After Z probing, print head smashing into bed

Phaedrux

Can you share your homing files and bed.g and any other macros you're using for leveling?

What firmware version?

@Adam_Sw3 said in After Z probing, print head smashing into bed:

M92 X80.00 Y80.00 Z1066.67

How did you determine those steps per mm for Z? It seems a strange value.

For a leadscrew z axis the formula for steps per mm is as follows.

Z_steps_per_mm = (motor_steps_per_rev * driver_microstep) / screw_lead

Adam_Sw3

@Phaedrux hello Phaedrux! yes certainly, i will supply these in the morning (GMT 08:00) i will share these. I got these z steps per mm using the prusa calculator. I am using this Lead screw https://uk.rs-online.com/web/p/lead-screws/8625281?gb=s i also checked with verniers ie down 25mm etc.

Thank you.

fcwilt

@Adam_Sw3 said in After Z probing, print head smashing into bed:

@fcwilt Would increasing my Z offset bring it further away from the bed and then from there, i could baby step it down onto the bed? Or would it be the inverse (decreasing Z offset)

That would be putting a bandage on the symptoms and hiding the real problem.

Hang in there - we will sort it.

Frederick

Adam_Sw3

@Phaedrux

Hi Phaedrux, my bed.g is here

; bed.g
; called to perform automatic bed compensation via G32
;
; generated by RepRapFirmware Configuration Tool v3.3.14 on Sat Oct 29 2022 18:08:10 GMT+0100 (British Summer Time)
G28 ; home

G30 P0 X0 Y440 Z-99999 ; probe near a leadscrew
G30 P1 X570 Y440 Z-99999 ; probe near a leadscrew
G30 P2 X290 Y10 Z-99999 S3 ; probe near a leadscrew and calibrate 3 motors




;M561 ; clear any bed transform
;G29  ; probe the bed and enable compensation

Home all

; homeall.g
; called to home all axes
;
; generated by RepRapFirmware Configuration Tool v3.3.14 on Sat Oct 29 2022 18:08:10 GMT+0100 (British Summer Time)
G91                     ; relative positioning
G1 H2 Z5 F6000          ; lift Z relative to current position
G1 H1 X-555 Y-415 F1800 ; move quickly to X or Y endstop and stop there (first pass)
G1 H1 X-555             ; home X axis
G1 H1 Y-415             ; home Y axis
G1 X5 Y5 F6000          ; go back a few mm
G1 H1 X-555 F360        ; move slowly to X axis endstop once more (second pass)
G1 H1 Y-415             ; then move slowly to Y axis endstop
G90                     ; absolute positioning
G1 X-20 Y10 F6000       ; 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 Z5 F100             ; lift Z relative to current position
;G90                    ; absolute positioning

Home X

; homex.g
; called to home the X axis
;
; generated by RepRapFirmware Configuration Tool v3.3.14 on Sat Oct 29 2022 18:08:10 GMT+0100 (British Summer Time)
G91               ; relative positioning
G1 H2 Z5 F6000    ; lift Z relative to current position
G1 H1 X-555 F1800 ; move quickly to X axis endstop and stop there (first pass)
G1 X5 F6000       ; go back a few mm
G1 H1 X-555 F360  ; move slowly to X axis endstop once more (second pass)
G1 H2 Z-5 F6000   ; lower Z again
G90               ; absolute positioning

Home Y

; homey.g
; called to home the Y axis
;
; generated by RepRapFirmware Configuration Tool v3.3.14 on Sat Oct 29 2022 18:08:10 GMT+0100 (British Summer Time)
G91               ; relative positioning
G1 H2 Z5 F6000    ; lift Z relative to current position
G1 H1 Y-415 F1800 ; move quickly to Y axis endstop and stop there (first pass)
G1 Y5 F6000       ; go back a few mm
G1 H1 Y-415 F360  ; move slowly to Y axis endstop once more (second pass)
G1 H2 Z-5 F6000   ; lower Z again
G90               ; absolute positioning

Home Z

; homez.g
; called to home the Z axis
;
; generated by RepRapFirmware Configuration Tool v3.3.14 on Sat Oct 29 2022 18:08:10 GMT+0100 (British Summer Time)
G91               ; relative positioning
G1 H2 Z5 F6000    ; lift Z relative to current position
G90               ; absolute positioning
G1 X-20 Y10 F6000 ; 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 Z5 F100       ; lift Z relative to current position
;G90              ; absolute positioning

Current firmware is
FIRMWARE_NAME: RepRapFirmware for Duet 2 WiFi/Ethernet FIRMWARE_VERSION: 3.4.4 ELECTRONICS: Duet WiFi 1.02 or later + DueX5 FIRMWARE_DATE: 2022-10-20 16:17:41

Adam_Sw3

@fcwilt Thanks Frederick! Its people like you that really go under appreciated in these forums, thanks for your help. I have replied to phaedrux below so we shall see what he says.

fcwilt

@Adam_Sw3

You mentioned that you use an inductance sensor.

In your probe configuration you have chosen type P1. Does you sensor actually have an analog output like a "smart IR probe"?

I've used many inductive sensors and I have always specified type P8, since the output of the probe is either "on" or "off".

I also would like to share with you what steps I perform when starting a print and why I do them.

But I don't have the time right now - it's 5.00 AM.

Doing the needed things in the correct order at the start of a print is important.

Frederick

Adam_Sw3

@fcwilt Hi Fredrick, my inductance sensor is similar to here https://www.aliexpress.com/item/1005004853709100.html?spm=a2g0o.productlist.main.33.60c8l3fwl3fwqS&algo_pvid=6f2ef3f2-1dd9-4b63-a7bd-bb78c1f5cfd8&algo_exp_id=6f2ef3f2-1dd9-4b63-a7bd-bb78c1f5cfd8-16&pdp_npi=4%40dis!GBP!6.68!6.68!!!7.89!!%4021038eda16964986241754812e39f3!12000030753506738!sea!UK!2004704503!&curPageLogUid=BWGfMQ4DwVrl

it has 3 leads, power is connected to my fan header (always on) so i put my z probe signal to my z probe signal header. what does p8 specify?

Thank you.

fcwilt

@Adam_Sw3

It is fairly typical of Chinese units - a bit short on specs. It says it has fast response but I didn't see a frequency spec. Higher frequency normal yields faster response.

I usually get my units from here:

Automation Direct

They have a good selection - for example they list 35 4mm units. And they usually provide full specs. They tend to be more expensive.

Probe type 8 just specifies that the probe sends an signal that is either ON or OFF, which is what these types of probes typically do.

Frederick

Adam_Sw3

@fcwilt Hi Frederick,

Yes that makes sense, So should i change my code to:

M558 ***P8*** C"!zprobe.in" H10 F240 T6000            ; set Z probe type to unmodulated and the dive height + speeds
G31 P500 X35 Y0 Z2.47                          ; set Z probe trigger value, offset and trigger height
M557 X15:525 Y10:400 S50                       ; define mesh grid

What did my P1 previously mean? I am guessing this is frequency specification? As I would be happy for it to work as a switch.

fcwilt

@Adam_Sw3 said in After Z probing, print head smashing into bed:

@fcwilt Hi Frederick,

Yes that makes sense, So should i change my code to:
M558 ***P8*** C"!zprobe.in" H10 F240 T6000            ; set Z probe type to unmodulated and the dive height + speeds
G31 P500 X35 Y0 Z2.47                          ; set Z probe trigger value, offset and trigger height
M557 X15:525 Y10:400 S50                       ; define mesh grid
What did my P1 previously mean? I am guessing this is frequency specification? As I would be happy for it to work as a switch.

From the documentation for M558 here are the probe types:

P0 indicates that no Z probe is present. Whenever Z probing is commanded, you will be prompted to jog the Z axis until the nozzle is just touching the bed and then signal completion.
P1 specifies an unmodulated or smart IR probe, or any other probe type that emulates one (probe output is an analog signal that rises with decreasing nozzle height above the bed). If there is a control signal to the probe, it is driven high when the probe type is P1.
P2 specifies a simple modulated IR probe, where the modulation is commanded directly by the main board firmware using the control signal to the probe.
P3 is similar to P1 but drives the control signal to the probe low. This may be used to switch between different Z probes.
P5 selects a switch by default (normally closed) for bed probing between the In and Gnd pins of the IO connector (Duet 3) or Z-probe connector (Duet 2).
P8 is as P5 but is unfiltered, for faster response time.
P9 is as P5 but for a BLTouch probe that needs to be retracted and redeployed between probe points.
P10 means use Z motor stall detection as the Z probe trigger.
P11 means a scanning Z probe with an analog output (supported from RRF 3.5.0-beta.4). Such probes must be calibrated before use (see M558.1).

Frederick

Adam_Sw3

@fcwilt thank you, so I will need to go for a P5/P8 command? To then turn this into a switch.

fcwilt

@Adam_Sw3 said in After Z probing, print head smashing into bed:

@fcwilt thank you, so I will need to go for a P5/P8 command? To then turn this into a switch.

P8 should work fine.

Frederick

Adam_Sw3

@fcwilt I will have a go now!

Adam_Sw3

@fcwilt Hi frederick, That didnt work. i did some googling and it appears i am having the same issue as this guy -> https://forum.duet3d.com/topic/16118/trigger-height-always-changes/9

I am also using the LJ18A3-8-Z/BX sensor found here -> https://cdn.awsli.com.br/945/945993/arquivos/14_PROXIMITY_INDUCTIVE_18BY.pdf

By the way I know this is frustrating and i am ever so greatful for you taking the time to help me.

Adam_Sw3

@fcwilt Okay it is semi solved now, I have re done my homeall & home z command to be in the centre of the build plate now and that seems to be working. Therefore this leads me to believe that my z movements / build plate isnt level in some way.

Phaedrux

@Adam_Sw3 said in After Z probing, print head smashing into bed:

I have re done my homeall & home z command to be in the centre of the build plate now

That kind of makes it sound like the trigger height of the probe was changing depending on where it was on the build plate.

fcwilt

@Adam_Sw3 said in After Z probing, print head smashing into bed:

@fcwilt Okay it is semi solved now, I have re done my homeall & home z command to be in the centre of the build plate now and that seems to be working. Therefore this leads me to believe that my z movements / build plate isnt level in some way.

That sensor you linked to seems to be very slow.

Take a quick look at this one which has good specs:

Example Sensor

It is a 8mm diameter unit, has a sensing distance of 4mm and switching frequency of 3kHz. That frequency is in the middle of the ranges you can find.

I have tested a few 18mm units but they take up quite a bit of space. I tend to use 8mm for most printers.

I need to write up a summary of how my 5 printers are configured. I have never had the problems you are having.

Frederick

Adam_Sw3

@Phaedrux Thats exactly what it sounds like, how would you remedy this?

Adam_Sw3

@fcwilt HI Frederick, To be honest I dont really understand why i put the 18mm on haha! Yes please do that it would be interesting to see! potentially because mine is about 500mm cubed printing size but even so.

fcwilt

@Adam_Sw3 said in After Z probing, print head smashing into bed:

@fcwilt HI Frederick, To be honest I dont really understand why i put the 18mm on haha! Yes please do that it would be interesting to see! potentially because mine is about 500mm cubed printing size but even so.

I will try to post later today with a outline of my setups.

Frederick