Gen 3 and Pololu on Extruder

I got a P4AC 4 axis controller by ljyang that uses Pololu 1201 stepper controllers running with the Techzone Gen 3 Remix motherboard and extruder controller on my Mendel. I have it set for 1/16 steps on X and Y, 1/4 steps on Z and 1/2 steps on the extruder.

I wanted to set the extruder to 1/16 steps but I noticed that the retract/restart speed with Skeinforge 040 was noticeably slower with 1/16 steps than with 1/2 steps. This prevented retract/restart from working right so I configured the Pololu for 1/2 steps on the extruder. I set the correct steps per mm in the firmware in both cases. Here's the code with the 1/16 steps commented out:

#define E0_STEPS_PER_MM   85.365      // NEMA 17 59/11 geared extruder 8mm diameter drive SF 40 defines this based on feedstock
#define E1_STEPS_PER_MM   85.365      // NEMA 17 59/11 geared extruder 8mm diameter drive SF 40 defines this based on feedstock
//#define E0_STEPS_PER_MM   682.92      // NEMA 17 59/11 geared extruder 8mm diameter drive SF 40 defines this based on feedstock
//#define E1_STEPS_PER_MM   682.92      // NEMA 17 59/11 geared extruder 8mm diameter drive SF 40 defines this based on feedstock

I took a quick look at the FiveD firmware that I'm using (reprap 20100719) and I couldn't see any parameters that limits the extruder speed. Is this a firmware limit or is this a Gen 3 motherboard limit?

Quote
brnrd
I wanted to set the extruder to 1/16 steps but I noticed that the retract/restart speed with Skeinforge 040 was noticeably slower with 1/16 steps than with 1/2 steps.

YES, I would guess about 8 times slower if you didn't change the retraction speed in Skeinforge and generate the gcode file again.

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

Actually, you don't need to change the retract/restart speed in SF or regenerate the G-code file as long as you change the firmware values for E steps per mm since F is specified in mm/min and E is specified in mm. The conversion to steps is done in the firmware. Anyway, I did regenerate the G-code file and I tried changing the retract speed but saw no effect when I had the stepper on the extruder at 1/16 steps.

Edited 1 time(s). Last edit at 03/21/2011 08:01AM by brnrd.

Hmmm... Strange, this should also work at 16x (gives a better sound when extruding).
But, whatever works for you...

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

Do you have this working on a Gen 3 board?

I thought there might be something different about the SDA/SCL pins that the motherboard is using to drive the extruder stepper. But it seems that these pins are also connected to digital I/O pins just like the ones driving the 3 stepper motor controllers.

I am using the double bridge on the extruder board and not a seperate pololu (although I bought some just in case) so I have always been using half stepping.

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

Well, after switching to a real stepper motor controller, that high pitched whine is gone.