Rotary blowmolding is not a new process. In fact, rotary blowmolding was in use by the mid-1960s for volume production of household product bottles, notably bleach bottles, said Wilmington Machinery, a company that was founded with the mission of developing and building plastics processing machines. Based in Wilmington, NC, and operating in a 65,000-square-foot facility, the company has developed machinery for foamed extrusion blowmolded packaging and foamed industrial blowmolding.
While Wilmington Machinery notes that the company did not invent rotary blowmolding (aka “wheels”), beginning in 1979 it sought to “perfect it.” The optimal features of “wheels” have been retained in Wilmington’s latest Series III B rotary blowmolding machine, notably simultaneously opposed clamping actuation, the most desirable feature for high-quality bottle making. The Series III B comes in four tonnage sizes configured for the specifications of the bottle and quantities.
Like its Series III predecessor, the Series III B is available with nine to 36 molding stations (clamps) rotating in a circular pattern at speeds up to 10 RPM, resulting in the production of 45 to 720 bottles per minute. The extrusion unit can incorporate one to seven extruders depending on bottle layer requirements. Die heads include single layer, three-layer and up to seven layers for both single and dual parison molding.
Construction of the new rotary blowmolding unit starts with a more robust modular clamping station with air and water services directly pre-plumbed to clamp platens, significantly reducing setup and maintenance times.
The new wheel has dual-cam clamp actuation, which significantly reduces wear on clamp components and allows for independent open/close control of each mold half. This feature is especially useful in ejection and placement of the bottle at the discharge point of the wheel. The new wheel retains the radial positioning (or variable pitch) feature that Wilmington pioneered in the 1980s. One change is the unique spoke-mounting arrangement of the clamps to the axle, enabling faster setups, improved mold coolant flow and reduced cycle times.
The new wheel also incorporates a servo drive for the clamps, ensuring a high level of consistency during station-to-station clamp opening and closing. The servo-drive system is programmed to index the wheel exactly one station for setup purposes. Additionally, Wilmington’s automatic clamp open and close feature simplifies mold setup.
Wilmington Machinery also builds the SB series of rotary blowmolding machines for high-volume production of single-serve energy, nutritional, juice and dairy products. These machines typically produce from 14,000 to 72,000 bottles per hour and have most of the features of the new Series III B machines.