Absolute coordinate fail

I was doing a one pass at a time burn of a large logo on plywood. Forgot how many passes I used previously so I just burned and hit play again as it wasn’t going through. But on the third burn I hit “Home” in stead of play. When I pressed play after that the laser was off by 1 mm ruining the logo, and about a square foot of plywood. Is absolute coordinates that inaccurate or is something wrong with my Xtool D1? Why would it not go back to the exact same location after a home command?

Is has nothing to do with absolute coordinates and more to do with the precision of homing. Every machine will have different tolerances for how precise the homing sequence is. If you are using the original D1 with sensorless homing I wouldn’t be surprised if 1 mm was about what you could expect in terms of homing repeatability.

If this is a machine with physical switches then depending on the quality of the switches and other mechanical aspects of your machine the repeatability could vary.

Wow. The romans built aquaducts of stone with better precision than this. 1 mm off on a 400x400 mm work area is horribly inaccurate (in my opinion). It is after all a machine that operates with a claim of 1000 dpi “resolution”. But at least knowing that the machine is that inaccurate enables me to work around it.

To be clear, the accuracy of the machine is likely high in terms of motion. Meaning it can make accurate movements within fractions of a millimeter, typically in the range of hundreds of a millimeter and it will do this across the entire range of the laser.

Where this problem is introduced is in the precision or repeatability of the homing process, meaning locating to a specific position in space to set origin at homing.

In practical terms, this means that between homing, you should have highly accurate motion. Across homing you’re likely to get much more variation.

Consider that most people with the original D1 do manual homing, meaning they physically place the laser head to the top-left before starting the machine instead of using the sensorless homing mechanism. You may want to actually test manual homing to see how precision compares to the sensorless homing process. Many people can’t get the sensorless homing to even work as the laser module will crash into the sides of the machine harder than expected.

I haven’t seen any reports on how precise the homing is on the Pro machines with physical switches.

Well I thought I could work around it. BUT.

I have a coaster design with a circle that is supposed to run 3mm in all round the coaster. Using either sensorless or manual homing there is no way to get this design accurately placed on pre cut wood coasters. 1 mm off means the whole burn is a fail. Is this really as good as it gets? I have seen so many videos online about prcise placement usnig either wasteboard or jig. But what good is a jig if the laser doesn’t start in the same spot every time. What kind of design can be 1 mm off on a 100 mm piece and not look croocked? Manual homing is no better. When moving side to side (stading in front of the machine) it is fine because the laser hits metal, but towards the back it hits cables or something else and flexes back slightly. All wires are strapped across the gantry according to the instructions. Is that the probelm here maybe? Do I need to move them somewhere else? Should it hit metal in the back as well?

There you have it.

Homing depends on sensing when the axis stops at the end of travel. If that endpoInt is flexy, the endpoint isn’t stable, and the home point isn’t fixed.

Some machines have a small tab to contact the home switch, and sensorless homing may depend on something similar. In any case, flexy isn’t going to work: you want a solid klunk.

Stabilize the home position and see if that solves the problem.

Agree with ednisley here. Hard to say based only your description but what you’re describing definitely doesn’t sound right. You should be getting clean unimpeded contact on the left and back of the machine.

You’re now talking about something slightly different, however. Homing isn’t the only mechanism by which work placement and alignment can be done.

There are other techniques you could employ to overcome any homing slop.

But let’s see if you can get any closer with the homing fix.

I’ll check and reseat any cable or cable ties that are making contakt with the frame. I just have to move the machine and it is a bit annoying.

I have made a target on my jig to enable an accurate starting location by firing the laser and manually placing it on the target before each burn. But I still want to fix the flex issue.

I too have been on the seemingly endless journey to get my xTool D1 to be able to repeat a job from home in the exact same place. I understand that the motion accuracy is incredible and that is why I find this specific issue so incredibly frustrating.

From the of hierarchy of machine settings and controls. The finicky way Light Burn writes values back to the console and somehow reverts back to some other settings is very frustrating.

This is what I’ve known so far and have gotten close to acceptable results.

Fabricated this Y axis stop, the left X axis seems to be a good hard stop, but as others mentioned it was difficult to get a split Y stop to be positive with the cables.

I have tried to change the home debounce to 0. Send it home. Slide the head back and to the left. Go to light burn and say get coordinates. Then set those to user origin and it will do great for awhile, and then will jump around for some completely unknown reason. When I’m making one cut out of the middle of a piece it doesn’t matter. However when I’m trying to engrave a $100 AirPod case for a friend, it makes me look like an idiot.

Any other advice or tricks would be appreciated.