Everything ARM did in Q1 2022

  • Premiered three safety webinars on energy, machinery, and hand tools.
  • Translated our operator training webinar on measurement into Spanish.
  • Presented a short video on removing parts with injector pins.
  • Shared What’s New in 2022 from our rotomolding suppliers.
  • Presented our Intro to Roto seminar in California and sold out our Minnesota meeting. We’ll be in Utah June 10 and Illinois in July 15.
  • Discussed how Prop 65 is affecting rotomolders.
  • Published five quick fixes for reducing your gas usage.
  • Hosted our What’s Your Problem? troubleshooting discussion on Zoom.
  • Welcomed new members: S.R.SmithRotogalVita Plast CyprusXcelerant Growth Partners.
  • Learned what’s new in the third edition of Practical Rotational Molding.
  • Met with 85 registrants at our first Executive Forum since 2019!
  • Plus our Board and committees are working hard behind the scenes to continue to provide value to our members.

In 2022, bring your operators to Intro to Rotomolding

Dru Laws hosts an Introduction to Rotational Molding seminar in Ogden, Utah on June 10 (register) or Arlington Heights, IL on July 15 (register). We’ll update the posts when more dates are confirmed.

The seminar covers the key elements of the rotomolding process. This includes available materials, the main types of equipment used, processing parameters, process control methods to optimize part properties and key design guidelines. Attendees will have plenty of opportunities to ask questions and explore areas of particular interest.

Course Outline

Molding Cycle Overview & Temperature Profile

  • Heating and Cooling
  • Particle Shape and Size
  • Venting and Pressure
  • Rotation Speeds and Ratios
  • Static and Humidity
  • Other variables

Basic Quality Testing

  • Pre-Process Testing
  • Post-Process Testing

Wall thickness

  • Simulated Data
  • Test Data
  • Comparing to Other Processes
  • Skin Mapping
  • Design Considerations

Impact testing

  • Definitions
  • Layer Evolution
  • Impact Maturation


  • When it occurs.
  • Where it happens.
  • Why it matters.

What Happens in the Oven

  • Oven Heating Types
  • Oven Shapes
  • Anatomy of an Oven
  • Dissecting the Temperature Profile
  • Rotation Reversal

Process Control

  • What can it do?
  • What could we all be doing?
  • Why do you care?

The Rule of Three

  • Basic Machine Layout
  • Temperature Profile in the Oven Station
  • Temperature Profile in the Cooling Station
  • The Basic Steps in the Service Station
  • Powder-to-Part Density Reduction
  • Energy Consumed by the Polyethylene
  • Simple Quality Confirmations

Dru Laws

Dru Laws has shared his experience and expertise with other rotomolders endlessly through his involvement with ARM. He has frequently organized and spoken at rotomolding conferences large and small. He has presented at multiple international conferences. For many years he has presented ARM’s Introduction to Rotomolding seminar which is an entry into rotomolding for many members. When the Association needs a volunteer, he is often the first to say yes.

Laws is ARM’s immediate Past President. He has chaired Committees and written ARM’s Rotational Molding Foam Process Guide. He graduated with distinction from the Queens University of Belfast in Northern Ireland with an MSc in Polymer Engineering, emphasizing in Rotational Foam Molding. He began his experience in rotational molding at Mity-Lite and is now an executive at Tango Manufacturing.

Five quick fixes to reduce your gas usage

Dr. Nick Henwood – ARM Technical Director

In a previous Blog, I talked about the possibility of a gas-free future for rotomolders.   Since then, we’ve witnessed the situation in Ukraine, which has added to the pressures on natural gas supply in many European countries.  Even if you are based in a country with a secure gas supply, it’s highly likely that your unit cost of gas (natural or LNG) will be rising.  The supply of oil and gas is a global business.

Conventional rotomolding, using gas ovens, is not an economical process, as far as energy utilization is concerned.  Rising gas prices will create an extra headache that rotomolders could certainly do without.

There are a number of far-reaching strategies that rotomoulders can apply, to build a more energy-secure future.  However, these don’t help much in the short term.

Is there anything helpful that you can do immediately?

YES!  Here are 5 “quick fixes” that could help.

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What’s new in the third edition of Practical Guide to Rotational Moulding?

Mark P. Kearn

It’s been almost 20 years since Professor Roy Crawford and I published our Practical Guide to Rotational Moulding book. Developed and based around Queen’s University’s popular ‘Hands-On Rotational Moulding Seminars’, a second updated version was published in 2012.

A third, revised and updated edition has just been published (by Elsevier). It continues to be very encouraging to see the way in which first two editions of this book have proved popular with readers throughout the world. The practical approach, with the extensive use of photographs to illustrate key points, has enabled a wide range of people to get access to simple and advanced technologies available within the rotational moulding industry today.

Since the publication of the first edition of this book, it has been very pleasing to note the continuing evolution of the industry worldwide. New market sectors continue to be developed, new types of products have emerged, and new and improved technologies and materials have become available to ensure better quality products can be offered to customers.

This third edition provides a step-by-step approach to rotomoulding, covering applications, moulds, machinery, materials, and design. The edition has been thoroughly revised to include the latest advances, including novel materials and moulds, new products, and automation.

The book begins with a chapter that introduces the rotational moulding process, analyses advantages and disadvantages, and explores common applications for rotomoulded products. The subsequent chapters provide detailed, methodical coverage of moulds, machinery, materials, and design for functionality, supported by clear illustrations and diagrams. Finally, challenges and future developments are discussed.

This hands-on technical guide helps engineers, designers and practitioners to understand all aspects of rotomoulding, with the aim of producing performant end products and parts, with uniform wall thickness and potentially in complex shapes. The book is also of great interest to professionals across the plastics industry, as well as researchers and advanced students in plastics engineering, industrial design, mechanical engineering, chemical engineering, and materials science and engineering.

I have also looked into the crystal ball again to predict some of the developments that will become available in the future – for example, greater levels of automation, increased use of robotics, etc.  I am very grateful to people throughout the global rotomoulding industry who have had input to this third edition – by providing advice, photographs, data and encouragement. I hope that the third edition will continue to be useful to those who are new to rotomoulding, as well as those experienced in the industry and are striving to push back the boundaries of this extremely versatile manufacturing technology.

Lastly, I would like to thank the family of Prof. Roy Crawford for the opportunity, within this publication, to continue his legacy of education in rotational moulding. The book is available via Elsevier and at a range of online bookstores: Amazon, Google, etc .

Mark P. Kearns is the Senior Technology Manager of the Advanced Manufacturing Innovation Centre, Queen’s University, Belfast and Rotational Moulding Research Manager at Queen’s University, Belfast. A Chartered Chemical Engineer and Fellow of the Institution of Chemical Engineers, he has been active in rotational moulding research, industrial support and innovation projects for over 25 years. Mark has co-authored two textbooks, over 60 papers and has presented advanced rotational moulding technology seminars and keynote presentations worldwide.

Welcome from Matt Bushman, ARM’s new President

First, I want to wish everyone a very Happy New Year!  After a couple of challenging years, we are all  looking forward to a better 2022. I am pleased that there are very encouraging signs that we are emerging from the worst.

As I reflect on the past two years, I am extremely proud of our industry response and successful navigation throughout these uncertainties.  The perseverance and professional commitment of the ARM staff, directors, and membership has been quite impressive and greatly appreciated.

Our theme for 2022 is Creating Efficiencies.  Meetings, seminars, and webinars will embrace this theme throughout the year.  Our industry as a whole is very healthy even though labor and supply chain issues persist.  

Efficiency objectives are achievable through: strategic planning, scheduling, automation, and recruiting. Many of these topics will be addressed at our Executive Forum in Amelia Island Florida, March 14-16. Learning about our members and their operations can be a great way to enrich our own processes and facilitate creative thought.

Please seriously consider participating in ARM’s webinars.  They provide immense value and knowledge without the necessity of leaving your office.  ARM is here to serve our members and interact through sharing  ideas and experience.  There’s a listing of our webinar library available here.

Lastly, thank you for your continued support.  I look forward to a prosperous and positive 2022.

We’re moving on!

Matt Bushman
2022 President, Association of Rotational Molding
President, Plasticraft Corporation

What causes oven fires and how to respond

ARM Technical Director Nick Henwood

A rotomolder member of ARM asked about recommended actions in relation to fires in rotomolding ovens. These fires are typically caused by powder spilling out of a mold during the cooking process.  This can be due to:

  • Incorrectly closed clamps, or clamps that fail, causing the mold to open as it rotates
  • A missing vent pipe, either because the operator forgot to insert it or because it was inadequately fixed and fell out during mold rotation
  • Missing vent fill media, either because the operator forgot to insert it or because it was incorrectly inserted and fell out during mold rotation
  • A damaged parting line that is leaking powder

Once the powder is released from the mold, most of it will fall to the oven floor where, as a minimum, it will melt and causes a mess.  With prolonged heating, it may catch fire spontaneously and create smoke.  Some of the powder (the finer sized fractions) may be drawn into the burner duct by the circulation fan.  This finely divided, combustible, material will then come into contact with the burner flame and may create an explosion.  Alternatively, repeated spillages may coat the sides of the burner duct and create an on-going fire hazard.

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Will future rotomolders be gas-free?

Dr. Nick Henwood

As a representative of ARM, I was recently asked in a discussion with some other ARMO groups about whether electromagnetic induction heating could be suitable for rotomolding.

The issue was raised because of how the Emissions Reduction Plan of New Zealand may limit rotomolders’ ability to use gas to power their rotomolding machines. Today there is increased pressure, around the world, to limit carbon dioxide emissions.  Therefore alternative heating systems for rotomolding machines is becoming a pressing subject; it’s worth thinking about now because, in the future, manufacturers in other territories may face similar limitations to the ones being proposed in New Zealand.

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