K40 Problem — head moves wrong direction to home after using rotary

I unplugged the the Y axis and put a rotary unit in the K40 as a trial. after returning to the normal use when I turn on K40 the head goes forward on the X and Y axis crashing into the framework and juddering. Is there a cure for this as it was working previously ok. If anybody is in the Bicester area contact would be useful.

Turn off the machine and slowly move the head somewhere in the middle of the work area.

When you turn on the machine, towards which corner does the head move? (A video of this may provide some useful information for trouble shooting.)

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The head moves towards the front right hand corner

But aren’t your X and Y end stops over at the Left Rear corner?
Did you change your Device Settings and set the wrong position?

Perhaps you set something to be mirrored or reversed when using the rotary?

The head moves away from the endstops if the controller things the endstops are already engaged. And only once they got disengaged, it will start moving towards them.

The endstops of K40s are normally closed. So, if they are disconnected, the controller will think they are always actuated.

If your machine uses that flexible flat cable, check if it’s properly seated. If it uses that endstop connector, check if that one is properly seated. Well, just check if all connectors are properly seated while you’re at it.

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Try powering off, removing the stepper connection that you used for the rotary, then rotate it 180 degrees. See if that fixes it. I don’t recall if those cables are polarized but if they’re not they’re easy to install backwards and will work in the opposite direction


Sorry, I am late to the conversation. If you’re using K40 Whisperer, click “Settings” and click on the “Rotary Settings”, that box should be uncheck if your not using the rotary tool and just using the regular laser. Next try clicking “Settings” find “Advanced Setting” and make sure that your box is unchecked for “Mirroring”. That’s the best I can come up with for now. Please let us know what works for you for when it happens to one of us. I hope this helps.

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Now that I think about if more it seems like I’ve heard @Scorch say that the homing process is entirely handled by the K40 itself, Whisperer just gives it a “home” command and it runs. So I don’t think Whisperer could reverse the homing.

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@garmentman the K40 has the end stop switch for the X axis on the LEFT side of the X axis rail and the Y axis end stop switch is at the back of the machine( mine is at the left rear ).

As you know, both axis should home to the left rear when you power up the machine. Does that happen?

My next question is what controller board and computer software are you using. Maybe post a picture of the controller board and a picture of your K40 build area too?