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The focus of this case study is a manufacturer of wood caskets. The company produces about 3,000 units per day using several different species of wood and making two different models, full-top and cut-top. Most of the caskets have cut-tops, which consist of caps cut into two portions to allow just the head end of the casket to be opened (see fig. l). Several quality problems are encountered, however, one of the greatest being misaligned caps. The caps, placed on the shell of the unit by way of foul hinges, are often skewed on the shell, creating problems down the assembly line. It is believed that the misplacement of the hinges lies at the root of the problem.
The placement of the hinges on the shell itself is a reliable process. The holes for the hinges are drilled into the shell by a machine that has proved to be consistent. This study focuses only on hinge placement on the caps, for which no holes are drilled. The hinges are placed in relation to "dimples" on the rim of the cap, which are indented before the caps are cut and sanded. The amount sanded off each cap varies from one species of wood to another. We evaluate this and other aspects of the cap-to-shell process to account for these variations and attempt to ascertain the consistency and reliability of the present processes.
UNDERSTANDING THE OPERATION
It is common practice for other companies to drill holes before the hinge screws and the hinge are assembled to the cap. This step guards against splitting and misdirected screws and allows the placement of the screws to be better controlled. To fully understand this, one must first visualize the operation:
A cap is automatically carried across the band saw-- butt sander (BSBS) machine, which cuts the cap at the specified place (which is constant on all cut-tops) and sands the butt-ends of the caps where they have been cut (see fig. 2). The operator then pushes the dolly containing the cap, as two pieces, across tracks on the floor to the conveyor line carrying the shells. The dolly is pushed up against the shell; the cap is already at the right height. The hinges are placed on the rim...