Manufacturing is defined as the conversion of raw materials into the finished goods on a large scale using man and machine whereas manufacturing processes are defined as the methods used for conversion of raw materials into finished products. Based on the product requirement there different types of manufacturing processes which are used to get the required output.
In this article, you are going to learn about the seven types manufacturing processes and their subtypes with examples.
Types of Manufacturing Processes
Some websites mention four types of manufacturing processes while some mention five types of manufacturing processes. Although, Wikipedia lists 7 main types of manufacturing processes which we are going to discuss below.
7 Main types of Manufacturing Processes and their subtypes
Casting is a process of pouring liquid metal into a mold containing the hollow shape of the desired outcome. It uses sprue, gates, and runners to pour the metal. The main types of manufacturing processes under casting are:-
Centrifugal casting is a process of pouring molten metal into a spinning die. Spinning die creates high g-forces to the molten metal which gives it the cylindrical shape. Moreover, spinning let the impurities (less dense material) to float at the inner dia from where it is removed later. Spinning can either be on a vertical or horizontal axis depending on the configuration of the desired part such as vertical rotation is used to cast ring and cylinder and horizontal rotation is used to cast tubular shapes .
Some examples of centrifugal casting include jet engine compressor cases, petrochemical furnace tubes, military products, and other high-reliability applications.
Die casting is a manufacturing process used for producing metal parts where high precision is required. This process is accomplished by forcing molten metal under high pressure into reusable metal dies. High volume production is done using this process.
- Steel molds capable of producing several castings at once are produced.
- Molds are mounted securely in a die casting machine and are arranged so that one is stationary while the other is moveable.
- The die cavity is injected with molten metal and allowed to solidify and the part is ejected.
Die casting process is used for producing precise non-ferrous metal parts. Some examples of die casting include engines, clutch housings, and covers of a four-wheeled vehicle.
Sand casting is a metal casting process that uses sand as the mold material. This process has a low production rate as the sand mold must be destroyed in order to remove the part. Although, it is a cheap process when low volume production is required.
- Furnace, metal, pattern, and sand mold are used in the sand casting process.
- The molten metal is poured using ladle into the cavity of the sand mold, which is made from the pattern.
- The casting is allowed to solidify and then removed by breaking the mold.
More than 70% of all metal castings are produced via sand casting process. Some examples of sand casting process include engine blocks, machine tool bases, cylinder heads, pump housings, valves, gears, pulleys, crankshafts, connecting rods, and propellers.
Permanent Mold Casting
Permanent mold casting is a manufacturing process that offers reusability of metal molds which makes it eligible for high volume production. This process uses gravity or vacuum or gas to fill the mold.
- The mold is preheated and a ceramic coating is applied to the mold cavity surfaces to facilitate part removal.
- The molten metal is poured from a ladle and gravity or vacuum is used to raise the molten metal into the mold assembly.
- The casting is allowed to solidify and then removed by opening the mold assembly.
Some examples of permanent mold casting include gears, pipe fittings, fuel injection housings, splines, wheels, gear housings, engine pistons.
Note the difference: Sand casting uses an expendable mold which is destroyed after each cycle whereas permanent mold casting and die casting uses a metal mold that is reused for several thousand times. Permanent mold casting process is considerably slower, and not as precise as die casting. Also, an external force is used to inject molten metal in die casting as compared to gravity or vacuum in permanent mold casting.
Continuous casting is a manufacturing process used to cast a continuous length of metal. Unlike other processes of casting, the timeline of steps in continuous casting is entirely different all the steps in continuous occur congruently making it a less time consuming process.
- The molten metal is allowed to pass through the mold at a constant rate where it takes the two-dimensional shape of the mold.
- The casting will keep traveling downward and takes an indeterminate length. Gas cutting tools are used to cut it into the required shape.
It is used to produce long strands from aluminum, steel, and copper. Some examples of continuous casting include slabs, landing gear bushings, sleeves and pipe supports for propulsion systems in Marine ships
Investment casting is metal casting process of pouring molten metal into an expendable ceramic mold. This process is also known as “lost-wax casting” as the wax pattern is melted out of the mold when molten metal is poured. Complex parts are made using this process.
- The wax pattern is prepared and surrounded/invested by the ceramic slurry that hardens it and converts it into a mold.
- The mold is preheated to evaporate the wax and the molten metal is poured from a ladle into the mold.
- The casting is allowed to solidify and then the mold is broken and the casting removed.
Some examples of investment casting include turbine blades, airplane parts, firearm components and military equipment.
Shell molding is a metal casting process that uses a sand covered with resin to form the mold. This process is similar to sand casting process but has better dimensional accuracy, higher productivity rate, and lower labor requirements. Also, the Shell Molds are reusable and expandable.
- A two-piece metal pattern is created in the shape of the desired part using iron or steel.
- These patterns are clamped to a dump box containing the mixture of sand and a resin binder. This is known as shell preparation method.
- These shells are joined together and clamped to form the complete shell mold and the molten metal is poured from a ladle into the mold cavity.
- After the casting is solidified, the mold is broken and the casting removed.
Shell molding is used for producing high precision parts. Some examples of shell molding include gear housings, cylinder heads, connecting rods, and lever arms.
Molding is a manufacturing process that uses a rigid frame to shape hot liquid or a ductile raw material. It is mostly used to manufacture plastic products. The different types of manufacturing processes under molding are: –
Injection molding is a molding process used for producing parts by injecting molten material into a mold. It is the most commonly used molding process for manufacturing plastic parts. This process requires the use of an injection molding machine, raw plastic pellets, and a mold to get the desired output. The plastic is melted in the injection molding machine with the help of heaters and then a rotating/reciprocating screw injects it into the mold, where it cools and solidifies into the final part.
Some examples of injection molding include automotive parts and components, game toys, chairs, tables, storage containers, housing for household appliances, consumer electronics, buckets.
Blow molding is a molding process used to manufacture hollow plastic parts. This process starts with melting down the plastic and forming it into a parison. The parison is then clamped into a mold and air is blown into it. This air pushes the plastic out to match the mold. The plastic is allowed to cool and later the mold opened and the part is ejected. Although the blow molding process is costlier than injection molding, it is still used for manufacturing many plastic products.
Blow molding is divided into three types of manufacturing processes namely extrusion blow molding, injection blow molding, and injection stretch blow molding.
Some examples of blow molding include automotive ducts, stadium seating chairs, containers, trays, reservoirs, tanks, coolers, fan housings, panels, doors, toys, sporting goods, watering cans and household products, carrying cases.
Extrusion Molding is a process used to manufacture long tube-shaped products of a fixed cross-section. This process uses an extrusion machine to force the heated plastic through a die with an opening. The machine uses a reciprocating/rotating screw to feed the plastic into the die. The die then forces the material into the desired shape or the shape of the die. Heaters are used to melting the plastic in the extrusion machine. The material is allowed to cooled and then cut down into the required shape.
Some examples of extrusion molding include pipe, tube, plastic films and sheeting, thermoplastic coatings, and wire insulation.
Rotational Molding is a molding process used for manufacturing hollow parts. This process is accomplished by placing resin into a hollow mold and then rotating that tool bi-axially in an oven. There is no pressure involved in this technique, unlike other plastic manufacturing processes. Thus, making the mold cost cheap and the process economical.
- The mold is filled with a polymer resin and heated in an oven until the resin melts inside of the mold cavity.
- It is then slowly rotated to disperse and stick the soft material inside the mold cavity.
- A cool tool is used to solidify the part and later the part is removed from the mold.
Some examples of rotational molding include water tanks, medical products, consumer’s products, toys, leisure craft, sporting equipment.
Thermoforming is a molding process where a plastic sheet is heated to an elastic forming temperature and formed into the desired shape. This method is often used for sample and prototype parts. It is divided into three types of manufacturing processes namely vacuum forming, pressure forming and mechanical forming.
- The thermoplastic sheet is heated using either convection or radiation until it gets soften.
- This soft sheet is then pressed against the mold using the vacuum or air pressure or mechanical force.
- The excess material is then trimmed away and the formed part is released.
Some examples of thermoforming include switchgear, motor components, thrust washers, ash cups, valve covers, disc brake pistons, knobs, and handles.
Powder metallurgy is a molding process used for manufacturing precision metal components from metal powders. The rate of production of parts is quite high in powder metallurgy which makes it economical than the other casting processes.
- A homogeneous mixture of metal powders or alloy powders is prepared.
- The metal powder is then pressed into the desired shape at room temperature.
- At last, the product is heated that causes the powder particles to fuse together without melting.
Some examples of powder metallurgy include self -lubricating bearings, porous metal filters, gears, cams, brackets, sprockets.
Forming is a manufacturing process that uses suitable stresses such as compression, tension or shear to deform the material and get the desired shape. This process involves deformation and displacement of material leading to no material removal or loss of material. The different types of manufacturing processes under forming are: –
Forging is a manufacturing process that uses compressive forces to shape the material. This process is accomplished with the help of a hammer, press or a special forging machine. The forged parts have good strength and toughness without the defects of porosity, inclusion or voids, also they can be used reliably for highly stressed and critical applications.
Forging may be carried out on materials in either hot or cold state and therefore, it is divided into types of manufacturing processes i.e. cold forging and hot forging.
Some examples of forging include hammers, sleds, wrenches, garden tools, sockets, hardware, hand tools, edged weapons, cymbals, jewelry, rivets, bolts.
Bending is a manufacturing process used to deform metal into the desired shape by using a die and punch. This process is most commonly used for sheet metal products to get the required U-shape, V-shape or the channel shape. Commonly used bending machines are pan brakes, brake presses, and other specialized machine presses.
- The material is placed on the die and positioned in place with the help of stops.
- The upper part of the press with appropriately shaped punch attached to it, descends and forms the V-shaped bend.
- The U-punch forms the U-shape with a single punch.
Some examples of bending operations include electric enclosures, electrical boxes, brackets, rectangular ductwork.
Stamping or pressing is a manufacturing process in which thin walled metal parts are shaped desirably with the help of punches and dies. This process is accomplished by placing flat sheet metal into a stamping press where a tool and die surface forms the metal into the desired shape. Stamping uses hydraulic or mechanical press to perform the operations which can be done at a single die station or multiple die stations. Also, this process is usually carried out on sheet metal, but can also be used on other materials, such as polystyrene.
Some examples of stamping include trunks, doors, panels, enclosures, fenders, roof, and hood outer parts.
Shearing is a manufacturing process used to remove a blank of required shape and dimension from a large sheet of metal, paper or plastics. This process includes cutting of sheet without the formation of chips or the use of burning or melting. Shearing is divided into following types of manufacturing processes: –
- Roll slitting
- The punch applies pressure on the sheet forming cracks on both the top and bottom edges of the sheet.
- The punch goes down further to grow these cracks and eventually separate the slug from the material.
Some examples of shearing include industrial machinery, automobile parts, electronic equipment, knives, scissors.
Machining is a manufacturing process used to cut a piece of raw material into the desired shape and size with the help of controlled material-removal process. These processes are based on a common theme known as subtractive manufacturing. The machining process is used for all the types of product especially metal products. The different types of manufacturing processes under machining are:-
- MIlling – Milling is a process of removal of material from a workpiece useing rotary cutters and getting the desired shape.
- Turning -Turning is a process of removal of unwanted material from circular parts using a cutting tool. This process requires a lathe, workpiece, fixture, and a cutting tool.
- Shaping – Shaping process uses a cutting tool that reciprocates against a stationary workpiece producing a plane or a desired surface.
- Drilling – Drilling process uses a drill bit to make a hole of circular cross-section into the solid material.
- Honing – Honing process produces a precision surface on a metal workpiece by scrubbing an abrasive stone against it.
- Finishing – Finishing process is used to improve appearance, adhesion, wettability, wear resistance, hardness or to remove burrs and other surface flaws with the help of sanders.
Joining or assembling process are part of every production processes where two or more parts are combined together to get the required product. The main types of manufacturing processes under joining are:-
- Welding – Welding process is used to heat and melt two or more parts and force them together making a single functional part. Arc welding, resistance welding, oxyfuel gas welding are few types of welding operations.
- Soldering – Soldering process is also used to join two or more metal items by melting and putting a filler metal (solder) into the joint. It differs from welding as it does not involve melting of the workpieces.
- Brazing – Brazing process is used to join two or more metal items together by melting and flowing a filler metal into the joint. Brazing uses higher temperatures for a similar process as compared to soldering. Also, it requires much more closely fitted parts than in soldering.
- Adhesive Bonding – Adhesive bonding is used to hold multiple closely spaced parts together using a filler material called an adhesive. It is mainly used for a non-metallic substance such as a polymer.
- Mechanical Assembly – It is a fastening process which uses nut, bolts, and rivets to join the parts together. It is also a reversible joining process.
6. Coating or Plating
This process is defined as a method of covering the part surface with powder or zinc or other chemicals to protect it from corrosion, wear and other defects. It is also done to improve the electrical conductivity or magnetic response of the material. The main types of manufacturing processes under the coating process are powder coating, electroplating, sputter deposition.
7. Additive Manufacturing
Additive manufacturing is the process reversible to subtractive manufacturing i.e. machining. It is a manufacturing process that builds 3D objects by adding layer-upon-layer of material, whether the material is plastic, metal or concrete. Additive manufacturing comprises many technologies such as 3D printing, rapid prototyping, direct digital manufacturing, layered manufacturing and additive fabrication. This technology is growing at a very fast speed due to its high-efficiency and accuracy.
Some examples of 3D printing include jewelry, toys, decorative items, phone cases.
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