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It has to be flexible
Lower production volumes and the outsourcing of high-volume part manufacturing to first and second tier suppliers have forced a move away from reliance on fixed transfer lines to more adaptable equipment. Manufacturers want to be able to modify their equipment to handle production changes at minimal cost. They also need a very reliable crystal ball to second-guess both economic conditions and the buyer's whims when planning. The question is, how prepared can they afford to be?
Conventional transfer lines are still a mainstay in some industries, chiefly those that are automotive-related. When production runs are in the millions over several years, it's economically feasible to accept the cost of a fixed transfer line with a multimillion-dollar price tag. But for lesser volumes, the strong preference is for system flexibility, which can be achieved by:
*Revising the manufacturing system by adding or removing machines and changing processes,
*Modifying existing equipment by alternations of such things as number of spindles, pallet type and configuration, fixtures, part flow, and the balance between manual and automated operations,
*Trying a little of both.
Here's how several machine tool manufacturers tackle this problem.
"Agile systems are hot," says Horst Roman, director of engineering, Cross Huller (Sterling Heights, MI). "Cross Huller agile systems can handle volumes of around 200,000-350,000 parts per year in a sequential process with six to eight high-speed Specht machining centers in a cell. They are loaded using an overhead gantry with an automatic interconnecting system to transfer parts from machine to machine within a cell, and between cells. Each cell is normally dedicated to a specific operation, based on either the number of spindles needed or the type of fixture required. Cells are sequential and machines within a cell are parallel. A typical production module produces approximately 325,000-400,000 parts per year. Higher volumes are accommodated by adding additional modules." To date, Cross Huller has provided what is said to be the world's largest agile manufacturing system comprising four modules of 39 machines each, producing 1.3 million cylinder heads per year.
In defining high volume, Mark Tomlinson, director of proposal & estimating, Cincinnati Lamb (Chesterfield, MI) says, "High volume is anything over 75,000 units per year."
Transfer machines may be part of the...