Are there any resources (online ,print, wherever) for draft angles, dependant on material and the distance the tool is being pulled over?
Something like this for instance:
Min. Draft. 1 degree over 25mm, 2 degrees over 50mm
Ideal draft. 2 degree over 25mm…
Or are the variations in material spec, tooling capabilities etc etc just mean this is impossible to compile?
I thought I knew of one but I can’t find it at this time. I also could be mistaken and no data base like this exists because of the complexity. You need to take into account the depth of draw, material rigidity, surface lubricity, mold texture, and material shrinkage. Then there is the part geometry itself adds another layer of complexity and if you are using ejecter pins or a stripper to remove the part.
But, as a rule of thumb, anything under 125 mm (5 in) of depth, 1 degree of draft is fine. And any molder will tell you, more is better.
Each manufacturer of plastic material, BASF, DuPont, GE, etc, usually has a design guide for the plastic in question. This design guide gives details on draft angles. Similar plastics from other manufactures are going to have the same basic characteristics.
I work with die cast brass, aluminium, gun metal, manganese bronze as well as injection moulded plastic and find that 2 degrees is absolute minimum for cast parts and 1.5 degrees for plastic while 3 degrees is better for castings.
I would talk to whoever is manufacturing your part. Toolmakers will tell you that for a certain radius there is a maximum depth and draft angle due to cutter availability and running tools within their limitations so they won’t snap.
Yeah, this is where a tooling engineer and manufacturer are your best friends, but that doesn’t mean they can’t be pushed. Just pretend you’re Apple.
Surface texture also will play a big role in draft requirements.