Drawn sheet metal pressing / extrusion

guy_thomas086

Hi
I have been tasked with drawing a steel pressing from sheet metal The pressing is a square plate with a 'drawn/extruded' cylindrical spigot/neck.

I have tried several things but extruding a feature in sheet metal mode does not appear possible. Have also tried adding a hole to the plate and then in sheet metal mode using the flange option, but this will not permit selection of the edge of the hole...
Does anyone have any suggestions that would enable me to model this part please? 
Thank you in advance for any help you can offer.

eric_pesty

"Active" sheet metal doesn't support formed feature like this. There is also no real "general" way to compute the shape of the required flat as the metal must be stretched and the amount of stretching depends on the tooling geometry etc...
Currently the only way to model this is to "finish" the sheet metal model and model this with a "standard" features and then let the manufacturer "figure out" what the flat shape needs to be to achieve the desired 3D shape.

matthew_stacy

@guy_thomas086, the fundamental issue is that "sheet metal" has entirely different meanings in the realm of "CAD" than it does out on the shop floor.  A key term is "developable surface".  CAD software typically defines "sheet metal" as linear bends (curved in a single direction).  The flat-pattern can be mathematically developed from the formed shape.  Think of "folding" a sheet of paper, rather than forming a salad bowl.  In this realm the math for transforming formed part to flat pattern (or vice versa) is fairly simple (thickness, bend radius, and k-factor) and deterministic.  CAD software excels at generating flat patterns in this special case.

We commonly form more complex surfaces with compound curvature (salad bowl, stainless steel sink, deep drawn beverage container, automotive body panel, etc).  As @eric_pesty pointed out above, the underlying math for this is much more complex, and most importantly, non-deterministic. In this general case the relationship between flat-pattern and formed-part very much depends on the specific design of fixtures for holding the work-piece and the specific design of the forming tools.  It's difficult to even quantify all of the relevant parameters let alone crunch the numbers.  Fortunately skilled artisans an designers have been applying their experience and intuition to these endeavors at least since the bronze age.  But it is a very empirical process.  Any software that claims to "flatten" complex curved surfaces should probably be taken with a grain of salt, unless it requires a lot of detailed input about material properties and tooling geometry.