Q51338 What do you understand by Cellular or Group Layout?

Answer:

When TI Cycles reorganized its manufacturing plant, it used Group or Cellular Layout to improve the efficiency of production. Sundaram Fasteners boasts of a Cellular Layout with world-class control on manufacturing costs. What, then, is Cellular Layout? It is a layout based on group technology principles. It is a combination of both process and product layout and incorporates the strong points of both of these. Conventional layouts, product and process layouts, are two extremes of the spectrum. The specific approach used to reach a group layout may also result in one of the above two extremes, if the situation so demands.

This layout is suitable when a large variety of products are needed in small volumes (or batches). The group technology principle suggests that parts which are similar in design or manufacturing operations are grouped into one family, called a part-family. For each part-family, a dedicated cluster of machines (called ‘machine cells’) are identified. Generally, all the processing requirements of a particular part-family are completed in its corresponding machine cell, eliminating inter-cell transfers of the part.

Group technology and Cellular Layouts can be combined and used to produce families of parts more economically than can traditional process or product layouts. Data is gathered to identify parts with similar characteristics, which are also manufactured similarly. Groups of items can be formed either according to similarities in their design (external features such as size, shape, use, etc.) or according to similarities in their manufacturing process. This is a time-consuming and tedious task, which can be accomplished by the following methods:

1. Visual inspection method (for grouping items according to design similarities), which is very simple in application but not very accurate.
2. Examination of design and production data (for grouping items according to design similarities), which is more complex to implement than visual inspection but much more accurate.
3. Analysis of the production flow of items (for grouping items according to manufacturing process similarities).

This identification and coding is the chart of group technology. The equipment to make these is grouped together and designated for these parts. To some extent, a process layout, characteristic of job shops, is changed to a small well-defined product layout. This group of equipment is called a cell, and the arrangement of cells is called a Cellular Layout.

Figure 1 illustrates the difference between the two alternative layouts. Two parts require different tooling;

1. One part could be made in a job shop moving from machine A – C to D – E.
2. The second part can be made moving from machine A – C to D – B.

In the Process Layout, the machines are grouped together and the product moves to the machines. In the Cellular Layout, the machines are grouped in a line flow.

In order for a cell to be economical and practical in the long term, the machines must be closely grouped, and the cell must be flexible in its mix of capacity and must be big enough so any absent employee does not shut it down, yet is small enough for employees to identify with the cell and understand the products and equipment.

Cell manufacturing is also the building block of Flexible Manufacturing Systems (FMS). It is, in essence, FMS with some manual operations. The Cellular Layout principles are adopted in FMS because the concepts make it easier to process large volumes of information because of the decomposed manufacturing system; it is easier to manage the operational facilities compared to functional manufacturing due to limitation on cell size, and the technological compulsions often require grouping some operations like forging machines and heat treatment unit.

Although Cellular Layout is a catchy new term, the phenomenon itself is not new. For decades, large job shops have grouped equipment for high-volume parts or special customers. Similarly, assembly lines may group machines by type to make or modify a variety of parts that ‘feed into’ the main assembly line.

Example: Telco, Jamshedpur, has different machine shops and dye shops whose output is finally fed into the assembly line.

When considering a new technique such as Cellular Layout, managers need to thoroughly look at past practices as a guide to changing the manufacturing environment.

The U-shaped assembly line: At any airport, it is common to see baggage in the arrival area being distributed using U-shaped conveyor belts. There is a trend to move from traditional longitudinal assembly lines to U-shaped assembly lines, especially in Cellular Layouts. Not only is it useful particularly when there is a single worker in the line taking care of all the work- stations, but it also consumes less space. The U shape of the line cuts the walking distance of the worker by almost half.

Assembly line balances frequently result in unequal work-station times. Flexible line layouts, such as the U-shaped line with work sharing, could help resolve the imbalance and are a common way of dealing with this problem. The closeness of the work-stations, is used by the Japanese, to allow workers to help a fellow worker catch up, thus increasing teamwork among workers. U- shaped assembly lines are being successfully used by Matsushita Electric Co. of Japan by using a single worker in the line. In addition, the U-shaped line reduces material handling as the entry and exit points of the material on the line are nearby. A trolley which brings the raw material for the line may take back the finished goods in a single round.

Advantages and Disadvantages

Some of the advantages of Cellular Layouts are that overall performance often increases by lowering costs and improving on-time delivery. Quality should increase as well, though that might take other interventions beyond the layout change. Other advantages are given below:

1. Lower work-in-process inventories,
2. A reduction in materials handling costs,
3. Shorter flow times in production,
4. Simplified scheduling of materials and labour,
5. Quicker set-ups and fewer tooling changes, and
6. Improved functional and visual control.

Disadvantages include the following:

1. Reduced manufacturing flexibility.
2. Unless the forecasting system in place is extremely accurate, it also has the potential to increase machine downtime (since machines are dedicated to cells and may not be used all the time).
3. There is also the risk that the Cells that may become out-of-date as products and processes change, and the disruption and cost of changing to cells can be significant.
4. There is increased operator responsibility, and therefore behavioral aspects of management become crucial.