Need help Homing sequence in H-bot( CoreXY) system

Hello,

I'am using a similar corexy machine, and I have not found the solution for automatic HOMING.
As explained above, as in Hbot configuration, both joints need to be moved in order to have a straight X or Y movement.

During homing both joints (motors) needs to be driven.

Does anyone already found a solution for homing a corexy (or Hbot) configuration ?

Thanks in advance.
Best regards. Bernard

I think that you can probably do this by configuring simultaneous gantry-style homing. (which means using LinuxCNC v2.

In the case of a gantry this means that both joints move towards their own home switch and then the first one to get there stops and waits for the other to get to its.

It seems that the same setup might work for H-bot. There is nothing to say that joints homing in tandem need to home in the same direction or at the same speed.

Squinting at diagrams I don't think it matters which joint is allocated to each limit switch, by the time homing is finished each axis is in a known position and each joint can be called home.

It is important to realise that homing is a joint-level action, not an axis-level one. But putting the joints in a known position will always put the axes in a known position for any workable kinematics.

Hello Andypugh.

Thanks a lot for your reply.
I'am indeed using version 2.8 of linuxCNC.

I tried the Gantry idea with synchronized movement on joint 0 and joint 1 (sequence = 0 on both).

The 1st part of the homing is working great: The mobile/head moves on X up to the stop switch.
Then, one of the motor stops. This was expected;
2nd part, the remaining motor continue to move in the same rotation direction as in 1st part.... unfortunately the mobile/head moves in diagonal, toward the right direction on Y but in the wrong direction on X: the mobile/head hit the end of travel immediately. Impossible to home the remaining joint.

I also tried a regular homing (sequence= 0 and sequence = 1), but it doesn't work very wheel because the homing works only the the mobile/head is in some specific area of the machine, and also after the homing, the final position is never at the same place on the X axis, because it depend on the position of the mobile/head before the homing... It's then not reliable.

Is there a way to make an "immediate homing" on both joints, and then, when in world coordinates X, Y, Z, run a python (for example) code to move the mobile/head toward the X limit switch and set X=0 in the interface, and then to move toward the Y limit switch and set Y=0 ?

What do you think ?

Thanks in advance.
Best regards,
Bernard

Try sequence = -1 on both.

Since to move in the X axis both joints must turn in the same direction, and to move the Y axis the joints must turn in opposite directions. I think the only way joint homing might work would be to home to flags mounted somehow on the belt.

Another option might be to use immediate homing to get out of joint mode then probe your x and y home switches and reset the home position to that point.

Todd Zuercher wrote: Since to move in the X axis both joints must turn in the same direction, and to move the Y axis the joints must turn in opposite directions.

What happens if only one turns?

Another option would absolute encoders.