In the previous blog post, we started the topic of resin shrinkage. We showed how serious it is and we presented a simple yet effective method of measuring the shrinkage amount and compensating for it.

However, the problem is more complex than the two numbers. Anyone who has ever worked with plastic injection molding can confirm this. There is a number of papers, models, and algorithms that deal with modeling shrinkage of plastics after molding. The same, unfortunately, applies to 3D printing as our material shrinks as it cures. What effects does it have? Is there something we can do about it? Yes, there is as we see at the end of the post!

Just to illustrate what we are trying to fight, there are a couple of posts from a single FB resin printing group:

Continue reading “Preventing Warping of Resin Printed Pieces: Alternative Way of Fighting Resin Shrinkage” →

Most polymers shrink when they cure or solidify. That means that their volume shrinks down during the process. The simple consequence is that the models you print either on FDM or resin printer are smaller than you designed. Therefore, when you try to print, e.g., an enclosure for PCB or a hole for a pin or a screw, they might not fit.

Today, we will explore how serious the shrinkage is, whether it is the only source of dimensional inaccuracy and how to measure it and compensate. After reading this post, you should be able to calibrate your resin printing process such that the models you print will come out perfectly within the accuracy of a single LCD pixel. That is usually roughly 50 µm + the inaccuracies in your measurement setup. We will also show you that you can easily use this test to precisely tell if you overexpose your model or not.

However, since we print quite complex geometry layer-by-layer there are some interesting phenomenons that need to be taken into account. They affect how the printed part wraps. They are complex, so we will dedicate a separate blog post on this topic in the future; today we will start with the basics.

Continue reading “Getting Perfectly Crisp and Dimensionally Accurate 3D Prints on a Resin Printer: Fighting Resin Shrinkage and Exposure Bleeding” →

In this regularly updated post, I sum up the results of torturing various resins for SLA 3D printing. I have a very fine and functional mechanical model – a 1:85 compound planetary gearbox. The gearbox uses M0.5 teeth (half the LEGO gears teeth size). It is intended to be used with a brushless motor. The overall diameter of the gearbox is 38 mm. Here’s what it looks like:

Continue reading “Overview of Practical Resin Properties” →

When you scroll through the various Facebook group about resin printing, you see quite often questions about the following topics:

• “my prints are not sticking to the build plate”
• “my layers separate”
• “my prints have a rough surface”
• “I have a large elephant foot/squished bottom layers”

In the first two cases, people often advise “increase your bottom layers!” and “increase your bottom exposure”, “lube FEP”, “sand your build plate!”.

But I think such advice is wrong and the best advice for all four cases should be “Introduce a light-off time”. Why? Let me walk you through a series of experiments and observations. It will be a long read, but bear with me – it is an actually simple puzzle just with multiple factors. And as we will see at the end, the same advice also applies to solving the rough surface case and also (partially) the elephant foot. We will also learn, that printing at layers thinner than 50 µm does not make much sense and it can actually degrade the print quality and precision.

Note that I have previously touched on this topic in my blog post Improving surface finish of hollowed SLA 3D prints: one aspect of blooming.

Continue reading “Prints not sticking to the build plate, layer separation, rough surface, elephant foot: resin viscosity – the common denominator” →

Today, I want to talk about an interesting phenomenon I noticed when printing hollow objects. A simple procedure can drastically improve the surface finish of your prints:

Continue reading “Improving surface finish of hollowed SLA 3D prints: one aspect of blooming.” →

Recently, I discovered Resione resins. They have a wide variety of resins. They also have a series of tough and flexible resins. They also have an EU distribution center, so the resin arrives quickly and you don’t have to care about customs. Overall, the resins seemed nice. I might make a separate blog post about their resins in the future.

When I was working on a big project (blogpost upcoming, sneak-peaks on my Twitter and Instagram) I decided to use Resione M68 — tough snow-white resin. The parts I printed were thin-wall parts (wall thickness of 0.5–1 mm). They also have a lot of internal cavities where a liquid can be trapped. After printing, the pieces looked great! However, it was a rainy day and the air humidity increased up to 80 %. The next day I found my parts deformed like this:

It seems that the Resione M68 absorbs a lot of moisture and the large flat areas between infill of the component expand, thus they form bumps. So I took one piece and soaked it into the water for 20 hours and it even cracked.

It is a well-known phenomenon, that some plastics absorb moisture. There is even an ISO standard 15512:2019 for measuring this (which I don’t have access to, unfortunately). Since my components will be exposed to the weather condition, I decided to make an experiment to determine which resins would be suitable and which not.

Continue reading “I tested how much moisture SLA printers resins absorb. How it changes them?” →