Forming - Twin-sheet Thermoforming

Back to main Forming page

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.

Typical applications are industrial dunnage and portable restrooms, utilizing the olefin family of materials.

ATI has been stretching the limits of this process employing techniques we call Technical Twin-Sheet® which employs a much wider range of materials, including TPU, Polycarbonate and the FR ABS family of plastics and meets significantly higher tolerances in trim and molding. Moreover, we have developed the tooling and knowledge to hide the parting line to allow us to produce very cosmetic parts. We can employ different materials on either side of the part as well as different colors. Insert molding of hardware is also possible.

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