Checking fixtures - How to build it and are its dimensions the same as the part?

[Corine]

Hi,

I would like to understand the basics of a check fixture (how to build it and are its dimensions the same as the part?)

Thank you for your help.

Corine.

 

[ralphsulser]

Corine,
Hi and welcome to the Cove.
I suggest you contact a company that builds tooling and check fixtures. There are some in Canada near Toronto I think, but I don't remember their name at the moment. Maybe someone else will provide the info.

 

[Bill Ryan - 2007]

Also with the Welcome to the Cove

I'm not exactly sure what you mean by a "check fixture". If you mean a holding fixture to ease with measuring the part, they are usually constructed to rest on your datum sheme and would have nothing to do with the dimensions of the part (except with respect to your datum scheme). If you mean an actual fixture gage, I would assume you are checking positional types of stuff and the "checking" part(s) of the fixture would typically be MMC pins or some type of variable sweep mechanism.

With that said, there are gage houses all over North America (as well as the rest of the world) and I agree with Ralph, you should contact and sit down with a rep to ensure you get a "check fixture" which will give you what you need.

 

[Wes Bucey]

Hi,

I would like to understand the basics of a check fixture (how to build it and are its dimensions the same as the part?)

Thank you for your help.

Corine.

First, let me join my colleagues in welcoming you to the Cove!

For the sake of the folks in the peanut gallery who may not have seen or used the term, a "check fixture" may have slightly different definitions, depending on who is using it, but the essence is that the piece part being checked fits into or on top of the fixture (male or female fit) exactly, to readily check arcs, spherical surfaces, or other difficult-to-measure aspects of the finished piece (or to check a piece at an intermediate step.)

The check fixture concept is often used in the sheet metal industry.

My guess would be the direct answer to your question is the check feature is the exact mate to the features on the piece part which need to be checked. Smart fixture makers include a kind of mistake proofing in the design to assure the piece part can only be put into the fixture the correct way.

You've run smack dab into the closing weekend of summer and the Cove will probably have very little activity until Tuesday to get you more responses to your query. Check back with us Tuesday and add a new post to the thread to "bump" it to the top of the 24-hour cycle.

Keep the email alert this message brings you and you can click on the link in the message for direct connection to the thread.

If you have more information to give us about the reasons for asking and your specific industry or part under consideration, it will help us focus on a more specific response.

The folks who make these fixtures are usually pros, either in-house or specialty jig and fixture makers. A side concern is that the fixture may show you where the piece part does not conform, but not "Why."

A check fixture differs from a "jig" in that the jig is essentially a holding device to hold the piece part while work or inspection is performed; the "check fixture" is a form of gage.

 

[Jim Wynne]

A check fixture differs from a "jig" in that the jig is essentially a holding device to hold the piece part while work or inspection is performed; the "check fixture" is a form of gage.

Especially in automotive work, check fixtures, or "checking aids," as they are referred to in the PPAP process, often are a hybrid of the two. They can be designed to hold the piece for CMM inspection, for example, and include surfaces that correspond to the datums of the GD&T schemes or car positions on the drawing. The same fixtures might include indicators that provide direct variable measurement data for certain features.
There are companies that specialize in building these fixtures and they often work directly from CAD models and supplementary GD&T specifications. As with any other type of specialized precision machining, they are not cheap, so it's important to account for their costs in the RFQ process. In the automotive world, they are usually paid for by the customer and remain the customer's property, as with other tooling.