Cemre Ablay 030060150 7th Week

Induction Welding: (27 March 2011, 1:10 pm)

Induction welding uses induction heating from high radio frequency alternating current to magnetically excite ferromagnetic particles embedded in a bonding agent (with a thermoplastic or matrix) placed at the joint interface of the two parts being welded. The heat released is used to melt and fuse thermoplastics, to heat hotmelt adhesives, or to provide rapid adhesive cures for thermosets. It is a reliable and rapid technique, ranging from fractions of a second for small parts to 30-60 seconds for parts with long (400 cm; 157 in.) bond lines, and results in structural, hermetic, or high- pressure welds.

(Plastics Design Library, Handbook of Plastics Joining: A Practical Guide, p.67)

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Ultrasonic Spot Welding: (27 March 2011, 03:24 am)

Ultrasonic spot welding joins two thermoplastic parts at localized points without a preformed hole or energy director. It produces a strong structural weld and is especially suitable for large parts with complicated geometry or hard to reach joining surfaces. Spot welding lends itself to sheets of extruded or cast thermoplastic and is often used on vacuum-formed parts, such as blister (clamshell) packaging.

(Plastics Design Library, Handbook of Plastics Joining: A Practical Guide, p.61)

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Ultrasonic Staking:(27 March 2011, 03:43 am)

In ultrasonic staking, a thermoplastic stud is melted and reformed to mechanically lock another dissimilar material (usually metal) in place. Staking provides an alternative to welding when the two parts are to be joined are made of dissimilar materials that cannot be welded or when simple mechanical retention of one part to another is adequate. Advantages of staking include short cycle times, tight assemblies with virtually no tendency for recovery, repeatability, design simplicity, and the elimination of consumables such as screws, rivets, adhesives and fasteners.

(Plastics Design Library, Handbook of Plastics Joining: A Practical Guide, p.61-62)

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Shear Joint:(27 March 2011, 03:43 am)

The shear joint is used in welding semicrystalline materials that have a sharp and narrow melting point. Energy directors are not useful with crystalline materials because material displaced from the energy director either degrades or recrystallizes before it can flow across the joint interface and form a weld. The small, initial contact area of the shear joint is the first to melt during welding; melting then continues along the vertical walls as the parts telescope together in a smearing action that eliminates exposure to air and premature solidification. Strong hermetic seals can be obtained. Rigid side wall support is necessary to prevent deflection during welding, and the walls of the bottom section must be supported by the holding fixture. The top part of the joint should be as shallow as possible, similar to a lid, but of sufficient structural integrity to withstand internal deflection. Shear joints provide part alignment and a uniform contact area.

(Plastics Design Library, Handbook of Plastics Joining: A Practical Guide, p.49)