parts overlapping the initial outside border generated

I'm new to slic3r and 3d printing in general, so I dont know all the right terminology so please bear with me.

When I add stl files to slic3r, sometimes the initial outside pass that slic3r does around all objects (Is this the "skirt?") will intersect with a part or more. Its as if the outer area does not account for parts accurately.

When the outside line is printed and then a part is attempted to print in the same area, either the part's height becomes uneven because of the existing layer where it is trying to print or subsequent passes end up pulling the part off of the bed due to uneven heights.

Attached is a picture of the generated pathing with the problematic outside pass that intersects with actual objects.

Is there a way to manually define the outside pass' pathing or at least keep it away from parts? And is it possible to disable this entirely, or would that be a bad idea?

Outside path intersecting with parts

You can disable the skirt in "Print Settings"/"Skirt and Brim" by setting the number of loops to zero. If you do that you will probably need to extrude a bit of plastic in your start code after all temperatures have been reached immediately before printing to get it flowing. As regards the issue, check that the objects to be printed are definitely all within the bed area as defined in Slic3r's printer settings. You could try experimenting by changing the skirt's "distance from object" in case it is a bug that occurs only at specific distances.

Dave

I've been fighting with the skirt being in a separate layer (higher by 1xlayer height) than the actual surface where I would like the print to start, basically I'm printing the skirt exactly where I would want on the bed at the proper height, but anything after (being raft or object itself) is one layer too high. What am I missing other than editing the Gcode and deleting the first "go up one layer in Z"?

Bob, I once had that, and in my case it was caused in the "support material" menu by having "generate support material" unchecked, but "Raft layers" set to 1 instead of 0. Other causes can be an STL that has a small bit (too small to print) hanging below the main base, so that bit is taken as being the bed height and the rest is above it. You could try double-clicking the part in plater and perform a Z cut at 1 layer height, or import the STL into OpenScad or another tool and cut the base flat.

Removing the first Z move in the G code would not help you, because the rest of the moves will also be a layer too high - i.e. layer 1 would be OK but layer 2 would print at the height of layer 3 etc.

When you want to have a raft, it is possible that having a gap between the raft and the part is intentional, to make removal easier.

Dave

Quote
dmould
Bob, I once had that, and in my case it was caused in the "support material" menu by having "generate support material" unchecked, but "Raft layers" set to 1 instead of 0. Other causes can be an STL that has a small bit (too small to print) hanging below the main base, so that bit is taken as being the bed height and the rest is above it. You could try double-clicking the part in plater and perform a Z cut at 1 layer height, or import the STL into OpenScad or another tool and cut the base flat.

Removing the first Z move in the G code would not help you, because the rest of the moves will also be a layer too high - i.e. layer 1 would be OK but layer 2 would print at the height of layer 3 etc.

When you want to have a raft, it is possible that having a gap between the raft and the part is intentional, to make removal easier.

Dave

Thanks Dave, I've played around those settings and you are right, it seems that some combos are really messing things up. Good thing we can preview the code before starting the print, that feature alone is awesome.

Now the only major issue I got left is when I go 0.2mm or below, the stop/start of filament extrusion and head movement generate gaps and blobs between the stop point and end point of vertical structure.... i.e. if I print a cylinder, I will get a blob where the printhead stops while moving the Y axis upwards, and no material for about 2-3mm where the head starts when reaching the new layer...I'm not printing fast (i.e. 30-45mm), and not using acceleration yet. Once that is taken care of, I'll be able to finally start printing for real.

Quote
boboche
Now the only major issue I got left is when I go 0.2mm or below, the stop/start of filament extrusion and head movement generate gaps and blobs between the stop point and end point of vertical structure.... i.e. if I print a cylinder, I will get a blob where the printhead stops while moving the Y axis upwards, and no material for about 2-3mm where the head starts when reaching the new layer...I'm not printing fast (i.e. 30-45mm), and not using acceleration yet. Once that is taken care of, I'll be able to finally start printing for real.

Do you use a Bowden extruder? Bowden extruders suffer from lag - there is a delay between the time the extruder starts to turn and the time that plastic is actually extruded, and another delay between the time the extruder stops and the time plastic ceases to flow.The slower you print, the less the effect this issue has on the print. Greatly lowering the acceleration may help without slowing the whole print too much, as it will effectively slow down the move only at the start and end of the perimeter - but that could cause the same symptoms to appear at corners. If the main problem for a particular print is at layer changes it may help to not retract at all (uncheck "retract at layer change") so the XY move does not stop for long, or experiment with the speed & distance of the retract. Or try setting the "Seam position" to "random" to try to stagger the place where the effect occurs - though in the version of Slic3r I used the position was still not all that random.

It is possible that the effect could be greatly reduced in the printer's firmware by having the extruder moves lead the XY moves by a short time interval so that the flow of plastic at the nozzle is brought into synch with the XY moves, but I do not have any such firmware to try, and it is not something that is realistically possible to achive in the slicing application (though Simlify3D makes an attempt in its "coast at end" feature).

Dave

Edited 1 time(s). Last edit at 01/19/2015 08:25AM by dmould.

Quote
dmould

Quote
boboche
Now the only major issue I got left is when I go 0.2mm or below, the stop/start of filament extrusion and head movement generate gaps and blobs between the stop point and end point of vertical structure.... i.e. if I print a cylinder, I will get a blob where the printhead stops while moving the Y axis upwards, and no material for about 2-3mm where the head starts when reaching the new layer...I'm not printing fast (i.e. 30-45mm), and not using acceleration yet. Once that is taken care of, I'll be able to finally start printing for real.

Do you use a Bowden extruder? Bowden extruders suffer from lag - there is a delay between the time the extruder starts to turn and the time that plastic is actually extruded, and another delay between the time the extruder stops and the time plastic ceases to flow.The slower you print, the less the effect this issue has on the print. Greatly lowering the acceleration may help without slowing the whole print too much, as it will effectively slow down the move only at the start and end of the perimeter - but that could cause the same symptoms to appear at corners. If the main problem for a particular print is at layer changes it may help to not retract at all (uncheck "retract at layer change") so the XY move does not stop for long, or experiment with the speed & distance of the retract. Or try setting the "Seam position" to "random" to try to stagger the place where the effect occurs - though in the version of Slic3r I used the position was still not all that random.

It is possible that the effect could be greatly reduced in the printer's firmware by having the extruder moves lead the XY moves by a short time interval so that the flow of plastic at the nozzle is brought into synch with the XY moves, but I do not have any such firmware to try, and it is not something that is realistically possible to achive in the slicing application (though Simlify3D makes an attempt in its "coast at end" feature).

Dave

No it's a folgertech Prusa i3 kit using the supplied direct-drive extruder. I had this back on my cupcake 5 years ago and could be compensated with something like "oozing" (bad memory here) but I don't see such settings in slic3r., I see filament retraction parameters vs. movement length but that won't help with the delayed start.