1 Topic by jenninaj

  • jenninaj
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Topic: Extrusion quantity problems since upgrade to SD8825 stepper driver

All,

I'd appreciate some assistance from the community regarding problems I'm having with my solidoodle 2 since I changed out the A4988 stepper drivers for SD8825 ( amazon link )

I edited the marlin v1 firmware (configuration.h) to drive the stepper motors the opposite direction as required. I also changed the number of steps in the eeprom configuration to be double what they were before.

I have an E3D J hot end with 0.4mm nozzle.

Now, I've done a fair amount of mods to my solidoodle and am extremely familiar with calibrating the extruder but the problem I'm having frankly baffles me. Basically, the first layer of material extrudes correct amounts but all subsequent layers are at least double what they should be. The image shows what I'm getting for a single walled 25mm square with extrusion width requested to be 0.5mm.

I have calibrated the extrusion length (201 steps/mm pulls in exactly 100mm of filament when I request it). I've set the extrusion multiplier in both slic3r and cura to be x1.0. I've even used older versions of the two slicers in case it was some wacky new 'feature'.

When I calibrate and dial down the extrusion multiplier to get the correct width wall I have to set it to x0.43 - clearly way off (the wall in the image is over 1mm thick). This has the unfortunate effect of making the first layer insufficient to stick to the glass bed and I have to make the first layer 900% in order to get anything like the correct amount.

I have tried various Vref settings for the SD8825 - 0.5V, 0.3V, 0.7V. The lower voltages make the stepper chip groan quite morosely.

The other SD8825 I have (on X,Y,Z) are running around 1V and are dimensionally correct.

Does anyone have any thoughts, firmware changes I've missed, or goats I could sacrifice in order to fix this?

Thanks in advance.

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2 Reply by jenninaj

  • jenninaj
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Re: Extrusion quantity problems since upgrade to SD8825 stepper driver

Okay, it turns out the extruder SD8825 must have had issues - I swapped it out for an identical unit and all is well.

Next question: what are the recommended Vref or amps for these steppers to be driving. I've seen posts for the A4988 on here - presumably I should match the amps? I'm running the 3 X/Y/Z at 0.5V and the extruder at 0.3V.

3 Reply by COASTER19

  • COASTER19
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  • Registered: 2013-03-08
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Re: Extrusion quantity problems since upgrade to SD8825 stepper driver

I had an issue like this the other day...  I had upgraded my threaded rod to a M3 almost immediately after getting the printer and had forgotten to change the Z steps per mm in eeprom.  Check that your bed moves down the same amount as the software says.

4 Reply by jenninaj

  • jenninaj
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Re: Extrusion quantity problems since upgrade to SD8825 stepper driver

Thanks, COASTER19. That was the first thing I checked and printed a set of steps to determine if the spacing between each was the same and correct. That was all fine and hence my confusion continued.

However, swapping out to a replacement SD8825 fixed the problem immediately.