Detailing With Draft

[chancey]

Is anyone aware of a standard or other information that discusses the use of applying draft with the dimension? Example - .500 +3 DEG DRFT. I understand what I read but question the method versus dimensioning the draft separately. If this is common practice and legal in the drafting world than I am all for it.

Thanks in advance

 

[Heckler]

According to ASME Y14.8M Castings and Forgings. Section 3.5 Draft Angle - Draft angle and tolerance shall be specified. Draft angle shall be accounted for in determining datum targets and datum positions. Draft may be shown for drawing clarity. Draft shall be additive to dimensional limits and may exceed perfect form boundary at MMC unless otherwise specified.

Best Regards,

Heckler
Sr. Mechanical Engineer
SW2005 SP 5.0 & Pro/E 2001
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Never argue with an idiot. They'll bring you down to their level and beat you with experience every time.

 

[Heckler]

How I apply this to our injection molded plastic parts is I put a note that states draft to be 1 deg then dimensions that have a "+" draft adds to dimension and dimensions that have a "-" draft subtracts from dimension. I hope this helps.

Best Regards,

Heckler
Sr. Mechanical Engineer
SW2005 SP 5.0 & Pro/E 2001
Dell Precision 370
P4 3.6 GHz, 1GB RAM
XP Pro SP2.0
NVIDIA Quadro FX 1400
o
_`\(,_
(_)/ (_)

Never argue with an idiot. They'll bring you down to their level and beat you with experience every time.

 

[MikeHalloran]

I find the '+' and '-' causes confusion, and heated arguments over interpretation.

Better, okay, less awful, to draw in the draft, and dimension all edges.

Exaggerating the draft for clarity also causes confusion, etc.






Mike Halloran
Pembroke Pines, FL, USA

 

[alexit]

We use the + and - but to resolve confusion the ANGLE is not included just "- DFT" or "+ DFT" then in the notes we specify "3° Draft Angle Standard" never had anyone blink (even when outsourcing...)

 

[MikeHalloran]

Better still is to discuss the design in some detail with your preferred molder, who may not put the parting line where you expect it.



Mike Halloran
Pembroke Pines, FL, USA

 

[pdybeck]

On our casting drawings, we explicitly state the tolerance of the dimension, draft included. This forces us to work to fully investigate and document the tolerances assoicated with all the dimensions on the print, taking into consideration draft, general tolerances due to sizes, and considerations of parting line and core location shifts. This also makes it much easier for our inpsection department and our casting vendor to agree on the tolerance, b/c we have defined what the tolerance is according to accepted industry practices. It is more up front work, but we feel it pays for istelf in the long run due to the experiences we have had in the past. Now there is no mistaking what the tolerances are. If a vendor has a problem with the tolerance, then we discuss it up front before the contract is signed. We also must specifiy parting line locations up front, as this dicates what tolerances apply to certain dimensions. If the venodr doesn't like the parting line location, then we can change it and evaluate what other tolerances should be applied to a new set of dimensions.