ROTATIONAL MOLDING
Larry Suba, Akro Plastics
LarryS@rotomold.net

Rotational molding is a highly versatile manufacturing option that allows for unlimited possibilities with the added benefit of low production costs.

PROCESS OVERVIEW

The rotational molding process starts with a good quality mold that is placed in a molding machine that has a loading, heating, and cooling area.

Several molds may be placed on the machine at the same time. Pre-measured plastic resin is loaded into each mold, and then the molds are moved into the oven where they are slowly rotated on both the vertical and horizontal axis. The melting resin sticks to the hot mold and coats every surface evenly. The mold continues to rotate during the cooling cycle so the parts retain an even wall thickness.

Once the parts are cooled, they are released from the mold. The rotational speed, heating and cooling times are all controlled throughout the process.

DESIGN ADVANTAGES

Rotational molding offers design advantages over other molding processes. With proper design, parts that are assembled from several pieces can be molded as one part, eliminating expensive fabrication costs.

The process also has a number of inherent design strengths, such as consistent wall thickness and strong outside corners that are virtually stress free. If additional strength is required, reinforcing ribs can be designed into the part. Rotational molding delivers the product the designer envisions. Designers can select the best material for their application, including materials that meet FDA requirements. Additives to help make the part weather resistant, flame retardant, or static free can be specified.

Inserts, threads, handles, minor undercuts, flat surfaces that eliminate draft angles ,or fine surface detail can all be part of the design. Designers also have the option of multi-wall molding that can be either hollow or foam filled.

COST ADVANTAGES

When cost is a factor, rotational molding has the advantage over other types of processes as well. In comparison to injection and blow molding, rotational molding can easily produce large and small parts in a cost effective manner. Tooling is less expensive because there's no internal core to manufacture. Since there is no internal core, minor changes can be easily made to an existing mold.

And because parts are formed with heat and rotation, rather than pressure, molds don't need to be engineered to withstand the high pressure of injection molding.

Production costs for product conversions are reduced because lightweight plastics replace heavier, often more costly materials. Which makes rotational molding as cost effective for one-of-a-kind prototypes as it is for large production runs. Rotational molding by virtue of its versatility is used to produce a wide range of products in an equally wide range of markets. Some typical market sectors and the applications within them include:

AGRICULTURE

Storage Tanks, Spraying Equipment Tanks, Brine Tanks, Wine presses Tanks, Livestock Equipment, and Livestock Shelters.

AUTOMOTIVE

Arm Rests, Motorcycle Fuel Tanks, Heavy-Duty Truck Beds, Duct Work, Air Intake Systems, Wheel Arches, Mud Flaps for Tanks, Instrument Panels and Consoles.

BUILDING/CONSTRUCTION

Water Tanks, Septic Tanks, Sewage Connecting Housings, Pipe Linings and Fittings, Pool, Spa and Hot-Tub Parts, Concrete Post Forms, Lighting Globes, Highway Barriers.

ELECTRICAL/ELECTRONIC

Above-Ground Pedestals, Below ground Chambers, Business Machine Enclosures, Speaker Enclosures, Cross-Arms For Utility Poles.

FLOOR CARE

Vacuum Cleaner Parts, Floor Cleaner Tanks.

INDUSTRY

Chemical Tanks, Laboratory Tanks and Sinks, Water Treatment Tanks, Cases, Shrouds, and Housings, Environmental Secondary Containment, Corrosion and Pollution Control Equipment Parts.

MARINE PRODUCTS

Dock Floats, Bumpers, Pontoons, Boat Parts (Wheels, Hulls, Fuel Tanks, Seating, Fenders, Live Wells), Storage Bins, Lifesaver Rings.

MATERIALS HANDLING

Tanks, Drums and Barrels, Hoppers, Intermodal Bulk Containers, Skids and Pallets, Chutes, Refuse Carts, Containers and Lids, Laundry Carts.

PLAYGROUND EQUIPMENT

Slides, Climbing Fences, Fast Food Outlet Play stations.

RECREATIONAL VEHICLES

Fuel Tanks, Water Tanks.

SIGNS AND DISPLAYS

Point of Purchase Displays, Newspaper Vending boxes.

SPORTS/RECREATION

Toys, Playballs, Kayaks and Canoes, Helmet Linings, Dolls, Ski Cases, Pet Products, Bowling Equipment, Equestrian Equipment, Park Benches.

TRANSPORTATION

Road Furniture, Road Traffic Barriers, Cones, Signage, Aircraft Duct Work.

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Akro-Plastics/Rotationally Molded Plastic Products provides design support, engineering, custom colors, molded-in parts and graphics (metal & plastic inserts, locking hinging), spin welding, post molded graphics, 5-axis CNC trimming, complete assembly, packaging. Metal castings.