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TMC2130 stallguard2 as touch probe?

Posted by firefly555 
TMC2130 stallguard2 as touch probe?
December 09, 2017 05:48PM
Does anyone know just how much force is required to kick in stallguard2 on the TMC2130's? If the force is something that's "safe" for the nozzle to tap on the bed, why not wire up the steppers to act as a touch-probe? I found an old reference to this but it wasn't really fully answered:

[github.com]
Re: TMC2130 stallguard2 as touch probe?
December 09, 2017 11:51PM
I believe dc42 is busy developing such an endstop replacement strategy. The key is to reduce stepper current while homing to reduce forces when the carrier bumps into the frame. If it is precise enough to be used as z-probe is the question.
Re: TMC2130 stallguard2 as touch probe?
December 10, 2017 05:58AM
Sensorless homing is already working on delta printers using the built-in TMC2660 drivers on Duet WiFi/Duet Ethernet electronics. The homing is only accurate to +/- 1 full step at best, however a single round of auto calibration taking about 20 seconds will correct for that inaccuracy. Of course, you need a Z probe for that. See [duet3d.com] for the details.

Stall detection is not a substitute for a Z probe because the resolution is not sufficient.


Delta printer calibration calculator, mini IR Z probe, and colour touch screen control panel: [escher3d.com]

Large delta printer, and other 3D printer blog postings: [miscsolutions.wordpress.com]

Disclosure: I have a financial interest in sales of the Panel Due, Mini IR height sensor, and Duet WiFi/Duet Ethernet [www.duet3d.com].
Re: TMC2130 stallguard2 as touch probe?
December 20, 2017 02:27PM
It seems that there is a challenge inherent in this, low inductance stepper motors are recommended for better high speed performance with 24v and on a delta if you don't want to go at least a little fast, why build a delta? But high inductance motors trigger stallguard 2 more reliably ie offer a bigger tuning window so you get more reliable detection.

I plan to try it on my next machine which I want to be as experimental as possible, specifying medium inductance motors, I'll home the towers with low motor current set in my homedelta.g file against hard stops,using stall guard.


[www.precisionpiezo.co.uk] Accurate, repeatable, versatile z-probe plus piezo discs, endstop cables, pt100, 50w heaters.
[www.facebook.com] we want to see your first layer photos... give us a like/share
[www.thingiverse.com] DemonDeltaMicro - Micro Delta Printer & Things I've made/remixed.
Re: TMC2130 stallguard2 as touch probe?
December 20, 2017 03:04PM
Stall detection for sensorless homing isn't difficult, because you can choose the homing speed to be in the optimal range for stall detection, and you can also reduce the motor current during homing. The motors on my delta are rated at 1.68A and have about 4mH inductance. It wasn't difficult to find suitable stall detection parameters.


Delta printer calibration calculator, mini IR Z probe, and colour touch screen control panel: [escher3d.com]

Large delta printer, and other 3D printer blog postings: [miscsolutions.wordpress.com]

Disclosure: I have a financial interest in sales of the Panel Due, Mini IR height sensor, and Duet WiFi/Duet Ethernet [www.duet3d.com].
Re: TMC2130 stallguard2 as touch probe?
December 20, 2017 03:05PM
Encouraging. Thank you I use those same motors currently.


[www.precisionpiezo.co.uk] Accurate, repeatable, versatile z-probe plus piezo discs, endstop cables, pt100, 50w heaters.
[www.facebook.com] we want to see your first layer photos... give us a like/share
[www.thingiverse.com] DemonDeltaMicro - Micro Delta Printer & Things I've made/remixed.
Re: TMC2130 stallguard2 as touch probe?
December 20, 2017 11:02PM
I tried stall detection on my compact carrier Delta with 1.7A steppers. At first I couldn't find a setting that homes well and later doesn't spit out tons of stall warnings.
I had to modify the homeDelta.g file and add a M915 line in the end to reduce sensitivity and switch filter on. Now it works reliable.

The sensitivity window is pretty small: I had a lucky punch with S5, but then tried S6 and S4 and both failed.
Re: TMC2130 stallguard2 as touch probe?
December 20, 2017 11:43PM
Quote
o_lampe
I tried stall detection on my compact carrier Delta with 1.7A steppers. At first I couldn't find a setting that homes well and later doesn't spit out tons of stall warnings.
I had to modify the homeDelta.g file and add a M915 line in the end to reduce sensitivity and switch filter on. Now it works reliable.

The sensitivity window is pretty small: I had a lucky punch with S5, but then tried S6 and S4 and both failed.

Increasing the minimum speed for stall detection (M915 H parameter) widens the window, but then of course there is a greater risk of missing stalls at low printing speeds.


Delta printer calibration calculator, mini IR Z probe, and colour touch screen control panel: [escher3d.com]

Large delta printer, and other 3D printer blog postings: [miscsolutions.wordpress.com]

Disclosure: I have a financial interest in sales of the Panel Due, Mini IR height sensor, and Duet WiFi/Duet Ethernet [www.duet3d.com].
Re: TMC2130 stallguard2 as touch probe?
December 21, 2017 08:25PM
Quote
dc42
Quote
o_lampe
I tried stall detection on my compact carrier Delta with 1.7A steppers. At first I couldn't find a setting that homes well and later doesn't spit out tons of stall warnings.
I had to modify the homeDelta.g file and add a M915 line in the end to reduce sensitivity and switch filter on. Now it works reliable.

The sensitivity window is pretty small: I had a lucky punch with S5, but then tried S6 and S4 and both failed.

Increasing the minimum speed for stall detection (M915 H parameter) widens the window, but then of course there is a greater risk of missing stalls at low printing speeds.

Maybe there can be multiple settings depending on how detection needs to work: endstop, bed-level, and obstruction. The sensitivity can be set as needed during the different operations.
Re: TMC2130 stallguard2 as touch probe?
December 21, 2017 11:56PM
Quote

The sensitivity can be set as needed during the different operations.

I tried to set sensitivity while I got so many warnings reported, but sending M915 Sxxx didn't work. I guess, I have to send M915 X Y Z Sxxx instead?
Or would that cause the other parameters to fall back to their default values?
Re: TMC2130 stallguard2 as touch probe?
December 22, 2017 12:17AM
Quote
o_lampe
Quote

The sensitivity can be set as needed during the different operations.

I tried to set sensitivity while I got so many warnings reported, but sending M915 Sxxx didn't work. I guess, I have to send M915 X Y Z Sxxx instead?
Or would that cause the other parameters to fall back to their default values?

You must always provide either axis names or driver numbers in the M915 command so that the firmware knows which motors you are talking about. You can use different parameters for each motor.


Delta printer calibration calculator, mini IR Z probe, and colour touch screen control panel: [escher3d.com]

Large delta printer, and other 3D printer blog postings: [miscsolutions.wordpress.com]

Disclosure: I have a financial interest in sales of the Panel Due, Mini IR height sensor, and Duet WiFi/Duet Ethernet [www.duet3d.com].
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