Installation question

I’m making an engraving machine with a larger area than the original k40.
I have a k40 from which I take the laser tube, the power supply and the front panel.
My idea was to also take the engines of the original (the frame is in 30x30 aluminum profiles like the workbee or the x-carve) but unfortunately the transverse structure is too heavy (about 2-3 kg) and only one engine to the y axis it generates friction.
I tried with two larger external 3d printer engines connected to a single a4988 driver with arduino ramps controller and it seems to work properly but I do not trust this controller and it seems really slow
So I ordered a cohesion board but before it comes as I think I would like to confirm that everything is right and that there are no problems or fry the board
Here my pinout diagram

1- Can it work without the motors losing step or power?
2- I wanted to replace the optical end stops with the mechanical ones, is it OK to connect them like that?
3- if you take the 24v from the external power supply and the 5v from the usb connected to the computer do I have to remove the 24v and 5v cable from the k40?
4- Do I have to change the firmware if I have this connection?

thanks a lot

Hello, anybody on the forum???

On point number 3:
The 5v from the computer is disconnected.
The 24v and 5v from the lpsu is disconnected on the laserboard.
So no you don’t need to cut/remove any cables.

All the power required is supplied via the power brick supplied with the laserboard.


What made you decide to use the external stepper drivers with this? The built in ones should be able to handle your setup.

Also, you shouldn’t use two motors on the Y axis, if one of those motors fail, the y axis can go sideways and redirect the beam in a dangerous manner.

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I tried with the double shaft integrated with arduino and a system of bearings for the shaft along the entire length of the frame(like k40) but does not flow well (use linear guides with low friction) because I think that with that length lose torque at the extremity while with two engines it worked well and now I would like to integrate this system with cohesion board

Unfortunately, I can only advise you to use one motor for the Y since your setup isn’t recommended for a CO2 laser. For diode lasers, it’s fine, but for a CO2, you should use a shaft setup. I am building a 500x900 and it will be using a shaft. Even if you have to go to a slightly larger motor, it’s the best way to go.

exact, but I could remedy these problems with a system of protection in case of failure of one of the engines

ok thank you
but why isn’t recommended for a CO2 laser? and for diode it’s fine?

Because a diode laser outputs from the head. A CO2 laser uses a mirror system and if the X axis should happen to shift because one of the Y motors fail, it can redirect the beam to somewhere outside the laser.

ok.I understand and it is true, but there are no hardware limitations or voltage problems using two external drivers in parallel and two motors?
My mirrors and my laser tube are directly in the transverse axis, so if a motor y fails and the axis is no longer parallel the beam enters the same in the final mirror :slight_smile:

I was just always told not to use two motors on the Y. You can still use one external stepper, but I wouldn’t. I’m going to be using an 8mm shaft with a 5mm to 8mm adapter. I can probably use a 5mm shaft, but I want to minimize any shaft twist, although there probably won’t be any at all on a 900mm setup. It’s going to be using a 1000mm 40x40 V slot rail.

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I was thinking, another way to safely use two motors would be to still use the shaft, but have one motor on each side of the shaft and just reverse the wires on the left motor. Still only need one external driver. One driver is all you need if it can handle two motors and most external drivers should be able to.

thanks Jamie i’m considering this option

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