Help with zeroing tooling for finnish pass

[swmarsh]

Hi guys,
I was wondering how to zero the tool when The g-code askes for a tool change for the finnish pass after the rough passes. Not sure If I am making this clear enough. When I cut out a dish cut ( Rough pass )It clears all the material where the finnishing pass cutter does not have to work as hard, There is no where for me to take the tool tip down to so I can zero it out. On my finnishing passes it just cuts air. Whats the procedures? Do I try to get the bits the same distance from tip to collett on the spindel?
Thanks and sorry for the stupid question.
Steve

[JamesB]

Steve,
if I understood correctly you machine away the part where you zero the tools so have nowhere to touch the finish tool off. Probably the best suggestion (in my limited world) would be to change the XY datum position to be in the lower left corner instead of the (default) center then you should still have the material to touch off after the roughing. Or if the material is flat you should be able to touch off a different part of the material for all your tools and still use the center if you want? Hopefully this makes sense - if not please ask more.
James

[Andy]

If you're wanting to finish a piece that's already had the roughing cut done, you could re-generate only the finishing pass with zero set for the bottom of the workpiece. (top of the fixture), then zero your finishing tool off the fixture rather than on the now non-existent top surface of your workpiece.

Or, could you possibly use another un-cut piece of your material that is still the original thickness, place it on your fixture off to the side so you can zero on it's top surface?

[RoutnAbout]

After I find and set my Z zero, then I jog either in the X or Y until the tool just misses the job and then touch off the table, and write that distant down from the top of the material.

[Turtle49]

Another option for zeroing out after roughing away all the material would be to have a piece of scrap that is the same thickness as your original blank. Zero off of the top of it.

Although I have never run into a situation where I cut away the entire top surface of a blank....

Hope this helps,
Tim

[Andy]

Another option for zeroing out after roughing away all the material would be to have a piece of scrap that is the same thickness as your original blank. Zero off of the top of it.

Gee, I wish I had thought of that. lol

[js11110]

What I use is a planer gage. Its like a adjustable parallel. I touch off the tool, move the tool outside the part and adjust the planer gage until it touches the tip. Sets the height for a tools that follow. Here is a link http://www.auto-met.com/subtool/stcat/st_pg13c.html

Jason

[lovebugjunkie]

When I did my first 2.5/3d cut with a bit change I never could get the z height quite right sometimes, I then made a “zero height tool” out of some scraps I had and have never looked back.
Quick, easy and always the correct height. Couple versions running around on the forums, (CNCzone, Mach3 and this one.)

Most times I have a “border” that I can still use or the method the Turtle49 suggested.

http://www.cnczone.com/forums/showthread.php?t=36099

[swmarsh]

Thanks Guys,
You are all awesome in my book. That hit the spot.
Thanks again
Steve

[AngelicDiablo]

If I cut a piece that I know will not have room to zero off of when done with the roughing pass, I will zero off the table. So I would create a toolpath for my roughing and finishing passes to zero off the top of table. -AD