Tool height measurement but part is in the way

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Black Forest
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Tool height measurement but part is in the way

Post by Black Forest »

I am trying to mill a part that takes up all but 5mm in all directions of X and Y. I only have three drill chucks. I need to drill four different size holes so that means I have to switch out a drill bit in one of the drill chucks. I have a tool height touch off probe but it cannot be used in it's normal place as the part covers that part of the mill table. I don't think I can measure the 4th drill beforehand as I won't be able to get it exactly correct in length when I change out the drills. My tool touch off probe is not fixed to the table so it can be moved. I use a hack to locate the tool setter. Just a sharpie outline around the base of the tool setter so I get it in the right place. I have a touch probe that I use to measure part Zero's. I touch of the touch probe on the tool setter to get my reference height. I really don't want to take the part off to measure the tool in the middle of a program. My mill is a 3 axis with the Z axis being the knee. Of course this will be a simple thing to you guys but to me it will be a head slapping situation. I have a lot of talents but CNCing ain't one of them I guess! :D
cncsnw
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Re: Tool height measurement but part is in the way

Post by cncsnw »

I have a touch probe that I use to measure part Zero's. I touch of the touch probe on the tool setter to get my reference height.
This means that your touch probe is your Reference Tool.

Since you have a Reference Tool, you can use it to set a new Z Reference on any surface you want, any time you want, in order to measure additional tools.

When you need to measure the 4th drill part-way through the job, you could:
1) Set the tool setter on top of the part
2) Set Z Reference with the probe on the tool setter
3) Measure the drill on the tool setter

Alternately, if it is awkward to use the tool setter on top of the part, you could
1) Set Z Reference with the probe directly on the part surface
2) Measure the drill by touching it to the part surface

Later, when this job is done and you want to revert to your normal procedures, you would just put the tool setter back in its usual place and set Z Reference with the probe on the tool setter.
cncsnw
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Re: Tool height measurement but part is in the way

Post by cncsnw »

Alternately, since the tool is a drill in a chuck, you could:
1) While setting up before the job, get an approximate offset by measuring the drill, with it extended 5mm or 10mm down from being pushed all the way up in the chuck.
2) When it comes time to use that tool in the job, put it in the chuck, pushed all the way up.
3) Command a move, with the drill's offset active (e.g. "G43 H4"), to a known point over the surface of the part (e.g. "G0 X50 Y80 Z0", assuming the part surface is zero at that XY location).
4) With the (shortened) drill sitting in the air slightly above the surface, and the DRO reading zero, loosen the chuck; let the drill slide down to the surface; and tighten the chuck.

In short, you would be matching the tool to the offset, instead of measuring the exact offset for the tool.
Black Forest
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Re: Tool height measurement but part is in the way

Post by Black Forest »

Thank you for the very clear explanation. That makes sense to me.
Black Forest
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Re: Tool height measurement but part is in the way

Post by Black Forest »

Thinking about this some more would it be acceptable to write down the Z reference height when it is in the "normal" position and then after moving the tool height setter to the top of the part and touching off with the touch probe on it and then touching off with the drill then just enter the original height offset in the tool library with the noted Z reference height when I am done with this tool? This part I am machining when mounted on the table covers the normal location of the tool touch off height setter. There is no place I can put it that I can get to with the part mounted on the machine.
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Re: Tool height measurement but part is in the way

Post by tblough »

When confronted with the problem of not enough oil holders, I split my program into parts. In the case of four drills, I'd make those a separate programs, and switch to another WCS with the same X and Y coordinates and manually set the Z for each tool.

I keep a 0.5000 gage pin handy for this. Change your drill bit, jog the tool down until the pin just clears and set your Z height to 0.5 or 12.7 without using a height offset (or offset 0).
Cheers,

Tom
Confidence is the feeling you have before you fully understand the situation.
I have CDO. It's like OCD, but the letters are where they should be.
Black Forest
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Re: Tool height measurement but part is in the way

Post by Black Forest »

I had already started some operations on the part when I realized the error of the fourth drill. In the future I will have enough drill chucks and tool holders so this won't be a problem. Today I actually cut off a drill with a grinder to be the same length as the other drill so I could exchange them without going through any hassles. For drilling it works as there is some leeway as to depth because I programed the hole cycle to go 3mm below the bottom height. I don't have any collars that I could use as depth stops. I first tried a sharpie but I couldn't see the mark. Old eyes! :(
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Re: Tool height measurement but part is in the way

Post by suntravel »

You can also measure the difference in the tool length and add/subtract it from the current tool offset.

If the bore is not very deep you also can use an endmill to enlarge a hole from a smaller drill.

Uwe
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