A hem is basically just bending over the edge of sheet metal to get a smooth, finished edge, versus a rough or sharp edge.
Hems also help to improve the strength of the sheet metal edge.
There are several types of hems that SolidWorks can create and if done correctly, features like piano hinges can be built into your part.
This does take some special tooling, so make sure the shop you're working with has the tooling. To get started, let's select an edge to hem.
I'm going to pick this edge here. And go up to the Sheet Metal tab and make sure I pick the Hem tool. And you can see right off the bat, I get a preview of what's going to happen. I want to use this closed hem here to start off with. So let's go over the features.
Number one is the edge that we chose. I can choose an adjacent edge to add additional hems to the sides. I can choose how I want that hem to be placed.
Do I want the material on the inside or do you want to add additional material to push it on the outside. I'm going to choose the first option there.
As far as the closed hem, I can have it so it's actually smashed against the other at the joining face. I can have it as an open hem by pushing it up.
I can have it as a teardrop hem or I can have it as a rolled hem.
A bunch of different options I can play with there.
In the first case, I'm just going to choose the basic closed hem and I'm going to adjust the length to being 0.375. If I have miders in my part, I can adjust the gap between the two. In this case here, I'm going to type in 0.03.
When you're happy with how it looks, go ahead and click OK.
And all those edges get hemmed out. If you want to edit the hem, we could always go back to that same feature over here, click on the feature.
Click on the fly out Edit Feature tab, and I can come back to it.
I can go back and adjust the hem, I can adjust the gap, maybe I'll make an open hem over here. And I don't really want all those edges, so I can go back and hit the Delete key to remove some of these other faces So I'm only doing that to the one edge. But you can always go back and edit things as needed. Now on this side of the part, maybe I'd like to add like a piano hinge for instance.
So what I'll do is I'll click on the edge, I'll click on Hem and in this case here I want a Rolled Hem. And I can type in the degree and I can type in the radius. So the radius would be whatever size pin you'd be using, we'd probably want half that pin diameter for the radius.
So let's say that we're going to use an 8th of an inch pin.
So maybe I'll give it a 0.065. So that'd be 0.03 which would be half the eighth inch plus a little bit more just so we have the clearance in there.
Let's zoom in and take a look what we have there.
So in this case here it'd be a little bit too open, so I'm going to change that angle.
So I can bring that all the way around and form it so it's just about hitting that lower face. So maybe 295 looks like a pretty good angle.
When I'm happy with that, go ahead and click on OK and there we have it.
Now to make a true piano hinge, we'd actually need to go back and slice this up and do some cuts to divide up that surface across the part.
But we can come back and do that later. Hems are a nice way to finish the edge of a sheet metal part, it can create a more professional and polished look on your design.
Not only do they strengthen the edges, they can also design in custom hinges or other connections into the edges of your parts.