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ABS benchy issues

Posted by Eikonals 
ABS benchy issues
June 15, 2017 12:19AM
I've printed a benchy in ABS and seem to be getting some layer issues. The print has these thick lines and is not smooth whatsoever. Also most of the internal dimensions are off.

Here is an album with pictures of the print and details on my configuration:

Possible sources of error I am currently considering: lack of enclosure to keep up ambient temperature, backlash from clothespin belt tensioners, Z-axis bobbing up and down due to the extruder assembly being only held by 2 bolts, amount of filament deposited (extrusion speed too fast or print speed too slow?).

Things I've tried so far: adjusting temperature of the bed between 100C and 112C, adjusting temperature of the hot end between 230C and 240C, calibrating extruder for filament length.

Has anyone encountered this before or have any ideas on how to address it?
Re: ABS benchy issues
June 15, 2017 01:50AM
What was the nozzle diameter, extrusion width and layer height? Did you succesfully print a testcube before?
Are you sure, this is ABS? It's so transparent...
Re: ABS benchy issues
June 15, 2017 02:06AM
Nozzle is 0.4 mm
Layer height is 0.2 mm (as described in the album)
Extrusion width was set to "auto" in slic3r
I've not printed a testcube as I've seen recommendations stating that benchy is a more thorough test.

Yes this is definitely ABS, it dissolves in acetone when I make my ABS juice for getting first layer adhesion. It is 1.75 mm ABS Hatchbox transparent white. Here is an amazon link to the filament as it doesn't seem to be listed on the Hatchbox website anymore:
Re: ABS benchy issues
June 15, 2017 03:30AM
"perimeter print speed of 40 mm/s external perimeters at 64 mm/s"
I'm pretty sure this is quite unusual. I didn't change lots of my Sl1c3r settings, but my perimeters are printed at 60, and my external perimeters at 30 mm/s. In Cura I set 60mm/s inner, 40mm/s outer perimeters.
Try to swap those speeds, the outer perimeters usually get printed somewhat slower to improve surface quality.
Re: ABS benchy issues
June 17, 2017 06:26AM
Looks like reducing the perimeter speeds gives a substantial improvement to the surface finish. I brought down the perimeters to 60 mm/s and the external perimeters to 30 mm/s.
Images of the improved prints:

Outer dimensions are still good. Inner dimensions are typically 0.3-0.5 mm off from those listed in the 3DBenchy Brochure.
There are still some deformities on the smoke stack and at the tops of windows and doorways.
I'm more concerned about the inner dimensions, is a 0.5 mm error normal?
Re: ABS benchy issues
June 17, 2017 10:44AM
Inner dimensions always get smaller than they should. Lots of reasons, discussed 100 times. 0.5mm smaller, I assume. Yes, that's normal.
Window & door tops: bridging problem. Quite normal, too. Yours doesn't look bad, as far as I can tell from the pic. Transparent filament is not optimal for showing printing issues. Depending on your slicer, you may experiment with:
less material while bridging
printing faster during bridging
lower temp for a few deg

And to the chimney: This is the topmost part of the benchy. With your printing speed, a layer will be finished within a few seconds, maybe 10. When printing the next layer, the last layer is still way too hot. From a feeling, I'd say the chimney must be printed at 10, max 15 mm/s. If your slicer can do that, increase minimum layer time. Maybe 30 or 40 seconds. If not, slow down. Set feedrate to 25% or 50%.
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