What is Sheet Metal Forming?
Sheet metal forming, also known as sheet metalworking, is a manufacturing process that involves multiple processes applied onto thin metal sheets, strips, and coils, shaping them into intricate and complex forms. Through a wide range of methods, this transformation relies on the application of precise force without adding or removing the material while keeping its mass solid and unaltered.
Commonly performed on presses at room temperature, sheet-forming operations are also described as pressworking or sheet metal press forming within the industry. Other notable features of sheet metal forming include the involvement of costly, heavy, and large types of machinery to withstand high loads of stress applied during the processes.
What Materials and Applications Are Suitable for Sheet Metal Forming?
The choice of materials plays a pivotal role, with low-carbon steel emerging as a cost-effective option, offering commendable strength and formability. Aluminum takes the lead in applications requiring corrosion resistance, such as beverage cans, packaging, and cookware. Another commonly used material for sheet metal forming is copper.
The sheet metal applications don’t just stop here. The applications can also include consumer and industrial uses. Common applications include automobiles, electronic parts, washing machines, airplane wings, household items such as gas cylinders, desks, file cabinets, and beverage cans, as well as construction uses like building roofs.
Common Sheet Metal Forming Processes
Sheet metal forming processes are typically classified based on variations in effective stresses. The basic processes include: bending, deep drawing, and shearing. However, many other types of common forming methods can still be applied to sheet metal, such as rolling, stretching, curling, hemming, laser cutting, etc. Let’s take a closer look to learn about these processes.
Bending
Bending is a metal shaping process where force is applied to sheet metal, making it bend and take a desired form or shape. The bending equipment is often a machine called a press brake, which can be operated manually or automatically. Press brakes come in various sizes to suit different applications. Most commonly, press brakes often use V-bending, where the punch and die have a "V" shape as the picture below shows. The punch pushes the sheet into the V-die groove, causing the bend.
In the bending process, the sheet metal is placed over a die and held in position by a back gauge. The punch then descends, causing the sheet to bend with the wanted angle and form. Automatic machines use a hydraulic metal brake to power the punch into the sheet metal. The depth to which the punch forces the sheet into the die determines the bend angle, and this depth is precisely controlled.
Deep Drawing
Deep drawing, or simply “drawing”, is a metal forming process that involves transforming a flat sheet metal blank into a hollow, cup-shaped, three-dimensional component through a series of drawing and stretching operations. This is achieved by placing the sheet metal blank over a die and then using a hydraulic punch, often made of strong steel, to draw the material into the cavity, creating the desired shape. This process can happen in several steps, each one stretching the metal a bit more to increase depth before achieving the final shape.
While various shapes are possible to be made from this process, it is particularly suitable for producing cylindrical or box-shaped parts with depth. Drawing is most efficient when applied to ductile metals like aluminum, copper, and mild steel. Common applications include sinks, fuel tanks, automotive parts, all types of containers and cookware, beverage cans, ammunition shells, and so on.
Shearing
Shearing, which includes punching and blanking, is a sheet metal forming process involving the cutting or removal of material from a metal sheet along a straight line between two cutting edges using a power shear.
In punching, a hole or various shapes are created by using a punch and die, while blanking involves cutting out a piece of material to form a desired shape. Both processes use a punch and die set, where the punch creates the cut or hole, and the die provides support for the material being cut.
Shearing is widely employed in manufacturing various components, such as metal plates, sheets, and intricate shapes used in diverse applications ranging from automotive to electronics. This method boasts high efficiency, precision, and cost-effectiveness.
Rolling
Rolling, or rollforming, is a metal forming process where a metal sheet or plate is passed through a line with roll stations to reduce its thickness or change its cross-sectional area. Every station is equipped with a pair of rollers, known as a roller die, set on both sides of the sheet. The roller dies may have unique shapes and sizes, or several identical roller dies may be utilized at different positions on a single line. As the metal passes through a series of rollers, the rollers exert compressive force on the metal, causing it to deform and elongate. The process is commonly used to produce sheets or plates with a consistent thickness, shape, and surface finish, including panels, tracks, shelving, etc.
The benefits of rolling include precise thickness control, improved surface finish, and the ability to work with a wide range of metals, making it a widely used method in the sheet metal forming process.
Stretching
Performed on a stretch press, the sheet is firmly held at its edges by jaws connected to carriages in the stretching process. The essential tool, a stretch form die, is a solid piece pressed against the sheet metal. Typically, the form die sits on a press table lifted into the sheet by a hydraulic ram. As the die enters the tightly gripped sheet, increasing tensile forces cause plastic deformation, reshaping the sheet.
However, stretching a metal sheet has its limits before reaching the breaking point, known as the ultimate tensile strength (UTS). Beyond this, the material fractures and fails. Manufacturers must grasp the science behind sheet metal stretching to effectively control and optimize the process.
This forming method is known for its precision and ability to craft smooth surfaces. Common materials used with the stretching forming technique include aluminum, steel, and titanium, with applications ranging from car door panels, and aircraft wing panels to window frames.
Curling
Curling involves the controlled bending of a metal edge into a cylindrical or curved shape, resulting in a hollow roll to the edge of the workpiece. This process is commonly employed to create rounded edges or intricate contours on sheet metal components, allowing for the creation of aesthetically pleasing and functionally effective, flexible designs. Rounded edges created through curling also contribute to safety by smoothing out sharp, rugged corners and removing burrs.
Hemming
Hemming involves folding and securing the metal sheet's edge onto itself, creating an area with double layers. This meticulous process goes beyond enhancing structural integrity and durability; it's a vital step in ensuring safety and aesthetics in various applications, especially within the automotive industry. The initial stage utilizes acute tooling for a robust bend, followed by a precise flattening process using a specific die. This not only fortifies the sheet but also conceals sharp edges, reducing injury risks and contributing to the polished appearance of the final product.
Hemming also comes with several different forms and types, as the picture suggests below.
Ironing
The ironing technique involves the thinning of a metal sheet through a controlled reduction in thickness, often achieved by punching the material between two constricted dies with force. Its prominent application is in shaping material for aluminum cans, where maintaining uniformity is a crucial requirement. This process ensures that the metal sheet, often too thick in its raw state, attains the desired thinness on walls without losing the whole structural integrity and changing the thickness of the bottom. The technique earned its name due to its resemblance to the process of ironing clothes.
Laser Cutting
Laser cutting is a highly precise and versatile method used to cut through various materials with the aid of a concentrated laser beam. It utilizes the power of light amplification by stimulated emission of radiation (LASER) to vaporize or melt materials when exposed to the laser beam. It has become a very common forming process for sheet metal recently.
One of the defining features of laser cutting is its ability to achieve intricate and precise cuts, making it ideal for creating complex shapes and designs. Additionally, laser cutting is known for its speed and efficiency, allowing for rapid production of parts with minimal material waste. Moreover, laser cutting offers versatility in terms of the materials it can cut, including metals, plastics, wood, and more. Its non-contact cutting method also minimizes material distortion, leading to high-quality finished products.
Tong Lay Doo offers top-notch laser cutting services for metal. Check out Sheet Metal Prototyping Service for more information.
Advantages of Sheet Metal Forming
Let’s take a look at some of the reasons why sheet metal forming works.
Versatile Shapes and Applications Available: Allows for the formation of diverse shapes while preserving structural integrity, providing significant flexibility for designs and applications, such as automobile parts, electronic components, and aircraft parts to everyday products like beverage cans and gas cylinders.
Wide Range of Materials: Sheet metal forming accommodates an extensive variety of materials, from stainless steel to aluminum and copper, enhancing its applicability across diverse projects.
Strength and Durability: Sheet metal boasts inherent strength and durability, ensuring the creation of robust and enduring components.
Cost-Effective Solution: Compared to processes like forging, casting, and extrusion, sheet metal forming offers a more economical solution without compromising on quality. The overall costs vary based on part design, material selection, and the number of processing steps required for production.
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