Hello, my lead 1010 doesn't always cut through- sometimes its a whole board but usually few places only. I'm using z-probe (19.7) and have used flattening wizzard. I also set the depth cut higher than the thickness of the board (18.35mm and board is 18mm). Is there any other way to make it work?
Is it consistently the same places? Seems like a) your spoilboard is warping after flattening, perhaps due to humidity, b) your machine simply isn't straight and you need to spend some time squaring and tramming, or c) you have some z-axis issues- nut tightness, backlash, etc. The nature of the problem should theoretically tell you what's wrong. Can you put a straightedge on the spoilboard in any direction without seeing daylight through the gap? You could also do some toolpath testing- do some multiples at say, 1mm, 5mm, 10mm and 15mm. Are they all accurate?
What if the stock at the corner is say 18.5mm. You zero based of probing that corner... And then assume it to be 18mm. No stock is ever consistently the same thickness all over the sheet. Use the spoilboard, as exactly that. A board to Spoil. It is a long term consumable. Cut 18mm stock with say 19mm so it cuts through for sure. Here where I am 19mm ply is somewhere between 17-22mm spread over the sheet - very inconsistent
The other thing, if the spoilboard is flat and the machine is square and tight, is to zero Z off the spoilboard, not the material. As Peter says, the thickness of sheet materials can vary significantly- I've literally seen 5/8" plywood in the store with one half of it with an extra ply in to make it 3/4" for no apparent reason- so zeroing off the top of it doesn't define anything. The only thing you can zero off the top of with any meaningful precision is something you've already surfaced down.