24 Rotary thermoforming.

The development of the rotary machine in the mid-1950s significantly increased production capabilities for U.S. thermoformers. The process, developed by Brown Machine and Comet (later Maac Machinery), expanded the use of thermoforming and made it more competitive and cost-effective for higher volume industrial applications.

Until then, single-station shuttle systems were the dominant cut-sheet forming process. In 1955, Brown launched the R223 model, a three-station rotary former with two platens and two heaters. High production rates resulted because heating, forming, and load/unload functions were being performed simultaneously.

One of the first applications developed in 1955 were refrigerator inner door panels made of ABS or PS. Other early applications included appliance housings and evaporator pans for refrigerators. So-called "substrate forming," in which foam-backed vinyl was thermoformed over wood particle board, was used extensively for auto inner door panels and interior trim.

Later, machine makers offered four-station rotary units with a second heating station, which facilitated twin-sheet thermoforming. Key high-volume twin-sheet applications included shoe soles and structural parts such as truck-cab floors and interior trim. Business grew rapidly in appliance, automotive, material handling, and toys. The market exploded by the early 1970s, as evidenced by Brown's sale of 48 rotary machines in 1971.

Today, rotary technology is almost mandatory for heavy-gauge (1/8-in. and up) thermoforming operations. While it brings big productivity advantages, rotary technology is not as versatile or flexible as shuttles since set-up and changeovers are more difficult.