Laser Filament Monitor - test results

wilriker

Finally managed to print the sensor housing. It seems that the lazy-me (why should I disassemble my X axis before lubricating it?) got some PTFE on my build plate - perfect for first-layer adhesion. Luckily nothing that gluestick won't overcome.

So, assembly and mounting of the sensor probably tonight.

wilriker

Finally, the first result I can contribute:

Generic Black PLA (the same that is used for the housing):
Duet3D laser filament monitor on endstop input 3, disabled, allowed movement 40% to 120%, check every 3.0mm, current position -7.9, brightness 60, shutter 17, measured minimum 80%, average 87%, maximum 93% over 320.6mm

Housing: @dc42 original, Open Top, 9mm base
PTFE Tubing: Generic 4mm OD 2mm ID (I will probably switch to the included Capricorn when I first switch housing parts.

I am so happy to be part of the test group. As I don't have too many filaments I will probably mainly be concentrating on housing performance.

Also, this gave me a chance to solve a very annoying issue I introduced myself when I added my reverse bowden. It literally took me 15-20 minutes(!) to change filament because the extruder-near end of it was totally in the way and I ended up disassembling the extruder every other time.
The sensor housing now also is my reverse bowden endpoint and is mounted via nuts and screws so I can easily remove it when loading filaments.

EDIT: Also no started a Google Spreadsheet.

fma

Ok, here is my first result. I use David's enclosure, printed in black PLA.

I printed a part with Dailyfil cream white: https://www.filimprimante3d.fr/filament-pla-175-mm/1470-bobine-pla-dailyfil-blanc-creme-175-mm-1kg.html

Duet3D laser filament monitor on endstop input 3, disabled, allowed movement 40% to 140%, check every 3.0mm, current position -10.2, brightness 94, shutter 8, measured minimum 53%, average 93%, maximum 107% over 5764.6mm

fma

Second test with SOVB3D purple PLA: http://www.sovb3d.fr/pla-175mm-standard-500g/90-fil-pla-violet-175mm-500g.html

Duet3D laser filament monitor on endstop input 3, disabled, allowed movement 40% to 140%, check every 3.0mm, current position 2.7, brightness 93, shutter 11, measured minimum 56%, average 84%, maximum 99% over 3425.2mm

dc42

FWIW the shutter reading is an indication of how much of the laser light is returning back to the sensor, which should be mostly determined by how reflective the filament is. High shutter reading = low refectivity.

wilriker

@dc42 I wanted to ask about shutter anyway. What is the range of values and what qualifies as high/low value?
And when we are at that, can you also say something about the brightness value?

dc42

The brightness is the average brightness of IR light received on the sensor. It doesn't usually vary as much as the shutter does, because the sensor appears to adjusts the shutter to try to keep the brightness constant.

kraegar

So to be clear, the ideal situation would be a totally enclosed housing that doesn't reflect any IR back?

dc42

@kraegar said in Laser Filament Monitor - test results:

So to be clear, the ideal situation would be a totally enclosed housing that doesn't reflect any IR back?

Yes, I think so.

kraegar

What wavelength is the IR?

dc42

@kraegar said in Laser Filament Monitor - test results:

What wavelength is the IR?

850nm.

fma

Another result, with Dailyfil Dark gray PLA: https://www.filimprimante3d.fr/filament-pla-175-mm/1479-pla-175mm-dailyfil-gris-fonce-1kg.html

Duet3D laser filament monitor on endstop input 3, disabled, allowed movement 40% to 140%, check every 3.0mm, current position -1.7, brightness 92, shutter 17, measured minimum 89%, average 97%, maximum 109% over
9032.8mm

Soon a result with their blue PLA ("Tardis RAL")...

fma

Dailyfil Dark blue (aka 'Tardis') PLA: https://www.filimprimante3d.fr/filament-pla-175-mm/1483-filament-bleu-fonce-dailyfil-pla-1kg-175-mm.html

Duet3D laser filament monitor on endstop input 3, disabled, allowed movement 40% to 140%, check every 3.0mm, current position -9.5, brightness 94, shutter 17, measured minimum 60%, average 97%, maximum 131% over 15377.6mm

wilriker

I did some more prints with the same configuration as before and added them to my Google Spreadsheet. I also added a new column whether this has been done at night or at day.

Interesting is that contrary to @T3P3Tony's theory I get slightly better results at daytime than at night with just a small light (halogen lamp). It's not much of a difference but consistent.

Unfortunately of the three prints I did today I forgot to take the data from the first one (added M591 D0 to the end codes meanwhile) and the third one was cancelled due to a recurring heater fault on my hotend (temperature rising much slower than the expected 1.8°C/sec). I have to investigate what is happening there first.

T3P3Tony

@wilriker thanks, that is interesting. I do wonder what caused the obvious improvement in the results over time...

Guyaros

Hi all,

Thanks for your feedback.
I designed an improved sensor housing (V2).
I have printed it and tested the sensor fit, but I didn't have time to test the sensor yet.

If anyone wants to print and test this, please go ahead.
I designed this to be a very fast and simple print and should be universally easy to mount because I included top and side holes.

Here is a link to download the STL file:
Laser Filament Sensor Housing - Thingiverse

T3P3Tony

@guyaros thats great, thanks!

fma

As reflections seem to be an issue, I would design an enclosure with a big hole behind the filament, and then try different things. For exemple, il should work fine at night. But it would need something to block the incoming IR during day. Several materials could be tests, then, without changing the enclosure. Maybe the distance could be enough?

T3P3Tony

@fma thats what the option to have the back open in the enclosure is there for in both designs. Also on the one i link from the documentation you can set the hole to be divergent to reduce the reflection. What we are not sure about is how much reflections case and issue. Also @wilriker has had some results that indicate external IR due to daylight may not be much of an issue.

LumberjackEngineering

With regard to external light, the NIR wavelength this sensor is using will get blocked by essentially anything that blocks visible light.
The reflectivity gets a little bit weirder though - if I remember when I get home, I'll try to do some digging. I can say that black probably isn't going to be the best choice as a lot of black pigments can suddenly turn reflective once you get above visible wavelengths.