# Zero at bottom of stock

Hi,
I am trying to create a program in CC that faces uneven stock to certain thickness then cuts pockets and other features in it.

I’m a bit confused how to implement this in CC and if it’s even possible. I have uneven stock around .75" and want to face it down to exactly .625", then proceed to cut pockets in it down to a certain depth. In my setup I set my zero height at “bottom”, yet that doesn’t seem to have any effect on depth values which appear to work always relative the top of stock.

IOW, is it possible to write a single program with multiple tool changes that starts with a block and ends with finished product without having to redefine the Z position along the way. I thought that setting zero at top of waste board would be able to accomplish this, but all depths appear to be relative to stock not absolute to waste board in CC.

Is air-cutting okay?

Define the stock as 0.75" (or whatever your thickest piece is) and surface that off, then begin the actual machining.

I’ve no issue with air cutting for now, but since simulation only shows the end result and I don’t have access to g-code, I can’t tell if zero is at the bottom and all Z values are positive.

What I will do to test it is set my stock to .825" and allow my facing program to go .200" deep, then change tool and see how the pocket cuts. I must assume that the program is smart enough to know what its new top of stock is after facing and creates a pocket of the assigned depth from that point.

Once you set your Z to the bottom you can confirm the Z settings by looking in the Carbine Motion settings. Just make sure that you have your stock thickness zero height set to bottom.

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Your assumption would be false… But YOU know where the new top of stock is, so just set the Start Depth on the rest of your paths to 0.200 (0.825 - 0.200 = 0.625), and the max depth relative to your 0.825 stock thickness.

I would do two jobs. Do the surfacing and then do a separate job with the actual project. Since your stock is rough make your rough stock thickness the highest level. Then let it cut it down until it gets to the level surface you want. Then start your real project and set your material at the .625"

This will make your life simpler.

It does not matter if you use top or bottom of material in job setup. The stock thickness accurately measured is critical. In this case you have to figure the thickest part of your material and use that as your stock thickness. Then when the surface is flat start the real job.

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Tod1d & gdon,
Yes, I just realized that having let the program run all the way through just now. Watching the Z values in Carbide Motion told me that all were indeed positive as expected, so zero was at the bottom. Clearly, the program doesn’t update it’s top of stock for subsequent toolpaths. I’m hoping that the trick of telling each subsequent toolpath that the new top of stock is where the facing finish pass was will do the trick, e.g. I faced from 0 to .300" depth and now my pocket will start from .300" top of stock to .700" depth for an actual pocket depth of .400". I’ll try to run it with these edits and I’ll report back.

Edit: I just realized this is exactly what Tod recommended. Thanks.

All is good. The solution above worked like a charm. Thanks all for help.

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