Join Gabriel Corbett for an in-depth discussion in this video Understanding sheet metal, part of SOLIDWORKS: Sheet Metal Design.
So, what makes sheet metal different from other parts designed in SolidWorks? Okay, so let's go over the basics. Number one, constant thickness. All sheet metal starts out as flat material and needs to be cut to size via laser, punch press, stamping press or shearer. Because material either comes in standard thicknesses, we need to choose one of those available gauges. Next, we need to bend the material with specialized tooling using standard raduis'. It's best to design with standard tooling to avoid needing you buy custom tools that are both cost and lead time to your design.
Let's go over some basic terms Sheet metal. Number one is thickness. Thickness is the material, gauge thickness you are going to select, when you first start off making a Sheet metal part. The bend radius is determined from these tooling you're going to be using to bend your part. Standard bends radiuses are 030, 060, 090. Eighth inch, quarter inch, 3 8ths, half inch. And those are just a few of the available radiuses that your sheet metal supplier will probably have. The k factor is determined by selecting the material, the bend radius and the type of tooling you have.
A lot of times your sheet metal supplier will be able to provide you the correct K-factor, bend deduction or bend allowance depending on how you want to use these values. The bend allowance, again, is the amount of material or the arc length of the bend. And we can look those up in tables and we're going to look at a few in just a few minutes. The bending was always determined from the flap to how much you are going to bend that flange up. So, in this case here, it's from the flat, in this case, we have a 90 degree bend. The flange length is again from the flat to the end of the flange. The final thing must be a mold line measurement that term not really use quite as much but that's the length up to the edge of the bend. I've included a few different tables for you to look up the gauge thicknesses of the various materials.
I've included both the aluminum table, the steel table, as well as the stainless steel table. And these are standardized thicknesses of gauge. This is just a subset of the different values. They're quite more extensive, if you open the PDF documents that we've included in the Exercise files. If you look at a couple different gauges, let's go down here on the aluminium table and look at 12 gauge. You can see it's 080 thickness. If you look on the steel table, the same 12 gauge materials is actually 0.104. So, the same gauge thickness is actually different from material to material. So, make sure you plan on that and you can't easily switch between two material gauges and expect the material to be exactly the same size. Here's an example of some break tooling.
You can see we have an upper die, which pushes into the material, at the bottom of the upper die you have a bend radius, which is going to determine the bend radius of your sheet metal piece. Your material, which then spans across the two sections of the lower die, and generally, we want to make sure that our thickness of material. And our lower die or our flange length is four times the thickness in the material. Otherwise, it won't hit these corners of the lower die and you'll have an issue that it doesn't form correctly. So, make sure that the flange length of your material is a minimum of four times your material thickness. Now, you can make it smaller if you need to.
However, it might be a matter of making custom tooling or having to remove part of the flange after your building the part and that's going to add cost and lead time. The back edge can move in and out to determine the length of your flange. Over here on the right you can see the completed bend and the material comes up out of the back gauge and forms into the V shape. This is an example of goose neck tooling. Sometimes when you want to make a relief flange, where the material actually comes up over and around, you need to have some clearance. If you use standardized straight tooling here, this flange would hit the backside of the tool. So, in this case here, you've got this goose neck die that comes in here and allows the material to form around there and provides a little bit of a relief. Keep in mind, when you're working with gooseneck dies we have to make sure we maintain a certain distance between the first flange and the return flange to allow the dye to get in here to actually form this bend. Here's an example of three different bend radiuses on the exact same piece of material.
If you look over here, the flange length is 1 and a half inches and we have 1 and a half inches of material here. So, if you flatten this out without a bend radius, it'd be 3 inches total. But as you can see by adding a quarter inch radius bend the flat length is actually 2.44. As you go up in bend radius thickness, so in this case we have a 3 8ths bend and this flat pattern is actually 2.38. And when you go to a half inch it comes down to 2.33. So, as the bend radius goes up, the flat pattern gets shorter and shorter. This is an example of a bend deduction table for an 030 radius tooling at 90 degrees, and you could see each value, say, 16-gauge for the thickness of the material has a different set back.
Steel and stainless steel have the same thickness. However, a little bit different set back. Where if you go here to aluminum, we're looking at a much different set back value because the material bends and forms differently. Make sure when you're designing a SolidWorks, that you choose the correct thickness and set back values so that your flat pattern will be the correct size when they come to build your parts. This is an example of different K-Factor values. As you can see, as the bend radius gets close to three times the material thickness, all those values end up going close to 0.5. These values are just reference values. However, you might want to check with their materials applied if you want to choose the K-Factor method for determining the flange length. Finally, I have included a setback.XL file that allows you to type in a material thickness, type in the bend radius and type in the angle as it's going to calculate for you the setback.
These values are going to be approximate, however, they're going to do a pretty nice job of getting you close to the values you need. This works great for thicker material or odd-sized bend angles. When working with solid Sheet metal, keep in mind that the computer can design anything. However, we need to stick with standard tooling and materials whenever possible. Hopefully these tables will be a good reference for you in the future.
- Understanding sheet metal fundamentals
- Creating base features
- Creating flanges and tabs
- Making hems and corner features
- Unfolding and folding parts
- Adding cuts across bends
- Adding welded corners
- Using the Forming tools
- Importing geometry
- Using the Convert to Sheet Metal command
- Making sheet metal drawings
- Exporting DWG and DXF files for laser cutting
- Building an assembly
- Creating parts in an assembly
- Creating flat patterns
- Using in-context design techniques
- Exporting parts