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Handbook of Materials for Product Design Part 14

Tham khảo tài liệu 'handbook of materials for product design part 14', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Plastics Joining Materials and Processes 11.31 Excellent Good Fair Poor Material 10 9876543210 Amorphous Polystyrene SAN NAS and ASA ABS Phenylene-oxide based resin Acrylic Polycarbonate Polysulfone Crystalline Nylon Polyester Acetal Polyphenylene sulfide Polypropylene Polyethylene Fluoropolymers Source Branson Sonic Power Co. Figure 11.9 Ultrasonic weldability index for common thermoplastics.17 Common ultrasonic welding joint designs are shown in Fig. 11.10. The most common design is a butt joint that uses an energy director. This design is appropriate for most amorphous plastic materials. The wedge design concentrates the vibrational energy at the tip of the energy director. A uniform melt then develops where the volume of material formed by the energy director becomes the material that is consumed in the joint. Without the energy director a butt joint would produce voids along the interface resulting in stress and a low strength joint. Shear and scarf joints are employed for crystalline polymeric materials. They are usually formed by designing an interference fit. Ultrasonic welding can also be used to stake plastics to other substrates and for inserting metal parts. It can also be used for spot welding two plastic components. Figure 11.11 illustrates ultrasonic insertion swaging stacking and spot welding operations. In ultrasonic spot welding the horn tip passes through the top sheet to be welded. The molten plastic form a neat raised ring on the surface that is shaped by the horn tip. Energy is also released at the interface of the two sheets producing frictional heat. As the tip penetrates the bottom 11.32 Chapter 11 TABLE 11.7 Compatibility of Plastics for Ultrasonic Welding15 ABS ABS polycarbonate alloy ABS PVC alloy Cycovin Acetal Acrylics Acrylic multipolymer Acrylic PVC alloy Kydex ASA Butyrates Cellulosics Modified phenylene oxide Nylon Polycarbonate Polyethylene Polyimide Polypropylene Polystyrene Polysulfone PPO PVC SAN-NAS I I Compatible substrate .