Question: I’m looking for information to go along with the Test Method for Particle Size of Rotational Molding Powders. What type of shaker do you need to use? Is it acceptable to shake the screens manually?
Dr. Nick: In North America, the “Rotap” system is normally used. This imparts a horizontal swirling motion, with a heavy up-and-down tap at the same time.
In other parts of the world, a vibratory motion is used. Whilst there might be some minor difference in the results, both are acceptable technically.
I run my Rotap for a standard run time of 15 minutes (there is a timer to facilitate this). Most of the pulverizer suppliers will sell you this equipment.
Be advised: the Rotap is a noisy piece of equipment! If you run it in close proximity to co-workers (eg in a lab), you may want to have it in a sound-proof box.
I wouldn’t advise manual shaking. Apart from sounding like an exhausting workout, you would struggle to maintain consistency.
Dr. Nick Henwood serves as the Technical Director for the Association of Rotational Molders. He has 30+ years experience in rotomolding, specializing in the fields of materials development and process control. In 2022 he was inducted in the Rotational Molding Hall of Fame. He operates as a consultant, researcher and educator through his own company, Rotomotive Limited, based in UK.
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