Page 213 - DMGT501_OPERATIONS_MANAGEMENT

Unit 7: Process Control Charts

By clicking on the right mouse button, and by selecting ‘Add Text’ one can add texts in the Notes
desired box.

Going back to the ‘connecting rod’ problem, let us also examine the flow diagram. Low Alloy
steel billets were stored in the billet yard. These came from GKW in Calcutta by trucks, each truck
carrying 10 tonnes of billets.
As the weight of the cut piece for the ‘connecting rod’ was around 1.50 kg. both in the case
of the drop forging and press forging, there was no impact on the forging process due to the
incoming billets. However, the cost of inventory (work in process) was higher for the forging

press, because a larger quantity was on the shop floor with value addition. There was a 5 per cent
increase in cost.
On studying the process, it was found that:
1. There was nearly 20 per cent less machining required for components manufactured by

press forging. This reflected a saving of around 17 per cent in cost of the component, but
2. If the cost of the forging were the criteria, it was more economical to manufacture it by
‘drop forging’; and
3. If the cost of the machined component was the criteria, it was more economical to use
‘press forging’. Machining costs were lower by 10 per cent.

The amount of metal that is required to be removed during machining is greater in drop forged
components, as press forgings provide better tolerances. Management has to find a solution as to

which process should be chosen and why.
How does one decide whether to use a drop hammer or a forging press for the manufacture of
a ‘connecting rod’? Higher production rate is desirable, and so are the lower capital costs and
maintenance costs. The results of the analysis carried out by the Division showed that it was
cheaper to manufacture the ‘connecting rod’ by drop forging compared to ‘press forging’. There
was a difference of 7 per cent in the cost.

7.2 Process Flow Charts

A Process Flow Chart is a tool that categorizes each activity and provides operation details to
understand the process.
Generally, the operations are summarized in sequence so that the pattern of operations can be
observed. If the sequence of activities varies from one job to the next, then that too provides useful

information about the operations. The information is provided in a typical process flowchart,
shown in Table 7.1. Note that more space is provided to give a detailed description of the nature
of each operation in the last column.

Table 7.1: Sample Process Flow Chart

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