How It Works
Vacuum forming, also called thermoforming, is the process of heating a plastic sheet and stretching it over a mold or pattern. This type of molding from D&D Plastics can be used to create a variety of parts, including concrete molds. It is particularly popular for contoured packaging that requires high precision and detail, such as food storage containers or medical equipment that meets stringent sterilization guidelines.
During the vacuum forming process, a thermoplastic sheet is heated until it becomes soft, then stretched over the mold and suck down tightly using vacuum pressure. This process creates durable, reusable, and highly sturdy parts that can support rapid prototyping. Once the part is formed, it’s trimmed and cooled. A band saw can be used to trim away the excess plastic and leave a border around the edge of the form.
Plastic vacuum forming can be a useful tool for making concrete molds, but it’s not without its problems. For starters, the absorbing moisture that can occur during the forming process can expand and weaken the plastic. Additionally, webbing can form around the mold and objects may stick to it. These issues can be addressed by decreasing the amount of vacuum and air that’s used during the forming process.
Outside of concrete, a wide range of materials can be used as a vacuum-forming mold, including wood, plaster, and cast phenolic or epoxy resin. For short to medium runs, wood and plaster molds work well, while for longer production runs, metal molds are the most effective option.
The heating time varies depending on the type of plastic being used. In the case of polystyrene, it is usually about 160 seconds. Once the heating and vacuuming steps are complete, the sheet that contains the formed material is placed into a 5-axis CNC trimming station or trim press where it is trimmed to its final size. Any holes that were necessary are also drilled at this stage. This process is a relatively quick one with the heating and vacuuming steps typically taking only a few minutes. However, the cooling and trimming steps can take longer, especially if the parts being produced are in very intricate shapes or sizes. Contact us to get started on your own thermoforming project today!
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