Extrusion Methods January 05, 2016 03:19PM |
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Re: Extrusion Methods January 05, 2016 04:40PM |
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Re: Extrusion Methods January 05, 2016 04:52PM |
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Quote
Srek
Controling the amount of extruded material is the key to high quality prints. Afaik noone tries to accomplish this by measuring the actual output during printing. The reason for this is that it is practically impossible to measure the extruded amount while at the same time get any kind of precision in placement of the material.
What is done is that you have to measure the exact diameter of the filament (taking into account that it might be oval) and enter this as a correction factor in your slicing software. Of course your extruder has to be calibrated so it can extrude precise lengthes of filament beforehand. With these two factors, diameter (or more exactly the surface of the crosssection) and the length of filament the software can precisely determine the volume of material that is beeing extruded at any time.
This is much easier to implement than constantly measuring the output.
Re: Extrusion Methods January 06, 2016 12:44AM |
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Re: Extrusion Methods January 06, 2016 04:27AM |
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Re: Extrusion Methods January 06, 2016 04:31AM |
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What you describe there is a fail safe mechanism to detect filament slippage/blocked hotend. For a controlled extrusion the prefered method would be a simple closed loop drive. The reason for using open loop stepper setups is just a matter of prive. I think this will change in the not to far future.Quote
leadinglights
A useful way may be to take two measurements:-
a) The filament demanded by the software. This could be by a counter connected to the extruder motor.
b) The filament actually drawn from the roll. A pair of pinch wheels connected to a counter to measure the length drawn is one way to do this.
Comparing those two counts and the measured diameter of the filament would give you a fudge factor for that roll of filament which could be used to manually change the feed factor. There are many caveats though, changing or even cleaning the hobbed drive wheel will alter the filament fed. Even the day to day temperature could have a minor effect.
Re: Extrusion Methods January 06, 2016 04:50AM |
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Re: Extrusion Methods January 06, 2016 05:08AM |
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I understand where you are coming from, but the teeth on the MK7 gears i mostly use are so flat that i doubt that there is any detectable difference in the amount of extruded material because of it. I never observed it anyway. I did have my doubts because of this when i used home made hobbed bolts for Wade extruders, but even with these, much more coarse teeth, there was never a problem like what you describe.Quote
leadinglights
I had more intended to address variability caused by material characteristics - the depth of bite of the drive wheel is significantly different between materials and even batches. While I use only observation of prints to get my "fudge factor" the last two rolls of black ABS measure up at 1.76mm but I set one at 100% feed and the other at 96% feed - the latter filament is detectably harder.
Mike
Re: Extrusion Methods January 06, 2016 05:20AM |
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Re: Extrusion Methods January 06, 2016 07:25AM |
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Re: Extrusion Methods January 06, 2016 11:42AM |
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Re: Extrusion Methods January 06, 2016 12:50PM |
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Re: Extrusion Methods January 07, 2016 04:35AM |
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Re: Extrusion Methods January 07, 2016 07:03PM |
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Re: Extrusion Methods January 08, 2016 12:48AM |
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Re: Extrusion Methods January 08, 2016 01:08AM |
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