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Viscount Plastics : Moldflow
Moldflow customer Viscount Plastics (Victoria, Australia) is a member of the Pacifica Group and the largest injection molding company in Australia. The company was chosen by Dunlop Bedding to design and manufacture the tooling of 48,000 bed headboard frames for beds targeted for the Sydney 2000 Olympic Games athletes' village.
Dunlop Bedding, a division of Pacific Dunlop and the largest Australian manufacturer of beds, is a Viscount customer. Dunlop was awarded a contract to provide beds for the international sporting event. The beds were designed for use as single beds or to be stacked to form bunk beds, with the option of extending the length of the beds for use by the taller athletes. In addition to meeting the functional and structural requirements, Dunlop Bedding was also looking for an innovative design that included a modern shape and color. Dunlop Bedding decided to manufacture the bed frames in powder-coated steel and the bed headboard panels in translucent plastic with a choice of several bright colors. With this knowledge, Viscount Plastics recommended polypropylene homopolymer as the material for the bed headboard panels, since the material met safety, aesthetics, lightweight, low maintenance, ease of assembly, and cost effectiveness requirements.
Sweet dream designs
Since the translucent bed headboard panel became a highly visual, aesthetic piece of furniture, outward defects and/or warpage were absolutely not allowed. "We took advantage of Moldflow consultants' analysis expertise since we've worked with them on several Dunlop projects over the years. Their track record is second to none. They have assisted us with filling, cooling, and warpage analyses as important tools in the part and mold design phases. These were critical components for this projectís part and mold design phase. We decided that the ability to verify and optimize tooling and product designs early in this project would help us reduce lead time to manufacture, avoid start up problems, and reduce part reject rates," says Viscount product development manager Vadim Gershon.
For this project, Moldflow's Australian-based consultants became involved early at the product design stage to help optimize the part and tool design, and to verify cycle time and processing conditions. "We wanted to ensure that we could reduce lead times associated with the first acceptable prototypes so that Dunlop Bedding would have enough time to fine-tune other components to fit the bed headboard, if necessary, and supply beds in time for the Olympic Games," adds Gershon.
Viscount used Moldflow Part Advisers (MPA) software to verify the gate design and location, as well as to assess the fill pattern. Moldflow Plastics Advisers allows part and mold designers to take control of their designs early on, enabling every part and mold concept to be tested for manufacturing feasibility before the tool is cut, when the cost of change is minimal. Seamless integration with CAD solid models allows users to perform simulations and view results directly on the solid model. The software identifies critical manufacturability and quality issues and recommends appropriate actions to address those issues.
"MPA analyses confirmed that the area of the part at the end of the longest flow path would fill for the proposed cavity layout and wall thickness with the choice of polymer and gate locations," notes Derek Hain, Moldflow senior consultant.
Dunlop's original design of the bed headboard called for a three-piece assembly. Viscount's engineering team suggested the use of sliding cores driven by hydraulic cylinders to allow a one-piece bed headboard panel to be manufactured. Several iterative analyses were performed and it was determined that the panels could be produced as a single part instead of three separate components. Further analyses using Moldflow Plastics Insight (MPI)/FLOW, MPI/COOL and MPI/WARP were undertaken to verify cycle times and to ensure that the design specifications for dimensional tolerance, aesthetics, and negligible warpage were met.
"MPI/COOL was used to verify and optimize cooling line layouts and confirm that the processing conditions suggested by Viscount Plastics could be used," adds Hain. The results from MPI/WARP indicated that there would be very little warpage since the fill pattern and the cooling lines had been optimized by then. "The predicted warpage was negligible and could be further reduced with fine tuning of the injection molding machine settings and tool temperatures during manufacture," adds Hain.
The initial mold trials undertaken in November 1999 showed that the actual cycle time was very close to that predicted by Moldflow's software, and the parts produced met design specifications. "Preliminary work conducted jointly by Viscount's engineering team, Moldflow's consultants, and Moldflow software, as well as excellent tool making by Centre Tooling, allowed us to achieve a near-perfect part at the very first die trial. We saved at least one tool rework and subsequent die trial, which could have cost us several thousand dollars and increased lead time by up to 20%" explains Gershon.
For more information about Moldflow, visit www.moldflow.com. Visit www.viscount.com for information about Viscount Plastics and www.sleepmaker.com for information about Dunlop Bedding.
Author: Laura Carrabine