IDEX z probing question

[Ray11]

I previously saw someone/company using endstop mounted on the carriage to probe the bed with 4 points (I will add the link to video if I can find it). Two on the left using left extruder, two on the right using right extruder. I would like to try mounting 4 limit switches on the bed wiring them in series such that I can use the left extruder to touch the left two and vise versa. This means that there will be some z offset for each of the limit switches and I need to probe the mesh with two extruders. I searched around and couldn't find any resources on that. I'm thinking of something like this:

T0
G30 P0 X20 Y50 Z-99999 H3.5 
G30 P1 X20 Y200 Z-99999 H3.1
T1
G30 P2 X210 Y200 Z-99999 H3.2
G30 P3 X210 Y50 Z-99999 H3.1 S4
 

But G30 with S parameter seemed only to be for printers with multiple z motors.

Thanks!

[T3P3Tony]

@ray11 is this to set the extruder offset or level the bed? i don't understand what the benefit of two switches on each side is. The video would be helpful.

[Ray11]

@t3p3tony https://youtu.be/EDbU1zlC3Ss?t=148
So instead of mounting microswitches on the hotend, which is pretty crammed for an idex setup. I want to try to mount the microswitches on the bed instead.

[T3P3Tony]

@ray11 i guess one issue then is how to accurately set the difference between the endstop heights, vs a bed that is not level. If the assembly process between machines is incredibly repeatable then you may get away with getting that offset set to 0 (or a known offset). If its not repeatable enough (most likely) then my view is this will not end well as you will have to manually calibrate the switch offset really well, before then levelling the bed.

[Ray11]

@t3p3tony Your point is right, what I thought about this is that I will first level the bed manually, then probe the four microswitches, record the offset at each probing point, and update the offset of each. I just wonder if currently, RepRap firmware allows individual offset and mixed tools for probing. Sorry, it is quite a wired use case.

[Ray11]

@t3p3tony So I think the correct way to frame this question is if I can use G30 to probe 4 points, record the "G32 bed probe heights" and save it to heightmap.csv using gcodes defined in the firmware?

[T3P3Tony]

@ray11 i don't think heighmap.csv is the way to go because you want to level the bed rather than just compensate for the bed not being flat. You would either use the manual bed levelling our auto bed levelling depending on what your mechanics support. I have asked @dc42 for his input.

[o_lampe]

@Ray11
You can use bed.g for multipoint probing without having multiple z-motors. You can even apply the pitch of your leadscrews and after probing you get an echo on DWC console how many degrees you have to turn each leadscrew.
What I'm not sure about is your plan to wire all four switches in series. IIRC you'd need a separate endstop input for each switch.
Maybe you can redefine the endstop-config between each probe point to get away with a single e-stop?

[Ray11]

@o_lampe Do you know if there is an example code I can look up to adjust the leadscrew? It would be really nice to store the offset, do some math, and then print it out as a prompt on the LCD display.
I think if I wire all endstops with series and connect them to active high, then once one is triggered, the entire circuit will switch to low. I can then use only one io port on duet.

[Phaedrux]

@ray11 said in IDEX z probing question:

Do you know if there is an example code I can look up to adjust the leadscrew?

You mean like this? https://duet3d.dozuki.com/Wiki/Using_the_manual_bed_levelling_assistant