starting point to find working default settings for your specific printer. I will actually be using the most popular settings in this list and then explain each setting from there.

Select the right printer here and click on “Copy”.

Lychee will now open a new window with all the imported settings so we can review them and make adjustments before saving the profile. So let’s review and understand each of these settings.

First, we can change the name, brand, colour, and add a comment to the profile. As I’m going to use this as a default profile for most resins, I’ll keep all of those as just “Default”.

The burn-in Layers, also sometimes just called bottom layers, are the first layers to be printed. These few layers need a longer exposure time to assure a good adhesion to the build plate.

  • Number of Layers” is simply the number of layers that will have that extra exposure time. A value of 3 to 6 is recommended here. If you specify more than this value, the printing process will not be significantly improved and the layers will become more brittle and the printing time will be longer.
  • Exposure Time” is the time each of those burned in layers will be exposed to the light. This time can depend a lot on each printer, from 20 to 60 seconds usually.

The normal Layers are simply all the other layers after the burning layers until the end of the printing process.

  • Layer Thickness”, as its name indicates, is how thick each layer will be. The two main impacts of this are the quality of the print and the time it takes to print. A small layer thickness means more layers need to be printed for the same print size which will both add details to the print but also a lot of time. While a big layer thickness will do the opposite, less total layers so less details but also faster prints. 50 microns is already only 0.05mm which is already thinner than most human hair. Going much lower than this won’t give you that big of a perceivable difference in quality while multiplying your print time exponentially. In the opposite direction, you shouldn’t go much higher than 100 microns or 0.10mm as too big of a gap could decrease layer adhesion and fail the print.
  • Light-off Delay” is a small delay you can add before the screen turns on for the next layer after the build platform has lowered down. This usually can stay at 0 as anything above will extend the print time heavily. However, this can sometimes be used to correct printing errors.
  • Exposure Time” is the time each normal layer will be exposed to the light. This will usually be a value in-between 7 and 10 seconds on older M-SLA printers but newer ones have monochrome screens that are much stronger and allow the exposure time to go down to 2 to 4 seconds instead. You should read on your specific printer to know what kind of time you can set here.
  • Lift Distance” is how far up the build plate will go between each layer. As explained plenty of times before, after each printed layer, the build platform needs to go up to detach the print from the FEP film before going back down to print the next layer. A lift distance too low could mean the print isn’t able to detach from the FEP film, which would fail the printing process. While a lift distance too high will also add unnecessary time to the printing process.

The speed settings are simply how fast the build platform will go up and down.

  • Lift Speed” is how fast the build platform will lift up after printing a layer. As the print has to detach from the FEP film, this operation can be quite delicate and shouldn’t be done too fast as it can fail the print.
  • Retract Speed” is how fast the build platform goes back down after going up. As the print is already detached at this point, this retract speed can be much higher which is why it’s set almost 3 times as fast as the lift speed.

The exact scale of your printed object can sometimes be slightly off from the sizes said on the computer. These small differences in scales can be caused by multiple things. If your prints need very precise measurements, I’d suggest using a very precise calliper and printing a few different calibration models. You can then change these 3 scaling options according to your results to get more precisely measured prints in the future.

The price settings don’t really have any impact on the actual printing. This just allows you to get an estimation on how expensive it’ll be to print your model as far as how much resin it’ll be used. You can change the price, currency as well as the bottle capacity of your resin to get a really close estimate.

This print time override allows you to override the default way Lychee will calculate the print estimate. This can get you a much more precise time estimate if you know the exact values. These, however, won’t have any impact on the actual printing time, just the estimate given by Lychee.

Once every setting has been taken care of, we can finally add the resin profile to our list by clicking “OK” at the bottom of these settings.

Our profile should now appear in our resin list and be pre-selected already.

Once the right resin is selected, we can finally close the printers and resins window.

The next slicing option we can change is the “Anti-aliasing”. So what is “Anti-aliasing”?

Anti-aliasing is a method to smooth out edges on an image to remove what’s called the “stair-case” effect, also called aliasing. As you can see, this smoothing is done by having a gradient on edges instead of going straight from black to white pixels. As this staircase effect can also be visible on M-SLA or DLP printed parts, anti-aliasing can also help here as edges won’t be as harsh on the layers and this will also smooth out the edges of the print. However, this can also have the effect of smoothing out very fine details on the print. Either on or off, the anti-aliasing won’t have that big of an impact on the final result to the human eye.

Finally the last step is to actually export the sliced file for our printer to use. As the printer I’ll be using, the anycubic photon S, uses USB drives to read files, I will insert the USB drive before the exporting process. This allows me to already select it in the “Destination” setting. The “Slice Format” should give you options that are readable by your printer then all that is left to do is to click on the “Export slices…” button at the bottom.You can change the name of your file then click “OK” to export it. Lychee will then render every layer and give you a preview as it’s doing so. 

When it’s done, you’ll get a report of the slicing. You can see how long it’ll be to print, how much resin it’ll use, and how expensive it’ll be to print. You can also save the export in your history so you’re able to quickly go back to it and see all your settings and even import those settings into a new print.The two buttons at the bottom either let you “Open Folder” to see the exported file in its folder or “Eject media” so you can directly remove the USB drive to place it into your printer.

 

Setting Up the Machine

Picture by Lévi Ponsard

In this part you’ll learn how to setup a SLA 3D printer and start a print.

Let’s meet the printer!

This is the Photon S from Anycubic. A very cheap but popular M-SLA printer that gives very decent results. First things first, let’s start by plugging in the printer and turning on the switch. If the printer has already resin in the vat or is dirty, please refer to the chapter 7 , maintenance, of this learning unit before proceeding.

There aren’t too many steps to setup an M-SLA printer but it is imperative it has been done correctly. Calibrating the build plate isn’t too hard of a process but there’s a few things to think about while doing it.

Picture by Lévi Ponsard

We’re going to both have to level it so it’s perfectly straight in comparison to the bottom. As well as set the height correctly. It’s not required to do this step before every print. If it has been calibrated already, you can do multiple prints before having to redo it again.

To calibrate the build plate, we’ll first need to remove the vat from the printer. To do so, simply loosen these two screws until you’re able to slide off the vat.

Picture by Lévi Ponsard

For the next step, we’ll need an Allen key to loosen the build platform to allow it to rotate freely.

Picture by Lévi Ponsard
Picture by Lévi Ponsard

A piece of paper will be needed next, make sure it’s of the right size so you’re able to insert it in the printer as such. For this particular printer an A5 sheet is perfect for the job. This sheet of paper will allow us to create a separation between the screen and the build platform. It’ll also allow us to set the exact height.

We’ll first need to lower the build platform to its home position. To do so, navigate on the screen to “Tools” then “Move Z” then finally press the house icon.

Picture by Lévi Ponsard

The printer will then automatically lower the build plate until it’s sitting a few millimetres above the sheet of paper.

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We’ll need to close that gap. As you’re already in the “Move Z” menu. You can lower the platform manually. You should start by selecting 1mm.

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Then go down a few steps until it looks like the build platform is making contact with the sheet. Before proceeding, make sure that the building platform is straight when viewed from above.

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Once it’s straight, you can go back onto the screen and switch the step to 0.1mm.

Picture by Lévi Ponsard

Then lower the platform some more until the build platform sticks the sheet of paper and itself in place. You can make sure that’s the case by trying to move the piece of paper, it shouldn’t be able to move.

 

Picture by Lévi Ponsard

When the build platform is stuck to the bottom. You can screw back the top with the Allen key. While you’re doing so, use your other hand to hold the build platform down and flat by slightly pushing on both sides at the same time. This will ensure the build platform will stay levelled as you screw it back in place.

Picture by Lévi Ponsard

When the build platform is locked into place, we can now start to raise it back. To do so you can stay on the 0.1mm step and start clicking the up arrow.

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While you’re pressing the up arrow with one finger, you should be using the other hand to pull into the sheet of paper. The right height will be when you’re able to move the sheet back and forth under the build platform while still feeling a tiny amount of resistance. If you can pull on it but it doesn’t slide back forward, the platform is still too low. If you can slide the sheet of paper without any resistance, then you’re now too high and you should go back down.

Once the height is perfect, we can set it as the new value for the origin point of the Z axis. To do so, make sure you don’t move the build platform anymore and go back to the “tools” menu and press “Z = 0” then “Enter”.

Picture by Lévi Ponsard

Once that’s done, you can go back to the “Move Z” menu and go up with 10mm steps until you have room to put the vat back in and lock the two screws. Don’t forget to also remove the piece of paper!

Picture by Lévi Ponsard

We’re now almost ready to print. There’s one more thing that you’ve probably realised is missing right now, the resin! Before we pour the resin inside the vat, make sure the build platform is high enough so it doesn’t block you. Be careful that some printers might not automatically stop when reaching the top. So if you do that by mistake, you might need to redo the build platform calibration step again. I always make sure there’s a few centimetres left over the build platform on the Z-screw.

Picture by Lévi Ponsard
Picture by Lévi Ponsard

Let’s now take a look at our resin.

We’ll be using the Anycubic grey resin for this print. The two main things you should be looking at when using resin is the wavelength and the expiration date. You should check on your specific printer what kind of wavelength the resin needs to react at. While it’s most of the time 405nm, it’s still better to check your printer’s specs in its manual. The expiry date is also very important, because an outdated resin is the cause of many problems. 

You can already wear your protective nitrile glove for this operation but you shouldn’t make a mess already. Before pouring the resin in, it’s important to shake it for a few seconds as some parts might separate if it sits still for a while.

We can now open the lid and pour some resin into the vat. Don’t forget the build platform will need to lower itself into this vat. Doing so will displace the resin. So if you put too much resin in (so that it is close to the edges) the resin will most likely go over the edges.

A lot of vats will have a maximum line drawn somewhere. As there is none here I’ll make sure I never get closer than around 1cm from the top. As this print doesn’t need too much resin, I won’t need to pour too much anyway. Any extra resin left in the vat after the printing process can be reused.

Pictures by Lévi Ponsard

Practical Tip
Try to get into the habit of closing the lid of the resin and the lid of the printer as soon as you have finished your work. The resin does not react immediately to light and solidify, but if you leave it open for a long time, it can definitely have negative effects. The best way not to forget it is to take care of it as soon as possible.

So let’s close the lid on the resin bottle as well as the top of the printer. We can now insert the USB drive with our printable file. Let’s navigate back to the main menu then to PRINT then select our file in the list. The only thing left to do is to press the starting button.

Picture by Lévi Ponsard
Picture by Lévi Ponsard
Picture by Lévi Ponsard

The build platform will now automatically go down then light up the screen when it’s sitting at the right height. As the build platform will be hidden by the vat as well as the resin itself, you can’t see if a print has failed or not until a few hours into the print. 

Picture by Lévi Ponsard

There is one more thing you should check, however, and that is that an image is displayed on the very first layer. If the first layer is blank then the print is going to fail regardless. In this unlikely case, stop the printing process and verify your file before trying again. The mistake is likely that the model itself is slightly above the build plate in the slicer. The display screen should give you a preview of the currently printed layer. Now all we need to do is to wait until the print is finished.

Pictures by Lévi Ponsard

Post-Processing

In this part you’ll learn how to remove the print from the build plate as well as cleaning, removing supports, curing and coating the model to get a finished piece.

Before we even think about taking out our print from the printer, there is a lot of equipment you should prepare. Let’s review the list.

Nitrile gloves

Probably the most important part, as already mentioned, is that the resin in its liquid form is toxic to the skin. You should always wear gloves when you touch it, especially when you take the printout of the printer, as this can be the dirtiest part. Latex gloves can also be used if you don’t have nitrile ones.

Picture by Lévi Ponsard

Protective glasses

Just as important as the gloves is the protection of the eyes when you work with resin.

Picture by Lévi Ponsard

Cleaning paper

You’ll be needing a lot of cleaning paper to take care of the messy aspects of this process.

Picture by Lévi Ponsard

A silicone mat or an easy to clean surface

You don’t want the resin to drip onto surfaces that won’t be easy to clean after. A silicone mat used just for your resin printer will allow you to keep the rest of the room clean.

Picture by Lévi Ponsard

A metal spatula

To scrape off the print from the build platform. Never use this on the FEP film.

Picture by Lévi Ponsard

Isopropyl alcohol 

Isopropyl alcohol, or IPA for short, will allow us to both clean our prints as well as our printer.

Picture by Lévi Ponsard

A washing station or ultrasonic cleaner or a watertight recipient

There are pre-made washing stations for cleaning your resin prints. If you do not have one, you can also use a waterproof container.

Picture by Lévi Ponsard

A recipient with water

Also needed as part of the cleaning process.

Picture by Lévi Ponsard

A pair of precise cutting pliers

To remove the support structure if it doesn’t come off easily.

Picture by Lévi Ponsard

A curing station

A curing station is really just a box with LEDs and a rotating platform that is switched on with a timer. This finalises the curing process of your prints. There are other alternatives if you don’t have a pre-made curing station such as making your own with UV LED or simply using the sun as your UV source.

Picture by Lévi Ponsard

Make sure all this equipment is prepared and easily accessible before starting this whole process.

Let’s start by loosening up the big screw on top of the build platform so it can be removed from the rest of the printer.

Pictures by Lévi Ponsard

Be careful that some resin will probably be left on the build platform and drip down as you move it. You should lean the platform over the vat so the liquid resin can drip in the vat and not elsewhere.

Pictures by Lévi Ponsard

You can then place it on the silicone mat as such.

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From here, let’s detach the print from the build platform. If it doesn’t come out easily, you can use the metal spatula under the raft of the print. Make sure that it cannot slip off the silicone mat.

Pictures by Lévi Ponsard

Once the print has been detached, the next part is to clean it from the small residue of resin that has been left on it. This is where the IPA, water, and washing station come into play. If you own a washing station, you can put your print in the basket and lower it inside the container.

Pictures by Lévi Ponsard

You can then pour enough IPA to cover your print.

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Then when that’s done, close the lid and start a washing cycle.

Pictures by Lévi Ponsard

As you can see there’s several pre-set timers for a washing cycle. The length it should take for one washing cycle is going to depend on how intricate your printing is and how much resin was left on it. I’ll use the middle value of 10 minutes for this one.

Practical Tip
Clean as early as possible. As you have to wait until the wash cycle has gone through, you can use this time to clean the rest of the equipment and the machine. I invite you to go over to the maintenance part of the courses to know how to do it properly.

When the cycle has finished, you can lift the basket to get access to your print. You can keep the IPA for several prints until it gets dirty, because if you change it for every print, you will use an excessive amount of IPA. Don’t forget to put on the watertight lid on top so the alcohol doesn’t evaporate. If instead, you own an ultrasonic cleaner, you can make use of it here too. Put the print inside the basket then cover it with IPA. Here you can also set the timer for your wash cycle. Around 5 or 6 minutes should also be enough. Don’t forget to also close the lid so you can start the cycle.

Pictures by Lévi Ponsard

An ultrasonic cleaner works by emitting high-frequency sound waves through the liquid solution. These frequencies will agitate the liquid and allow it to scrub even the smallest details. This makes an ultrasonic cleaner one of the best ways to clean very detailed parts. However it’s not a required tool to own for the process. If you don’t have either of those two tools you can still clean your prints in a much more manual way.

If your print is pretty solid and doesn’t have very small parts that could break off, you can just put it in a waterproof container with some IPA and then shake it well for 2 minutes.

Pictures by Lévi Ponsard

However, if it does have parts that could break during that process, you’ll have to use an open container and manually clean it. You can dedicate a toothbrush for this kind of job. Just make sure it’s never used for anything else after.

Picture by Lévi Ponsard

Once the print has been cleaned with IPA through one of these 4 methods, you can rinse it in a container full of water. The water should get blurry as the last bits of resin detach from the print.

Picture by Lévi Ponsard

Now that the print has been fully cleaned, let’s remove the supports. They should come off pretty easily just with your hands. 

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If some cannot be removed or small pieces remain on the print, you can cut them off with precision cutting pliers.

Picture by Lévi Ponsard

If your print is hollowed out and has holes, the uncured resin trapped inside will want to flow out of the holes. You should position the print so that the liquid resin can easily flow out of the print. Make sure that the underlay under the print can absorb the liquid resin at this stage. The last required step of post processing is curing. The print is actually not fully cured when coming out of the printer so it’ll need to spend a few more minutes curing to get the final properties of your resin. If you own a curing station you can place your print on top of the turning platform.

Picture by Lévi Ponsard

We can now set a timer for how long we want to cure the print for. I can vary in-between 2 and 5 minutes depending on how big your print is and if you’re using translucent resin instead of opaque one. Smaller and translucent will need a lower curing time. For this particular print, 4 minutes should be plenty enough. If you do not own a curing station, you can actually use the sun as well for this curing process. However it’ll take longer and you’ll need to manually turn the print every few minutes to make sure your print is cured uniformly. If you use sunlight, it should take about 3 to 4 times as long. Be careful of over-curing your print as it could make the thinner part more brittle.

Now that the washing and curing is done, the required steps are complete. However you can still go one step further by sanding support contacts and painting the model. Before adding any type of coating on our print. It’s important to make sure none of the support contacts are still visible.

Picture by Lévi Ponsard

You can use a Dremel with sanding bits. You’ll have to be really gentle as adding too much force can easily eat into your print.

Picture by Lévi Ponsard

You can also just use sandpaper and manually go over the support contacts. That process will take longer but also has lower risks. I’d suggest a very fine grit level of 1000 or more to achieve a smooth result. Once you’re done with the sandpaper smoothing, you can use some microfiber cloth to clean the fine powder left on the print.

Picture by Lévi Ponsard

To get paint to stick on your print you’ll first need to apply a primer layer then you can apply other layers.

Picture by Lévi Ponsard

Another finish you can add to your resin print is a clear coat to increase the transparency and glossy look.

Picture by Lévi Ponsard

Troubleshooting

In this part you’ll learn how to spot printing errors as well as how to fix or avoid them in future prints.

SLA printing won’t always give you perfect results. It’s good to be able to spot issues, know why they happened, and how to fix them. A lot of the fixes are actually often things that have already been talked about so if you’ve already been paying good attention and doing everything properly, the number of issues and failed prints should be really minimal.

Print doesn’t stick to build plate

Picture by Lévi Ponsard

Prints not sticking to the build plate is probably the most common issue but also one that could be the result of many different reasons and as such, will also have many different fixes. You might have to try to find out the particular reason it didn’t stick for you. Don’t forget to clean your vat of any stuck part on the FEP between each try. To do so check the maintenance part of this course.

  • Calibrate your build platform
    The main reason your print might not stick to the build platform could simply be due to an improper calibration. I’ll invite you to go back to the printer setup part to redo the process.
  • Check your sliced file
    It’s possible you might have moved your model up on the slicer software, if you do so right before slicing it, the first layer won’t have anything printed on it, which means it won’t be printed right against the build platform. 
  • Switch the resin
    The resin could be the culprit for a print not sticking to the build plate too. Always make sure it’s not out of date. However, even if it’s not out of date, it’s possible it has been contaminated due to improper handling or is simply a bad quality resin. 
  • Clean the build plate properly
    If the build plate isn’t well cleaned and there’s a fine layer of anything on it, it might get stuck in-between the print and the build plate. This will lower the adhesion and will make it more likely for the printed layer to stick to the FEP film instead.
  • Change the FEP film
    Check if your FEP film is still in a good state, a roughened up FEP film will add adhesion to itself which will make it harder for the build plate to detach it. To change the FEP film, check the maintenance part of this course.
  • Use PTFE lubricant on the FEP film
    Another way to reduce the adhesion between the FEP film and the print is to add a thin layer of PTFE lubricant on top of it before pouring in the resin. This is usually not needed and you also need to be careful not to add too much as it risks mixing with the resin. 

Print doesn’t stick to supports

Picture by Lévi Ponsard

Sometimes, at the end of your print, you’ll be left with only the support structure and seemingly no model. It might be easy to feel like the sliced file had a problem and only had the supports come out but it’s a lot more likely the problem was actually due to the model detaching itself from the supports. There can be several reasons for this but the two main ones will often be either the model was too heavy for the supports or the layers the model started to print had too much contact with the FEP film in comparison to the supports. On top of these tips to not have this happen again, make sure you clean your vat and the FEP film as the rest of the model will probably be sitting on top of it. To do so check the maintenance part of this course.

  • Hollow your models
    Hollowing your models is one of the easiest ways to reduce the weight on bigger models. With a less heavy model, the supports will be more likely to hold on to it. If you hollow your model, make sure you go back to the hollowing part of this course.
  • Add holes to your hollowed model
    If you have hollowed your model, it’s imperative to have added holes. A hollowed out model with no holes will create a suction effect, adding a lot a lot of stress to the supports and making them more likely to fail. Make sure to go back to this part of the course for a more in-depth explanation. 
  • Change the orientation of the model
    As one of the reasons the model could be detaching itself from the print is the difference in the surface that’s touching the supports versus the FEP film, the orientation can definitely help with this. Make sure to go back to the courses for a more in-depth explanation.
  • Increase the support density
    While the orientation and the weight of the model has an impact on how easily the supports will hold onto your model, the density of them can be really important too. The more supports, the easier it’ll be for them to hold the model, at the cost of more contact points onto the model itself. 
  • Increase the contact diameter of the supports
    The contact the supports have with the model are very small points to make those contact points not stick out too much when the supports have been removed. However, that very small contact can also mean the supports have a very hard time holding onto the model. Slightly increasing that diameter can also help.
  • Change the FEP film
    Check if your FEP film is still in a good state, a roughened up FEP film will add adhesion to itself which will make it harder to stick to the supports as the build plate goes up. To change the FEP film, check the maintenance part of this course.
  • Use PTFE lubricant on the FEP film
    Another way to reduce the adhesion between the FEP film and the print is to add a thin layer of PTFE lubricant on top of it before pouring in the resin. This is usually not needed and you also need to be careful not to add too much as it risks mixing with the resin. 
  • Check your sliced file
    While very unlikely to be a software or file issue, you should make sure your sliced file actually contains the model by previewing all the layers and see if only the supports are actually there.

Layer detach mid print

Picture by Lévi Ponsard

Layers detaching in the middle of the print can usually be caused by either too big of a layer height or too slow of a curing time. Both of those things will lower layers of adhesion. While those two things can be the cause of layers detaching, it’s also possible it’s caused by other factors that we’ve already gone through in previous issues.

  • Lower the layer height
    If you’ve increased the layer height too much to speed up your print, it’s possible those layers are now too far apart and the adhesion in-between layers will be affected. A layer height of 0.1mm is still doable but it’s not advised to go higher than that.
  • Increase curing time
    If the curing time is too low, the resin won’t be cured and solid enough, making it much easier for them to detach.
  • Change the FEP film
    Check if your FEP film is still in a good state, a roughened up FEP film will add adhesion to itself which will make it harder to stick to the previous layer as the build plate goes up. To change the FEP film, check the maintenance part of this course.
  • Use PTFE lubricant on the FEP film
    Another way to reduce the adhesion between the FEP film and the print is to add a thin layer of PTFE lubricant on top of it before pouring in the resin. This is usually not needed and you also need to be careful not to add too much as it risks mixing with the resin. 
  • Change the orientation of the model
    As one of the reasons the layers could be detaching themselves is the huge surface that’s in contact with the FEP film, the orientation can definitely help with this. Make sure to go back to the courses for a more in-depth explanation.

Print is brittle

Picture by Lévi Ponsard

Brittle print can manifest itself with small parts of your print breaking apart very easily. It’s often due to over-curing your print which will start to damage the resin. The resin itself can also be the cause if it’s out of date or of bad quality.

  • Lower the curing time in post treatment
    The smaller the features on your print, the lower the curing time should be. Small and thin parts will cure faster and then become brittle much faster. You can remove one or two minutes of curing time if this is the case.
  • Lower the curing time in the printing process
    If you’ve lowered the post treatment curing time a lot and the prints are still very brittle, it’s also possible the over-curing happens during the printing process itself. Make sure you check the layer cure time for your specific printer and that specific resin as those can vary.
  • Switch the resin
    The resin could be the culprit for a brittle print too. Always make sure it’s not out of date. However, even if it’s not out of date, it’s possible it has been contaminated due to improper handling or is simply a bad quality resin. 

Outer surface has ripples or shifting layers

Picture by Lévi Ponsard

The outer surface ripples are visible on smooth surfaces that start to have ripples or layer shifts. This is due to the build platform not being perfectly straight during the whole printing process or the print itself is moving.

  • Fix or replace the Z-screw
    The Z-screw, if broken or not set properly, can wobble around during the print. This will move the build platform around and create ripples on the surface of your print at best and damage your printer at worse. You should check for your specific printer on how to fix and change it.
  • Add enough of a support structure
    If your model isn’t supported well enough, it can start to move during the printing process as the resin is still somewhat soft, this will also create wobbles or layer shifts on the final result. 
  • Make sure the build platform is not loose
    As you need to loosen the build platform when you do its calibration, it’s possible to forget or to simply not tighten it up enough back afterward which can also create wobbles during the printing process. 

Warping

Picture by Lévi Ponsard

While this problem happens a lot more with FDM printing, it can also occur with resin printing. 

  • Calibrate your build platform
    An improper calibration of the build platform can easily result in what could look like warping. Especially if you’ve noticed that the warping happens on a specific side of the build platform in different prints. This usually means the build platform is not levelled, which causes one side to not adhere to the solid resin as well.
  • Change the initial layers settings
    If the first few layers don’t adhere as well, it’s a lot more likely the print will be able to warp. You can increase the time as well as the number of initial layers.
  • Change the raft settings
    As said while talking about the raft settings, these can also cause warping if the surface area is too big. The bigger the surface area, the more the plastic will shrink and the bigger the warping will be. If you’re printing several pieces, it might be a better idea to move them apart enough so the rafts aren’t merged into one huge one. 

Z-Axis noise

Picture by Lévi Ponsard

If your printer starts making screeching sounds while the build platform is going up and down, it’s probably in need of some lubrication.

  • Lubricate the Z-screw
    Lubricating the Z-screw should make the build platform slide up and down much smoother and silent. You can check the maintenance part of this course for an in-depth explanation of the process.
  • Fix or replace the Z-screw
    The Z-screw, if broken or not set properly, can also be the cause for noise as the build platform goes up and down. You should check for your specific printer on how to fix and change it.

Maintenance

In this part you’ll learn how to maintain your resin printer to keep it running safely and properly for a long time.

Picture by Lévi Ponsard

The first thing you should know is how to properly remove the resin from the tub. While you can leave the resin in the tub if you want to print again soon, it is definitely not advisable to leave the resin in the tub for several days. You might also want to remove the resin from the vat if you simply want to switch to a different resin or if you need to remove a failed print stuck at the bottom. Before we do anything, let’s first gather all the equipment we’ll need. These are the same things that were needed for the post-treatment. Make sure you have the nitrile gloves, protection goggles, cleaning paper, silicone mat and the IPA. But we’ll also need two more things, a funnel, a filter, and a plastic spatula. Make sure the filters have holes of around 150 to 200 microns. This will ensure no waste or cured resin gets back inside the resin bottle. There are also paper filters, but they have to be disposed of after use. For long-term use, it is therefore better to get metal sieves that can be cleaned. Once all the equipment you need has been gathered, let’s start the process.

You can first place the funnel and filter on the open bottle. That way you’ll be able to go directly from the printer to the bottle with the vat.

Picture by Lévi Ponsard

Unscrew the vat from the printer.

Picture by Lévi Ponsard

You can now remove the vat and start pouring the resin through the filter and into the bottle using the spout of the vat. This process should be done slowly, as the filter does not allow the resin to flow quickly, so it is very easy for the filter to overflow and leak resin everywhere. You should always make sure you’re doing all of this on a surface that can be cleaned easily like the silicone mat.

Picture by Lévi Ponsard

To get the last bits of resin inside the vat, you can use the plastic spatula to guide toward the spout of the vat so you can pour it in the bottle too.

Picture by Lévi Ponsard

If a print has failed, you’ll most likely have some cured resin stuck at the bottom of your vat.

Picture by Lévi Ponsard

Removing those is not too hard but it’s very important to use the right tool and be very gentle as it can be very easy to damage the FEP film. The more gentle you are in these operations, the longer you’ll be able to keep your FEP alive before having to change it. I’ll be using the same plastic spatula that I was using earlier. As you can see it has round corners and no sharp edges to make it much harder to scratch the FEP film

Picture by Lévi Ponsard

To remove the failed print from the vat, you can simply try to scrap it off with the plastic spatula. However, if it doesn’t come off easily, don’t put too much force into it as you’ll easily damage the FEP film that way.

Picture by Lévi Ponsard

If it doesn’t come off easily, you can use another trick to help yourself. If you take the vat with one of your hands, you’ll be able to place one of your fingers under the FEP film where the failed print is. If you slightly push from under it, you should be able to slightly detach it, making it very easy to then scrape it off with the plastic spatula without damaging the FEP film.

Picture by Lévi Ponsard

After removal, you can dispose of the faulty print.

Cleaning properly is of the utmost importance when working with resin printers. If you don’t take care of it every time, your work station will get messy very fast and the printer will also suffer from it. I won’t go over cleaning the equipment and workplace but you should be doing it at the end every time too. If you’ve removed the resin from the vat you’ll also want to clean it. Do not place it back inside the printer until it has been cleaned properly.

Once most of the resin that could be saved has been removed, you’ll want to use paper to sponge out the rest of the resin that’s still stuck on the FEP film. Be very gentle every time you’re around the FEP film.

Picture by Lévi Ponsard

Once most of it is removed, you can pour some IPA into the vat and then use cleaning paper again to finish the cleaning.

Picture by Lévi Ponsard

You can also pour a little bit of IPA onto the paper itself to clean the edges of the vat as well as the underside of the FEP film.

Picture by Lévi Ponsard

You can either let it air dry or use a dry cleaning paper to remove the rest of the IPA. Then place it back in the printer. If you didn’t need to remove the resin from the vat and just want to do another print directly after a successful one, the only thing you’ll need to clean up is the build plate. Not cleaning the build plate properly and restarting a print makes it a lot more likely that the print won’t stick on the build plate and fail. If it’s not done already, you can remove the build plate by unscrewing it from the printer.

Picture by Lévi Ponsard

Then place it on the silicone mat. You can clean most of the resin with cleaning paper.

Picture by Lévi Ponsard

When most of it is gone, you can pour a little bit of IPA onto some paper and scrub it onto the build plate. You should take special care of the bottom of the build plate itself as you want it to be as clean as possible. Once that’s done, you can either let it air dry or use the dry side of the paper to remove any IPA left on the build platform.

Picture by Lévi Ponsard

The build platform can now be screwed back onto the printer and is ready for the next print. The last part that’ll need some cleaning will be the screen of the printer. This part should never be in direct contact with the resin but it’s not impossible that I’ll be. I have talked about how careful you should be with the FEP film to not scratch it, this applies even more with the printer’s screen as it usually can’t be replaced at all. In which case, you’ll have to buy a new printer. To access the screen, you’ll first need to remove the vat.

Picture by Lévi Ponsard

You’ll need a non-abrasive cloth for this operation. Pour a little bit of IPA onto the cloth itself, never pour it directly on the screen. You can then wipe the screen. You should be going straight from the same direction from one end to the next. Use a dry part of the cloth and do the same motion to remove any leftover IPA.

Picture by Lévi Ponsard

Cleaning, while very important, isn’t the only maintenance step that needs to be done to a resin printer. As mentioned a couple of times before, the FEP film at the bottom of the vat will degrade over time. Very small scratches might not have too much of an impact on your prints but more serious ones will definitely do. I encourage you to check how to perform this procedure for your specific printer, as there might be some small differences, but most of it will be very similar. To change the FEP film, we’ll first need to remove the vat from the printer and turn it upside down to get access to the screw.

Picture by Lévi Ponsard

You’ll need an Allen key of the right size to remove these screws to separate the frames holding the FEP film from the rest of the vat. Since we’ll only have full access to the frames while changing the FEP film, you should clean them with alcohol before proceeding. You can also clean the slot on the vat itself.

Picture by Lévi Ponsard

Once everything is clean we can place our new FEP film in-between the two frames. We’ll also need to add an extra bulge in the middle so we’ll put a bottle cap under here. Make sure you check your particular printer to know what size of an object you have to put here or if you need to do it at all.

Picture by Lévi Ponsard

The reason we need to add that bulge is because the vat has a small edge that will tension the FEP film as well. If you do not add this bulge now, it won’t be possible to insert the FEP film back onto the vat. You’ll need to hold onto the frame to make sure you keep the bulge while doing the next operations.

Picture by Lévi Ponsard

Puncture one of the corner holes with a sharp object then screw it back. Repeat for the opposite corners then the other two corners and then finally, for all the side holes.

Picture by Lévi Ponsard

Once every screw has been placed, make sure they’re tightened up. You can then place the frame over the vat. Puncture every holes.

Picture by Lévi Ponsard

You can now place the screws. Don’t fully tighten up one screw at a time. You should only do a few turns and then do the same on every screw to lower the FEP film evenly and make sure there’s no crease that forms as the FEP film fully tightens up.

Picture by Lévi Ponsard

Once done you can finally place the vat back into the printer.

The only moving part of a resin printer is the build platform on the Z-screw. This screw needs to be lubricated every now and then to assure a smooth movement. You’ll usually be able to tell that the printer is making much louder noise than usual when it’s starting to need to be lubricated again. There’s a couple of greases or lubricants you can use for this; Teflon dry lubricant, white lithium grease, graphite dry lubricant, and silicone lubricant. Most should give you a decent result. I’ll be using a Teflon dry lubricant for this demonstration.

We’ll first need to lower the build platform to get access to the full length of the Z-screw. We can use the home button to do so.

Picture by Lévi Ponsard

We’ll now apply the lubricant along the whole Z-screw. Once a decent amount has been put on the whole screw, you should move the build platform back to the top and then down again a few times to evenly distribute the lubricant all along the screw.

Picture by Lévi Ponsard

Your build platform should now be much quieter as it’s moving up and down.

Picture by Lévi Ponsard

Summary

Summary

In this content unit we looked at what a 3D SLA printer is, what to use it for, how to operate it in a safe manner, how to post process the pieces that come out of the machine, how to troubleshoot issues on the print, and how to maintain the printer.

In the first part, the basics of how a SLA printer works were shown by curing liquid resin inside a vat while a build platform moved up to let the next layers get cured. Different types of SLA printers like Laser-SLA, M-SLA and DLP were also presented. As well as the applications of SLA printing like prototyping, dental, jewellery, etc.

In the second part, the safety measures to follow when working with SLA printers were explained. It was shown that you need to keep your hands and eyes safe from the resin and know about the toxic fumes. 

In the third part, slicers were presented and explained. How to take a 3D object and import it into the slicer software to prepare it to be printed was displayed. As well as resizing, positioning, creating supports, changing the printing settings and more.

It was then shown how to slice models and verify the printing process before exporting the printing file.

In the fourth part, how to prepare the printer was taught by levelling the bed, adding the resin, starting the print and supervising it.

In the fifth part, it was shown how to remove the print, clean it, and finish the curing process. It was then presented how to smooth out and add extra coating to finish the print.

In the sixth, spotting printing errors and how to avoid or fix them as well as issues on the printer itself were explained.

In the sixth and last part, it was explained how to maintain a SLA printer like removing the resin but also cleaning the vat, the build platform, and the screen. As well as changing the FEP film and lubricating the Z-screw.

Quizz