A few weeks ago I printed out some parts for an ROV I’m building. Two parts, joined together, form a ring about 200mm in diameter, to which an acrylic dome is attached. When I tested this after printing everything was fine, but today when I had time to return to this project, I found that the Durable print has shrunk sufficiently so the acrylic is no longer the correct size. Is this expected? Can it be avoided or should I switch back to using Tough?
Most of our materials will hold tolerances of approximately 100 microns over 90% of the print. After being soaked in IPA, resins will swell slightly but it’s often by a fraction of a percent and doesn’t exceed 1% even if the part is left overnight (I’ve done this a few times…). Parts return to their original dimensions after a few hours when the IPA has evaporated off.
Parts that haven’t been UV cured are in a green state and can be susceptible to warping. This would be my best guess as to what you’re seeing. After parts have been fully post-cured they shouldn’t change further. Making sure parts are fully supported and orienting at an angle are the best ways to cut down on warping.
Thanks for the reply; a few comments:
The part is now 3% smaller than it was about 2 weeks ago. The part was originally printed just over a month ago, washed and cleaned with IPA and cured for about a day (forget the exact number of hours). After, the part appeared to be just fine - not sticky or anything unusual - and the expected size. I’d been happily working with it for a while but had put the project aside for the last two weeks and was very surprised to come back to it and find the shrinkage.
For comparison, an older version of this part was made in Tough and has sat next to the Durable part in my office. Checking this part today, it’s exactly the correct size as you’d expect - no shrinkage.
So - I don’t think the part was in a green state and it hasn’t warped - just shrunk. Even the bolt holes appear to be smaller than they use to be (ie. the bolts no longer fit). As for support - I was supported well and printed fine. While it sat in my office, its sits in a fully supported foam container.
Any other ideas? I can switch back to using Tough which doesn’t have this problem, but that’s not ideal. I’d rather not throw another half tank of Durable at this without definite steps I can change.
This doesn’t sound like typical behavior. After post-curing the properties of parts should be stable. Can you open a ticket with our support team so that we can look into this for you? It also helps us to track issues like this internally and get a sense for how prevalent they might be.
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