Advantages/Disadvantages to where you Zero the Z

[nomi]

I have a question for folks.

Some of the ShopBot files I have been looking at, zero the Z on the table of the shopbot instead of the level of the material you will be cutting.

Is there an advantage to doing this? I'm still learning so I thought I would ask


- Noel

[jerry_stanek]

If you zero to the table and you say your material is .75 thick and your material is only .72 and you tell the file to cut .75 when it gets to the table top it should not cut into you spoil board. But if you zero to the top of the material and set your file to cut .75 and your material is only .72 then you will be cutting into the spoil board .033. Hope this helps.

[bob_s]

I agree with Jerry, Z zero on the table when you are cutting parts. But I find it necessary to Z zero on top of the material when I'm V carving, fluting, or doing anything else where more than a few thousands difference will be a problem. I find this confusing, and mistakes are disastrous, so I now put "top Z" in any file names that were set up that way, and assume all of my other files are bottom Z. I don't have a vacuum setup, so it's possible that the switching is not necessary if you have one, you carefully check all stock thickness, and your stock sits down very evenly to the spoilboard.

[bill.young]

Hey Noel,

I hate to have to accurately measure the thickness of each sheet of material so if I'm doing something that's at all precise I make the decision by what features are important...how much material I'm cutting away or how much is left. For instance if I'm cutting a series of slots and I want them to be exactly .25" deep, then I zero at the material surface and they'll be the correct depth even if the material is a little thicker (or more likely thinner!) than it should be. I always zero at the material surface for v-carving.

On the other hand if I want to leave a .25" thick tab on a piece then I zero at the table surface and I know that the tabs will always be .25" thick no matter how thick the ply is.

If neither of these matter, your material thickness is consistent, or you don't mind measuring each sheet and creating files for that thickness, then I tend to zero at the table surface so that I don't cut too deeply into the table if my material is a little thinner than I expected.

There's no wrong way, though..whatever works for you.

[nomi]

Ok, that all makes a lot of sense.

Thanks guys


- Noel