Sunday, August 14, 2011

Test printing continues...then stops! :-(

[This is a duplication of the update I just posted to the forum ( but I wanted to log my current status here on my blog also.]

Update: I removed the extruder drive shaft and re-hobbed it cleaner and deeper (M3x0.5  tap). I tightened the springs on the idler bearing also once re-assembled, and tigntened some other cold-end motor mounting bolts that had come slightly loose. The whole assembly grabbed and fed the filament much better. Deffinetly no slippage now.

I adjusted some Skeinforge  setttings also before re-commencing so test printing.
Speed – Feed and Flow Rates 15mm/s, With over Thickness (both) 1.5, Layer Thickness .35mm.

Looking at thinks now, I think my layer thickness should be reduced, given my nozzle hole is .4mm.

Extruder retraction changed from 1mm to 2mm and retraction speed from 20 to 30mm/sec. Cleaned up blobs a lot!

I re-checked my firmware flow setting (E0_STEPS_PER_MM) and increased it slightly – now set to 540.

I’ve lowered the temperature from 200Dec C to 195Deg C. That’s its Target Temperature set in RepSnapper and it hovers at an actual of about 185. (I don’t have a digital thermometer so I’m going on look/feel of extruded plastic. When I lowered the target even more the stepper had trouble pushing the filament, and started skipping steps. I could increase power slightly to the stepper, but I think that would risk increasing hot-end pressure – it’s a balancing act.

I’ve removed the blue tape from my Perspex platform and the PLA took to the Perspex very nicely. It separated easily when cold and gave a good finish to the base of every print, visible in photos.

Some new test prints:  (Ignore the little number tabs in the pictures. They are for my own notes only.)
Circuit board spacer (my square test piece)


LM8UU Linear bearing holder

General view of LM8UU holder




The infill on what should be a solid top surfaces needs improvement. It may be my layer height for my given nozzle diam (.35mm for a .4mm nozzle). I’m not sure. I’m going to change parameters slowly and continue my observations. A general remark is that these photos are very close-up and stepping back the items I’m printing are robust and very useable.
Oh… there’s a great bunch of test objects here and some interesting discussion with it also, which I must return to:

Late update: In removing the extruder earlier today to make some change, I snapped off the wire from the heat resistor. I don’t have a spare resistor so that puts me ‘dead in the water’! :-(

I’ll have to order one from somewhere tomorrow.

Thanks to all for observations and feedback on the forum. Hope all the photos and detail isn’t too monotonous folks. It’s been invaluable to me.


1 comment:

  1. The optimal layer height for a nozzle is approximately 0.75 * the hole diameter. For a 0.4 mm hole this would be 0.3 mm. I am still printing with a 0.5 mm hole using a layer height of 0.375 mm.