| Compiled By Don Rosato
Advanced Plastics In-Mold Assembly
TRW Advanced Plastics GmbH & Co. KG's patented in-mold assembly (IMA) injection molding procedure, allows the company to produce complex plastic parts with mechanically connected individual moveable components by intentionally using incompatible plastic materials. All components of a tool are manufactured in a single cycle with a solitary injection mold machine. Dissimilar materials with different melt temperatures ensure no bonding between successive shots. The technology can be used to produce articulated appliance air flow louvers and electromechanical hinges.
|
Injection Molded IMA Appliance Parts
(Source: TRW Advanced Plastics )
|
TRW Advanced Plastics is involved principally in engineered fasteners and components and produces a number of different industrial products. The reduction in assembly effort with in-mold assembly is particularly apparent with production of industrial cold storage refrigerator air diffusers for Whirlpool, Electrolux, and Lucky Goldstar. TRW's in-mold assembly product used for the air diffuser reduces independent parts by more than 50% with concurrent increased precision of the finished assembly.
The company uses TRW Advanced Plastics Technologies' specialized injection molding knowledge to create perfect fit components for most industrial sectors such as a crankshaft smaller than 1cm with a flexible connecting rod that TRW developed for use in an electric toothbrush appliance by one of the leading manufacturers, Oral-B, or as an oven control housing for use by Miele and KitchenAid. Using a 2x2-cavity tool two materials are molded into two parts of a housing for an oven control, produced as a two-piece assembly consisting of a tubular housing with a freely rotating shaft inside. Until TRW redesigned it for in-mold assembly, the component consisted of three molded pieces and two metal screws that required three molds, three machines, purchased screws, incoming and intermediate part warehousing, an assembly operation, and much intraplant movement of parts. That is now all accomplished inside the mold, allowing the separate assembly process to be eliminated for different end products. TRW says overall accuracy of the finished assemblies is very high.
|
Appliance Oven Control Receptacle
(Source: TRW Advanced Plastics) |
Advances in Multi-Material Molding
Injection molding machine and mold makers say multi-material molding demand in North America is still less than 10% of their sales. But while multi-material molding in North America lags significantly behind that in Europe, the technology is attracting increasing attention in North America driven by growing Asian competition. Injection molders are recognizing that the elimination of capital and operating costs for downstream equipment, made possible by producing a finished part in the mold, can result in significant savings. With less part handling, manufacturing cycle time may be reduced by as much as 20%, and total assembly costs may also be reduced by 15% or more. Additionally capital investment for a job may be cut by up to 25% as a result of using just one machine and mold instead of two.
Milacron states that in the U.S. multi-molding machine quotes have increased to 15% of the total for their injection molding machines, whereas over 20% of the company's sales in Germany are for multi-material units. Arburg also sees growing interest. Other companies in the U.S. are also noting growing interest in multi-material molding. MGS Manufacturing Group needed more space to meet growing demand for multi-material molding equipment produced by its Universal Multishot Systems division. The Universal Multishot business which makes portable, bolt-on injection units, rotary indexing plates, rotating platens, and other multi-material molding equipment has moved to a dedicated, 12,000 sq. ft. structure to keep pace here.
Multi-material molding is evolving in new directions. Recent developments include larger machines with more cavities, larger parts, and more combinations of materials. Some presses are being equipped with four to six injection units, or for thermoplastic/thermoset combinations. Sophisticated rotating tools allow for in-mold assembly and finishing while other multifaceted tools produce parts with combinations of multiple materials using water injection technology or gas assist, and novel uses for coinjection that go considerably beyond imbedding recycle plastic material within a plastic part.
|
Large Stack Turning 32-Cavity Mold, for 3-Component Deodorant Roller
(Source: Foboha GmbH)
|
The Injection Molding Machine as Manufacturing Cell
The injection molding machine's role in production has being expanded through the addition of various secondary processes into the mold, to become a manufacturing cell. Traditionally, the injection molding machine was a single cog in a value-added process, responsible only for molding. Now that machine is being transformed from a segregated operation into the hub of an integrated processing system that produces value-added subassemblies or finished products rather than a range of individual parts requiring secondary assembly. It is increasingly common for multi-component molding, in-mold assembly and/or other operations to be incorporated into one machine, thereby reducing the machines, operators, auxiliary, and assembly equipment required. This ability to incorporate secondary operations into the molding machine, through the use of innovative tool designs reduces manufacturing costs, improves quality and creates new opportunities for molders. The technology also allows molders to maximize production with existing equipment, and the added flexibility from interchangeable mold cavities allows molders to add printing, welding, painting, assembly, or other secondary processes in the tool. The expanded role of the injection molding machine is finding applications in appliance, medical, personal care, packaging, and other markets including even large part automotive areas.
|
