ABSTRACT:
Man and machine constitute the two most important factors of any industry. Ideal assignment to both these units is a matter of great importance. The study consists of ideal man machine assignment in a flow shop. Man and machine charts are drawn to find ideal assignment to operators and machines. It also deals with minimization of idle block in machining the cylinder blocks of an automobile engine and gives a brief description about using line balancing techniques and cellular manufacturing to reduce idle time and improving productivity.

Introduction:

IDLE TIME IN MANUFACTURING:

IDLE TIME is a period of time during a regular work cycle when a worker or the machine is not active because of waiting for materials or instruction. Idle time may be present due to factors like
• Shortage of materials
• Machine Breakdowns
• Power failure
• Shortage of materials
• Sloppy production scheduling
• Operator not available, etc.

NEED FOR MINIMIZING IDLE TIME:
Idle times are a common feature of any industry. But these idle times have a lot of impact on productivity, i.e. if the idle times are less then the production levels are going to increase. But, in general cases, the idle times of the man or the machine are greater than expected and desired. These unexpected and undesired idle times cause a lot of losses to the industry. Hence it becomes quite desirable to decrease idle times.

SOME TERMINOLOGY USED:

PRODUCTIVITY:

It is the ratio of output to input. Total factor productivity is usually measured in monetary units. Rupees for example, by taking the rupee value of the output and dividing by the cost of the inputs. Alternatively partial factor productivity is measured based on individual inputs, labor being the most common. Partial factor productivity answers the question of how much output we can get from a given level of input.

EFFICIENCY:

It is the actual output of a process relative to some standard.
RUN TIME:

It is the time required to produce a batch of parts. This is calculated by the time required to produce each unit multiplied by the batch size.
SET UP TIME:

It is the time required to prepare a machine to make a particular item. Machines that have significant set up time will typically run parts in batches.

OPERATION TIME:

It is the sum of run time and set up time for a batch of parts that are run on a machine.
Operation time = set up time + run time

THROUGH PUT TIME:

Through put time includes the time that a unit spends actually being worked on together with the time spent waiting in a queue.
Through put time = operation time + time that the job waits in a queue

PROBLEMS IN MASS PRODUCTION LINES:

While dealing with problems of industry, it was assumed if the work element times are constant. In practice these times may be varying randomly due to factors like human variability, fatigue or carelessness on the operator’s part. Even in case of machine operations, the set up time or positioning time of the part or components could lead to random variations in individual work element times. Since assumed for a given fixed set of work element times, the effect of these variability are of tow fold.

(i) Greater idle time at some workstations, and
(ii) Reduction of the average production rate of the line.

For various combinations for man machine charts drawn it was observed that

A combination of 7 men for seven machines was not very useful as idle time for the operators was more than optimal.

Instead by using 1 man for two machines it was observed that the idle time for one of the operator decreased considerably but for other operator result was not the same.

When we considered three machines were to be handled by that operator the results were better than before but still idle time was considered to be more.

But when four machines we allotted to him it was observed that the percentage of utilization for that operator increased drastically.

So we can suggest that instead of using seven operators for seven machines it is lot more productive to use three operators.

ANALYSIS OF IDLE TIMES

In an entire day the broaching machine is in operation for a small portion of time. In that case it is advisable to use buffer storage for this machine, and once the required number of blocks has been machined this machine can be used for some other operation in the company.

As it was found that in a day horizontal boring machine could only produce around 190 components, if more production was required then this part of the work can be given for subcontracts. This will improve the productivity of the unit at the same time will increase the utilization time of both the machines and the labour.

Cellular manufacturing and line balancing techniques can be used to improve the productivity

SCOPE FOR STUDY:

While analyzing the idle times of the operators and the machines we suggested line balancing and cellular manufacturing techniques to be used for improvement of productivity. But we could only study this area briefly due to time constraint. There is a great scope for study and development in this area on line balancing and cellular manufacturing .

Participant : 5

Harsha Vardhan,Gitam, Vizag