5 Ways to Design Sheet Metal Parts for Better Fabrication
Are the sheet metal parts you’re designing actually able to be made on the shop floor?
When engineers submit a drawing or model to a precision sheet metal fabrication shop, there’s often a disconnect between the design itself and the manufacturability of the part. At Ameritex, we’re always upfront about any changes we need to make to the initial design—and this communication is key to developing lasting partnerships with our customers.
During these conversations, we’ve come to realize that many of the engineers we work with are eager to learn more about designing for manufacturability (DFM) and sheet metal fabrication. They want to know that they can send their model to a shop and feel confident that it’ll be made according to their exact specifications.
That’s why we’ve made it our ongoing mission to help set engineers up for success right from the start. The good news is that there are some easily avoidable mistakes that can easily improve your sheet metal part designs.
When you avoid these common mistakes, you’ll know that what you’re designing ultimately translates to the shop floor.
Top 5 Problems with Sheet Metal Part Designs
Problem 1: Flanges are too short for the particular material thickness.
In most cases, we use a press brake with a v-shaped die to bend sheet metal parts. During the bending process, it’s important to have enough material to reach all the way across the die, otherwise, there’s nothing to catch it and create the bend.
The v-size is typically set to 5-8 times the thickness of the material, and the die ultimately determines how short the flanges can be. As a general rule of thumb, we recommend multiplying your material thickness by 8 and designing your flanges to be only about half of that measurement so that the material will reach the other side.
Problem 2: Features are too close to bends.
Similar to the problem with flanges being too short, the v-die determines everything when it comes to designing features into a part. If the features are too close to the area undergoing the bending forces, they’ll become stretched or deformed once the material is bent.
Round or square holes designed too close to a bend will be stretched into ovals or rectangles, respectively. Extrusions (like louvers for electrical enclosures designed too close to a bend will be crushed by the tool. Pressed-in hardware can also become damaged during the bending process.
To prevent this issue from occurring, any features you include should be designed outside the die by a considerable amount.
A good rule of thumb is 1.5 times the thickness of the material plus the inside radius of the bend. This usually equates to 3 or 4 times the thickness of the material when using 5 to 8 times material thickness for die size but will increase as bend radius and die sizes increase.
Problem 3: The parts are too deep to be bent on standard tooling.
When designing parts that are bent in multiple places, like a box or an enclosure, engineers frequently provide drawings with all sides bent. By the time we get to the third flange, the sides are too long for a standard press brake to handle. If our precision sheet metal fabrication shop receives this type of drawing or model, we have no choice but to break it apart so that we can fabricate it.
We encourage engineers to design each side no more than 8” tall (6” for most efficient bending) and, if the goal is to have us build to the exact design, go ahead and separate the smallest sides to begin with. If we’re going to have to weld a side on, we always want it to be the smallest side requiring the least amount of labor to save our customers on cost and lead time.
Problem 4: Features collide when flat.
Many of the drawings and models we receive include features that collide when their part is unfolded (i.e., translated to a flat sheet of metal). We typically encounter this issue with parts that have complex contours or when an engineer is trying to close a gap on a part where aesthetics matter, like for an architectural application.
Fortunately, there are easy ways around this problem. SOLIDWORKS will warn you when it’s happening, so be sure to pay attention to those alerts and adjust your design accordingly. If you need a solution and want to guarantee that we can make it happen on the shop floor, we recommend welding or bolting on another piece of material.
Problem 5: Awkward flat patterns and wasted material.
When it comes to low-volume sheet metal fabrication, custom metal shops usually work with standard size 4’-5’ wide sheets. If you’re designing a part with an awkward size or shape that does not fit well on standard sheets, or a part with large cutout features—you may end up paying extra money for wasted material.
Our typical solution for this problem is to split the design into two pieces and weld those pieces together after cutting to make better use of the available material. So if you want your part made exactly as you design it, we recommend evaluating the flat pattern and, if necessary, designing the piece to be split apart and welded or fastened back together.
Hopefully, this advice will help you feel more confident designing sheet metal parts for manufacturability. Next time you need sheet metal fabrication services, give us a shot! We’ll always jump through hoops to get you the parts you need.