Preform doesn't reduce raft size for hollow part (was working on older versions)

Hey there,
So recently I started to print parts that are hollow in the center, and preform doesn’t reduces the raft size like it used to in older versions.

Consequently, the printer fails the peeling operation and i can’t print this file as-is. I had two consecutive failures with the printer reporting motor jammed error somewhere between the layers 10 and 15.

In some late 2017 version of PreForm this issue had been solved and I could print such parts with the base only where needed.

Now I did update to the Jan. 29 version of the Firmware and PreForm, recreated the supports from scratch, set base thickness to 1.5mm, re-uploaded the file and this time (3rd attempt) it seems to be working since were at layer 25 and so far so good. I don’t know if it’s the new version or the 1.5mm height.

The questions to Formlabs would be :slight_smile:

  1. Are the Jan 29 updates expected to solve this kind of issues
  2. Can we expect to see the base generation get back to the way it was a few months ago ?


No, nothing has changed in PreForm in this area. But it is very sensitive to the spacing of supports, so you might see it hollow the middle out somewhat randomly. I talked about this a bit in this post, and showed how to get a bit of control over it.

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Thanks for the swift answer !

OK so PreForm isn’t able to remove the center if the raft forms a loop… makes sense as it would create succion, I didn’t think of that before. That’s indeed a good workaround to know about.

Regarding the peeling failures is there something I should do ? I normally print this type of part standing up to pack more of them but this time I needed one asap which is why I tried to limit the amount of layers… However, isn’t the printer supposed to be able to handle bases as large as this one ?

Another thing you might want to try, if you can’t create a ”channel” to the inside by removing supports, like mgarrity suggested, is make the raft thinner.

Much thinner.
From my testing, 1.25mm is perfectly fine for 90% of the prints.

1.25mm is 13 layers, so that might just do to get your print beyond the point where you get a jam.

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And we expect a change from this point in the program.

The channel trick should work for you, but the printer shouldn’t have a problem with a base this big anyways. It’d be good to figure out why it jammed. You could send the details to support, they might be able to figure out what’s going on. What material was this? It looks like maybe tough? And a regular tank?

Yup it’s a regular tank (fairly clouded, about 1.5l of resin have been printed, details and surfaces are still fine) and Tough V4. Settings in preform for the raft are default except for the 3rd print for which the base thickness was set at 1.5mm and part height to 3.5.

I will open a ticket tomorrow

It jammed because the changed peel strategy (of the past year) is too damn violent, is what i keep saying, but no one believes me.

I had it rip supports off old V2 tough (which is relatively soft in green state, and even softer when it’s expired). Yes, it’s an extreme case, and i’m not saying old expired resin should be a supported use case, but that’s not the point - the point is, it proves the forces are higher than before.

Mgarrity, is there a way to reduce the in window menu boxes when working on a lap top, they take up entirely too much of the workspace; older versions of Pre-Form occasionally glitched and allowed for much smaller boxes, but not the newer versions. Any suggestions outside of altering the settings of the lap top itself?!

I’m afraid I’m more of a geometric algorithms person than a windows ui person. You should probably start a new top-level thread on that subject. There are probably folks on the forum who have some tricks for this.

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