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Ask Dr. Nick: Are There Guidelines for Vent Sizes?
During a recent “What’s Your Problem?” session, we were asked whether any guidelines existed relating to the sizing vents for rotomolding tools. This subject is covered in the ARM webinar series on “Operator Training.” I have reproduced the most relevant slides below: The first slide shows a “rule of thumb” that has been cited by…
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Ask Dr. Nick: What issues should I expect with mold pressurization?
Question: We have a question about molding with pressure inside the mold. We have rock & roll machine making medium sized parts. We have been experiencing significant warpage, especially on flat surfaces and it has been suggested that we should apply air pressure inside the mold, to improve our parts. Please could you provide some…
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Two New Videos on Air Amplifiers
Over the last few months the ARM Process and Optimization Committee has been been discussing with one another the best methods for using air amplifiers in the rotational molding process. As a result, two companies have created videos to share with ARM members. These videos represent suggestions from individual molders. Each molder will need to…
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Ask Dr. Nick: Particle Size Test Method Specifics
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…
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Ask Dr. Nick: Shrink Rate Data
Q: Do you have any data for shrink rates over time, for roto based products? Dr. Nick: Interesting question. Nothing immediately sprang to mind, in terms of a prior published reference. But… Clearly, shrink rates will be governed by the development of crystallinity within the PE. So I looked for data concerning the development of…
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Advanced Rotomolding Seminar
ARM Technical Director Nick Henwood will host an Advanced Rotomolding seminar at the ARM Annual Meeting in Kansas City on September 26, 2023 from 8 AM to 4:00 PM. This seminar will cover how melt index and density relate to romotolding, alternatives to PE, how to use data sheets, thickness control, correct cure, how cooling…
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Don’t Forget Your Venting
Last year I wrote a blog for ARM that pointed out the importance of adequate venting and the bad consequences of not ensuring that your venting for each tool is adequate. This is VITAL to making a quality part. While I’m sure that many of you are fully aware of this subject, I still get…
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ARM Webinar: Environmental Regulations
Martin Coles, Matrix Polymers, will provide an overview of environmental regulations on the horizon that are likely to affect the roto industry during a free webinar for members January 18 at 10 Central. There is a proposal to ban all new installations of gas in New Zealand, new taxes in Europe on all plastics packaging made…
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Temperature Conditioning for ARM Impact Testing
(and a few other practical tips) Minus 40º (actually the same number in ºF or ºC) is specified as the conditioning temperature prior to drop dart testing, according to the ARM protocol (“Low Temperature Impact Test”, Version 4.0, July 2003). This relatively low temperature has been chosen because it provides a better differentiation between different polyethylene grades and…
