Thermoforming

• Thermoforming starts with a film or sheet. The sheet is then heated where it becomes soft but not melting. The sheet is brought down on a mold, or the other way around, to form the desired product.
• Since molding temperatures are very low, thermoformed molds are very economical.
• For prototypes molds, material like wood, epoxy, or plastic is commonly used.
• For mass production, aluminum or beryllium/copper may be used.
• Two main types of molds:

  • Male, core, positive
  • Female, cavity, negative
• Thermoformed parts need draft angles to be dismolded. The deeper the part, the greater the angle.

  • Male mold - 5 ° to 7 ° taper angle
  • Female mold - 2 ° to 3 ° taper angle
• Thermoformed parts cannot have undercuts.
• Most common packaging application are blister and clamshell packaging, made from PVC and sometimes PET and HIPS.
• Thermoforming is also used for tubs as replacement to injection molding. But a thermoformed part may not have the precision required to fit a snap-on lid.
• Through thermoforming cannot make hollow objects with narrow necks two halves can be thermoformed then joined.
• Thermoforming methods

  • Matched Die Forming
  • Vacuum forming
  • Pressure Forming
  • Plug Assist Forming
  • Billow Forming
  • Skin Packaging
• Microwavable Packaging

  • PP
  • PS
  • CPET
• CPET can be used for the two common types of oven - microwave and conventional ovens. It has better water and oxygen barrier than the other plastics in the category. It also has good grease and oil resistance and minimally affects food taste; it is costly.
• PP can be used for microwave but not conventional ovens. Has low density blends of PS can also be used.
• • Injection Molding has a gate mark.
  • IBM bottles has a bull's eye mark on the bottom
  • EBM bottles has a parting line across the bottom
  • Thermoforming has no marks