Rotational Moulding: Basic process
- The rotational moulding process :
1.1.An amount of plastic powder is deposited inside the mould.
1.2.The mould is then closed.
1.3.The mould rotates bi-axially inside the oven.
1.4.The plastic begins to melt and forms a layer over the inside surface of the mould.
1.5.With the oven cycle over the mould is removed and the cooling process begins.
1.6.The mold is opened and the hollow article is removed.
- Where we can use the rotational moulding process:
- Agriculture:Vegetable growing trays, feeding/watering troughs, chemical tanks.
- Consumer products:Baby strollers, child car seats.
- Containers:Storage tanks, 55 gallon tanks, carboys, septic tanks.
- Furniture:Children’s beds, chairs, planter pots, tables.
- Industrial equipment:Tool carts, equipment housings, safety helmets, battery containers, fluid reservoirs.
- Lawn/garden:Garden tool carts, composting bins.
- Marine:Boats, kayaks. Sailboards, canoes, boat bumpers.
- Medical:Syringes, dental chairs, testing equipment, anesthesia/oxygen masks, ear syringes, squeeze bulbs.
- Materials handling:Stackable pallets, forklift containers, shipping containers.
- Road/highway:Safety barricades, lane markers, litter bins, portable toilets.
- Sporting equipment:Bike seats, athletic pads, footballs, juggling pins, helmets.
- Toys:Playhouses, outdoor gym equipment, balls, rocking horses, picnic tables, wading pools, pool floatables, doll parts.
- Transportation:Camper tops, motorcycle saddlebags, bicycle trailers, tool chests for trucks, truck bed liners, air ducts, fuel tanks, seat back head restraint covers.
- What are the main advantages of rotational moulding are:
Rotational molding offers design advantages over other molding processes. With proper design, parts assembled from several pieces can be molded as one part, eliminating high fabrication costs. The process also has inherent design strengths, such as consistent wall thickness and strong outside corners that are virtually stress free. For additional strength, reinforcing ribs can be designed into the part. Along with being designed into the part, they can be added to the mold.
The ability to add prefinished pieces to the mold alone is a large advantage. Metal threads, internal pipes and structures, and even different colored plastics can all be added to the mold prior to the addition of plastic pellets. However, care must be taken to ensure that minimal shrinkage while cooling will not damage the part. This shrinking allows for mild undercuts and negates the need for ejection mechanisms (in most pieces).
In some cases rotational molding can be used as a feasible alternative toblow molding, this is due to the similarity in product outputs, with products such as plastic bottles and cylindrical containers, this is only effective on a smaller scale as it much more costly to blow mold regarding a small output, and with fewer resulting products rotational molding is much cheaper, due to blow molding relying on economies of scale regarding efficiency.
Another advantage lies in the molds themselves. Since they require less tooling, they can be manufactured and put into production much more quickly than other molding processes. This is especially true for complex parts, which may require large amounts of tooling for other molding processes. Rotational molding is also the desired process for short runs and rush deliveries. The molds can be swapped quickly or different colors can be used without purging the mold. With other processes, purging may be required to swap colors.
Due to the uniform thicknesses achieved, large stretched sections are nonexistent, which makes large thin panels possible (although warping may occur). Also, there is little flow of plastic (stretching) but rather a placing of the material within the part. These thin walls also limit cost and production time.
Another cost limiting factor is the amount of material wasted in production. There are no sprues or runners (as in injection molding), no off-cuts (thermoforming), or pinch off scrap (blow molding). What material is wasted, through scrap or failed part testing, can usually be recycled.
From Wikipedia
- What material we use
L.L.D.PE