17 April 2014

Quality Control

Steps used in quality control:
1.     Define the quantity specification as given by customers.
2.     Measure actual quality from the process.
3.     Comparison of actual quality with the specified quality.
4.     Whenever there is derivation or variation between them, then take appropriate corrective action.

Every manufacturing process has got variability. The variability is of two types:
1.     Process is under chance cost
2.     Process is under assignable cost
Chance cost is random, i.e. even though the process is controlled very well, under identical conditions, but even though every item is varied in dimensions than the other. This variation has to be accepted because of chance cost. Variation due to assignable cost is not accepted. This concept is used in SQC (Statistical Quality Control) as follows:
·        We draw control charts
A control chart consists of 3 straight horizontal lines. Middle line is called x bar which is avg of avg of sample means. Upper control line & lower control line are called as decision criteria lines which are away from central line x bar at a distance of 3 бs. The sample points drawn at regular interval from the production process are plotted on these graphs.
Inference: If all the sample points drawn are lying within the 2 control lines then, we say, process is under statistical control i.e. the process is under chance cost only, but if any 1 of the point falls beyond the control limit, it gives  a signal that process is going out of control statistically, i.e. assignable cost is introduced in the system, therefore the process is to be stopped at that point & corrective action is taken. Take correct action so that sample points will lie between 2 control limits. This process is called as Statistical Process Control.


TQM is an integrated approach of the organization in delighting the customer (both, Internal & External) by not only meeting, but exceeding their expectation on a continuous basis through everyone involved in the organization on continuous basis in order to improve products, services & processes along with problem solving methodology.