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Extruder issue?

Posted by smithilesj 
Extruder issue?
October 24, 2014 09:46PM
Hi, I've built a kit I bought from this website. I do regret going for the cheap kit but I've learnt a fair bit trying to get it to work. So I've been able to get some rough (very rough) prints (see pictures). I'm using pla at 200 degrees. I've calibrated the esteps and I'm still getting dodgy prints, the 0.5mm thin wall print doesn't work at all (see pictures). I read somewhere about adjust the pololuo drivers but can't find a good how to. I don't know what I'm doing wrong, any help would be very appreciated smileys with beer

All prints
0.5 mm wall
20mm box
Re: Extruder issue?
October 27, 2014 06:33PM
You are without doubt under-extruding. This could be caused by:

1. Incorrect e-steps per mm value.
2. Slipping small gear on the extruder (easy to check and tighten).
3. Insufficient tension on the guilder (easy to tighten, extrude a bit and check again).
4. Print speed is too high, causing skipping steps on the extruder. Reduce speed.
5. Vref too high or too low, causing skipping steps on the extruder. Vref too high will cause overheating, so check the temperature of the stepper motor and pololu driver board for high temperature.

Once you've checked / eliminated 1 through 4, go on to the vref. The best way to set it is to work out the correct value and set using a multimeter. If you don't have one, you can still set it, but it's more of a trial and error thing.

There is a trimpot on each stepper driver which you can see clearly in ololu_v-ref_checking.jpg" target="_blank" rel="nofollow">this picture. The red probe is resting on the trimpot. To adjust, use a small jeweller's screwdriver to turn the trimpot a very, very small amount clockwise to increase vref, or counter-clockwise to decrease. If your driver board is cool after a print, try increasing the vref slightly and try again until you get good extrusion. If hot, decrease slightly.

If you have a multimeter, it's easy to check the vref on the steppers. Rest the red probe on the trimpot and the black probe on the negative power terminal for your RAMPS board and read the vref. Use this page to determine the correct value for your board (be careful, though - the page referenced is for the Pololu A4988. There are references at the bottom for Stepstick and G3D driver boards, which require a slightly different calculation).

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