Minimum print time per layer? Has anyone actually gotten Slic3r to slow down when the layer prints quickly?
I’m seeing settings for “Slow down if layer print time is below” but it doesn’t seem to have any effect. I’ve got it set to 30 seconds, and on tall, narrow objects, the print speed can be 5 or 10 seconds, which doesn’t give the PLA time to cool. I see “Min print speed” but I’ve bumped that all the way up to 60 and it doesn’t seem to be making a difference.
In any case, slowing down the print speed doesn’t really help because the hot end is still on contact with the part. That keeps the PLA hot, and leads to all sorts of problems as layers are added without prior layers hardening.
What is really needed is a “stop and sit off the part so each layer has a chance to cool” setting. I saw a big improvement in printing by adding gcode to re-home X and Y between each layer, primarily because it was giving the PLA time to cool.
But moving off part and stopping (either for a time or to re-home) introduces a second problem, which is that the hot end drools. So I tried to increase retraction. I’m up to 1.5mm and it still drools if I re-home. Leaves little blobs on the outside of the part as the hot end returns to print the next layer. It seems like there needs to be a “keep_retracting” setting that re-triggers retraction every x seconds when sitting… Of course, that would eventually release the filament… :sigh: this fine tuning is tough…
seems like “min print speed” should be MUCH lower, like, 1-5???
If your MINIMUM is 60, then the printer will NOT slow down below 60 - so it will print small layers at 60mm/s which will mean there will be no “slow down”… you want those layers to be done at (say) 5mm/s - so you need the minimum to be at MOST 5mm/s…
Suggest 2 things:
-
Get a big fan… a HUGE fan… or a colder flow of air directed on the part… More cooling (up to a point) can never hurt… I have a carriage mounted fan and a 120mm frame mounted fan for almost all PLA work…
-
Add a tall 10 or 20 diameter hollow cylinder to your print, off to one side… the printer will have to travel to it, print it and then come back to your original object, allowing it more time to cool…
Skeinforge had/has some sort of ‘dwell’ or ‘hover’ function (can’t remember the exact name of it) but as you say, it has the drooling problem and in my experience it created problems without solving any…
@Jarred_Baines is right about the min speed, you have to make that slower to get the print to slow down.
Also, printing multiple copies of an object at once can help a lot with cooling, by giving the nozzle somewhere to go to stop heating up the part you’re trying to cool. Even if it is printing slowly, it’s hard for it to cool when the plastic is constantly in contact with the hot nozzle.
Yup… I printed 2 “reprappro fan mounts” because there are 2 tiny pins that stick up on them… I’d call it “impossible to print by itself”…
Spaced them apart, one at one end of the build plate, one at the other end… that too gives it an extra second or two to cool (which makes a difference with a lot of cooling going on as well 
) but getting the nozzle away is mandatory…
I did exactly this, moving the nozzle off print, then retract, then wait, then prime the nozzle. I set it in slic3r settings between layer changes.
I think that if you retract enough, you won’t have the ooze problem. But its possible it can lead to jams.