Laser cutting in the wrong place (some lines offset), file to large?

I’ve got a chinese laser using the newer Ruida controller. On larger files, sometimes I have found that part of my cuts are offset to one side or another, almost as you’d expect from a slipping belt.

After tightening the belts and having the “offset” happen again, I noticed that small readout screen on the laser matched what I was seeing cut into my material. In my understanding, if it was a slipping belt the image on the lasers screen would look as expected - not all offset and wrong.

After some googling I have seen varying opinions that data can be lost in the transfer between the PC and laser. I am wondering if this is what is happening here and if anyone has any advice as to what I can do to solve it. I am using a USB cable that was provided with my laser.

I have also read that a motor driver could possibly be the culprit. Any truth to this?

Apricate any help! Thanks!

A bad motor driver wouldn’t result in the cut showing incorrectly on the display. Which version of LightBurn are you running, with what kind of PC?

We’ve had some intermittent communication issues with the last couple releases that I’m trying to track down, but I’ve been unable to reproduce it on any of our hardware, which makes this incredibly difficult to find.

As much information as you can tell me about what controller, firmware version, computer, OS version, etc would be useful. Are you connected with just the USB cable, or through a hub or adapter at all? Anything you can think of.

Hey Oz, thanks for the reply.

I’ll grab you as much info as I can get you.

I am on lightburn v9.20. I have a windows 10 PC. My laser is new in Jan, and things were working well up until a few days ago. I believe my controller is a RDC6445G. I will need to confirm that but I am 90% sure. When I dig into the info on the controller itself it says “mainboard version v15.01.19”. Hopefully thats the firmware version?

The USB is plugged into a hub on the side of the machine, which then runs to the controller. I will gladly just run the USB directly to the controller for testing.

I have read that using “start” instead of “send” can drop some data, is there truth to this? I will be attempting to use “send” from now on for testing.

If theres anything more you can think of that I can try I am willing to with some guidance. I have a cnc plasma table as well so I am somewhat familiar with this stuff, though there are a lot more wires on the laser.

The smoking gun here in my opinion is that the messed up cut shows on the display, which to me indicates the laser is doing what it is told. And it seems to be only present on larger files where I use my entire bedspace to cut lots of smaller parts, which again makes me think data transfer.

Is there a way to clean out any stored files (if there are any) in my controller to give it more computing power to process everythng?

In LightBurn, from the ‘File List’ window, ‘Refresh’ will read the current controller file list and display here. You then have options. :wink:

From the HMI of your controller, look under the ‘Files’ button menu for management of these files directly from the control panel keys.

There is, yes, but it’s rarely an issue when cutting, more often a problem when running fast, dense engraving data. That said, it can still happen occasionally. The fact that you’re having this issue on 0.9.20 is pretty unique though - nearly everyone reporting a problem like this has been on 0.9.21 or above, where we changed the underlying way the comms are handled.

When you use ‘Start’, a bunch of data is buffered by the controller before the job actually begins. If the job is fast or complex (ie, lots of commands to process), it’s not impossible for the controller to drop a bit of incoming data because it’s doing too much. If you use ‘Send’, the file is sent to the controller completely, then you run the job, so the controller is only doing one thing at a time.

I use both regularly, and have only ever had a file corrupt when running dithered or grayscale engraving at 500+ mm/sec, otherwise, it’s never missed a beat. Your mileage may vary.

Other things to check:

  • You mentioned a hub, sometimes those can be troublesome

  • There’s a short extension wire that connects the controller in the machine to the USB port in the case that you plug in to. Those can wear and may need replacing. If this happens, the first sign is usually intermittent USB issues. Try connecting direct to the controller within the case to see if that fixes the issue, if so, replace that little extension. Don’t leave the computer plugged in directly for long - if you trip on the cord you’ll need to replace the controller, not just that little extension.

  • Check the USB cable itself. Cable quality varies, and a cord with ferrite chokes (on one end at least) is better than one without.

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