The term “thermoforming” refers to a manufacturing process during which plastic materials are made to form parts through heating, stretching and cooling. It yields medium to large scale results quickly, frequently producing uniform parts within seconds of each other.
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Advantages of Thermoforming
Thermoforming is a fairly inexpensive procedure, used to the benefit of industries including: cosmetics, sports and recreation, food processing, healthcare, entertainment, electronics, appliance, textile, toy and office supply. Thermoforming is valued in packaging and shipping in particular, because it allows them to quickly and economically receive products they rely on, like shrink wrap, bins, clamshells and blister packs.
Process of Thermoforming
The basic thermoforming process is carried out as follows: First, thermoplastic film or sheet is fed into a heating device; to raise the temperature of the plastic, the heater harnesses the power of either infrared radiation, natural gas or electricity. The plastic remains in the heater until it becomes pliable and soft. The time it takes and the temperature selected for this to happen depends on the properties of the plastic being used. Regardless, once pliable, the plastic is moved over to the form station, where it is stretched over a temperature-controlled surface known as a buck or a mold.
At this point, the technique used to solidify the form varies. Most often, manufacturers use a method called vacuum forming. During vacuum forming, a vacuum suctions the air between the plastic and the mold, forcing them together. Another common method of adherence-securing is pressure forming.
During pressure forming, pressurized air pushes the plastic into the mold. Of the two, pressure forming yields the best level of adherence and is preferred for detail-heavy applications. Another option is twin sheet thermoforming, which combines and seals two thermoplastic sheets together with a seam around their edges to form one uniform part.
Finally, drape forming involves draping the heated plastic over the mold in order to create parts with a gradual bend. After this step, the thermoforming process once again becomes fairly standard: the part is dried, allowed to cool, cured and ejected. If it needs it, it can then be trimmed via CNC machining, drilling, cutting or hand routing. Once this is done, it may undergo secondary processes like hot stamping or printing.
Types of Thermoforming
Generally speaking, thermoforming can be divided into two categories:
- Thin-gauge thermoforming and heavy-gauge, or thick, thermoforming. Those sheets that are less than .06 inches (1.5 mm) thick are formed by thin-gauge thermoforming procedures, while sheets that exceed .12 inches (3 mm) in thickness are formed via heavy-gauge thermoforming. Common thin-gauge products include disposable or recyclable items like food containers, lids, trays, cups and the aforementioned blisters and clamshells. Heavy-gauge thermoforming, on the other hand, yields more permanent products like cosmetic surfaces of refrigerators, kiosks, spas, cars and trucks, electronic equipment and more.
- Other Materials Used
- The list of plastics that manufacturers may use during thermoforming is quite varied. It consists of many thermoplastics, such as acrylic, crystalline polyester, low density polyethylene (LDPE), polystyrene, polyvinyl chloride (PVC) and polypropylene, as well as semi-gloss polymers and other plastics that exhibit qualities of moisture resistance, rigidity and durability. Manufacturers will select which one or ones to use for an application based on their qualities and how they match up with the needs of that application. Before proceeding with the process, they must also decide on clamping force, depth of draw, air pressure, machine dimensions and thickness.