Category Archives: Uncategorized

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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In 2022, bring your operators to Intro to Rotomolding

Dru Laws hosts an Introduction to Rotational Molding seminar in Buena Park, Calif. on February 4. You can register for this full-day program here.

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.

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.

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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What constitutes ADEQUATE venting?

Dr. Nick Henwood

When I train machine operators, I tell them that, most likely, venting problems are the biggest cause of scrap parts they will come across.  This statement was originally based on a survey conducted by the ARM many years ago.  After 30 years in this business, the statement still holds true, as far as I’m concerned.

Creating scrap parts because of bad venting is totally avoidable.  This is one aspect of rotomolding that absolutely isn’t rocket science (not much is, actually).

If you have inadequate venting, or if your vents block during the process, you will get parts with defects.

During the cooking stage, inadequate venting will create a build-up of pressure in the mold, as the air inside heats up and cannot expand through the vent.  At some point in the cycle, molten plastic will be forced into the parting line (or any other potential emergency air release passage).  The result will be the creation of flash along the parting line, which will need to be trimmed off.

Worse, inadequate venting in the cooling stage will create a vacuum in the mold, as the air inside cools down and cannot draw more air in through the vent to equalize the pressure.  At some point in the cycle, air from outside will penetrate the parting line.  The result will sometimes be bubbles along the parting line (on the inside of the part) or, more likely, a small hole where a bubble has formed and then burst.  Either way, you’ve got a part that is either scrap, or else requires re-work.

There’s a photograph below that illustrates both issues.  This was made in a test mould I have that actually has no vent.  You can clearly see the flash that was formed during cooking and the bubble that was created during cooling.

Horrible!.  So how can you avoid this and, specifically, what constitutes adequate venting?

In the first instance, an “adequate” vent (or vents) has an opening that is large enough to allow adequate flow of air from inside to outside the mould, at all points in the cycle.

So far, I’ve not been able to find any sources of primary research into this, but there are a number of authorities that state rules of thumb relating vent diameter (note this is the inside diameter) to mold volume.  These rules of thumb express themselves in various units, but the most useful way I’ve seen of expressing it is in terms of vent open cross sectional area (CSA) per mold volume.  A typical number is:

0.01 in2 of vent open CSA per ft3 of mould volume

I’ve used this figure to calculate what this means, for various volumes of mold (see table).  Note that this data relates to vents without packing.  If you do use packing (wire wool, mineral wool, rolled-up scotch pads etc), I have seen recommendations that you double the CSA of the vent provided.

How can you estimate the mold volume?

  • If your mold has been designed using computer aided design (CAD), the mold cavity volume should be directly available from the design file.
  • If your part is a relatively simple geometric shape (eg a cylinder or box), you can roughly calculate it.
  • Another idea would be to fill a finished part with water and weigh it.
  • Either way, this doesn’t need to be exact; it’s a guide only.

Have a look at some of your existing molds and see whether, according to this table, you already have adequate venting.  You may be surprised at what you find!

Happy rotomolding!

Dr Nick Henwood serves as the Technical Director for the Association of Rotational Molders. He has 30 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.

ARM Training Series on Health and Safety

Beginning October 20, ARM will deliver our next training series directly to ARM members’ inboxes. Technical Director Nick Henwood has created presentations on health and safety that you can use for staff training. 

Topics covered include: risk management, machinery safety, heat, explosions, slips, trips, and more.

The first four presentations will be released every other week in October and November. The final four will be released in the first quarter of 2022.

This new series on Health and Safety follows previous webinar series on Operator Training, Finishing, and Design. All are available free and on demand to ARM members, in addition to hundreds of additional training, technical, and roto industry webinars and videos.

We now offer more than 100 videos on-demand for members. Non-members can join ARM here. Members can access all of the titles listed below immediately. 

ARM awards industry leaders and student designers

The Association of Rotational Molders presented a number of awards and recognized Board members who have completed their service to ARM at our Annual Meeting on September 23, 2021.

  • Charles D. Frederick Distinguished Service Award was presented to Michael Paloian of Industrial Design Systems
  • Student Design Awards were given to Bryce Lee, Amanda Evans, and Szymon Salamon, all from the Milwaukee Institute of Art and Design
  • Safety Awards were presented to Formed Plastics and Gregstrom Plastics
  • Product Competition Awards were presented to Centro Inc. in the Innovative/State of the Art category for the Vector product, to Duracast for the Pilon Master in the Conversion Category, and to Roto Dynamics for Rowdy Hound, the Product of the Year.
  • Dru Laws and Tom Murdough were inducted into the Rotational Molding Hall of Fame.

You can view all of the Rotoplas photos on Facebook. If you need high-quality downloads, visit the photographer’s site and use the download PIN 8398.

Laws and Murdough to be Inducted in the Rotational Hall of Fame

ARM is excited to announce that Dru Laws (Tango Manufacturing) and Tom Murdough (Simplay3) have been elected to the Rotational Molding Hall of Fame. They will be inducted on September 23 at the ARM Annual Meeting/Rotoplas in Rosemont.

R. Dru Laws

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.

Tom Murdough

Tom Murdough
Tom Murdough is the innovative founder of Little Tikes, Step 2 Corporation, and most recently Simplay3 Corporation. Tom and his design team changed the face of the small household toy and the outdoor home playground markets and ultimately convinced many other molders that there was a business beyond tanks and simple moldings.

Murdough and his companies provided significant technical contributions to the global rotational molding industry, including pioneering the use of Teflon coating of molds and designing products that can be assembled with few or no fasteners. Through smart design techniques, Murdough inspired complicated mold designs that previously had been thought to be impossible. Little Tikes’ needs drove innovations in UV protection and color matrix developments for its outdoor products that all molders enjoy the benefits of today.

The Nomination & Election Process

  • Nominations for the Hall of Fame were collected from the industry throughout the Spring.
  • All nominations received from 2016 – 2021 comprised 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 narrowed the longlist to a shortlist of five nominees.
  • All Hall of Fame members voted on a ballot to elect two inductees from the shortlist.

More information on Rotoplas

Rotoplas 2021 FAQ

Rotoplas will be held September 20-23 at the Donald Stephens Convention Center in Rosemont, IL (a few minutes from O’Hare Airport). Learn more about the event.

Registration

Do I need to register?
This is our most frequently asked question. Yes, you need to register. Online registration is available here. You can register onsite at the Stephens Convention Center in Hall B beginning Tuesday, September 21 at 6:45 AM.

How do I get my badge?
Your badge is available in Hall B at the Stephens Convention Center. You can pick up badges from 7:00 AM – 5 PM on Tuesday, Wednesday, and Thursday.

What does my registration include?
This depends on the registration level you selected. (Check the confirmation emailed to you.) Annual Meeting includes exhibit floor, breakfast & lunch (Wed), welcome reception (Tues), supplier-sponsored reception (Wed), breakfast & lunch (TH), gala & awards dinner (TH). Exhibits Only includes the exhibit floor (Wed and TH). Spouse/Guest includes Welcome Reception (Tues), supplier-sponsored reception (Wed), gala & awards dinner (TH). Retired includes exhibit floor, gala & awards dinner (TH).

We offer three full- or half-day seminars for an additional fee that can be added on. Details on all education sessions are here.

Do exhibitors receive free registration with their booth?
Each booth includes four Exhibitor Personnel registration for employees of the exhibiting company to work the booth. Your exhibitor personnel only have access to events being held within the exhibit hall. Discount codes for these passes have been emailed to you. Contact staff if you have any questions.

Exhibiting companies also tend to register many employees for the Annual Meeting, which includes education sessions and many networking opportunities. One person from each exhibiting company is required to register for the Annual Meeting.

Schedule

When are the exhibits open?
The exhibit hall is open Wednesday 1:30 – 6:30 PM and Thursday Noon – 5 PM.

What’s the rest of the schedule?
The schedule is available here. The online schedule will be updated to include room numbers. The schedule will also be available in the show guide which is given to each registrant and there will be a schedule behind your name badge.

Is the meeting at the Hotel or the Convention Center?
Most of the meeting is held at the Convention Center.

Golf departs from the Hilton Rosemont Lobby. Tuesday’s Welcome reception, Thursday’s gala, and Friday’s Board meeting will also be held at the Hilton.

Everything else is at the Convention Center.

I need a break!
There are thirty-minute networking breaks in the middle of the general sessions and before the workshops. There will be coffee and other refreshments.

What’s the difference between the general session and workshops?
The general session is the only rotomolding programming Wednesday morning and for the first hour Thursday morning. All Annual Meeting attendees attend these sessions.

Multiple workshops run at at the same time Thursday morning. Annual Meeting registrants choose among seven workshops to attend during two time slots.

The Exhibit Hall

Who is exhibiting?
You can review a list of our exhibitors here.

Where is the Product Competition?
Along Row 600 near the ARM Booth and Presentation Theater. This year you will vote on your phone or on a tablet at the ARM Booth.

What if all this walking around makes me thirsty?
There will be cash bars on the floor for the entire afternoon. There’s a Starbucks in the convention center, just outside our Halls. At 5:30 PM on Wednesday, we’ll conduct a one-hour reception (with passed appetizers and open bar) in the Exhibit Hall.

When is exhibitor setup?
Monday 12:30pm-4:30pm, Tuesday 8:00am-4:30pm, and Wednesday 8:00am-11:00am. Most questions about exhibiting are covered in the Exhibitor Service Manual.

What is suitcasing?
Suitcasing is an unprincipled business practice in which  companies who are not exhibiting gain access to an event by obtaining event credentials (attendee badge, expo-only badge etc.) and then solicit business in the aisles or other public spaces used for the conference. Please note that while all meeting attendees are invited to the exhibit floor, any attendee who is observed to be soliciting business in the aisles or other public spaces, or any company’s booth will be asked to leave immediately. Don’t make it weird.

Travel

Can I get a hotel room?
Our room block at the Hilton is sold out but there are rooms available at our secondary block at Aloft

Is there a shuttle from O’Hare airport?
The Hilton Rosemont provides a shuttle from 5:00 AM – Midnight. Details here.

Aloft picks up at Door #3 at the :15 and :45 minute mark of every hour. It is on call after 10:30pm: (847) 671-4444

What are the COVID-19 precautions?
The State of Illinois mandated masks for indoor events regardless of vaccination status at the end of August. There is an exception for eating and drinking while stationary. The Convention Center will post whatever the local rules are at the time of our meeting.

Since our meeting is held in Rosemont, the City of Chicago travel guidance does not apply to our event.

What else?

What should I wear?
The meeting is business casual. Some people will wear blue jeans. Dress up a bit for Thursday night’s gala dinner.

Do Illinois restrictions indicate cases are especially high in Illinois?
Illinois cases are below the US average. Daily average cases in Cook Country (which includes Chicago and Rosemont) are 20 per 100,000 — compared to the U.S. average of 48 per 100,000. [This information is accurate as of September 1.)

What if I need help at the show?
Our registration staff will be able to answer many questions and can contact ARM staff for help. If there’s an emergency, contact security.

What can I buy at the ARM Booth/Presentation Theater?
A variety of ARM books, some rare rotomolding text books, t-shirts, cycling jerseys, and posters.

I’ve got some free time. What should I do?
Nearby Dining and Entertainment: Parkway Bank Park is right behind the hotel. The site features eight restaurants/bars, a comedy club, movie theater, and indoor sky-diving.
Shopping: The Fashion Outlets of Chicago is a multi-story mall that’s one big block away from the meeting. Approximately a 10-15 minute walk.
Get to the city: Take the Blue Line Rosemont station (a ten-minute walk from the meeting) to Chicago. Thirty minutes to hipster neighborhood Logan Square. One hour to downtown.
Chicago Dining: Your best close Deep Dish pizza option is Lou Malnati’s.  Gene and Judes (since 1946) is an authentic hotdog stand open late. Paradise Pup was featured on Diners Drive-In and Dives.

I have a question you didn’t answer!
Send an email. We’ll keep adding questions as the event gets closer.