# Statistical Process Control

Pages: 2 (459 words) Published: December 1, 2012
Standard Operating Procedure for inline Q.A, using Statistical Process Control charts

OBJECTIVE
To remove or minimize, cost of poor quality.

SCOPE
This procedure is applicable for all kind of critical points for which variable charts are being made to know about the process stability.

RESPONSIBILITY
1) Q.A. Manager
Q.A. Manager is responsible for allotting the critical points in a particular product to in line Q.A.’s.

2) A.Q.M.
A.Q.M. is responsible for carrying out the SPC effectively in their given lines. He is also responsible to assist the in line QA’s in case of any difficulty.

3) In Line Q.A.’s
In line Q.A.’s are responsible to fill the variable chart correctly and take appropriate actions required after depicting the charts.

PROCEDURE
✓ One Variable chart is to be prepared against each critical point. ✓ Take 5 samples at random produced in a particular hour and start measuring critical points on each sample. ✓ Write down the measurement difference as per the size-measurement specification given on variable chart in the period of that hour. ✓ After the five pieces are inspected, find out the median and range of these five readings by the following method. o Arrange the data in ascending order and write down the third no. in the median array for that particular hour. o To calculate range note down the difference between the maximum reading and minimum reading of that particular hour. Write it down in the range array. ✓ Calculate Upper Control Limit and Lower Control Limit by using the following formula: o Calculate X Bar for previous days 8 hours reading by following formula

X1+X2+X3+X4+X5+X6+X7+X8
X =
8
Where X1 ….. X8 are the median readings for previous day 8 hour.

o Calculate R for previous days 8 hours reading by following formula

R1+R2+R3+R4+R5+R6+R7+R8
R=
8...