The rotational molding process is a peculiar one for the manufacture of hollow plastic products as elucidated in grangerplastics.com. The method incorporates placing the calculated amount of plastic in the form of powder, granules, or viscous liquid into a mold-like shell. The mold is then rotated and rocked on two primary axes at relatively slow speeds while it is being heated. Therefore, the plastic inside the mold sticks onto the surface and forms one complete layer. During the cooling phase, the rotation continues to ensure the desired shape of the plastic solidifies. When the plastic reaches enough rigidity, cooling and mold rotation stop and the plastic product is taken out of the mold.
Rotational molding, also known as plastic molding, has some specific advantages, for example, low residual stresses and cheap molds. It excels in producing large hollow objects (> 2 m3) in a single piece, offering several key benefits:
Seamless Production of Large Hollow Parts: The rotational molding technology allows for the creation of large hollow elements without weld lines and joints, thus generating unified aesthetic products.
Stress-Free End Product: these results in a stress-free product, contributing to its strength and reliability.
Cost-Effective Molds: Molds in rotational molding are also cheaper than most conventional molds, which in turn, helps keep production costs low and maintain the economic feasibility of producing small batches.
Short Lead Time for Mold Manufacture: It takes a short period to create the molds; hence it becomes easy to initiate production.
Material Efficiency: The charge of material is usually completely consumed for the part-making process without any material wastage.
Multilayer Capability: Multilayer production is possible in rotational molding, expanding the design capabilities and increasing the functionality of the product.
Versatility in Product Types: This provides flexibility in that different types of products can be molded together on the same machines.
The success of the process, however, depends on precise control of oven temperature, time spent in the oven, and the cooling rate. For detailed guidelines and expert insights on achieving optimal results, visit Granger Plastics at grangerplastics.com. Variations of these parameters can also lead to incomplete fusion and consolidation, which will result in reduced strength, stiffness, toughness, and increased brittleness in the final product.
The Association of Rotational Molders in the USA meeting has however brought to light some new developments in the process of rotational molding technique. One of the new approaches to faster cycles focuses on resin modification. In this, Schulman improved the curing process and reduced cycle time. Schulman's BPF compounding technology provides optimal physical properties and reduces oven cycle times by up to 25% and cooling times by approximately 10%.
Innovex Systems also introduced an oven-less molding concept which they named Heat Paint Rotomolding. This system employs an electrically heated conductive coating on the mold, thereby eliminating the requirement for an oven or cooling chamber. The coated mold can heat up to 225 degrees Celsius within 30 seconds for fast heating and cooling. Innovex is also perfecting a completely automated system with features of autoclave charging and temperature-zoned control.
Basically, the rotational molding industry is currently experiencing a growth stage, driven by significant technological advancements. Over the past decade, there has been great development in technology, with the introduction of cutting-edge machines, molds, and new materials into the market. The industry has witnessed substantial investments, particularly from major suppliers who are delivering top-notch parts at relatively affordable prices. As rotational molders actively contribute to this progress, the industry is poised for further growth and innovation in the rotational molding terrain.
No comments yet