Composite Position - Secondary datum axis repeated in FRTZ

[powerhound]

Hi everyone,

We have a dilemma here and I need to either be corrected or backed up. Attached is a simplified example of what we're dealing with. My stance is that since datum B is an axis, there is really no orientation refinement possible, thus the datum B reference should be removed from the FRTZ. Am I just not seeing something? I know there are missing dimensions on this sketch but that doesn't detract from the issue.

Powerhound, GDTP S-0731
Engineering Technician
Inventor 2010
Mastercam X6
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

 

[axym]

Powerhound,

You're right, the B reference serves no purpose in the FRTZF. The only rotational DOF's that B can constrain have already been taken by A.

Evan Janeshewski

Axymetrix Quality Engineering Inc.

http://www.axymetrix.ca

 

[pmarc]

Yep, B adds no value for FRTZF.
Such composite callout would make sense if axes of the pattern holes were nominally perpendicular to datum axis B, and not parallel like in your case.

 

[powerhound]

pmarc,

What if the holes were actually obround? If the holes along the X axis were obround along the X and the Y axis holes obround along Y so that the centerplanes are now what is being controlled, would that make a difference? It still seems that refinement of orientation to the B axis is futile.

Powerhound, GDTP S-0731
Engineering Technician
Inventor 2010
Mastercam X6
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

 

[pmarc]

That wouldn't change anything.

 

[powerhound]

I didn't think so but your comment about the axes being perp to B made me think that there might be something special about a slot that I just wasn't aware of.

Thanks for the confirmation,

Powerhound, GDTP S-0731
Engineering Technician
Inventor 2010
Mastercam X6
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

 

[pmarc]

I was thinking about holes being perpendicular in different plane (see fig. 7-42 in Y14.5-2009).

 

[fsincox]

The relative orientation of the axis is important in that determination. I can't see the picture of what you actually have.