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PostPosted: Fri Feb 19, 2016 9:23 am 
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Walnut
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Hello everyone, I'm curious to know whether you zero your Z axis to the table or top of the material you're milling and why? I've been setting my cam program and machine to the top of the material from the start, but I believe that I can benefit from changing that to the table spoil board. I've skimmed into my table because of inconsistent sized boards that cause my Mill to take 20 thou's off the spoil bd. If I set my z to the table top using a touch probe and script , then add an additional operation to face the top of the material before milling it I believe I would have more consistent results. I have a Z touch probe coming in the mail so I'm glad to get that added to the mill. I'm using Mach3 and Vetric's Cut2D and Cut3d. I greatly appreciate all advice, Vince


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PostPosted: Fri Feb 19, 2016 9:37 am 
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As a long time machinist and programmer, I can tell you definitively - depends on the job. There is no hard and fast rule.

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PostPosted: Fri Feb 19, 2016 1:29 pm 
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Chris is correct.
Examples:
1. When surfacing a part to a specific thickness, or when machining a fretboard, you should definitely use the top of your fixture.
2. If you're cutting a pocket in something to a specific depth, then you need to go from the top of the part for more consistent results.

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PostPosted: Fri Feb 19, 2016 3:26 pm 
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Cocobolo
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What Chis and Don said.

You just have to think about what you are trying to accomplish and where the critical dimension / tolerance is that you are striving to achieve.

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PostPosted: Sat Feb 20, 2016 1:34 pm 
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Cocobolo
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+3 when we machine pickguards we zero off the part for the screw holes and countersinks and then zero off the fixture to machine the edge chamfer


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PostPosted: Sat Feb 20, 2016 2:42 pm 
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Quote:
+3 when we machine pickguards we zero off the part for the screw holes and countersinks and then zero off the fixture to machine the edge chamfer


PERFECT EXAMPLE.

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PostPosted: Sun Feb 21, 2016 12:52 am 
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Walnut
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Every job I do is zero'd different, so I'd tend to agree with the previous posts.


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PostPosted: Wed Mar 09, 2016 9:34 pm 
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Walnut
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Thanks to everyone for your replies, I can see why you would do it each way with the examples you mentioned. Very very helpful. regards, Vinny


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PostPosted: Thu Mar 10, 2016 12:39 pm 
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It's really just a matter of determining what matters and what doesn't matter with regard to precision. Your machine doesn't care where its zeroed at...it's your preference.

I usually (not always) use the bottom of the tooling jig or jaws for everything because, with a tool changer, I can set up the whole job so I just run the first first op, flip the part over, and run the second op, and so on until it's done.

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PostPosted: Sat Mar 12, 2016 7:36 am 
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I zero off the spoil board. I don't have to change it so zero is always the same unless I have to re-surface the spoil board. Forgetting to set a new 0 when changing jobs can lead to some scary tool plunges. Ask me how I know. oops_sign

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PostPosted: Tue Mar 15, 2016 1:44 am 
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Koa
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I like to zero on top of the part when I can. But when I need to thickness the part it has to be the spoilboard. The reason I like the top of the part is because then I can "go to Zero" where I have marked so I can see if I have missed steps or something has gone wrong. If you go to zero and your z is below the part it is a disaster with the bit routing through your part.

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PostPosted: Tue Mar 15, 2016 1:57 am 
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Koa
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oops dp
[uncle]

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