Organizing Machines Into Cells

Many companies have realized significant benefits from implementing manufacturing cells in their plants. They include:

• supporting manufacture of small, or as needed, quantities allowing operators to perform multiple processes on a part in
• a localized area
• reducing part throughput time
• minimizing part handling and travel from the start of the process to the end
• faster discovery of quality problems.

If a company decides to lay out machines in a cellular arrangement, it must first determine which parts will be produced in the cell so it can be configured appropriately. To do this, we need to think of parts in terms of “families” that undergo the same manufacturing operations. A simple, yet effective way to identify product families is a product/process chart. The following example shows parts and processes included in such a chart.

The parts shown on the chart undergo various manufacturing processes, as indicated by an “X”. The stem and body could be considered a family, and hence are candidates for a manufacturing cell, because they undergo identical manufacturing processes. A cell consisting of turning, milling, drilling and assembling could be configured to produce these parts. Each of the other parts could be processed in this cell, but before making decisions for these parts, consider:

• How much of the cell’s capabilities will the part employ? In the case of the cap, three of the four processes planned for the cell are used to finish the part. With the insert, only two of processes are needed. Therefore, the cap would be a better candidate to assign to the manufacturing cell. It is not necessary for all parts produced in the cell to require exactly the same manufacturing processes, but they should require very similar processes.
• What are the volumes of the parts being considered? When determining which parts and processes to include in the manufacturing cell, part volumes must be considered. For example, if the housing is a low volume part and requires a tumbling operation to be completed prior to assembly, it may not be worth assigning this part to the cell. The fact that the stem and body do not require tumbling would mean that either the part would have to go to another area to be processed before returning to the cell, or an underused tumbling machine would be added to the cell. On the other hand, if the housing is a high volume part (in relation to the stem and body), it might be worth including the tumbling machine in the cell and producing this part complete. In the case of the insert, the situation is reversed. A low volume might warrant putting the insert into the cell, despite not fully using the cell’s equipment, because it will have a minimal impact on capacity. But if the insert has a high volume, then it may overtax portions of the cell, hindering the production of better-suited parts.
• How difficult would it be to partially complete the part in the cell and complete it outside the cell? This question may apply to the bonnet. If the turning, milling and drilling can be completed in the cell using a substantial part of the cell’s capability, then the bonnet could move to another area for the tumbling process. Again, the question of volume needs to be considered.
• What is the future of the part? If the part is growing in volume, this may affect the decision. Back to our discussion of the housing—if the volume is high, which might justify putting the tumbling machine in the cell, but volume is expected to decline in the near future, it may not be worth putting the tumbling machine in the cell after all. With the insert, an expected growth in volume might prohibit its inclusion in the cell.

One possiblity as to what to include in the cell is shown below. The shaded parts could be produced in the cell, while those that are not shaded would not. It would also be possibile to establish two cells, with the second producing the housing and the bonnet.

Following the above approach to identifying cellular manufacturing candidates will allow you to start realizing the benefits of manufacturing cells sooner.