Z axis starts to high even after homing

My mpcnc works great except it starts carving 3mm to high with or without touch plate. If your doing a large piece it goes through several layers before actually coming into contact with work piece. I’ve tried manually homing z and even made sure it knows where i want z0 to be but when you run a job it starts 3 mm too high.

How are you setting Z=0?

  • What are you using for CAM to create the gcode job?

  • What does your starting code like?

  • How do you set up your machine to prepare for the job.

The machine has no inherent way to know where 0 is, it has to be told

Now let’s say that you use the touchplate to set Z=0 to the top of the work, but the code backs off 3mm yo allow you to remove the touchplate, but your CAM adds a G92 X0 Y0 Z0 to the start of the gcode. This will then set that current position 3mm above the work as Z=0 undoing the setup.

Personally, I do not use code in the job to set the zero point, for pretty much this reason. I always set up my zero points before starting the job, but that is my work flow. Others do things differently and it works for them.