How to override Z=0 limit?

Hello !

Here is my question !

I recently upgraded my laser (With Ruida 6442) with a stepper motor for Z, limits switches and a Z sensor.

Everything is OK. When I click on Autofocus, the Bed lift until it triggers the sensor then go down until it reaches 15mm between top of the wood and bottom of laser.

Z is resetted to 0.

But, it’s OK for drawing, not ideal for cutting.

For example, if I want to cut a 8mm board, maybe it would be better to set the focus to +4mm so that the focus will be centered in the middle of the board.

Then comes the question:

I can’t lift the bed, because Z=0 and Lightburn nor the Ruida allows me to override this limit.

I’d like to lift the bed until Z shows -4mm for example but I didn’t succeed.

I can fool the system and set up my autofocus by using a 8/2 = 4mm board but it’s not convenient.
Any ideas how to proceed ?

Thanks !

1 Like

That’s pretty much the only way to do it, because Ruida controllers know the autofocus pen will crash into something, so they prevent raising the platform beyond the Z=0 level. Given the few millimeters of Z travel between the pen tip and the bottom of the nozzle, they’re probably right.

You can autofocus on the platform (or a thin card), then lower the platform to the proper focus point using a step gauge, but that pretty much negates the value of an autofocus setup.

I mostly work with thin material and set the pen to put the focal point about a millimeter below the surface. If I were running a lot of thicker material, raising the pen a few millimeters to move the focal point would make sense. So far, it hasn’t.

Hello ednisley,

thanks for your answer.

I agree with you, overriding Z may be dangerous if you exceed 4 or 5mm…

I work mostly with thin material and 6mm wood cut well.

It was rather a theorical question and I wanted to check if cut would be better of faster by focusing in the middle. I will try different focus for cutting by zeroing the Z on the bed itself and see if it changes the results and decide if I should change my process.
For thicker material, I prefer to use my CNC (Less smoke, more beautiful sound ?)

Thank you for your help !

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