Rotational molding, also known as rotomolding, produces seamless hollow parts in complex or intricate shapes in virtually any size. Structurally, rotomolded parts are good load bearers and the process easily accommodates molded-in stiffeners when additional strength is needed. Most plastics for rotomolding are special formulations of either thermoplastic and thermoset resins. They feature good thermal stability and narrow molecularweight distributions for the best physical properties. With correct resin selection, rotomolded parts can economically replace fiberglass, metal, and wood.
Rotomolding provides lots of design options and produces stress-free parts with no mold lines or sprue and ejection marks. Recent winners in the Association of Rotational Molders (ARM) International, Oak Brook, Ill., design competition illustrate why this often-underutilized molding process can make sense.
The Boatin' Bud, a tackle-storage system for aluminum boats, rotomolded by M.B.C. RotoMould Inc., Newmarket, Ont., topped the list for Innovative State of the Art. Entries here demonstrate significant departures from established rotomolding practice, displaying both craftsmanship and quality. In production since 2000, this rotomolded storage system features a rod, net, and beverage holder as well as tackle compartments and a personal-storage area. It mounts on the side of 14 to 16-ft runabout aluminum boats.
Bonar Plastics Inc., Ridgefield, Wash., walked away with two accolades. The first, in the Conversion category, was the redesign of the Gen-Eye Junior. The portable video-inspection device is made from a four-piece rotomolded assembly. Rotomolding let the OEM reduce overall footprint and weight. The rotomolded design is also more durable and less prone to damage than its predecessor. The battery-powered device comes with 200 ft of cable, an LED display, and camera. Products in this category had to be converted to rotationalmolding from some other material-or process.
Bonar Plastics's second prize was for The Polar Box 57 which took Large Product honors. Products in this category must have at least one 72-in.-long dimension. The double-walled, foam-filled container for food distribution is a redesign of a previous model. Improvements were made after feedback from customers and production personnel. The unit is designed for refrigeration/frozen-food distribution in nonrefrigerated trucks. Because the product is used in a harsh frozen environment and is in contact with 120°F dry ice, it was designed to withstand impacts at these extreme temperatures.
The second Product of the Year winner a 12 X 12 X 15-in. sandblast housing unit molded by Formed Plastics Inc., Carle Place, N.Y. also captured top honors in the Recycled category. The housing was converted from sheet metal to rotational molded polyethylene (PE). The key factor that led the OEM to rotomold the housing was the economics gleaned from the use 100% black reprocessed PE.
A Johnson Diversey Cleaning Cart used in chain stores was a cowinner of the top 2005 Product of the Year honor. In production since February 2005, the
Johnson Diversey Cleaning Cart was molded by Dutchland Plastics Corp., Oostburg, Wis., using both rotational and blow molding. The robust cleaning cart is produced in a sixpiece mold. The individual pockets are designed specifically for Johnson Diversey products and container sizes. Dutchland Plastics was able flow the material into the front and rear handles. This let them eliminate the need for extruded tubes that would have served as handles. Dutchland Plastics purchased and then assembled all components used to build the carts.
The Travelocity Roaming Gnome also rotomolded by Dutchland Plastics was the top PVC entry. The gnome is a new advertising piece for Travelocity. It was rotomolded with rigid PVC, then filled with urethane foam and hand decorated. The production for this piece began in Spring 2005 with an initial run of 100 units.
ARM International, (630) 571-0611, rotomolding.org
Bonar Plastics Inc., (800) 972-5252, bonarplastics.com
Dutchland Plastics Corp. (920) 564-2356, dutchlandplastics.com
Formed Plastics Inc. (516) 334-2300, formedplastics.com
M.B.C. RotoMould Inc., (905) 836-0210 mbcrotomould.com