Twin Sheet Forming

Posted by Ashwin.S at 5:20 AM

Twin sheet forming

Twin-sheet thermoforming is a process of vacuum or pressure forming two sheets of plastic essentially simultaneously, with a separate mold on the top and bottom platens. Once the plastic has been molded, it remains in the molds, and while still at its forming temperature the two molds are brought together under high pressures, and the two sheets are welded wherever the molds dictate a weld.

The process creates 3 dimensional parts with formed features on both sides. The parts are typically very strong, stiff, and quite light-weight.

Step 1: Two preheated thermoplastic sheets are simultaneously heated between the two molds till they are are entirely plasticized.

Step 2: On reaching the the specific temperature the two molds move together. The
two Sheets are deep-drawn and tightly molded to each other in one step. No
adhesives are used. There are neither resulting pressure nor strain.


Step 3: To achieve a high level of detail or precision, the forming can be supported by high pressure or (and) vacuum.


Step 4: ... and the hollow body, without solvent, molding additives and adhesives,
is finished. Furthermore, there are no inner strains.

Materials

  • H.M.W. HD Polyethylene
  • ABS
  • PC/ABS
  • Polycarbonate

Typical applications are:

pallets, industrial dunnage, portable toilets, medical housings, surfboards, fuel tanks, air/ventilation ducts, electrical enclosures, recreational boats, cases, toys, marine products, doors, tables, spine boards and numerous transportation-related products.

Main Advantages

  • Increased Structural Integrity and Rigidity
  • Enclosed Cross-Section Capability
  • Low Tooling Cost
  • Internal Reinforcement Options: Structural Member, Rigid Foam, Etc.
  • The process has some distinct advantages over blow-molding and rotomolding.

The process has some distinct advantages over blow-molding and rotomolding.

Compared to blow-molding, the twin-sheet process:

  • Tooling and machines are more cost-competitive for small to modest run sizes.
  • Each sheet may be a different thickness, material or color.
  • More flexibility with parting line structure is possible.

Compared to Rotomolding, the twin-sheet process:

  • Many more resin types are available in twin-sheeting.
  • More structural beams can be created in twin-sheeting
  • Much higher production rates

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