Measuring drilled hole location

[drafter16]

Hi all
Does anyone here have experience in measuring drilled hole location on a finished part? I included a picture of what I have in mind. The part with the drilled holes is what we make. We would like to use a linear encoder thats connected to a track that can be pushed back and forth. Just not sure what kind part(or device) to use that would be connected to the fixture.

 

[BrianE22]

Have you thought about a coordinate measuring machine (CMM)?

 

[SnTMan]

Yeah, measured lots of drilled hole locations on lots of parts. Used tape measures, steel scales, drill bits and rod, dial calipers, and other stuff, depends on the accuracy needed and quantity to be checked.

As seems to be so often the case these days, your screen shot does little or nothing to illustrate the problem. Pretty though.

Regards,

Mike

 

[drafter16]

Thanks. No, we have not talked about using a CMM. I will look into it. We need to measure a length of at least 102".

 

[drafter16]

CMM would be too expensive as we would need to build a room to control the environment.

 

[fegenbush]

You already have a linear encoder, just add a wobble center to check two sides of each hole. Average the two values to get the center dimension. Use multiple measurements to increase precision.

 

[drafter16]

I'm not sure what a wobble center is. But I think you mean an edge finder. This may work.

 

[KENAT]

"CMM would be too expensive as we would need to build a room to control the environment. "

Your measurements are affected by temperature regardless of whether you're using a CMM.

Now if you're building the fixture shown out of Zerodur & Invar maybe ignore what I said but otherwise I'm not sure of your reasoning.

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[1gibson]

Do you want to measure it, or do you want to make sure the spacing is correct? Make a fixture/gauge with pins to fit in the holes. 10 pins on the gauge, overlap a couple pins when you move the gauge (check holes 1-10, then holes 8-18, then holes 16-26). |___|___|___|___|___|___|___|___|___|

 

[IRstuff]

There are probably a ton of different ways that this could be done. Much depends on your required accuracy/repeatability. Since you have the linear track, a standard inspection camera with lighting coupled with a bit of image processing and the linear track position information would be employed. I think much of that can be done with Labview. There would need to be some sort of calibration of the positioning information.

The part's relative position to the track would be determined by checking some sort of fiducial that's tied to the part's mechanical datums. The track would step to each hole's location, and the hole's image would be centroided to determine its position and if you are using Labview, it would compare its list of correct positions and would give you a go/no-go indication.

However, it sounds like the holes are drilled by a subcontractor? Wouldn't it be better for you to get them to test and certify the position/size of the holes, since that should be part of their acceptance testing?

TTFN
faq731-376

Need help writing a question or understanding a reply? forum1529

 

[drafter16]

The subcontractor makes the tube and we drill the holes. We need to measure the location of the holes from the datum and not the diameter. Tolerance is +/-0.005". Thank you all for the tips.

 

[fegenbush]

"I'm not sure what a wobble center is. But I think you mean an edge finder. This may work. "

An edge finder is probably the proper (read: modern) term for the tool.

"Tolerance is +/-0.005""

This seems to be a complicated setup for such a loose tolerance. Also, what is the tolerance for the hole diameter?

 

[BrianE22]

Lower a tapered piece into the hole via a slide mounted on your carriage. Your carriage will move as required to center the tapered rod in the hole.