Min layer time

So, I finally found the min layer time setting in Slic3r under cooling, which I guess is where it belongs, but since I don't have a part fan (mostly ABS printing these days) didn't see it before.

Anyway, the question is that the option here seems to be to slow down the extrusion if the layer will take less than the specified time. But wouldn't we *not* want to slow down in order to not overheat the small features?

I would think a good behavior here would be to retract at the end of the layer to reduce ooze, then move a bit off the print and wait for some time. Is this feature hidden some where of does anyone know of a workaround besides printing a sacrificial object?

I've been saying the same thing for some time. You have several options. The easiest is to simply drop more than one part onto the plater so that it prints two or more at a time and has to move the extruder to-and-fro between parts. Ok for small and quick prints, not a solution for larger prints. In the case of larger prints I create an ad-hoc sacrificial column that is as tall as the top of the print, and drop that onto the plater alongside the part. Moving the parts apart and/or slowing the non-printing move speed will increase the cooling time.

As an alternative you could set up an "after layer change G-code" or "Before layer change" G-code to perform a delay away from the print.

e.g.
G91 ; set relative positioning
G1 X20 F7200 ; Move rapidly away 2cm to get hot nozzle away from print
G4 P5000 ; Pause 5 seconds
G1 X-20 F7200 ; Rapid move back to original location
G90 ; Set absolute positioning

Choose the move directions & distance so as not to go outside the print area.
If you only want this to be done above a certain layer, you could cut & paste the code into the G-code file between each layer change above that height. If your printer does not implement the delay command (G4), you could perform a slow move (or series of slow moves) instead.

Dave

Yes, I do frequently use the sacrificial tower approach and the print two approach, as I alluded in the OP.

I'm wondering about the Slic3r feature which is already there to address short time layers this seems to be doing something non-intuitive.

I suppose just slowing down would help if your top feature were, say a thin raised lip around the perimeter of an object.

But I think the more common error is the "pointy thing at the top" type of problem, for which it seems there could be an in-build solution.

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braddo99
Yes, I do frequently use the sacrificial tower approach and the print two approach, as I alluded in the OP.

I'm wondering about the Slic3r feature which is already there to address short time layers this seems to be doing something non-intuitive.

I suppose just slowing down would help if your top feature were, say a thin raised lip around the perimeter of an object.

But I think the more common error is the "pointy thing at the top" type of problem, for which it seems there could be an in-build solution.

I would certainly welcome an inbuilt solution, but none of the slicing applications I have seen do anything except slow down the print - which as you say is only of help if the perimeter is reasonably large, so for the present we have to use one of the workarounds. I shouldn't think it would be a particularly difficult thing to add.

Dave

I agree - we need a "print 1 layer, move to the side and pause for a few seconds before starting the next layer" function.

Seems Matterslice has this option but it doesn't appear to do a retraction so filament oozes all over while the extruder is hanging out.

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braddo99
Seems Matterslice has this option but it doesn't appear to do a retraction so filament oozes all over while the extruder is hanging out.

Forget the mess this makes. This means you're losing track of plastic. So even if you sat there and tweezed off the plastic as it oozed, the final print quality will suffer.

Yes but if there was a good retraction that could be significantly reduced if not eliminated.