Plastic Casting Process Explanation

Just like the casting of metals, the plastic casting process is also a very important process to produce various kinds of plastic parts. In plastic casting processes, both thermoplastics and thermosetting can be poured. This is the biggest advantage of plastic casting processes.

There are several plastic casting methods are used in industry;

  • The first method to cast plastics inside molds includes the polymerization of less complex molecules inside the molds to obtain long molecular chained polymers.
  • The second one is the pouring of plastisol which is the suspension of the fine particle of thermoplastics inside liquid inside heated molds. This suspension solidifies inside molds and forms the plastic part.
  • This is the most classical way to cast materials. Thermoplastic resins are heated to a highly liquid state and poured inside mold cavities. After the solidification, the plastic part is obtained.

Advantages And Disadvantages Of Plastic Casting Processes

Cast rubber part: Image Source:

In plastic casting processes, the used molds are simpler than other plastic molding processes such as injection molding. Another advantage of plastic casting processes is the suitability of low production quantities. This is also because of the requirement of particularly more time to complete one process cycle.

Viscoelastic memory is one of the most important problems in most plastic injection and extrusion processes. So, there is no problem with die swell or other types of problems caused by the viscoelastic memory of polymers.

The main disadvantage of the plastic casting process is the very high rates of shrinkages. About 20% of shrinkage may occur in plastic casting processes. This is a very high rate compared with metals. So, consideration of shrinkage is very important in plastic casting processes.

How Thermosettings Are Used In Plastic Casting Processes?

Resin cast part(Image Souce: Wikiwand).

The pouring and forming of thermosetting plastics in molds are slightly different than thermoplastics. Because of the cross-linking nature of thermosetting, primary ingredients of thermosetting material are poured inside molds. Also, other additives such as catalysts are added to improve cross-linking. When cross-linking occurs, solidification also occurs.

Thermosetting material must be suitable for casting operations. Very rapid rates of cross-linking are not suitable for the casting method. So, thermoplastic material must have slow rates of cross-linkings.

Materials And Applications Of Plastic Casting Processes

  • Electronic Encapsulation: Electronic parts can be coated with plastic casting processes. Electrical parts such as transformers, coils, connectors, etc. are coated with plastic casting processes generally.
  • Slush Casting: Slush casting is a plastic casting process in which the poured plastic forms shell-shaped structures inside the mold walls. After the solidification, the shell is de-attached from the mold.

Thermoplastic materials that are generally used in plastic casting processes; acrylics, nylons, and vinyl.

Most used thermosetting polymers in plastic casting processes; phenolics, epoxies, polyurethanesand polyesters.

  • Acrylic sheet production which is also called Plexiglass or Lucite is also a very important application of plastic casting processes. These sheets are used for optical purposes, so surface characteristics and molecular characteristics must be superior. In the plastic casting process, these features can be provided unlike plastic injection or extrusion processes.
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Plastic casting is also a special process to obtain special parts. This is the summary information about plastic casting.

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