how does setting Z=0 affect how deep the cuts are?

[Chelmite]

I'm trying to make some cuts in some wood where the depth of the hole, with respect to the bottom of the board, is critical. That is, the bottom of the board has been leveled. The top of the board is close to level, but not exactly level, but that doesn't matter to me because most of it will be carved away. However, for some counter-sunk holes that I will be cutting, I need the uncut thickness, from bottom of the board to the bottom of the countersink, to be an exact height.

How do I set up and specify the desired thickness of the material at the bottom of the countersunk holes? I assume that I will be setting Z=0 to be the top of the sacrificial board. If I have a roughly 1.5" thick board and want to have 1/2" of wood remaining, do I specify the depth to be 0.5" or 1"? Or, when I specify the material's thickness, even if I set Z0 to be the bottom of the board, are all the calculations, such as depth=0.5 with respect to the material's ideal top surface?

Thanks for you help,
Chelmite

[TReischl]

You got the right idea with setting zero at the surface of the spoil board.

All of the cutting depths are entered from the surface of the material. So even though your board is not a perfect thickness, pretend it is. In your example, tell it the board is 1.5 thick and you want to cut a 1 inch deep hole. That will leave .5 on the bottom.

[FixitMike]

If you specify the material as 1.5" thick, and set the cut to be 1" deep, then you will have .5" below the bottom of the hole. (Obviously) The trick is to set your Z0 at the table surface, then raise the router 1.5" and reset the Z0, rather than setting your Z0 from the top of the material. Now the cut will stop .5" from the table.

[PaulRowntree]

If you specify the material as 1.5" thick, and set the cut to be 1" deep, then you will have .5" below the bottom of the hole. (Obviously) The trick is to set your Z0 at the table surface, then raise the router 1.5" and reset the Z0, rather than setting your Z0 from the top of the material. Now the cut will stop .5" from the table.

Mike, I was with you until after the (Obviously). What is the point of raising the router then reseting Z0 ? As Ted said, the bottom is precisely on the table, so set Z=0 there, and tell Aspire some approximate value for the thickness, and program the pocket to go to a certain depth, relative to that fictional top surface.
The approximate thickness should be slightly more than the actual thickness for safe motion above material; too much more and you will be wasting time with air cuts.

[dealguy11]

I'm with Paul on this. No need to move z0 from the table top - works fine that way.

[Leo]

Normally ----- We normally set the "Z" zero as the top of the material. BUT - that is NOT a hard and fast RULE. It is just what we normally do.

In the case of normally - all cuts into the material will be at a "Z" MINUS number. So normally - if your material was 1.5 thick and you wanted a .5 material under a counrer bore your POSTED code would be cutting at a MINUS "Z" or Z-1.0

So - what you want to do is OK - nothing at all wrong with what you want to do - nothing wrong at all.

YES - by all means set your "Z" zro on the bottom of your material - the top of the spoilboard.

AND - ALSO - go to Aspire and set your "Z" zero as the bottom of your material.

edit in -- REPOST your Code --- you MUST do this !!!

NOW - what will happen is that the bottom is the datum reference point and all you cutting will be in the "Z" PLUS numbers.

You counterbore will now be cutting at PLUS .5 or Z.5 and the top of the material will be facing at Z1.5

You do not need anything else

[FixitMike]

[quote="PaulRowntree"]What is the point of raising the router then reseting Z0 ?

Paul: I erroneously underestimated the intelligence of the Vectric programmers. I assumed that if I set the Z0 at the table, I would have to compensate all of the toolpaths upward so they would be in the material. Just as I would have to if I was programming directly in the G codes. Instead, when I tried it, the program reset the home position to the top of the material and all was fine.

I would like to point out that anytime you set Z0 at the table, you risk making air cuts or burying the tool if the actual material height varies very much from what is specified in the program.

[ssflyer]

Chelmite,

As others have said, simply Z-Zero to the spoilboard. As far as "normal" settings for Z-Zero, I don't think there is one - it all depends on what you are doing. I always zero to the top of the material for V-Carving (after making sure my top surface is flat) and for relief carvings. However, I always zero to the spoilboard when doing sheet stock. That allows all my dadoes and rabbets, for instance to be precise. It also allows me to cut through sheet goods without cutting into my spoilboard.

In your case, set your material thickness a little over the thickest part of your material.