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Plastic Part Drawings

Question asked by Glenn Wilkins on Mar 31, 2009
Latest reply on Sep 9, 2009 by Tony Cantrell
I've started a new job with a company whose products are injection molded. Coming from a world of steel and weldments, this is kind of new to me. I've never seen drawings done the way they do it here and I would welcome your opinions on the following:

Their standard tolerance block on thier formats reads:

UNLESS OTHERWISE SPECIFIED:
1. DIMENSIONS ARE IN MM
2. TOLERANCES
0.00 TO 3.00 ±0.08 3.00 TO 6.00 ±0.10
6.00 TO 18.00 ±0.13 18.00 TO 30.00 ±0.15
30.00 TO 50.00 ±0.18 50.00 TO 80.00 ±0.23
80.00 TO 117.50 ±0.28 117.50 TO 180.00 ±0.33
180.00 TO 250.00 ±0.36 250.00 TO 315.00 ±0.38
315.00 TO 400.00 ±0.46 400.00 TO 500.00 ±0.51
ANGULAR TOLERANCE= ±0.25°

I've never seen this before. Is this form of tolerancing common in the plastics world?

I'm used to more like the following:

Unless otherwise specified:
.x = +/- .75mm
.xx = +/- .25mm
.xxx = +/-.125mm
.xxxx = +/-.0125mm


Secondly, on their drawings they show very few dimensions but have a note that reads:

"SEE 3D CAD FILE FOR COMPLETE SHAPE DETAILS."

I understand that fully dimensioning these complex shapes is impossible but is this how the rest of you do your drawings? Since there are only general size dimensions on the drawing, the tool maker has no specified tolerance to go by for the dimensions taken from the 3D model. Shouldn't we specify a general tolerance or GD&T profile tolerance at a minimum?

Would any of you be willing to share some good examples of your drawings with me?

This is a relatively new company and I'd like to get us on the right track as far as drawings go before we create too many more.

Thanks!

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