Part Fixture Certification

[kabby35]

Hi All,
Here is my question...
I now work for a company that builds Part Fixtures, my job is to certify them... I have been provided Cad models from FCA for example, which contains everything I need to write the program... Can I pick and use the bushings in the base for my initial alignment, then pick up the ABC datums for my DCC iterative and continue checking feeler/flush and so on?

Thanks in advance

[Matthew D. Hoedeman]

that's how I would do it. However, in a build/certify situation like yours, you may have to:

1) Pick up the bushings (align)
2) Pick up the part ABC datums (align)
3) Measure all feeler/flush checks. If in specified tolerance, dimension the bushings to update them to the values from the ABC alignment
~~~~
3a) Measure all feeler/flush checks. If not within specified tolerance, do a best-fit 3D alignment of ALL features. If all are in tolerance, then dimension the bushings to this alignment to update the values for the fixture.

[kabby35]

Thanks Matt!

[marcc]

Dimensional reports which we are getting with fixtures always have measured values of 3 tooling balls reported first so I am guessing they align to tooling balls and after that measure locators and everything else.

[Matthew D. Hoedeman]

Dimensional reports which we are getting with fixtures always have measured values of 3 tooling balls reported first so I am guessing they align to tooling balls and after that measure locators and everything else.

They go back after they have measured everything, and report the 'updated' values. You don't have to have the dimensions with the features, you can measure everything, align to everything (except the t-balls) then report the t-balls and everything else after.

[marcc]

They go back after they have measured everything, and report the 'updated' values. You don't have to have the dimensions with the features, you can measure everything, align to everything (except the t-balls) then report the t-balls and everything else after.

I just looked at 2 reports for different fixtures and it looks to me that company we are dealing with do whatever works best for them during inspection. 4 -way locator from first report has zero deviation in 2 axis, 2-way locator has zero deviation in 1 axis. On second report both 4-way and 2 -way are showing deviations in all 3 axis.

[Matthew D. Hoedeman]

I just looked at 2 reports for different fixtures and it looks to me that company we are dealing with do whatever works best for them during inspection. 4 -way locator from first report has zero deviation in 2 axis, 2-way locator has zero deviation in 1 axis. On second report both 4-way and 2 -way are showing deviations in all 3 axis.

Yep, that's how most of them do it these days, 3D best fit of all part locators and hand checks (stab, feeler, flush), as long as they can get them within the specified tolerance from the customer, they make no changes, then they map out the location of the t-balls, or bushings in the fixture base, and put those values on the fixture base for other to use for pickup.

Long gone are the days when the fixture base was flat and square, and they would then move/tweak/adjust all the mounted details to get them 'right'. The Iterative and 3D best fit alignment killed the 'square & true' fixture builders.