Sheet metal bending is a versatile and efficient process that can be used to create a wide variety of products. Whether you are a beginner or an experienced manufacturer, this article will help you to understand the basics of sheet metal bending and to produce high-quality parts safely and efficiently.
This guide will explain the several types of bending operations, the advantages and disadvantages, the equipment used, and the safety guidelines that should be followed. Let’s get started by defining the process.
What is sheet metal bending?
Sheet metal bending is a manufacturing process that uses force to change the sheet metal into a shape. This is done to achieve the desired form or shape needed for a manufacturing process. The external force used alters only the external features of the sheet.
Overall, sheet metal bending is a useful and versatile manufacturing process. It is used in a wide variety of industries. It is an inexpensive process, but it is important to follow safety guidelines when operating sheet metal bending equipment.
Key features of sheet metal bending operations
Bending force: Presses or brakes provide clamping force and bending force via a punch and die to bend the material.
Material deformation: The sheet metal exceeds its yield strength and plastically deforms to take the desired shape.
Spring back: The material’s elasticity causes some rebound after bending that must be accounted for in the bend programming.
Bending radius: The smaller the radius between bent flanges, the greater force required and likelihood of cracks.
Bend allowance: Extra length must be added to account for the bend radius when programming bend locations.
Tooling: A punch and die matching the desired bend shape must be used, like box and pan finger tooling or wipe dies.
Grain orientation: Bending against the sheet metal grain orientation takes more force and risks cracks.
Applications: Bending creates enclosures, chutes, brackets, channels, clips, housings, and innumerable component shapes.
What is sheet metal bending used for?
Sheet metal bending is an essential process in the manufacturing of many products. It enables efficient, high-strength fabrication of parts that would be difficult or impossible to make using other processes.
Here are some of the things that sheet metal bending is used for:
- Brackets: Bent metal brackets to provide mounting points and support structures
- Frames: Bending forms, the basic frames for enclosures, boxes, chassis, machinery guards, and display cases
- Chutes: Formed sheet metal chutes to guide parts or materials through processes
- Clips: Small bent metal clips that provide retention and fastening functions
- Channels: U-shaped channels used for supporting, mounting, and material handling
- Housings: Metal housings for motors, pumps, electronics, junction boxes, and equipment enclosures
- Panels: Bending sheet metal to form control panels, covers, doors, and partition panels
- Guards: Formed guards as barriers around mechanical equipment and moving parts for safety
- Heat shields: Bent aluminum or steel panels surround hot components like exhaust pipes
- Signs: Bending forms metal sign backing, frames, lettering, and decorative shapes
- Furniture: Bending processes create legs, supports, frames and shelving for metal furniture
Industries that use sheet metal bending
Sheet metal bending is an essential process in the manufacturing of many products. It is a versatile process that can be used in a wide variety of industries, including automotive, aerospace, electronics, and appliances.
Here are some examples of products that are made using sheet metal bending:
- Car bodies
- Aircraft components
- Electronic devices
- Appliances
- Furniture
- Medical devices
- Construction materials
Advantages and disadvantages of sheet metal bending
It has several advantages, such as speed, accuracy, repeatability, cost, and versatility. However, it is important to be aware of the disadvantages of sheet metal bending, such as its noise, dust, and safety concerns. Let’s see both sides of the story.
Advantages of sheet metal bending
Speed and efficiency: It is a fast and efficient process. It can be used to create many parts in a short amount of time.
Accuracy: It is an accurate process. Modern CNC (COMPUTER NUMERICAL CONTROL) press brakes with precision tooling provide close bend tolerances.
Repeatability: It is a very repeatable process. Advanced automation with robots, manipulators, and CAD/CAM programming enables lights-out bending. It can be used to create identical parts repeatedly.
Cost: Bending is an economical, high-speed process suitable for mass production fabrication. It is a cost-effective way to create high-quality parts.
Versatility: Can be used to create a wide variety of shapes in sheet metal. It is a very versatile process that can be used to create parts for a wide range of industries.
High strength: Bending sheet metal produces parts with excellent strength-to-weight ratios capable of supporting large loads.
Shape flexibility: A wide range of profiles can be bent from sheet metal using different punches and die sets.
Minimal secondary processing: Bent parts require little additional finishing or surface treatment in most cases.
Material options: Can bend steels, stainless, aluminum, copper alloys, and other ductile metal sheets.
Disadvantages of sheet metal punching
Noise: Can be a very noisy process. This can be a problem if the bending is being done in a noisy environment.
Dust and metal shavings: Can create a lot of dust and metal shavings. This can be a problem if the bending is not done in a well-ventilated area.
Safety: Can be a dangerous process if not done properly. It is important to follow safety guidelines when operating sheet metal bending equipment.
Limitations: Bound by press bed size and material thickness capabilities.
Grain orientation: Bending against the sheet metal grain risks cracking and requires pressure adjustments.
Spring back: The material’s elasticity causes some shape deviation that must be compensated for.
Bend sequencing: The order of bends affects the final shape and must be carefully programmed.
Operator skill: Experience needed to produce quality parts and properly adjust processes.
Three types of sheet metal bending
The type of sheet metal bending that is used depends on the desired outcome and the type of sheet metal being used. There are three main types of sheet metal bending:
Air bending: This is the most common type of sheet metal bending because it is fast and easy to do. It is a process that uses a punch and die to bend sheet metal. The punch is a tool pressed into the sheet metal, while the die supports the sheet metal during the bending process. The bend is created by the punch pressing into the sheet metal and forcing it to bend.
These are the steps:
- The punch presses the sheet metal down over a die opening but does not fully form the metal to the die shape
- A small gap remains between the bent flange and the die at the bend point after the punch retreats
- Air bending does not require bottoming of the punch and is easier than coin or bottom bending
Bottoming: This is a type of sheet metal bending that uses a punch and die to force the sheet metal into a V-shaped groove. This creates a sharp and accurate bend in the sheet metal. It is often used for bending sheet metal for ducting, piping, and other applications.
These are the steps:
- The punch fully presses the metal into the mating die cavity, fully closing the flange shape
- These cold forms the material around the exact die profile
- It requires greater force and precision to avoid cracking
Roll bending: This is used to create cylindrical shapes from sheet metal. Roll bending is a type of sheet metal bending that uses three rollers to bend sheet metal into a cylindrical shape. The rollers are arranged in a pyramid configuration, and the sheet metal is passed through them. The rollers rotate in the same direction and at different speeds, which causes the sheet metal to bend into a cylindrical shape.
These are the steps:
- The punch and die close to an intermediate position, then the punch moves laterally to bend the metal to the final profile against the die radius
- No press force is applied when in the final bend position
- Produces accurate bends while reducing cracking risks
The process for sheet metal bending
The process for sheet metal bending can vary depending on the type of bending being performed and the equipment being used. However, the general process is as follows:
- Design: All bend locations, angles, radio, and dimensions are specified in the engineering drawings
- Programming: The bending sequence is programmed, including tool selection, depth, allowances, pressure, etc. based on the material, thickness, and features
- Setup: The required punch and die sets are installed in the press brake per the programming. Proper lubrication and alignments are set
- Load: The flat sheet metal stock is loaded and aligned to the backstops on the press bed. Hold downs clamp it firmly
- First bend: The press brake makes the first programmed bend according to the sequencing
- Reposition: The operator or manipulator repositions the sheet for the next bend in the sequence
- Remaining bends: The press brake progresses through all the remaining bending operations per part programming
- Unload: The finished bent part is unloaded from the press brake for inspection while a new sheet is loaded
- Inspection: Dimensions, angles, tolerances, and surface defects are checked to ensure the parts meet specifications
- Hardware: Any required holes or cutouts are made in secondary operations before hardware installation.
A word of caution: Make sure that the sheet metal is properly secured before bending. Be careful not to over-bend the sheet metal, as this can cause it to tear. Be aware of the location of all moving parts of the bending machine.
In the following video you will be able to watch a sheet bending machine in action.
Equipment used for sheet metal bending
The appropriate machinery, tooling sets, material handling, and safeguarding is crucial for cost-effective sheet metal bending production. The primary equipment used for sheet metal bending includes:
Press brake: The main machinery that provides the force and precision movement to bend the sheet metal. Can be hydraulic, mechanical, pneumatic, or servo electric.
Punch and die sets: The punch and die match the desired bend shape and radius. Multiple sets used for complex parts.
Tool holders: Securely hold the punch and die in the press brake during operation. Allow quick changeovers.
Back gauges: Locators that consistently position sheet blanks for the programmed bend sequence.
Clamping: Clamps like vise clamps or toggle clamps hold the sheet metal securely during bending.
Manipulators: Automated arms that reposition parts between bending operations increase automation.
Safety guarding: Physical barriers around the press brake safeguard the operator.
Deburring tools: Files, abrasive wheels, and deburring machines remove sharp edges after bending.
CAD/CAM programming: Computer programming optimizes bend sequencing and calculates required tonnage.
Rolls: Rotary rolls pre-bend sheet metal prior to final press brake forming when needed.
Cranes: Bridge cranes or jib cranes for lifting heavy dies, tooling, and materials in and out of the press brake.
Safety guidelines for sheet metal bending
Strict adherence to press brake safety is crucial for avoiding serious operator injury due to the extreme force and pinch points involved. Here are some key safety guidelines for sheet metal bending operations:
Machine guarding: Enclose or barricade pinch points around the press brake dies to prevent accidental hand contact.
Safety blocks: Insert safety blocks between die openings during setup, tool changes, and inspections.
E-stop buttons: Ensure sufficient emergency stop buttons are accessible to immediately halt the press brake action.
Lockout/tagout: Strictly follow lockout/tagout procedures when servicing press brakes or handling any tools or dies.
Bending aids: Use bending aids like support tables, lifts, and vacuum cups to secure parts for safe handling.
Crane safety: Follow all crane operation guidelines when handling large dies or materials to and from the press brake.
Die handling: Use proper lifting techniques and wear steel toe boots when handling heavy dies.
Clamping: Do not exceed rated tonnage and use adequate clamping pressure to securely hold material without slippage.
Gloves prohibited: Never wear gloves due to grab and pinch hazards.
Operator training: Provide extensive operator training on press brake safety, operational procedures, and proper bodily positioning.
OSHA compliance: Adhere to OSHA regulation 1910.212 and ANSI B11 standards for press brakes.
Signage: Post-approval warning signs, safe operating procedures, and emergency contacts at the station.
Sheet metal bending: Last thoughts
Sheet metal bending is an essential process in the manufacturing of many products. It is a versatile and efficient process that can be used to create a wide variety of shapes in sheet metal.
For decades we have been helping companies to set up sheet metal punching operations. Feel free to reach out to us at your earliest convenience to get started.
