Design Guidelines: Sheet Metal Fabrication

Sheet metal fabrication is a versatile manufacturing process used to create parts by cutting, bending, and assembling thin metal sheets, suitable for a wide range of industries such as automotive, aerospace, and electronics.

To ensure optimal results, it’s important to consider factors like material selection, thickness, and design for manufacturability (DFM) when designing for sheet metal fabrication.

Material selection and thickness considerations
Design for ease of bending and cutting
Tolerance and edge finishing requirements

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Size

Maximum Dimensions

	Metric	US
Size	990.6mm x 1,193.8mm	39 in. x 47 in.
Bend Length	1,193.8mm	47 in.

Minimum Dimensions

	Metric	US
Formed Part	12.7mm x 12.7mm	0.500 in. x 0.500 in.
Flat Part	6.35mm x 6.35mm	0.250 in. x 0.250 in.

Materials

1. Aluminum
2. Brass
3. Copper
4. Stainless Steel
5. Steel: CR Non-treated
6. Steel: CR Galvanneal and CR Galvanized

Z Frame

Looking to transform flat metal sheets into fully formed three-dimensional parts? Our functional design aid, featuring countersinks, punch-outs, powder coating, and silk screening, provides all the guidance you need. The Z Frame highlights sheet metal fabrication processes and key design elements to enhance the structural integrity and aesthetics of your parts—and it even doubles as a handy desktop organizer.

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Tolerances

Single Surface

	Metric	US
Bends	+/- 1 degree	+/- 1 degree
Offsets	+/- 0.304mm	+/- 0.012 in.
Hole Diameters	+/- 0.127mm	+/- 0.005 in.
Hardware to edge/hole	+/- 0.254mm	+/- 0.010 in.
Edge to edge/hole; hole to hole	+/- 0.127mm	+/- 0.005 in.
Hardware to hardware	+/- 0.381mm	+/- 0.015 in.
Bend to edge	+/- 0.254mm	+/- 0.010 in.
Bend to hole/hardware/bend	+/- 0.381mm	+/- 0.015 in.

Multiple Surface

	Metric	US
Features separated by two or more bends	+/- 0.762mm	+/- 0.030 in.

Sheet Metal Material Thickness Range

\Sheet metal parts are formed from a single sheet of metal, requiring a uniform wall thickness throughout. Thickness typically ranges from 0.024 inches (0.609 mm) to 0.250 inches (6.35 mm).

Steel			Stainless			Aluminum		Copper		Brass
CRS/HRPO*	Galvanneal	Galvanized	304-2B	304-#4	316-2B	5052-H32	6061-T6	C101	C110	C260
0.024	0.028	0.028	0.024	0.024	0.024	0.025	0.025		0.025	0.025
0.030	0.034	0.034	0.029	0.029	0.029	0.032	0.032	0.032	0.032	0.032
0.036	0.040	0.040	0.036	0.036	0.036
0.042						0.040	0.040	0.040	0.040	0.040
0.048	0.052	0.052	0.048	0.048	0.048	0.050	0.050	0.050	0.050	0.050
0.060	0.063	0.063	0.060	0.060	0.060	0.063	0.063	0.064	0.062	0.063
0.075	0.079	0.079	0.075	0.075	0.075	0.080	0.080	0.080	0.080	0.080
0.090	0.093	0.093	0.090	0.090	0.090	0.090	0.090	0.093	0.093	0.093
0.105	0.108	0.108	0.105	0.105	0.105	0.100	0.100
0.120	0.123	0.123	0.120	0.120	0.120	0.125	0.125	0.125	0.125	0.125
0.135*	0.138	0.138	0.135	0.134	0.135
0.164*			0.165			0.160	0.160
0.179*			0.187			0.190	0.190
0.239*			0.250			0.250	0.250

*These thicknesses are available as Hot Rolled, Pickled & Oiled (HRPO) only

Surface Finishing

We provide a wide range of sheet metal finishing options, including welded assemblies, edge breaking, standard mill finishes, and orbital-sanded surfaces:

Powder Coating: Available in textured and non-textured finishes, with a variety of colors, including RAL options.
Plating: Includes anodizing, chromating, zinc coating, and passivation.
Welding: Seam, tack, and stitch welding for durable assemblies.
Hardware Insertion and Riveting: Standard PEM hardware and POP-riveted assemblies.
Silk Screening: One- and two-color options with colors matched closely to most Pantone numbers.
Assemblies: POP-riveted and welded for added strength and functionality.

fabricated assemblies metal part different types of surface finishing

Guide for Sheet Metal Surface Finish

Explore our sheet metal guide for an overview of the standard and cosmetic finishing options available for different sheet metal materials.

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Design Guidelines for Bending

These guidelines are created to support product designers in understanding sheet metal fabrication and identifying the main factors that impact part quality and consistency. Applying this knowledge in your project can help control costs, meet visual expectations, and maintain high precision throughout production.

Brake Lines

Rake lines are a common result of the force applied to sheet metal during the bending process, typically performed using a press brake. These lines are inherent to the manufacturing process and will remain on the final product unless additional treatments are applied.

To remove these brake lines, a direct oscillating sanding device can be used. For parts requiring specific aesthetic qualities or a cosmetic finish, several secondary processing options are available:

Using a direct oscillating (DA) tool to blend the brake line into the surrounding material.
Placing a rubber slip sheet on top of the die tooling during the bending process.
Applying a finish, such as powder coating, after forming to cover the entire surface of the part.
Note: Plating thickness is often not sufficient to cover brake lines, so these lines may still be visible after plating.

If your part requires a uniform finish with no visible brake lines, please contact our applications engineers to explore the best method for your specific needs.

Bent sheet metal showing visible press brake lines.

A direct oscillating sanding tool can effectively eliminate brake lines.

Feature Proximity

When sheet metal is bent in a press brake, the material naturally stretches along and near the bend line. Any feature located within a certain proximity of the bend—usually within 4 times the material thickness from the bend—is at risk of deformation.

However, there are several design strategies that can mitigate this issue and help you achieve your intended design outcome. Below are common design solutions for addressing this challenge:

Possible Solutions	Rationale for Using this Solution
Allow the feature to deform during bending	This solution is only recommended if deformation is acceptable, such as in cases where the feature’s criticality is low or during early prototyping. Future design changes can resolve the issue. Protolabs’ design for manufacturability analysis may suggest feature deformation as a viable option. Before manufacturing begins, our sheet metal fabrication experts will evaluate all potential deformation scenarios and contact you if any concerns arise.
Change the bend radius	Opting for a smaller internal bend radius when features are close to, but not directly through, the bend can reduce material stretching at the bend. A smaller bend radius helps to minimize deformation risks. Consult our list of available internal bend radii to choose the best option for your design.
Re-locate/move the at-risk feature	The most common solution when dimensional accuracy of the feature is essential. This approach involves repositioning the feature to a location where it is less prone to deformation. Our design for manufacturability toolkit provides a reference guide that outlines minimum feature distances based on material type and thickness, helping avoid distortion issues.

In most cases, these design solutions do not significantly affect the cost or lead time of your project, but they can help avoid additional processing costs over the lifespan of your part.

Not sure which solution is best for your design? Our sheet metal experts are available to offer a free 30-minute design review, with same-day appointments available!

When features, such as the fan bracket and bottom holes, are too close to a bend, the sheet metal will experience deformation during the bending process.

In this case, reducing the size of the internal bend radius effectively provided the extra material needed, preventing deformation of the fan cutout and holes.

Extending Features

One more option to prevent deformation along bends is to extend a feature through the bend.

In images A and B (below), the bracket has two L-shaped cutouts that terminate at the bend. The material experiences deformation where the top of each L intersects with the bend.

image A

image B

By following the feature distance guidelines outlined in the “Placing Features Near Bends” section of our sheet metal DFM toolkit, deformation can be eliminated by extending the L-shape through the bend line. This method removes the material where the bend would typically occur, as demonstrated in images C and D below.

image C

image D

Minimum Flange Lengths

To ensure an accurate bend in a press brake, the design must make three (3) points of contact with the machine. The image to the right highlights these crucial points of contact.

If only two points of contact are made, the final part may experience a deformed flange. For example, in the image below, the “H” bracket’s center portion has two flanges on the z-axis, which didn’t make three points of contact during the bending process. This resulted in inconsistent and deformed bends.

points of contact with the machine for bending design

The center portion of this “H” bracket demonstrates quality issues due to insufficient material on the z-axis flanges, leading to bending inconsistencies.

By adding material to a short flange, the workpiece can make three points of contact with the press brake, ensuring consistent and accurate bending.

Hardware Inserts

Including hardware inserts in your sheet metal design is an effective and affordable solution for joining components. However, when placing hardware holes and inserts near bend lines, it is crucial to account for potential deformation during the bending process.

If hardware holes are too close to a bend, the material will stretch, which may impact the integrity and functionality of the insert. The mounting bracket below demonstrates how the bending process can influence hardware positioning and installation.

To overcome this challenge, a recommended approach is to adjust the design by moving hardware holes further from the bend line or considering alternative insertion methods that ensure secure functionality even in challenging bending scenarios. This proactive design strategy can help avoid deformation and maintain the effectiveness of hardware inserts.

This mounting bracket has laser-cut holes along the bend line, causing the holes to become oblong (non-round) after forming.

As a result, the hardware inserts won’t properly seat into the holes, preventing them from gripping the component material and impacting the functionality of the insert and the overall design.

The term “relief” is commonly used in sheet metal manufacturing, especially in the context of “bend relief,” but it can also apply to other design situations. Relieving sheet metal involves strategically placing cut-outs to enable material stretching during bending, preventing distortion of critical features.

For hardware holes near bends, adding cutouts around the hole allows for material relief during bending, preventing distortion. This approach helps maintain the design intent while keeping costs low.

Considering material relief during the design phase offers several benefits, such as:

Preventing material tears and cracks along bend lines or stress points like corners
Reducing quality issues like warping or feature deformation that can impact dimensional accuracy
Ensuring consistent production quality from part to part and order to order
Improving durability and performance by reducing material stress
Avoiding interference issues during assembly by ensuring proper fit where parts or components meet

KingStar Mold’s Capabilities

Bend Radius

We maintain a tolerance of +/- 1 degree on all bend angles and offer a variety of common bend radii. Our standard options include 0.030 inches (0.762 mm), 0.060 inches (1.524 mm), 0.090 inches (2.286 mm), and 0.120 inches (3.048 mm), with tooling available on a 3-day lead time. For optimal results, it is advised to use consistent radii across all bends. Additionally, the minimum flange length for sheet metal parts must be at least four times the material thickness.

Hems

We produce both open and closed hems, with tolerances influenced by the hem’s radius, material thickness, and nearby features. For best results, we recommend a minimum inside diameter equal to the material thickness and a hem return length of six times the material thickness.

Offsets

Offsets are used to create Z-shaped profiles in sheet metal parts, with a height tolerance of +/- 0.012 inches (0.304 mm) from the top of the sheet to the top of the form. We recommend a standard offset of 0.030 inches (0.762 mm).

Additional standard options include offsets of 0.060 inches (1.524 mm), 0.093 inches (2.362 mm), 0.125 inches (3.175 mm), 0.187 inches (4.749 mm), 0.213 inches (5.410 mm), 0.250 inches (6.35 mm), 0.281 inches (7.137 mm), and 0.312 inches (7.924 mm).

Holes and Slots

Holes and slots should have a minimum diameter equal to the material thickness. For materials 0.036 inches (0.914 mm) or thinner, holes should be at least 0.062 inches (1.574 mm) from the material edge. For thicker materials, the minimum distance increases to 0.125 inches (3.175 mm) to prevent distortion. If hardware inserts are needed, spacing should follow the manufacturer’s specifications.

Notches and Tabs

Notches should be at least the material thickness or 0.04 inches (1.016 mm), whichever is greater, and their length must not exceed five times their width. Tabs must measure at least twice the material thickness or 0.126 inches (3.200 mm), whichever is greater, with a maximum length of five times their width.

Countersinks

We provide both machined and formed countersinks, which are conical holes designed to allow screws, nails, or bolts to sit flush with the surface.

For optimal results, we recommend major diameters between 0.090 inches (2.286 mm) and 0.500 inches (12.7 mm) with standard angles of 82°, 90°, 100°, or 120°. The tolerance for the major diameter of formed countersinks is +/- 0.010 inches (0.254 mm).

Frequently Asked Questions

How does KingStar Mold ensure high-quality sheet metal fabrication?webadmin2025-04-09T06:41:40+00:00

How does KingStar Mold ensure high-quality sheet metal fabrication?

KingStar Mold utilizes advanced technology and experienced engineers to ensure precision in sheet metal fabrication. We maintain strict quality control throughout the entire production process, from material sourcing to final inspection, ensuring consistent, high-quality parts for every project.

What are the advantages of using laser cutting in sheet metal fabrication?webadmin2025-04-09T06:40:35+00:00

What are the advantages of using laser cutting in sheet metal fabrication?

Laser cutting offers high precision and a clean edge, making it ideal for intricate designs and small parts. It is also faster than traditional methods like punching and can cut through a wide range of materials, including metals, plastics, and even ceramics. Laser cutting minimizes material waste and can handle complex geometries, reducing the need for further processing.

How do I choose the right sheet metal for my project?webadmin2025-04-09T06:39:08+00:00

How do I choose the right sheet metal for my project?

Choosing the right sheet metal is crucial for the success of your project. Key factors include material type, thickness, corrosion resistance, and formability. Common materials like steel, stainless steel, aluminum, and copper each have distinct advantages depending on your project’s requirements, such as strength, weight, and environmental exposure.

Consider the thickness of the material based on strength and workability, with lighter gauges ideal for general use and heavy gauges suited for structural applications. For projects exposed to moisture or harsh chemicals, corrosion-resistant materials like stainless steel or aluminum are essential.

Additionally, factors such as the cost, aesthetic finish, and the specific manufacturing processes (like bending or welding) should influence your choice. Understanding your project’s environmental and durability needs will ensure you select the best material, balancing both performance and cost.
For more detailed guide, refer to this post: How to Choose the Right Sheet Metal for Your Project and if you need detailed data sheets, refer to this page: Sheet Metal Materials

What is the role of bend allowance in sheet metal design?webadmin2025-04-09T06:31:46+00:00

What is the role of bend allowance in sheet metal design?

Bend allowance is the amount of material that is required to be added to the flat pattern of a sheet metal part to account for material stretching during the bending process. It ensures that the final bent part fits as intended. The bend allowance depends on the material thickness, bend radius, and the angle of the bend.

How do I ensure the holes near bends remain round after forming?webadmin2025-04-09T06:31:05+00:00

How do I ensure the holes near bends remain round after forming?

To maintain the shape of holes near bends, you can place cutouts or relief areas around the hole to allow the material to stretch without distorting the hole. This helps maintain accuracy and prevents oblong or irregular holes.

How do I prevent deformation of features near a bend?webadmin2025-04-09T06:30:16+00:00

How do I prevent deformation of features near a bend?

Deformation of features near bends is a common challenge in sheet metal fabrication. It happens because of the material stretching or compressing as it’s bent, which can affect the overall quality and functionality of the part. In this article, we’ll discuss practical ways to prevent such deformation, ensuring the part maintains its structural integrity and dimensional accuracy.

1. Understanding Deformation Near Bends

When a sheet of metal is bent, the material near the bend line experiences a stretch on the outer radius and a compression on the inner radius. Features that are close to the bend line (typically within 4x the material thickness) are susceptible to distortion, as the bending process alters their shape. This can result in a variety of issues, such as:

Holes becoming elliptical or misshaped
Features being stretched or deformed beyond their intended dimensions
Loss of accuracy in critical features like cutouts or slots

Preventing this deformation is crucial to maintaining part functionality and aesthetics.

2. Design Solutions to Prevent Deformation

Relocate Features Away from the Bend Line

The most straightforward solution is to move any features (holes, slots, or cutouts) away from the bend line. Keeping features at a sufficient distance from the bend line ensures they won’t be subject to the stresses and stretching that occur during the bending process.

A common rule of thumb is to maintain a minimum distance of 4 times the material thickness from the bend. This distance may vary depending on the material type and thickness, but this guideline serves as a good starting point.

Example: If you have a sheet of metal that is 2mm thick, features should be placed at least 8mm away from the bend line.

Use Bend Reliefs

Bend reliefs are cutouts or notches placed at the bend area to help relieve stress and prevent material tearing during the bend. These reliefs create space for the material to stretch without distorting the surrounding features.

Internal Relief: This type of relief is applied to the inner part of a bend, where material compression occurs.
External Relief: Used on the outer radius of the bend, this relief allows material stretching without pulling features out of shape.

Bend reliefs are especially useful when features are unavoidable near the bend line. They allow the material to stretch without negatively impacting the design.

Increase Bend Radius

Reducing the severity of the bend radius can help mitigate material stress. A smaller internal bend radius leads to a more gradual bend, which in turn reduces the stretching and compression on the metal. If features are located near the bend, a larger bend radius will help reduce the risk of deformation.

Example: Using a larger internal bend radius (e.g., 1x or 2x the material thickness) can allow for a smoother, more controlled bend, reducing the likelihood of deformation in the surrounding features.

In many cases, adjusting the bend radius doesn’t impact the overall part cost or lead time significantly, but it can improve the quality of the part and reduce the need for post-processing adjustments.

Consider the Material Type

Different materials behave differently during the bending process. For instance, some metals, like aluminum, are more ductile and may stretch more easily, while others, like stainless steel, may be more prone to cracking. The material’s thickness, hardness, and grain direction all affect how it will respond to bending.

To prevent deformation, consider the following:

Use more ductile materials for parts with features near bends.
Increase the thickness of the material if possible. Thicker materials are less likely to deform during bending.

Add Extra Material for Short Flanges

In situations where a short flange is close to a bend, adding extra material to the flange can provide sufficient support. This ensures that the flange makes three-point contact with the press brake during bending, leading to a more consistent and accurate bend.

Example: By extending the flange, you create a scenario where the material makes three points of contact with the press brake, reducing the chances of deformation or a bent flange.

Design for Manufacturability (DFM) Analysis

A Design for Manufacturability (DFM) analysis is a critical step in identifying potential issues in your design. By working closely with your manufacturer or using DFM software, you can review your design before fabrication begins. DFM tools can help identify areas at risk for deformation and provide recommendations for improving part manufacturability.

Prototyping and virtual simulations can help visualize how the bending process will affect features and make adjustments early in the design phase.

3. Post-Bend Processing Options

In some cases, the deformation cannot be entirely avoided during the bending process, but you can use post-bend processing to correct the issue. Common post-bend techniques include:

Sanding: To smooth out imperfections or remove any surface distortion caused by bending.
Heat Treatment: In cases where material stress has affected the part’s integrity, heat treatment may be used to relieve the stress and return the part to its intended shape.
Finishing: Applying coatings or finishes such as powder coating or plating may help hide any minor deformations and enhance the part’s aesthetic quality.

4. Collaborating with Experts

If you are unsure about the best way to prevent deformation in your part, working with a sheet metal fabrication expert can help. Manufacturers can provide valuable insights into material selection, design adjustments, and potential post-processing methods.

At KingStar Mold, our sheet metal fabrication experts are available for a free consultation. We’ll help you optimize your design to ensure the best possible result while avoiding unnecessary deformation and improving part performance.

By considering these strategies during the design phase, you can significantly reduce the risk of deformation near bend lines and ensure that your sheet metal parts meet both functional and aesthetic requirements.