Integration: Batch, Dial, and Conveyor
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Almost intrinsic to any assembly problem is how material flows into and out of the application zone.
Traditional batch mode systems are most cost effective in low production runs that require high change-over including many custom or adjustable pallets. While it is possible to convert batch mode systems to conveyor based systems, purpose-built conveyor systems are going to be optimal for throughput. Tools such as hoppers, magazines, matrix trays, vibratory bowls, and even multiple heads can help, but it is difficult to recapture productivity gains attributable to dial and conveyor systems with their typical one second dial index times and two second pallet transfer times. And of course all of the batch-mode optimizations can be for the most part brought to dial and conveyor applications.
Batch mode systems usually factor in a five to ten second part changeover time. While improvements can be made with 180 degree indexers and shuttles, the additional costs and the fact that these limit the integration of additional production steps make investment in these tools a limited proposition at best.
Dial mode systems are the most restrictive, limiting the size of the work area and fixturing must be general enough to accomodate all permutations, but these systems offer the highest throughput. Index times can be one second or less and usually no additional rotational-translational adjustments need to be made at the individual stations although often z-probing is still necessary. Dial systems can be restrictive on part size as well as each part must sit in a "pie-slice" of the dial.
Dial mode systems often (but not always!) require dedicated fixtures, welded steel frames and precision machine locations, significantly increasing their cost. However this cost becomes amortized over the higher production rates and so as long as annual production levels are there, dial systems provide the highest return on investment.
Conveyor based systems offer the best compromise: you dont get the throughput of a dial system but you get more flexibility. Flat belt conveyor systems are the most flexible, but usually require rotation-translation adjustment once the part gets into the work envelope. This can be done with push bars and shot pins, or with vision. Cam driven index belts can often be made to an accuracy that does not require further alignment, but now require the expense of dedicated fixtures.