Establishing Manufacturing Cells

Last month, I discussed how manufacturing cells can reduce or eliminate the major wastes inherent in a manufacturing operation. The logical grouping of all the equipment required to make similar parts is an effective technique for addressing the problems of overproduction, excess inventory, over- processing, motion, waiting, transportation, defects and order tracking.

Columns From: 5/2/2005 Modern Machine Shop,

Last month, I discussed how manufacturing cells can reduce or eliminate the major wastes inherent in a manufacturing operation. The logical grouping of all the equipment required to make similar parts is an effective technique for addressing the problems of overproduction, excess inventory, over- processing, motion, waiting, transportation, defects and order tracking. Recognizing the advantages that manufacturing cells offer, I would like to describe a simple, yet effective, seven-step approach to establishing manufacturing cells in any type of operation.

Step 1: Identify candidates for cellular manufacturing. The objective of this step is to group products with similar manufacturing processes into product families. There are many ways to identify these families. Perhaps the simplest method is using a matrix that lists products and processes employed. A matrix will provide a visual representation of the relationship between products and processes, allowing for easy recognition of the parts that undergo the same, or substantially similar manufacturing processes.

Step 2: Determine demand for the products. When analyzing the demand of products planned for a cell, there are three demand figures that are important to note. The first is the average demand. This is probably the most meaningful number in cases in which the demand is "relatively" consistent. However, in cases in which the demand fluctuates significantly (as in seasonally or cyclically dependent products), it is useful to review the minimum and maximum demand levels. Once the demand level has been determined, it should be tied to the capacity of the cell. The most effective way of representing this relationship is a concept called the rate of customer demand or TAKT time. TAKT is determined by taking the available working time and dividing it by the demand for that period. For example, if the demand for an 8-hour shift is 400 parts, then TAKT = 480 minutes per shift ÷ 400 parts = 1.2 minutes per part. This means that the cell must be capable of completing a part every 1.2 minutes.

Step 3: Review the work sequence. When planning the cell, we need to understand what is really going on in the manufacturing process. Often, what we think is being done is different from what is actually occurring. To get an accurate picture, observe the process and divide it into meaningful elements or tasks. Identify each task as either value added or non-value added. If the process includes automated tasks, pay special attention to equipment capacity, cycle times, change-over times, and downtime issues.

Step 4: Improve the process. Before implementing a cell, an attempt should be made to improve the process. For one, because of the close proximity requirements of a cell and the desire to make one and pass one part, some material handling processes currently employed will be either eliminated or modified. Therefore, it is best to design the manufacturing cell with these changes in mind. In this step, we should consider which processes can be eliminated; which should be changed; whether the sequence of activities should be rearranged; and where we can combine steps. In addition, we should search for opportunities to simplify tasks with better tooling, more efficient equipment or improved documentation.

Step 5: Balance the process. In this step, we attempt to balance the process so that all tasks take approximately the same amount of time. This balancing can be done after tasks are improved (in the prior step), or it can be accomplished through altered staffing levels. After all improvements are made, a longer task may simply require more personnel in order to keep the product moving through the cell (and meeting TAKT requirements).

Step 6: Design the cell layout. At this point, it is time to design the actual cell layout. The area required, the amount of people needed, and the type and quantity of necessary equipment all need to be addressed. The key to a successful cell is flexibility; so when finalizing a cell layout, consider changes that might be expected in demand, product design, manufacturing technology and more. Recognizing the need for a cellular layout to be responsive to change will keep you from designing a layout that is too rigid.

Step 7: Plan the implementation (and implement). We can now roll out the cell, but we need to plan for an orderly transition to this new way of making our products. Part of this transition must include education and training of all who will be part of the cell. The physical transformation also needs to be planned, and the movement of equipment and modification of utilities should ideally be completed during off-hours. All of these aspects need to be formalized and reviewed by all affected parties.

Consider this approach to introducing cells and realize the benefits that they offer.

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