Sheet Metal Fabrication: What It Is, How It Works, and Why It Matters
What Exactly Is Sheet Metal?
Sheet metal is flat metal that has gone through a process to reduce its thickness to a manageable size for fabricating. Depending on the material used and how you plan on using it, thicknesses can range anywhere from being less than a millimeter all the way up to several centimeters. Commonly used materials include aluminum, steel, copper, brass and stainless steel.
Sheet metal fabrication is one of the earliest practices in making products, and it continues to be used by a large number of companies today. In addition to being very common in manufacturing, you will also find it in use in hospitals, kitchens, etc., as sheet metal items are used for making enclosures, brackets, ducts, panels, frames, etc.
Why is this practice so popular?
Because it is an inexpensive way of making products out of metal; it can be produced quickly and easily; finally; there are many possible finishing options (e.g., painting, powder coating, anodizing).
The fabrication process is the combination of several different operations to create a finished part or assembly from flat metal sheets through cutting, forming and assembling together.
Laser Cutting
Laser cutting is a method of cutting sheet metal using a high-precision focussed beam of light to create its edge. It also works great on creating very detailed parts or intricate designs because it is like a precision tool, and it can cut almost any type of metal easily. For mass-produced components or parts that need to meet specific tolerances, laser cutting is typically used as part of the secondary manufacturing process.
Modern fiber lasers can quickly process both stainless steel and aluminum, resulting in short lead times and reasonable costs.
CNC Bending
When a part has been cut, the next step is frequently bending that part into the desired shape. CNC bending machines or Press Brakes use an exact amount of force to bend items in a straight line resulting in precise angles and channels.
The CNC part applies to machines that operate according to a pre-programmed set of instructions. All machines are capable of bending the same piece repeatedly, producing identical finished products (all parts will fit together as if they were made to fit together).
Stamping
Metal sheets can be stamped by using a die and a press which punches and/or forms shapes with speed, smoothness and consistency; this method is suitable for the mass production of items - examples include electrical connectors, automotive body panels and components of appliances that have been stamped.
The cost of tooling (dies) can be considerable; however, if you are producing many parts at once, the cost of the die per part reduces significantly.
Welding
Once all of the individual parts have been cut and bent, they will be welded together to make one piece. The most typical forms of joining metal are MIG, TIG, and spot welding.
To create a good weld one must have both skill and the right preparation. A poorly welded part may experience stresses that can ultimately lead to its failure when subjected to a load. As a result, the preparation of the metal will often be the most important factor affecting the longevity of a finished assembly.
Metal Spinning
Spinning is an uncommon but important process that involves spinning a thin disc of metal at a high rate of spin to produce round or symmetrical shapes (e.g., cones, domes, or cylinders) by using a tool to apply pressure through a forming die. Examples of parts produced using this method include lighting fixtures, aerospace components, and ornamental metal items.
Materials Used for Sheet Metal Fabrication
The choice of material impacts everything from weight and durability to corrosion resistance and pricing.
1. Mild Steel is cheap and easy to weld and is traditionally used for structural and other enclosures.
2. Stainless Steel can withstand corrosion therefore is generally used within industries handling food, medical and marine environments.
3. Aluminum is light weight and naturally corrosion resistant. The aviation, automotive and electronics industries use it extensively.
Copper and brass are ideal for electrical components and application where aesthetics are considered. Usually, thickness is defined in terms of gauge (in the U.S.) or in millimeters. Thicker material will provide a stronger component; however, it will not bend as easily without breaking.
Importance of understanding where sheet metal manufacturing fits — relative to other manufacturing processes — is crucial when deciding which manufacturing process to use for your project. Sheet Metal vs. Metal Casting
Metal casting is the process of pouring molten metals into molds to form a specific shape. This process allows the production of complex parts in three dimensions that would otherwise be very difficult or even impossible to produce from flat sheet materials. There are many types of metal casting methods including sand casting, die casting and precision casting. Sheet metal is used in a wide variety of applications starting from flat sheets that are cut and formed into a desired shape through bending and cutting operations. Flat sheets of metal lend themselves to producing thin walled parts, enclosures, and structural frames. The materials produced using the metal casting process tend to have thicker, solid cross-sectional geometries than products made using sheet metal.
Metal casting is probably the best option for manufacturing a part with interior cavities, thick walls or organic curves. If that part is a bracket, panel, or housing then sheet metal is typically a faster, less expensive method than CNC machining.
Process comparison: Sheet Metal vs. CNC Machining
CNC machining creates a particular part by subtracting material from a previously solid piece of material via rotary- and linear-motion cutting tools (turning, milling, drilling and tapping). It can produce products with extremely high accuracy requirements and very tightly controlled tolerances — making it excellent for precision engineering mechanical components. Sheet metal is better suited to the production of large quantities of thin parts. CNC Machining is better suited to the production of heavy, complicated, and high dimensional accuracy solid products. Many products incorporate both types of manufacturing processes, such as having a machined shaft inside a sheet metal housing.
Sheet Metal vs. 3D Printing
3D printing produces parts through layering until the final part is produced. It's great for making prototypes, creating complex shapes and building custom items in small quantities. 3D Metal Printing (using metal materials such as titanium alloy, aluminum alloy, or stainless steel) can also manufacture parts that cannot be produced using any other manufacturing method.
On the other hand, the cost and time required to produce a part using conventional techniques like sheet metal manufacturing are generally much less than for 3D printed components. There is still room for both technologies, as some productions have a mix of prototype (3D printed) and production (sheet metal) items.
Common Applications Across Industries
Sheet metal shows up in more places than most people realize.
HVAC ducts, roofing panels and structural supports are all fabricated using sheet metal within the construction industry. Door panels, chassis components and fuel system parts can all be manufactured out of sheet metal by companies involved with the automotive sector. The electronics industry relies on sheet metal for enclosures, chassis and server racks to protect electronic equipment. Medical device manufacturers rely on stainless steel sheet metal for housing of equipment and surgical tool trays. Aerospace suppliers will use aluminum sheet metal to manufacture airframe sections, access panels, and brackets.
This explains the large volume of sheet metal fabrication, as it is one of the leading manufacturing segments in the world today.
The following are some of the factors that determine the quality of fabricated sheet metal. What makes one fabricated metal part a good one? There are several things that separate high quality fabrication from lower quality fabrication and ultimately cause problems later in the production process.
Material certification - suppliers must provide documentation of their metal materials that document their grade and chemical composition. Consistency of tolerances - dimensional accuracy is important when looking for parts that will be used in an assembly; therefore, you should also determine if your supplier has access to coordinate measuring machines (CMM) or other means to inspect their materials.
A Practical Note for Buyers
If you're sourcing sheet metal parts for an OEM project, a few questions will help you get better results faster.
If you need a tolerance of ±0.1mm, make sure to communicate that clearly to the supplier that they have to comply. Always provide material certifications (if required for your particular industry). Encouraging the supplier to manage their processes under one roof will create fewer logistical headaches for you if your project requires multiple processes (i.e., sheet metal housings and CNC machined inserts).
Sheet metal fabrication has been around for a long time, so it is very well-established and continues to form the backbone of modern manufacturing. Furthermore, while it may not necessarily make someone say "wow," sheet metal fabrication does; in fact, function successfully within all types of industries and applications. To Summarise: Sheet Metal Fabrication Is A Mature Manufacturing Process And Will Continue To Be Used For Many Years To Come.
Having a solid understanding of the core processes associated with sheet metal and how it relates to other manufacturing methods and materials can help you make better sourcing decisions. Visit the Fabricators & Manufacturers Association (FMA) website if you want to learn more about sheet metal processes, standards, tolerances, tooling, and materials.
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