Laser will not fire,durning camera alignment laser will not fire

Machine: K40

Board: cohesion3D

Firmware: Smoothie or GRBL-LPC? “I have a new board and I’m using whatever it came with” is also a great answer!

Problem/ Question: after install of all i ran camera lens calibrate no problem there, Ran camera alignment and laser will not fire. Test fire of laser works fine. Please help


Hello Bob, can you please provide some pictures of the LaserBoard and wiring? We always ask for pictures and try to go through some diagnostics to start with. We’ll definitely want to see a photo of the large connector that goes between the LaserBoard and the LPSU since that controls the laser firing.

Let’s also get some photos of the LPSU, and any text or labels where the wires connect to it. Confirming everything is wired up correctly is our goal.

Hey Pete how do i send you photo

Bob, when you reply you can click the little “upload” icon, or you can just drag an image into the reply editing area.

Thanks for the photos. Sadly the four wires running from the LPSU to the LaserBoard are all the same color. Blue is great color, but makes it hard to tell what is what.

If you check out our LPSU guide you’ll see that most (but not all) K40 laser power supplies have the wires in this order from left to right: 24V, G, 5V, L. We need to ensure that the correct wires from the LPSU connect to the appropriate places on the LaserBoard connector. We really only care about G and L as those two are needed to fire the laser.

Would you be able to check that the wires are all connecting in the correct place? You may need to unplug the connector from the LPSU to check the labels to see which wire is which. Again, we just need G and L going to the correct place on the LaserBoard.

[quote=“raster, post:7, topic:2246”]
Pete what is LPSU?, is it the power supply. If u would like to call me here my phone ADMIN REMOVED PERSONAL INFO

Bob, the LPSU is the “Laser Power Supply Unit” and the part of the laser that provides high voltage to the laser tube so it can fire.

The LPSU is controlled by the LaserBoard, and with LightBurn and the LaserBoard you can control the power of the laser so it’s not at 100% all the time.

Your LPSU is in the third photo you posted. It’s the bluish metal box. It will look like one you see on this page:

We need to make sure the wires for G and L going to the correct place on the LaserBoard.

The other thing we can try is to manually send commands to the LaserBoard to fire the laser.

(Note: some lasers have safety interlocks, so make sure your lid is closed and then try the following.)

Send some lines to the LaserBoard using the console in LightBurn as explained here: PWM tuning for Smoothie Firmware such as G1 X10 S0.8 F600

It should look something like this:


The laser head should move while firing. A red LED “Laser Fire Status” in the bottom left corner of the board should turn on.

Tell us exactly what does and does not happen.

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