What are the procedures and rules of sheet metal design? Why do manufacturers spend more on fixing errors? The sheet metal design needs to go through a thorough checking process to avoid any design errors. As revealed by research reports, manufacturers spend more than forty percent on fixing errors. More importantly, twenty-four percent of those errors are the outcome of manufacturability problems. During the manufacturability process, they need to focus on some essential factors. A few of them are temperature, fabrication, and bending. In the following sheet metal design guide, we will cover a lot of things. We will know how to design sheet metal and sheet metal material requirements. Also, we will focus on basic rules and common mistakes. With a proper understanding, manufacturers can make the process fast and cost-effective.
Table of Contents
- 1 Rules for Selecting Sheet Metal Materials
- 2 5 Basic Factors to Consider when Designing Sheet Metal
- 3 Common Mistakes to Avoid when Designing Sheet Metal Parts
- 3.1 Using Models without Any Bends
- 3.2 Adding Features Close to the Bending Lines
- 3.3 More Emphasis on the Perpendicular Metal Corners
- 3.4 Not Specifying Hardware Specs in the CAD File
- 3.5 Choosing the Wrong Finish
- 3.6 Choosing Wrong Metal Sheet
- 3.7 Not Considering U-Channel Strength
- 3.8 Focusing on Impractical Weld Needs
- 4 Conclusion
Rules for Selecting Sheet Metal Materials
The sheet material selection will play a determining role. Manufacturers will have to understand the unique material requirements to select the best material for the manufacturing. If they choose the best sheet metal material, they can reduce the cost of manufacturing. Also, the accurate material will contribute to the product manufacturing process, quality, and performance. When it comes to rules to select the correct material, you can consider the following.
- Focus on common metal materials. By doing so, you can reduce the specification of the material, and you can have better control based on the material manual of your company.
- While designing a product part, you can diminish the sheet thickness specification and the variety of the material.
- To minimize the cost and improve the functionality of the end product, you can use inexpensive materials. You can reduce material use as well. Ultimately, it will reduce the end cost significantly.
- For large plug boxes and cabinets, you will have to focus on the overall weight of the machine. Yes, the product weight needs to be less to get a better outcome.
- In addition to the functionality of parts, you will have to consider the stamping usability of the end material. It will have to meet the processing demands to ensure the quality and rationality of the product processing.
5 Basic Factors to Consider when Designing Sheet Metal
Sheet Hole Sizes
If the design has small holes, then it will need smaller punches. That might lead to breakage during the manufacturing process. Hence, the diameter of the holes needs to be greater or equal to the thickness of the metal sheet.
When it comes to bending relief, it is a must to make the bending process simple. It will support the design process. If the flange lacks this unique feature, it will experience a higher degree of distortion. As a result, it might impact the adjacent material. Hence, you will have to follow a thumb rule. The depth of the bend relief needs to be greater or equal to the inside bend radius. However, the width needs to be larger or equal to the thickness of the metal.
Bend & Hole Distance
It is a determining factor. There needs to be a required distance between a bend and a hole. Otherwise, the metal hole will deform while bending the sheet material during the manufacturing process. Hence, you will have to follow a rule to make the distance accurate. The distance between the edge of holes and bend lines needs to be 2x or even more of the sheet material thickness.
Bending Radius of the Sheet Metal
The bend radius of the sheet material will depend on the tool and process of the manufacturing. With better flexibility, manufacturers can get a smaller bend radius. Hence, you can follow a simple rule to avoid any mistakes. You will have to ensure that the minimum bend radius for any mild steel metal is almost equal to the metal thickness.
Minimum Flange Size
During the sheet metal assembly design, you will have to ensure that the flange width is more than 4x the thickness of the sheet metal. If you do not follow this rule, tools might leave marks on the surface of the sheet. It might impact the appearance of the end product.
You will have to follow these five rules to avoid mistakes and spend less on product errors after manufacturing. A few considerations will save you a lot in the end. Apart from material requirements, you will have to avoid some other mistakes during the designing process. Here are more details.
Common Mistakes to Avoid when Designing Sheet Metal Parts
Engineers experience many problems while designing sheet metal parts. They notice a few common errors during the designing process. Here are some mistakes that engineers can avoid during the manufacturing process.
Using Models without Any Bends
It is the most prevalent issue that engineers experience during the designing process. As we know, sheet metal is available in flat form. Therefore, it needs to be bent, cut, formed and lased to get into the final shape. While designing a part of the sheet metal as a solid object, you can use a CAD file that looks folded. It will show where you need bends. Also, as you will use a single sheet of metal, the entire metal part needs to have the same level of thickness.
Adding Features Close to the Bending Lines
Many engineers place tabs, holes, or other additions close to the bend during the manufacturing process. However, you will have to avoid keeping too close to the bendings. Instead, you will have to follow a simple 4T rule. Make sure that all the features are at least 4x material thickness far from the bending lines.
More Emphasis on the Perpendicular Metal Corners
If you bend the sheet metal using a press brake, it will not form a ninety-degree angle. As the tool comes with a rounding tip, it will add the radius to the metal bend. You can measure the bent length area and then divide it by two. You will have the bend radius. If the curve size is essential for the part, you can mention it in the model. The average internal bend radius is 0.030. However, you will have to consider the external radius. It is the one that you can get on the die side of your press brake. It needs to be equal to the thickness of the material plus the internal bending radius. When some designers consider different radius for each bend, others use the same for all the bends. If you use the same radius for all your bends, it will save you on labor.
Not Specifying Hardware Specs in the CAD File
Yes, some engineers do not add the detailed specifications of the hardware to the CAD file. However, you will have to add every detail. We can take the example of the flush-head stud, LS-440-2, and many other things. If you add all the details, you can get the required hardware. It will save time, and you can get the best result as well.
Choosing the Wrong Finish
You might be aware that finishes offer two benefits. They can boost durability and give the part an impressive look. When some finishes serve one purpose, others do both. When the aesthetic finishes focus on appearance rather than corrosion protection, powder coating will offer the best protection against external elements. If you choose silk screening, it will add images and texts to the parts. But it will not serve the protection purpose. But the chemical conversion coating will protect your products. Therefore, you will have to choose the correct finishes based on the part material and environment.
We can take the example of a corrosive environment. In that condition, you can use galvanized metal. That will have protective zinc finishes to work as a shield against external elements. However, you cannot use galvannealed metal. Even if it offers the same protection, it will have dangerous toxins. When it comes to chromate conversion, it will give electrical connectivity to your part, and it will also offer a primer layer. Apart from that, you can use metallic colors to get corrosion-resistant benefits.
Choosing Wrong Metal Sheet
You will have to use the best metal sheet to get durability and other benefits. While selecting metal sheets, you will have to consider the manufacturability, corrosion protection, expected wear and tear, mechanical properties, conductivity, and cosmetic appearance.
Not Considering U-Channel Strength
You will have to consider the strength of the U-channel while designing it. You will have to maintain a minimum 2.1 width-to-height ratio for these channels.
Focusing on Impractical Weld Needs
You will have to make sure that the weld requirements are achievable. Yes, when a welding torch will not access the seam, the weld will not happen. Also, you will have to consider a metal thickness that can withstand extreme heat. Besides, you will have to specify the weld needs by using a nomenclature. You cannot use the box corners to indicate welding.
From the above sheet metal design guide, you might have details about the material requirements, rules, and common mistakes that you need to avoid during the designing process. The most important thing is to choose the correct material, and then you will have to consider the specific design requirements to minimize the cost of fixing errors.