Problem with Z-offset during the toolchanger - Duet2 Wifi

simobone19

Hello everybody,
I started to build a 3d bioprinter using duet 2.
I used the particular extruders with a unusual geometry.
I have a problem with the Z-offset of the T1 and T2, in comparison to T0 Z position.
I calculated tools different Zs and I update the config.g file with G10 command:

G10 P0 X-0.81 Y49.74 Z0.00
G10 P1 X-0.82 Y50.12 Z-0.9
G10 P2 X-0.20 Y50.44 Z1.85

When I checked the Z position, when I impose the command T1 the system adjusts the position of the bed +0,9mm, maintaining the Z position value in the console graphic. When I regulate the position of tool 1 at Z = 0 the tip is really far from the bed (1.8mm). I can arrive at the value of -0.9 mm of Z and after that the system stop the movement. In consequence I have a tool at 0.9 mm from the bed.
The same behaviour I find with the tool 2 but in the opposite direction because the difference is positive.
Can same people help about that?
Thank!
Simone

jay_s_uk

@simobone19 if your bed needs to be higher for tool 1 compared to tool 0 then the z offset should be + not -

simobone19

Thanks jay_s_uk,
I tried but the Z offset when is negative, when I impose the command T1 the system adjusts the position of the bed +0,9mm (from 10 to 10.9) and I can move the Z until -0.9 mm. When I changed with positive, when I impose the command T1 the system adjusts the position of the bed -0,9mm ((from 10 to 9.1) and I can move the Z until +0.9 mm, i can go at lower values. In each of case, the system maintain a offset off 0.9 mm.

simobone19

The z-axis motor when adjusting position after tpre.g turns in the wrong direction. i don't understand why but there is an asynchronous between the previous movement and the value that is subsequently imposed as a limit by the system.

dc42

@simobone19 the axis limits set by M208 are for the head reference point, which is the point from which all offsets are measured. It follows that if a tool has a positive Z offset, then for that tool to reach Z=0 the M208 lower Z limit will need to be negative. So you can either set your M208 lower Z limit to -1.85mm in config.g or you can adjust the M208 lower Z limit in your tpost#.g file for each tool.