Laser Filament Monitor - test results

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.

Guyaros

@fma In my sensor housing design, the sensor window can be completely closed using M4 screw.
Its also make it easy to check if the IR from the surrounding is interfering with the sensor.

dc42

Has anyone tried my earlier suggestion of a closure that is cone shaped on the inside?

wilriker

Something related to the guide at dozuki: It states that one should use M3x16 screws and nyloc nuts. I am using the open top (which is still thinner than the closed top) and the 9mm base and I could barely screw regular nuts on M3x20 screws. I could of course have used nyloc nuts but the threads of the screw would not have gone deep enough into the nut to make it to the nylon ring. I am using nylon washers underneath the nuts though. But anyway M3x16 would not have even protruded from the housing in my case.

T3P3Tony

@wilriker Thanks updated

@dc42 The housing design I shared has a divergent light path where the amount it diverges can be edited. Its has a square rather than round profile though.

wilriker

@t3p3tony said in Laser Filament Monitor - test results:

@wilriker Thanks updated

Do updates in dozuki pages take a while? I cannot see any difference.

wilriker

@t3p3tony said in Laser Filament Monitor - test results:

@dc42 The housing design I shared has a divergent light path where the amount it diverges can be edited. Its has a square rather than round profile though.

@dc42 Also in what direction is that cone/divergence supposed to be according to your suggestion (that I apparently missed and cannot find either)? Tip towards the sensor or away from the sensor?

EDIT: Of course if it is tip towards the sensor it would not make sense to have full cone since it would block the sensor. In that case I would assume a cone with the top chopped off.

T3P3Tony

@wilriker have a look at this:

Having a divergent light path to reduce stray reflections back to the sensor might help, See the "divergeAmount" variable in the OpenSCAD design on youmagine.

From the documentation

wilriker

@t3p3tony Now I am confused

I thought your "Thanks updated" was related to me reporting that I found the screw lengths given in the documentation to be too short.

Re: housing: I already have your scad file on my hard drive and looked into it. My question on the direction of the cone that @dc42 suggested was that it could be he meant to have the base of the cone starting at the sensor going into its tip in direction of the top housing part so that in the end it looks like the top housing has some kind of spike. I would assume that this is to keep the light deflecting internally in various directions until it is too faint to detected by the sensor anymore. But that is just an assumption.