Dual Z for IDEX

[stephenc]

Hello,

I think I'm getting close to finish building this printer. http://www.openbuilds.com/builds/zidex.5259/

I have the duet wifi and expansion board but haven't gone into wiring yet. my question is about Z end stops. since I will have two independent towers each with its own motor driving each lead screw, I want to have their own z endstop. I'm also thinking about using FSR for the Z probing. can I use only 1 FSR board ( it has 3 FSR input) and assign 1 FSR per tower?

Thanks,
Stephen

[stephenc]

Found this article https://duet3d.com/wiki/Bed_levelling_using_multiple_independent_Z_motors
It appear those are written specifically for multiple Z motors connected to bed and adjusting surface tiltness to achieve leveled
Bed.

I'm not sure if this applies to my printer. My bed in Y axis actually fixed in position. I have 2 independent X gantry attached to 2 independent Z leadscrews each with its own motor.

Is there a way to perform and save more than 1 surface mapping?

[T3P3Tony]

It looks like "ZIDEX" kinematics is not yet supported completely (in the sense of mapping for example drive U to X and V to Z) David will be able to confirm.

Two independent X axis are supported, and moving two Z motors concurrently with two drivers is supported (to enable bed levelling as you describe). The bed levelling assumes the two Z motors manipulate the plane of the bed so that would not be what you were looking for in this case, better to use two separate bed height maps. I am not very familiar with FSR sensors, if you instrument your bed with the sensors then they should detect either hotend making contact during probing.

For the multiple bed maps check out the documentation here:
https://duet3d.com/wiki/Using_mesh_bed_compensation

It might work for you to probe the bed with each tool using named height maps:
https://duet3d.com/wiki/G-code#G29:_Detailed_Z-Probe

so save two height maps, Tool 0

[[language]]
T0
G29 S0 Ptool0.csv
 

and Tool 1

[[language]]
T1
G29 S0 Ptool1.csv
 

Then recall them in tool change macros, for example in tpre0:

[[language]]
G29 S1 Ptool0.csv
 
```and in tpre1

[[language]]
G29 S1 Ptool1.csv

Caution I have not actually tested this method but it should work in theory. You may need to make some changes to the area probed, given the offsets of your towers:
[https://duet3d.com/wiki/G-code#M557:_Set_Z_probe_point_or_define_probing_grid](https://duet3d.com/wiki/G-code#M557:_Set_Z_probe_point_or_define_probing_grid)
 
That is a very interesting printer design it will be fascinating to see how you get it working.

[stephenc]

glad to hear that each tool head can have it's own height map. I think this is exactly what I'm looking for to make this printer work.
my probe FSR sensor is a bit crude and manual at the moment I'm planning on intercepting between nozzle and bed

[T3P3Tony]

Ahh yes, that does not look to be a long term solution for your FSR

The 2 height maps is theoretical, you need to test to see how it works.

[stephenc]

your theory is sound. I will definitely give it a try. me being new to duet will have a lot to catch up on reading… thx