Dimension GD&T of a complex nylon / plastic parts.

[ingallspw]

I have a highly complex design that twist, curves, etc.

Let's say its similar to this PC fan

http://www.newegg.com/Product/Product.aspx?Item=N82E16835233112

but on a much larger scale.

Obviously you would want the blade to twist because that would effect airflow.
You would also not want it to lose the radius of the blade or go flat.
You'd want it to fit in the shroud without hitting the motor.

The problem is plastic flexes, relaxes, twists, etc.

We want the shape to be as close as possible to the CAD file.

Any one out there have any suggestions on how to dimension it?

 

[ctopher]

Dimension it to the final dimensions/tolerances.
The mold designer will design for shrinkage.

Chris, CSWA
SolidWorks 14
ctopher's home
SolidWorks Legion

 

[Tarator]

You're the one that knows the fit&function of this part... and you know what the functional and critical features are (tolerances). If the part is big, it might be considered as non-rigid.

 

[ajack1]

Unless I am missing the point put a surface tolerance on the "freeform" part.

 

[KENAT]

As ajack implies, this may be a good example to consider for Model Based Definition - or at least hybrid MBD where there is a partial drawing and then reference is made to the model.

A surface profile to the 'blade' portion may well be appropriate.

As to allowing enough clearance you need to work this out, and take into account process capability as to what tolerance you can meaningfully apply and then make sure this still meets function.

Function first, but it still needs to be manufacturable at acceptable cost.

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[ingallspw]

I think this youtube video is dead on to what I am looking for, talking about. (Obviously modified to match our functional needs).

http://www.youtube.com/watch?v=YpS5Sxcl4i0

 

[ingallspw]

I think we'd need to ad a C datum though because it would not be a constant section view... and then stack that on top of what this shows. Basically we'd almost like to make a cavity for it to fit in...