I’m at “member” level - but still not allowed to attach STLs.
Well idk about bambu forums layers of membership but I made a cylinder that’s printing now.
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It printed fine at like 1mm height so idk.
20mm x 12mm id x 10mm height is printing now in tpu.
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Set retraction and max volumetric speed in the filament settings. Find the filament, click the notepad and pencil next to it, and find volumetric speed and retraction. Set retraction to 4. Almost no stringing.
Did a manual calibration of flow rate, which changed Flow Rate in filament settings from 1,0 to 1,2. Then printed these.
Top shells: 5
Left: Random seam
Right: Aligned seam
The top layers seem “starved”.
I saw the same during the manual calibration: Never got a smooth top layer, just a “grid” with openings between the lines.
One of the best samples during manual calibration (flat lighting to highlight the surface pattern). According to the instructions, I should select the one with the smoothest surface. None had a flat surface, always this grid pattern.
Hmm, It does look underextruded which is strange if your flow ratio is 1.2. These were printed with default flow ratio (1.0) for generic tpu. The +10 sample shows definite overextrusion. The -5 looks somewhat like your example.
I have noticed with tpu it seems good to have a low friction spool holder as the tpu can slip without throwing any errors. My Sunlu s4 dryer has a fair bit of friction on the rollers and it has slipped before trying to print tpu direct from the dryer.
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If you want to print TPU reliably you should use this change on the leaver!
I can print 82shore A very reliable!
Yes it is indeed strange to have under extrusion with Flow ratio as high as 1.2.
I use a spool holder with steel bearings, to ensure minimal pull force and no slipping.
Improvements!
After having read the printing recommendations for the new TPU 90A, where it is proposed to feed the filament without PTFE tube, I tried a similar configuration.
My external spool holder is mounted behind the printer. Instead of PTFE tube I now have a short piece of PTFE in each end. The one on the printer is pryed open at the upper end, to reduce the risk of the filament rub against the cut edge.
These are with identical print settings, the one on the right with this improved feeding setup.
The difference is significant - although I think it is still some slight under extrusion.
Tried to reduce speed to 50% (“Silent”). Photo below shows 100% left / 50% right. Maybe a slight improvement on the top layer. Maybe.
But the seam was significantly worse at low speed:
Flow 1.12 - 1.2
temperature : 210
Volumetric Speed : 2 mm/s
Time per layer : 16s
No flow calibration
PERFECT.
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