Quality
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Transcript of Quality
Quality
Er.Sartaj Singh Bajwa
Quality
• Quality– The extent to which a product or service is able to
meet customer needs and expectations.• Customer’s needs are the basic standard for
measuring quality• High quality does not have to mean high price.
• ISO 9000– The quality standards of the International Standards
Organization.
Er.Sartaj Singh Bajwa
Quality Control Process
1-Prepration of policies regarding quality
2-Fixation of quality standard relating to material & process
3-Designing the production system
4-Inspection and control of materials
5-Inspection and control of process
6-Production of goods and services
7-Inspection of final product and service
Er.Sartaj Singh Bajwa
Objectives of Quality Control
• Increased sales volume• Increased profits• Improving the company`s image• Improving the production system• Better procurement of material• To reduce the cost of inspection and losses
Er.Sartaj Singh Bajwa
Quality Circles
• Small group of employees who meet regularly for solving problems related to cost , quality , efficiency , equipment ,tools etc.
• In QC it is believed that each individual worker is responsible for quality and productivity
Er.Sartaj Singh Bajwa
Inspection
• Process of examining an object for identification or checking it for verification of quality and quantity
• Functions Of Inspection :
1 – To maintain quality of RM , WIP , FG
2 – To locate the defective items
3 – To prevent losses
4 – To detect sources of weakness
Er.Sartaj Singh Bajwa
Types Of Inspection
• Vendor place inspection ( For raw material )
• In process inspection
1–Trial run inspection ( to check tool & M/C )
2–First off inspection(items produced at first step are checked )
3–Inspection by self control(checking the operations)
4–Floor inspection(semi-finished goods are checked)• Final inspection• Post sales quality evaluation ( items rejected by customers
should be analyzed)
Er.Sartaj Singh Bajwa
Control Charts
• Whole production line is divided in sub groups such that variation in the quality , in each sub group is attributed to some change
• Factors considered while making of the sub groups :
1- Each sub group should be homogeneous2- Sample should not be taken at regular
intervals
Er.Sartaj Singh Bajwa
Control Charts• Characteristics/Quality on Y axis• Quantity/number on X axis
Er.Sartaj Singh Bajwa
Interpretations of Control Chart
• If all the points lie within UCL & LCL then the process is said to be in control
• If one or more points lie beyond UCL & LCL then the process is said to be out of control
• If points lie predominantly on one side of the central line then we cannot derive any conclusion
Er.Sartaj Singh Bajwa
Types Of Control Charts
• Control chart for variables
1 – M or Mean charts
2 – R or Range charts
• Control chart for attributes
1-P chart (to calculate the number of defective items)
2–C chart (to calculate the number of defects)
Er.Sartaj Singh Bajwa
Control Chart For Variables
• When the quality characteristics is capable of direct quantitative measurement then the control chart is known as chart for variables.
• Eg life of an item , diameter of a screw• Variables in these charts should be such that it
can be measured and expressed in numbers.• It includes : Control chart for Mean
Control chart for Range
Er.Sartaj Singh Bajwa
Control Chart For Mean
• Basic assumption here is that variability of the characteristic is under control
• Mean(M) and standard deviation(sigma) of each sub group is calculated with size of the sample(n) to be known then Charts are given by :
UCL = M+3 (sigma/square root of n)
CL = M
LCL = M-3 (sigma/square root of n)
Er.Sartaj Singh Bajwa
Control Chart For Range
• Basic assumption here is that variability of the characteristic is out of control
• Value of d and standard deviation(sigma) of each sub group is calculated , with size of the sample(n) to be known then Charts are given by :
UCL = d2*sigma+3d3*sigma
CL = d2*sigma
LCL = d2*sigma-3d3*sigmaEr.Sartaj Singh Bajwa
Control Chart For Attributes
• In this we cannot have direct quantitative measurement and the items can be classified only as good or bad , accepted or rejected
• Eg quality of cloth
Er.Sartaj Singh Bajwa
Plotting the P Chart• Calculate p (fraction defective in the lot) in
sample of size n• p = no. of defective items found , q=1-p
total no. of items
Control charts are given by :
UCL = p + 3*square root of(pq/n)
CL = p
LCL = p – 3*square root of(pq/n)
Er.Sartaj Singh Bajwa
Plotting the C chart
• Calculate c ( average no. of defects per unit )
C= mean of the given frequency
Control charts are given by :
UCL = c + 3*square root of c
CL = c
LCL = c – 3*square root of c
Er.Sartaj Singh Bajwa