Plastics are some of the most common materials used to produce commercial items. Manufacturers use these materials to create everything from medical devices to consumer products.
Plastics can be made from thousands of types of polymers, each of with its own unique mechanical properties. Engineers have created plastic manufacturing processes that cover a wide variety of part geometries and applications.
Many methods are used to create plastic products. Some of the most efficient plastic manufacturing techniques include:
Injection molding works by injecting a mold with molten thermoplastic. Because molds can be custom designed, and because the plastic conforms completely to each mold used, this process can create large amounts of highly intricate products. This is the most common process used to mass manufacture plastic parts.
Manufacturers use this technique to create hollow plastic parts. To build desired shapes, manufacturers inflate a heated plastic tube inside a mold. This process is continuous and can be completely automated, which results in low unit costs and high rates of production.
Manufacturers perform thermoforming by using air-based or mechanical processes to mold plastic sheets into the desired shapes. Air pressures used can range from nearly zero psi to several hundred psi.
When thermoforming at 14 psi, which is equivalent to the Earth’s atmospheric pressure, manufacturers instead create pressure by removing the space between the sheet and the mold. This process is referred to as vacuum forming.
Manufacturers use extrusion to create products such as:
- Continuous sheeting
- Profile shapes
Similar to injection molding, extrusion refers to a process in which workers feed dry plastic material into a hopper, which conveys it into a long heating chamber. The difference between these two processes, however, lies at the end of the heating chamber: During extrusion, the plastic is forced out of a die or small opening in the desired shape. After the material leaves the die, manufacturers move it to a conveyor belt, where it cools.
Unlike more common plastic manufacturing processes, CNC machining is a subtractive process. Plastic is removed by either by milling (using a fixed part and spinning tool) or lathing (using spinning parts with fixed tools). Machining is best suited for building low-volume plastic part applications that require geometries that are hard to mold but still require tight tolerances.
Manufacturers can draw from thousands of types of polymers when designing plastic products. Each polymer has its unique derivatives, base chemistries, and additives that suit it to unique aesthetic and functional requirements. Most plastics shake out into one of two categories: thermoplastics and thermosets.
Thermoplastics are the most widely used type of plastic. They’re durable enough to withstand many melting and solidification cycles without significantly degrading.
Thermoplastics normally come in the form of sheets or small pellets. Workers heat and form these into the required shape using a number of manufacturing processes. Since no chemical bonding occurs, the process is wholly reversible, which makes it feasible to recycle or melt thermoplastics for reuse.
After curing, thermoset plastics permanently remain in a solid state. Polymers in thermosetting plastics cross-link during the curing process, which is induced by suitable radiation, light, or heat. Because the curing process forms an irreversible chemical bond, thermoset plastics will not reform upon cooling and not melt when heated. Instead, they will decompose when exposed to extreme heat. This makes it nearly impossible to recycle thermosets or turn the plastic back into its base components.
Industries that use thermoset plastic parts daily include:
- Electronic and electrical
- Home products
- Medical and pharmaceutical
Mardek leads the field in offering high-quality, custom plastic manufacturing and machining services. Our long-standing relationships and ISO 9001–certified manufacturing facilities guarantee the highest level of quality for your products.
Contact us today to request a quote on our quality plastic manufacturing services.