There are several old posts here from myself and others complaining about how Elastic and Flexible prints always seemed oversized and very inaccurate. This was plaguing me on some more recent jobs and I finally decided to do some testing and am happy to share the results. For example this gasket below was washed and cured under normal conditions but still came out as 52mm instead of 50mm. No surprise that this did not fit into its mating groove.
The TLDR is that this is heavily correlated to DRYING TIME of your parts after an IPA wash. Following the Formlabs wash time specs do not reduce inaccuracies in any way, it’s the drying time that matters.
You can see in the graph below how heavily this impacts dimensional accuracy. We now put printed parts into a food dehydrator or filament dryer after washing to speed up and ensure full evaporation of IPA and good accuracy. I hope this helps out others - the full blog post on our website is below.
In my very limited testing I came to the same conclusion. I usually dry out my elastic and flexible parts in my home-made curing oven at around 60°C for about 30 mins or so before turning on the UV. I then follow it up with an underwater UV cure. I haven’t been as scientific as you’ve been but I’ve seen similar results.
EDIT:
I also ensure there’s minimum contact time between the IPA and the parts to minimise the initial absorption.
I realized that my first elastic 50A resin print came out big. The part, which was 30 mm, came out with a measurement of 32 mm. In the information I read in some forums, I got information that the part should not be kept in IPA for too long, that the part grows by absorbing the IPA. But I could not find the exact solution. After the part comes out, I will leave it for 1 day after the IPA solvent and cure it, I hope I will be successful in measuring.
