Cons of zero tolerancing at MMC

Hello!


Today I was presented to the concept of zero tolerancing at MMC on postion tolerance. I quite understood how it works but couldn't understood why it's not so used in industry. For me, it ALWAYS has more benefit than using the MMC plus any tolerance since the virtual condition doesn't change as well the LMC and beside it the inspector could use a fixed gage with size at virtual condition and just be sure the part pass trought the gage and don't waste time checking if it's meeting the MMC. Do anyone knows an situation where zero tolerancing at MMC may not be the right choice?

[QUOTE=ivanginato;18032]Hello! Do anyone knows an situation where zero tolerancing at MMC may not be the right choice?[/QUOTE]

[I]When a know minimum clearance between mating parts at virtual condition is required and the designer chooses to not build in the clearance at zero mmc. [/I]

Though zero at MMC gives more combinations of fits and acceptable geometric tolerance and simplifies functional check gage requirements this isn't always a benefit. Functional check gages are becoming less utilized in mass production environments as automated technology is becoming more cost effective. Moreover there may not be a 100% check on production parts required when six sigma manufacturing capabilities are achieved.

The case for zero at mmc is sound however there is not a "one-size-fits-all" in the world of engineering and manufacturing.