Duet magnetic filament monitor adventures

[soare0]

One of the things I needed, and because I decided to refurbish my printer (other than junky-closed-bugy electronics/firmware), was the lack of a magnetic sensor support.
I mean, in fact they (DoWell) had the possibility to use such a sensor on their cheap 32 bit board, but they did not mount such, because of the problems... you all know.

Long story short, I ordered the sensor from DUET, fortunately and unwillingly without its case (maybe this was a new version though?), so downloaded and printed LO-FI new enclosure.

I had great hopes, before reading the forums. Not so great, after some reading.
And... of course, it did not work.

Thing no. 0: do yourself a favour: print it in resin. I was very lazy, and also, I do not use my resin printer (albeit sometimes I should do), so I did it in ABS, 0.1mm height, 0.4mm width, 60mm/sec, on a raft. The raft was needed, because only a real hero would do such a print otherwise, on a 600x600x800, wich have 0.35mm on the height map (fine tuned, that is...). The smaller printers are garbage now, so, again, if one have such a printer and not being lazy, resin is recommended.

Oh, I would even buy some enclosures, well printed

Thing no. 1: the board was too close to the magnet. So needed to mount some washers for this. Message was: magnet too strong.
Right.
Then, amazingly, with some washers under the board, it worked. Somewhat.
I tried a complex printing, with many travels (even if short). So many errors, and please note that retractions were set low, 0.4mm, as I have a direct extruder.
Because of this, I then used some ... unreasonable settings: m591 d0 r30:200 e10.0
Why?
Because:

m591 d0

Duet3D rotating magnet filament monitor v4 on pin 1.io1.in, enabled, sensitivity 28.80mm/rev, allow 30% to 200%, check printing moves every 10.0mm, version 4, mag 131 agc 85, measured sensitivity 26.24mm/rev, min 36% max 109% over 649.0mm

I assumed that somehow, there are issues correlating what is happening there, especially with so many retractions (albeit low) and travels (albeit short).

I am not interested in filament skipping sensing, but in total throat blockages, because of sh.ty filaments. When you print 3-4 days in a row, such events are ruining your ... life.
Things worked well for an hour, or so, as in the beginning, it worked maybe for 30 seconds, with r60:160.

Then, the problems begun again.

This would be Thing no.2.1.

This time I tracked down to a mechanical issue: the magnetic rod had some movement along its axis, so the magnetic field strength, fluctuated, so... etc.
The problem was again solved, pressing a little on the center of the ... rotating piece (name it... your way please...), I mean in the hole of the body of the enclosure.

And yes, this was with my middle finger, the only one available in that position.

The sensor performed flawlessly in this time, but as I tested an ABS print, I preffered to sort this later, the test being concludent to me.

My point: the firmware works well, I mean for the board and for the sensor too. The problems are hidden in the mechanical assembly: it must be redesigned, to be immune to such stuff. For now, it is not. Maybe a bulky infrared rotary gap would solve the problem.

Or maybe I just moved too much, at some ... limit, the board from the magnet.

This would be Thing no.2.2.

As the first washers were 0.5-0.6mm, I put on some 0.3mm washers, and for now, it seemed to work.

This would be Thing no.2.3.

However, there was another issue, mechanical too: the sensor worked well only in a certain position. When rotating 90 dgr, clockwise, stopped working right. I assumed that maybe I inserted the PTFE tube too much, and I pulled it very little, I would say (during printing, again), unnoticeable.
It works now in both positions.

This is why many of us (ok, maybe not so many) love Tinkerbell (besides she has a very green and very short dress): she tinker until stuff works.

However, for an industrial design, I would say that rev. 5 (ish?) of this sensor would be needed.

And definitely threaded PTFE inserts, M5, or 1/8”, for pneumatics, or such. I even failed to understand how the... provided stuff works (the black ones): I just assumed one needs to push hard, and indeed, it was so, but I am used to pneumatics fittings, so...

For now, after:

m591 d0 r10:200 e10.0

is printing right.

And interogating:

Duet3D rotating magnet filament monitor v4 on pin 1.io1.in, enabled, sensitivity 28.80mm/rev, allow 10% to 200%, check printing moves every 10.0mm, version 4, mag 132 agc 58, measured sensitivity 24.87mm/rev, min 62% max 103% over 2219.0mm

You may find a very good ideea to use such ... relaxed interval, like 10-200%, at least until you know where you are situated with your printing/s.