Why Sheet Metal?
Sheet metal can be used for a wide variety of applications. Sheet metal can be extremely advantageous depending on the type of application. Sheet metal has a much lower material cost than machining does. Instead of beginning with a chunk of material and having the majority of that cut away by a machine, sheet metal enables a person to purchase and use only the amount needed. Also, the leftovers of sheet metal can be used again, compared to swarf (the shavings the machining creates) which needs to be discarded. This greatly reduces waste, saving a person or company money.
In this day and age, sheet metal manufacturing can be automated, and segments created right from computer-aided design (CAD) models. CAD models use lots of different materials and a wide variety of processes to form completed apparatuses and products. Since mass production is crucial to a competitive edge, sheet metal fabrication is extremely scalable. Even though getting started can be expensive, the cost per segment decreases rapidly as volume increases. This is true for a lot of different processes. However, price per segment for sheet metal typically goes down sharply, compared to a subtractive process such as machining.
How is Sheet Metal Being Used?
Sheet metal can be:
- Punched
- Bent
- Welded
- Tapped
- Drilled
- Cut
- Riveted
- Sheared
- Machined
- Rolled
Hardware can go into sheet metal components and those components can be:
- Anodized (converts a metal surface into a decorative, durable, and corrosion-resistant finish)</li
- Brushed
- Plated
- Silk screwed
- Marked
- Powder-coated
- Spray painted
Finally, parts can be screwed, riveted, or welded into multifaceted assemblies.
Just like the continuous evolution of technology today, sheet metal is changing and adapting to current needs and trends. Leveraging the right supplier and technique for manufacturing parts is essential in order to gain all the benefits from using sheet metal.
The key components of sheet metal production described in this paper are:
- The materials
- Manufacturing styles
- Design considerations
- Finishing preferences
Sheet Metal Fabrication Techniques
Sheet metal starts out flat but can be molded in a variety of ways to meet a variety of demands. The focus of this guide is on technologies that mold sheet metal by bending it along one axis. However, there are a range of techniques that can be used to mold the material into multi-axis shapes that are not made up of flat planes or bent along one axis. Some of these techniques include hot and cold forming of deep drawing, stamping, spinning, and hydroforming. The techniques listed above are the type of process that forms the body of panels for vehicles today, multifaceted shaped objects like metal sinks, and aluminum cans. A lot of the time these techniques are repetitive, forming the metal by repeating the process multiple times to alter the form of the metal in small stages.
Cold forming processes:
Cutting
- Shearing. This was the original way to cut sheet steel but is outdated and has been replaced by quicker, more accurate ways.
- Punch press. This can be used to punch and die sets into cut metal. This is useful for cutting simpler segments, compared to a laser or water jet. A punch press operates at hundreds of stokes per minute and can make appropriate parts rapidly. Punching can be used to create holes or other cutouts in parts. Through combining punch and laser cutting a person can create a multifaceted flat pattern with size-limited stamped features.
- CNC laser cutting. This uses spurts of oxygen, nitrogen, carbon dioxide, or helium to burn away metal and creates an extremely precise, finished edge. The thickness of the metal will affect the speed of the overall process. Since there is no contact with any metal, the apparatus does not wear out in the same manner as a mechanical cutter would.Two types of lasers are typically used in sheet metal fabrication:
- Fiber-optic lasers: Used for thinner and more reflective material to deliver exact cuts.
- Multi-gas or carbon dioxide lasers: Used for thicker gauges and are more powerful.
- Photochemical machining. This is a process of controlled engraving using CAD produced cutouts to leave a design that is chemically triggered to eliminate unnecessary metal.
Bending. The majority of metals are able to be bent along a straight axis through the use of an assortment of processes. The forms of the bends can vary from mild curves to sharp corners at angels over, under, or exactly at 90 degrees. In order to create those sharp bends, press brakes are used. Rolling and forming approaches create open or closed single-axis curves in an unceasing bending operation.
Hemming. This encompasses rolling the edge of a metal shape in order to deliver a slicker, tougher edge. Hems are able to be opened, which creates an air space within the bend. They can also be closed, which is when the folded metal is right up against itself. Curling creates a barrel hem (a round edge to a piece of metal). A barrel hem can be used to get rid of sharp edges or as a specific operational function like a door hinge where it holds the pin allowing the hinge to swivel.
A Brief History of Sheet Metal
Starting way back in the ancient Egyptian times, sheet metal was first reportedly used to create stunning gold and silver jewelry. Fast forward from there and it was used to create medieval armor. Once the Industrial Revolution started, the use of sheet metal began to become more prevalent. Today, sheet metal can be found in so many different things. From the appliances found right in the comfort of one’s home to the satellites floating thousands of miles above.
The industrialization of sheet metal manufacturing started in 1682 with the first cold rolling mill appearing in England. The Industrial Revolution that started in 1760 led to the creation of assembly-line production, hydraulic press, and press brakes. From there, in 1856, the Bessemer converter was created to mass-produce steel. Even today, advancements in sheet metal production have been growing at an explosive rate. The sheet metal industry is currently worth over 25 billion dollars.
What Types of Sheet Metal Are There?
A variety of metal and metal alloys can be molded into sheets and used to construct sheet metal pieces. Determining what materials to use depends largely on two things. The first, is the requirements of the application. The second, is factors in selecting materials such as corrosion resistance, cost, formability, strength, weight, and weldability.
Popular Sheet Metal Materials:
- Stainless Steel. There are two popular types of stainless steel that are used in sheet metal fabrication:1. Standard stainless. This is the most frequently used version of stainless and can be non-magnetic (any 300 series steels). Unlike some metals, standard stainless does not need hot work or other stress relief while being manufactured.
- Grade 304 is the most widely used standard stainless is because it provides good formability and weldability even though it is a little less corrosion-resistant than Grade 316.
- Grade 316 is the most corrosion-resistant out of all the stainless-steel grades and can even maintain strength at extreme temperatures.
Standard type magnetic stainless. These fall under standard stainless and are known as the 400 series.
- Grade 410 is less corrosion resistant but is heat treatable.
- Grade 430 is cheap compared to other stainless-steel options and is used in applications where corrosion resistance is not a constraint like in brush-finished appliance surfaces. The material typically experiences elastic deformation, so they need to be over bent to obtain their finished form.
2. Spring-like steels. These steels are Grades 17-4, 301, and 1075. They are characterized by how they work-harden rapidly and their need to be heated to reduce stress when being molded. They need special equipment, processes, and must be considerably bent in order to obtain their finished shape.
- Cold rolled steel (CRS). This form of sheet metal material comes in 1008 and 1018 alloys. This type of sheet metal material goes through the process of cold rolling steel in order to smooth the finish of hot rolled steel and holds a tighter tolerance when molding.
- C1008 is intended for exposed or unexposed parts involving bending, moderate drawing or forming, welding, and should be painted to avoid rust.
- C1018 is better for carburized parts and is versatile.
- Pre-plates steel. This form of sheet metal material can be both hot-dip galvanized or galvanized steel (galvanized and then annealed).
- Aluminum. This form of sheet metal material has a wide variety of features across multiple grades allowing it to meet application needs.
- Grade 1100 is of low strength however, it is weather and chemical resistant, ductile, and weldable, permitting deep drawing.
- Grade 3003 is tougher, weldable, corrosion-resistant, formable, and reasonably priced.
- Grade 5052 is much stronger but weldable, formable, and corrosion-resistant.
- Grade 6061 is a structural alloy. This is strong and corrosion resistant, however, it’s not formable. This can be welded, but it losses some strength when welded.
- Copper/Brass. People generally pick either C110 or C101, electrolytically tough pitch (ETP) copper, when they want a “red” metal. Less commonly, designers and engineers pick cartridge brass as an alternate.
- C101 has a nominal conductivity of 100 percent International Annealed Cooper Standard and high thermal conductivity.
- C110 is the purest grade of oxygen-free copper, has much tighter limits on impurities than other grades, as well as offers the highest electrical and thermal conductivity values available.