Cellular Manufacturing: An Integrated Model of Manufacturing Excellence
Cellular Manufacturing is a technique for producing similar products using cells, or groups of team members, workstations, or equipment, to facilitate operations by eliminating setup and unneeded costs between operations. Cells might be designed for a specific process, part, or a complete product.
They are favorable for single-piece and one-touch production methods and in the office or the factory. Because of increased speed and the minimal handling of materials, cells can result in great cost and time savings and reduced inventory. Cellular design sometimes makes use of group technology, which studies a large number of components and separates them into groups with similar characteristics.
They also uses families-of-parts processing, which groups components by shape and size to be manufactured by the same people, tools, and machines with little change to process or setup. Irrespective of the design of cell (straight line, u-shape, or other), the equipment in the cell are placed very near one another to save space and time.
In cellular design, the handling of materials can be by hand, conveyor, or robot. A cell supervisory computer must be used to control movement between equipment pieces and the conveyor when robots or conveyors are used.
Meaning of a Cell
A cell refers to a combination of people, equipment, and workstations organized in the order of process flow, to manufacture all or part of a production unit. The features of a cell include the following:
- It is made up of very small lot, flow.
- It is often required for a family of products.
- It has equipment that is right-sized and very specific for this cell.
- Is usually arranged in a C or U shape so the incoming raw materials and outgoing finished goods are easily monitored.
- Have cross-trained people for flexibility.
Objectives of cellular manufacturing
The following are some core objectives of cellular manufacturing:
- To reduce manufacturing lead times. This can be achieved by reducing setup, work part handling, waiting times, and batch sizes.
- To reduce Work in Process (WIP) inventory. Smaller batch sizes and shorter lead times reduce work-in-process.
- For improvement of quality. This is accomplished by allowing each cell to specialize in making a smaller number of different parts thereby reducing process variability.
- To simplify production scheduling. The system simply schedules the parts, rather than scheduling parts through a sequence of machines in a process-type shop layout,
- To reduce setup time. Accomplished by using group tooling (cutting tools, jigs, and fixtures) that have been designed to process the part family rather than part tooling, which is designed for an individual part. This reduces the number of individual tools required as well as the time to change tooling between parts.
Steps for Implementation
After mapping out your value streams, you are ready to setup continuous flow manufacturing cells. Most cells that have been set up in the past ten years do not have continuous flow; most changes to cells have been a layout change only. That is, machines were moved in a cellular arrangement and nothing more was changed. It should be noted that change in layout alone does not create continuous flow.
The following are seven steps to creating continuous flow manufacturing cells:
- Decide which products or product families will go into your cells, and determine the type of cell
For product focused cells to work correctly, demand needs to be high enough for an individual product. For mixed model or group technology cells to work, changeover times must be kept short.
- Calculate Takt Time
Takt time, sometimes mistaken for cycle time, isn't dependent on your productivity- it is a measure of customer demand expressed in units of time.
- Determine the work elements and time required for making one piece
In much detail, document all of the actual work that goes into making one unit. Time each element separately several times and use the lowest repeatable time. Do not include wasteful elements such as walking and waiting time.
- Determine if your equipment can meet takt time
Using a spreadsheet, determine if each piece of equipment that will be required for the cell you are setting up is capable of meeting takt time.
- Create a lean layout
More than likely, you will have more than one person working in your cell (this depends on takt time); however, you should arrange the cell such that one person can do it thereby ensuring that the least possible space is consumed. Less space translates to less walking, movement of parts, and waste. U-shaped cells are generally best; however, if this is impossible due to factory floor limitations, other shapes will do.
- Balance the cell
This involves determining how many operators are needed to meet takt time.
- Determine how the work will be divided among the operators
There are several approaches. Some of these include splitting the work evenly between operators, having one operator perform all the elements to make a complete circuit of the cell in the direction of material flow, reversing the above or combinations of the previous approaches. After you’ve determined the above 7 elements, you will have gathered much of the necessary data required to begin drawing and laying out your continuous flow manufacturing cell.
About the Author
Adebayo is a thought leader in continuous process improvement and manufacturing excellence. He is a Certified Six Sigma Master Black Belt (CSSMBB), Digital Manufacturing Professional and ISO Management Systems Lead Auditor (ISO 9001, 45001 & ISO 22000) with strong experience leading various continuous improvement initiative in top manufacturing organizations.
You can reach him here.
