PMI and downstream usage

[randomdrafter]

Posting this in GD&T forum as well.....

Does any one used Link to PMI option in NX Inspection module? how many dimensions/GD&T linked automatically after running this command? Does the tool automatically links all the tolerances/dimensions mentioned in help files?

If we make sure PMI annotations link automatically through NX Inspection and create program will it compatible with other CMM software's?

Is PMI used in CAM programs automatically? in which other downstream applications PMI can be used?


Another question,not directly related to PMI, how complex parts with only model is given without most of dimensions get inspected [We have few critical dimension shown in drawing,for remaining model is master.]

 

[JNieman]

To your last point:

It relies upon your default-tolerances and manufacturing requirements. If you have a statement that says "Unless otherwise noted, hole positions must be within [true pos | .030 | A | B | C ] and surfaces within [ prof o' surf | .030 | A | B | C } with the 3D Model considered the Basic/Nominal condition" Then the CMM must inspect all surfaces based upon that alignment.

We get parts from customers at times that fall under this category. They send us a .STP file or other neutral format, typically. The PDF drawing may have 3 dimensions called out, the key characteristics or critical features, or whatever you want to call it... and a general note covering the rest.

I won't speak as to how "proper" this practice is, but they get good parts, they don't reject parts unfairly, and everyone gets paid. It seems, to me, that the part is fully defined and controlled. So long as the designer has considered how 'loose' the part may be made, and accounted for that, then no issue should arise. I'm sure some lawyer could tear it to shreds, but no reasonable person should be able to make a bad part check 'good' with this practice.

 

[randomdrafter]

No GD&T general note called in drawing. just mentioned refer CAD model for missing dimensions. There is also a internal spec number attached which deal with +/- tolerance and other stuffs. Funny thing is this spec specifically mentions models should not be used for inspection.[May be we are one of your customers ; )].

One of the reason i am asking this point is try to reduce dimensions and use model as much as possible when applying PMI. But this may translate headache to supplier than us designers.

Thanks for reply, Any information about remaining points?

 

[JNieman]

No, sorry, no experience with translating PMI directly to CMM software. We don't use NX for inspection / CMM programming, but we do for drafting, design, and CAM programming. I'm curious what others say. Our current process is to translate models to STP, open in Calypso/PC-DMIS, verify the translation accuracy, and program from there.

The idea of working from MBD, and having suppliers make your parts, is a pretty decent sized discussion. Yes, it shoves some headache off on the suppliers. However, I believe there's a happy middle ground that makes everyone equally head-ached, that yields good parts at a better lead time. However, many manufacturers do not want to depart from a "fully dimensioned paper drawing" for every part. I don't suggest that machinists/manufacturers operate "blindly" but I do think there's a point in between the extremes where real progress can be made.

 

[randomdrafter]

JNieman, I tried Link to PMI in NX Inspection module. It successfully linked few dimensions,unfortunately there are issues in NX 8.5, so need to check in NX 9 or NX 10.

Is your CAM programming manual or some sort of automation available by using PMI?

 

[JNieman]

No automated programming. I'm not much help on that topic.