Work cells work: Drilling Performance

Over several decades, precision part manufacturers have adapted to resource constraints, cost pressures and increasing global competition by embracing the principles of lean manufacturing. While lean manufacturing has many tenets, the primary focus is elimination of waste. Cellular manufacturing is one way manufacturers have sought to reduce waste in manufacturing processes.

Cellular manufacturing is no longer an innovative approach to manufacturing as it was a few decades ago. Many large and medium manufacturers have adopted it in some fashion, and automotive manufacturers exclusively utilize it.

Although cellular manufacturing is common, some people may not realize how it has transformed manufacturing and the benefits it provides.

Cellular manufacturing is a broad term encompassing many methodologies and philosophies. It generally combines all manufacturing processes needed to produce a product or family of products into a common area, which allows a person or small team to operate and manage the processes.

A work cell usually houses all processes used in the production of a single part. A good example is my former employer and the individual components it used to manufacture power steering gears. Steering gears are assembled from several major components, one of which is a rack bar. Rack bars are long shafts that must be turned, milled, broached, ground, heat-treated and polished. All these activities are completed in one cell. Bars enter the cell as cut blanks and leave as finished components ready for assembly.

In other situations, a cell may handle one manufacturing process that delivers multiple configurations of the same type of part. Another former employer in the aerospace industry built a cell to machine cast-aluminum flanges. These complex parts required milling, drilling, tapping, reaming and boring. In this case, machining operations were combined into one machine, a horizontal machining center, which allowed a machinist to produce the entire family of parts in one location and in any quantity needed. Prior to installing the cell, flanges had to travel around the shop, stopping at a few different machines, and were processed as a batch before moving to the next machine.

Manufacturing processes in an efficient cell have balanced cycle times so each process is completed in about the same amount of time. Line balance is the term that describes activities used to calculate, plan and build cells with balanced cycle times and efficient flow. When a cell is balanced, products arrive at a rate that satisfies demand with no more or less than is required. This is the foundation of just-in-time manufacturing.

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