Mistake in IDEX configuration guide for RepRap

JNB

Hey,
I just stumbled over a mistake in the tutorial for configuring a IDEX-Printer.

It states that the U-offset should be added / subtracted from the M208 U-Axis value.

"Subtract the U co-ordinates from the X co-ordinates and you have the rough offsets for U and Y. For the U value, increase or decrease the value of M208 Uxxx by the U offset, so that when the U axis is homed and then travels back to the spot it is above it for the same X co-ordinate as the X axis. For the Y co-ordinate add it to the G10 P1 Yx.x tool definition."

Source

By doing this you change the virtual length of the axis in relation to the actual length, which results in changing the relation between a virtual mm and a real mm (e.g. 1mm in reprap is 1.2mm in reality).

The correct way is to change the offset in the G10 of the corresponding tool.

For example: G10 P1 U3 Y-3 Z0 (resulting in bringing the tool 3mm more to the front on the Y-axis and 3mm to the right on the X-axis)

Would be nice if this could be corrected.

Greetings
JNB

dc42

@jnb you can do it either way. If you line up the nozzles by adjusting the M208 U maximum value (which is also the homing position), then for any adjustment you make to the maximum position you can make a corresponding adjustment to the M208 U minimum. This will keep the allowed U movement range constant. Even if you don't adjust the U minimum, it will not result in the scaling error that you suggest, it will just mean the U minimum limit isn't quite right.

My preferred way would be:

Set the X, Y and U tool offsets to zero.
Set the M208 U maximum as described in the wiki, so that the two nozzles print in approximately the same place.
Set the M208 U minimum so that the U head can't quite crash into the parked X head.
Make fine adjustments to the calibration by adjusting the Y and U offsets of the U tool.

fcwilt

@jnb said in Mistake in IDEX configuration guide for RepRap:

By doing this you change the virtual length of the axis in relation to the actual length, which results in changing the relation between a virtual mm and a real mm (e.g. 1mm in reprap is 1.2mm in reality).

I think you will find that if you experiment that the M92 settings of steps/mm control the scale regardless of the axis min/max settings.