this post was submitted on 03 Dec 2024
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[Resin Printing] Any tests for finding the minimum lift height? (self.3dprinting)
submitted 2 days ago by papalonian to c/3dprinting
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Something I've noticed when watching my resin printer work is that a lot of time is spent every later lifting the plate well after I hear the model unstick from the FEP.

It's not a huge deal on smaller prints, especially ones that can be printed with "vroom" settings, but on larger models that are being printed at 1-2mm/s lift speed, several hours are spent just waving the model in the air for no reason...

I had the idea of making a test model that is essentially an intentional suction cup in the center of the plate (where FEP stretch is most prominent and required lift distance should be highest). I would print this model multiple times, with slightly lower lift heights each iteration, until it fails to release from the FEP. I'd add a safety margin and set my raise height to that...

Does anyone see any fault in my logic, or know of a better method of achieving what I'm after?

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[–] Fribbtastic 1 points 1 day ago (1 children)

I can think of two problems:

First, not every Release Film is the same. You are talking specifically of FEP which is mostly used to describe the Release film and was commonly used for that but is the material that the Release film is made from. There are different types like the already mentioned FEP but also nFEP, PFA, ACF and probably others as well. Each of those materials has a different rigidity which would mean that they peel away from the Model sooner or later. According to this, FEP is much more flexible than PFA or ACF.

Second, the durability of the Release Film. Over time, the Release film will wear out and need to be replaced. They could become more flexible the more you use them. Cutting it too close could mean that your models will fail from one print to another.

Some other thoughts:

  • How much the Release film flexes could also depend on the surface area being printed. More surface area could mean that the layer is sticking to the release film longer
  • The same would apply to the Exposure rate because higher exposure rates make your layers stick more, including to your Release film
  • Assembly also plays a role in this. Since you need to replace the Release film at some point, you could add more or less "slack" on the film which would throw off your previous test massively.

While I like the idea, I think it would signal a false sense of confidence in your printer because if you "dial in" your lift distance and the model then fails, people could start looking in the completely wrong direction to fix a problem. I mean, with that many variables to consider, people still download the validation matrix without adjusting their bottom and transition layers based on the description and then ask why their exposure test doesn't work.

[–] papalonian 1 points 1 day ago

All very good points. I think if I want to continue entertaining this idea I need to adjust my sights to a more general number than anything exact. Another user pointed out that time spent testing vs time saved would be a pretty close cut. I might devise a test to find a general minimum, increase it by a fair margin, and call it close enough.