Injection molding and metal fabrication combined
Mark M. Matsco
Manager, Innovative Applications Group
Bayer Polymers Div., Pittsburgh, PA
Hybrid technology for metal/plastic composites--a project in which Bayer invested heavily--has now become established on the market. The technique represents the ideal combination of sophisticated injection molding technology and economical metal fabrication, resulting in a synthesis of materials and processes.
First examples of the technology debuted at the K'95 show in Dusseldorf, Germany. The application involved functionally integrated crossbeams, front ends, and seats and doors from the automotive sector. The economic advantage of the technology stems from the high level of integration of functions in the complete module. The process also offers lower weight and less material input, thanks to the carefully calculated combination of material properties.
An important advantage of the plastic/metal composite technique is that the buckling resistance of thin sheet-metal profiles can be improved with properly placed ribbing. When designing the composite structure, it is possible to locate ribs at high-stress areas in order to better distribute the loads. In regions having high torsional loading, a cross-ribbed pattern with increased wall thickness can be used. In other areas, simple V-ribbing may suffice.
The technology also has advantages in flexure and axial compressive loading. Using flexural load capacity as a measure, it becomes clear that, under a localized force, the closed profile fails by buckling earlier than the composite. A weight-normalized comparison between a hat, box, and composite profile resulted in respective ratios of 1:1.5:2.
To speak with a Bayer application engineer, call (412) 777-2000.
Pulse welding offers bonding alternatives
Wendell Johnson and Michael van Haaren
Process Equipment Co., Tipp City, OH
Materials that are considered non-weldable often hinder the best solutions to an engineer's design challenge. A new process called high speed pulse welding allows product designers to specify innovative materials to solve design challenges.
High speed pulse welding is a form of resistance welding. It achieves a bond within milliseconds at very high current levels by using capacitor-stored energy. The capacitors are charged to voltages of approximately 3,000V and are fed to special impulse transformers. There, the energy is converted to high current and low voltage.
When the pulse is initiated, the components begin to fuse. The weld energy is focused into the interface region by appropriate projection design, and the material in this region heats up rapidly. Due to the high surface pressure, the resulting plasticized material is squeezed out from the contact area, and the components migrate together and are forge-welded.
Due to the low heat input and rapid cooling rates of high speed pulse welding, the heat-affected zone is extremely small (about 0.5 mm) relative to other welding methods. High speed pulse welding makes it possible to weld a large assortment of materials including exotic and dissimilar materials. The process is especially well-suited for high carbon materials and many combinations of powder metal parts.
The process creates a diffusion-type weld with minimal part heating. Parent metal strengths are achieved even for vast thermal conductivity variation or dimensional differences.
To reach a Process Equipment applications engineer, fax (513) 667-9322.