Thermoforming plastic services have been provided by the Gregstrom Corporation since 1946. In addition to world class molding and forming, we offer complete assembly, testing, packaging, inventory management, and direct shipment both domestically and internationally.

At Gregstrom Corporation we provide the full range of thermoforming processes to meet the most demanding applications. These processes include: Vacuum Forming, Pressure Forming, and Twin Sheet Forming.

What is Thermoforming?

Thermoforming plastic is a manufacturing process where a plastic sheet is heated in an oven to a high-enough temperature that it can be stretched into or onto a mold and cooled to a finished shape. Thermoforming offers significantly lower tooling costs and lead times than injection molding and other processes. It is cost effective for both short runs and medium volume production.

Thermoforming Processes:

Vacuum Forming – a plastic sheet is clamped and heated. A vacuum beneath the sheet causes the atmospheric pressure to push the sheet down into the female mold.

Pressure Forming – through the use of positive pressure in addition to the atmospheric pressure used in vacuum forming, much sharper definition and tighter corner radii can be achieved. The need for costly painting is often eliminated by using a textured mold.

Twin Sheet Forming – two heated sheets are clamped in a rotary or in-line shuttle machine. Then the upper and lower sheets are vacuum drawn into top and bottom female molds. The molds are subsequently brought together, and the hot sheets are compressed at joining areas designed into the mold. The two sheets are thus thermally welded into a single part without use of adhesives or fasteners. This process is used for three dimensional, hollow parts with detail on both sides that are structurally strong and lightweight. For extra rigidity, twin sheet parts can be filled with rigid foam or have inserts placed in the part during forming. Dissimilar materials, colors and thicknesses are possible on the same part.

Forming Techniques:

Drape Forming – the plastic sheet is clamped and heated, then drawn over the mold. When the mold has been forced into the sheet and a seal created, vacuum beneath the mold forces the sheet over the male mold.

Plug Assist Forming – After the sheet is clamped and heated, it is sealed across the mold cavity. A plug shaped similar to the mold cavity contacts the sheet causing it to stretch as it is carried into the cavity. Vacuum is then applied to transfer the sheet from the plug surface to the mold surface.

Vacuum Snapback – after the sheet is clamped and heated, it is sealed over the female draw box. A vacuum is applied at the bottom of the draw box pulling the plastic sheet into a concave shape. When the sheet is fully pre-stretched, the male mold enters the sheet and a vacuum is applied through the mold, pulling the sheet to the mold surface.

Billow Forming – similar to vacuum snapback except the heated sheet is blown upward into a bubble shape and then the plug or mold is driven into the pre-stretched sheet from the top plate.

Our Thermoforming services and other services have produced these and other fine products for our clients:

• Rotationally Molded Ventilation Ducts
• Rotationally Molded Chemical Feeder Assemblies
• Rotationally Molded Shopping Cart Accessories
• Rotationally Molded Manifolds
• Pressure Formed Instrument Housing Assemblies
• Rotationally Molded Chemical Feeders
• Rotationally Molded Tanks
• Rotationally Molded Bins & Pallets
• Rotationally Molded Mufflers
• Pressure Formed Instrument Housings
• Rotationally Molded POP Assemblies
• Vacuum Formed Medical Instrument Cases
• Pressure Formed Medical Laser Assemblies
• Pressure Formed Printer Assemblies

• Twin Sheet Thermoformed Instrument Housings
• Rotationally Molded Boats
• Pressure Formed Instrument Housings
• Rotationally Molded Spine Boards
• Rotationally Molded Coffee POP Display
• Vacuum Formed Medical Instrument Cases & Covers
• Vacuum Formed Taxi Tops
• Rotationally Molded Baby Changing Stations
• Rotationally Molded Lawn/Garden Equipment Housings
• Rotationally Molded Shopping Cart Accessories
• Pressure Formed Digital Taxi Media Display Assemblies
• Rotationally Molded Powder Chemical Dispensers
• Rotationally Molded 3-D Printer Housings