Ch36- Quality Assurance

7/29/2019 Ch36- Quality Assurance

1/17

Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.

ISBN 0-13-148965-8. 2006 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.

Chapter 36

Quality Assurance, Testing, and Inspection


2/17



Life Expectancy of Some Products


3/17



Demings 14 Points


4/17



Example of Robust Design

Figure 36.1 A simple example of robust design. (a) Location of two mounting holes on

a sheet-metal bracket where the deviation keeping the top surface of the bracket from

being perfectly horizontal is . (b) New location of holes where the deviation (keeping

the top surface of the bracket from being perfectly horizontal) is reduced to /2.


5/17



Taguchi Loss Function in Television Sets

Figure 36.2 (a) Objective-function value distribution of color density for television

sets. (b) Taguchi loss function showing the average replacement cost per unit to

correct quality problems. Source: Courtesy of G. Taguchi.

Loss cost k YT 2 2k

Replacement cost

LSL -T 2


6/17



Frequency Distributions

Figure 36.3 (a) A histogram of

the number of shafts measured

and their respective diameters.

This type of curve is called a

frequency distribution. (b) A

normal distribution curve

indicating areas within each

range of standard deviation.

Note: The greater the range, the

higher is the percentage of parts

that fall within it.

Arithmetic mean, x x1 x2 x3 xn

n

Standard deviation, x1 x

2 x2 x

2 xn x

2

n1


7/17



Frequency Distribution Curve

Figure 36.4 Frequency distribution curve showing lower and upper limits.


8/17



Statistical

Quality Control

Charts

Figure 36.5 Control charts

used in statistical quality

control. The process

shown is in good statisticalcontrol because all points

fall within the lower and

upper control limits. In this

illustration, the ample size

is 5, and the number of

samples is 1.5.


9/17



Constants for Control Charts

UCLx x 3x A2RLCLx x 3x A2R

UCLR D4R

LCLR D3R


10/17



Control Charts

Figure 36.6 Control charts. (a) Process

negins to become out of control because of

such factors as tool wear (drift). The tool is

changed and the process is then in statistical

control. (b) Process parameters are not setproperly; thus, all parts are around the upper

control limit (shift in mean). (c) Process

becomes out of control because of factors

such as a change in the properties of the

incoming material (shift in mean).


11/17



Unstable and Stable Processes

Figure 36.7 Illustration of processes that are (a) unstable or out of control and (b)

stable or in control. Note in sketch (b) that all distributions have lower standard

deviations and have means closer to the desired value. Source: After K. Crow.


12/17



Operating-Characteristics Curve used in

Acceptance Sampling

Figure 36.8 A typical operating-characteristics curve used in acceptance

sampling. The higher the percentage of defective parts, the lower is the

probability of acceptance by the consumer. There are several methods of

obtaining these curves.


13/17



Liquid-Penetrant Inspection

Figure 36.9 Sequence of operations for liquid-penetrant inspection to detect the presence

of cracks and other flaws in a workpiece. Source: Metals Handbook, Desk Edition.

Copyright 1985, ASM International, Metals Park, Ohio. Used with permission.


14/17



Magnetic-Particle Inspection

Figure 36.10 Schematic illustration of magnetic-particle inspection of a part with a

defect in it. Cracks that are in a direction parallel to the magnetic field (such as in

A) would not be detected, whereas the others shown would. Cracks F, G, and H

are the easiest to detect. Source: Metals Handbook, Desk Edition, Copyright

1985, ASM International, Metals Park, Ohio. Used with permission.


15/17



Radiographic Inspection Methods

Figure 36.11 Three methods of radiographic inspection: (a) conventional radiography,

(b) digital radiography, and (c) computed tomography. Source: Courtesy ofAdvanced

Materials and Processes, November 1990. ASM International.


16/17



Eddy-Flow Current Changes

Figure 36.12 Changes in eddy-current flow caused by a defect in a workpiece.

Source: Metals Handbook, Desk Edition, Copyright 1985, ASM International,

Metals Park, Ohio. Used with permission.


17/17



Basic Optical System for Detecting Flaws in Radiography

Figure 36.13 Schematic illustration of the basic optical system used in

holography elements in radiography for detecting flaws in workpieces. Source:

Metals Handbook, Desk Edition. Copyright 1985, ASM International, Metals

Park, Ohio. Used with permission.

Ch36- Quality Assurance

Documents

Transcript of Ch36- Quality Assurance