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Barely extruding any filament

Posted by Manny 
Barely extruding any filament
February 06, 2011 11:56AM
Hi there,

We've recently attempted to build our very first Reprap Mendel, but after a rather challenging assembly, we've run into a few complications. The most important one being the following:

First of all, everything appears to be working. We can move the extruder along all three axis, ABS filament is being pulled in by the extruder. We're using the Reprap Host Software for both, G-Code generation and printing. We've left most settings in the host software at their initial default values, except for X/Y axis movement speed (we've set them to 800ish each for now, the initial 3000 didn't seem to work out that well) and temperature. We set the extrusion temperature to 260°C - it may seem incredibly high, but we assume that our thermistor is off by a few dozen degrees. 260°C seems to be a temperature where we actually see some filament coming out. We're using this kind of ABS.

However, it does appear that too little filament is being pushed out by the extruder. Attempting to print any model usually results in a little bit of ABS around the nozzle, maybe even some on the board (usually barely anything).
Now I do wonder, how would be best start trouble-shooting this issue? Which settings do we change in the firmware or Reprap Host software to enforce a little more extrusion? To be honest, we're out of ideas (and decent skill) to know where to begin.

As for the machine itself, it's a "regular" Mendel with Generation 3 Electronics and laser-cut parts, Firmware as provided by the retailer. The only thing we tried so far is to increase the number of steps for the extruder to 2.8 to see if that increases the output.

Thanks in advance,
Re: Barely extruding any filament
February 06, 2011 12:24PM
Hey Manny

Is your feedstock in fact being pulled into your hot end by your motor?

It would certainly be strange if it was and nothing was coming out!!

Check to see if the filament is in fact progressing into your extruder. If so then it could be that your gcode is instructing your extruder to extrude way too little.

I have been having problems with my extruder this weekend (only started pushing plastic Friday night), but I think I may have cracked it. See this post.

What happens when you use the EXTRUDE button on the host? I get, with 0.5mm nozzel and speed setting at 3000 about 5-7mm travel of the 3mm feedstock each time.
Re: Barely extruding any filament
February 06, 2011 12:30PM
I would suggest positioning your extruder over the dump zone, let the extruder heat up and extrude in air. Then measure the diameter of the extruded plastic after it cools down. It should be close to your nozzle diameter. If it's right, then you need to play with the sw settings. It's also possble that ABS is not sticking to the bed. Is it heated? What's the surface? I haven't used ABS yet but I will start as soon as the first 5 lb of PLA is finished. But I read that the extrusion temperature is more critical for ABS than PLA since it has a broader glass transition temperature.
Re: Barely extruding any filament
February 06, 2011 11:44PM
Do you have a wades extruder? the page you link to has a picture on it of a mendel with a wade's. If so, you might need to adjust the pressure of the idler bearing. Not enough pressure and the teeth won't bite into the filament; two much pressure and it will just grind a grove into the filament. in either case, the gears will spin, but nothing will come out of the nozzle.
Re: Barely extruding any filament
February 07, 2011 03:40PM
Buback Wrote:
> Do you have a wades extruder? the page you link to
> has a picture on it of a mendel with a wade's.

Exactly that one, yes. From the looks of it, it is pulling filament just fine. But it looks like the non-mechanical parts (software, firmware, I don't really know which one) don't "request" sufficient amounts. Then again, we suspect that our thermistor readings may be off and the ABS simply isn't heated enough. (Unfortunally, we don't have proper equipment to test the temperature.)

As for all the responses so far, thanks. We'll look into it and give an update next time we find the time to gather more information and tinker with our mendel.
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