In polymer casting, a reactive liquid resin or rubber fills a mold that reacts chemically and solidifies. Typical polymers for casting include polyurethane, epoxy, silicone and acrylic. Flexible molds made of latex rubber or vulcanized silicone rubber at room temperature (RTV) are economical compared to hard tools, but they can only produce a limited number (about 25 to 100) of castings, since the chemical reaction of urethanes, epoxies, polyester and acrylic degrades mold surfaces. Polymer casting is relatively inexpensive, with little initial investment, but thermosetting polymers for casting are often more expensive than their thermoplastic counterparts and molding castings requires a lot of labor.
Each casting requires manual labor for post-processing, making the final cost per part high compared to automated production methods such as injection molding. Polymer casting is commonly used for prototyping, short-run production, and certain dental and jewelry applications. A variety of plastic manufacturing processes have been developed to cover a wide range of applications, part geometries and types of plastics. Softer thermosetting plastics require specialized tools to support the parts during machining, and filled plastics can be abrasive and reduce the life of the cutting tool.
Plastic manufacturing processes are constantly evolving and the tipping points at which it makes sense to move from one technique to another are changing due to improvements in equipment, materials and economies of scale. One way to control the surface texture of a plastic film during manufacturing is through electrical treatments. Electricity is sent through the film to a metal roll connected to electrical ground called a treating roll, around which the film is wrapped. This process helps to control static electricity and improve surface texture.
Another method used in plastic manufacturing is blow molding. This technique is used to create hollow plastic parts by inflating a heated plastic tube inside a mold until it takes on the desired shape. Problems related to laminating, sealing and printing on thin extruded films and plastics such as polypropylene and polyethylene are very common for manufacturers. It is possible to control these additives and detect them before they can interrupt the plastic film production process. CNC machining is another method used in plastic manufacturing.
Unlike most other plastic manufacturing processes, CNC machining is a subtractive process in which the material is extracted using a rotating tool and a fixed part (milling) or a rotating part with a fixed tool (lathe). A similar method, known as reaction injection molding (RIM), is used to manufacture thermosetting plastic parts. Compact desktop or desktop 3D printing systems for creating plastic parts are also becoming increasingly popular. While most plastic manufacturing processes require expensive industrial machinery, dedicated facilities, and trained operators, 3D printing allows companies to easily create plastic parts and rapid prototypes in their own facilities. Some of them are used as aids in the manufacturing process, ensuring that plastics do not stick to molds and the like. Finally, vacuum forming or thermoforming is another manufacturing method in which a plastic is heated and formed, usually using a mold.
This process helps control surface texture by allowing manufacturers to adjust temperature settings. In conclusion, there are several ways that manufacturers can control surface texture when producing plastic films. Electrical treatments help control static electricity while blow molding helps create hollow parts with desired shapes. CNC machining and 3D printing systems are also becoming increasingly popular for creating plastic parts quickly and easily. Finally, vacuum forming or thermoforming allows manufacturers to adjust temperature settings for better surface texture control.