Customer demands for shorter lead-times, high quality products and lower costs have prompted many companies to install manufacturing cells in their facilities. Recently, I attended the eighth annual Work Cells Symposium, sponsored by the Institute for International Research (New York, New York), and had the opportunity to meet many people from companies that had implemented manufacturing cells.
Large manufacturers such as Boeing, Raytheon, and Pratt & Whitney, as well as small manufacturers such as Wainwright Industries in St. Peters, Missouri; Lantech in Louisville, Kentucky; and St. Jude Medical in St. Paul, Minnesota; have reaped major benefits from manufacturing cells. In upcoming columns, I will discuss how some of these companies have used manufacturing cells to improve their operations.
What is a manufacturing cell? A manufacturing cell is a grouping of all the resources (people, supplies, machines, tools and equipment) required to manufacture a part or product. The cell resources are arranged in close proximity to enhance communication and allow everyone to see what is going on throughout the cell. The cell arrangement must be flexible enough to handle fluctuating production demands efficiently.
There are two types of cells:
- Product Cell—Provides a finished product to one or to a few customers. In a product cell, team members typically assemble, test, package, and even ship the product.
- Process Cell—Services multiple customers and completes multiple operations on a variety of products. A CNC machining center that can machine a number of parts completely is a type of a process cell.
What are the benefits of manufacturing cells? Manufacturing cells allow you to produce just what is needed with minimum materials, equipment, labor, time and space. This typically translates to lower operating costs. In addition, a cell has a simple and direct routing between operations, so bottlenecks can easily be identified and eliminated, reducing leadtimes. Next, because cells can accommodate small lots, quality problems are discovered and corrected sooner.
Cells help eliminate waste, especially:
- Excess Inventory—A cell will generate inventory only for the output being achieved. Because of a manufacturing cell's layout, excess inventory cannot be tolerated, as there is no place to put it.
- Waiting—Operators do not have to wait for supplies or tools as they are all kept in the cell ready for use.
- Motion—Workers need not move throughout the plant because everything they need to do their job is kept in the cell.
- Part Transportation—In-plant transportation is reduced, as there is no need to truck parts from department to department.
- Over-processing—Unnecessary operations (such as packing and unpacking for in-plant transportation) are eliminated in a cellular structure.
How do I get started planning a manufacturing cell? Ideally, all manufacturing operations should be contained in a cell. However, this may not always be practical. There may be some processes which are not feasible for inclusion in a cell.
Most companies follow the same methodology when implementing manufacturing cells. They start by looking at the existing process for making a product. This leads to construction of a process map. When mapped, the flow of a product through a traditional manufacturing process may resemble a "spaghetti diagram" with lines running in many directions, some even overlapping. The process map is useful in identifying excessive product movement, bottlenecks and non-value-added operations. The process map is then used to develop a cellular layout.
How can I measure the success of these cells? Key factors need to be measured and compared to pre-cell manufacturing processes. These factors are:
- Cycle time—The length of time from the point a part is ordered to the time it is shipped. In a manufacturing cell, cycle time closely matches actual production time because most of the queue time and travel time (up to 95 percent of cycle time) is eliminated.
- Total area allocation in square feet—A cellular operation requires less space.
- Number of times a part is touched—This is a measure of materials handling.
Can manufacturing cells work in my operation? Yes. Pick a product or process and you will see.