Cellular Manufacturing

Cellular Manufacturing An efficient way to organize your small-quantity-multiple-product manufacturing Cellular Manufacturing

Group Technology (GT) Group technology (GT) is a concept that seeks to take advantage of the design and processing similarities among the parts to be produced. The term “group technology” first was used in 1959, but not until the use of interactive computers became widespread in the 1970s did this technology develop significantly. Group technology becomes especially attractive because of the ever-greater variety of products available to consumers, which are often produced in batches. Since nearly 75% of manufacturing today is batch production, improving the efficiency of batch production becomes important. The traditional product flow in batch manufacturing, the process-oriented layout, creates large amount of transportation and WIP. For the small-quantity-multiple-product manufacturing, the things will get worse. Such an arrangement is not efficient, because it wastes time and effort. A more efficient product flow line to take advantage of group technology is the product-oriented layout or to form a manufacturing cell. Cellular Manufacturing

Work cell layout 1. Process-oriented layouts: You collect all like machines together and bring all parts to them. 2. Product-oriented layouts: You place machines where they are needed to eliminate excessive moving. Skipping over machines and backtracking will result from process layouts and must be discouraged because it adds costs without adding to the value (muda). When many parts are fabricated in one group of machines (called a process layout), jumping around may be necessary, but we want to minimize this jumping, skipping, and backtracking. Cellular Manufacturing

Group technology Part similarity Cellular Manufacturing

Group Technology Group technology takes advantage of similarity in parts or features in a group or family of parts so that these parts can be processed as a group. Part family Machine group Cellular Manufacturing

Advantages of GT • It makes possible the standardization of part design and the minimization of design duplication. New part designs can be developed using previously used designs. • Data that reflect the experience of the designer and the manufacturing process planner are stored in the database. Thus, a new and less experienced engineer quickly can benefit from that experience by retrieving any of the previous designs and process plans. • Manufacturing costs can be estimated more easily, and the relevant statistics on materials, processes, number of parts produced, and other factors can be obtained more easily. Cellular Manufacturing

Advantages of GT • Process plans are standardized and scheduled more efficiently, orders are grouped for more efficient production, and machine utilization is improved. Setup times are reduced, and parts are produced more efficiently and with better and more consistent product quality. Similar tools, fixtures, and machinery are shared in the production of a family of parts. Programming for NC is automated more fully. • • With the implementation of CAD/CAM, cellular manufacturing, and CIM (computer integrated manufacturing), group technology is capable of greatly improving the productivity and reducing the costs in batch production—approaching the benefits of product-oriented layout. Cellular Manufacturing

Classification and Coding of Parts In group technology, parts are identified and grouped into families by classification and coding (C/C) systems. This process is a critical and complex first step and is done according to the part’s design attributes and manufacturing attributes. Cellular Manufacturing

Classification and Coding of Parts Design attributes: • External and internal shapes and dimensions • Aspect ratios (such as length-to-width or length-to-diameter) • Dimensional tolerances • Surface finish • Part functions Cellular Manufacturing

Classification and Coding of Parts Manufacturing attributes: •Primary processes used • Secondary and finishing processes used • Dimensional tolerances and surface finish • Sequence of operations performed • Tools, dies, fixtures, and machinery used • Production quantity and production rate Cellular Manufacturing

Classification and Coding of Parts Coding can be time consuming, and considerable experience is required. The coding can be done simply by viewing the shapes of the parts in a generic way and then classifying the parts accordingly (such as parts having rotational symmetry, parts having rectilinear shape, and parts having large surface-to-thickness ratios). The code for parts can be based on a company’s own system of coding. The three basic types of coding systems are: The Opitz System The MultiClass System The KK-3 System Cellular Manufacturing

Classification and Coding of Parts The Opitz System The Opitz system was developed in the 1960s in Germany by H. Opitz (1905-1977), and was the first comprehensive coding system presented. The basic code consists of nine digits (12345 6789) representing design and manufacturing data. Four additional codes (ABCD) may be used to identify the type and sequence of production operations. This system has two drawbacks: (a) it is possible to have different codes for parts that have similar manufacturing attributes, and (b) a number of parts with different shapes can have the same code. Cellular Manufacturing

Classification and Coding of Parts The multiClass system It was developed to help automate and standardize several design, production, and management functions and involves up to 30 digits. The KK-3 system It is a general-purpose system for parts that are to be machined or ground. It uses a 21-digit decimal system. This code is much greater in length than the two previous systems described, but it classifies dimensions and dimensional ratios, such as the length-to-diameter of the part. The structure of a KK-3 system for rotational components is shown in Fig. 38.17. Cellular Manufacturing

The structure of a KK-3 system for rotational components Cellular Manufacturing

Cell Formation Approaches Efficient work flow can result from grouping machines logically so that material handling and setup can be minimized. Parts can be grouped so that the same tooling and fixtures can be used. When this occurs, a major reduction in setup results. Machines can also be grouped so that the amount of handling between machining operations also can be minimized. Part family Machine group Cellular Manufacturing

Cell Formation Approaches Rank-Order Cluster Algorithm There are several cell formation approaches available. Here, we focus on one of them, the Rank-Order Cluster Algorithm The left diagonal block shows that two cells are finally formed: C1: Machines: M1 and M2 Parts: 2, 4, and 6 C2: Machines: M3 and M4 Parts: 1, 3, and 5 Cellular Manufacturing

Cell Formation Approaches Rank-Order Cluster Algorithm Cellular Manufacturing

Cell Formation Approaches Rank-Order Cluster Algorithm Example: Consider a 8-part-and-6-machine problem shown in the following table, form the part family and machine group. Cellular Manufacturing

Cell Formation Approaches Rank-Order Cluster Algorithm Step 1:We assign column 8 place value 1, column 7 place value 2, column 6 place value 4, and so on. Row A receives a value of 128 + 64 + 8 = 200 for its 1’s in the first,second, and fifth columns. Evaluating all rows produces the values shown. Cellular Manufacturing

Cell Formation Approaches Rank-Order Cluster Algorithm Step 2: Rank the row in order of decreasing decimal weight values. The rows are reordered to A, B. C, D, E. F. Cellular Manufacturing

Cell Formation Approaches Rank-Order Cluster Algorithm Step 3:Repeat steps 1 for each column by assign the value to each row with bottom row’s value 1, 2nd bottom row 2, and so on so for. This produces the following result: And reorder the column in decreasing values from left to right, the new ordering is 3,1,2,4,5,6,7,8 (the table is shown in next slide). Cellular Manufacturing

Cell Formation Approaches Rank-Order Cluster Algorithm Step 4:Repeat steps 1, 2, and 3, finally, the result is given by: 4 4 Next, repeat step 1 for further ordering. However, the row ordering for the repeat step is unchanged and we stop. Cellular Manufacturing

Cell Formation Approaches Rank-Order Cluster Algorithm Homework (lab) Problem: Consider a 6-part-and-9-machine problem shown in the following table, form the part family and machine group. Cellular Manufacturing

Work cell Layout Cellular Manufacturing

Work cell Layout The lean production, linked-cell system is the newest manufacturing design. Cellular Manufacturing

Work cell Layout Manufacturing cells produce parts one at a time using standing and walking workers Cellular Manufacturing

Interim-cell design example A manufacturing cell produces a family of 4 parts, in this case, 4 pinions. Cellular Manufacturing

Interim-cell design example Cellular Manufacturing

Interim-cell design example The part family can be manufactured in the lean-production cells shown in following figures operated by one to three workers. The interim-cell: the cell can be operated by one, or multiple workers. Left figure shows a one-man operated cell. Cellular Manufacturing

Interim-cell design example This cell is a less-than-full-capacity design that can be quickly modified for different parts in the product family, and to increase output by adding workers. Left figure shows a two-man operated cell. Cellular Manufacturing

Interim-cell design example These workers are multifunctional and multiprocessers. Left figure shows a three-man operated cell. Cellular Manufacturing

Interim-cell design example Cycle time is calculated as below CT = (MT×O) + (WT×WC) where CT = cycle time, minutes MT= worker-manual time, minutes O = number of operations WC= number of walk cycles, or Cellular Manufacturing

Interim-cell design example CT = 1/PR where PR = production rate, parts/hour. Throughput time can be calculated as: TT= CT × C where TT = throughput time, minutes C= number of cycles that the part was in the cell Cellular Manufacturing

Interim-cell design example Cycle time in this example: CT = (MT×O) + (WT×WC) = 0.25 minutes × 8 +3 sec. × 8 = 144 sec./part = 2.4 min./part Number of parts produced = (3,600sec./hour) / (72 sec./part) = 25 parts/hour Throughput time = (144sec./part) × (8 transfers) = 1152 sec./part or 19.2 min./part Cellular Manufacturing

Interim-cell design example Cellular Manufacturing

U-Shape Example Cellular Manufacturing

Work cell Layout • Lean manufacturing and cell design, By Black, J. Temple. Dearborn, Mich. : Society of Manufacturing Engineers, c2003. Cellular Manufacturing

Cellular Manufacturing