Apply proper GD&T for "Keep In Zone"

[rattler1975]

My issue is that I'm not 100% sure how properly dimension a "keep in zone" using GD&T.

This should be simple for someone who does this all the time... I however am not that guy.

Originally we set up the dimensions on a source control drawing as two MAXs and one MIN dimension. The idea was this defined a theoretical boundary the part had to sit in. Parts came in and they couldn't get a good measurement (some measurements were greater than 70°) so a functional gauge was made. The quality engineer said they couldn't accept the parts because the parts could have an angle greater than the 70° MAX.

I put together a slide that hopefully explains my issue in more mathematical details. Personally I'd just like to slap a flag note on each of the MIN and MAX dimension that states something like, "this dimension forms a virtual boundary condition used for a functional gauge." Or something along those lines. But I'm aware that this may not be the correct method...

I appreciate any help I can get.

 

[3DDave]

You didn't specify what the part is supposed to do. The initial spec indicates that the part could be of zero size, once the .64MAX is dealt with.

Without that, there's no telling what a correct response would be like.

 

[rattler1975]

Think of it as a keep in zone. This is part of a cable strain relief that goes into a device that has items all around it in a non linear 3D space. In theory the smaller the MIN dimensions the further away we are and the better. The true limiting factor is the fact that there's a cable under the strain relief and this dimension is .250.

 

[rattler1975]

This is what I was envisioning...I believe it's a solution. The idea is use a unilateral no datum surface profile...

I guess I could make a "no go" gauge...

Agree?

 

[Belanger]

Maybe profile in conjunction with position (where position would be of the "boundary" type). If you have a copy of the Y14.5 standard, see page 171 of the 1994 edition or page 176 of the 2009 edition.

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

 

[pmarc]

Looking at the solution...
- What controls total width of the zone? As far as I see one basic dimension is missing in that direction.
- I am not sure I fully understand the description given, but as it is shown now the minimum total height of the zone can be .240 = .640-.200-.200. How is a dia. 250 cable going to fit inside that zone?