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Direct drive slipping

Posted by krakadu 
Direct drive slipping
March 11, 2014 04:15PM
Hello,
This is my first post here so ... Greetings everyone.

A few months ago I bought a chinese kit for a modified Prusa i3 called Pangu from rp3d.com and it's been wokring pretty good until last week. I finally decided that it's time to tweak with the firmware and found a topic about my printer on the soliforum where a guy had uploaded a new version of marlin that he had modified to work with his Pangu. So I got that and calibrated it to get exact movements. Besides the red lamp on my melzi board that stopped working after i used the reset button, everything was fine. Here's the last good print that I got and one before the firmware update:
Old: [www.dropbox.com]
New: [www.dropbox.com]
All seemed fine...

The problem is that soon after the test cube the direct drive gear of the extruder started slipping and digging in the filament. It works at first and easily extrudes a few mm but then it just "clogs" or something.
Here's the amount I can extrude: [www.dropbox.com]
And a few pictures of the cold-end:
[www.dropbox.com]
[www.dropbox.com]
[www.dropbox.com]
[www.dropbox.com]
[www.dropbox.com]
[www.dropbox.com]

I'm using 3mm filament,
the extruder is a Nema17
I did set the voltage for the motors after I built the printer - should be ok.
Tried printing with temps between 220 and 240 deg - same thing
Changed the hot-end the day after this issue developed - still the same thing, with the old one and with the new one.
0.4mm nozzle
It gets hard to push the filament even manually...
The guy who's firmware I'm using said he had it set for 1.75mm filament but I'm not sure where it shows. Is it even in the firmware? Isn't it slic3r's job to calculate that?
Here's the topic on soliforum: [www.soliforum.com]

here's the frimware:
Quote

#define NUM_AXIS 4 // The axis order in all axis related arrays is X, Y, Z, E
#define HOMING_FEEDRATE {50*60, 50*60, 3*60, 0} // set the homing speeds (mm/min){50*60, 50*60, 4*60, 0}
// default settings
#define DEFAULT_AXIS_STEPS_PER_UNIT {80, 80,3200,151.111}; // default steps per unit for Ultimaker {78.7402,78.7402,200.0*8/3,760*1.1} {100,100,3200,836}
#define DEFAULT_MAX_FEEDRATE {500, 500, 5, 10000} // (mm/sec)
#define DEFAULT_MAX_ACCELERATION {3000,3000,100,10000} // X, Y, Z, E maximum start speed for accelerated moves. E default values are good for skeinforge 40+, for older versions raise them a lot.
#define DEFAULT_ACCELERATION 3000 // X, Y, Z and E max acceleration in mm/s^2 for printing moves
#define DEFAULT_RETRACT_ACCELERATION 3000 // X, Y, Z and E max acceleration in mm/s^2 for retracts
#define DEFAULT_XYJERK 5.0 // (mm/sec)
#define DEFAULT_ZJERK 0.1 // (mm/sec)
#define DEFAULT_EJERK 2.0 // (mm/sec)

Any tips will be useful, thanks for the time and help.
Re: Direct drive slipping
March 11, 2014 05:45PM
Have you checked that the hotend temperature is corect after the firmware update.

Could be a wrong thermistor table.
Re: Direct drive slipping
March 11, 2014 06:51PM
Quote
krakadu
... direct drive gear ... using 3mm filament ...
Honestly, I'm surprised this worked at all. Usually direct-drive extruders just don't have enough torque to drive 3mm filament at any reasonable speed.

Quote
krakadu
The guy who's firmware I'm using said he had it set for 1.75mm filament but I'm not sure where it shows. Is it even in the firmware? Isn't it slic3r's job to calculate that?
Yep. The firmware doesn't care what the filament diameter is, only how many steps it takes to drive 1mm of filament into the extruder.

Quote
krakadu
It gets hard to push the filament even manually...
This is indicative of a problem that is separate from the firmware or extruder drive. Perhaps, as Ralf mentioned, your temperatures aren't accurate? Or maybe the problem is with your hot end? Those Chinese J Head clones tend to be of poor quality, and replacing the hot end with another one doesn't rule out the possibility of the hot end being the problem.


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Re: Direct drive slipping
March 13, 2014 02:31AM
I switched to the old thermistor table and got a few successful test prints. I guess that was it grinning smiley

Thank you.
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