Calibrate E - Printrbot

I'm trying to do the E calibration on my Printrbot. I extruded my 30mm and did my measurement, and came up with 28.6mm, so I did the calculation and put my new value into Slic3r, sliced and loaded the file into Prontoface and got 27.76mm, then 27.81, then 27.52, then 27.74, then 29, then 28.53. So clearly I'm doing something.

Currently my Start G-code in Slic3r is:

G28 ; home all axes
M92 X64.8592 ; calibrate X
M92 Y64.8592 ; calibrate Y
M92 Z2387.0719 ; calibrate Z
M92 E600 ; calibrate E

The wiki page for the getting started guide mentioned something about setting the new E value to active, and that I would need to either "slice and print an object" or "send the command to the printer using the Pronterface console".

I understand that changing the M92 for E in Slic3r does not affect the printer until it starts printing. I entered M29 E600 into the "send code" box on Pronterface. When I click send the extrusion motor runs backward and does not stop. I have to turn the power off in order to get it to stop running backward.

How do you calibrate "E"? Obviously I'm missing something.

If you got 28.6, then change E600 to E629.37 in the start code area of Slic3r.

BTW, I prefer to extrude 100mm as then my measurement error is less significant.

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[www.matter-replicator.com]

I guess I need to explain myself more. I know the formula for adjusting the G-code for E. What I was trying to say is that every time I adjust it nothing changes in the amount of filament fed.

Also that doesn't explain why when I enter M92 E600 into Prontoface it makes my feed stepper motor go backwards.

How do I force E600 or anything else I want to set into Prontoface so I can test it?

I like your 100mm idea once I get this first part figured out.

Thanks.

Put this into your start code:

M92 E100 ; calibrate E

Then tell it to extrude 30mm. Hopefully it will extrude 5mm.

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[www.matter-replicator.com]

I entered M92 E100 ; E calibrate and hit "Send". Extruded 5mm six times and still got the same about out, no change from before.

Still stiffled

What do you mean by 5mm six times?

If you said to extrude 30mm, it should extrude 5mm one time.

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[www.matter-replicator.com]

Extruding 5mm six times is the same as setting it to 30mm and extruding it once.

Try getting rid of the comment at the end of the line when you're sending it through the command box in pronterface, I've seen that cause problems in the past. If you're setting a calibration and not issuing the "save to epprom" command then it's returning to the default value every time you restart the printer, so it would appear that nothing changes. I've no idea why a setting of 600 would reverse the motor