Laser filament monitor
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@phaedrux Thanks for the info. I wondered if a plain switch with no resisters anywhere could damage the Duet. Perhaps the inputs on the Duet are well protected and debounced?
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@3dmntbighker said in Laser filament monitor:
@phaedrux Thanks for the info. I wondered if a plain switch with no resisters anywhere could damage the Duet. Perhaps the inputs on the Duet are well protected and debounced?
Yes, the endstop inputs are.
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sorry for the delays. An update on testing is here:
https://forum.duet3d.com/topic/6092/laser-filament-monitor-test-results
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Hi to everyone who is beta testing this sensor. I built upon the geometry for the housing, and modified it so that the PTFE tube can't be pulled out , and also it is split-able so that you can remove the remnant filament after the tail end has been fed past the hob gear.
Video explaining it here: https://youtu.be/RmZ7aJYvWLc?t=7m40s
.stl file here: https://www.myminifactory.com/object/3d-print-splitable-duet-laser-filament-bracket-for-bowden-tube-printers-73781
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@punamenon That's a clever design. Nice work. Love the videos too.
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@punamenon said in Laser filament monitor:
Hi to everyone who is beta testing this sensor. I built upon the geometry for the housing, and modified it so that the PTFE tube can't be pulled out , and also it is split-able so that you can remove the remnant filament after the tail end has been fed past the hob gear.
I'm a bit confused about having the sensor after the extruder. So you are relying solely on filament movement detection for both jams and out of filament conditions? Obviously once the hob stops pushing you will always still have filament present in the sensor. Just no movement. Mine is direct drive so this is purely my curiosity. I want a QuadFusion CMYK head eventually, so my filament detection will be a whole different worm can.
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@3dmntbighker said in Laser filament monitor:
@punamenon said in Laser filament monitor:
Hi to everyone who is beta testing this sensor. I built upon the geometry for the housing, and modified it so that the PTFE tube can't be pulled out , and also it is split-able so that you can remove the remnant filament after the tail end has been fed past the hob gear.
I'm a bit confused about having the sensor after the extruder. So you are relying solely on filament movement detection for both jams and out of filament conditions? Obviously once the hob stops pushing you will always still have filament present in the sensor. Just no movement. Mine is direct drive so this is purely my curiosity. I want a QuadFusion CMYK head eventually, so my filament detection will be a whole different worm can.
I would install it after the extruder too so it can read the texture made by the hob gear even with difficult to read materials.
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One disadvantage of installing the filament monitor after the extruder drive is that there is an increased risk of filament dust contaminating the image sensor, especially after there has been a jam and some filament had been ground up.
Duet WiFi hardware designer and firmware engineer
Please do not ask me for Duet support via PM or email, use the forum
http://www.escher3d.com, https://miscsolutions.wordpress.com -
@dc42 said in Laser filament monitor:
One disadvantage of installing the filament monitor after the extruder drive is that there is an increased risk of filament dust contaminating the image sensor, especially after there has been a jam and some filament had been ground up.
A good point! What about a redesign so that when you split it apart, you can access the sensor with a cotton swab? Would repeated wiping damage the sensor?
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@dc42 That is is true.....
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@dc42 said in Laser filament monitor:
Today I've been trying out a laser optical sensor to see if it is accurate enough to use instead of the rotating magnet sensor we use in the beta test filament monitors. The good new is that in tests with several different filaments including black and transparent, first indications are that it works adequately, provided that the filament position is sufficiently well constrained. So we will go ahead with making prototypes. We may have a very small number (between 2 and 4) available for beta testers
This does however mean that production of filament monitors to the existing design is on hold until the prototypes are ready and tested, so that we can make an informed decision on which design to use.
The laser filament monitor would have a much simpler housing design. Basically it just needs to clamp PTFE tubes on the inlet and the outlet, to ensure that the filament is constrained to be in the centre of the field of view of the sensor.
Is the filament monitor available for purchase?
Thanks.
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@celulari not yet
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Just ordered my duet this morning for an idex printer build. Definitely interested in a filament laser sensor, if there are spots for any more beta testers in the future. I would also like to put forward a design for a different type of filament sensor, using not lasers, nor ultra sound, but an electric motor. Would it be possible to mount a very small electric motor, and a wheel to rub up against the filament, and then read the voltage output? Surely if this was done correctly, it would allow you to read everything necessary, with no calibration required. Again, I'm just thinking, and haven't done any testing, but in principle, a zero voltage reading would indicate either a jam or that the printer has run out of filament, a sudden dip in the voltage would indicate grinding, and the overall voltage could be used to monitor the flow rate. It does occur to me for better accuracy, more than one motor would be ideal, but I don't see why this would be such a problem. The only other issue I can identify is that this sensor would be very large compared laser sensors, and therefore harder to install in a printer.
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@brunofporto I had seen they had made something similar, though I also saw earlier in the post that it was susceptible to dust, and I presumed this was to do with the sensor. Surely monitoring voltage output by a motor would be simpler? I have no clue whether there is any way of reading a dc voltage input however. I simply had this idea because I was looking at anemometers for the raspberry pi, and saw one that worked in this same way. As far as I can recall, a motor's rpm has a linear relationship with voltage put in. Presumably the inverse is true for the voltage output, with the rpm put in.
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@robobobob The issue is not the type of signal, IMO, but the mechanical reading of the movement itself.
Filaments can slip the wheel, the reading may vary based to the spring compression of the reading wheel relative to the hardness of the material, the mechanical sensor adds drag that can influence the reading, etc.. Also the casing design, quality of bearings, type of hob wheel, etc may vary if the end clients are the builders of the mechanical part of the system. And it will be much more expensive if they sell the bundle.
Optical movement sensors are widely used ( i.e. your mouse) even in industry to feedback motion. They are cheap and precise enough. And they do the job without touching the material (at least the sensor
) So they are very good candidates for this job.With enough data from the beta testers they can fine tune the sensor for a wide range of materials and learn the behavior of the sensor to fine tune it.
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hi,
sorry but i have not read all post, its a long post...
One question
The filament monitor. Detect when run out of filament only? or too detect when filament, for a jam, not its extruded?
thanks
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@peirof Yes it will detect a jam and under extrusion as well I believe.
