Prototek’s Sheet Metal Design Guide

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Prototek is a leading on-demand digital manufacturer specializing in precision sheet metal, CNC machining, and additive manufacturing. A one-stop shop for your custom prototyping and manufacturing needs. We have multiple locations throughout the USA and an expansive International Manufacturing Partner Network. This Sheet Metal Design Guide will help you with designing the best possible prototypes and parts.

We can get your ideas made with too many capabilities to list and materials ranging from titanium and steel to acrylic and nylon. Across the nation, our dedicated staff is here to serve the engineers and innovators who are creating tomorrow’s industrial world.

Get a quote on your next sheet metal project. Or contact us for more information at 1-800-403-9777 or [email protected].

What Is precision sheet metal fabrication?

When people talk about sheet metal fabrication, they discuss the process used to manipulate materials to create a sheet metal component used in an end product. It involves material being cut, formed, and finished. Sheet metal fabrication is used in every manufacturing field, notably in medical equipment, computers, electronics, and appliances. Essentially, anything that is constructed out of or contains metal will have gone through these processes:

Cutting

There are several ways that we can cut sheet metal into smaller pieces. Shearing involves a cutting machine using shear stress to cut down a large portion of material into smaller. Electrical discharge machining (EDM) involves conductive materials being melted with a spark from a charged electrode. Abrasive cutting consists of grinders or saws to cut through the material. And laser cutting consists of using a laser to achieve precise cuts in sheet metal.

Forming

After the metal has been cut, it will be formed into the desired shape for the needed/necessary components. There are several techniques of forming that can be used. Rolling involves flat pieces of metal being shaped repeatedly with a roll stand. Bending consists of the material being manipulated by hand. Stamping consists of the use of tools to stamp designs into sheet metal. Punching involves holes being put into the surface. And welding involves one piece of material being joined to another using heat.

Finishing

Once the metal is formed, we will pass it through a finishing process to ensure it is ready for use. This step will involve sharpening or polishing the metal with an abrasive to remove or eliminate rough spots and edges. This process may also include the metal being cleaned or rinsed to ensure that it is spotless when it gets delivered to the factory for its intended purpose.

Sheet metal fabrication is essential in creating any component that contains metal (from your laptop to the paper clips holding your files together). If you do not have the time or the resources to fabricate your materials, you can employ a specialist fabricator to do this for you. We can do this for you, giving you more time to focus on creating your products, but it will ensure that you receive the best finish possible on your metal components.

Metal fabrication is the creation of metal structures through cutting, bending, and assembling processes. It is a value-added process involving creating machines, parts, and structures from various raw materials.

Typically, a fabrication shop bids on a job, usually based on engineered drawings, and if awarded the contract, builds the product. Large fabrication shops employ many value-added processes, including welding, cutting, forming, and machining.

Metal fabrication usually starts with drawings with precise dimensions and specifications. Contractors, OEMs, and VARs employ fabrication shops. Typical projects include loose parts, structural frames for buildings, heavy equipment, stairs, and hand railings.

As with other manufacturing processes, both human labor and automation are commonly used. A fabricated product may be called a fabrication, and shops specializing in this type of work are fab shops. These end products of other common types of metalworking, such as machining, metal stamping, forging, and casting, may be similar in shape and function, but these processes are classified as fabrication.

Sheet Metal Materials

The materials we work with include ESD-safe plastics and metals including titanium, gold, copper, and stainless steel.

We also work with ABS, Corzan, Delrin®, Ertalyte®, Kevlar, Kynar®, Lexan®, Nylon, PE, PP, PU, PlexiGlas®, PVC, Radel®, Ryton®, Semitron, Torlon®, Ultem®, Vespel®, and Victrex®.

Design Considerations

The following sections address common areas. By aligning to better designs, you can often save money on the cost of a part.

Corners

Full Overlap: Typically chosen when welding is not needed. Ensure proper bend relief is being used at the intersection of the two bends. This corner construction is the most economical choice and should be chosen where there is no need to secure the corner of a sheet metal part.

Half-Lap: This is preferred for steel and stainless parts when welding is required. A half-lap will allow for proper weld penetration and limit the amount of heat needed when welding, which will help reduce distortion. An appropriate bend relief is required for half-lap corner construction.

Open Corner: Is chosen for Aluminum parts where a full weld penetration is essential. Typically, there is no need for bend relief when an open corner construction is desired. Open corner construction can also be used for other materials where parts are subject to high-stress environments.

SpotWeld Flanges: Another popular choice for corner construction. This construction is not seamless like fully welded corners but can be a more economical option. Proper bend relief and alignment holes should be considered when choosing to add spot weld flanges. Alignment holes can be filled with weld and ground smooth if required.

Pop Rivet Flanges: Similar to spot welds, flanges are typically the most economical choice to secure the corners of a sheet metal part. Holes are added through the walls with flanges where pop rivets are inserted to secure the corner.

Bends

Adding bends to a flat sheet of metal transforms that metal into a three-dimensional piece.

Best practices recommend maintaining the same bend radii across all bends if possible. Standard bend radius is 0.030 inches. Our machines can hold a ± 1 degree tolerance on all bend angles.

Part Example | Best Practices

Part Example | Outside Best Practices (Increased Complexity)

Wall Thickness

Wall thickness refers to the overall thickness of the metal being used to create the part. Sheet metal parts are made from a single sheet of metal. This means the part needs to maintain a uniform wall thickness.

Best practices require that part designs maintain a uniform thickness due to being created from a single sheet of metal.

Part Example | Best Practices

Part Example | Outside Best Practices (Increased Complexity)

Bend Relief

Bend reliefs help strengthen transitions from bend to flat surface (or from bend to another bend) in sheet metal. When a bend is made close to an edge, there is a risk the material may tear. Bend reliefs are minor cuts in the material perpendicular to the bend to help prevent tearing.

Best practices bend reliefs a) are no deeper than the thickness of the material plus the bend radius b) no wider than 0.030 inches.

Part Example | Best Practices

Part Example | Outside Best Practices (Increased Complexity)

Slots and Holes

Slots and holes generally need to follow guidelines around sizing and be placed at specific distances from edges and bends to avoid material warping and maintain structural integrity. If hardware inserts are required, spacing should be according to the manufacturer’s specifications.

Best practices for Slots include a) slot diameters should be at least as large as the material’s thickness, b) slot placement should be at least 4x material thickness plus the bend radius away from any bends, and c) placement of at least 2x material’s thickness away from the edge.

Best practices for Holes include a) hole diameters should be at least as large as the material’s thickness, b) holes should be at least 2.5x material thickness plus the bend radius away from any bends, c) at least 2x material’s thickness away from an edge, and d) should be separated from each other by at least 2x material’s thickness.

Part Example | Best Practices

Part Example | Outside Best Practices (Increased Complexity)

Tabs and Notches

Notching is a metal-cutting process used on sheet metal or thin bar-stock, sometimes on angle sections or tubes. A shearing or punching process is used in a press to cut vertically down and perpendicular to the surface, working from the edge of a workpiece. Sometimes the goal is merely the notch itself, but usually, this is a precursor to some other process: such as bending a corner in a sheet or joining two tubes at a tee joint, notching one to fit closely to the other.

What is the difference? Notching is a metal-cutting process in which an intrusion or cut is made on the edge of the sheet metal, while a tab feature is created by adding material to the walls of a sheet metal component.

Best practices for Notches a part will have notches that a) are at least the material’s thickness or b) at least .04 inches and c) do not have a length more than 5x the width for material strength.

Best practices for Tabs are a) at least ½x the thickness of the material or b) at least 0.126 inches and c) do not have a length more than 5x the width for strength reasons.

Part Example | Best Practices

Part Example | Outside Best Practices (Increased Complexity)

Hems

Hemming in sheet metal fabrication is when the edge of the sheet is folded back on itself or folded over another part to fasten two sheet metal parts. Hemming may improve the appearance of a part, reinforce part edges, or increase the part stiffness. Hems can be open or closed.

Best practices for Hems tolerance depends on the hem’s radius, the thickness of the material, and features near the hem. Best practices recommend a minimum inside diameter equal to the thickness of the material and a return length of 4x the thickness of the material.

Part Example | Best Practices

Part Example | Outside Best Practices (Increased Complexity)

Countersinks

Countersinking is used for holes that need to accept a flat head screw or fastener when the hardware needs to be flush with the part’s surface. They can be created either using machines like a drill press or formed with a punch press tooling.

Best practices for Countersinks include a) tolerances of ± 0.010 inches for machined countersinks and b) tolerances of ± 0.015 for formed countersinks.

Part Example | Best Practices

Part Example | Outside Best Practices (Increased Complexity)

Welding

Welding in sheet metal is used to seal the edges of bent parts. Prototek offers resistance spot welding (RSW), gas metal arc welding (MIG), and gas tungsten arc welding (TIG). The type of welding will vary for each project.

Best practices for Welding can generally save money and time by allowing the manufacturer to determine the best welding method for your particular part. When specific types of welding are needed, it can increase the project’s complexity.

Part Example | Best Practices

Part Example | Outside Best Practices (Increased Complexity)

Offsets

Offsets are a double bend on a piece of sheet metal that adds a second tier to your part, typically shaped like a “z.”

Best practices for Offsets include:

0.030 inches
0.060 inches
0.093 inches
0.125 inches
0.187 inches
0.213 inches
0.250 inches
0.281 inches
0.312 inches

Offset height tolerance is ± 0.012 inches from the top of the sheet/top of the form. *Prototek also offers custom offsets.

Part Example | Best Practices

Part Example | Outside Best Practices (Increased Complexity)

Link for hardware catalog.

Additional Resources – Call Prototek at 1-800-403-9777

Have you ever received a no-bid on your prototype?

Many companies will no-bid complex forming operations or no-standard materials because of the expertise and machining needed to be able to deliver on it cost-effectively.

Are you ready to start a project?

Get a quote on a sheet metal project from Prototek or call 1-800-403-9777

FAQs

What questions should I be asking a sheet metal prototyping company?

What is your current capacity?
What is your turn time?
Can you provide an NDA?
Do you quote from a solid model or drawings?
When can I expect my quote?
What materials do you work with?
What are your standard tolerances?
Do you install inserts?
Do you do TIG welding?
Do you do any finishing?
Do you provide silk screening and assembly services?
Do you design work or do reverse engineering?
What are your standard radii?

What are some common reasons companies reject sheet metal prototypes?

Length or width issues
Thickness (too thin or too thick)
Material type
Tight tolerances
Special tooling or forming that require tools or skills
The company does not have certifications to meet the requirements of the part
Machine limitations

What makes Prototek different is our ability to handle most complex jobs – having the capability to quote most any prototyping project across processes and finishes.

How fast can Prototek respond to a quote?

In most cases we will get back to you within 24 hrs. If all the information required is not provided we will contact you. If you require a quote much faster please contact us by calling and speak to one of our team members. Our phone number is 1-800-403-9777.

What types of metals can be used for sheet metal forming?

Cold rolled steel, hot rolled steel, aluminum, stainless, copper, brass, beryllium, titanium, and galvanized.

What are the common sheet metal material thickness ranges?

.005, .006, .010, .017, .020, .023, .025, .030, .032, .036, .040, .042, .048, .050, .059, .060, .063, .074, .063, .074, .075, .080, .090, .100, .104, .105, .134, .135, .160, .179, .188, .190, .239, .239, .250, .312, .437, .500, .625

What are minimum and maximum dimensions in inches?

We will discuss your dimension needs directly with you.

What are tolerances?

Tolerances is a limit or limits of a physical dimension, measured value or physical property of a material or manufactured object.

What is air bending verses coining?

Air bending is a method where material is forced into a V-die opening requireing less bend force and tonnage. You can use smaller tooling and the angle of the tool is less important. air bending requires a little more attention as the angles will not be as consistent and require forming to a more acute angle due to spring back.

Prototek uses a press brake tool for air bending, coining and bottoming. We can also work with designs needing three-point bending, folding, wiping, rotary bending, rol bending, elastomer bending, and joggle bending. Coining involves using tonnage to conform the material to the exact angle of the punch and die. Coining is used more in production where a lot of parts will be manufactured and need to hold exact tolerances and precise angle of your tooling.

What is stitch welding?

Stitch welding or intermittent welding involves initiating a weld, typically indicated on a drawing, terminating the weld and then starting again along the joint a specified distance from the previous weld. Stitch welding can be used when air or liquid tightness (Seal) is not a requirement, when structural integrity is not a concern or to control heat.

What is plating?

Plating provides many benefits to products made from metal and other materials. Plating is a manufacturing process in which a thin layer of metal coats a substrate. This can be achieved through electroplating which requires an electric current or. through electroless plating which is an autocatalytic chemical process.

What is Prototek's finishing process?

Prototek utilizes a multi-step process of anodizing and finishing which includes cleaning, treatment, anodizing, coloring, sealing, and numerous quality rinses in between each phase. We focus on controlling the pH, temperature, concentration, frequency, and duration. Our technicians maintain multiple controls in the tank to ensure a consistent, quality coating. As industrial craftsmen, these processes and quality phases are the art and science we take pride in delivering high-quality parts to our partners.

Prototek offers: