Molding & Its typesInjection MoldingRotational MoldingBlow MoldingCompression MoldingExtrusion MoldingTransfer Molding

Molding or moulding is the process of manufacturing by shaping pliable raw material using a rigid frame or model called a pattern.Molding technology has brought revolution in our daily life. With the passage of time it became modern and more efficient and effectively Its applications are in the ,automotive industries; it is used in plumbing industry, construction industry, and aero space industriesIts products are plastic bottles, water tanks, pipes, toys, bags and many more.Its major fields areInjection moldingCompression moldingRotational moldingBlow moldingTransfer moldingExtrusion molding

DEFINITION Injection molding is a process whereby a solid thermoplastic material is heated until it reaches a state of fluidity , is then transferred under pressure(injected) into a closed hollow space(mold cavity), and then cooled in the mold till it again reaches a solid state, conforming in shape to the mold cavity.HISTORY John Hyatt patented the first injection molder in 1872. . In 1951, William H. Willert invented the first molder machine to use a screw to provide continuous feed of liquid material. From the 1980s on, the most significant developments in injection molding have been in the area of computerization of the process.

John Hyatt William Willert

Injection molding machine

Apparatus descriptionInjection molding machines consist of a material hopper, an injection ram or screw-type plunger, and a heating unit and cooling system. presses hold the molds in which the components are shaped.Two types of operating systems

Plastic is melted through shearing and external heat, forced into the mold with a the screw.

Plastic is pre-melted in the hopper, fed into a chamber, and forced into the mold with a piston.

1. Reciprocating Screw System

2. Ram Injection Molding

MeltingThe process usually begins with taking the polymers in the form of pellets or granules and then Material is fed into a heated barrel, where it melted Injecting resinIn the injecting process the screw type plunger moves with the help of external rotating rods, and the heating system heats the granules. Part coolingIn the part cooling step the screw in the plunger moves the material to the mold part which is the cooling part where it is cooled andhardens to the configuration of the mold cavity. part ejectionIn part ejection The mold is then opened and the part is ejected.

Injection molding is used to create milk cartons, packaging.Bottle caps, automotive dashboards, pocket combs, toys and many plastic products It is used in plumbing industry and construction industryIt is used in automotive industryIt is used in aero space industry

Advantages Injection molding is the most common method of part manufacturing. It is ideal for producing high volumes of the same objectLow costs in mass production, low labour cost, minimal scrap lossesHigh precision

It has ability of using wide range of materialsLittle need to finish parts after molding

Disadvantages

High initial setup costsHigh initial cost-mold, Injection machine, Auxiliary equipmentHigh amount of scrap

DEFINITIONRotational molding, also known as rotomolding, is a molding process for creating many kinds of mostly hollow items, typically of plastic.Process descriptionRotational molding is a 4 stage process that includes adding material, heating, cooling, and demolding

Loading a measured quantity of polymer (usually in powder form) into the mold.

Heating the mold in an oven while it rotates, until all the polymer has melted and adhered to the mold wall

Cooling the mold, usually by fan. This stage of the cycle can be quite lengthy. The polymer must be cooled so that it solidifies and can be handled safely by the operator. The part will shrink on cooling, coming away from the mold, and facilitating easy removal of the partMold is moved to the open station where part is removed

Roto-moulded traffic cones with Reflective sleeve for night visibility.Rotational molding of plaster is used to produce hollow statuettes.Chocolate is rotationally molded to form hollow treatsIndustrial products like Tanks, containers, housingConsumer products like Desks, beds, dog houseFootballs, helmets.Recreational products like Toys, pools, ballsAgricultural products like Troughs, tractor cabs

Advantages

Low molding pressure allows use of light-duty moldsManufacturing large, hollow parts such as oil tanks is much easier by rotational molding than any other methodMolds can quickly be built and put into productionMold cavity is the only thing in contact with the material No scrap: material that goes in comes out as finished part

Disadvantages Surface details limited to outside surface-hollow moldMold is heated and cooled as well as plastic Long cycle times and high heat Maintaining precise dimensions is difficult

DefinitionBlow molding, also known as blow forming, is a manufacturing process by which hollow plastic parts are formed. It is a process used to produce hollow objects from thermoplastic.HistoryThe process of using air to blow hot material was first used by the Syrians, who realized that a glass bulb on the end of a blow pipe could be shaped into many useful hollow forms,. William Kopitke were the first verified personwho used the Blow Molding Process. In 1938, Ferngren and Kopitke produced a blow molding machine . In 1970, Coca-Cola test markets the worlds first plastic carbonated beverage bottle.

The blow molding process begins with melting down the plastic and forming it into a parison or preform. The parison is a tube-like piece of plastic with a hole in one end in which compressed air can pass through. A pressurized gas, usually air, is used to expand the hot preform and press it against a mold cavity. The pressure is held until the plastic cools. Once the plastic has cooled and hardened the mold opens up and the part is ejected

Toy wheels, automobile seat back, fuel tanks, flower pots, automobile bumpers, cabinet panels . Milk bottles, Pharmaceutical bottles, Antifreeze bottles, Polypropylene bottles Garbage cans

AdvantagesAdvantages of blow molding include: low tool and die costFast production rates Ability to mold complex part Produces recyclable parts.Increase the materials tensile Strength, barrier properties, clarity. Blow molding produces a container from less raw material and with improved economics properties.

DisadvantagesDisadvantages of blow molding include: limited to hollow partswall thickness is hard to control.

DEFINITION

The process of molding a material in a confined shape by applying pressure and usually heat Almost exclusively for thermoset materials. It is used to produce mainly electrical products

.

Molding compound is placed in an open, heated mold cavity.The mold is closed and pressure is then applied to force the material to fill up the entire mold cavity. Excess material is channelled away by the overflow grooves. The heat and pressure are maintained until the plastic material is cured.The final part after the mold Is removed

This process is commonly used for manufacturing electrical partsIt is also used for manufacturing dinnerware and type of products It is also used for manufacturing gears, cams This process is used to produce buttons, buckles, knobs, handles,Appliance housing, radio cases, and large containers.

AdvantagesLow initial setup costsFast setup timeGood surface finish (in general)Wastes relatively little material

DisadvantagesProduction speed is not up to injection molding standardsLess-than-ideal product consistencyIt is not suitable for some types of parts

Definition Extrusion is a process used to create objects of a fixed cross-sectional profile. It is like forcing of solid metal through a suitably shaped orifice under compressive forces. Extrusion is somewhat analogous to squeezing toothpaste through a tube, although some cold extrusion processes more nearly resemble forging, which also deforms metals by application of compressive forces. Most metals can be extruded, although the process may not be economically feasible for high-strength alloys.

In this process, a heated billet of metal is placed in a cylindrical chamber and then compressed by a hydraulically operated ram . The opposite end of the cylinder contains a die having an orifice of the desired shape; as this die opening is the path of least resistance for the billet under pressure, The metal, in effect, squirts out of the opening as a continuous bar having the same cross-sectional shape as the die opening.

Extrusion has found great application in food processing. Products such as pastas, breakfast cereals, French fries, baby food, dry pet food and ready-to-eat snacks are mostly manufactured by extrusion Chewing gums, drinking straws, plumbing pipes, door insulation seals, optical fibers, and steel or aluminum I-beams.A multitude of polymers are used in the production of plastic tubing, pipes, rods, rails, seals, and sheets or films. Many modern bricks are also manufactured using a brick extrusion process.

Advantages

Low initial setup costs Fast setup time Low production costs Advantages of this process over other manufacturing processes are its ability to create very complex cross-sections and work materials that are brittle, because the material only encounters compressive and shear stresses.

DisadvantagesModerate production speed Mediocre precision Limited to parts with a uniform cross section

Transfer molding process beginning with the uncured material placed in a transfer plate located above the cavity area, rather than being placed directly in the cavity as in compression molding applications. heat is then applied to the rubber and transferred from the transfer plat, being pushed through a gate by a piston, into the cavity where the material is then vulcanized using heat and pressure.

Step #1 - A piece of uncured material is placed into a portion of the mold called the "pot." The plunger (on the top-most part of the mold) fits snugly into the "pot.Step #2 - The mold is closed up and under hydraulic pressure the material is forced through the small hole (the "gate") into the cavity. The mold is held closed while the material cures.

Step #3 - The plunger is raised up and the "transfer pad" material may be removed and thrown away.Step #4 - Mold is opened and the part can be removed. The flash and the gate may need to be trimmed.

Some common products are utensil handles, electric appliance parts, electronic component, and connectors. Transfer molding is widely used to enclose or encapsulate items such as coils, integrated circuits, plugs, connectors, and other components.In the semiconductor industry, package encapsulation is usually done with transfer molding due to the high accuracy of transfer molding tooling and low cycle time of the process.

AdvantagesProvides more product consistency than compression molding Cycle times are shorter than compression molding Better than compression molding for rubber-to-metal DisadvantagesThe transfer pad is scrap Cycle time is longer than injection molding Product consistency is poorer than injection molding

****