Rotomoulding: unleash your creativity

There is a new respect for Rotational Moulding and ARM would like to help you explore the possibilities for your next project.

ROTOMOULDING

Amazing products are made using modern rotomoulding techniques.

Increasingly businesses in a wide range of industrial sectors are turning to rotomoulding to produce their existing plastic products or converting their existing products made in the traditional methods and materials. Rotomoulding is often a much more cost effective and flexible process and is very easy to explore as an option due to its cheap development costs and suitability for small to medium sized batch runs.

What is Rotational Moulding?

Rotational moulding, more commonly known as rotomoulding, is an extremely versatile process for the manufacture of a vast range of plastic products and components. Advances in oven technology, mould making techniques and the raw materials available have increased its use substantially. 

Rotational moulding is a method for manufacturing hollow plastic products by pouring polyethylene pellets into a metal mould and rotating it in an oven to coat the inside surfaces of the mould. The end result of rotomoulding is extremely strong, long lasting, and durable parts. 

The Rotomoulding Process

Stage 1: 
Based on the size of the mould and final thickness of the walls required, a specific amount of plastic powder granules or liquid, is poured into a hollow metal mould, consisting of two or more pieces.
 
Stage 2: 
The mould is introduced into a preheated oven and rotated about two principal axes for a set time, ensuring the plastic is fully melted and flows to all the corners sufficiently and adheres to all the inner surfaces of mould.
 
Stage 3: 
The mould is removed from the oven, after the allocated time, with the axle rotation continuing as the mould is cooled by large fans. This phase ensures the item retains its desired shape and wall integrity.
 
Stage 4: 
Once the plastic has cooled sufficiently the rotation is stopped to allow the removal of the rotomoulded plastic product from the mold. In some situations the product might be placed in a cooling frame to maintain it shape until fully cold and rigidly formed

ARMA: Association of Rotational Moulding Australasia

Features of Rotational Molding

The rotational moulding process has some specific attractions over other traditional and plastic manufacturing methods including:
  • Very large products can be made cost effectively
  • Hollow parts can be made in one piece with no weld lines or joints.
  • The rotomoulded part is essentially stress-free.
  • The moulds are relatively inexpensive compared with other mould types
  • There is a relatively short lead time for the manufacturer of moulds 
  • Wall thickness can be quite uniform due to the low pressure manufacturing method
  • Wall thickness distribution can be altered with no mould modifying required
  • Economically short production runs are viable
  • Material waste is none existent as the full weighed plastic charge is used every time.
  • Multi-layer molded parts and products are possible 
  • Hollow parts can be foamed for additional rigidity or buoyancy.
  • Different types of products can be molded together on the one machine
  • Metal inserts can be moulded in for additional structural integrity
  • High quality damage resistant graphics can be molded in

Rotational Moulding Product Benefits

In addition to the manufacturing benefits of the manufacturing method the end attributes of the rotomoulded products also show specific benefits over other manufacturing techniques including:

  • Aesthetically pleasing
  • Naturally Buoyant
  • Complex Shapes
  • All weather resistance
  • Chemical resistance
  • Child safe (non toxic)
  • Comfortable to handle (hot and cold)
  • Consistent wall thickness
  • Corrosion proof
  • Durability
  • Easy repair
  • Eco-friendly
  • Economical
  • Flexible material
  • Food safe
  • Good load bearing properties
  • High impact resistance
  • Leak-proof reliability
  • Light
  • Longevity
  • Low maintenance
  • One-part construction (no seams)
  • Potable water safe
  • Recyclable
  • Stress-free products
  • Superior strength
  • Temperature stable
  • Thick walls
  • UV Stable
  • Add weight (water/concrete)?

Rotational Molding Applications

Over recent decades new types of machines and quite a number of significant technical advances have been made with moulds  and materials. Making the rotational moulding method available and attractive to designers, engineers and new market sectors including highly technical industries requiring high-performance parts such as the aircraft industry.

The Versatility of rotomoulding

Rotational Molding Material Options

Polyethylene comes in many forms and is used for the vast majority of rotomoulded products. There are other materials available however depending on the specific requirements of the end product. Those other materials for rotomoulding include:

  • Polycarbonate
  • Nylon
  • Polypropylene
  • Unsaturated polyesters
  • ABS
  • Acrylics
  • Cellulosics
  • Epoxies, 
  • Fluorocarbons
  • Phenolics, 
  • Polybutylenes
  • Polystyrenes, 
  • Polyurethanes
  • Silicones 

Rotational Mold Design

The design of the mould is an important part of ensuring a successful rotomoulded product. 

Knowing exactly how a mould will react to the heat is crucial to ensure the end product will perform as intended, taking advantage of the specific benefits of the rotational moulding process. 

Understanding that different rotational moulding materials have unique flow properties and processing requirements can mean the difference between success and failure. 

During the rotational moulding design process various details need to be considered including:

  • Nominal wall thickness requirement
  • Wall thickness uniformity
  • Varying wall thickness
  • Flatness considerations
  • Minimum wall separation
  • Corner angle limits
  • Reinforcing ribs
  • Kiss-off ribbing
  • Draft angles
  • Corner Radiuses 
  • Undercuts
  • Tolerances

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Is Rotomoulding right for you?

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