SELECTION OF QUALITY ASSURANCE METHODS

• The next activity of process planner is to specify QA methods and

inspection criteria.
• The process planner Provides inspection criteria and quality engineer
decides QA tools and techniques.
• The overuse of QA methods and inspection has to be avoided, as it will
increase processing time and total manufacturing costs.
• Tasks of process planner:
- Identification of inspection locations
- Identification of suitable inspection and testing methods
- Determining frequency of inspection
- Evaluation of inspection and test data
- Identifying corrective action
 WHAT IS QUALITY?
 Totality of features and characteristics of product or service.
 Ability to satisfy stated and implied needs of customers.
DEFINE TQM?
 Management approach
- Quality
- Participation of all staffs
- Customer satisfaction
- Benefits to all members of organization and society
 BASIC PRINCIPLES OF TQM

1. TOP MANAGEMENT COMMITMENT

2. FOCUS ON CUSTOMER
3. EFFECTIVE INVOLVEMENT AND UTILIZATION OF
WORKFORCE
4. CONTINUOUS IMPROVEMENT
5. TREATING SUPPLIERS AS PARTNERS
6. ESTABLISHING PERFORMANCE MEASURES FOR
PROCESSES
ELEMENTS OF TQM
 BASIC QUALITY STRATEGIES

1. DETECTION STRATEGY
Strategy focuses on question, Are we making it correctly?
2.PREVENTION STRATEGY
Strategy focuses on question , can we make it correctly?
 SEVEN STATISTICAL TOOLS OF QUALITY (Q-7 TOOLS)
• Seven basic tools -Japanese quality guru ISHIKAWA
• Statistical techniques to facilitate successful accomplishment of quality
improvement objectives.
SL.NO QUALITY TOOLS

1. FLOW CHART

2. CHECK SHEET

3. HISTOGRAM

4. PARETO CHART

5. CAUSE AND EFFECT DIAGRAM

6. SCATTER DIAGRAM

7. CONTROL CHART
WHAT IS STATISTICAL QUALITY CONTROL?

 Statistical method of analyzing variations in the manufacturing

process in order to make it better and more effective.

 Only a certain number of samples are needed to determine

whether the products are acceptable.
TWO MAIL METHODS EMPLOYED IN SQC
1. Statistical Process Control (SPC)
2. Acceptance Sampling

 All manufacturing processes have some degree of inherent

variability.
 Four sources of variations:
-Processes, Materials, Operations and miscellaneous factors.
- Miscellaneous variations- environmental factors
(heat, light, radiation and humidity)
TYPES OF VARIATIONS
1.ASSIGNABLE CAUSES OF VARIATION
 Larger in magnitude and can be easily traced and detected
 Reasons:
a. Differences among machines
b. Differences among materials
c. Differences among processes
d. Differences in each these factors with time
e. Differences in relationship to one another.
 Objective of SQC- detecting assignable causes of variation.
 Once it is identified and eliminated , process becomes statistically
control.
2. CHANCE CAUSES OF VARIATIONS:
 They are inevitable in any process
 Difficult to trace and control
 All occur at random
 Random variations cannot be avoided
 Random Factors- human variability from one operation cycle, raw
material variation, fluctuation in working condition, lack of supervision
skills.
 Process operating under stable system of chance causes is in statistical
control.
 CONTROL CHARTS

 It is a graph that displays data taken over time and the

variations of this data.
 Uses of control charts:
-To check whether the process is controlled
statistically or not.
- To determine process variability
- To establish the process capability of
production process.
- To identify the type of variation that occurs.
- To determine the effects of process changes.
TYPES OF CONTROL CHARTS
1. Control charts for variables
2. Control charts for attributes.

1. Control charts for variables:

 Quality characteristics which are measured and expressed in
specific units of measurements
 Commonly used charts
-Average charts
- Range charts
-Standard deviation charts
2. Control charts for attributes
 Attributes refers to quality characteristics that conform to specifications or
do not conform to specifications.
 It monitors the number of defects rate present in sample.
 Commonly used charts
1) p-chart - Fraction rejected as non-conforming to
specifications
2) np-chart - number of non conforming items
3)c- chart - number of non conformities
4)u-chart - number of non conformities per unit
GUIDELINES FOR CHOOSING THE RIGHT CONTROL CHART
 PROCESS CAPABILITY

• It measures the output of the process and compares to customer

specifications.
• Def: Minimum spread of a specific measurement variation which will
include 99.7% of the measurements from given process.
• Process capability =6σ
• It’s Purpose is
a) Whether the process is capable of
meeting the specified tolerance limits.
b) Identifying why a process capable
is failing to meet specifications.
 INSPECTION AND MEASUREMENT
 OBJECTIVE
Inspection is the function of product quality.
 AIM
1) Sorting conforming and non conforming products.
2) Determine variations during manufacture.
3) Discover inefficiency during manufacture.
STAGES OF INSPECTION
a) Inspection of incoming materials (pre-production or input inspection)
• Checking or inspecting purchased materials and parts before using in
manufacturing.
• Takes place at supplier’s or manufacturers’s gate.
b) Inspection of production process
• Inspection during production or process inspection
• Inspection done while production process is simultaneously going on..
• At various work centres and at critical processing points.
• Advantage of preventing wastage of time and money on defective units
and preventing delays in assembly.

c) Inspection of finished goods

(post production or output inspection)
• Last stage when finished goods are inspected before marketing.
• Poor quality products may be either rejected or sold at reduced price.
 METHODS OF INSPECTION
1. 100% INSPECTION
2. SAMPLING INSPECTION
1) 100% INSPECTION
 When the number of parts to be inspected is relatively small.
 Every part is examined as per specification.
 Depending on examination, acceptance or rejection of the parts are done.
2) SAMPLING INSPECTION
 When inspection is costlier and not practical to test each piece .
 From a batch, a random sample is inspected and the whole batch is
accepted.
 If sample is not to desired specification, either piece by piece it is inspected
or rejected as a whole
 Statistical methods are employed.
 TYPES OF INSPECTION
1. INSPECTION OF VARIABLES - Quantified and measurable
2. INSPECTION OF ATTRIBUTES-Qualitative characteristics
 MEASUREMENT INSTRUMENTS
Measurement : The different types of quality characteristics that are to be
measured are
1. Dimensions, 2.Physical properties (Variables – measured)
3.Functunality 4. Appearance (Attributes – counted and checked)
1. MEASUREMENT INSTRUMENTS USED FOR VARIABLES INSPECTION
CHARACTERISTICS BASIC MEASUREMENT
INSTRUMENTS USED
MEASUREMENT OF 1. ENGINEER’S RULE
LENGTH 2. MICROMETERS
a)INTERNAL MICROMETER
b)CYLINDRICAL GAUGE
c) INTERNAL MICROMETER
3. DEPTH GAUGE
4. VERNIER CALLIPERS
5. VERNIER DEPTH GAUGE
6. VERNIER HEIGHT GAUGE
MEASUREMENT OF 1. BEVEL PROTRACTOR
ANGLES 2. SINE BAR

MEASUREMENT OF AUTOCOLLIMATOR
STRAIGHTNESS
MEASUREMENT OF FLATNESS INTERFEROMETER

2. MEASUREMENT INSTRUMENTS USED FOR ATTRIBUTES

INSPECTION
TYPES OF LIMIT GAUGES PURPOSE
1. PLUG GAUGES  CHECKING HOLES OF MANY
DIFFERENT SHAPES AND SIZES.
 ‘GO’ PLUG GAUGE – SIZE OF LOW
LIMIT OF HOLE
 ‘NO GO’ PLUG GAUGE –HIGH LIMIT
OF HOLE
 STRAIGHT CYLINDRICAL HOLES,
TAPERED, THREADED SQUARE HOLES
2. RING GAUGES  TEST EXTERNAL DIAMETERS
 ‘GO’ RING – MAXIMUM DIAMETER
 ‘NO GO’ RING- MINIMUM DIAMETER
3. TAPER  TEST TAPERS
GAUGES  BOTH PLUG AND RING STYLES
4.SNAP GAUGES  MEASURE EXTERNAL DIMENSIONS
(GAP GAUGES)  EXAMPLE : SHAFTS ARE CHECKED

5. THREAD  CHECK THE PITCH DIAMETER OF

GAUGES THREAD.
 PLUG THREAD GAUGES- INTERNAL
THREADS
 RING THREAD GAUGES – EXTERNAL
THREADS
6. FORM GAUGES  CHECK THE CONTOUR OF PROFILE

7. FELLER  CHECKING CLEARANCES BETWEEN

GAUGES MATING SURFACE

8. PLATE AND  THICKNESS OF SHEET METAL IS

WIRE GAUGES CHECKED- PLUG GAUGE
 WIRE DIAMETER – WIRE GAUGES
 SELECTING MEASURING INSTRUMENTS

1.Accuracy
2. Linearity
3. Magnification
4. Repeatability
5. Resolution
6. Sensitivity
7. Stability
 SET OF DOCUMENTS REQUIRED FOR PROCESS
PLANNING
• Assembly and components drawings of the product and bill of materials
• Specification of various machine tools available in the catalogues of machine
tools.
• Machining/ Machinability data handbook
• Catalogues of various cutting tools and tool inserts
• Sizes of standard materials available in market
• Charts of limits , fits and tolerances.
• Tables of tolerances and surface finish
• Tables of machine hour cost of all machine tools available.
• Tables of standard cost
• Table of allowances
• Process plans of certain standard components such as shafts, bushings, flanges etc
• Handbooks such as Design Data Handbook, Tool Engineers Handbook, etc
 ECONOMICS OF PROCESS PLANNING

DECISIONS MADE BY THE MANAGEMENT

1. Type of material
2. Type of manufacturing process
3. Volume of product to be manufactured
4. Make or buy a product
5. Design of a product
6. Classification of costs
 BREAK EVEN ANALYSIS
(COST –VOLUME –PROFIT ANALYSIS)
 Break even point – Point at which revenues and costs are exactly equal.
Determination of Break Even point , 1. The algebraic method
2. The graphical method
Margin of safety (in %) = Sales – Sales at BEP x 100
Sales
THE GRAPHICAL METHOD (BREAK EVEN CHART)
PROBLEM-1
The fixed costs for a factory for the year 2009-10 are Rs. 1,50,000 and the
variable cost is Rs.10 per unit produced. The selling price per unit is Rs.25.
Calculate the break even quantity.
PROBLEM-2
From the following data, calculate break-even point expressed in
terms of units and also the new break –even point, if selling price is
reduced by 10%
Fixed Expenses: Variable Expenses:
Depreciation -Rs. 1,25,000 Materials -Rs. 4 per unit
Salaries -Rs. 1,00,000 Labour - Rs. 2 per unit
Selling price -Rs. 15 per unit
PROBLEM-3
Process A has fixed costs Rs. 25,000 per year and variable costs of Rs. 13 per
unit, whereas process B has fixed costs of Rs. 10,000 per year and variable
costs of Rs.24 per unit. At what production quantity (Q) are the total costs of
A and B equal?
PROBLEM-4
The fixed costs for the year 2000-01 are Rs. 6,00,000 and the variable
cost is Rs.40 per unit produced. The selling price per unit is Rs.160.
Determine;
1) Break even point (a) in terms of physical units, and (b) in terms of
rupees.
2) If a sales volume of 5500 units has been expected, then what will the
profit (or loss) earned.
3) If a profit target of Rs. 1,20,000 has been budgeted, compute the
number of units to be sold.
4) If the company sells 6500 units, calculate the margin of safety and
profit.
1,20,000
PROBLEM -5
PROBLEM-6 : Brackets can be purchased on any of three machines
with costs
M/C A M/C B M/C C
Fixed cost per set up Rs. 1000 Rs. 2000 Rs. 6000
Variable cost per set up Rs. 30 Rs. 20 Rs. 10
Which machine should be used for production units upto 500 units
1. The given component drawing is analysed and important features
are identified.
2. Identification of sequence of operations involved.
3. Based on operations , the machines, cutting tools , measuring and
checking instruments are selected.

4. The cutting speed, feed and depth of cut are selected from data
book.
5. The process planning is complete with the documentation of all the
details in route sheet.