If you follow my work, you know that I use my resin 3D printers a lot to produce soft silicone molds or pieces (original blog post and a follow-up). Resin printers can create precise and detailed patterns. You can quickly prototype, cast miniatures, dices, chocolate molds… There are plenty of uses for soft silicone molds. However, some silicones play well with resin-printed patterns, and some don’t. In this post, I will explain to you which silicones cause the trouble, why we care, and also, how to prevent the cure inhibition. The recipe I give you is surprisingly easy and doesn’t require any special equipment. It actually outperforms existing commercial solutions (e.g., Inhibit X) both in terms of price and performance.
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:
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”
A while ago I was approached by Overhanglab.com (QTS) about whether I would be interested in trying out their resins. I usually resist testing resins since, in my experience, most of the smaller companies just blindly copy the original resin formula by Autodesk and they are the same rubbish as Elegoo and Anycubic Standard resins: not particularly strong and very brittle. However, QTS gives some really strong claims about their resins, so I thought – let’s see if they are true or just a marketing talk.
I had the opportunity to test their Model resin, Flex resin, Engineering Strong resin, and Engineering High Temperature. In this post, I will share my experience with all of them except for the high-temperature one. The high-temperature one needs further testing and I have an exciting project with it on my mind which deserves a blog post on its own. Let’s dive in.Continue reading “Testing UV Resins by QTS: Really Interesting and Unique Properties”
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:
In my recent blog post, I showed you that the resin viscosity and printer’s poor construction are the main reasons why people observe print failures. I also highlighted that the same phenomenon causes the elephant foot. However, I did not give you a step-by-step guide on how to work around it. I’ll fix this in this blog post, where I show you how to use UVTools to post-process your sliced files in order to get the perfect bed adhesion and no elephant foot on your prints.Continue reading “A Step-by-step Guide for the Perfect Bed Adhesion and Removing Elephant Foot on a Resin 3D Printer”
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:
Back in high school, I wrote SOČ (student-paper) about designing and building a small horizontal wind turbine (available here, only in Czech). It was an interesting experience and I learned a lot about aerodynamic. Ten years passed and I decided to revisit the idea of having a small DIY wind turbine. However, with a modern spin on it in the form of 3D printing the whole full-scale turbine on an SLA printer. Spoiler: it turned out perfectly!Read more about the desing and manfacturing of the turbine
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?”