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Electronics Industry
Edited by Professor Mauro Onori
1 Introduction
The assembly operation is a very important aspect of the manufacturing process. This process is required when two or more component parts are to be brought together to provide the finished product. In automated assembly ([1] Boothroyd, 1992), before parts can be put together, they often have to be loaded into a hopper, translated, singularised (each part separated from the bulk), appropriately oriented and discharged down a chute for the workhead to pick it up for assembly. The device performing this task is generally referred to as a parts feeder. The most commonly used automated parts feeder is the vibratory bowl feeder. For such a feeder, the path along which the parts travel is formed as a helix and is located around the inside wall of a cylindrical, bowl-shaped hopper which is secured to a heavy base by sets of inclined leaf springs. The bowl is vibrated by alternating the activation and deactivation at a certain frequency (e.g. 50 Hz) of an electromagnet mounted on the base, and a support system ensures that the resulting movement of the bowl is such a way that it provides torsional vibration about the vertical axis coupled with linear vertical vibration. All parts of the inclined track vibrate along a short, almost straight path, inclined to the horizontal at a greater angle than that of the track. The pushing action of the feeding parts at the bottom of the bowl and the vibratory motion cause feeding parts in the bowl to climb up the track to the outlet at the top of the bowl. Besides, the vibratory bowl feeder, many different types of non-vibratory feeders have also been developed such feeder for tubular parts ([2] Chua and Yeo, 1991), feeder for fragile parts ([3] Chua, 2006), reciprocating tube hopper feeder, centreboard hopper feeder, rotary disk feeder, tumbling barrel hopper feeder, centrifugal hopper feeder ([1] Boothroyd, 1992), etc.
Orientation is one of the most import tasks in automatic production ([4] Riley, 1996). Every item possesses six degrees of freedom in space. After orientation, it is restricted to only one degree of freedom as it travels to the exit of the bowl and down the chute for the next operation. Parts feeders...