MPCT
Recent Trends in Information Technology (RTIT)-2010
AN IMPLEMENTATION OF GROUP TECHNOLOGY USING ‘C’ ON A PROBLEM OF MACHINE SEQUENCING Amit Aherwar Department of Mechanical Engineering, Madhav Institute of Technology & Science, Gwalior Phone: 09826317058, Email:
[email protected]
ABSTRACT All the manufacturing companies are striving hard to achieve their aims, objectives and their capabilities by proper planning and application of automation and innovative concepts, example Group Technology (GT), Cellular Manufacturing (CM), just-in-time (JIT) and Total Quality Management (TQM). Among these innovative concepts, GT is recognized by the manufacturing companies as a major driver to achieve world-class capabilities. Many large and medium-size manufacturing companies have adopted GT concepts, and experienced reduction in manufacturing lead time and material handling cost, and improvement in quality among other benefits. The application of group technology is not just limited to existing trend in shop layout, process planning, design, fixture, but it is used in scheduling. This problem is very challenging and complex, as so many important as well as strategic factors need to given due to consideration. In this paper, a program is made that is based on Hollier’s 2nd method to arrange machines of a Group technology cell. The basic two obstacles that come in the ways to switch over to Group Technology technique from conventional layout are: (1) grouping of parts and machines and (2) arrangement of machines in a cell. A program to group the parts and machines has already been made, so I have tried to solve the second problem by preparing such type of program with the help of ‘C’ language.
The objective of cell formation decision is to create mutually separable machine cells. Cells are designed so that they can operate independently with minimum intercellular moves between cells and the result of these separable cells formation is the simplified material flows that allow much easier control than job shop.
INTRODUCTION
In the early 1960s, Opitz carried out an investigation into work piece statistics, which showed that although firms manufacture a variety of products, the spectrum of them all was remarkably similar. Based on the findings of this investigation, he established a Classification system, which enabled components to be codified by means of their geometrical similarity.
Group Technology (GT) is a manufacturing philosophy or concept that identifies and exploits the similarities of product design and manufacturing processes. One application of GT is cellular manufacturing (CM). The first and most important step in CM is the cell formation, which groups parts with similar design features or processing requirements into families so as to take advantage of their similarities and forms machine cells by assigning machines dedicated to process only the parts belonging to each family.
DEVELOPMENT TECHNOLOGY
OF
GROUP
The basic thinking behind Group Technology can be attributed to the Russians, who carried out initial investigations during the 1920s. Grayson has traced the progress of GT since then and its gradual adoption in other countries. The early work stressed the importance of industrial classification and initial applications were limited to the medium and large batch productions. The work was extended during the war years by Mitrofanov to include work pieces produced in small batches. His major publication on Group Technology first appeared in 1959 and was translated into English in 1966. Mitrofanov proposed that it was possible to produce a theoretical composite component which incorporated all the major features of components belonging to a family, and that a machine could be tooled up to produce the composite component, thus providing the setups required for each component in the family.
A number of methods for classification and coding were being investigated at approximately the same time. A significant growth in the interest and application of Group Technology in the U.K. followed the publication of Opitz's work. The most notable
22
MPCT
Recent Trends in Information Technology (RTIT)-2010
were the works conducted by PERA and by MTIRA. A government-sponsored centre was set up in Blacknest for the dissemination of information about Group Technology, and a specialist division was set up by the Institution of Production Engineers which ran seminars and published papers on the subject. The advances in GT have been greatly influenced by the existence of a classification system devised by Brisch and Partners. The Brisch system was originally designed to facilitate variety reduction, component standardization and product rationalization. It was later developed to suit GT requirements. There have been many applications of GT using the Brisch system and the most successful example was probably that of Serck Audco Valves. During the late 1960s, several well-known organizations implemented Group Technology. A notable example of one such companies was Ferodo where reductions in W.I.P. of about 8 to 1 were achieved. Other well-known firms such as Ferranti, Rolls Royce and Baker Perkins introduced GT at roughly the same time, and these applications provided benefits in many areas. Since then there have been more applications of GT in the U.K. – Herbert Machine Tools, Rank Xerox, Wildt Mellor Bromley and Simon Container Machinery. Other methods were later developed as alternatives to the classification and coding approach. These were methods based on the analysis of production information. The most representative work was the Production Flow Analysis method proposed by Burbidge. Other similar methods were due to ELEssawy, Purcheck and Nagarkar. These methods are different with respect to the underlying assumptions and the technique of analysis, but the general approach is to study a company’s total system and to determine those families of components which are related by similarities in the production facilities required for their manufacture. After some initial experience with Group Technology in organizations, it became evident that a change in the workshop was not sufficient on its own. To obtain the full benefits, it was necessary to change other parts of the system, including, for example, production control, planning, payment systems and accounting methods. For this reason, Group Technology was changed from being a technique in itself to being part of a new philosophy of production organization. Most research efforts of recent years have been directed towards other areas of organization affected by the introduction of GT. This trend was initially reflected at the ‘Conference on Production Improvement through Group and Cell Formation’, held at
the University of Aston in Birmingham in February 1973. Most speakers agreed that Group Technology had to be looked at not only as a machining system but as a complete manufacturing philosophy embracing all functions. In the late 1970s, Group Technology began to lose favour among British manufacturers. This was partly due to the fact that some companies who had previously introduced GT were discovering not only the advantages but also the problems, which sometimes result. This was not altogether unexpected and indeed Leonard and Rathmil that Group Technology is not a universal panacea for manufacturing industry demonstrated it. A publication by the EDCME suggested some reasons for the slow rate of adopting GT by the British firms; traditional attitudes and practice, fear of changes and suspicion of extravagant claims for GT were the main factors. Burbidge held a different viewpoint and proposed some other reasons why GT has failed to retain acceptance by the British industry. Although Group Technology is out of favour in the U.K., it has flourished in other industrial nations. Since the 1960s, work has been done, though on smaller scales, in the Netherlands, Switzerland, Belgium, Sweden, U.S.A., Japan and West Germany. Today, many of these countries have more application of GT than in the U.K. and they are continuing to press ahead with its development. In the United States, Group Technology has been accepted as a technique of raising manufacturing performance, and the merits of integrating it with the very popular production control technique of Material Requirements Planning are well publicized. The British industry appears to have given up GT just when the other industrial nations have become convinced of its value and are taking it up. This suggests that there is still a need for research directed to testing the basic hypotheses and premises of GT. New stimulation is required if Group Technology in Britain is to be revitalized and some benefits gained. HOLLIER METHOD 1 The first method uses the sums of flow “From” and “To” each machine in the cell. The method can be outlined as follows: (a) Develop the From-To chart from part routing data. The data contained in the chart indicates numbers of part moves between the machines (or workstations)
23
MPCT
Recent Trends in Information Technology (RTIT)-2010
in the cell. Moves into and out of the cell are not included in the chart. (b) Determine the “From” and “To” sums for each machine. This is accomplished by summing all of the “From” trips and “To” trips for each machine (or operation). The “From” sum for a machine is determined by adding the entries in the corresponding row, and the “To” sum is found by adding the entries in the corresponding column. (c) Assign machines to the cell based on minimum “From” or “To” sums. The machine having the smallest sum is selected. If the minimum value is a “To” sum, then the machine is placed at the beginning of the sequence. If the minimum value is a “From” sum, then the machine is placed at the end of the sequence. Tie breaker rules: (i) If a tie occurs between minimum “To” sums or minimum “From” sums, then the machine with the minimum “From/To” ratio is selected. (ii) If both “To” and “From” sums are equal for a selected machine, it is passed over and the machine with the next lowest sum is selected. (iii) If a minimum “To” sum is equal to a minimum “From” sum, then both machines are selected and placed at the beginning and end of the sequence, respectively. (d) Reformat the From-To chart. After each machine has been selected, restructured the from-To chart by eliminating the row and column corresponding to the selected machine and recalculate the “from” and “To” sums. Repeat steps 3 and 4 until all machines have been assigned HOLLIER METHOD 2 This approach is based on the use of form/To ratios formed by summing the total flow from and to each machine in the cell. The method can be reduced to 3 steps: (a) Develop the Form-To chart. This is the same step as in Hollier Method 1. (b) Determine the Form/To ratio for each machine. This is accomplished by summing up all of the “Form” trips and “To” trips for each machine (or operation). The “Form” sum for a machine is determined by adding the entries in the corresponding row, and the “TO” sum is determined by adding the entries in the corresponding column. For
each machine, the Form/To ratio is calculated by taking the “Form” sum for each machine and dividing by respective “TO” sum. (c) Arrange machines in order of decreasing Form/To ratio. Machines with a high Form/To ratio distribute work to many machines in the cell but receive work from few machines. Conversely, machines with a low From/To ratio receive more work than they distribute. Therefore, machines are arranged in order to descending From/To ratio. That is, machines with high ratios are placed at the beginning of the workflow, and machines with low ratios are placed at the end of the work flow. In case of a tie, the machine with the higher “From” value is placed ahead of the machine with a lower value.
FLOW DIAGRAM Start
Ask for the value of: No. of rows No. of columns Elements of matrix
Initialize 1st row and column (Using for loop)
Initialize diagonal value=0
Enter the elements of matrix (Using for loop)
Calculate Sum of rows (Using for loop)
Calculate Sum of col. (Using for loop)
Calculate ratio (row sum/col. sum) (Using for loop)
Contd...
24
MPCT
Recent Trends in Information Technology (RTIT)-2010 RESULT Ratio[1] = 0.6667 Ratio[2] = 1.1000 Ratio[3] = 1.6666 Ratio[4] = 0.8181
Store ratio array (using for loop)
Check whether the element is larger to its next
Matrix after sorting according the ratio
If the element is larger
Check further with 2
nd
1
2
3
4
3
10
50
0
0
2
20
0
21
25
4
30
0
15
0
1
0
10
0
30
no. Store this value
Print this sorted array
Calculate % of in-sequence moves = no. of in sequence moves/ no. of total moves
Calculate % of backtracking moves = no. of backtracking moves/ no. of total moves
Percentage of in-sequence moves = 49.76% Percentage of backtracking moves = 36.01% So machine sequence is: 3-2-4-1
CONCLUSION Print the % of in-sequence moves, backtracking moves
End
AN ILLUSTRATIVE EXAMPLE: Suppose that four machines, 1, 2, 3, and 4 have been identified as belonging in a GT machine cell. An analysis of 50 parts processed on these machines has been summarized in the From-To chart of Table 1.1. Additional information is that 50 parts enter the machine grouping at machine 3, 20 parts leave after processing at machine1, and 30 parts leave after machine 4.
In this paper, an attempt has been made, to arrange the machines of a GT cell through computer program, which is made in ‘C’ Language. This program arranges the machines automatically, by feeding the number of parts and machine of a GT cell. This program is also calculating the Percentage of in-sequence moves & backtracking moves.
REFERENCES
1
2
3
4
1
0
10
0
30
2
20
0
21
25
3
10
50
0
0
Nallen C Suresh, John M Kay, “Group Technology and Cellular Manufacturing. 2. Mikell P. Groover, “Automation, Production Systems and Computer integrated Manufacturing”, PHI Publication. 3. Hollier, R. H., “The Layout of Multiproduct lines”, International Journal of Production Research. 4. KURIC, I.: Theory of Group Technology. In: Proceedings of the Conference “Systemy oprzyrzadowania w budowe maszyn i projektowanie procesów technologicznych” Krakov, 2000, pp. 75-82,
0
ISBN 3-901509-16-X. 5. E. Balaguruswami, “ANSI C”, TMH
4
30
0
15
1.
Publication.
25
