Vacuum Forming
Vacuum Forming is a process of forming any type of plastic thin over a mold using vacuum pressure. The process begins by heating the plastic material, usually a sheet of plastic, until it becomes soft. The material is then pressed down over a mold until forms a shape. A vacuum is then applied to suck the air away from the formed material, in order to secure it tightly around the mold. The vacuum sucking the air away from the formed plastic is why this process is referred to as vacuum forming.
The process of vacuum forming is used for creating many different types of items such as boxes, parts for cars and planes, signs and product packaging. The advantages of using this process is that it is cost effective, relatively quick and can be used for very intricate shapes. It is considered a low to medium volume manufacturing process as it is substantially faster and cheaper than injection molding or blow molding processes. Vacuum forming is also an excellent choice when prototyping a product.
The process is used mainly for thermoforming thermoplastics, such as polystyrene, polyethylene, acrylonitrile butadiene styrene (ABS), and polyvinyl chloride (PVC). The selection of the plastic material is based on the application and the function of the part, an engineer must consider the properties of each material. The properties can include factors such as structural strength, rigidity, heat resistance and others.
Heating the plastic is the first part of the vacuum forming process. It can be done using different types of heating elements depending on the type of plastic and the size of the sheet. Common elements used for heat include gas ovens, radiant heaters and infrared heaters. The heat level must be balanced correctly in order to correctly form the plastic. Once the plastic is heated to its point of malleability, it is transferred to a vacuum forming machine.
The vacuum forming machine is what will create the vacuum in the plastic and form it over the mold. The machine is made up of two main parts, the clamp frame and the draw frame. The clamp frame is used to hold the plastic sheet in place, while the draw frame is used to apply a vacuum to the material. As the vacuum is applied the plastic is stretched and forms over the mold. The vacuum will hold the plastic in place until it cools and retains its shape.
Once the plastic has cooled, the formed part is removed from the machine and can be inspected. Any voids or flaws in the formed part are difficult to fix, and will requires the part to be cut from the sheet, melted down and reformed. Vacuum forming can also be used with other products such as foams, rubber and leather in combination with thermoforming. This is done to create certain desired characteristics or look in a product.
Vacuum forming is a transformative process that can be used to create custom parts and products. This process is mostly used for low to medium volume productions, while being a cost-effective and efficient production process.
