1. MACHINE GROUPING IN CELLULAR MANUFACTURING With Reduction Of Material Handling As the Objective
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2. MACHINE GROUPING IN CM With Reduction of MH As The Objective
Here we will investigate how to reduce MH in a cellular manufacturing layout
As in ordinary Group formation as discussed in lecture# 17 & 18 (cell formation in GT), The machine-grouping analysis does not consider either the production or the associated material handling difficulties in machine grouping. These can be important factors
The main emphasis of that algorithm was on grouping machines so that a cell can process a part completely
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3. MACHINE GROUPING IN CM With Reduction of MH As The Objective
4. The incidence matrix on which the method is based depends on the use or nonuse of a machine for a part, & each part is given the same importance in cell formation
5. If the parts vary in their production volume, identical weighting does not seem logical
6. It seems obvious that the machines used in producing a large-volume part should be physically closer together than the machines associated with a part that has a very small demand
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4. MACHINE GROUPING IN CM With Reduction of MH As The Objective
Along with volume of flow b/w machines that defines material handling, there may also be some difficulties due to varying weights & volumes of the parts, & special care that may be needed in transportation (eg. Glass, explosives)
More unitization of part in handling may produce different proportion of pallet loads than the relative proportions associated with the part demands
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5. MACHINE GROUPING IN CM With Reduction of MH As The Objective
The new solution procedure that incorporates material handling is a slight modification of tabular method discussed in Cell Formation in Group Technology
The modification involves the addition of steps 0a & 0b before step1 & changing step1
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6. MACHINE GROUPING IN CM With Reduction of MH As The Objective
The new procedure is as follows:
Step 0a: Determine material handling (MH) for each type of part:
For each part type i, based on the volume of production, determine the unit loads of material handling necessary per unit time (ui). Also note the degree of difficulty in transportation associated with part i.
The degree of difficulty is a relative measure of difficulty in material handling b/w two part types
The unit load of a part that is easiest to handle is given a degree of difficulty 1. All other parts are compared with this part to determine (subjectively) their relative degree of difficulty in handling, di
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7. MACHINE GROUPING IN CM With Reduction of MH As The Objective
The new procedure is as follows:
Step 0b: Construct a MH Table.
To develop the MH Table, start with a machine component matrix in which 1 indicates the use of machine & blank or zero indicate nonuse of the machine in processing a specific part type
Multiply each element 1 for part i by its ui & di values
This give the MH Table. The element in the MH table indicates the weighted MH trips b/w two machines to produce a specific part
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8. MACHINE GROUPING IN CM With Reduction of MH As The Objective
Step 1: Develop the Machine to Machine Material Handling Table (MM):
Table indicates the total of all modified MH trips that would occur b/w two machines.
Each element in the table is obtained by adding from the MH table, all the MH trips that occur b/w the associated two machines. Note that MM table is symmetrical about the diagonal; therefore only elements above or below the diagonal are needed
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9. MACHINE GROUPING IN CM With Reduction of MH As The Objective
Procedure can be best understood by the Data illustration on EXCEL Sheets
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10. MATERIAL HANDLING: Flow Lines
Flow Pattern in Assembly Lines eg: a. serial & modular conveyor systems
b. Banking
c. closed loop conveyor systems
d. Automated Control Transfers
e. Horizental & Vertical Flow
Note: all from a – e : DO YOURSELF
Guidelines: Book name="Manufacturing Facilities : Location, Planning, & Design“ 2nd Edition
chapter # 10, pages:
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11. 19/04/2013
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12. Lecture # 17 & 18 Date: Main Topic: Cell Formation in Group Technology Sub topic: 1-9 Steps for Tabular method of GT Cell Formation
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13. CELL FORMATION IN GROUP TECHNOLOGY
There are numerous methods available for machine grouping in Group Technology (GT)
Here we will discuss the simple method called as Tabular Method.
The method start with 0-1 table called the machine component matrix or incident matrix
This table show the machine that each component (e.g., part or job) needs in production; 1 indicating the use of machine & 0 (or a blank) indicating the nonuse of the machine
The objective is to develop m/c cells that each component can (as for as possible) be fully processed in a single cell
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14. CELL FORMATION IN GROUP TECHNOLOGY
TABULAR METHOD SOLUTION PROCEDURE: Procedure falls in two phases: In 1st Phase: the machine is assigned to a group based on its affinity to all the machines that are presently in the group In 2nd Phase: this phase distributes the jobs in the cells generated in the first phase
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15. TABULAR METHOD OF CELL FORMATION
PHASE 1: This phase of tabular method follows the steps given here Step 1. Develop a machine-to-machine relationship table. A machine-to-machine relationship table 5.2 indicates the number of jobs that are processed on both machines Step 2. Select the initial value of Relationship Counter (RC) , RC defines the value of relationship being used in the present calculation these values are taken from table 5.2. Pick the largest element in table 5.2 & designate it as the present value of RC. The RC will change as we go through the iterative process
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16. TABULAR METHOD OF CELL FORMATION (Cont..)
Step 3. Define a value of minimum %age . A measure of effectiveness of joining a machine to a group, such as 50% (P=0.5), is defined by analyzer at the beginning of the problem. It states the closeness an entering machine must have with all the existing machines within a group in order for entering machine to join that group.
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17. TABULAR METHOD OF CELL FORMATION (Cont..)
Step 4. Starting with the first row in table 5.2, examine each row for an elemental value that equals RC. Note the machines in corresponding row and column Step 5. If the associated machines in the row & column are not already in a group, then form a group consisting of these two machines & go to step 7. If both m/cs are already assigned to same group ignore the observation & go to step 7. If one of the machines in the pair is in a group & the other one has not been assigned yet (this machine is called the Entering Machine), go to step 6a. If both machines are assigned, but to different groups, go to step 6b
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18. TABULAR METHOD OF CELL FORMATION (Cont..)
Step 6a. Calculate the closeness ratio of the entering machine with each group that have already been formed. Closeness Ratio (CR) is defined as the ratio of the total of all relationships the entering machine has with the machines that are currently in a group to the total number of machines that are presently assigned to that group Entering machine is placed in a group that has the maximum closeness ratio (MCR), as long as this maximum is greater than or equal to the minimum threshold value (MTV), i.e MTV =Px RC. If the value of value of MCR is less than MTV, then a new group is formed consisting of two machines noted in step 4. which have relationship value that equals the present value of RC. Go to step 7
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19. TABULAR METHOD OF CELL FORMATION (Cont..)
Step 6b. Duplication of one or more machine is suggested . There are two possible alternatives & they are checked subsequently b/c of cost considerations. First alternative is to add one additional machine of either type & place it in appropriate cell; the 2nd alternative is to add two additional m/cs, one of each type, & form a new group or place the appropriate one in each of existing groups
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20. TABULAR METHOD OF CELL FORMATION (Cont..)
Step 7: Continue the check of machine-to-machine table with the present value of RC proceeding sequentially in rows. If an element is found that is equal to present value of RC, go to step 5. If no such element is found, go to step 8. Step 8: Check to see if all the positive values of RC greater than 0 are checked. If they are, go to step 9; other wise, reduce the value of RC to the next value in its descending order of magnitude & return to step 5. An other termination rule is to stop when all the machines are assigned to at least one group. This stopping rule keeps machine duplications to a minimum
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21. TABULAR METHOD OF CELL FORMATION (Cont..)
Step 9. This step involve group consolidation. Compare the groups formulated so far. If one group-say, G1-contains machine such that it is a subset of another group, then eliminate G1 from any further considerations.
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