Magnetic vs Laser filament monitor

Mr Yod · 27 Nov 2018, 13:32

I'm interested in a filament monitor, but the laser sensor has problems with many type of filaments and the magnetic one isn't out yet (I'm currently waiting that the magnetic sensor will be available on the store), so: while waiting wouldn't it be possible and easier to use the laser monitor like some sort of magnetic monitor?
In this way the laser, instead of watching directly the filament, will watch a bearing that rotates thanks to the friction of the filament against it; so, basically, something like this: https://www.thingiverse.com/thing:3223513

This way even the laser filament monitor will be able to see any type of filament.

fma · 27 Nov 2018, 14:36

Did you see this design?

https://www.thingiverse.com/thing:3241561

timcurtis67 · 27 Nov 2018, 16:50

Yeah I saw that one a little while ago. There is an even nicer one that uses a smaller flange bearing. The flange runs against the filament and the sensor watches the flange. I am in the process of designing a housing with the bearing approach to see how it works.

My plan it to use a small o-ring on the bearing that the filament will run against for better grip with less pressure on the bearing and filament. Then have the filament monitor board watch the other side of the flange for motion. I guess they read the stainless steel surface of the bearing pretty well. Time will tell.

brunofporto · 27 Nov 2018, 16:56

@fma said in Magnetic vs Laser filament monitor:

Did you see this design?

https://www.thingiverse.com/thing:3241561

I was going to try that with the Duet3D LFM but was planning to use two bearings!!! A magnet is MUCH better

Thank you for the inspiration

fma · 27 Nov 2018, 17:06

Instead of a simple bearing, I would like to use a MK7 gear. Such like https://www.ebay.fr/itm/Feedstock-Wheel-Extruder-Gear-Drive-RepRap-3D-Printer-1-75mm-Pignon-5mm/182601677691, so there is a good grip. But there are 2 issues:

there is a ratio between the filament move and what the sensor reads; This requires this ratio to be set in the firmware. I think this is not something difficult to do, adding a param to the relevant M-Code.
the screw is on the sensor path

Any idea of a better gear to address the second issue?

timcurtis67 · 27 Nov 2018, 17:37

@fma said in Magnetic vs Laser filament monitor:

Instead of a simple bearing, I would like to use a MK7 gear. Such like https://www.ebay.fr/itm/Feedstock-Wheel-Extruder-Gear-Drive-RepRap-3D-Printer-1-75mm-Pignon-5mm/182601677691, so there is a good grip. But there are 2 issues:

there is a ratio between the filament move and what the sensor reads; This requires this ratio to be set in the firmware. I think this is not something difficult to do, adding a param to the relevant M-Code.

the screw is on the sensor path

Any idea of a better gear to address the second issue?

I'm looking for the path of least resistance in my design. I don't want the drag of a heavy geared hob. I'm not saying it won't work, I believe the more attempts to create different version is better in the long run for everyone.

bot · 27 Nov 2018, 17:57

@timcurtis67 Something like this might be good, too. It's a plain bearing with a silicone or urethane coating of variable hardness and colour. https://us.misumi-ec.com/vona2/detail/110300423960/?CategorySpec=00000030014%3A%3Aa unitType%3A%3A1&Inch=0

timcurtis67 · 27 Nov 2018, 18:03

@bot Yep, that would work as well.

fma · 27 Nov 2018, 18:08

It seems that the detection of the laser sensor is optimized for steal...

bot · 27 Nov 2018, 18:34

Stainless steel, yes. However, we've been trying to get it working with a mix of materials. Having a consistent material that works is all that matters, and that specific product offers a variety of choices (4, really). If none of those work, I suppose you could try a plain bearing, but then you cannot be sure that the bearing is being driven by the filament at all times. Silicone or urethane coating would help with grip, without having a hobbed idler that may damage the filament.

I would personally choose a hobbed gear like a bondtech with a very fine tooth pattern, as to not damage the filament. I suggested the misumi bearings as an alternative to anyone looking to try something else.

Mr Yod · 27 Nov 2018, 18:38

@fma said in Magnetic vs Laser filament monitor:

Did you see this design?

https://www.thingiverse.com/thing:3241561

LOL: it's laser AND magnetic!

It still seems similar with the one I linked (and the others linked in that thingiverse page).
But my question (that I forgot to address in the OP and that bot reminded me) is: is this system with laser sensor on a bearing reliable?

brunofporto · 27 Nov 2018, 18:41

@fma I was going to cover the bearing surface with something.... But I would test it first as bare bearing... As there is nothing to resist the movement.....

timcurtis67 · 27 Nov 2018, 18:41

@mr-yod said in Magnetic vs Laser filament monitor:

@fma said in Magnetic vs Laser filament monitor:

Did you see this design?

https://www.thingiverse.com/thing:3241561

LOL: it's laser AND magnetic!

It still seems similar with the one I linked (and the others linked in that thingiverse page).
But my question (that I forgot to address in the OP and that bot reminded me) is: is this system with laser sensor on a bearing reliable?

I believe it is but we will find out soon enough. There will probably be a few versions built shortly.