Does your K40 grind and causes noise when homing?

When you turn on your K40 laser machine it´s default setting is to home to top left corner and stop.
It happens that the machine starts to bang against the fence and it sounds like a grinding noise – it´s the belt jumping on the the drive pulley.
For some errors you can also see it moves to top but then suddenly starts to move to the right very slow. The cause is the end-stops for both situations.
If you have a external 24V power source for your controller board and stepper motors, make sure to power them on at the same time when starting the machine. Thanks to Eric noticing this in the comments!

The reason is actually pretty easy.

On both axis there is a optical end-stop with a metal tab, when it comes in to position the movement stops.
It´s also from this position the machine can calculate where the head is in the machine so it doesn’t run too far right or down.

How to fix it

Make sure the metal pieces are inside the optical end-stop in top left position.
If they are, check all cables and remove the optical end stops and inspect them. It happens that solderings are bad and cracks with time.

I suggest changing to mechanical end stops – article how to do this is being written right now.

Here is the Y-axis end stop circled with red.
k40 laser y axis end stop

Here is the X-axis end stop circled in red.
Located behind the laser head.
k40 laser x axis end stop

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First of all, thanks for all the information you share here, it’s been really useful.

I have an issue and I was hoping to get some info before I replace the controller. My machine homes correctly on the Y axis, but the X axis behaves erratically and never gets anywhere. If I manually move everything to the top left the movement stops, so the end-stops seem to be working.

I’ve also disconnected the motor and connected it directly to the controller instead of using the flat cable that carries both the X signal as well as the end-stop signals, and in that case the motor moves correctly.

Is this a common problem, or something completely random?

Thanks in advance!


Thanks for your answer! I’ll try to run direct cables to see what happens then, I’ve been suspecting that small board as well, but it seems so simple (just bridges and a single resistor) that it doesn’t seem possible for it to fail.

Thanks again!

mrs deborah wagstaff

mechanical end stop not working, need to know what to buy to replace on a K40 laser engrver

mrs deborah wagstaff

mine are a 6 pin, i got a 3 pin one but not sure how to install them.

mrs deborah wagstaff

they are the ones that came with the machine, i will try take some picks for you

mrs deborah wagstaff

sent them over for you, as best i can get photos of them


In my case, the homing didn’t work properly for a different reason. When I switched on the power, the laser head only moved a bit to the right and down, and quiet slowly. The reason turned out to be that I was switching on the external 24V power supply I added to the machine, which was powering the board and motors, but not the original 220V power supply for the rest of the machine. The 220V needs to be on before or at the same time as the 24V for homing to work.