Designing sheet metal parts is the art of balancing functionality, manufacturability, and safety. For product design engineers, mastering basic rules of sheet metal design is key to turning part design into high-quality, durable components. This article highlights essential tips for optimizing sheet metal designs to ensure both manufacturability and cost-effectiveness. Whether you aim to reduce the cost of sheet metal parts or improve their product quality, these insights will guide you in avoiding common pitfalls and applying best practices to create superior products that excel in today’s competitive market.

There are two primary reasons to avoid sharp corners on sheet metal parts. First, for safety: sharp edges can easily cause injuries to workers during manufacturing and assembly, as well as to users during product use or maintenance. Second, for tooling: sharp corners on sheet metal parts also mean sharp corners on the die, which are difficult to produce and prone to cracking during heat treatment. Additionally, the punch’s sharp edges can chip and wear out quickly during blanking, reducing the mold’s lifespan, and increasing production costs.

To mitigate these issues, sheet metal designs should feature rounded transitions at sharp corners, as shown in Figure 1. Typically, the radius of the rounded corner should be at least 0.5 times the sheet metal thickness, and no less than 0.8 mm. In this context, R represents the radius, and T represents the sheet metal thickness. Similarly, internal sharp corners should also have rounded transitions, adhering to the same guidelines.

In sheet metal design, it is crucial to avoid long cantilevers and narrow slots. Those features can lead to small punch sizes on the stamping dies, which reduces strength and shortens die life, ultimately increasing the costs of the sheet metal part. Generally, the width of long cantilevers and slots should not be less than 1.5 times the thickness of the part, i.e., A≥1.5T, where A represents the width of the cantilever or slot, as illustrated in Figure 2.

Hexagonal holes provide a higher open area ratio, offering better heat dissipation, but the complexity of manufacturing hexagonal holes makes the tooling more costly, increasing production cost. Square holes offer the highest open area ratio, but their right-angle corners lead to faster tool wear, increasing costs similarly. Therefore, when designing ventilation holes, it is essential to balance ease of manufacturing with the system’s heat dissipation requirements. Where possible, round holes should be prioritized to satisfy system cooling needs while ensuring easier production.

When punch holes are not parallel to each other or the edge, the spacing between holes or the distance from the hole to the edge should be at least equal to the sheet metal thickness, i.e., B ≥ T, as shown in Figure 2. If the holes are parallel, the spacing should be at least 1.5 times the thickness, i.e., C ≥ 1.5T. In general, the size of the punch holes in sheet metal should be at least 1.5 times the thickness of the metal. If the holes are too small, the punch die size will be too small, making it prone to breaking or bending, leading to the increased production cost. The minimum hole size also depends on the material of the sheet metal. For softer materials, the minimum hole size can be less than the sheet metal thickness, but for harder materials like stainless steel, the minimum hole size should not be less than 1.5 times the sheet thickness, i.e., D ≥ 1.5T, as shown in Figure 2.

The distance between punched holes and the bending edge or forming features of a sheet metal part should be at least 1.5 times the thickness of the sheet metal plus the bend or forming radius, i.e., E≥1.5T+R, as shown in Figure 4. Otherwise, the holes are highly likely to distort during the bending or forming process, causing the sheet metal parts quality issues and impacting the products.

1) If the distance between the punched hole and the bend or forming feature is too close, consider bending or forming first and then punching the hole. However, this increases the complexity and cost of the mold, so it is not the recommended way.
2) Add a relief cut to the bend or forming area to absorb deformation during bending or forming. This ensures the quality of the punched hole, as shown in the upper part of Figure 5.
3) Increase the size of the punched hole, as shown in the lower part of Figure 5.

When designing sheet metal components, product design engineers often work with 3D models, which can lead to overlooking the verification of clearance when the sheet metal is unfolded. This oversight can result in insufficient clearance or even material interference once the sheet is unfolded, especially in more complex structures.

For example, as illustrated in the upper part of Figure 5, if the dimensions of a relief cut are not correctly designed, the clearance may be too small once the sheet is unfolded. This can reduce the strength of the punch in the stamping die and significantly shorten the tool’s lifespan, increasing production costs, as shown in Figure 6.

If you have any questions or need further advice on sheet metal design or manufacturing processes, please don’t hesitate to Contact us. We’re here to help you create exceptional products that meet your needs and exceed expectations.