Starting Datums

[Troy442]

Seems like everytime we have a review of drawings there are many opinions of what the 3 "primary" datums should be. I am looking for some ideas from this group. I have attached a pdf of a single injection molded part. It will be inspected with a CMM touch probe. I have simplified the part for this discussion. There would be draft and ribs and small rounds etc. for molding.

This part holds a PC board with display and connector. There is another molded part that completes the enclosure and mounts to a wall.

So what are the thougts for A-B-C? Would you have a D or E?

Thanks, Troy GDTP-T-0386

 

[restedup]

Paul,

I have not been able to find referece online to Rectangular Ellipse, other than your explanation. Can you 9or someone else) direct me to a technical definition of one please.

Thanks

 

[ctopher]

No such thing as a 'rectangular' ellipse. An ellipse is an ellipse, a elongated circle. A circle has a square bounding box, an ellipse a rectangular bounding box.
Calling it a 'rectangular' ellipse is almost redundant.

Some links to explain datums...

http://www.tec-ease.com/tips/june-07.htm

http://nvl.nist.gov/pub/nistpubs/jres/104/4/html/j44mac.htm

Chris
SolidWorks 10 SP4.0
ctopher's home
SolidWorks Legion

 

[restedup]

ctopher,

Thanks, I almost fell for that one.