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Extruder Motor Wont Vary

Posted by dixied 
Extruder Motor Wont Vary
February 27, 2015 03:10PM
I have just built an Ormerod 2 and i'm all done except for the calibration print. However as i was calibrating the extrusion, i have noticed that the extrusion motor runs too fast and when i adjust the rate ( In Pronterface ) it has no effect.
Anyone have any ideas as to what is wrong.

For now i have RRP 0.78c firmware in the Duet and bog standard SD card image from their Github entry.

Re: Extruder Motor Wont Vary
February 27, 2015 03:27PM
Does your second extruder motor sounds like the first one? And can you post the output of M92? Perhaps you didn't set up the steps/mm correctly.
Re: Extruder Motor Wont Vary
February 27, 2015 03:33PM

I only have one head ( Extruder ) and when i did the 100mm extrusion calibration run, the printer extruded exactly 100mm so the M92 command reports the default reply as i haven't had to apply any compensation.
For reference the reply was Steps/mm: X:87,Y:87,Z:4000 E:420.000000:420.000000:420.000000:420.000000:420.000000
Re: Extruder Motor Wont Vary
February 27, 2015 03:47PM
I must admit I haven't used Pronterface for ages, but you can do extrusion moves using G-codes like

G1 E20 F450

This one should feed 20mm of filament at 450mm/min (quite slow). Can you notice any difference when you run it?
Re: Extruder Motor Wont Vary
February 27, 2015 04:07PM
Sent G1 E20 F450 then G1 E20 F50 and both were the same fast rate i keep getting.
Re: Extruder Motor Wont Vary
February 28, 2015 11:20AM
Sounds like a minimum speed issue (M204 & M205 settings). See if you have any of those parameters in your config file, and maybe also try flashing with the latest firmware.

Re: Extruder Motor Wont Vary
March 03, 2015 08:56AM
There's a small 'gotcha', due to the way the firmware implements minimum axis speeds, with feeding filament. When you send individual commands, the extruder always turns very fast. You have to extrude very short amounts (like 5mm), or the filament is moving too fast for it to melt, so eventually the extruder skips. The minimum extrude speed is set in config.g to:
M566 X1200 Y1200 Z30 E1200

This is because it needs this setting when doing a full print to make the extruder work correctly in all situations. Fortunately, this bug has finally been fixed in our latest development firmware, and we will be reverting the minimum speed so this doesn't catch people out. When actually printing, the extruder moves much more slowly when extruding. If you try the snowman.g, you'll see what I mean.

Generally, I load filament by hand anyway (turning the large gear), because it's useful to feel if there is any resistance to movement, which you won't feel when you command the extruder. You can also override the minimum speed, and send M566 E50, and you can then extrude very slowly. But revert the setting before printing.

RepRapPro tech support
Re: Extruder Motor Wont Vary
March 03, 2015 11:00AM
You could always use my 1.00-dc42 firmware series, which doesn't have any minimum speeds due to the use of completelty different and more precise movement code. smiling smiley

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
Re: Extruder Motor Wont Vary
March 03, 2015 11:01AM
I just discovered this in my config.g file ( Thanks Dave for the clue ) not ten minutes ago and as i went to post the result, noticed you have posted the cause. I hadn't tried printing as i thought it would fail with it extruding so fast. This i now see was wrong and it would have been OK.

Ian, are there any instructions for the 2 Colour upgrade kit? Mine arrived today and there are blank pages where the instructions should be on your website.

Thanks all, i will get on with calibrating now.
Re: Extruder Motor Wont Vary
October 31, 2015 06:50PM
Am in trouble with my Prusa, Im using Repetier with ATMega boards extruding 1.75 mm, when I set up repetier and connect then go to the manual tab
and after the extruder is up to temp if I try to extrude 10 mm of filiment the extruder just sits and nothing happens.
Ive subed the motor and driver and all works as it should, I subspect my problem is in the software but Im at a loss as to where.
Hope some one can shed some light on this.
Thanks Rtty177
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