Introduction
Whether in the production of aerospace parts or home appliances, sheet metal dominates as a primary material in contemporary manufacturing. It is an absolute necessity due to its flexibility, high strength-to-weight ratio, and moldability. Not to mention, its full capabilities are only reached through particular custom features added to various parts. One of the most critical, yet simple features is the sheet metal flange.
A flange may appear to be just a bend at the end of a part, but it is much more than that. This specific feature is key to improving the construction and use of parts and provides assistance during assembly. It also increases the quality of flanged parts. Sheet metal flanges are an important part of the sheet metal working process and it is important for engineers, designers, fabricators, and technicians to have adequate knowledge of them.
In this guide, you will learn about the components and concepts concerning flanges: their types, materials, design and manufacturing processes, application, and most importantly optimal methods. Let’s see how this pivotal part influences the outcome of sheet metal projects.
What Exactly is a Sheet Metal Flange?
In basic form, a sheet metal flange is an edge or a raised rim on sheet metal that extends outward. This is usually done by bending or forming the metal to a specific angle, most commonly 90 degrees, although some designs will allow for other bend angles. Imagine it as a folded lip of a component. Like any geometric feature, the function of a sheet metal flange is quite diverse and crucial to the overall quality and performance of the final product.
Reasons to add a flange on a piece of sheet metal are numerous:
Improved Stiffness and Strength: In most cases, this is the main reason for these designs. There is a major resistance to flexing that occurs along the edge and that increases with bending. This also provides deformation along that edge which works like its spine, only locally. Minimal material is added for major gain in rigidity and structural integrity.
Attachment and Mounting Surfaces: Flanges help create flat areas that are mostly perpendicular to the main sheet. These are ideal for setting other components to be bolted, screwed, or riveted onto the outer part of the sheet metal structure.
Edge Treatment (Safety and Finish): A formed edge, particularly a hemmed flange (folded back onto itself), provides a safer edge than a cut edge which is sharp, dangerous or can be rolled to a rounded or reinforced edge.
Sealing Surfaces: Flanges can be designed to accommodate gasket or sealant surfaces, which are very important for creating dust tight, water tight or air tight enclosures, ducts or containers.
Location and Alignment: Flanges can also be used to locate or stop the assembly of components in the right position.
Before we proceed with the discussion of flanges, it is necessary to define some terms:
Flange Face: The surface of the bent portion.
Bend Line: The line that is planned and ought to be drawn on the sheet should initiate the turn.
Bend Radius (Inside): The internal diameter value defining the concave edge of the bend.
Flange Height (or Length): The vertical distance measured parallel in the direction of the concave surface of the turn that connects to the flange – up to its section.
Surface of Gasket: An elastic material is placed to achieve tight borders and the surface of the flange becomes the one for attachment.
Bolt Holes: Circular openings in the flanges are intended to enable bolting the components together.
Types of Sheet Metal Flange
In sheet metal working, flanges are among the most used features that are formed by bending and used for reinforcement, joining or fastening. Key types include:
Angle Flange: A 90 degree bend with an L-shape mainly for stiffness and to offer points of fastening.
Raised Flange: The flange is positioned above the main sheet surface, which can be used for clearance or as a raised base for mounting.
Flat Flange: The flange is in a flat plane with the base plane for flat surface to surface connection or for mounting.
Pipe Flange: A flange that is circular in shape and is used for joining pipes or creating a joint at an opening in the sheet metal with the use of bolts.
Ear Flange / Lug: Small, ear like protruding part from the main body which is used for locating purposes, hanging or merely for fastening purposes.
Flanged Edge: This is a process where the free edge of the sheet is bent in order to strengthen it or to create a joining surface. Its specific form can be different (for example, simple bend, hem).
Grooved Flange: Has a groove on the face of the flange that can be machined or formed for the purpose of accommodating seals such as O-rings for sealing or for positioning with other mating parts.
Hole Flange: It is the raised edge that is created around a hole in the sheet metal. Its main function is to strengthen the area around the opening so that it does not tear, or to provide a surface for a bearing or mounting.
The type of flange depends on the application’s needs, including the strength needed, the way of connection, sealing, tolerance, and how it connects with other components.
Common Materials for Sheet Metal Flanges
The type of material used in the manufacture of a flange has a significant influence on its performance, ease of production, and durability. These are the strength, weight, corrosion, bendability and cost requirements of the material. Common materials choices include:
| Material | Pros | Cons | Common Uses |
| Low Carbon / Mild Steel | – High strength – Good formability – Easy to weld – Low cost | – Heavy – Poor corrosion resistance (unless coated) | – Automotive structures – Appliances – Industrial equipment – Construction elements (with protective finishes or controlled environment) |
| Stainless Steel | – Excellent corrosion resistance – High strength – Maintains properties at elevated temperatures – Clean appearance – Common grades: 304 (standard), 316 (superior corrosion resistance) | – More expensive than mild steel – Harder to form – Increases tool wear | – Food service – Medical equipment – Chemical processing – Marine hardware – Architectural features |
| Aluminum Alloys | – Lightweight (~1/3 density of steel) – Excellent corrosion resistance – Good conductor – Common alloys: 3003 (formable), 5052 (marine), 6061 (stronger) | – Lower strength than steel – Requires larger bend radii – Higher material cost than mild steel | – Aerospace – Automotive panels – Electronic enclosures – Marine structures – Lightweight portable equipment |
| Copper and Brass | – Excellent electrical & thermal conductivity – Good corrosion resistance – Brass(copper-zinc) stronger and more machinable than pure copper | – Expensive – Heavy – Lower strength than steel | – Electrical components (busbars, contacts) – Heat exchangers – Decorative items – Plumbing fittings |
Ductility and yield strength are some of the material properties that affect the design rules. It is important to note that less ductile materials require larger bend radii. Higher strength materials need higher forming force and have more spring back which should be taken into consideration in the manufacturing process, thus need more control.
How Sheet Metal Flanges Are Manufactured?
The predominant method for creating flanges is bending, typically executed on a press brake. A basic understanding of this process illuminates key design constraints. It typically follows these steps:
Design & Material Selection: Define the flange’s required dimensions, angle, and location; select the appropriate sheet metal material and thickness.
Cutting: Precisely cut the sheet metal to the necessary blank size using methods such as shearing, laser cutting, or CNC punching/cutting.
Marking/Programming: Accurately mark the intended bend line on the blank or program it via CNC controls to guide the bending process.
Clamping & Tooling Setup: Securely clamp the workpiece into the forming machine (usually a press brake) and install the correct punch and die tooling suitable for the material and desired bend.
Bending Operation: Use force with the help of the machine, to press the metal with the punch and die in order to bend the flange to the required angle and shape.
Quality Assurance: The formed flange’s angle, height, length should be measured and checked against the designed flange to ensure quality and standardization.
Finishing (As Needed): Any additional operations that may be necessary depending on the application of the part, for example, deburring to remove sharp edges or applying a protective or decorative coating (paint, plating etc.).
Other Methods: Although the press brake is the most common, flanges can also be made by the following methods:
Stamping: Used in progressive or compound dies to form flanges as well as other features on high volume parts.
Roll forming: Produces long lengths of parts with uniform cross-sections (including flanges) by passing the sheet through a series of rolls.
Nevertheless, for the vast majority of discrete sheet metal parts that need flanges, the press brake is still the main working tool.
Key Considerations in Flange Design and Specifications
This is where design intent meets manufacturing reality. Careful attention to these details is vital for successful outcomes.
Flange Height (or Length): Insufficient height is a common cause of manufacturing failure.
Guidelines: Some of the rules that are basic include ”Min Height ≥ 1.5 x T”, while a more accurate rule for press brake forming, which guarantees adequate die contact, is often expressed as ”Min Height ≥ 4 x T + R” (where T=Thickness, R=Inside Bend Radius). There are variations depending on the die geometry, but this rule shows that much more than the thickness is required.
Inside Bend Radius (R): Impacts formability and stress concentration.
General Rule: R ≥ T is a good starting point for most steels to avoid cracking on the outer bend surface.
Material Considerations: Some materials such as some aluminum alloys, high-strength steels are less ductile and hence need larger radii (1.5T, 2T or more). Consult datasheets.
Standardization: Fabricators have standard punch radii. Using these standard radii (for example 0.8mm, 1.6mm, 2.4mm, 3.2mm or their inch equivalents) is less costly than when one has to order for special radii. When a part has consistent bends, it is easier to set up.
Feature Proximity to Bends: Holes, slots, edges cut too close to a bend line will likely distort during forming.
Clearance Rule: Maintain a minimum distance from the feature’s edge to the tangent point of the bend radius. A common recommendation is Min Distance ≥ 3 x T + R. Some sources might use simpler factors like 2T or 2.5T from the bend line itself – clarify which reference point is used.
Bend Relief: When close proximity cannot be avoided, include bend reliefs (small notches or cutouts at the ends of the bend line) for enabling smooth motion of material without altering the feature.
Bend Calculations (Allowance/Deduction): In flat pattern development, it is necessary to take into consideration the material elongation during the bending process. This includes factors such as Bend Allowance, Bend Deduction or K-Factor which are used to determine bend angle, radius, thickness and position of the neutral axis. CAD systems usually perform these calculations, but designers should have an understanding of the principle to guarantee correct generation of flat patterns.
Tolerances: Specify realistic tolerances. Typically, the standard angular tolerance for press brake bends is about +/- 1 degree in either direction. The dimensional tolerances are not very tight and may be in the range of +/- 0.25mm to +/- 0.75mm for normal work. Specifying a very small tolerance that is not required in the application of the part will only add to the manufacturing cost and make the process more complicated.
Consistency: It is recommended to use the same bend radius and, if possible, the same flange height for several flanges in a part stream because it reduces tooling changes and programming.
If these points are addressed during design, then manufacturing issues and poor part quality are minimized.
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At TZR, we are committed to delivering high-quality products, achieving precision up to ±0.02mm. Our adherence to ISO 9000 standards and a 98% product qualification rate demonstrates our dedication to meeting global requirements and client needs. We emphasize quality throughout every stage, offering thorough DFM analysis conducted by reviewers with 30 years of experience. Partner with TZR for reliable and precisely manufactured sheet metal flange.
Diverse Applications of Sheet Metal Flanges
The practical benefits of flanges lead to their use across a vast spectrum of industries and products:
Electronics & Enclosures: Essential for creating rigid chassis and housings. Provide mounting surfaces for PCBs, power supplies, connectors; form seating edges for lids and panels, often incorporating seals.
Automotive: Used throughout vehicle structures for stiffness (body panels, frames), joining components (welding/riveting surfaces), and creating brackets for mounting engine, suspension, and interior parts.
Aerospace: Critical for creating lightweight yet stiff structural elements (ribs, spars, brackets) from aluminum and titanium alloys, where strength-to-weight ratio is paramount.
HVAC: Used in ductwork fabrication to join sections together such as TDC/TDF flanges that enable sealing and mechanical fastening of the ductwork as well as providing additional rigidity to long runs of ductwork.
Appliances: Offer internal support and fastening points for motors and pumps and shelves in washing machines, dryers, refrigerators, ovens, etc., and smooth edges on outer casings.
Construction & Architecture: Used in structural connectors, mounting hardware for facades and roofing, custom brackets and other architectural metalwork.
Industrial Machinery: For machine guards, stiffness, safety edges, equipment frames, mounting plates for motors and sensors, and control panel enclosures.
In other words, where sheet metal must be reinforced, connected, attached or safely chamfered, the flange is the ideal solution.
Common Issues and Best Practices for Sheet Metal Flanges
Designing and manufacturing flanges successfully involves anticipating and avoiding common problems.
Common Issues:
Bend Cracking: Failure of the outer surface due to the radius being too small for the material or bending parallel to an unfavorable grain direction.
Feature Distortion: Holes/slots in the vicinity of the bend zone become distorted due to lack of enough space from the bend area.
Inability to Form: Flange height is below the minimum required for stable die contact.
Angular Inaccuracy: The final angle deviates from specification due to uncompensated springback or inconsistent material properties.
Tool Marks: Any unwanted line or depression on the surface of the part due to contact with the tool or due to pressure exerted by the tool or due to debris.
Flange Waviness/Bow: Lack of flatness along the flange edge, especially on long, thin flanges.
Best Practices:
Minimum Height Standards: Always follow the basic rules of thumb (4T + R for press brake) and check with your fabricator for designs that are close to the minimum.
Select Appropriate Bend Radii: Set R ≥ T as a minimum, and increase R for non-ductile materials; otherwise, use fabricator’s standard bend radii.
Ensure Feature Clearance: Keep at least ≥3T + R or a similar distance or use bend reliefs.
Note Material & Grain: The formability of the material should also be considered. Indicate if the bend orientation with respect to the grain is important.
Provide clear drawings: All dimensions, angles, radii, tolerances, material type and thickness should be clearly indicated.
Maintain Standardization: As far as possible, the radii and flanges should be standard to ease the manufacturing process.
DFM (Design for Manufacturability): Consult with your sheet metal fabricator as early as possible. It can help them to detect problems and adapt the design to their processes, thus reducing time and money spent and increasing quality.
These practices change orientation from solving problems to designing solutions, which results in more dependable and less expensive solutions.
Conclusion
The sheet metal flange is one of the basic components of the design, but it is not a simple one at all. It is a basic component that provides support, allows connection and shapes a wide range of products in the manufacturing process. From the basic definition of flanges to the finer details of materials, manufacturing methods, and design parameters, it is impossible to design sheet metal parts without a good understanding of flanges.
In conclusion, the use of sheet metal flanges depends on the design, material properties, and manufacturing process knowledge. Thus, engineers and designers can go on using this simple yet effective feature to develop new, efficient, and high-quality sheet metal products.
