Measurement Method Challenge - Measure feature #91

[Ron Rompen]

I have an exceptionally difficult measurement task, and am hoping that someone here will have some suggestions as to how to solve my problem.

On the print extract shown below, I need to measure feature #91. As you can see, this is not as easy as it first looks.
My current method is to measure with a contour tracer, however that requires the operator to leave the production area, come to the lab, wait to have the part measured, return to production, make adjustments (if required) and repeat to validate....all in all, not a very suitable method.
I am looking for something that would (relatively) simple for an operator to use on the floor. I have contacted several gauge makers that I have dealt with in the past, and none of them have any useful ideas.

Any suggestions?

 

[GRP]

In my days as quality engineer in the plastic injection industry I always fancied having a Renishaw Equator. It is sort of a CMM for the shop floor. It would have made my life easier. Do understand that if you go and buy one I'll receive doodly-squat.



Here is a possibility, if I interpreted the drawing correctly: make a fixture to pass through the center hole, seat the part horizontally and measure on top with an indicator. To seat the part have some sort of pins machined to follow the radius.

 

[Ron Rompen]

GRP: Thanks for your response, We have several CMM's with a variety of measuring heads, but the feature is too small to accurately measure in this method. YOur other suggestion (to seat the part on the blend radius and measure 'down' from the top has somewhat the same issue. The blend radius varies in size, and this change has a direct impact on the Feature 91 measurement.

Thank you for your input though, I do appreciate you taking the time to respond.

 

[John Predmore]

In addition to the shop floor CMM that @GRP mentioned, I know there have been a lot of advances in non-contact measurement instruments. I was always suspicious of the precision and repeatability of optical devices, in which accurate measurements in the Z dimension is a function of focus and lighting, there are now affordable, very precise instruments which use laser light. If you can see a surface inside a hole, you can measure it. I am no expert, but you may wish to explore these as a solution.

 

[Ron Rompen]

Thanks for your response John. I too am suspicious of optical devices for this type of measurement, however I have started exploring the potential of using a laser to measure the location of the feature.
The blend radius between feature 66 and 75 is what makes it so difficult - there is no clearly defined transition zone.

 

[Genaro Luevano]

my suggestion as this is a difficult to measure use a go no go gauge for the area using the max indicator, because measurement every time will be quite complicated

 

[GRP]

my suggestion as this is a difficult to measure use a go no go gauge for the area using the max indicator, because measurement every time will be quite complicated

Are you suggesting a go / no-go gauge will be apt to control a feature which cannot be accurately measured with CMM?

 

[Ron Rompen]

GO/NOGO gauging for this feature is (virtually) impossible, due to the feature configuration. In addition, the dimension is critical enough to part function in the assembly that (although it is not designated as an SC/CC) I want to be able to monitor it for process shifting.

 

[Ninja]

If a laser profilometer wont work for you (I'm thinking along the lines of the old OGP Flare laser add-on)...does it make sense to make your own go-nogo fitting the internal hole and slope? Then measure protrusion from the other flat side?

If what you are looking for is process shift, this should catch it. Not a direct measurement per se...but should give you data you don't currently have...

Just thinking out loud...

 

[Genaro Luevano]

another method will be with a height gage from the

If a laser profilometer wont work for you (I'm thinking along the lines of the old OGP Flare laser add-on)...does it make sense to make your own go-nogo fitting the internal hole and slope? Then measure protrusion from the other flat side?

If what you are looking for is process shift, this should catch it. Not a direct measurement per se...but should give you data you don't currently have...

Just thinking out loud...

thats what i talk about do the go-no go use as a base and then measure, take the practical aporach