Layers missing in Benchy
Can you help identify what the issue is with these failed prints?
The last Benchy almost printed well, but has very weak layers at the top of the doors.
The previous ones failed totally when the layers did not print and I either stopped the print manually, or it 'completed' without extruding the filament for the upper 3/4 of the Benchy.
On the print that 'completed' but with no upper 3/4 of Benchy having appeared, I found that the filament had 2 notches ground out of the part just above the melt-down area, and then a deep notch where the extruder pulley had eventually just spun without gripping at all.
I thought maybe it is due to the retraction setting s of 5mm retraction with 120mm/s speed, and changed it to 2mm at 40mm/s for the last print, the one that has the fault in the upper part but otherwise completed.
I also increased the extruder idler tension so the springs are now 12.3mm instead of 13mm long.
Any ideas how to fix it?
Thanks, Mik
Re: Layers missing in Benchy
Can you help identify what the issue is with these failed prints?
Where did you download your Benchy? I know there were some posts here about 4 weeks ago that ended up (primarily) being a bad Benchy download.
Re: Layers missing in Benchy
Can you help identify what the issue is with these failed prints?
Where did you download your Benchy? I know there were some posts here about 4 weeks ago that ended up (primarily) being a bad Benchy download.
A valid point, but I think not to blame for the current problem, because the failure occurs at different z-levels when using the same .gcode file generated from the Benchy.stl file, which I think I downloaded from http://www.thingiverse.com/thing:763622
I have another print in progress right now, after another failed one with increased idler screw pressure, and my money is on this explanation for now (but only until this print fails, then I'll come up with another hare-brained explanation, no doubt!):
I used a Taulman T-Glase idler since one week, and T-Glase is too flexible for this application. The idler bends, worse so when the temperature inside the housing rises during a print, until the pressure against the filament is so weak that fast movements (like during 5mm x 120mm/s retractions) do not work any more, but it grinds the filament away instead of pushing it along.
For the print in progress (3DBenchy_ZH5-120_PLA-EM1.053_0p1D.gcode), I have replaced the extruder idler with one I printed a couple of weeks ago, from polycarbonate. It has it's tip snapped off, which took all the effort of an ambitious teenager for 10-15minutes before it snapped. It's tough, does not bend much, and has a comparatively high glass transition temperature.
The print is up to Z 4.35 and looking fine so far.
Re: Layers missing in Benchy
The print was messed up again, producing several layers that can be pulled apart easily by inserting a fingernail and then pulling, with most of the print in-between looking OK. After a few mm, no filament was deposited at all but the hotend continued to 'ghost-print".
Next theory: Filament might be dodgy.
Next print running now is using the PRUSA filament that came with the printer, PLA, orange.
Same .gcode file as before (3DBenchy_ZH5-120_PLA-EM1.053_0p1D.gcode), no changes to the tension of the extruder idler screws, using polycarbonate idler with springs screwed to 12mm length.
Re: Layers missing in Benchy
The test with PRUSA PLA filament also ended as a 'ghost print' . Benchy printed nicely to about z 10, and then the print continued without deposition of any filament.
I think the extruder body and cover made from Taulman T-Glase also need to be replaced, so the extruder stays rigid when it gets hot in the enclosure.
The challenge is now to print new extruder parts with the printer as it is, or I need to put it back together using the old parts.
I'll try to print the parts in polycarbonate without closing the enclosure, maybe that will keep the T-Glase extruder cool enough to maintain tension on the filament.