draft angle

[par1]

I have recently started with plastic part design. (understand little bit core/cavity, draft, fillet requirement....)

As per my understanding the draft angle - considering ice tray- draft at the bottom side would be minimum(bottom of tray) & will increase as move towards top face of ice cube.

Does it true for any plastic part or may be it reverse sometimes?

The reason to ask you this question because i have two part dwgs & which draft varies on the cavity side (postive & negative draft)

 

[MikeHalloran]

There are a few conditions under which a reverse draft would be appropriate:

- Where you want the finished part to always cling to that part of the mold, e.g. so a robotic handler will always find the part.

- On a male mold feature, maybe combined with a positive draft to make a wasp-waisted part cavity, so the part will be a push fit on a straight- sided mating part.

- Where the part is a snap-fit to something, there may be a very obvious back-taper.

- Under bizarre circumstances, I suppose in a high- shrink resin, you might need a reverse draft in the mold to produce a zero draft surface in a part. I don't recall ever doing it myself or seeing it done, but it's possible.

There are probably many other reasons ...


Mike Halloran
Pembroke Pines, FL, USA

 

[TheTick]

I recently did a part with negative draft for a "Tupperware" type seal. Tried the tool last week; works great.

Reverse drafts can work. What is important is that there is some place for the plastic to deflect to when ejecting. This can be accomplished with adequate taper (if on a rib cut into a single half of the tool) or if opposite side of undercut is on the opposite side of the tool (i.e. undercut on core, opposite side relieved on cavity).

I could be the world's greatest underachiever, if I could just learn to apply myself.

http://www.EsoxRepublic.com

-SolidWorks API VB programming help