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Problems with flow rates, extrusion etc

Posted by skebengaboy 
Problems with flow rates, extrusion etc
December 26, 2013 12:51PM
I'm really struggling to get past the hurdle of getting out my first print. I'm using the ormaxis.g file. I assume it is all set up ready to go for the Ormerod.

I don't seem to be getting extrusion when I should be. I'm using the PLA that came with the printer. We bought three reels, so I'm not sure if it was the one in the kit, or another supplied by RS, but it is the white one.

My hot end temperature at "room temperature" is in the region of -5 to 0 degrees, so I'm a little suspicious of the measurement to start with, but the docs do say that the sensors are more accurate at the working temperature. The other thermistor, for the bed, gives a pretty good temperature, about what I'd expect. I couldn't get anything out of the extruder at 200C, so I kept increasing the temperature, but at 260 I lost my nerve, fearing that I might do something some harm.

I don't know what to expect, but I was hoping that I'd see a steady stream of filament coming out of the hot end when it was hot enough. Just like extruder drive I'm also seeing slippage in the extruder drive, but it isn't intermittent, it is pretty much constant. I've tried to drive the extruder at minimum speed, but it doesn't seem to go slower than about 1mm/sec. If I ask for anything slower, the extruder doesn't go any slower. I might be missing something? I'm trying to get manual extrusion by:

G1 E1 F20 (or some other tiny value)

I've managed to get to the third layer of the calibration test piece, but even those three layers are not great quality. Then it seemed like the hot filament stopped flowing...

I'd really appreciate some tips to get me over this first hurdle. Now that the machine is assembled and working I'd really like to get to a printed part and continue with getting the calibration sorted out.
Re: Problems with flow rates, extrusion etc
December 26, 2013 05:27PM
If you have problems of getting the filament out even at high temperatures you might check the nozzle entry, the teflon tubes, the filament tube and the extruder drive if everything is clean and fits together.
Try to push filament through the filament tube with the tube at the end of the hot end disconnected. There might be something blocking the extruder/ filament flow. This seems to be more evident, as the extruder stutters.


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Re: Problems with flow rates, extrusion etc
December 26, 2013 05:36PM
are you actually extruding something? is the extruder gear turning or is it stuck?
when I first put the printer together I did not tighten the nylon nut enough and I could feed PLA to prime the extruder but then the stepper motor would "spin". You want to make sure that extruder drive is squeezed between both bearings byt tightening that nut (within reason).
Re: Problems with flow rates, extrusion etc
December 26, 2013 07:37PM
It sounds like a partial block of the nozzle to me. We're working on an Ormerod specific troubleshooting guide, but for the moment our Tricolour Mendel troubleshooting guide holds much useful information. See: [www.reprappro.com]

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Re: Problems with flow rates, extrusion etc
December 27, 2013 03:54AM
My hot end registers either 5.4 or 9.8C at room temperature, which is about 20C where I have the Ormerod. It sounds as though yours is 2 quanta of measurement lower at room temperature than mine. I guess it's not impossible that you have a dud thermistor, or that you overcooked it while shrinking the PTFE sleeving on. I would ask RepRappro for another thermistor + heatshrink. But a blockage is certainly another possible cause. Perhaps you could check whether you can melt PLA filament on the outside of the nozzle, to see if it is up to temperature?

Edited 1 time(s). Last edit at 12/27/2013 03:56AM by dc42.
Re: Problems with flow rates, extrusion etc
December 28, 2013 07:45PM
To add some detail regarding diagnosis of poor extrusion problems:

We are in the process of writing a troubleshooting page for the Ormerod to cover these sort of problems, but most of this information will come from our existing instructions from our other printers, the Mendel and Huxley. See: [www.reprappro.com]

Construction is slightly different, but most of the advice is valid. Some useful pointers:
1. Is the hot end fan on all the time? If it is not, the filament melts too far up the nozzle, and extrusion is very difficult
2. Test the nozzle is working okay by disconnecting the Bowden tube from the extruder end (remove the tongue) and feed filament down the tube, with the hot end heated to 200C. The filament should extrude by hand, with a little pressure. If not...
3. It could be that the nozzle is partially blocked; see the guide above for help clearing this.
4. With the Bowden tube removed feed some filament into the extruder, and test the movement of the extruder. There isn't much to go wrong, but make sure the teeth of the hobbed insert are clear of chewed up filament, or the filament will slip.

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