As Published In Design News
Youngsters enjoying playground slides may never thank Meese Orbitron Dunne, but they should. The plastics molding company based in Saddle Brook, New Jersey, is producing a one-piece, 360-degree slide bedway for Playworld Systems that is safer and more durable than steel and much cooler. It’s also less bumpy than a sectionally-assembled slide. And as any kid on a hot, steel slide in a playground will tell you, a smooth slide that’s cool is “way cool!”
And that’s cool, too, with the people at Playworld Systems, New Berlin, Pennsylvania. Playworld, which has been bringing innovative products to playgrounds for more than a quarter century, approached Meese Orbitron Dunne (MOD) with a challenge. Could they produce Playworld’s new, one-piece, 360-degree spiral slide? MOD, an innovating specialist in rotomolding, not only could, but did, and in an astonishing 16 months from concept to shipping the finished product.
Of course, MOD was already producing 270- and 360-degree slide beds for Playworld, using a medium-density polyethylene, in seven UV-inhibiting colors, but these were rotomolded in sections. Playworld felt it was time to introduce a better product, one that had greater integral strength, fewer assembly points, didn’t collect dirt in joints….and provided a smoother ride.
Then, engineers and designers from MOD, Playworld and tooling manufacturer Wheeler-Boyce began brainstorming together to come up with manufacturing parameters. These parameters also had to meet the restrictions of existing technology, a state-of-the-art Ferry 330 rotational molding machine. And in order to include the new slide in the next Playworld catalog, MOD was faced with an extraordinarily tight deadline.
“We went from concept to finished product so quickly because every participant had input on every part of the project right from the beginning,” explains Bob Dunne, General Manager, Rotomolding at MOD’s Ashtabula, Ohio plant.
The weight limitation of the Ferry 330 is 2,300 pounds. The cast aluminum mold weighed 1,200 pounds. The resin would weigh 200 pounds. Thus, the spider could not weigh more than 800 pounds. (“Spider” is the term for the tooling support framework which encases the molten plastic during molding and looks very much like a gigantic spider.)
“Supporting a 1,200 pound mold seven and a half feet tall and five and a half feet in diameter is not an easy task to begin with,” said Dave Ralston of Wheeler -Boyce. “Every structural member had to be scrutinized for size, weight, structure and loading.” Common spider materials were replaced with different shapes and wall thicknesses for maximum performance. Each shape matched the position and loading of every member. The final spider weighed in at just over 700 pounds.
In June, the Playworld design team, led by Mike Griffin, Design Engineer, created a three-dimensional solid model of the 360-degree slide using Pro-Engineer software by Parametric Technologies. The slide is designed to carry the load through the homogeneous outside wall and center support post. The bedway is a wide, deep catinary hung between the two supports. Unlike steel slides which have a flat bedway and sharp bends and do not carry a load or stress very well, the Playworld design spreads stress equally within the bedway. Threaded inserts (the “nuts” of the bolted construction) were molded directly into the plastic to eliminate hardware and clumsy pockets of bolt-through connections. The custom-designed and machined-threaded inserts deliver 1.5 times greater pull-out strength and 2 times greater torque strength than commercial inserts.
By August, they were ready to make the models needed for the tool. Tooling started in October and by March, 1995 work began on the spider. This immense tooling support framework required a custom-made cradle to ensure its safety during storage and transportation. In May, 1995 the first prototypes came out of the molds, with a little “persuasion.”
During the prototype phase, workers began the process of removing the molded slidebed from the tool. Because of its unique, one-piece spiral configuration, it caught on a corner of the tool and could not be removed whole. Or so it seemed. Wheeler-Boyce engineers returned to their drawing boards and succeeding inmaking modifications to the tool to permit safe removal of the slidebed. By June, 1995 the 360-degree slidebeds were coming off the production line at a regular clip.
From the beginning, packing, shipping and handling were built into the design concepts. Custom-fabricated skids, boxes and wrappings were designed so the product could be moved within freight terminals and onto trucks without damage during delivery to playground sites.
Playworld Systems’ 360-degree slidebed is less expensive to produce than sectionally-molded slides, but the dramatic returns come during installation. Playworld Systems’ designers had practiced installing conventional slides so they could understand the complexities of the operation. Conventional slides often require heavy lifting equipment and can take over five hours to stand up. The entire slide unit with the new, one-piece slidebed requires only one concrete footing instead of three and can be put up by a three-person crew without using cranes or tractors in around two hours. Installing the new slide is also far safer for the crew.
For guidance in custom molding large parts, call 800.772.POLY (7659).