Combinations & Permutations for gd-t
Combinations & Permutations for gd-t
(OP)
Has anyone used statistics formula (using MatLab) to come up with a number of combinations you can have for a specific tolerance stackup? with tolerances, w/wo gd&t, w/wo M modifier, w/wo L modifiers, etc. Say the gap constraints are given, thus calculate the missing dimension. pretty straighforward.
thanks
thanks





RE: Combinations & Permutations for gd-t
Where do the statistics come from? When I apply tolerances to drawings, I am specifying what I want. I hope the fabricator can do it. My tolerance stack-ups are based on specified tolerances.
I don't have statistics unless I inspect a batch of pieces.
--
JHG
RE: Combinations & Permutations for gd-t
RE: Combinations & Permutations for gd-t
If you do tolerance stacks manually, you assume all the worst cases. If you specify a positional tolerance of Ø0.4mm, your inspector must accept parts when the holes are 0.2mm out of position. What is ±3σ? Maybe the fabricator's process is Ø0.1mm! Maybe it is Ø0.6mm, and their inspector is doing 100% inspection and rejecting a significant number of parts. You don't have statistical data until you inspect stuff. You cannot assume that the statistical distribution has any relationship to your tolerances.
In mass production, there are all sorts of work-arounds, but you need to know the capabilities of your fabricator.
--
JHG