Principles
Forming processes convert solidified steel into products useful for the fabricating and construction industries. The objectives are to obtain a desired shape, to improve cast steel’s physical properties (which are not suitable for most applications), and to produce a surface suitable for a specific use. During plastic forming, the large crystals in cast steel are converted into many small, long crystals, transforming the usually brittle cast into a ductile and tough steel. In order to accomplish this, it is often necessary to reduce the cross section of a cast structure to one-eighth or even less of its original.
The major forming processes are carried out hot, at about 1,200° C (2,200° F), because of steel’s low resistance to plastic deformation at this temperature. This requires the use of reheating furnaces of different designs. Cold forming is often applied as a secondary process for making special steel products such as sheet or wire.
There are a number of steel-forming processes—including forging, pressing, piercing, drawing, and extruding—but by far the most important one is rolling. In this process, the rolls, working always in pairs, are driven in opposite directions with the same peripheral velocity and are held at a specific distance from each other by heavy bearings and mill housings. The steel workpiece is pulled by friction into the roll gap, which is smaller than the cross section of the workpiece, so that both rolls exert a pressure and continuously form the piece until it leaves the roll gap with a smaller section and increased length. As shown in the figure, the reduction in cross section is calculated by subtracting the out-section (S2) from the in-section (S1) and then dividing by S1. Assuming the workpiece maintains its original volume as it is formed, the elongation (L2) divided by the original length (L1) equals S1 divided by S2. When rolling flat products, there is not much change in width, so that the thickness alone can be used to calculate reduction.
The basic principles of a rolling-mill design are shown in B in the figure. Two heavy bearings mounted on each side of a roll sit in chocks, which slide in a mill housing for adjusting the roll gap with a screw. The two housings are connected to each other and to the foundation, and the complete assembly is called a roll stand. There are also compact rolling units (C in the figure), which do not have housings; often used in the tandem rolling of long products, they can be exchanged quickly for repair or for a change in the rolling program. Rolls are driven through spindles and couplings, either directly or via a gear, by one or several electric motors. Depending on the product rolled, there are stands that have two, three, four, and more rolls; accordingly, they are given the names two-high, three-high, four-high, six-high, cluster mill, and planetary mill (schematically shown in the figure). For rolling strip, heavy backup rolls support the smaller work rolls, because thin rolls form flat material better than do large-diameter rolls.
In a rolling shop, stands are arranged according to three layout principles. One is called the open train (G in the figure), in which the stands are arranged side by side, often driven by the same motor and linked by spindles. This arrangement is applied only to the rolling of long products, with guides or cross-transfers being used to move the workpiece from stand to stand. A tandem mill arrangement (H in the figure) has one stand behind the other and is used for high-production rolling of almost all products. This continuous arrangement requires the construction of long rolling trains and buildings, but layouts can be shortened by a so-called semicontinuous mill, in which the workpiece is passed back and forth through a reversing mill before being sent through the rest of the line. When open-train and tandem arrangements are combined for rolling long products in more compact layouts, it is called a cross-country mill.
Metal forming processes play a crucial role in powering our society, driving innovation across industries. They enable the creation of a wide range of products and components, from heavy machinery and infrastructure to cutting-edge technologies like microprocessors and artificial intelligence.
But have you ever wondered how metal is shaped? In metal manufacturing, there are multiple processes to choose from. Each process holds its own set of advantages and disadvantages, making them suitable for specific applications and different types of metal.
Some of the most common types of metal forming techniques are:
- Roll forming
- Extrusion
- Press braking
- Stamping
- Forging
- Casting
Explore the diverse world of metal manufacturing processes and discover the optimal techniques for shaping metal to meet your unique needs.
1. Roll Forming
In short, roll forming involves continually feeding a long strip of metal through drum rollers to attain the desired cross-section. This process is highly efficient and cost-effective, making it the preferred choice for producing long lengths of sheet metal with consistent profiles. Additionally, roll forming can handle various metals such as steel, aluminum, copper, and more.
Roll forming services:
- Allow for advanced inline addition of punched features and embossing
- Are best suited for large volumes
- Yield complex profiles with intricate bending
- Have tight, repeatable tolerances
- Have flexible dimensions
- Create pieces that can be cut to any length
- Require little tool maintenance
- Are capable of forming high-strength metals
- Permit ownership of tooling hardware
- Reduce room for error
- Create less scrap
Common Industries & Applications of Roll Forming
Industries
Aerospace
Appliance
Automotive
Construction
Energy
Fenestration
HVAC
Metal Building Products
Solar
Tube & Pipe
Common Applications
- Construction Equipment
- Door Components
- Elevators
- Framing
- HVAC
- Ladders
- Mounts
- Railings
- Ships
- Structural Components
- Tracks
- Trains
- Tubing
- Windows
2. Extrusion
Extrusion is a metal manufacturing process that forces metal through the die of the desired cross-section. It creates complex cross-sections and hollow parts with uniform wall thicknesses. Extrusion is a favored process for producing long lengths of metal with intricate cross-sectional profiles, and it's also highly efficient.
If you're thinking of pursuing extrusion metal forming, you should keep in mind that:
- Aluminum is primarily the extrusion of choice, though most other metals can be used
- Dies (aluminum) are relatively affordable
- Punching or embossing is done as a secondary operation
- It can produce hollow shapes without seam welding
- It can produce complex cross-sections
Common Industries & Applications of Extrusion
Industries
- Agriculture
- Architecture
- Construction
- Consumer Goods Manufacturing
- Electronics Manufacturing
- Hospitality
- Industrial Lighting
- Military
- Restaurant or Food Service
- Shipping & Transportation
Common Applications
- Aluminum Cans
- Bars
- Cylinders
- Electrodes
- Fittings
- Frames
- Fuel Supply Lines
- Injection Tech
- Rails
- Rods
- Structural Components
- Tracks
- Tubing
3. Press Braking
Press braking involves common sheet metal forming (usually), bending the metal workpiece to a predetermined angle by pinching it between a punch and a die. Press brakes are commonly used to bend metal sheets into V or U shapes for architectural, automotive, and other purposes.
If you're interested in press braking, be aware that it:
- Works best for shorter, smaller runs
- Produces shorter parts
- Is best suited for compatible shapes with more simple bend patterns
- Has a high associated labor cost
- Produces less residual stress than roll forming
Common Industries & Applications of Press Breaking
Industries
- Architecture
- Construction
- Electronics Manufacturing
- Industrial Manufacturing
Common Applications
- Decorative or Functional Trim
- Electronics Enclosures
- Housings
- Safety Features
4. Stamping
Stamping involves placing a flat metal sheet (or coil) into a stamping press, where a tool and die apply pressure to form the metal into a new shape or cut out a piece of the metal. Stamping is ideal for producing high volumes of parts with consistent, intricate designs.
Stamping is associated with:
- Single-press stroke forming
- Consistent pieces with fixed dimensions
- Shorter parts
- Higher volumes
- Creating complex parts in a short amount of time
- Requiring high-tonnage presses
Common Industries & Applications of Stamping
Industries
- Appliances Manufacturing
- Construction
- Electrical Manufacturing
- Hardware Manufacturing
- Fastenings Manufacturing
Common Applications
- Aircraft Components
- Ammunitions
- Appliances
- Blanking
- Electronics
- Engines
- Gears
- Hardware
- Lawn Care
- Lighting
- Lock Hardware
- Power Tools
- Progressive Die Stamping
- Telecom Products
5. Forging
Forging involves shaping metals using localized, compressive forces after heating the metal to a point where it's malleable. This process yields strong, durable parts that are resistant to wear and tear.
If you're considering forging, keep in mind that:
- Precision forging combines production and manufacturing by forming the raw material into the desired shape, with the lowest possible amount of secondary operations needed
- It requires little to no subsequent fabrications
- It requires high tonnage presses
- It yields a stronger end product
- It results in a product with high strength and hardness
Common Industries & Applications of Forging
Industries
- Aerospace
- Automotive
- Medical
- Power Generation & Transmission
Applications
- Axle Beams
- Ball Joints
- Couplings
- Drill Bits
- Flanges
- Gears
- Hooks
- Kingpins
- Landing Gear
- Missiles
- Shafts
- Sockets
- Steering Arms
- Valves
6. Casting
Casting is a process that involves pouring liquid metal into a mold containing a hollow cavity of the desired shape. As the liquid cools and solidifies, it takes on the shape of the mold. Casting is ideal for complex shapes and designs with intricate details that would be difficult or expensive to produce through other metal forming processes.
Those considering utilizing a casting metal forming process should keep in mind that it:
- Can use a wide range of alloys & custom alloys
- Results in affordable short-run tooling
- Can result in products with high porosity
- Is best suited for smaller runs
- Can create complex parts
Common Industries & Applications of Casting
Industries
- Alternative Energy
- Agriculture
- Automotive
- Construction
- Culinary
- Defense & Military
- Health Care
- Mining
- Paper Manufacturing
Common Applications
- Appliances
- Artillery
- Art items
- Camera Bodies
- Casings, Covers
- Diffusers
- Heavy Equipment
- Motors
- Prototyping
- Tooling
- Valves
- Wheels
Choosing A Metal Forming Method
Are you looking for a metal former for your project? The type of metal manufacturing method you choose will depend on many factors:
- What metal are you using?
- What's your budget?
- What do you need to create?
- How will it be used?
By understanding the different metal manufacturing processes available and their applications, you can make informed decisions when choosing the most suitable technique for your specific project requirements.
Is Roll Forming Right for You?
If your metal shaping needs demand high volume, intricate profiles, and exceptional durability, roll forming is a powerful solution worth exploring. Its efficiency, precision, and flexibility can significantly enhance your production processes and deliver superior-quality products. With its ability to both optimize existing designs and unlock innovative possibilities, roll forming is a valuable tool for any manufacturer looking to stay ahead in today's competitive landscape.
Find out why so many industries choose roll forming and if the process fits your needs. Check out our free guide:
(Editor's Note: This article was originally published in January 2017 and was recently updated.)