Bad extrusion when outlining holes

[JustinDeming]

It seems like I'm experiencing a bug regarding how much filament is extruded when the printer is drawing the outline for a hole.

This has been happening for a while, but I just ignored it, but now I can't get a good print for a part I really need. The problem is any area that should have a circular perimeter printed ends up with not enough filament by a long shot. It looks to me like the G-Code is allowing just enough filament as if the print head was going from one side of the hole to the other, rather than around the hole 3-4 times.

I'll attach my factory file & the most recent attempt. In this print there were supposed to be standoffs to hold up a printed circuit board. All I got was a little knot of filament where those were supposed to be, and you can see where the through holes look terrible.

Printed with black ABS, 100 degree bed, 230 degree print head.

ATMegaCase.factory

Factory File

(943.91 KiB) Downloaded 105 times

[JoeJ]

I looked through the gcode file and I don't see any problems with the toolpaths the software is generating. Maybe this is more of an environmental problem - meaning that maybe the reason those small circles are having trouble printing is because on the first layer, the circles didn't bond well to the build plate. Then for every layer after that, there is nothing good for the plastic to grab onto and it ends up bunching up like that. You might be able to improve the first layer adhesion for those small holes by decreasing the first layer speed to 20%.

What happens if you print one of these cases on top of a raft with a fairly small separation distance (i.e. 0.1mm)? Do the holes look any better?

Either way, for the next print you do, watch the first layer closely to make sure those rings are stuck in place and properly extruded

[JustinDeming]

Thanks Joe, but the small circles aren't being printed on the first layer. They should be printed on top of the "bottom" of the case, which is about 10 layers high. I always watch the first layer carefully to be sure it's adhering well.

Also, I had the same problem with another part that had a circular depression, which was printed on a raft. That part ended up with a hole twice the size it should have been because the wall was a mess, and almost not there at all.

I just don't see how this could be environmental. Also, those holes looked good on the first layer, the ugliness developed on higher layers. I can show you the back of the part. Typing this reminded me of something. I have been using a 2 process setup, starting the part at .2mm for the first few layers, then switching to .1mm. I'll have a closer look at the settings on the .1mm process to see if there's something weird in there.