Offset from bottom of stock

I typically use double-sided wood-workers tape for my hold-down and it works just fine for me. However, I have to lie to Carbide Create as to the thickness of the stock because I also use bottom of stock measuring. This is mostly due to wood (the primary material I use) is not only not the thickness specified, even for those that are planed to a specified thickness, but also not consistent. I’ve measured up to 0.05" difference from one side of a piece to the other, What I’d like to see is, when using the bottom of stock setting is an additional offset where I can specify the thickness of the tape. In this way, my design and simulations look correct and the cutting would go only as low as the real bottom of the stock. This would also be useful if one were to use a temporary wasteboard with a piece screwed into it (or other fastening methods) without damaging the machine waste board.

I’ve yet to have to replace my wasteboard as the bit never gets to it. On the other hand, I’ve forgotten a couple of times to “lie” to Carbide Creature about the thickness of the material and have had the bit bite into the tape, which makes a mess. Obviously, providing an offset wouldn’t help the forgetfulness part, but that’s my problem.

So, to put it a bit more consisely, I’d like a way to enter the offset from the measured bottom of stock (the top of the wasteboard) to the actual bottom of stock when bottom is selected in the zero-height setting of the job setup dialog box.

How thick is your tape? 0.004" - 0.005" ??

You could just touch off to your wasteboard, and enter -0.004 for Z, rather than click the “Zero Z” button.
Now your Z zero is 0.004 above the table. :wink:


Or, just put a piece of tape on the wasteboard and measure there.


Yes, both of those solutions would work, but they are much more workarounds. The tape I use (XFasten woodworking double-sided tape) is 0.010" thick and pretty consistent. I cannot use that tape on the wasteboard for measurement because it is double-sided. If I leave the liner on, that alters the thickness and everything is off again.
I like Tod’s suggestion better for the workaround, but would sill like to see an offset field setting when selecting bottom of the stock for Z-zero. Where does one do that? I don’t see it in Carbide Create when defining the stock. Or is this done in Carbide Motion?

I wonder if it’s a rabbit hole… Where do I put the thickness of my Oramask? Or the 7 coats of finish I just added…?

It’s not a typical feature of any CAM software I’ve seen. That’s why zero points can usually go wherever you want. Although CC is the only software I’ve seen that limits XY to 4 geographic locations around the workpiece.

Either set your zero to the bottom of the workpiece (wasteboard + 0.010), or add the 0.010 to your stock thickness. i.e. it’s either part of your setup, or part of the workpiece. It’s entirely arbitrary how you want to look at it. As long as the toolpath lines up with your zero at the right height on the machine.

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Tod, you may be right. Where do I set the zero to other than the top or bottom of stock? Those are the only two choices in Carbide Create. I’ve been adding the 0.010" to the stock thickness, but that messes up the simulation so I don’t see where things are really cut through.

If you want the bottom of the simulation to look right, then set the job up normally with actual thickness & bottom of stock. Then make up the difference on the machine. Either Will’s suggestion of zeroing to the top of the tape, or if you’re confident it’s always 0.010 thick, touch off the table & set zero to -0.010. Or touch off the table, set zero, move the tool up 0.010, reset zero. (All achieve the same thing, setting zero to the bottom of stock like you did in CC).

If your part is sitting on 3/4" MDF blocks (that are actually 0.750) but your part hangs over so you can’t reach the blocks you’d do the same. Touch off the table & set Z to -0.750. (Or touch off the block before you set the part on it.) Your part can be anywhere within the machining envelope. All that matters is that you set the Zero on the part the same as you did in the CAM system. :wink: