Sheet metal fabrication is a manufacturing process that requires a high degree of accuracy and understanding of the process capabilities, and tolerance. Therefore, you should familiarize yourself with sheet metal design guide before engaging it. Even though sheet metal fabrication is effective, manufacturers must acknowledge and adhere to its limitation in the design stage. Consequently, this will reduce the risk of challenges associated with the process. It will also reduce the production time and cost of the manufacturing process.
To help our customers make the most of our manufacturing services, we put together a comprehensive sheet metal design guide. This design guide will cover the fundamentals of sheet metal fabrication. It will include sheet metal design techniques, material selection, design limitations, and available surface finishes. Read on!!!
What is Sheet Metal Fabrication?
Sheet metal fabrication is a product manufacturing process that involves turning thin, flat pieces of metal into pre-programmed structures. Manufacturers use many sheet metal design techniques to achieve this conversion. These include punching, stamping, cutting, and bending.
The various sheet metal design techniques used by manufacturers ensure versatility while allowing the production of a broad range of parts and products. This, in combination with the sheet metal malleability, shows the vast sheet metal design possible for manufacturers.
Common Application of Sheet Metal Fabrication
Sheet metal parts must be precise, durable, and resistant to environmental factors. These properties are crucial for end-use applications in some industries. Consequently, sheet metal fabrication is used making components used in the automotive, aerospace, medical, and architectural sectors.
Sheet Metal Fabrication Process
Sheet metal fabrication begins with a 3D CAD model. On design specification, authentication, and vesication, the CAD file is converted to machine code. This machine code is responsible for instructing the machine on sheet metal design techniques ideal for raw material manipulations. In conclusion, you can also finish the process by using a range of surface finishing treatments.
Sheet Metal Design Techniques
Before diving into the sheet metal design limitations and tips, below is a brief overview of various sheet metal design techniques used in product manufacturing:
This consists of fitting a sheet of metal between a punch and a die and mounting both of them on a press. Both the punch and die have the same shape. However, they might vary incrementally in size. Therefore, when you press the punch into the die, you will create a hole or depression in the sheet metal.
In sheet metal fabrication, many types of tools are applicable in cutting sheet metal to size. For softer metals, it is even possible to use manual tin snips. However, more sophisticated cutting tools such as high-velocity water jets, lasers, and plasma cutting tools are common in sheet metal fabrication in manufacturing.
In the stamping process, you will place a piece of sheet metal stock on a stamping press. Consequently, it forms the sheet metal into the desired net shape using male and female dies.
As the name implies, bending is a sheet metal fabrication technique that involves bending metal sheets using brakes or presses. The most common types of bending techniques are V-shaped, U-shaped, and channel-shaped forms.
There is a limitation on sheet metal fabrication by the type of sheet metals you can manufacture as sheet stock in terms of materials. The most common materials for the process are steel (especially Stainless steel), Aluminum, and Copper. At RapidDirect, we offer a range of grades for each material:
- Stainless Steel 301, 316/316L, 304.
- Steel 1018.
- Aluminum 5052.
Grades of Copper
- Copper 101, C110, 260 (Brass).
How to Choose the Right Material?
When choosing what material to work with, it is important to consider the properties of each sheet metal type. You should look out for properties such as corrosion resistance, weldability, ductility, conductivity, and cost-effectiveness.
Below are some common materials to work with and their peculiarity.
- Stainless steel offers excellent corrosion resistance and good weldability.
- Aluminum is ductile and cost-effective.
- Copper/Brass alloy is corrosion resistant and conductivity.
Another thing you should note in sheet metal design is the gauge—or the thickness of the metal. Sheet metal thicknesses usually vary between 0.006 and 0.25 inches (0.15 and 6.35 mm). Gauge numbers do not represent the thickness measurement. They generally range from 3 to 38, with the highest gauge number corresponding to the thinnest piece of sheet metal.
Design Limitations for Sheet Metal Fabrication
Sheet metal fabrication is a versatile manufacturing approach for producing a broad range of metal parts. Like all production processes, this technology comes with advantages and disadvantages. However, knowing about sheet metal design means knowing about its limitations and tolerances. Below are important factors that may affect sheet metal product design or maximize sheet metal fabrication.
It is crucial for effective sheet metal design to ensure that the part’s wall thickness is consistent throughout its geometry. This is because the fabrication of parts from a piece of sheet metal occurs via bending, cutting, or stamping into shape.
For effective sheet metal design, wherever possible, it is helpful to ensure that all bends are designed to follow the same direction. Therefore, you won’t need to reorient parts during production. Furthermore, by maintaining the same bend radius across a part’s design, production costs will reduce.
When designing a part with bends, it is also useful to maintain an inside bend radius that is equivalent in size to the sheet metal thickness.
For an effective sheet metal guide, curls are ideal for making safe, rounded edges for parts. When integrating curls into sheet metal design, it is important to make sure that the outside radius of the curl is at least double the sheet metal thickness.
Furthermore, place any holes in the part’s design at a certain distance from the curl (at least the distance of the curl radius + the sheet thickness).
Like curls, hems are important in sheet metal design to make the edges of parts safe for handling. There are a number of hem types. This includes open, flat, and tear-dropped hems. However, unlike curls, which have no raw edge, hems still have exposed edges.
For open hems, the inside diameter should be at least as large as the material thickness. Also, the length of the hem should be at least four times the metal’s thickness. For tear-drop hems, the same measurements apply as well as an opening at least a quarter of the thickness.
When integrating countersinks into sheet metal design, you should consider some factors. This includes the opening angle, the diameter of the hole, and the placement of multiple countersinks.
Though less precise than CNC machining, punch tools are effective and more affordable for producing countersinks. To reduce costs, you should also maintain standard countersink dimensions.
In terms of dimensions, countersinks can be up to 0.6 times the sheet metal thickness. You should place it at least eight times the material thickness from each other. It is also worth noting that countersinks should be at least 4x the metal’s thickness from an edge and three times the thickness from a bend.
In sheet metal fabrication, holes are commonly used for parts that require mounting or wiring. Fabricating the holes can be done either using a drill or punching tool. Punching tools are more cost-efficient. However, it can result in a slight taper at the bottom of the hole.
In sheet metal product design with holes, the hole diameters should be at least as large as the material thickness. To ensure that non-deformation of holes, place the hole at a certain distance from bends (at least 2.5x the metal thickness + the bend radius). Punched holes should also be in at least 2x the sheet’s thickness away from edges to avoid deformed edges.
Notches And Bend Relief
Notching is usually used in sheet metal fabrication to facilitate bends or part assembly. The process uses a punch press to remove material from the outer edge of the metal stock. Bend reliefs, for their part, are useful to ensure that a bend transitioning into a flat surface does not tear or break at their intersection. Bend reliefs should be at least as deep as the radius of the bend and at least as wide as the material thickness.
Sheet Metal Surface Finishes
Sheet metal surface finishing treatments are several optional finishing processes applicable in improving or modifying the surface quality of a part. Surface finishing treatments can alter the aesthetic finish of metal components. They can also change the part’s properties. Therefore, they offer more wear-resistance, better conductivity, etc. Below are some of the sheet metal surface finishing processes you can use with sheet metal fabrication.
This finishing treatment consists of blowing small glass beads against the surface of the sheet metal part in a controlled manner. This technique results in a smooth surface with a matte texture. In bead blasting, various materials—such as sand, garnet, walnut shells, and metal beads—are used to clean parts or prepare them for subsequent surface treatments.
Powder coating involves spraying powdered paint on the sheet metal and then baking it in an oven. Consequently, it forms a durable, wear-resistant, and corrosion-resistant layer. In addition, there are a wide variety of color options available in the powder coating process.
Anodization (Type II or Type III)
Anodization provides excellent corrosion resistance to sheet metal parts. Consequently, it improves the hardness and wears resistance of the surface while dissipating heat. Anodization is the most common surface treatment for painting and priming in sheet metal design due to its high-quality surface finish.
RapidDirect offers two types of anodization: Type II (corrosion-resistant) and Type III (thicker and adds a wear-resistant layer). In addition, both anodization processes allow for a broad range of color finishes.
Chemical Film (Chromate Conversion Coating)
Chemical films are corrosion-resistant and provide good conductivity. The coating process results in a golden surface finish and is predominantly used as a base for paint.
RapidDirect customers can also choose a customized finishing process based on their requirements. Our experts will work with clients to achieve specific finishing requests, such as surface cleaning, enhanced shine, stripping, corrosion resistance, tarnish resistance, and vulcanization.
Sheet Metal Design Tips
Maintain the same bend radii, countersink, and hole diameters across a part’s design. Consequently, this will reduce the need for multiple tool changes, production time, and cost.
Don’t forget reliefs
Bend reliefs are an integral feature in sheet metal design, and they help to ensure that a part meets its design intent without the risk of tearing or breaking. You should integrate these simple design features wherever a bend transitions into a flat surface.
Sheet metal design for manufacturing ensures that design features such as holes, countersinks, and notches are not integrated too close to any bends or edges. Failure to meet these clearances can result in hole deformations and bulging edges.
Check your corners
It is possible to leave sheet metal parts with sharp edges. However, it is more cost-effective to design parts with corner fillets. These fillets should measure about half of the sheet metal’s thickness.
Provide a flat layout
If possible, provide a flat layout of your part’s design to allow for better production planning. A flat layout is essentially what the finished part will look like before it is bent into shape. This layout will include cuts, notches, holes, etc., enabling the manufacturer to better estimate costs and plan out production.