Re: This engineer claims 100 grams direct extruder. I want one March 20, 2016 11:01AM |
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Re: This engineer claims 100 grams direct extruder. I want one March 20, 2016 12:26PM |
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Re: This engineer claims 100 grams direct extruder. I want one March 20, 2016 01:32PM |
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Re: This engineer claims 100 grams direct extruder. I want one March 20, 2016 02:25PM |
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Re: This engineer claims 100 grams direct extruder. I want one March 20, 2016 02:42PM |
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Re: This engineer claims 100 grams direct extruder. I want one March 20, 2016 03:21PM |
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Re: This engineer claims 100 grams direct extruder. I want one March 21, 2016 04:30AM |
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Re: This engineer claims 100 grams direct extruder. I want one March 21, 2016 07:08AM |
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Re: This engineer claims 100 grams direct extruder. I want one March 21, 2016 07:41AM |
Registered: 9 years ago Posts: 1,035 |
Quote
VDX
... this would only be precise enough, if you get 'perfect' filament - with common (real world) filament the diameter and circular/oval cross section shape is often some 5 to 10 percents off
Re: This engineer claims 100 grams direct extruder. I want one March 21, 2016 09:23AM |
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Re: This engineer claims 100 grams direct extruder. I want one March 21, 2016 09:33AM |
Registered: 9 years ago Posts: 1,035 |
Quote
VDX
... no, the length/travel measuring can be super perfect - but the volume per mm value, what's needed to calculate the extrusion amount, will be some ten percents off.
So regardless, how good your feed-sensor is, the extruded volume is related to the inserted volume {= length * (varying) cross-section}, not the length alone!
Re: This engineer claims 100 grams direct extruder. I want one March 21, 2016 11:07AM |
Admin Registered: 17 years ago Posts: 13,986 |
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realthor
.. But isn't that the same situation with direct extruders?
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realthor
I believe that in this area we are at the mercy of the filament makers and getting those filaments to better tolerances.
Re: This engineer claims 100 grams direct extruder. I want one March 21, 2016 11:21AM |
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Quote
realthor
[...] would still be getting the bowden up to the same level with direct extrusion, still achieving the lighter weight of the printhead.
Re: This engineer claims 100 grams direct extruder. I want one March 21, 2016 11:42AM |
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Re: This engineer claims 100 grams direct extruder. I want one March 21, 2016 12:05PM |
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Re: This engineer claims 100 grams direct extruder. I want one March 21, 2016 12:10PM |
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Re: This engineer claims 100 grams direct extruder. I want one March 21, 2016 12:16PM |
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Quote
Paul Wanamaker
This could easily be a standalone board, but it would be easy enough to include in the firmware of a 32-bit controller.
Re: This engineer claims 100 grams direct extruder. I want one March 21, 2016 01:22PM |
Registered: 11 years ago Posts: 580 |
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Koko76
So what do you intend to do with the sensed position of the filament with this wheel? Is your intention to modulate the XY feed to keep up with the extruder? Or are you intending to modify the feed at the other end of the Bowden based on data from this encoder? Both of those have drawbacks, some significant.
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Koko76
History in this project used a DC motor with encoder for filament extrusion.
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Koko76
Nobody uses this approach anymore, perhaps this is trodden territory?
Re: This engineer claims 100 grams direct extruder. I want one March 21, 2016 02:09PM |
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Re: This engineer claims 100 grams direct extruder. I want one March 21, 2016 02:24PM |
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Re: This engineer claims 100 grams direct extruder. I want one March 21, 2016 03:39PM |
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Re: This engineer claims 100 grams direct extruder. I want one March 21, 2016 04:34PM |
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Re: This engineer claims 100 grams direct extruder. I want one March 22, 2016 01:24AM |
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Re: This engineer claims 100 grams direct extruder. I want one March 22, 2016 05:08AM |
Registered: 13 years ago Posts: 2,470 |
Such a sensor can not differentiate between oval filament or general over- / undersize. You would need to measure from several directions (at least two at 90°) to get a useable result.Quote
The Mechanic
Perhaps I'm missing something, but is there any practical reason that a digital dial indicator couldn't be mounted in line with the bowden tube right after or before the extruder. Most of said indicators output a signal that could be sent the controller to get a reasonably accurate idea of what the diameter is. After that input the length of the bowden tube and distance from indicator to extruder. Coupled with the proposed position sensor, we'd have a good idea of volume and position of the filament at all times.
It seems like the hardest part would be firmware implementation.
Re: This engineer claims 100 grams direct extruder. I want one March 22, 2016 05:33AM |
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Re: This engineer claims 100 grams direct extruder. I want one March 22, 2016 06:22AM |
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Re: This engineer claims 100 grams direct extruder. I want one March 22, 2016 02:36PM |
Registered: 12 years ago Posts: 33 |
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Koko76
Good luck Paul, I believe that you will find "closing the loop" to be more difficult than you think. Modern machine tools still keep servo encoders on the motor shaft instead of the moving table for very good reason, the same one which makes it difficult to close the loop here. Personally I think this is a dead end and I am working to make a lightweight direct solution. I think I can get pretty close to the proposed magic number.
Re: This engineer claims 100 grams direct extruder. I want one March 22, 2016 04:44PM |
Registered: 14 years ago Posts: 268 |
Because moving the encoder further away in the chain from the source of motion makes it far harder to control. As I said in the post you quoted, modern machine tools still put the servo encoder on the motor shaft, not post gearbox, and not on the moving table. A simplified version of what will happen is that the motor will hunt back and forth through the lash present in the system to get to the commanded position. It becomes harder to damp, and the max velocity and acceleration go way down.Quote
jonnycowboy
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Koko76
Good luck Paul, I believe that you will find "closing the loop" to be more difficult than you think. Modern machine tools still keep servo encoders on the motor shaft instead of the moving table for very good reason, the same one which makes it difficult to close the loop here. Personally I think this is a dead end and I am working to make a lightweight direct solution. I think I can get pretty close to the proposed magic number.
Actually why do we care what speed the extruder motor is moving? What we really are interested in is the quantity of filament extruded (or retracted).
Thus:
Why not use a small motor such as the one linked above: similar to stratasys geared maxon motor and instead of an encoder on the motor, just use the mouse sensor to determine filament movement?
Lots of torque, easy to control, and very lightweight.
Re: This engineer claims 100 grams direct extruder. I want one March 22, 2016 05:37PM |
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Re: This engineer claims 100 grams direct extruder. I want one March 22, 2016 08:19PM |
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