Where should PROGRAM ZERO be?

[max90272]

Hi guys,

I'm having a hard time understanding a very basic concept as far as CAM programming is concern in relation to actual cutting... I'm basically wondering where I should put my PROGRAM ZERO or PART ZERO. I always thought that it should be at a corner of the blank AT THE TOP, not the bottom but a friend of mine made a good point....

Let's say you program your tool paths (with your software of choice) to face a rectangular blank. In your CAM software you entered that your blank is 4" high and you program your toolpaths to face off .250" on top and the same amount at the bottom (after flipping it of course) to give you a finish part being 3.5" high.... ok so far so good...BUT... let's say that the blank in real life is not 4" but rather 4.05".... if I put my part zero on top, the finish product will not be 3.5" but rather 3.05" (although the software did its job)... Then I was thinking, ok I can put my part zero at the bottom of my part and the problem will be solved but I don't know if it can be done and how? What do people in the industry do in cases like these? Do they put the part zero at the bottom? if so, how do you do your tool offsets on the machine?

Thanks for all your help

Max

[CNCRim]

As you are the programmer, zero point can be whereever you assign the most important is the part come out good and your setup man must also on the same page as you are. Otherwise, desaster wait to happen, that's is why we have setup sheet to tell how to setup so coresponding with the program.

So, the foundation programmer have to establish and stick with it....... if anyone come a long and want to change or decise to. It will be a the whole mess.

For me, I like X-Y center of the part and Z on top of the part.

[mactec54]

Hi Max 90272

Your math is not quite right if your part was 4.050 & you remove .250 off each side which would be .500 total end part would be 3.550

If you want the part to be 3.5 you measure the piece before you do your program then if you need to ajust in the program just the last Z cut needs a change in the program to get the size you want

& Z0 or tool to work zero the top of the part is the best & safest place to put it

[max90272]

Mactec, you are correct about the finished piece not being 3.05 but rather being 3.55". Actually is what I meant.

Thanks guys.

I'd love to hear from other experienced programmers/machinists.

regards

Max

[mark c]

What I do is for op 1, specify the amount into the material z0 will be, although I don't take a lot off in the first op, but this doesn't matter much. For the second op, specify z=0 at the finished thickness. If you're not sure of the starting thickness of the stock, you can set the starting surface higher to enable an extra pass in case it's thicker. You can add block deletes to bypass this first pass if necessary. Be careful if you do so though, that you bypass information that might be needed if the block delete function is on.
Newtexas2006 is right, you and the setup man/operator need to be on the same page. I'm lucky; my Haas operator is very sharp and knows what I mean most of the time, but I still give him really good setup instructions; more info is better than not enough
HTH
Mark

[max90272]

Marc c,

If I understand correctly, your operator sets the z zero at the top of the blank unfinished, then proceeds with your first op, then stop the machine with optional stop and reset his Z zero on the finished surface, then proceeds with op 2? Would you repeat those procedures for the flip side of the blank?

thank you
Max