Thermoforming Process

Thermoforming Process

The thermoforming process converts flat, two dimensional sheet into more complex three dimensional shapes through the application of heat and a pressure differential. The process will use single sided tooling, either male or female to define and control the shape of the part. The formed part will go through a trimming operation to become a finished part. The primary advantage of thermoforming is the relatively low cost and short lead time to construct single sided tools compared to other processes utilizing two sided closed molds. A secondary benefit is the rapid and economical design changes that can be accomplished on single sided forming tools and trim fixtures versus two sided closed molds. The thermoforming industry is divided into two general categories, thin gauge and heavy gauge. Thin gauge thermoforming, used mainly for packaging, will use materials less than .060" thickness. High speed, in-line equipment is geared to produce parts in the 10,000+ to millions. Heavy gauge thermoforming will use material .060" and thicker for low to moderate production volumes. Tru-Form Plastics is a heavy gauge thermoformer producing parts up to 5'x9' with draw depths to 28". Material starting gauges range from .060" up to .500". The majority of parts produced by Tru-Form Plastics will use material starting thicknesses between .125" and .250". Most of the parts produced will fall in the range of 2 square feet to 8 square feet in surface area. Depending on part size, production quantities can go from 50 parts to 5,000 parts. Thermoforming capability summary
Part size
Up to 5'x9' with draw depth to 28"
Material thickness
.060" to .500" - most common .125" to .250"
Quantities
Production runs 50 to 5,000 parts

Vacuum Forming Plastic Process (step-by-step)

  • A material blank which has a length and width greater than the finished part is loaded into a clamp frame to be carried through the process.
  • The blank in the clamp frame moves into an oven where it is heated to the forming temperature. At the forming temperature, the material is softened and pliable, but remains in a sheet configuration and is not melted.
  • The material is then moved from the oven to the forming station. The softened blank is then sealed on the deck of the tool. In some instances, low pressure air will prestretch the material to enhance wall thickness uniformity on the finished part.
  • A vacuum is drawn between the blank and tool to form the softened material against the tool surface. In pressure forming, while the vacuum is drawn to avoid air entrapment, positive air pressure is applied on the non tool side of the material to force the material against the tool surface.
  • An option for the process when using female tools is to use a 'pusher' or 'plug assist' on the non tool side of the blank to control and improve material distribution in the finished part.
  • The (now) formed part, while still in the clamp frame, is removed from the forming tool.
  • The clamp frame releases (opens) for part removal.
  • The formed part is now ready for the next step – trimming.