Problem with Bowden extruder with ABS 3.0mm filament

Is anyone running 3.0mm ABS with bowden cable for your extruder? Do you have any problem with that?

I just switched to using extruder with bowden cable and I had some problems: First, I have to increase temperature on the hot end from 210 - 220*C, then I have to reduce the print speed from 60mm/s down to 40mm/s, but then the extruder fails alot more often. the hobed bolt (cut with a 8mm tap) bites the filament after some sort running.

Another problem is that it looks like I have to increase E-steps, otherwise I have a lot of gaps during the prints. While I don't think I should change this E step because it was printing fine with direct extuder / hotend, I'm puzzled at how I should fix this? Should I increase E steps? or should I increase temperature and slowing down the print more?

I also have this problem: when I print the 20mm test cube, one of the corners (the corner at lower left where it finishes the old layer and starts a new layer) looks like a bump because it has more plastic than other. I didn't have this problem when I was printing with direct extruder (at both same or higher print speed). I think back pressure from the hot end still extrudes a lot of plastic while the print head (hotend) is slowing down.

Anyone has any tips how to calibrate / fix this problem?


Thanks very much

-Thanh

"The Bowden cable system has one major drawback: Hysteresis. The plastic filament will compress in any extruder, but putting pressure on such a long length of filament will multiply the effects of this compression, leading to springiness. The flexibility of the PFTE tube exacerbates this problem."

yes i have a system that uses a bowden cable. I have used abs black, but mostly stick to pla. it is my ultimaker clone. the hot region is really short. there are issues if you use any other material that pfa or ptfe cable tubing with friction, and the tubing stretches in size slightly.


if you have uneven filament flow i would suggest to not turn up flow rate, but to have skirt and brim feature enabled. you want nozzle to build up a little pressure before your print begins. retraction is a must. It may be possible your flow rate is already too high. with the skirt feature doing at least 10 loops, this should pressurize the nozzle

cura seems to print better for this setup rather than slic3r. the technology to clean up defects such as oozing, and flow around corners are more advanced, even with the default settings. also kisslicer has impressive results with this as well.


temp seems to be too low for abs. you really want it to be more like a liquid and easily pass thru the nozzle. if your setup can handle it raise temp to at least 240 for abs. I run my abs at 250. pla at 200

Edited 1 time(s). Last edit at 05/12/2013 09:22AM by jamesdanielv.

Thanks for your help James.
I am using pfte tubes I bought from mcMastercarr. Not sure if that's okay to use or not.
Thanks for the tips about the software settings and temperature setting. I'm running with ReplicatorG with Skeinforge 40. I haven't tried slicer yet. The 210* was running fine for me with direct extrusion and have he some okay bridges.
I will try again with temperature at 240 - 250 and see if it works. I needed some emergency print and took thrthe Bowden off. I need this set up so that the hot end tip can get closer to the bed and still stay level. The printed pribtrbot is not that sturdy.

Thanks

Thanh