Z cut starts high

Z starts high?? . I have zeroed Z both by plate and to work piece. When I start cut, tool is about 5mm high. Machine has been calibrated. This is a change as I had been able to cut normally. Have I altered a GRBL setting?

Have you measured your probe disk thickness and input that information into Easel machine setup?

Thank you, yes. At moment using a copper plate 0.51mm thick and entered that figure into settings. On the wild assumption that this was being read as 0.5 " I set figure to zero, but no change. In addition, if I zero just with a slip of paper the tool still starts about 5mm high.

Are you using Easel or another sending program???
If you are using Easel, when you hit the carve button is the bit raising moving to start location and then down to the work piece? OR is it carving above the the work piece (Carving Air)???

I am using Easel. I zero the bit and then raise the bit. I would say however , although this did not affect it previously, my machine zero is different from my material zero, in which case I move forward say 100mm, zero on material and then move back, after bit has zeroed and raised. When I probe zero, the bit automatically rises. When I manually zero I raise the bit a fraction and return to machine zero. When I hit carve, the bit proceeds to my material start point, but will carve air about 5mm above, proceeding into material.
Afraid I am struggling to identify, what if anything, I changed to cause this. I have tried a number of Arduino Uno’s and all are the same. Any help appreciated.

At the moment I just want to get my router up and running using Easel through my MacBook Air. I have an old Dell with a BOB and drivers to enable me to try LinuxCNC as I enjoy the challenge.

Any recommendations as to a “sending programme”?

Resolved. Looking for the high tech solution and forgot the obvious, the Z axis was sticking and loosing steps, so not meeting the work piece. Although I had adjusted obviously not careful enough. Onwards and Upward, but not sticking!

How was it sticking and what did you do to fix it? I have yet to get a good complete detail cut after the rough cut… my z-axis started perfect this last time then as it went on, started to just cut air!

Having reflected on the reasons it all came down to my lack of care and attention. I had modified the gantry by fitting larger end plates. During that process I removed the Z axis. First error was not refitting the axis properly with the bottom bearing not fully seated in its holder. The second reason, and this should have been obvious, was that I had not adjusted the spindle on the Z slide, as I thought there was sufficient travel, which was not the case. The slide lowered and at its maximum apparent travel the top bearing plate struck the X travel drive pulley preventing further travel. The noise made that obvious but not apparent to me.
All this is in an OX machine but I hope it helps you.
All cutting fine although now have difficulty converting downloaded file to adjust for different material thickness but all keeping the brain active.(good for a 73 year old school boy)