[Metrology] What Instrument to use

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CoPie

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Hello all,

I have done a lot of research on the topic, but I am still unsure how to solve my problem.

What I am trying to do:
Measure the alignment of the end effector of my machine with a hole. So the machine would be moved above a hole, the operator using her own eyes, and then the operator would identify how well positioned the machine end effector has been placed above that hole. I do not get force feedback from the machine. The hole is somewhat rough. My machine can use tool that fit on milling machines.
The end effector cannot rotate. Cost is also a important element.

What I have explored:
-Dial Test Indicators: requires rotation, measure along only one axis (1D).
-3D sensor: expensive solution
-Center finder: simple, cheap, might break when moved downwards. How to give a value for the alignment??
-Other sensors (vision based): expensive, difficult to integrate

What is the best options? Are there alternatives to the tools stated above? Do 2D dial indicators exist?

Many thanks for your inputs. Let me know if I can clarify certain points.

Best regards

CoPie
 
Could you mount a rod with a cone shape on the end, and using the cone, locate the (rough/approximate) center of the hole?
 
I think It's important to know the tolerance of the location before deciding on a solution. How accurate does it need to be?
 
T Bredehoft said:
Could you mount a rod with a cone shape on the end, and using the cone, locate the (rough/approximate) center of the hole?
Click to expand...
thx for you reply
I think that would be possible. But the question becomes then:
How to measure how well that cone is in the hole, the concentricity of the rod with the hole?
 
ConValSam said:
I think It's important to know the tolerance of the location before deciding on a solution. How accurate does it need to be?
Click to expand...
thx for your reply
I would say it is in the order of the mm. I reckon up to 1-2mm.
 
For accuracies on the order of .3 to .5mm, the cone described by Tom would work. It works best if the work is free to move. I would seat the cone firmly in the hole and then clamp the work. It is a little more difficult if you have to move the table as it becomes a judgement call as to when the the cone is fully seated.

I made up a laser center finder that uses a circular pattern to better identify the edge of the hole. The laser is mounted off the center of the spindle axis so when spindle rotates, the laser traces out a circle that is concentric with the spindle axis. The pattern works equally well for holes, bosses or scribed circular patterns. The laser pattern is most accurate when it is slightly different from the feature diameter so I made mine adjustable by using my boring head for mounting the laser. https://www.hobby-machinist.com/thr...n-your-shop-today.14637/page-1088#post-553286

For accuracies on the order of .01 to .1mm an edge finder or an Indicol with a dial test indicator mounted on the spindle will accurately find the center of a circular hole or boss. They work well because they are independent of any runout in the spindle or chuck, indicating the true center of the feature. https://www.janesvilletool.com/C/114/Indicol
 
Given that tolerance, I would make a plug that is a snug fit in the hole and scribe or engraved a cross hair on center and then use a pointer in the machine to align to the cross hair.
 
CoPie said:
What I am trying to do:
Measure the alignment of the end effector of my machine with a hole. The hole is somewhat rough.
Click to expand...

If you know the desired location of the hole, say 20mm from one edge and 15mm from another, then a simple edge finder will allow you to use your X-Y hand wheels to pretty closely center the spindle over the hole. It would not matter if the hole is rough; it only matters if you have the desired X-Y coordinates.
 
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