Locating Pattern of Holes and Gage Design - Injection Molded Part

[dacili]

Hi All,

I'm new to GD&T (ASME Y14.5-2009) and decided to try to apply it to a injection molded part I am designing. It seemed pretty straight forward at first, but when I start thinking about drafts in the eventual part I become a little uncertain.

I've attached a sketch of a simplified version of the part, basically the part goes onto a metal shaft through the hole (Feature A) and then a separate threaded metal clamp block which buds up against surface B and C is used to clamp the part into place. Now just as a sanity check, if the part were to be machined:

1. Are my callouts adequate to locate the pattern of 4 holes? Ignoring the draft and parting line callouts of course and that I left out perpendicular controls between the datum features?
2. The functional gage for this would be a 31.95mm cylindrical datum simulator A and a planar datum simulator B and then a planar datum simulator C which is movable with 4 X 5.03mm gage pins?

If i'm right so far, then how does this differ when the part has drafts on it:

i. Is datum A now conical feature (must it be?)
ii. Do I now control datum C as a planar feature that is now at an angle to datum B?

I can only hope I'm not way of the mark here, I know from reading around here that there's ASME Y14.8 which has some details the rules for injection moldings however unfortunately do not have access to it. Though I've manage to get my hands on ASME Y14.43 to help me out with the gage design. Any feedback is appreciated, thanks in advance.

- Gilbert

 

[Tunalover]

You might want to follow the practices condoned in ASME Y14.8 for cast, forged, and molded parts. It talks a lot about establishing datums when there are no perpendicular/suitable surfaces to use for that purpose.

Tunalover