G28 detail question
-
We're got a printer that we're working on implementing a Jubilee tool-changing mechanism that uses a gear-reduced stepper motor. We lock an unlock a tool during a tool change by turning the motor one way or the other. The unlock direction turn until the mechanism reaches a limit switch, so we know the mechanism is aligned for picking up or dropping off a tool. Locking a tool requires moving in the opposite direction until a certain torque is reached, as indicated by a second limit switch and fancy spring mechanism, so travel in either direction is protected by a limit switch. We've got lock and unlock macros that are working properly, using G1 H1 moves. In our implementation we've assigned this motor the U axis and we want to NOT home the U axis. There is no need and a homing move might cause a tool to unlock and fall off.
The question we have is how to set up for a G28 (home all). If someone touches the home-all button on DWC or Paneldue, we understand that a G28 command is issued. Reading the G-code dictionary page, we find this:
If ALL axes or towers are to be homed, the file homeall.g is processed, except that on a delta printer homedelta.g is processed. If this process results in at least one axis, but not all axes, becoming flagged as "position known", an attempt will be made to home the remaining axes as if the G28 command had listed those axes.
We can set homeu.g to do nothing, but we expect the U axis will not be flagged as "position known" and the user interfaces will indicate that homeall.g has not completed.
If we use a different axis designation, will G28 skip it? Can we easily change the axes called by DWC and PanelDue and designate only XYZ homing? Other thoughts on this?
-
You can always use G92 Unnn to tell the firmware that the axis is some known position and that will mark it as homed.
It doesn't matter if that is the real position since you are moving it with G1 H1 commands.
And it seems the next G1 H1 move will set the position to the axis min/max.
Frederick
-
@fcwilt - Thanks for the G92. I did not realize that this would mark the axis as homed, but it does make sense. I'll just add it to the end of my homeall.g and that'll do it.
