cell formation in group technology there are numerous methods available for machine grouping in...

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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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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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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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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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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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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 groupEntering 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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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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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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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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cell formation in group technology there are numerous methods available for machine grouping in...

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