Preventing Warping of Resin Printed Pieces: Alternative Way of Fighting Resin Shrinkage

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:

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Getting Perfectly Crisp and Dimensionally Accurate 3D Prints on a Resin Printer: Fighting Resin Shrinkage and Exposure Bleeding

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.

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On the Topic of Disposing Dirty IPA Washing Bath From Resin Printing

Resin printing is wonderful. I love it – it’s fast and detailed compared to FDM printing. Also, the materials are getting better and better. However, compared to FDM printing is a really messy process. The resin frequently drops where you don’t want it to, and you have to wash the models in an IPA bath.

And here comes the problem ­– how should you safely dispose of a dirty IPA bath? The resin before it is cured is toxic, especially to aquatic life. The best way is to probably bring the bath to a facility for hazardous waste disposal. Nevertheless, the idea of recycling IPA is appealing so you see a lot of people on YouTube and Facebook trying to clean it and recycle it.

Here I bring my 2 cents on the topic. Note that what I present here is more of an idea or a proof-of-concept rather than a complete solution. Also, I am no chemist, so I cannot guarantee that the presented procedure actually yields safe waste. If you have some insight or ideas, please, let me know in the comments!

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Testing UV Resins by QTS: Really Interesting and Unique Properties

A while ago I was approached by (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.

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JLCParts Rising From The Ashes

About 2 years ago I started a small and dirty project – a new catalog for the search engine for the components that JLC PCB provides for their assembly service. The motivation was really personal — I liked the dirt-cheap assembly service, but finding the suitable components for my projects was really painful. So I created JLCParts – a browser-only alternative component catalog that doesn’t need any sophisticated backed. It is just served as a static page.

However, on March 7 2022 I was forced to shut down the service. As of today, March 21 2022 it is back operational and working again. What happened? Who to blame? TLDR: Blame no one; the whole shutdown thing is just a misfortunate result of miscommunication and my service operating in a pretty dark grey area of what is legal. There was no bad faith from JLC PCB nor LCSC, just poor communication. Details below.

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Testing Siraya Tech Fast Mecha: A (r)evolution In Functional 3D-printing?

There are many resin printing materials out there marketed as “engineering”, “for functional parts”, “heavy-duty”. Since I got into the resin printing world, I tried a large number of them. However, none of them in my opinion didn’t deliver what was promised. The main challenges are not only low strength but also low impact resistance and most notably insufficient surface properties. Most of the 3D-printing resins out there are easy to scratch and when two surfaces mate, they have relatively high friction, and, most notably, they grind each other and form a white powder.

I was given the opportunity to test a new material – Siraya Tech Fast Mecha that claims to be suitable for articulated functional parts. The marketing is that the material doesn’t grind when two surfaces interact. Is it true? We will find out in this hands-on review. For clarity; I was given a sample of Siraya Tech Fast Mecha for free before it was available to the general public. I wasn’t paid in any other way for this review and all opinions are mine.

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Overview of Practical Resin 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:

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A Step-by-step Guide for the Perfect Bed Adhesion and Removing Elephant Foot on a Resin 3D Printer

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.

I will show you how to get perfect results every time.
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What Screws Does Elegoo Saturn Use?

There is a common question regarding damaged and lost screws on the resin tank on Elegoo Saturn. I have answered several questions for this on the Facebook groups, but those are not indexed by Google so you are out of luck when Googling. This is why I publish this really short blog post – so people can actually Google up the screws used on the Elegoo Saturn resin tank.

There are three screws:

  • M3x5 with countersunk head,
  • M4x10 with countersunk head, and
  • M4x10 with cylindrical head.
  • The vat is attached via M4x40 screws with overmolded cylindrical head.

This is it. I hope the search engines will pick this up well.

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

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”
An example of all the problems shared in the FB groups. It is really not hard to find them.

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.

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