Sheet metal design offers many challenges, so coming up with smart design strategies is vital. Sometimes, it’s difficult to reconcile the things we want in our parts with what’s truly needed. Sheet metal fabrication is a very hands-on process, so design becomes a balance of aesthetics and economics. Five of the smartest sheet metal design strategies engineers can incorporate are simple, and they can help reduce costs and lead times.
Use Stocked Sheet Metal
It’s always a good idea to use the types and thicknesses of sheet metal that your manufacturer stocks. Most manufacturers’ websites list their stock materials. Using special order material will cost more, especially if the quantity doesn’t meet the minimum amount required for purchase. That special order could also add to the lead time for your parts. If special materials are required, you should consider availability and cost at the design stage.
Uniform Bend Radii
Using a single-size radius on your part bends will not only give it a uniform look, it will save money. Each different bend radius requested for a part requires a separate press brake setup, adding significant cost and longer lead times.
Also, using industry standard bend radii helps keep costs down. When using material thicknesses under 0.125 in., you should always consider the standard bend radius of 0.030 in. It typically offers a manufacturer the most choices for stocked tooling to make the part.
Design to Center of Desired Tolerance
Here’s one that’s a little more complex, but incredibly important. Many designers will include a tolerance of +0.030/-0.000 in. on a critical dimension, then have the model at the 0.000 in. point. While the tolerance surely adds some flexibility for the manufacturer, it can cause some problems. Today’s manufacturers refer to the CAD model in their manufacturing process.
So, let’s say a cover is 12.000 in. +0.030/-0.000 in. wide on the outside and the designer has it modeled at 12.000 in. The machines will be programmed to the model. Because of material variances and machine tolerances, this cover could come in under the 12.000 in. dimension during manufacturing. Instead, you should model at 12.015 in., and if you include a print, show a tolerance of +0.015/-0.010 in. You will get a part that will stay consistently in the original tolerance of the 12.000 in. +0.030/-0.000 in. In the end, the CAD model will be more reflective of reality.
Uniform Corner Radii or Chamfers
Replacing pointed corners with radii or chamfers on sheet metal parts is a great idea. Unfortunately, these are sometimes overlooked or over-engineered. With certain parts, a designer must consider where the parts are located and if sharp corners could be a hazard for the consumer. Not only do chamfers and corner radii eliminate sharp edges, using the same dimension throughout your part adds visual consistency. It also helps a manufacturer when tooling the part for punching, if required.
Use Standard Hardware Inserts
Another strategy involves using PEM hardware to fasten other parts or electronics. When considering what PEM hardware to use, remember that most manufacturers stock a set of standard types. Sticking with these is another way to speed the manufacturing process. While you can consider other hardware types, special orders may require a minimum purchase. That could add significant lead times and affect timely delivery of your part.
Designing sheet metal parts is challenging. Maintaining standards is key. Using these five smart sheet metal design strategies will allow designed parts an easy and direct route to production. It will also keep the overall design intent of the parts.
Related Design Tips
For more helpful sheet metal design tips, download our Design for Manufacturing (DFM) Guide.