Rotomolding - Complex Shapes and Large Parts
What is rotational molding (or rotomolding)
Rotational molding is a process allowing the creation of large or small seamless hollow plastic parts. The manufacturing process begins with a mold mounted on the machine arm and loaded or charged with a pre-measured amount of powdered resin into the mold cavity. While the rotomold moves in a biaxial rotation and is heated to a specific temperature, fusion starts to take place, forming the desired shape of the part.
Rotational Molding Manufacturing Process
Step 1 The rotomolding process is begun by placing a pre-measured amount of plastic material in a cavity. The rotomold is then closed and clamped and moved into an oven where it and its contents are brought up to the fusion temperature. As the mold is heated, it is rotated continuously on vertical and horizontal axes. This biaxial rotation brings all surfaces of the mold in contact with the plastic material.
Step 2 The mold is rotated within the oven until all the plastic material has been picked up by the hot inside surfaces of the cavity and creates a uniform layer, rotationally molded component.
Step 3 While continuing the rotation, the machine moves the mold out of the oven and into the cooling chamber. Air cools the mold and the layers of molten plastic material.
Step 4 The rotomolding machine then moves the mold to the loading and unloading station. The mold is opened and the part removed. A new pre-measured load of material is then placed in the cavity, the mold is closed and the process is repeated.
Step 5 Rotomolded parts are then trimmed, finished and packed ready for market or secondary assembly.
Why choose Rotational Molding
Rotational molding offers the most design flexibility, cost saving and the ability to produce both complex and simple large or small parts versus other plastic manufacturing processes. With proper design, parts that are assembled from several pieces can be molded as one part thus eliminating expensive fabrication and related costs.
A great advantage of rotational molding to consider is the relatively inexpensive tooling costs in comparison to other molding methods. A low initial investment provides an entry point for lower volume production with much faster to market timing. Diversity of products and overall production cost in rotational molding are positive factors which help facilitate many exciting and innovative products.
Design Flexibility in Rotational Molding
- Allows for complex geometry
- Finite element analysis FEA to is used to provide a risk assessment and design Verification to avoid part failure
- Solid works software provides finished 3-D part drawings and CAD drawings
- Capable of digitizing and reverse engineering
Cost Savings in Rotational Molding
- Molds cost less then other molding methods
- Less per part price than metal or fiberglass
- Faster to market from design → tooling → first part, taking advantage of immediate market opportunities
- Individual part manufacturing allows quality checks facilitating part matching specifications
Production Flexibility in Rotational Molding:
- Unlike other molding processes rotational molding produces stress free parts
- Provides the ability to have very fine surface detail such as texturing
- Additional parts can be added at time of molding like inserts or spun in fittings
- Large or small production runs
- Ability to alter wall thickness by adjusting part charge weight
- Color changes
- Stone effect / granite materials
Advantages & Benefits of Rotational Molding
- Design flexibility to meet specifications
- One-piece seamless construction
- Metal inserts and fittings as integral parts
- Excellent load-bearing properties
- U.V. resistance
- Molded-in graphics, such as logos, and embossing
- Uniform wall thickness
- Resistance to corrosion
- Ribs and cones for stiffening
- Variety of colors including proprietary stone effects and metallic colors
- Variety of textures and finishes
- Lightweight
- Product longevity/durability
- Consistent wall thickness
- Single wall or double wall for strength
Industries Served Through Rotational Molding
Site Furnishing - from benches and chairs to planters and tables
Waste & Recycling - receptacles to multi stream recycle units
Material Handling - bins, hoppers, pallets, storage containers, salt and sand bins, document destruction.
Marine - water tanks, fuel tanks, boat parts, buoys,
Lawn & Garden - rain barrels, composters, storage bins, carts and wheel barrows
Recreational - playground, games, water sports
Safety - road barriers, pylons, salt and sand bins, spill pallets, hazardous waste containment
Point of Purchase Displays - kiosks, displays, signage, merchandising accessories
Pool & Spa - hot tubs, pool steps, backyard pools,
Military Equipment - vehicle components, protective personal equipment
Agriculture - livestock feeders, bushel carts, auger covers,
Truck & Automotive - Fenders, bumpers, shields interior ventilation
Food Service - Carts, trolleys, food centers
Medical - storage bins, trays
Children Toys - wagons, small trucks, toboggans
Original Equipment Manufacture
Building & Construction
What our customers have to say:
"This was our first project with Shirlon Plastics and it was a success! We would definitely choose you again for our rotational moulding projects!"