Piezo Z probe problems/ Seeking alternatives !!!

CozyP · 22 Dec 2018, 19:33

Dear Duet-ers!

I want to permanently solve the problem with bed leveling. As I have a large glass bed ( 800 x 550 ), autoleveling is essential!!!!

Now, from my previous printer, I have a piezo sensor, which is attached to the nozzle. It has two wires.

I have succesfully connected the sensor to endstop Z input, set endtop Z ACTIVE LOW NC, succesfully homed Z on Zmin with the help of the piezo. However, when I click auto bed mesh, the printer homes Zmin, nozzle and sensor touch the bed, the Z axis ''dives'' succesfully +3mm as I have dictated and I get an instant error
---->Z probe already triggered at start of probing move <----

I also tried connecting the piezo sensor on probe input, connecting +3.3V and GND, while using an normal endtop to home on Z MAX.

Still, I get the same error.

Any solution or alternatives??? Manual leveling is NOT an option, as the tempered glass has many variations throughout its length.
PS. I can't buy another leveling sensor, as most sensors are very inaccurate on glass. I have endstop mechanical sensor and Piezo sensors available.

Thank you for your time

Phaedrux · 22 Dec 2018, 19:37

So are you using it as a probe, or just simple endstop?

Probe type P8 is recommended for the Precision Piezo probe I believe. You may have better luck trying to duplicate their configuration.

https://duet3d.dozuki.com/Wiki/GCode#Section_M558_Set_Z_probe_type

CozyP · 22 Dec 2018, 19:54

I have used as both as an endstop and as a probe. Both times, same results. The weird thing is than when I use the piezo as Zmin endstop, it works perfectly

CozyP · 22 Dec 2018, 19:56

This is my configuration.
It is being turned in P5 program

; Z-Probe
M558 P5 R0.4 H3 F1200 T3600 ; Set Z probe type to effector and the dive height + speeds
G31 P400 X0 Y0 Z0.55 ; Set Z probe trigger value, offset and trigger height
M557 X0:330 Y0:660 S40 ; Define mesh grid

Phaedrux · 22 Dec 2018, 20:32

Try P8 instead of P5.

Are you using G30 to probe the bed when set to zprobe?

CozyP · 22 Dec 2018, 20:48

I don't know. How can I check it out???

I'm gonna try your P8 solution and update...

CozyP · 22 Dec 2018, 21:23

When I switched to P8 program I get:

G29
Error: Z probe already triggered before probing move started

When I switch to P5 :

G32

Error: Z probe already triggered before probing move started

Any help?

Phaedrux · 22 Dec 2018, 21:33

What value does the Zprobe field on the DWC show?

Have you seen this?
https://duet3d.dozuki.com/Wiki/Connecting_a_Z_probe#main
and this?
https://duet3d.dozuki.com/Wiki/ConfiguringRepRapFirmwareCartesianPrinter#Section_Homing_Z_using_a_Z_probe

dc42 · 23 Dec 2018, 08:18

@cozyp said in Piezo Z probe problems/ Seeking alternatives !!!:

I have succesfully connected the sensor to endstop Z input

Connect it to the Z probe input instead. Try P8 and I1 in your M558 command. If you can't get it to trigger, try reversing the polarity.

CozyP · 23 Dec 2018, 14:58

@Phaedrux The Z sensor indicates 1000 on WebControl, if I connect it to Z endstop. If I connect it to Z probe, I get 0. My trigger value is 400 though.
@dc42
I tried connecting the piezo to the Z probe. I changed the preferences from the online configurator to ENDSTOP Z / Z PIEZO/ LOW END. I added both I1 and P8 commands.

I tried to home Z but :

Error: G0/G1: insufficient axes homed.

I changed the polarity, same result.
I think, the piezo doesn't work at all on Z probe input.

PS. This is my Z probe setting
; Z-Probe
M574 Z1 S2 ; Set endstops controlled by probe
M558 P8 I1 R0.4 H3 F1200 T3600 ; Set Z probe type to effector and the dive height + speeds
G31 P400 X0 Y0 Z0.55 ; Set Z probe trigger value, offset and trigger height
M557 X0:330 Y0:660 S40 ; Define mesh grid

CozyP · 23 Dec 2018, 15:02

If this thing ( Piezo ) is not compatible with Duet, is there a solution to mesh bed with a mechanical endstop -temporarly silicon-glued- to my heaterblock, so that I can start printing???

invertmast · 23 Dec 2018, 16:49

@cozyp said in Piezo Z probe problems/ Seeking alternatives !!!:

If this thing ( Piezo ) is not compatible with Duet, is there a solution to mesh bed with a mechanical endstop -temporarly silicon-glued- to my heaterblock, so that I can start printing???

im using the Precision piezo Orion on my Duetwifi with basically zero issues. It is very sensitive to movement. Mine shows a "1000" in the Z-probe box of DWC during nearly all movement of the X/Y carriage's. One thing i did to combat the false "probe already triggered" messages was to put a G4 D2.0 (2 second pause) prior to the Z movement to probe the bed in the Home files.
In my case, the biggest headache I had was having the Bowden tube "bundled" with the wiring going to the hotend carriage. This put enough pressure on the piezo sensor to constantly trigger it. I now have my wiring and bowden cabling separate and haven't had any further problems.

As for the G29 bed mesh probing sequence, i had to turn the acceleration and instantaneous movements for the Z axis down significantly, otherwise just the initial movement of the Z steppers (i have 4) would cause vibrations to run through the machine and cause the piezo to false trigger.
Mine is wired into the Z probe port on the board itself

Here is a copy of my Z-probe config:
; Z-Probe
M574 Z1 S2 ; Set endstops controlled by probe
M558 P8 I1 H2 A4 S0.2 R.5 F100 Z1 ;Z probe switch type, inverted (I1),2mm dive height, 4 probes per point, 0.2mm probing variance, 0.5 second pause, Feed100, Zprobe as switch
G31 X0 Y0 z0.1 P280 ; Set Z probe trigger value, offset and trigger height X, Y, Z offsets, debounce interval
M557 X15:562 Y15:503 S150 ; Define mesh grid

Phaedrux · 23 Dec 2018, 17:02

@cozyp said in Piezo Z probe problems/ Seeking alternatives !!!:

Error: G0/G1: insufficient axes homed.

Can you post your homing files as well.

CozyP · 23 Dec 2018, 17:38

@Phaedrux

I have posted the homeall and homez files. If you need homex and homey let me know!!!
Thank you

; homeall.g
; called to home all axes
;
; generated by RepRapFirmware Configuration Tool v2 on Sun Dec 23 2018 16:45:16 GMT+0200 (Eastern European Standard Time)
G91 ; relative positioning
G1 Z3 F3600 S2 ; lift Z relative to current position
G1 S1 X-365 Y-665 F4200 ; move quickly to X and Y axis endstops and stop there (first pass)
G1 X5 Y5 F3600 ; go back a few mm
G1 S1 X-365 Y-665 F900 ; move slowly to X and Y axis endstops once more (second pass)
G90 ; absolute positioning
G1 X0 Y0 F3600 ; go to first bed probe point and home Z
G30 ; home Z by probing the bed

; Uncomment the following lines to lift Z after probing
;G91 ; relative positioning
;G1 S2 Z3 F60 ; lift Z relative to current position
;G90 ; absolute positioning

; homez.g
; called to home the Z axis
;
; generated by RepRapFirmware Configuration Tool v2 on Sun Dec 23 2018 16:45:16 GMT+0200 (Eastern European Standard Time)
G91 ; relative positioning
G1 Z3 F3600 S2 ; lift Z relative to current position
G90 ; absolute positioning
G1 X0 Y0 F3600 ; go to first probe point
G30 ; home Z by probing the bed

; Uncomment the following lines to lift Z after probing
;G91 ; relative positioning
;G1 S2 Z3 F60 ; lift Z relative to current position
;G90 ; absolute positioning

Phaedrux · 23 Dec 2018, 17:41

@cozyp said in Piezo Z probe problems/ Seeking alternatives !!!:

G1 X0 Y0 F3600 ; go to first bed probe point and home Z
G30 ; home Z by probing the bed

Is 0,0 really where you want to probe the bed?

G31 P400 X0 Y0 Z0.55

Is Z0.55 a measured trigger height value? It's normal for nozzle contact probes to require negative values since they push into the bed and compress the springs, etc a bit before triggering.

CozyP · 23 Dec 2018, 17:51

@phaedrux Z0.55 is the real difference between nozzle and glass with the help of the piezo.
If I home Z and remove the piezo, there is a gap between nozzle and bed, so I added +0.55 as an offset to position the nozzle exactly on bed surface.

Also, beware that this piezo DOES NOT have springs, it's a simple film attached to the nozzle

Phaedrux · 23 Dec 2018, 17:56

Your trigger height should be a measured using this procedure: https://duet3d.dozuki.com/Wiki/Test_and_calibrate_the_Z_probe#Section_Calibrate_the_Z_probe_trigger_height

CozyP · 23 Dec 2018, 17:57

gimme 5' to try that asap and provide you an update.
Thanks

CozyP · 23 Dec 2018, 18:04

G30 S-1
Error: Z probe already triggered at start of probing move.

Also, the machine continuously crashes to X axis endstop for 1 sec.....

Phaedrux · 23 Dec 2018, 18:05

Is that when doing homeall?