In every household and working environment, metal plays a major role in how people operate. From appliances and light fixtures to desk tools, chairs, and utensils, metal is the stabilising element that makes all of today’s conveniences possible.
Metal fabrication is the process of turning raw metals into pre-made shapes for assembly use. For example, the panels that comprise the frame of an automobile are made through custom metal fabrication processes, which are usually performed at a fabrication facility and then sent to an auto assembly plant. However, the processes involved are complex and varied. The following sections explore and answer two simple questions: What is metal fabrication, and how does it work?
Metal fabrication is the creation of metal structures by cutting, bending and assembling processes. It is a value-added process involving the creation of machines, parts, and structures from various raw materials. Typically, a fabrication shop bids on a job, usually based on engineering drawings, and if awarded the contract, builds the product. Large fab shops employ a multitude of value-added processes, including welding, cutting, forming and machining. Metal fabrication usually starts with drawings with precise dimensions and specifications. Contractors, OEMs and VARs employ fabrication shops. Typical projects include loose parts, structural frames for buildings and heavy equipment, and stairs and hand railings. As with other manufacturing processes, both human labour and automation are commonly used. A fabricated product may be called a fabrication, and shops specialising in this type of work are called fab shops. The end products of other common types of metalworking, such as machining, metal stamping, forging, and casting, may be similar in shape and function. Still, those processes are not classified as fabrication.
Metal fabrication is a broad term referring to any process that cuts, shapes, or moulds metal material into a final product. Instead of an end product being assembled from ready-made components, fabrication creates an end product from raw or semi-finished materials. There are many different fabrication manufacturing process processes, and the process used depends on both the beginning metal material and the desired end product. Fabrication is used for both custom and stock products.
Most custom metal fabricated products are crafted from a range of commonly used metals and their alloys. Some of the most popular metal types available for custom metal fabrication include aluminium, brass, copper, gold, iron, nickel, silver, magnesium, tin, titanium, and various grades of steel. Fabricators often start with stock metal components, such as sheet metal, metal rods, metal billets, and metal bars to create a new product. For example, an aluminium billet may be fabricated into a curved aluminium tube by using the extrusion process and then folding the tube.
Specialised metal fabricators are called fab shops. Contractors, equipment manufacturers, and resellers have metal fabricators work on a variety of projects for them. Often metal fabricators bid on jobs by submitting drawings, and if they are awarded the contract, they build the project. Once a contract has been awarded, metal fabricators begin the planning stages. This involves ordering the correct materials and having a manufacturing engineer program CNC machines for the project. Some of the work may be sub-contracted out depending on the size and specialised needs of the project. Many metal fabricators specialise in specific processes or metals. Fab shops may use multiple fabrication processes to create a final product. They may also provide finishing services such as deburring, polishing, coating, and painting, to the product. Finishing differs from fabricating in that finishing is a secondary process to treat the exterior of the product, not to shape it or to create a new product.
This article gives an overview of some of the more common fabrication methods and considerations when choosing the right fabricator for a project.
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Metal Fabrication – Types of Fabrication
Choosing a fabrication method suited to a given project depends on part geometry, the product’s intended purpose, and the materials used in crafting it. Common custom metal fabrication processes are as follows:
Casting is when molten metal is poured a mould or die and allowed to cool and harden into the desired shape. The process is ideal for mass-production of parts with the reuse of the same mould to create identical products. There are several different types of casting. Die-casting is when liquid metal is forced into a die instead of a mould, and there the applied pressure keeps it in place until it hardens. This process is known for the high-speed applications it supports. Permanent mould casting involves pouring the molten metal into a mould.
There are a variety of types of casting processes. In some cases, a vacuum is also used in this process. Permanent mould casting can create stronger castings than die casting, but they can be difficult to remove from the final product. For this reason, semi-permanent mould castings are also available. These moulds have expendable cores, making them more manageable and less costly to remove. The final casting process is sand casting. With sand casting, castings are made by pressing a pattern into a fine mixture of sand. This forms a mould for the molten metal to be poured into. This process is slow but is generally more economical than the other forms of casting. It is also good to use when intricate designs are needed, or for large metal fabrication.
This very common type of fabrication is the cutting of a metal workpiece to split it into smaller sections. While sawing is the oldest method of cutting, modern methods include laser cutting, waterjet cutting, power scissors, and plasma arc cutting. There are many different methods of cutting, from manual and power tools to computer numerical computer (CNC) cutters. Cutting may be the first stage in a longer fabrication process or the only process used.
Die-cutting is another cutting process that uses a die to slice metal. Rotary die cutting uses a spinning cylindrical die to cut the material fed that is fed through a press. Flatbed die-cutting is used on thicker metal materials and uses a dies on a press to cut out shapes when the die stamps down on the metal.
Drawing uses tensile force to pull metal into and through a tapered die. The die stretches the metal into a thinner shape. Usually drawing is performed at room temperature, and is called cold drawing, but the metal workpiece can be heated to reduce the required force.
This process is considered deep drawing when the end product has a depth that is equal to or greater than its radius. It is usually used with sheet metal fabrication to turn sheets of metal into hollow cylindrical or box-shaped vessels.
In the extrusion process, the workpiece is forced through or around an open or closed die. When forced through an open or closed die, the diameter of the workpiece is reduced to the cross-section of the die. When pressed around a die, a cavity is formed within the workpiece. Both of these processes generally use a metal slug or cylinder (a billet) as the workpiece, and a ram to perform the impact operation. The resulting cylindrical item product is often wiring or piping. The die cross-section can have different shapes to produce differently shaped parts. Extrusion can be continuous to create very long pieces, or semi-continuous to create many shorter pieces.
Also called cold extrusion, impact extrusion is performed at room temperature and increases the strength of the part, making it stronger than the original material. When enough force is applied to the appropriate metal, it starts to flow into the available shape, much like the movement of viscous liquid. Cold extrusion is commonly used for steel fabrication.
Hot extrusion is performed at an increased temperature, to keep the metal from hardening and to make it easier to push through the die. It’s usually used for copper fabrication, as well to create custom aluminium parts.
Metal is manipulated to bend at an angle. The most common means is with a brake press that creates creases in the metal by pinching it. The workpiece is held between a punch and a die and forced to crease with pressure from the punch. This process is usually used to shape sheet metal. Folding can also be done by hammering the metal until it bends, or by using a folding machine, also known as a folder. The machine has a flat surface where the sheet metal is placed, a clamping bar the holds the workpiece in place, and a front panel that lifts upwards and forces the metal extended over it to bend.
Forging uses compressive force to shape metal. A hammer or die strikes the metal workpiece until the desired shape is formed. This process can be done with the metal at room temperature and is called cold forging. Forging can also be performed with the metal heated to a range of above room temperature to below the recrystallisation temperature and is then called warm forging. When the metal is heated to its recrystallisation temperature, which varies by metal, the process is called hot forging. Forging is one of the oldest types of fabrication, with blacksmiths using forging centuries ago.
Metal fabricators in Melbourne Metal fabrication company have a broad range of resources including both conventional and CNC machining, metal fabrication and sheet metal work.
Machining refers to the process of shaping metal by removing the unwanted material from it. This process can be performed in a variety of ways. There are many different machining processes, including drilling, turning, and milling.
Drilling uses a rotary cutting tool, the drill bit, to cut a hole in the material. The drill bit presses against the metal while being rotated very quickly to create a circular hole.
Turning uses a lathe to rotate the metal while a cutting tool moves in a linear motion to remove metal along the diameter, creating a cylindrical shape. The cutting tool can be angled differently to create different shapes. It can be done manually or with a CNC turning machine. CNC machining is generally used when part measurements must be extremely precise.
Milling uses rotating multipoint cutting tools to progressively remove material from the workpiece until the desired shape is achieved. The metal is slowly fed into the rotating cutting tool, or the tool is moved across the stationary metal, or both the workpiece and the tool are moved to each other. This process can be done manually or with a CNC milling machine. Milling is often a secondary or finishing process, but it can be used as the sole method of fabrication from start to finish. The different types of milling include face milling, plain milling, angular milling, climb milling, and form milling.
Uniquely shaped turrets on a punch press hit the metal through or into a die to create holes. The end product can either be the piece of metal with holes for fastening purposes, or it can be the now removed, and shaped metal pieces called the blanking. Most punch presses are mechanical but smaller, and simpler punches can be hand-powered. CNC punch presses are also now common and are used for both heavy and light metalwork.
One long, straight cut is achieved by combining two tools, with one of the tools above the metal and the other one located below for applying pressure. The upper blade forces the metal down onto the stationary lower blade and fractures it. The fracture then spreads inward for complete separation. The sheared edges are usually burred. It is ideal for cutting smaller lengths and differently shaped materials since the blades can be mounted at angles to reduce the required force.
This process is similar to punching, except the press doesn’t create a hole in the metal, but an indentation. The turret doesn’t completely force the metal through the die, but only raises it. Stamping is used to form shapes, letters, or images in a metal panel or sheet. Mechanical and hydraulic are the two types of stamping presses. Metal stamping machines cast, punch, cut and shape metal sheets. Sheets of up to 1/4 inch thickness are moulded into specified shapes and sizes. The presses used for metal stampings can create a wide range of products, and they can perform a series of operations including blanking, metal coining, and four slide forming. Metal coining (as the title implies) can be used to create coins, but it has other uses as well, such as parts for electronics. Four slide forming incorporates a variety of stamping and forming processes to create more complex products, and it is particularly effective for smaller parts.
With welding, two or more pieces of metal are joined together, through a combination of heat and pressure. This is a popular process because the pieces of metal can be any shape or size. Four of the popular types of welding procedures are Stick or Arc Welding, MIG Welding, TIG Welding, and Flux Cored Arc Welding.
Stick welding, also known as Shielded Metal Arc Welding (SMAW), uses an electrode stick that produces an electric current that forms an electric arc when in contact with metal. The high temperature of the arc welds the metal.
Metal Inert Gas Welding (MIG), or Gas Metal Arc Welding (GMAW), uses an externally supplied gas along with a continuous solid wire electrode to shield the metal from reacting to environmental factors so that welding is faster and continuous. The shielding gas also creates less welding fumes.
Tungsten Inert Gas Welding (TIG), also called Gas Tungsten Arc Welding, uses a tungsten electrode rod that creates a short arc to weld heavier metals, for heavy fabrication. This method requires a highly skilled welder, as the process is more difficult, but can be used on most metals and for complex projects.
Flux Cored Arc Welding (FCAW) has a similar process and equipment as MIG welding. The wire electrode used contains a core that produces shielding gas, so a secondary gas source is not needed. This method is more portable than MIG or Stick welding but can’t be used on thinner metals.
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What Qualities Should You Look for in a Fabrication Material?
Fabricating a part or product means making it from scratch using raw or semi-finished materials. This can really be anything, from copper or pine wood to complex composite structures or high-temperature epoxy laminate. You can even fabricate multiple parts from different materials and assemble them at a later stage in the manufacturing process.
There’s no inherent difference in quality between raw vs. semi-finished materials. The quality of any fabrication material is entirely relative. It depends on:
- How you want the finished part or product to function
- The fabrication company’s capabilities
- The finish you can achieve
- Whether the material is best suited for tight or loose tolerances (or either)
- The fabrication timeline
All of these factors are unique to your product and process. As such, it’s impossible to recommend any one type of fabrication material that works for every project. This is what makes choosing a fabrication material so challenging, especially for startup companies or entrepreneurs who haven’t gone through this process before. Fabrication materials lists can be overwhelming unless you know exactly what you’re looking for.
If you work with an experienced, full-service product fabrication company, this process is less daunting. A team of engineers can help you find the most appropriate materials for your needs based on their invaluable experience working with each material. Before you start a conversation with a product fabrication expert; however, it’s useful to know which types of fabrication materials are out there and what their potential advantages and disadvantages are.
Take a close look at your fabrication processes and identify all the issues that pose safety risks or that are generally frustrating to your team. Rank order the problems. (Note: The safety issues should be at the top of the list.)
Begin applying your Lean toolkit to removing these issues. It might sound a bit like a haphazard approach, but the goal is one that aligns with the big picture. You are attempting to build support for the problem-solving processes that continuous improvement demands. Once team members see that there is some benefit to them, they will be more willing to take on the bigger projects that improve flow.
Those types of changes—running smaller lots and arranging by product line rather than function—generate much more resistance. Having a solid track record of success makes people more accepting of the change.