[KwartzLab] 3d printer progress

[Kevin Martin]

This doesn't quite look like our setup. The second 2-wire connection from the motherboard to the extruder controller is missing. The wire in the photo on this web page is the RS485 communication line that talks a private protocol between the stepper controller and motherboard, but the extra wire we have is used as step & direction to drive the extruder stepper. The protocol on the RS485 has commands for turning the extruder feed on and off, and for setting the extruder speed by adjusting the PWM duty cycle, but those are only relevant when you have a DC extruder motor (where the PWM duty cycle does indeed affect speed). When you have a stepper feeder, the PWM setting just controls motor winding current, and the actual feed speed is controlled by the rate of step pulses provided.

It also does not show the thermocouple controller board.

I would say this web page describes our setup except that it is used with a DC motor feeder and thermistor nozzle temperature sensor. The extruder firmware for this would be completely incompatible with our extruder.

The GCode we had contained both M108 (obsolete) and M113 (current) commands to set the PWM duty cycle, but also contained E coordinate words on the G01 lines that wanted extrusion. The values in the M113 commands implied that these were indeed intended as an extruder feed rate, and it is not clear how anyone expects the acceleration of the extruder speed to properly synchronize with the XY acceleration of the print head. At least the stepper pulses generated by the E-axis "motion" will properly synchronize with the XY motion. I suspect that in order to synchronize the XY acceleration with the DC extruder's feed acceleration, the GCode generation uses higher accelerations on X and Y than our steppers are tuned for, which eventually results in lost Y position.


-Kevin Martin
 the Papertrail Handmade Paper & Book Arts
 New Dundee, Ontario
 518-884-7123
 www.papertrail.ca



-----Original Message-----
From: discuss-bounces at kwartzlab.ca [mailto:discuss-bounces at kwartzlab.ca] On Behalf Of doug moen
[...]
For future reference, we are using these electronics:
http://reprap.org/wiki/Generation_3_Electronics/Tech_Zone_Remix

Doug.

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