Black printbite and IR Sensor - very inconsistent heights?

RGN01

The applicable line in config.g is:
[c]G31 P500 X9 Y21 Z2.26 ; Set Z probe trigger value, offset and trigger height[/c]

The 2.26mm was set using the method on this page https://miscsolutions.wordpress.com/mini-height-sensor-board/

Richard

dc42

How much higher is the edge of the senzor board than the nozzle? What I am after is the height of the sensor board above the bed when it triggers, which will be somewhat greater than 2.26mm.

RGN01

Oh, I see, sorry. The bottom edge of the board is about 3.25 - 3.3mm above the PrintBite (it is difficult to measure so used a taper and measured that afterwards).

What should it be?

Richard

RGN01

The height measured with G30 S-1 is repeatable when measured in the same spot. These are readings from one location:
2.382
2.380
2.382
2.385
2.385
2.385
2.380
2.382
2.382
2.382
2.382
2.382
2.380
2.378
2.380
2.380

Moving the nozzle by X=10mm and I get the same level of repeatability but around 2.200mm. Another 10mm across and it is back to 2.380

I turned the bed compensation off to test this.

Richard

RGN01

Thanks, swoozle, but that seems to be related to the clear / white PrintBite as it talks about grid lines. The black that I have does not have those lines. I'm thinking of changing to an inductive sensor if I can't get this right.

I'd use the piezo but I don't know how I'd connect it to my x-carriage or bed - neither was designed for that.

Richard

Dougal1957

can you lower your IR Sensor by about 1 mm in relation to the nozzle?

I think the recommended distance is between 1 and 2 mm but it is a while since I used one

RGN01

Yes, I could try that but I don't have much height to play with. The dimension I quoted to David is the height of the bottom of the sensor board above the PrintBite when the sensor triggers - 3.3mm approximately. At that point the nozzle is 2.26mm above the PrintBite so the height difference is close to the recommended 1.5mm - actually a bit lower than recommended but it never fouled a print on the previous print surface (PEI on a black PCB heatbed).

Now that I've made the change to aluminium plate and added the PrintBite I'm beginning to wonder if that inductive proximity sensor isn't my best bet. Either that or a BL Touch, perhaps.

Richard

RGN01

I've just used Blu-Tack to mount an inductive sensor under my carriage and tested that manually by monitoring the LED on it as I lowered the nozzle. Even like that it is repeatable to less than 0.01mm and the peaks and valleys seem to have gone.

I just need to figure out how to wire it up (I'm already using an NPN inductive sensor on Z-max as my Z-home and only want this one for Z-probe, not homing.

Richard

dc42

I'll ask Jason again for a sample of matt black PrintBite to test the IR sensor with.

RGN01

Thanks, David.

It does seem to be something to do with the interaction between the PrintBite and the IR sensor. I'm busy printing a mount for the inductive sensor and will try that later.

Is it possible to connect the NPN inductive sensor yo the Z-probe input of the Duet WiFi through a Schottky diode? Is it the Z-Probe_In pin that I connect to the diode and the sensor and then just set it as a switch input?

Thanks.

Richard

dc42

@RGN01:

Is it possible to connect the NPN inductive sensor yo the Z-probe input of the Duet WiFi through a Schottky diode? Is it the Z-Probe_In pin that I connect to the diode and the sensor and then just set it as a switch input?

Yes, see the wiki. If you use the Z probe input then an ordinary small signal silicon diode will probably work too if you don't have a Schottky one.

Mutley

Hi Richard, Generally it has been positive feedback with the IR sensor on the black (matte) PB. Dave will have some to test early in the week. Possibly a silly question but any surface imperfections or scratches on the PB that might be distorting the readings?
J

RGN01

Thanks, I found the new one (the format is growing on me) and got it sorted. The applicable lines in config.g are as follows:

[c]; IR Z-probe
M558 P1 H4 F250 T2000 ; Set Z probe type to unmodulated and the dive height + speeds
G31 P500 X9 Y21 Z2.26 ; Set Z probe trigger value, offset and trigger height

; Inductive Sensor
M558 I1 P5 H4 F250 T2000 ; Set Z probe type to digital and the dive height + speeds (I1 = invert signal)
G31 X9 Y21 Z2.26 ; Set Z probe trigger value, offset and trigger height
[/c]

I'm constantly amazed at the ease of changing things with the Duet!

Richard

(edited to fix typos)

dc42

@RGN01:

T
I'm constantly amazed at the ease of changing things with the Duet!

"One firmware binary to rule them all" (all Duets that is) - with apologies to JRR Tolkien.

Seriously, we want you to be able to change ANYTHING that isn't a 1-off requirement by sending the appropriate GCode, either in config.g or live from DWC or USB. I even have a macro for homing my Cartesian printer and then turning it into a pretend CoreXY printer for firmware testing.

In the unlikely event that your requirement is a 1-off (e.g. the user who recently needed to add a 13th stepper driver), RepRapFirmware is open source so you have the freedom to modify it - and it will stay that way.

RGN01

To close this out - I'm now using a TL-W5MC1 inductive proximity sensor and am getting repeatability of about 0.002mm and the PrintBite is showing as flat to all intents and purposes.

I'm adjusting a few things to now get it level but one step closer and that sensor works well - especially at the price! https://www.ebay.co.uk/itm/5mm-Noncontact-Inductive-Proximity-Sensor-Switch-Detect-DC-6-36V-NPN-TL-W5MC1-/253114333447

Richard

rkrammes

My results with the matt white Printbite+ with a grid. I purchased my sensor more than a year ago and it is not a surface mount board. Would it be worthwhile to put some electrical tape in the corners and define points there for probing? I really like both this sensor and Printbite but if one has to go unfortunately it will be the sensor.

GeckoBox3D

@dc42:

I'll ask Jason again for a sample of matt black PrintBite to test the IR sensor with.

Any update on this? I've been waiting to see someone's results for a while as my old gridded printbite gives horrendous IR probe results

dc42

I've just chased for samples again.

JohnOCFII

@dc42 Any chance yet to re-test the IR sensor with PrintBIte?

dc42

Thanks for the reminder, I've chased again for a sample.