Laser Filament Monitor - test results

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.

dc42

@wilriker said in Laser Filament Monitor - test results:

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.

Yes, that is what I intended.

wilriker

@dc42 said in Laser Filament Monitor - test results:

Yes, that is what I intended.

So I came up with
Top View:

Bottom View:

Sorry for those screen-caps, my OpenSCAD only produces fully-black PNG files when trying to export the design as an image.

deckingman

@wilriker said in Laser Filament Monitor - test results:

Sorry for those screen-caps, my OpenSCAD only produces fully-black PNG files when trying to export the design as an image.

I think the png background colour gets inherited from the preferences you set for 3d view. So "Edit - Preferences - 3D view" then select a different colour scheme. I'm pretty sure that you can also create custom colour schemes but it means digging into code - not my field of expertise but I'm sure you could make the changes. As ever, Google is your friend.

wilriker

@deckingman OK, I can see that the background color gets inherited from the theme. But why is then everything black on export? Even the blue-ish rendered parts?

Anyway, changing the theme helps. I found though that the export does not do anything really different from a screen capture. So no use in doing it that way.

deckingman

@wilriker said in Laser Filament Monitor - test results:

@deckingman OK, I can see that the background color gets inherited from the theme. But why is then everything black on export? Even the blue-ish rendered parts?

Don't ask me - I'm just an old guy who cuts a screws bits of wood together .

wilriker

@deckingman said in Laser Filament Monitor - test results:

Don't ask me - I'm just an old guy who cuts a screws bits of wood together .

Don't forget the guy that gives great advise on how to also screw aluminum extrusions together.

wilriker

So, I added some more results to my Spreadsheet and they line up with the previous results pretty good which means that for the same conditions, e.g. filament, housing and settings the sensor will perform quite stable.

Probably tonight or maybe tomorrow night I can switch the housing to one having a cone-shaped interior as @dc42 suggested - took me some tries to design it in a way to be actually printable. I will then do some more prints with the current filament to see if the redesigned housing performs better or worse before switching filament.

T3P3Tony

@wilriker thanks for the update. So from those results you could probably be comfortable having the filament sensor error outside 40%-120% which over 3mm mean it would under read by 1.8mm before having an error - that is short enough to save some prints, but not all, depending on how big the object is, layer height etc.

fma

Did someone try to reduce/increase the check length (default to 3mm)? Could it improve things?

T3P3Tony

@fma I did a lot of testing with 1mm earlier on, this increased the % range of min and max, which is to be expected as there is less difference to average over and some time maybe that 1mm is all during a fast retract or something. On the other hand if you have 20%-140% of 1mm then the maximum underextrusion before an alarm is only 0.8mm so worth testing and tuning for specific filaments, retract lengths etc.

fma

Ok, I see. Thanks.

wilriker

@t3p3tony Based on my current results and as stable as they are I would even be comfortable to set the limits to a narrower range of 65-105%. I will add this to my filament's config.g but still with S0 as long as I continue testing.

EDIT: Regarding check length: would it make sense to synchronize this somehow with retraction distance? On my MK8 direct extruder I use a rather unusual 3.5mm retraction length which is quite close to 3mm check length.

wilriker

I switched now to a cone shaped interior. First print with it might be tomorrow or the day after.

But when I removed the PCB from the housing I took a look at the sensor itself and it seems to have some kind of dirt on the shiny part. It is hart to spot or to explain. What would be the best way to clean it? My intuitive approach would be to deal with it like with my camera lenses that have sensitive coatings on it and therefore need careful cleaning with just cigarette paper (the softest paper available) and Isopropyl alcohol. But I am open to suggestions.

Mounted in its new housing it just happily blinks now... green - red - green - red - green - red...

EDIT: And yes I read and adhered to

Take great care not to damage [the sensor] or to touch it. Do not put the filament monitor PCB component-side down on any surface.

dc42

I used cotton buds and isopropyl alcohol to clean the image sensor. AFAIR this is close to what the manufacturer recommends.

wilriker

@dc42 Thanks, will do it like that then.

dc42

PS - the manufacturer says you must not squirt alcohol on the image sensor because it could get inside. So moisten the cotton bud with alcohol and then use it to gently wipe the sensor.

wilriker

@dc42 said in Laser Filament Monitor - test results:

PS - the manufacturer says you must not squirt alcohol on the image sensor because it could get inside. So moisten the cotton bud with alcohol and then use it to gently wipe the sensor.

Did it like that. Sensor seems to be clean now. I have not printed anything yet but the status gives a lower brightness than before. No idea if that is somehow related.

Also did a first print with the internally cone shaped housing and the results are worse than with the default square window and open top. Not much worse but measurable. See my Google Spreadsheet for details.

wilriker

And a second print with the cone-housing. Again slightly worse than the straight square open-window version.

I printed @T3P3Tony's housing with divergence today but when I tried to mount it I noticed that it does not fit. Has there been a rearrangement on the PCB at some point in time? Because the window for the sensor is much to far down. I took a photo with mounting holes aligned because they fit:
housing comparison

Left is Tony's design, right is my cone-shaped based on @dc42's version on Thingiverse.