Ask Dr. Nick: How does cold weather affect the rotomolding process?


Dr. Nick Henwood

You may have heard that in England, when we’re not obsessing about Brexit, we often discuss the weather.  This is odd, when you consider that, other than a lot of rain, we don’t see extremes of weather that often.

Recently, we’ve experienced what we Brits would regard as some cold weather, although it’s been nothing like as bad as that experienced by my friends in the Midwest.  I recently phoned Adam Webb in Chicago, on the day when outside temperatures sank to minus 50°F.

My rotomolding lab in UK is a 1,500 sq ft industrial unit, of pretty standard construction (mainly precast concrete panel).  On a recent morning, I experienced an ambient temperature of 30°F, when I opened up the molding area. This compares to an ambient temperature in the range 60-80°C during mid-summer and even higher after a heavy day of rotomolding.

I’m molding all year round, for my various R&D  and consultancy projects, and I know it’s important to maintain consistency.  The question is: how big an effect will ambient temperature have on what I produce and how I produce it? Continue reading

President’s Message: Serving Our Members


Dru Laws

As I enter my final year as ARM’s President, I’m excited to continue to the shape the future of the Association and rotomolding. We had an amazing 2018 with the implementation of the Operator Training Program, a successful meeting in Montreal, and great technical value for members including the much anticipated Resin Guide.

2019 Goals

  • Grow Membership
  • Get Involved
  • Improve Technical Content

ARM prides itself as an association that is welcoming to new members and new ideas. We hope to continue to grow membership in 2019 to increase value for current members and grow the rotomolding industry as a whole. If you know a company that would be a good fit for ARM, contact our staff at

I hope that you will consider joining a committee this year. Committees are open to all members and require little commitment but return a great investment on your time.  If a committee isn’t your cup of lemonade, join us on a Hot Topics in HR call, troubleshooting calls, or a webinar. These are all free for members and provide value without having to leave your office. From the networking opportunities to the ability to shape the industry, I think you will enjoy getting involved with ARM in 2019.

We are happy to again have Dr. Nick Henwood as the Technical Director for ARM in 2019. Dr. Henwood provides blog posts, input on webinars, and reviews all materials for meetings. ARM is dedicated to improving technical content and continuing to be your go to source for knowledge about rotomolding. This year’s webinar series will focus on finishing training.

We are planning to update the Resin Guide and hold three regional meetings focused on How to Stop Warpage. This year’s Annual Meeting in Houston is being organized now but we know it will offer a valuable program for rotomolders at all levels and Spanish translation.

The Roy Crawford Education and Development Foundation will offer a scholarship for graduating seniors. Details are available here.

ARM exists to serve our members and we want you to feel that value.  Please consider recommending a new member, getting involved with a committee or call, and taking part in our technical programs. I’m excited for the year ahead and to make my last year as President one for the record books!

Dru Laws is the President of ARM and the Senior Vice President of Seljan Company in Lake Mills, Wisconsin.

Ask Dr. Nick: Can I fix gaps in a parting line?


Dr. Nick Henwood

A badly fitting parting line is a regular pain in the neck, for a number of reasons.  The most notable annoyance is that, as the mold rotates in the initial stages of heating, powder spills out from any gaps that exist.  This wastage of powder can cause an under-weight part and, even if the spillage is small, the powder burns, makes a mess in your oven and creates a nasty smell.  Better to avoid the problem, if you can!

Recently I was given an old steel test mold from another lab; it was a hexagonal cylinder used to make 5 inch square plaques for the ARM Low Temperature Impact Test. (The procedure for this important test is available on the ARM website.)  The first time I put the mold on my machine, I noticed that I had a small powder spill from the parting line area.

gap edited

By good fortune, the next day I participated in one of ARM’s Troubleshooting Calls; we run these every month, as a free-to-member service.  One of the regular moderators is Sandy Scaccia of Norstar, who is one of our industry’s top mold experts.

During the call, I asked Sandy for some advice about what I could do to reduce, or hopefully eliminate, the parting line gaps.  He told me of a procedure he had used for aluminum molds: heat up the affected area and use an exterior clamp to squeeze the parting line shut while it is still hot.  He expressed some doubt that this would be as effective for a steel mold, but I thought it was worth a try. Continue reading

Miller Time: More on Angel Hair


Rob Miller

Further to Dr Henwood’s comments on Angel Hair, I would like to add the following…

Dr Henwood is correct that it is typically formed due to high temperatures in the conveying line.

I would comment that a good conveying system design utilizing good conveying parameters can be employed to eliminate the creation of angel hair, therefore eliminating the need for any kind of angel hair trap. Traps can be helpful in collecting the angel hair that is created, but why not investigate and potentially eliminate the basis for the angel hair creation?

Most conveying in the plastics industry is known as “Dilute Phase conveying”. This typically represents that the conveying line is approximately 10-15% material concentration at any given moment.

In the designing of a conveying system, there are limited factors that can contribute to a safe or unsafe conveying situation.

Velocity is everything in conveying. Continue reading

Ask Dr. Nick: Avoiding “Angel Hairs”


Nick Henwood

On ARM’s most recent What’s Your Problem? teleconference, there was a question asked about powder piping systems, especially about avoiding and dealing with “angel hairs”. I provided some follow up to the molder after the call, which we’re happy to share here for everyone’s use.

My first recommendation was to contact ARM’s mainstream pulverizer supplier members, who should be able to offer good advice. They are the real experts in this area.

In the meantime, I also recommended installing simple traps for angel hair in your lines.  Pulverizer systems have these in place.  The grid has something like ½ inch gaps and the sideplate can be opened for manual removal of accumulated debris.  The pulverizer folks will have proper drawings of this; please excuse my rudimentary draftsmanship!

trap for angel hair

As far as I’m concerned, angel hair production gets bad when ambient heat is sufficient to start to soften powder particles.  A particle momentarily trapped on an obstruction will then get stretched and elongated by fast air flow around it and a hair gets formed.  So keeping temperatures down (say below 100°F), or not generating elevated temperatures in the first place (correct pipe sizing and avoidance of sharp bends), should help a lot.

Note from staff: ARM offers What’s Your Problem? teleconferences — an audio version of our popular troubleshooting workshop — to our members every six weeks as a free benefit of membership.

Dr Nick Henwood serves as the Technical Director for the Association of Rotational Molders. He has 25 years-plus experience in rotomolding, specializing in the fields of materials development and process control. He operates as a consultant, researcher and educator through his own company, Rotomotive Limited, based in UK.

Executive Forum in Napa: Speakers

Join your rotomolding colleagues March 25-27 at the Archer Hotel in Napa, California for the ARM Executive Forum. Below we’re highlighting a few of the event speakers.

Dr. Christopher Kuehl, Armada Corporate Intelligence , is one of our highest rated speakers and we’re glad to welcome him back after speaking at the Executive Forum in 2015. He has been Armada’s economic analyst and has worked with a wide variety of private clients and professional associations. He is the chief editor for the Business Intelligence Briefs, distributed all over the world by business organizations and he is one of the primary writers (with Keith Prather) for the Executive Intelligence Briefs.


Chris Kuehl

Seeing the Dark Cloud Behind the Silver Lining – Five Things to Worry You in 2019

There is no doubt that 2018 was a good economic year – low unemployment, solid growth, a robust (if volatile) stock market. But trouble is never very far away and 2019 is likely to be a lot less encouraging. The five most worrisome aspects of the coming year will include the return of inflation, negative reactions to the trade wars, truly bitter partisanship in government, mounting debt levels for the government, corporate community and the consumer and drastic changes in leadership for countries that matter to the US (Mexico, Brazil, UK, Israel, Germany and others).
There will be some bright spots as well – nobody wants to be utterly depressed so early in the year. The real question will be whether the bad stuff can be managed and dealt with soon enough to avoid a recession at the end of the year or early 2020.

Ben Varquez is a partner at Whistle Work, an employer and industry branding, recruiting and retention solution. He’s also the managing director of Youth Marketing Connection, the largest student-focused marketing agency in the United States. Throughout his career, he has worked closely with industry leaders such as Google, Capital One and Spotify and leading trade and professional associations such as the American Institute of CPAs and the Center for Audit Quality. Varquez is a graduate of The George Washington University’s School of Business, an outdoor enthusiast and a lifelong learner. He enjoys cooking, building furniture and playing ultimate frisbee.



Ben Varquez

Attract and Retain the Next Generation Workforce

Many plastics processors  struggle to find candidates to fill their job openings. Low unemployment, while a great sign for the economy, compounds this issue. In this session, you will take an all-encompassing look at developing, recruiting and retaining your future workforce. You’ll learn best practices by reviewing multiple research studies, engaging with experts and analyzing real-life examples of what Millennials and Gen-Z are looking for in a career and employer.


John Mackay

John MacKay, Chairman of the Mackay Research Group, served as Vice President of the Profit Planning Group, a research and executive education firm headquartered in Boulder, Colorado. He joined the Profit Planning Group in 1982 to head up its profitability survey activities. Over his 20 year tenure, John helped build PPG’s client roster from 1 to 80 associations, most of which were distributor-member based. In 2001, PPG began to expand its client base to include more trade associations with manufacturer members. In the process, it became clear that many of the tools PPG had developed for distributor clients did not quite fit for manufacturers and that some changes would be required. To respond to this growing need, in 2003 Mackay spun-off a segment of the company so he could work with manufacturer clients in a more targeted manner. John is a frequent seminar and convention speaker on topics such as Improving the Bottom Line, Getting Serious About Profit, and Doing More with Less. John received his undergraduate degree from The Ohio State University and his MBA from the University of Colorado.

Insights from the ARM Wage and Benefits Survey

John Mackay and Taylor Mackay will present on the compensation they conducted of ARM members. They will present key insights to the entire meeting, and conduct an additional discussion with those companies that submitted data.

Jon Ratzlaff, Chevron Phillips Chemical Company, is the Technical Service Manager (for Rotational and Injection Molding Polyethylene) responsible for business development and support through design, processing, and polymers (technical services).  Jon has been involved in the plastics industry for 30 years. He holds experience in rotational molding, injection molding, compounding, extrusion, film, sheet and thermoforming. He is a graduate of Oklahoma State University in Chemical Engineering. He has time well spent in management, manufacturing, quality, research and development, and technical service which includes his favorite: product/application & business development.  He was on the Executive Board of the Society of Plastics Engineers for 7 years including the President in 2013-2014.


Jon Ratzlaff

Exciting Growth in Plastics Require Sustainable Solutions

Today  is an exciting time to be in plastics industry.  With an ample supply of low cost feedstock, North America has seen unprecedented increases in plastics production.  Polyethylene in particular has seen the highest production growth in the history of North America.  But in spite of high growth coupled with strong worldwide consumer demand, plastics have come under fire in the public’s eye with increased attention being placed on mishandled plastics entering our waterways and oceans.  Some have proposed plastics bans,  but the truth is these materials are needed by a growing middle class to meet basic human needs for safe food, safe water and energy efficient homes and transportation.  In response, a range of programs are under development to address post consumer plastics mismanagement around the world while continuing to meet the needs of a growing middle class. This presentation will highlight drivers behind this unprecedented industry growth, the challenges faced by our industry and the illustrate examples of programs under development to deliver sustainable solutions globally.

Panels and additional speakers will be announced as well. For more information and to register visit: 

The State of ARM: Scholarships for High School Seniors

The Roy Crawford Education and Development Foundation has just announced that it will award three scholarships to graduating seniors this coming spring.

Employees of ARM member companies and their children are eligible to apply by completing these forms by March 18, 2019. The Foundation will award at least three scholarships of $2,000 each.

This scholarship is a new benefit that ARM member companies can offer employees! Please spread the word among your company.

We are also announcing multiple ways to support the Foundation. Make a general donation to support all of the Foundation’s projects (including rotomolding R&D and education), help build our scholarship fund for future years, or make donations that will be used in their entirety to increase the total scholarship amounts awarded in 2019.