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Prusa i3 Extruder Problem

Posted: Sat Feb 11, 2017 1:28 pm
by Micromet
Hi - I'm a new 3D printer person and have the following problem. I have a Geeetech Prusa i3 Pro B printer - which generally works fine except that extruding is inconsistent. If I leave it to itself, I get either full or partial fill layers. Edges appear to be OK. However, if I apply moderate downward finger/thumb pressure to the filament above the extruder - I get consistent layers laid down. So it seems to be the direct drive extruder problem. I have adjusted the Motor voltage output on the A4988 Driver board to be 1.0v to maximise the motor output. With the MK8 nozzle removed and setting extruder temperature to 80 deg C to allow filament movement within Repetier-Host, I can get filament to move through the system OK and have calibrated the extruder "Steps per mm" OK in the Marlin Firmware EEPROM Settings. So the motor and hobbed gear are doing their work OK except when the nozzle is on. I am using 0.4 mm nozzles currently with PLA but would like to move to ABS - but can't really until I get this problem sorted out. I have thought about using a DIY clock-spring pressure feed about 50mm above the extruder entrance to mimic my finger/thumb pressure (the 50mm distance to allow retraction to take place). I have even put grooves into the idler pressure wheel in the extruder to see if this helped with what I thought was filament slippage - but this didn't improve the situation.

There may be options inside Repetier-Host to do with the Printer setup that, as a beginner, I have overlooked or not understood. Any pointers would be appreciated.

Re: Prusa i3 Extruder Problem

Posted: Tue Feb 28, 2017 9:27 am
by iDig3Dprinting
Hi Micromet,
If it is all calibrated ok then it is to do with pressure on the filament against the hobbed bolt, possible in combination with a blocked nozzle??? But the pressure required on the filament against the hobbed bolt is not so great as that this should be causing and issue so you may have to look downstream from there. One other thing to look at is whether the path from the hobbed bolt into the heat break is obstructed in any way. Do you have ptfe tubing to guide the filament. Sometimes kinks in this or a poor path down to the hot end can cause feed problems.

I assume that the hot end is heating up OK so that you are reaching print temperatures?

Re: Prusa i3 Extruder Problem

Posted: Mon Mar 04, 2019 9:58 am
by steveprinters29
There may be a lot of options inside the Repetier-Host that you could have missed and you can only get information on this when you use the user manual of your 3D printer.
Through this, you would also get better information about the 3D printer temperature settings etc.