Moulding analysis software eliminates tool rework

Designing moulded parts for manufacturing that are right first time is not easy. Dean Palmer reports on analysis software that lets engineers test virtual designs on their desktops

Design engineers, particularly mould tool designers, need to be able to quickly verify their mould concepts and manufacturing feasibility before the actual tool is cut, when the cost of change is minimal. Getting a mould design ‘right first time’ is not easy but there is now software out there that can help.

Canadian companies DW Product Development and Camalor are both subcontract design firms for DIY manufacturing giant Black & Decker. In a recent project to re-design Black & Decker’s existing Workmate product, DW created a new design that included handles and wheels to make it easier to move the product around and folds for quick and easy storage. But because DW designed the parts as injection moulded parts rather than the traditional wood laminate, the design team added other moulded-in features such as colour, measuring rulers, tool storage holes and pocket recesses for nails and screws.

During the project, DW used ‘Moldflow Plastics Advisor’ (MPA) software from Moldflow Europe, for plastic injection moulding analysis, and Solidworks and Pro/Engineer software for 3D CAD modelling. MPA allowed the users to test every part and mould concept for manufacturing feasibility before tools were cut. And integrating this software with the 3D CAD packages meant that designers were also able to perform simulations and view results directly on the solid model.

DW’s senior product designer and plastics applications specialist, Aldo Balatti commented: “We used the [MPA] software to reduce trial and error, improve part design and quality and slash time-to-market. It’s a powerful tool to optimise parts and improve plastic processing conditions. We have been able to save time and money by reducing or eliminating tool re-work. We use MPA on the majority of parts that we design to obtain fast feedback on wall thicknesses, weld-line placements, material selection and gate locations.”

Balatti went on to say that his company wanted to make sure that each new part was designed correctly and was ready for production prior to being sent to the mould maker. He said there is usually no time to make changes with the mould after this stage. “Using MPA and our own expertise, we have eliminated the mould trial and error phase from the moulding process,” he added.

“We tested the jaw parts we designed by quickly creating CNC-machined polypropylene prototypes. Eventually, because of plastic creep, we felt it was necessary to put a small metal stiffener inside each jaw to resist creep that would occur, if for example, a heavy object was left on the Workmate for a long period of time,” said Balatti.

That’s not all though. For the gating solution, MPA also showed that the handle area, rather than the end of the jaw, was the ideal location. This cut the flow length in half and eliminated any knit lines and cosmetic issues.

The design engineers at DW also worked closely with PolyOne, the polypropylene resin supplier for the new Workmate plastic parts. DW’s team requested more advanced simulation software from Moldflow – Moldflow Plastics Insight (MPI) – to perform mould filling and warpage analysis. The results of these simulations using MPI were almost identical to DW’s MPA calculations, confirming that the handle gating location was the best option.

Marc Fortin, engineer at Camalor, told Eureka: “In terms of the vice jaw, when we first considered it as a plastic part versus a wooden part, we initially thought that it would run as a 80 to 90-second cycle time. That was unacceptable from a capacity point of view. We couldn’t produce enough vice jaws in the time frame required with the tooling that we had budgeted for. Moldflow analysis software helped to cut the cycle time to one minute to meet the capacity and delivery requirements.”

Tom Shelley

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