Solidworks Plastics Design Tools: Shell

I’ve written about the shell in the past

https://dezignstuff.com/capabilities-of-the-solidworks-shell-command/
https://dezignstuff.com/impossible-models-manufacturing-concerns-shelling/
https://episodes.dezignstuff.com/blog/tools-shelling/

I’ve got a couple of cool techniques for you here, and then some ways to get a shelled body when the shell feature won’t work.

Double Shell

Here’s a cool one first. This kind of thing happens with plastic parts frequently. It might turn out that you need to shell something twice. That’s what’s happened with this ice tray. It was shelled on the top to get the little indentations for the ice cubes, and then shelled again on the bottom to get the lip that goes around the tray.

Multibody Shell

This part had to be split in half and molded as two parts which were later assembled. But to shell it, the part has a transition section in the middle which would not shell. So I shelled it in three sections. The round handle area shelled great. The middle section I had to shell by hand with offset surfaces. And the main blade of the cricket bat also shelled nicely.

This was a case where I chose which battles to fight. I should have been able to force the middle section to shell by getting the tangencies between patches dialed in, but in this case, I chose not to fight that one, and just shelled the middle section with offset sketches and a new loft cut. Then I joined the three shelled bodies back together.

Outside Shell

I’ve only had to do this a couple of times. Outside shell. It essentially makes a thin walled part, but the inside of the shell looks like the outside of the part.

This was supposed to look like water splashing out of a bucket, but frozen in time. It was molded in transparent polycarbonate and in the finished product, it sat on top of a small bucket containing vodka, I think.

Entirely Hollow Part

This part was shelled with no face to remove. So it’s like a hollow Easter Bunny. This kind of part can be rotomolded or sometimes blow molded. It’s not really a trick, it’s just a technique that the Shell feature actually allows for if you don’t select anything in the Faces To Remove box.

Indent

And then of course is the Indent feature. You can use this in place of a Shell if you need to. It’s a little odd, but here’s how you’d go about doing that.

Let’s work with the ice tray we had before. And then just put a flat, thin extrusion over the top of the ice tray. Do it as a separate body. And then use Indent to indent the ice tray into the flat sheet. The tool is the tray and the sheet is the target.

It’s kind of insane, but it works. You can even set the thickness separate from the thickness of the sheet.

This kind of works like the thermoform method.

Multithickness Shell

The one thing you have to know about the multithickness shell to get it to work is that areas of different thickness cannot be tangent to one another.

For example, on a bottle there are two areas you might want to have a different thickness: The top screw area and the bottom. Just make sure these are not tangent to one another. And more than that, they need to have enough of an angle between them that the difference in thickness can be accommodated. So if there’s only a 3 degree non-tangency and the thickness on one side is double or triple the other side, it might not work. It’s just a geometrical situation.

Oh, and yes, this is an old screen shot with the old FeatureManager colors. (Did you know there’s a setting to get the old FeatureManager colors back? Tools/Options/Colors and Icon Color should be at the top of the screen.)