It’s amazing what plastic can do. Recently, we explained how companies produce plastic products using the methods of blow molding, injection molding, casting, and extrusion. This post will review eight more plastic processing techniques, some of which are swiftly growing in popularity.
Thermoforming
Thermoforming is one of the simplest methods of processing plastic. First, a plastic sheet is heated to the ideal temperature for pliability; then, it is pressed into a mold. When cool, the molded plastic is removed and trimmed to form a usable part or product. Though not appropriate for all projects, plastic processors typically find thermoforming advantageous because it is incredibly inexpensive: The process is fast, requires only a half-mold, requires minimal plastic material, and exceedingly flexible for a variety of jobs.
Vacuum Forming
Like thermoforming, vacuum forming requires heat and a mold to process plastic. Inside an oven or under a heat lamp, the plastic is made pliable. A vacuum forces air into a chamber to stretch the plastic into a concave or convex mold, and the vacuum then sucks the air out, forcing the plastic tight against the mold. Because vacuum forming is a variation of thermoforming, it boasts nearly identical benefits as the previous method.
Compression Molding
Alongside heat, pressure can be used to force plastic into a new shape. This process is most often called compression molding, and it begins with plastic molding powder mixed with strengthening agents. When the mold is closed, pressure and heat are applied to the powder, causing it to harden into the desired shape. Processors can alter the temperature, the amount of pressure, the components mixed with the powder, and the length of time in the mold to affect the final product.
Transfer Molding
Like compression molding, transfer molding requires the application of heat and pressure, but unlike the previous method, this processing technique is mixed and heated outside the mold. Typically, the plastic is brought to pliability first, and then poured or placed into the mold.
This is advantageous for the creation of intricate products, such as those with many metal inserts or items with small, deep holes. With other processing methods, these components can shift during molding, altering the final product. With transfer molding, the plastic flows easily around the intricate details, ensuring perfection in the final product.
Reaction Injection Molding
One of the newest plastic processing techniques, reaction injection molding (RIM) requires the mixing of liquid plastic components in a low-temperature chamber. In fact, for RIM, the plastic needs only to reach between 75 and 140 degrees Fahrenheit before it is injected into a closed mold. Inside the mold, the plastic undergoes an exothermic reaction that forces it into the mold and causes it to stiffen. Because of the lower temperatures, RIM requires less energy than other injection systems, and it can produce incredibly tough plastic products.
Laser Cutting and Etching
Thanks to laser innovation, plastic processors can produce unique products without the costly creation of discrete molds. The process is simple: Plastic is placed below the laser, the laser is programmed with the appropriate pattern, and in minutes, a high-quality product emerges. Plus, laser cutting and etching is possible on a wide variety of plastics, including 3M tape VHB, as well as other materials, including metals and woods. With laser tools, materials processors don’t worry about tool wear, chipping, clamping, or reworking; lasers produce a perfect product every time.
Rotational Molding
Another popular plastic molding technique is rotational molding. This process is most often used to produce large hollow products. First, a plastic blank is placed into a cast, which is closed and put into an oven. As the oven heats, the plastic melts; then, the mold is rotated vertically and horizontally to coat the mold’s interior with the liquid plastic. After an appropriate amount of time, the mold is removed from the oven and carefully cooled to prevent the plastic from warping or cracking.
Calendering
Not unlike an old-fashioned clothing mangle, calendaring pushes plastic through dozens of rollers rotating at different speeds and serving different purposes. For example, there might be two sets of mixing rollers to build a plastic of the appropriate strength and color; there might be several heating rollers to make the plastic pliable; then rollers will shape the plastic to the correct thickness, cool the plastic, and wind the sheet up into a manageable spool.
