A few pointers:
-Tighter tolerances = higher cost. Larger number of tolerances = more places they will have to measure and verify = higher cost.
-The thickness of the sheet is specified to +-0.02mm. This is very tight and close to impossible. The material will be thickened or flattened at the bend depending on how they draw or bend it. It is also very difficult to measure if that thickness is correct all the way so best case scenario is that they ignore it.
-The 0.04mm width of the spring is quite tight as well, does it need to be that exact?
-Geometric tolerances. There are signs which is used to specify flatness, circularity etc. I suggest you look through this link and use them rather than text.
Edit:
-Stacked tolerances:
http://i.imgur.com/qB0XNle.png
The dimension marked in red will be +-1.3mm if you add up the tolerances of the other dimensions. Be aware of where you put the dimensions and exactly which dimension is actually important. Just something to be aware of.
Thanks for the pointers and info damorgue!
The shim stock I used as a starting material claims a
thickness tolerance of 0.00075" which is almost exactly 0.02mm;
however you're correct that my thickness spec in the drawing is
ambiguous - I don't actually care about what happens to the
thickness in the bends, or really anywhere but along the flat bottom
where the magnet will contact. I'll have to see if I can find a way to
communicate that in the drawing.
Regarding the width: the holding force will be closely tied to volume
of material in the leg of the clip that the magnet contacts. +/- 2.5%
of the width is ~ 0.04mm. +/-5% of the thickness is 0.02mm.
Stacked together this is a 15% potential variation in holding force,
which I already think is a lot - I don't think I should open those specs.
Thoughts?
I agree that the dimension you noted ends up being wide open at
+/-1.3mm. That is intentional - There is some latitude in where the
top corner ends up relative to the right-side. It does not need to be
kept tight, but can't be left unspecified since it must fall within a window.
It serves as the retension mechanism so that the clip doesn't fall out...
just needs to dig into the plastic a tiny bit.
I will look up the symbols, take another swing at it, have an ME buddy
review/update, then post and send for quote. Any bets on the per-clip
cost at 1000 pieces?
Thanks again for the input!