Category Archives: Uncategorized

Rotomolding Education Sessions at the ARM Annual Meeting in Houston

ARM continues to announce new presentations for our Annual Meeting in Houston (October 27-30). We’ve listed approximately 2/3 of the program below. There’s still more to come.

Hidden Costs Only Front Line Personnel See and How Making Toast Can Find Them
Ken Bather, Hedstrom Plastics

This workshop is an interactive program using the Shingo Prize-winning Introduction to Continuous Improvement & Lean Principles video combined with actual rotomolding plant operations. A great first step to having your front line operators tell you where your hidden costs are lurking. This workshop is the icebreaker to get over the initial hump of the “we’ve heard it before” attitude by making a relatable link between something everyone can actually relate to and the often unrelatable process of Lean Continuous Improvement. It nails the 7 wastes by showing how to find them with real rotomolding operation examples and gives you the opportunity to take the information back to your team. Introduce or reinvigorate lean concepts to your shop floor production team without onerous terms, paperwork, or oversight. This is a simple way for the hidden talents of your team members to shine through and save you money and lost margins.

Case Study on Slushing Tests for Diesel Tanks
Celal Beysel, Floteks

The market for rotomolded diesel fuel tanks and Adblue [urea] tanks is growing globally. Further market penetration for Commercial Vehicles with irregularly shaped high volume tanks holds much potential & promise for rotomolding. Floteks has developed patented technology to mold integrated baffles; these have been tested with sloshing simulations and experiments, accelerating the tanks to +/-0.8 g.  This technology also enables to mold an integrated fuel and AdBlue tank separated by a 100% sealed baffle.

Keeping Powder and Pellets Out of the Environment
Doug Biela, NOVA Chemicals

In a time when plastics and the environment are on the minds of consumers, politicians and our customers, this discussion will highlight the paramount importance of keeping powder/pellets out of the environment.  It will cover management systems and tools that rotomolders can employ to ensure that their plants are not putting plastic where it’s not supposed to be.

Rotomolders will gain an understanding of some actions they can take immediately to improve their powder/pellet management and reduce or eliminate environmental impact.  They will also learn about Operation Clean Sweep® and how to join other rotomolders to take the pledge to eliminate pellet and powder leakage into the environment.

Alternative Materials in Rotomolding Today
Ron Cooke, ExxonMobil Chemical Company
Ron Joannou Jr., Formed Plastics Inc.

This workshop will provide rotomolders with an understanding of materials other than polyethylene that are successfully being used in rotomolding operations today. The discussion will include the attributes molders are looking for in their parts and which materials may work for them.

What’s Your Problem?
Ron Cooke, ExxonMobil Chemical Company
Sandy Scaccia, Norstar Aluminum Molds

An ARM tradition: troubleshoot your problems with your colleagues and industry experts. This is a simple and effective workshop that can change your operation, help you reduce scrap, and reduce significant expenses.

Pigment warpage and interactions with HDPE Rotomolding resins
Mike Haubert, Mosaic Color and Additives

In order to provide rotomolders with a deeper understanding of how pigments affect their process, this presentation will report on new research comparing various pigment choices in HDPE. Shrink, warp and impact have been measured to compare how individual pigments affect performance.

Dry Blending Study
Dr. Nick Henwood, Rotomotive/ARM Technical Director

Funded by the Roy Crawford Rotomolding Educational & Development Foundation, this study examines the effects of pigment dry blending on material strength. It builds on previous research and concentrates on the effect of pigment type on the retention of impact strength.

Industry 4.0 Will Rotomolding Be Left Behind?
Eric Maziers, Total
Johan Portagent, AMS Belgium

The Industry of the Future 4.0, the 4th industrial revolution, will certainly change manufacturing. This is a real industrial revolution with the arrival of Automation, Predictive Maintenance, and Big Data. The fourth industrial development is coupled with major changes in the world: energy, environment, organizational, and societal interests. The human will be at the very center of this industry with a new role: Digital will be between machines and workers. New jobs will be created and training will be strategic in organizations. It’s an amazing opportunity for the rotomolding industry to enter a new age to bring new opportunities: innovation (process and resin developments, new kinds of studies), competitiveness, productivity, customer focus, service focus, a factory networking suppliers and clients, high flexibility, a clean plant oriented to sustainability, an automatized plant to get rid of hard work for people. Let’s have a look to see if the rotomolding industry can enter soon into the industry of the future 4.0.

An Industry Profile of Rotational Molding
Troy Meinhard, KnowHow Strategy & Analytics

Comprehensive market intelligence on the rotational molding industry is limited.  Low product volumes make data challenging to collect and general plastic industry market research doesn’t address the rotational molding industry in detail because rotational molding is <1% of annual resin consumption.  By combining existing sources of data in an analytically rigorous way and supplementing it with creative and gritty data acquisition from non-traditional sources, ARM and KnowHow have created an industry profile that segments and sizes the producers and consumers in the industry along multiple dimensions.

Members will have a data-driven understanding of the structure of the industry. This market intelligence is critical context for:

  1. Sales planning

  2. Growth strategy development

  3. Competitive analysis

  4. Baseline for understanding changes in the industry (e.g., the impact of consolidation, generational transfer that results in sales to strategic and financial investors)

  5. Other business decision-making

Modeling the Rotomolding Process: Practical Benefits and more
Hassan Riaz, NOVA Chemicals

In this presentation, the complete functionality of RotoSim as a process modeling tool is explored at the NOVA Centre for Performance Applications. Mainly, the importance of model inputs such as machine conditions, resin properties, and mold drawings will be discussed as well as a protocol to follow for molders to build confidence in RotoSim as a technical tool. Furthermore, this presentation will outline how to practically apply modeling results from RotoSim, such as PIAT curves, thickness distributions, etc. to guide molder’s manufacturing processes.

Designing for the Future
Martin Spencer, UniqueRoto

The presentation looks at how rotational molding has changed over recent years with new machinery and materials now available to molders. It will look at how, if grasped, by molders these developments open up many new markets and opportunities giving those designing considerably more freedom to exploit the process.

Rotomolding Application in Historical Preservation and Artifacts
Oliver Wandres, MAUS GmbH
Alongkorn Kanokboriboon, SCG ICO Polymers

Case Study on converting very traditionally wood carved artifacts to beautiful rotational molded products which — with a great amount of post-molding work — become unique pieces of artwork, that on a first glance nobody would or could associate with rotomolding.

In close co-operation between the end customer, SCG ICO Polymers and MAUS GmbH were able to develop the sensitive transformation from historical and religious wood carved objects to very unique examples of what is achievable in rotomoulding when combining handcraft, high-quality mold making, the latest mold making technologies, and out of the box thinking.

This case study provides an example of the infinitely versatile application possibilities of rotational molding.

There is still more to be announced. Register for the Annual Meeting today. 

Conchita Miranda & Jon Ratzlaff to be Inducted in the Rotational Molding Hall of Fame

ARM is excited to announce that Conchita Miranda (Operadora Miraplastek) and Jon Ratzlaff (Chevron Phillips Chemical Company) have been elected to the Rotational Molding Hall of Fame. They will be inducted on October 29 at the ARM Annual Meeting in Houston.

Conchita 2016 HD (1)

Conchita Miranda

The longest-serving member of ARM’s Board of Directors, Conchita has been a strong and active supporter of the rotomolding industry for many years. She has always been a dynamic member of ARM: volunteering her time for the success of the Association, participating in most of ARM’s committees, and presenting the Introduction to Rotomolding seminar in Spanish. She has written for Rotation Magazine and Rotoworld.

Conchita is a second-generation rotomolder and the Director General of Operadora Miraplastek. She began attending ARM meetings as a teenager. She is recognized by many rotomolders as an outstanding leader in our industry and a promoter of our industry throughout Latin America. Our members have also recognized her focus in continuously strengthening relationships with members and making ARM a very inviting environment for decades.

JDR 1200 - ARM

Jon Ratzlaff

Jon’s extensive experience in numerous plastics disciplines affords him exceptional insight into the advantages of the rotational molding process; which he has shared throughout the world.

He is currently Technical Service Manager Polyethylene with focus on product, application, and business development for polyethylene products for Chevron Phillips Chemical Company.

Jon has served on ARM Committees and has presented many times at ARM meetings and via webinar. Jon is a contributing author to Handbook of Industrial Polyethylene and Technology, including writing the Rotational Molding chapter.


The Nomination & Election Process

  • Nominations for the Hall of Fame were collected from the industry throughout the Spring.
  • All nominations received from 2014 – 2019 serve as the longlist.
  • The ARM Executive Committee elected a Hall of Fame Selection Committee comprised of six members of the Hall of Fame.
  • The Selection Committee votes on the longlist to narrow it to a shortlist of five nominees.
  • All Hall of Fame members were delivered a ballot to elect two inductees from the shortlist.
  • Conchita Miranda and Jon Ratzlaff will be inducted October 29 in Houston.

Register to attend the Annual Meeting in Houston.

Ask Dr. Nick: A Basic Review of Foam in Rotational Molding


Dr. Nick Henwood

ARM often receives questions about the foaming process as it relates to rotomolded parts and we thought a basic review might be useful.

 A number of different foam products have been used in conjunction with rotomolded articles, in order to impart enhanced properties.  These include:

  1. Polyurethane (PU) Foam, injected into a cavity in the final rotomolded part, with the aim of completely filling it.  Typically, a fully cooled part is contained inside a foaming fixture and the foam components (polyol and isocyanate) are mixed and injected through a special nozzle.  The creation of the PU Foam is extremely rapid, once the components are fully mixed.  PU Foams have very low density (typically 0.050 g/cm³), which gives them excellent heat insulation properties.  They are also used to add buoyancy to marine components.  There is no bond between the PU and the PE part and de-lamination of the foam is instantaneous.  The PU Foam does not impart any additional stiffness to the product.
  2. Expanded Polystyrene (EPS) Foam, created in a cavity in the final rotomolded part, with the aim of completely filling it.  Typically, a fully cooled part is contained inside a foaming fixture and pre-expanded EPS beads are poured inside the part.  Steam lances are then inserted into the part and the associated heat further expands the beads.  This process takes time (typically tens of minutes) to complete.  EPS Foams have low density (typically 0.150 g/cm³), which give them moderate heat insulation properties.  However, they are mainly used to add buoyancy to marine components.  There is no bond between the EPS and the PE part.  The EPS Foam does not impart any additional stiffness to the product.
  3. “Syntactic” Foam, created in a cavity in the final rotomolded part, with the aim of completely filling it.  These are composite materials; for rotomolded applications they usually consist of an epoxy-based polymer matrix with hollow glass spheres suspended in it.  This structure provides low density and very high stiffness / crush resistance.  The density can be adjusted over a wide range, but when used in rotomolded products, it is typically in the range 0.400-0.500 g/cm³.  The main application is for subsea flotation devices (eg flotation collars around undersea pipelines), where they impart high resistance to crushing by water pressure.  There is no bond between the PU and the PE part and de-lamination of the foam is instantaneous.
  4. PE Foam, which differs significantly from other types.  PE Foam is generally added as a second charge during the molding process, when an outside skin of standard solid PE has already been formed.  In this case, the aim is not normally to completely fill the cavity; rather, the aim is to produce a second layer of even thickness around the inside of the rotomolded part.  This imparts a degree of extra stiffness and a degree of heat and sound insulation (although significantly less that Options 1&2).  There is a full bond between the PE Foam and the outside PE skin.  The density of PE Foam can be adjusted over a limited range, the minimum practical density that can be achieved is approx. 0.200 g/cm³ and the maximum density is, theoretically, the density of the PE used in its formulation (i.e. zero foaming).

For more information, ARM’s website includes a free webinar for members on In-Process Rotational Foam Molding, conducted by Dru Laws. Late this summer and throughout 2019, ARM will conduct a series of webinars on Finishing that will go into more detail on foams.

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.

President’s Message: Investing in New Value for Members


Dru Laws

As I write this, I have just returned from ARM’s Summer Board meeting. This is the Board’s longest meeting of the year and it is typically used for planning. As a result of the Association’s success over the last few years, we were able to spend a lot of the meeting talking about ways to invest in value for all of our members.

The various ideas for adding for members can be separated into three categories:

  • Making rotomolding more productive
  • Promoting for the rotomolding process
  • Providing research into the rotomolding market

Some of the ideas are bold long-term projects that we will study before we move forward.  One project we have acted quickly on, and I hope we can announce within the next few weeks. And the other ideas are somewhere in the middle.

One of the drivers of these discussions is a new ad hoc committee focused on Productivity Improvement, this project of ARM and the Roy Crawford Rotomolding Education Foundation has been driven by ARM Past President Corey Claussen and Vice President Rick Carlsen. The group spans our industry and supply base. Their goal is to research, experiment, document and make available methods to improve the industry’s productivity. They have wide-ranging discussions on automation, robotics, material development, and mold building methods. They’re focused on identifying areas that we can invest in advancing our process and communicating valuable productivity improvements that already exist.

Over the past year, ARM has seen an uptick in new members. This is one of the reasons we’re able to invest in new value for members. In the first five months of 2019, these companies have joined ARM:

  • Alpha Systems
  • Aquaplastica
  • Bergen International
  • CIPSA Industrias
  • Crane Resistoflex
  • Ecotank
  • Fibeco
  • Houry Design Services
  • Legend Brands Dri-Eaz
  • Progen
  • Rock Lake Robotics
  • RPS Corporation

ARM just finished our Spring regional meeting schedule. We held two regional meetings on Warping Parts in California and South Carolina. Our final regional meeting will be held in Minneapolis on June 18. Also, I personally had the pleasure of presenting a two-day hands-on rotomolding course at Penn College in Williamsport, Pennsylvania. All of these meeting attendees will tell you just how valuable face-to-face meetings can be. I hope we’ll see all of you at our Annual Meeting in Houston this October 27-30. It will be well worth your time.

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

Why is there (what looks like) orange contamination in my powder?


Dr. Nick Henwood

Bizarre as it may seem, in the past few weeks, I’ve had two different consultancy customers report powders with this same problem.  They sent me samples and parts but, even before they arrived, I suspected that the problem was gas fading.

Some of you may have experienced this phenomenon before, and wondered why it happens:

The problem: A coloration (usually either orange or pink colored) that you can see clearly in your powder.  I’ve included a photograph below, to illustrate the point.  This material was actually compounded white, but it can show in natural material as well…


Despite appearances, this is not just a gross contamination of the powder, it’s something else.  So – what is it? Continue reading

ARM Members Access 55 On-line Training Videos

For ten years, ARM has been building a library of webinars and training videos that are available to our members online.  We currently offer 55 titles. Members can access all of these titles immediately. Non-members can join here.

Online training includes:

  • Operator Training Program (25 Videos) presented by Nick Henwood, Dru Laws, and more Click for the detailed contents
  • Burner Maintenance presented by Adam Covington
  • Considerations When Light-Weighting Rotomolded Parts presented by Henry Hay
  • Cooling Fixtures presented by Ron Joannou Jr. and Joey Morsi
  • Determining Your True Cost presented by Steve Osborn
  • EPCRA Reporting & Combustible Dust (with Roto 101 Intro) presented by EPA & OSHA
  • Finishing Parts with Robots (Case Study) presented by Dru LawsFinite Element Analysis: The Basics presented by Michael Paloian
  • Improving Rotational Molded Insert Performance presented by Glenn Larkin and Jon Ratzlaff
  • In-Process Rotational Foam Molding presented by Dru Laws
  • Infrared Thermography presented by Bill Spenceley
  • Lengthening the Life of Your Mold presented by Tony Short
  • Making the Most of Your Marketing Budget presented by Melissa Shearer
  • Mold Clamping Methods – Pros and Cons presented by Erik Adams and Bob Mueller
  • Mold Release presented by Even Silo & Scott Waterman
  • Prop 65 for Rotomolders presented by Mike Haubert
  • Proper Sampling Techniques presented by Josh Hunsberger and Dave Loeffler
  • Rebranding Your Business (Case Study) presented by Tom Innis
  • Rotational Molding & the Evolving Structural Part Processing Business presented by Dr. Peter Mooney
  • Roto 101 presented by Rick Carlsen & Ron Joannou Jr.
  • Safety in Rotomolding & OSHA Compliance presented by Dave Schwoerer
  • Save Energy & Save Money presented by Bill Spenceley
  • Selecting the Right PE Grade for Your Part presented by Nick Henwood
  • Solve Cosmetic Part Problems presented by Jon Ratzlaff
  • Stiffness Models and Options for Multi-Layered Parts presented by Dr. Nick Henwood
  • Test Method for Flowability (Dry Flow Rate) of Polyethylene Powders Using a Specified Funnel presented by Ron Cooke & Jon Ratzlaff
  • Troubleshooting Your Rotomolding Operation from a Shop Floor Perspective presented by Ron Cooke
  • Turning a 4% Bottom Line into a 10% Bottom Line presented by Al Bates
  • Understanding the Molding Cycle presented by Gareth MacDowell
  • What Does Internal Air Mold Temperature Have to do with Quality presented by Gareth McDowell
  • What’s Your Problem (2 videos) presented by Ron Cooke & Sandy Scaccia

Ask Dr. Nick: Why does the same mold need different cook times in a different rotomolding machine?


Dr. Nick Henwood

Rotomolders who have multiple machines often find that, if they move a mold from one machine to another, an adjustment in cooking conditions is invariably required.  The differences between machine performance can be considerable. Whilst this may be expected when moving from one style of machine to another, an adjustment may even be required when moving between machines of the same type or model.

Whilst most rotomolding grades of polyethylene are actually quite forgiving of processing variations, the issue becomes especially relevant when molding materials with a narrower processing window (eg repro, foams, polypropylene or crosslink).

Why can there be such a big difference?

The first thing to understand is that the temperature showing on the control panel of your machine is, almost certainly, not the actual temperature in the oven.

The oven requires a control signal that will call on the burner, when required.  This signal is a temperature, measured by a thermocouple located in the burner duct.  The burner duct is a passage external to the main oven, which contains a circulating fan and the burner itself.  The action of the circulation fan draws air out of the main oven, raises its temperature (if necessary) by switching on the burner, then sends the air back into the main oven at a different place.

The position of the control thermocouple in the burner duct will make a significant difference to the temperature it reads.

In many North American machines, the control thermocouple is located upstream of the burner.  In this case, the temperature measured will be less than the temperature in the main oven, because heat will already have been taken out of the air stream by the action of warming the contents of the oven (ie the arm, plate, molds and mold contents).

In some other well-known brands, the control thermocouple is located downstream of the burner.  In this case, the temperature registered will be more than the temperature in the main oven, because heat will not yet have been absorbed by the contents of the oven.

So, the temperature showing on the machine control panel is most unlikely to be the same as (or even similar to) the temperature in the oven.  Its purpose is simply to act as a control variable, to operate the burner. Clearly, its value is related to the oven temperature, but it will not be the same.

In many ovens, the difference can be significant.  In addition, the difference will vary depending on the Actual Oven Temperature.

To illustrate the point, I have shown data from my gas-fired laboratory machine.  This is laid out in the same way as larger roto ovens, with a burner duct containing a circulation fan, the burner itself and a control thermocouple.

Using a K-PAQ that I have permanently installed on the arm of my machine, I measured the Actual Oven Temperature achieved after the system had reached equilibrium.  I then varied the Set Point Temperature (ie the temperature showing on the control panel), waited for the oven to reach equilibrium and recorded the Actual Oven Temperature again.  I repeated this procedure for a number of Set Point Temperatures and produced the Oven Characterization Curve shown below.

Screen Shot 2019-04-09 at 4.50.37 PM

You can see from the graph that, for my oven, the Set Point Temperatures were consistently lower than the Actual Oven Temperatures.  For example, at 300°F Set Point, the Actual was 370°F (70°F difference). At 375°F Set Point, the Actual was 460°F (85°F difference).  At 450°F Set Point, the Actual was 545°F (95°F difference).

So, even the numerical difference between Set Point and Actual is not fixed.  To fully understand the relationship between these two temperatures, you need to perform a characterization exercise across your normal oven operating range.  Then you will know what Set Point Temperature on Machine A is equivalent (in terms of Actual Oven Temperatures) to a certain Set Point Temperature on Machine B.  You need to characterize and compare all the ovens in your shop.

Of course, if you constantly use in-mold temperature measurement to control your process, you don’t need to worry with any of this.  However, for the 99% of moulders who don’t do this, characterizing your ovens will be a good start to achieving better process control and more operational flexibility.

With a bit of ingenuity, you can do a characterization with a hand-held thermocouple.  Alternatively, you could get someone with a K-PAQ (or similar device) to come and do it for you.  Once this exercise is done, you will be set up well for future operations.

Happy rotomolding!

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.