A Primer On Lean Manufacturing Techniques

In last month's column, I described the value stream mapping process and how it is a natural first step in identifying opportunities to streamline the manufacturing process. Once you recognize the areas for improvement, you need to understand the lean manufacturing techniques that can help.

Columns From: 11/1/2002 Modern Machine Shop,

In last month's column, I described the value stream mapping process and how it is a natural first step in identifying opportunities to streamline the manufacturing process. Once you recognize the areas for improvement, you need to understand the lean manufacturing techniques that can help.

The are many techniques associated with lean manufacturing, including workplace organization and visual management, quick changeover (otherwise known as setup reduction), point-of-use storage of parts, quality at the source, standardized work procedures, cellular manufacturing, and pull scheduling. I have spoken about a number of these techniques in previous columns, but let me briefly summarize them for you now.

Let's start with workplace organization and the use of visual techniques for effective management of the workplace. If we can effectively organize our work areas, we can eliminate a great deal of time spent looking for things. An organized workplace is one that complies with the "30-second rule." This rule states that anyone should be able to find anything within 30 seconds (think whether you and your co-workers can do this now). The 5S system of workplace organization (sort, set in order, shine, standardize and sustain) emphasizes removal of what is not used and employment of shadow boards, signs, areas boundaries, labels, and more to help everyone find what is used.

Quick changeover, or setup reduction, is a systematic means of reducing the time a piece of production equipment is down, when changing from one product to the next. Changeover time is defined as the time from the completion of the last good piece of one job, to the first good piece of the next job. The main components of changeover time are 1) Preparation (clean up the work area and get paperwork, materials, tools and so on); 2) Removal and mounting of parts, tools, fixtures and equipment; 3) Measuring and setting the equipment; and 4) Making trial pieces and adjusting where necessary. By watching and analyzing current changeover procedures, we can find ways to reduce each of these components and minimize equipment down time during the process.

Point-of-use storage of parts means that every part needed to do a job is stored in the area that uses it. This will require some management discipline, especially when inventory items are involved, but the storage of parts at their point of use offers reduced search time, minimal travel and material handling, and simplified storage.

Quality at the source means that employees are certain that the products they are sending to the next workstation are correct. To implement quality at the source, employees must be given the means necessary to ensure the parts are good. Gages, tools and other inspection equipment can help, as can sample parts, mating parts, pictures and other visual items.

When we are talking about standardized work procedures, we mean that tasks are organized in the best sequence to ensure products are being made the best way every time. Standardized work procedures bring consistency (and as a result, better quality) to the workplace, and therefore they should be documented and given to anyone charged with completing the task.

Cellular, or flow, manufacturing is when all of the resources required to complete the product are grouped together. Cellular manufacturing is the opposite of the traditional departmentalized layout, in which all machines of the same type are grouped together. In a cellular arrangement, a company may have equipment such as CNC lathes, milling machines, grinders, vibratory finishing machines and parts washers all located in the same area. Furthermore, assembly operations are often completed within a cell. Manufacturing cells are frequently organized in a U-shape so that operators can manage different machines. A cellular layout can more easily accommodate a single piece flow by eliminating the handling and queue times inherent to a traditional departmentalized layout.

A pull scheduling system emphasizes replenishment of what has been consumed. Another way to describe a pull system is to make only what you need, and no more. A pull system typically uses some type of visual signal, such as an empty box, open space, or flashing light to initiate the part replenishment process. A pull system will control and balance the resources required to produce a product and is effective in reducing non-value-added activities.

With a basic understanding of these lean manufacturing techniques, you can determine the ones that can help you improve your overall operation and start putting them to use today.

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