Overview of Plastic Processes 145

This class describes the most common plastic manufacturing processes and the machinery used to manufacture plastic components.

Class Details

Class Name:
Overview of Plastic Processes 145
This class describes the most common plastic manufacturing processes and the machinery used to manufacture plastic components.
Number of Lessons:
Additional Language:
Related 2.0 Classes:
Introduction to Plastics 131, Thermoplastics 251

Class Outline

  • Objectives
  • Manufacturing Plastics
  • Polymer Structure
  • Extrusion
  • The Pros and Cons of Extrusion
  • Injection Molding
  • Pros and Cons of Injection Molding
  • Compression Molding
  • Pros and Cons of Compression Molding
  • Casting
  • Pros and Cons of Casting
  • Thermoforming
  • Pros and Cons of Thermoforming
  • Rotational Molding
  • Rotational Molding Machines
  • Pros and Cons of Rotational Molding
  • Blow Molding
  • Pros and Cons of Blow Molding
  • Foaming
  • Foaming Processes
  • Pros and Cons of Foaming
  • Summary


  • Describe the different ways to manufacture plastics.
  • Describe the different kinds of plastics and their molecular structure.
  • Describe the extrusion process.
  • Describe the pros and cons of extrusion.
  • Describe the injection molding process.
  • Describe the pros and cons of injection molding.
  • Describe the compression molding process.
  • Describe the pros and cons of compression molding.
  • Describe the casting process.
  • Describe the pros and cons of casting.
  • Describe the thermoforming process.
  • Describe the pros and cons of thermoforming.
  • Describe the rotational molding process.
  • Describe the rotational molding machines.
  • Describe the pros and cons of rotational molding.
  • Describe the blow molding process.
  • Describe the pros and cons of blow molding.
  • Describe the formation of foam.
  • Describe the different foaming processes.
  • Describe the pros and cons of foaming.

Job Roles



Vocabulary Term Definition
backdrilled The method of drilling vents into a mold so that the vent hole is wider on the outside of the mold than it is on the inside. Backrilling vents allows air to escape easily from the mold.
barrel The holding chamber of an extrusion or injection molding machine. The barrel holds the resin as the screw melts and mixes it.
base The foundation of a machine that supports all the other machine components.
blow molding A plastic shaping process in which heated resin is clamped over a mold while positive air pressure blows the resin into its desired shape.
casting A plastic shaping process in which heated resin is placed in a mold and allowed to solidify. Pressure is not applied to the resin during the molding process.
casting foaming A foaming process in which resin and a specific amount of foaming agent are placed in a mold. The foaming agent forces gas into the resin, forming foam.
cell casting A casting process in which melted resin is poured between two panels to solidify. This process is typically used to make clear panes.
chemical foaming The formation of foam by inserting chemicals into a resin. The chemicals produce gas, which forms foam.
chlorinated fluorocarbon (CFC). A volatile organic compound that is used in the manufacturing of foam. CFCs deplete the ozone layer and are now often replaced by hydrochlorofluorocarbon, which is safer.
clam shell machine The simplest rotational molding machine in which the mold is placed inside until the resin has sufficiently heated and cooled. The machine resembles a clam shell.
coextrusion A variation of the extrusion process in which two streams of different molten resins are combined to form one stream. During coextrusion, the different resins do not mix together.
collapsible That which is capable of collapsing or being compressed.
compression assembly The large, upper section of the compression press that holds the male die half. The compression assembly moves up and down, allowing the male die have to shape the plastic material on the female die half.
compression molding A molding process in which resin is placed between dies. Pressure is applied until the resin heats, forms to the dies, and cools.
compression press The machine in which compression molding takes place.
continuous casting A casting process in which resin moves between two moving sheets. The distance between the two sheets dictates the thickness of the resin.
cross-linking The development of primary bonds that form between polymer molecules. Thermosets are heavily cross-linked, while thermoplastics are not cross-linked.
cycle time The time it takes for a resin to be heated, molded, and cooled. Cycle times vary with the method of shaping used.
daylight opening The farthest space between the base and the compression assembly on a compression press.
die A tool containing a recess, which provides space for the shaping of plastic.
dip casting A casting process that involves repeatedly dipping a product or part of a product into resin. Repeated dipping results in a thicker coating of resin.
embedding A casting process that encases a part in resin, as if that part were to be embalmed.
encapsulation Another term for dip casting.
expanded foam molding Foaming process that traps volatile gas. When the gas is heated, it expands, forcing the resin to expand as well.
extruder screw A long screw that turns inside the barrel of the extruder machine. The extruder screw heats and mixes the resin.
extrusion A plastic shaping process in which resin is melted and then pushed out of the machine. As it exits the machine, a die shapes the resin.
extrusion blow molding A blow molding process in which the resin is extruded into a mold before it is blown into the desired shape.
extrusion foaming A foaming process similar to extrusion. During extrusion foaming, the resin is mixed with a foaming agent as it ejects from the extrusion machine.
feed throat The entryway for the resin into the extrusion barrel. The feed throat connects the hopper and the barrel.
feed zone A section of the injection screw that moves resin into the barrel.
female die The concave die used in compression molding on which the resin is placed. The female die half rests below the male die half.
filler Particles added to plastic resin to take up space. Fillers are often used to lower costs.
film casting Casting process in which resin is coated onto a moving belt. The belt moves to a heater that cures the resin.
foam molding The shaping of plastic foam. The first step of foam molding is to turn resin into foam by inserting air bubbles.
gasket A device that holds the two plates used in cell casting. The gasket also functions as the base of the mold.
hollow glass foaming A foaming process in which tiny hollow glass spheres are mixed with resin. The resulting material is foam.
hopper A large, funnel-shaped device located on the top of the barrel on extrusion and injection molding machines. The hopper serves as the entryway for resin into the barrel.
hydrochlorofluorocarbon (HCFC). A chemical compound that has been used to replace chlorofluorocarbon in the formation of foam. HCFCs are less harmful to the ozone layer than CFCs.
infrared radiation The emission of energy that is outside visible range. Infrared radiation can harm certain plastic products.
injection blow molding A blow molding process in which the resin is injected into a mold before being blown into the desired shape.
injection molding A molding process in which resin is heated in a barrel and then injected into a mold by a reciprocating screw.
injection screw A device in the injection molding machine that melts, mixes, and moves the molten resin through the machine. The injection screw is in the barrel.
jacketed rotational molding A variation of rotational molding in which the resin molds are heated through thermal conductors in the mold wall.
joining Bringing two separate materials together through some type of forming. Joining is one of the four main ways plastics can be formed.
male die A convex die used in compression molding that presses against the resin in the female die.
matched die molding Another term for compression molding.
material removal The removal of plastic from a given area to create a part. Material removal is often the last step in a shaping process.
mechanical foaming Forming foam by whipping a resin. The whipping action produced by mechancial foaming disperses air throughout the resin.
mer The basic molecular unit of plastic that combines in long chains to form polymers.
metering zone A section of the injection screw in which resin is pumped to the mold area to be formed.
microballoons The hollow glass spheres mixed into resin during hollow glass foaming. Microballoons are roughly 0.0012 inches (0.03mm) in diameter.
mold casting A casting process in which liquid resin is formed by being poured into a mold.
mold tree A frame within the casting oven on which different molds may be placed for simultaneous heating.
ozone layer A region of the upper atmosphere containing concentrations of ozone, which is a form of oxygen that absorbs ultraviolet radiation. CFCs deplete the ozone layer.
painting A casting process in which the resin is applied by brush or roller to the object being coated.
parison A cylindrical tube of resin that is placed within a mold. Positive air pressure forces the parison to fill the mold.
physical foaming A foam forming process during which gas is inserted into resin.
plastic A material consisting of very large molecules characterized by lightweight, high corrosion resistance, high strength-to-weight ratios, and low melting points. Most plastics are easily shaped or formed.
polymer A material made of very large molecules that generally does not have a crystalline structure. Polymer is a technical term for plastic.
polymerize The chemical process of forcing small molecules to bond together, forming macromolecule chains of polymers.
polystyrene A thermoplastic polymer that can be molded or made into foam, and is often used as an insulator. Polystyrene resin is used during expanded foam molding.
preform A plastic part of generic shape that is later reheated and formed into a finished product by blow molding.
preform tube A tube-shape section of plastic that is later reheated and blow molded into a predetermined shape.
pressure thermoforming A variation of thermoforming in which positive air pressure forces resin against a mold.
pultrusion A molding process in which heated resin cures as it is pulled through a die. Pultrusion is a variation of the extrusion process, during which resin is pushed through a die.
pyrometer A device that measures the temperature of plastic through the radiation emitted by the substance.
resin A raw polymer, usually in the form of beads or pellets, that is not yet formed into its final molded shape.
rotational molding A plastic shaping process in which resin heats inside a rotating mold. Rotational molding forms hollow parts.
rotomolding Another term for rotational molding.
scrap Any material not used to create the final part. Some processes require the scrap to be grinded away.
secondary shaping A shaping operation that occurs after plastic has already been formed or molded.
shaping The process of changing the shape of a piece of plastic. Extrusion and casting are examples of shaping processes.
shuttle machine A rotational molding machine in which heating and cooling takes place in different areas. Shuttle machines offer greater turnover than clam shell machines.
spray foaming The use of pressurized foam resin to cover a surface. Spray foaming is often used for insulation purposes.
take-up roller A device used to collect the molded product during film casting or solvent casting.
thermoforming A plastic shaping process that shapes heated plastic sheets around a mold.
thermoplastic A polymer that is solid at room temperature and can be melted at high temperatures. Thermoplastics can be shaped by heating and then applying pressure.
thermoplastic sheets Flat pieces of solid plastic resin that will be reheated and shaped during a secondary shaping operation. Thermoplastic sheets are used particularly during thermoforming.
thermoset A polymer that can be either a liquid or solid. It can be molded by heating and placing into a mold. Once a thermoset has cured, they cannot be remolded.
thick-gauge thermoforming Another term for pressure thermoforming.
thin-gauge thermoforming Another term for vacuum thermoforming.
transition zone The section of the injection screw around which resin is melted.
transparent Having the quality of lallowing light to pass through. Some plastics are transparent.
twin-sheet thermoforming A type of thermoforming in which two separate heated plastic sheets are welded together at their edges to make hollow parts.
vacuum thermoforming A variation of thermoforming in which positive air pressure forces resin against a mold.
vent A small opening in a mold that allows air to escape as resin solidifies.
viscosity A fluid's resistance to flow. In general, the hotter a resin is, the lower its viscosity.
void A gap or lack of definition in the final molded product. Voids can occur in casting because no pressure is used on the resin while it fills a mold.