Setting Z height to not cut into spoilboard

Hello All,

I’m sure this question has been asked before but I’ve not had any luck finding an answer that makes sense to me. I read a detailed post but can’t find it a second time to post it here.

Anyway here’s the question:

What is the method to zero off your spoilboard (make it the reference plane) so that you only have to tell your model how high to lift the cutter…i.e. it won’t cut into the spoilboard.

This video from youtube explains what I’m trying to do with my Shapeoko and CC - Don’t Spoil your Spoilboard

I’ve given it a couple of tries but have not yet been able to get the effect of what I want. Anyone want to give me the secret? I’ve got several outlines of bunny rabbits on my temporary spoilboard I don’t want on my permanent spoilboard.

I’ve also used “bottom of stock” as suggested in this post…didn’t make a difference for me but I could have screwed up my test run by changing too many variables at once:

So anyone have a good article explaining this because I’m just not getting it…

Here is how I address this subject on my cuts:

  1. I use “bottom of stock” setting in CC on any through cuts, especially my final profile.
  2. I set my stock thickness to whatever it measures at the thickest point, but try to surface my stock first so that it is parallel.
  3. My Z retract height is set based on what it takes to clear my highest point, usually the bolts holding my clamps.
  4. On the toolpath/s that are through cuts, I set it .010 less than my stock thickness to avoid cutting my spoil board. If my stock is .500" thick, I would set my toolpath to cut .490".
  5. When setting up my tool I place the touch off probe on the FLAT (surfaced) mdf spoil board, and then run the z axis probing cycle.

An alternate option is using a secondary spoil board for parts that you want a true 100% through cut. I use a piece of peg board with extra holes which match up to the threaded inserts in my spoil board.
I hope this helps and doesn’t confuse you.

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Thanks for the reply — I will give it another go…if not…I think I might just pick up some peg board though I do have to master this…through cutting with the CnC reduces finish time drastically and I have 5 rabbits my wife wanted to sand :frowning:

I have a metal table, and I never want to cut into it, but cutting wood is probably the greatest opportunity to cut into my table because wood isn’t flat, and varies in thickness.

First, let me tell you that my table is flat, very flat, so here I use the KISS method.

Let’s say I have some 3/4" wood. I set my tool to zero on the table. I then raise it 3/4" PLUS 0.010". That’s it. When the cut is made it will never touch my table (or waste board), because it was set 0.010 higher.

There are variations all more complex, but I really like the KISS method. Four years of using it everyday and my table is still a virgin.

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Hey Richard,
So your still using zero at top of stock? Set tool to zero on wasteboard - meaning actually zeroing it out at this point? Then raise it up 3/4 plus .010" according to the zero scale or measurement - then reset zero?

I’m pretty sure he sets the actual zero 0.01" above the wasteboard
most cam software has a setting for this so that the gcode you generate is aware of this…

Yes and yes exactly.

Close. I zero it off my baseplate (well, using a piece of paper), then I ask myself, how much onion skin do I want. (It varies on the material and what I am making), once I have that number (onion skin) I then raise it that amount PLUS the material thickness…then I zero it (just once).

My Z0 is still based off the theoretical top of the part (not the bottom)

I was getting pretty frustrated because of not getting accurate results over and over again. I ended up running test holes off the stock before running operations, it would usually take me about 3 holes or test runs to get it to just where it was skimming the wasteboard, - no surprises then!

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