Wrong Start Location: Cohesion 3D & Lightburn

Machine: K40 with Cohesion3D

Board: LaserBoard

Firmware: Smoothie
Build version: edge-54d22942, Build date: Jun 5 2019 14:09:26, MCU: LPC1769, System Clock: 120MHz CNC Build NOMSD Build 4 axis

PC: Windows 10 Pro 21H2 (OS Build 19044.1466)

LightBurn 1.0.06
LightBurn Device Settings: X: 355mm, Y: 170mm

Problem/ Question: I will start by referencing a previous locked post:

“Cohesion 3D & Lightburn in Window 10 new issue”

When I send a project at the laser it starts engraving in an obviously wrong location and if i let it go for long it will slam the head against the zero X rail and then proceed to another area.

It is important to note, Home and Origin do not change.

LightBurn Start From: Absolute Coords

Today’s scenario: I performed some test cuts that used 50% of my project board. I have been testing this project for the past week. Today after the first LB project run on the left half of my board, I wanted to reuse the remaining 50% on the right half of my board to duplicate the LB project. So, I moved my project to the right side of the board in LB. When I started the project, it started the right side of the project in the top left corner of the workspace near the left boundary (Position Y: 170mm, X: 20mm) and proceeded with all cuts. Then it proceeded bumping against the left boundary persistently trying to move left to finish the remaining images.

This has been happening approximately 1 in 10 uses for me since purchase in 10/2021. It has been getting increasingly stubborn to resolve.

Previous resolution steps:

  1. Close LightBurn
  2. Unplug Cohesion3D power supply (important)
  3. Turn OFF OMTech K40
  4. Unplug the OMTech K40
  5. Plugin the Cohesion3D power supply
  6. Plugin the OMTech K40
  7. Turn ON the OMTech K40
  8. Load LightBurn
  9. If the problem persists, delete the device in the LightBurn Devices and re-add it.

Usually this works.

Yesterday when this happened, I proceeded to follow the referenced article above and replaced the Original SD card I received in October with a spare. Today, after a couple of hours working on the same project, it happened again. I replaced the 2nd SD card with a 3rd.

The 3rd SD card has been unsuccessful, as well.

I’ve reached my end of solutions. I am beginning to feel as if there is an issue with: 1) Cohesion3D board, 2) Smoothie firmware, 3) recent Windows 10 update or ???

New product season, I would appreciate any help.

Thanks in advance

I’ve been loading different projects in LB to test. It doesn’t matter what project I load or how much coverage is in the project on the workspace. ALL projects cut/engrave with some unknown offset of X = -240 or such (approximation for discussion). So, an object with right boundary of X = 290 will print in approximately X = 50 (example, not exact). All projects have this “adjusted” X behavior.

I have not made any changes and no offsets in my settings.

Oddly, I can move the laser position in LightBurn correctly to any spot on the physical workspace. So, X = 280 moves to the correct spot. The offset behavior is only happening when the project executes.

UPDATE: I pressed the reset button on the C3D LB and jobs are executing correctly again. I will continue to test. If I don’t update again, problem resolved. I think my troubleshooting procedure is getting revised with a new Step 1.

SOLUTION: Use correct config.txt (adjusted for my machine) in the SD card.

Upon further testing, I found the behavior reappearing. After lengthy inspection, I found I had copied the original config.txt to ALL SD cards I used and was not using the modified config.txt to match my K40.

By some luck, I had been using the wrong config.txt for 3 months, but had been using the same project size every time and had not encountered variations that revealed my oversight. I switched to a new project size and that revealed the mistake I had made 3 months previous.

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