cellular manufacturing

1. UNIVERSITY OF BOTSWANA
DEPARTMENT OF MECHANICAL ENGINEERING
MANUFACTURING SYSTEMS
MMB 513
MINI PROJECT
TITLE; CELLULAR MANUFACTURING
BY;
KEALEBOGA MOGAPI
201001654

2. CELLULAR MANUFACTURING
Introduction
In today’s business world, competitiveness defines an industry leader. The drive toward maximum efficiency is constantly at the forefront of such companies’ objectives. Managers across the country are striving to adopt lean manufacturing practices to help address worries about their bottom line. Cellular Manufacturing is one staple of lean manufacturing.
Cellular manufacturing system layout is based on recognizing similarities in products, similarities in geometry, size, materials and processing requirements. This similar products are collected “Grouped” instead of being treated as individuals. Manufacturing cells which are a group of equipment (resources) are formed. These cells are dedicated to produce similar products or a family of parts. A Manufacture Cell produces parts, one at a time, following the sequence of the machines and operations in a lean flow.
The objective of cellular manufacturing is to design cells in such a way that some measure of performance is optimized. This measure of performance could be productivity, cycle time, or some other logistics measure. Measures seen in practice include pieces per man hour, unit cost, on-time delivery, lead time, defect rates, and percentage of parts made cell-complete.

3. LAYOUTS BY TASKSVS MANUFACTURING CELLS
Old “Layouts by Tasks” are inconvenient because
• Defects in products are not detected until the part has a quality inspection.
• Some of the defects are not generated in the manufacture process but appear due to material handling problems (dirt, spots, damage).
• Parts spend too much time going to all the process. (Sometimes days or weeks – funnel sample).
• Inventory (RM, WIP, and FG), can require up to 25% of the total area of the plant.
Fig 2; Process flow before the group technology
Fig 3; Process flow after the group technology
CELLULAR LAYOUT ADVANTAGES
• Reduced material handling and transit time
• Reduced setup time
• Reduced work-in-process inventory

4. • Better use of human resources
• Better scheduling, easier to control and automate
• Less floor space required
• Reduced direct labor
• Heightened sense of employee participation
• Increased use of equipment & machinery
• Reduced investment on machinery & equipment
CELLULAR LAYOUT DISADVANTAGES
• Sometimes cells may not be formed because of inadequate part families.
• Some cells may have a high volume of production and others very low. This results in poorly balanced cells.
• When volume of production changes, number of workers is adjusted and workers are reassigned to various cells. To cope with this type of reassignments, workers must be multi-skilled and cross-trained.
• Sometimes, machines are duplicated in different cells, this increases capital investment.
 Issues like placement of bottleneck machines are needed to be addressed during cell formation.
 Machines may require their own individual stocks of materials.
 Inadequacies in employee education, training & involvement could come in the way of proper implementation.
RULES FOR MANUFACTURING CELLS
 When installing a Manufacturing Cell, the productivity will increase, so prepare a plan and explain to the personnel that some of them will have to be “Re-located”
 Design a complete Inspection System for each Manufacturing Cell.
 Each aspect affected by the Manufacturing Cell should be discussed and communicated to all the workers and the Labor Union through the Manager.

5.  The design for the Cell should consider:
 Work Flow
 Parts and Material Flow
 The 5S pillars, Sort (Seiri), Set in Order (Seiton), Shine (Seiso), Standardize (Seiketsu), and Sustain (Shitsuke), which provide a methodology for organizing, cleaning, developing, and sustaining a productive work environment.
MANUFACTURING CELL IMPLEMENTATION
A wide variety of methods for the implementation of cellular manufacturing have been proposed. These range from complex computer and mathematical models to straightforward applications, such as production flow analysis. A pattern for implementation is now presented.
The first step in implementing cellular manufacturing is to break down the various items produced by the company into a number of part sets or families. The grouping process (group technology) involves identifying items with similarities in design characteristics or manufacturing characteristics, and grouping them into part families. Design characteristics include size, shape, and function; manufacturing characteristics or process characteristics are based on the type and sequence of operations required. In many cases, though not always, the two kinds of characteristics are correlated. Therefore design families may be distinctly different from processing families.
Fig 4; part family
Once identified, similar items can be classified into families. Then a system is developed that facilitates retrieval from a design and manufacturing database. For example, the system can be used to determine if an identical or similar part exists before a completely new part is designed.

6. If a similar part is found, it may be that a simple modification would produce satisfactory results without the expense of new part design. Similarly, planning the manufacturing of a new part after matching it with an existing part family can eliminate new and costly processing requirements.
Parts Classification and Coding
Identification of similarities among parts and relating the similarities by means of a numerical coding system;
 Most time consuming of the three methods
 Must be customized for a given company or industry
Reasons for using a coding scheme:
 Design retrieval
 Automated process planning
 Machine cell design
Most classification and coding systems are based on one of the following:
 Part design attributes
 Part manufacturing attributes
 Both design and manufacturing attributes
Part design attributes includes major dimensions, basic external shape, basic internal shape, length/diameter ratio, material type, part function, tolerances and surface finish.
Part manufacturing attributes includes major process operation sequence, batch size, annual production, machine tools cutting tools and material type.
Coding refers to the process of assigning symbols to the parts. The symbols represent design attributes of parts or manufacturing features of part families. The variations in codes resulting from the way the symbols are assigned can be grouped into three distinct types of codes:
 Monocode or hierarchical code- Interpretation of each successive digit depends on the value of the preceding digit.
 Polycode or attribute- Interpretation of each symbol is always the same and there is no dependence on previous digits.
 Hybrid or mixed code- Combination of hierarchical and chain-type structures.

7. Some of the important systems of coding
 Opitz classification system –the University of Aachen in Germany, nonproprietary, Chain type.
 Brisch System –(Brisch-Birn Inc.)
 CODE (Manufacturing Data System, Inc.)
 CUTPLAN (Metcut Associates)
 DCLASS (Brigham Young University)
 Multi Class (OIR: Organization for Industrial Research), hierarchical or decision-tree coding structure
 Part Analog System (Lovelace, Lawrence & Co., Inc.)
Grouping of part or product families requires a systematic analysis that often proves to be a major undertaking. Usually, there is a considerable amount of data to analyze, and this in turn can be quite time-consuming and costly. Three primary methods exist for accomplishing the grouping process: visual inspection, examination of design and production data, and production flow analysis. Visual inspection is the least accurate of the three but nonetheless the simplest and the least costly. The most commonly used method of analysis is the examination of design and production data. This method is more accurate but is also more time-consuming. Production flow analysis examines operation sequences and machine routing to uncover similarities (therefore, it has a manufacturing perspective rather than a design perspective). However, unless the operation sequencing and routings are verified, this method could be far from optimal.
The resulting number of families determines the number of cells required, as well as what machines are required within each cell. The cell usually includes all the processing operations needed to complete a part or subassembly. However, it is possible for a product to go from raw materials to packaging and be ready for shipment by the time it reaches the end of the cell.
The families will also help determine where within the cell each machine will be located for the most efficient flow, and how many employees are needed within each cell. After the product families are determined, the machines needed for the production process of a specific family are organized into cells according to processing requirements (e.g., the order of processing). Frequently, machines are grouped in an efficient U-shaped configuration. Since each machine operates on its own for much of the cycle, few workers may be needed, and even then only for a limited number of steps.
The optimal layout is one that minimizes the distance between cells, or the distance to the next production point. The resulting reduction in time and handling ultimately provides a reduction in processing costs. Some firms utilize "linked-cell manufacturing," which is the concept of

8. arranging the manufacturing cells near the assembly cells. Again, this decreases travel distances while reducing materials handling. Hopefully, the floor layout will also provide for the easy flow of a product to shipping, if shipping is located close to the cells in a streamlined flow.
Some plants in advanced stages of cellular manufacturing utilize what is known as a "mini- plant." The cell not only does the manufacturing, but also has its own support services, including its own industrial engineer, quality manager, accountant, and marketing representative and/or salesperson. Only research and development and human resource management are not dedicated to the mini-plant.
An entire facility can be broken down into a number of mini-plants, each of which operates as an independent profit center.

9. REFERENCES
Hyer, Nancy and Urban Wemmerlov. "Cell Manufacturing: The Hard Part Is to Get People in Step with the Program." Mechanical Engineering 126, 2004.
Meredith, Jack R., and Scott M. Shafer. Operations Management for MBAs. Hoboken, NJ: John Wiley & Sons, Inc., 2004.
Mr kommula Lecture notes. Manufacturing Systems. University of Botswana.