2014-02-13

Makibox A6 HT - reliable Slic3r settings?

I may have found reliable setting for the default extruder of the Makibox A6 HT!

It finished several prints from 5 minutes to more then 3 hours without any manual intervention.
Something I haven't seen since I own this printer!
There is some grinding and blockage but only every 1-2 days and for obvious reasons (plastic blobs accumulating in the parking position,...)

Mechanics

Do all the tuning steps. Especially check the stepper motor reference voltages.
Make sure the X and Y axis and the hot end are loose enough to slide without any unusual sounds and nearly no force at all.
Make sure the springy plastic wheel in your extruder can rotate. If not, use a round file to widen the axis holes slightly. I filed a small filament-shaped grove into the surface of the wheel to reduce pressure to the filament.
Oil the trapezoidal rods of X and Y axis, the smooth rods and also the 4 plastic axes of the filament reel holder in the back.
Insert the filament spool into the back of the machine

Make sure the machine is cool (hotend less then 60°C) before you start printing.
Make sure the outside of your nozzle is clean. (Don't care for the hole.)
Always retract the filament until it is completely outside the hot end after printing.
Before starting to actualy print, manually insert the filament until it has overcome the barrier between bowden tube and the actual hot end (there's a slight change in resistance and a noise), then slooooowly go further until you feel the resistance of the plastic hitting the bottom of the extruder.

Basic settings

I started with the default Slic3r profile "A6 General (HT PLA) v0.3" from Makibox.
Then I did the following modifications:

Printer Settings

  1. Leave layer height at 0.2mm
  2. Leave the first layer height at 150%
  3. Speed: Reduce External Perimeter and Perimeter speed to 20mm/s
  4. Advanced: Extrusion width of First Layer: 200% 
The first layer needs to stick. So we push out twice as muchfilament as needed, to make sure it does.
The slow perimeters help making round holes round instead of D-shaped.

Filament Settings

  1. Increase PLA temperature from 193°C to 218°C
  2. Leave printer bed temperature at 60°C 
The increased temperature lowers viscosity and thus the force required by the extruder.
Thus reducing filament stalls due to the extruder grinding.
It also makes the first layer stick much better.

Printer Settings

  1.  Reduce retraction speed from 70mm/s to 25mm/s
  2. Reduce the retraction from 4mm to 2mm.
  3. Increase "minimum travel after retraction" from 2mm to 4mm (At least twice the retraction.)
 Together with the increased temperature this seems to prevent filament stalls due to the extruder grinding.
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