I’ve made some progress tonight.
I used some thicker 12mm plywood, clamped it down tight and put a few screws in strategic spots.
Probably should have used a solid board underneath?
I worked out while it was milling the holes that it was resonating in the steel tubing.
Stuffed a piece of foam in there dampened it.
I also noticed some slop in one of the top bearings on the Z axis, I need to reprint one of the brackets as its got a small crack forming.
The other thing was that when it broke through, it really plunged through… like dropped a couple of mm and I really had to slow things down.
Suggests to me that the Z axis isn’t making its depth on each pass.
So I’ll look at adjusting the Z axis driver – properly.
Feedrate is: 20mm/s XY and 10mm/s Z
I’ve been slowing things done to 50% or lower when the wheels start to fall off.
So I’ve got plenty to look at now and making progress.
Thanks for the help everyone.