Stopping stringing across open space in an object
Hello all. I've had a Prusa mini for about 2 weeks now and things are going OK even though there have been problems in a few areas. One I'm now having is stringing in open areas. I'm using PrusaSlicer and have retraction off (or else this particular TPU jams in the extruder) and I have "avoid crossing perimeters" shut off. I'm thinking there is a setting I can set so it doesn't ever cross open spaces. The stringing is in the exact places each time. Any help is appreciated.
RE: Stopping stringing across open space in an object
It looks like the filament is taking a shortcut in the curved part when extruding.
Not stringing in traditional sense, when extrusion stops and the ooze from the nozzle drags a string to the next starting point.
If this is the case "avoid crossing perimeter" will not help. I would try lowering the printing speed and see if that helped.
TPU can be tricky to get right.
Have a look at my models on Printables.com 😉
RE: Stopping stringing across open space in an object
@area51
I have all the settings at 20mm/sec. I should have mentioned that. It's slow, but the print comes out very nice other than these shortcut lines, and at 20mm/sec the mini's extruder doesn't jam. I can't tell you how many times I have had to take the extruder apart. It doesn't do well with this 95A flex from Overture. https://www.amazon.com/gp/product/B07VBL6XHH/
I haven't had jams with the 2 other Flex types I've tried but they all have the shortcut lines. I did add in 5mm of retract twice, and that helped the shortcut lines a bit, but the extruder jammed both times.
I do think the slicer needs a "vase" checkbox setting or something like it to never route across over spaces.
RE: Stopping stringing across open space in an object
The avoid crossing perimeters IS the setting that reduces travel across open spaces. It doesn't eliminate it but adds an extra 'cost' to moves that do cross and so reduces them. If you have that turned off then it will travel across like that.
But as area51 says that doesn't look like filament stringing, it looks like non adhering perimeters. Are there sections missing from the perimeters where that filament should go ? If so then its not going to be any of the path planning options needing changing but more getting your extrusion to adhere correctly and that is usually down to speed, temperature/ cooling, overhang issues. Basically other reasons.
RE: Stopping stringing across open space in an object
@tmrent
If you zip and upload the project file (3mf) here on the forum, it would be easier to help.
The Mini doesn't like the softer TPU filaments and many short extrusions often leads to under extrusion and clogs.
The ideal situation is "vase mode" where the filament flow is steady and no retractions that mostly eliminates the effect of bowden tube and the single side drive gear.
When I got my Mini, I tested some different soft TPUs and found that the Mini could print with filaments that had a hardness of 98A or more. Softer filaments would often under extrude or clog the nozzle.
Have a look at my models on Printables.com 😉
RE: Stopping stringing across open space in an object
I have been having a similar issue but mine actually is from stringing. Checking the Avoid Crossing Perimeters box reduces the crossings by more than half. Is there a way to reduce it even more? I would like to not cross the center at all if that is possible. If I can avoid these crossing then clean up will be so much easier.
I am Printing in TPU and I have all of the settings dialed in so it prints amazingly well with the excepting of the stringing in the center.
I do have "retract on layer change" and "wipe while retracting on to reduce the blobs. Turning these on improved the outer surface quality so hopefully, these are not the culprates.
If you know any settings that you think will fix this I am open to trying anything to help me reduce this cleanup.
