nwrichard,
Some of the folks who post here are the best of the best when it comes to ASME Y14.5-2009 and have helped shape Y14.5 over the years. They disagree sometimes, but not with respect to this. Take some time and look deeper. They have set me straight on many occasions.
Peter Truitt...
Hmmmmm. Where are the words??? I suppose you realize that the CAD model used for both illustrations is the same except I circumscribed a sphere around the cube as a last step in the illustration on the right side. Someone might be confused by the fact that I rotated the model after adding the...
I am still thinking about cubical vs. spherical tolerance zones. Noone responded the first time I posted it at http://www.eng-tips.com/viewthread.cfm?qid=325577. (I don't blame you guys/gals. I get in over my head all too often.) One of the attached illustrations shows a cube, with a basic...
I often design custom checking fixtures instead of the finished part. So my CAD model is for reference only. The checking fixture(s) might check form, function, or both. Here is one of the previous discussions:
http://www.eng-tips.com/viewthread.cfm?qid=313733
Peter Truitt
Minnesota
I am still thinking about cubical vs. spherical tolerance zones. One of the attached illustrations shows a cube, with a basic surface and its boundaries, similar to Paul’s. The other illustration (same PDF) shows the same basic surface and boundaries, but clipped by a circumscribed sphere. My...
Thanks, Checkerhater,
I guess I am not sure how to check either Paul Jackson's refined approach or the variation I asked about other than employing analysis software that would analyze a point cloud. I keep thinking about the benefits of round vs. square tolerance zones, but I know that we are...
Good comments!
When you hear "manufacturability" study "process capability". When people say that the design is process-capable and the parts passed inspection, ask them what measurement uncertainty value was used.
Peter Truitt
Minnesota
Perhaps it would be worthwhile to calculate the measurement uncertainty for each method that seems viable and give that inbformation to whoever needs to weigh cost of quality against risk.
Peter Truitt
Minnesota
Dean's response to Pmarc got my attention:
"Yes, I think two single segment feature control frames with position or profile could replace composite feature control frames. They're almost equal, except for how simultaneous requirements works (with "SIM REQT" being required to tie together...
I like employing colors to help the design process, but slow down when using them on finished documents. If color is significant, it would be wise (if not imperative) to note that the colors have significance and reproductions must include an adherence to the colors used on the document. This...
I agree with Kenat's suggestion to use a dash ( - ). I never had a problem with the FDA or FAA when my designs had that much scrutiny. In your internal drafting policies, you could define the dash and just ensure that you use it consistently, in my opinion.
Peter Truitt
Minnesota
The tolerance analysis software package that I am most familiar with refuses to analyze point cloud data using A-B datum references. Perhaps they are waiting for folks to agree or another Y14.5 iteration to clear things up.
Peter Truitt
Minnesota
There are two main approaches that I am aware of. One is championed by Frank Watts and the other by David Garwood. I think it is important to give each of these serious consideration before 'investing'. I always suggest reading their books, in depth, before making a decision that can have...
Formalizing a system that sets goals, identifies problems and addresses them with measurable corrective action is a deep subject that can be helped by reading thick books or by hiring staff that have had previous experience properly identifying and correcting design development problems. Having...
Production does not need to be very massive before process capability of small features becomes unrealistic, especially when considering measurement uncertainty and bias. I must wonder what the process capability has been or will be achieved in the OP.
Try this: Ask ten people to do a simple...
I would suggest having two drawings: A casting drawing and a machining drawing. The circularity of a sphere puzzles me. Only one datum is presented in the second option, but a second datum is referenced. I think folks are wondering how to get started with comments. I also know there will be...
