Lo #4 manufacturing technology (jan 2016)

Manufacturing Technology 1
Manufacturing TechnologyManufacturing Technology
LO #4
Part 1 - Measurement & Inspection
- Reference e-textbook (Chapter #6, P. 131 ~ 153)

2Manufacturing Technology
Interchangeability
 One of the important aspects of parts manufacturing is
interchangeability of the produced parts.
 Interchangeable parts are parts that should be identical. They are
made to the specifications of the designer that ensure they are all
nearly identical and they can fit in any assembly of the same type.
 These parts can freely replace another, without any further
custom fitting such are filing or machining.
 This interchangeability allows easy assembly of new devices, and
easier repair of existing devices, while minimizing both the time
and skill required of the person doing the assembly or repair.
 The concept of interchangeability was crucial to the introduction
of the assembly line at the beginning of the 20th
century, and has
become a universal element of modern manufacturing.

Examples of Interchangeable parts
• Started in mass production assembly, the Ford Model T auto
parts.

Interchangeability & Dimensional Tolerance
 Interchangeability is determined by the dimensional tolerances
of the parts.
 Dimensional tolerances is the permissible variation in the
dimensions of a part.
 Tolerances are important because of their impact od the proper
functioning of a product, part interchangeability, and
manufacturing costs.
 The smaller the tolerances, the higher the production cost.
 But if the tolerances are higher than permitted this will lead to
poor product quality and functionality.

Measurement & Inspection
 A procedure in which an unknown quantity is compared with a
known standard, using an accepted and consistent system of
units.
- U.S. Customary system (U.S.C.S.)
- International System of Units (SI, metric system)
 Measurement provides a numerical value of the quantity of
interest within certain limits of accuracy and precision.
Measurement

Measurement & Inspection
 Inspection is a procedure in which a part or product
characteristic, such as dimension is examined to determine
whether it conforms to the design specification.
 Many inspection methods rely on measurement techniques,
while others use gauging method.
 Gauging (=Gaging) is faster than measurement, but provides
scant(=inadequate) information about the actual value of the
characteristic.
 In inspection part passes or fails.
Inspection

Quality - InspectionQuality - Inspection
- Coordinate metrology is concerned with the measurement of the actual
shape and dimensions of an object and comparing these with the desired
shape and dimensions.
- In this connection, coordinate metrology consists of the evaluation of the
location, orientation, dimensions, and geometry of the part or object.
- A Coordinate Measuring Machine (CMM) is an electromechanical system
designed to perform coordinate metrology.
Coordinate Measuring Machine (CMM)

8
QualityQuality
CMM quality depends on four(4) characteristics;
-Resolution : it specifies the CMM’s finest incremental reading.
-Repeatability : it also called precision, is that CMM’s ability to duplicate
a measurement. It is a function of machine stiffness.
-Accuracy : the lack of error in measurement, the difference between
what the CMM measures and what a perfect CMM would have measured.
-Linearity : the least effective measure of CMM quality. It checks the
machine for its movement along the three linear directions X, Y, and Z.
Manufacturing Technology

9
QualityQuality
CMM quality : Accuracy - Precision

Dimensional ToleranceDimensional Tolerance
It is defined as the permissible or acceptable variation in the
dimensions (height, width, depth, diameter, and angles ) of a
part.
Tolerances are unavoidable, because it is impossible and
unnecessary to manufacture two parts that have exactly the
same dimensions.
Dimensional tolerances become important only when a part
is to be assembled or mated with another part.

Dimensional ToleranceDimensional Tolerance
Engineering Golden Rule

Dimensional Tolerance -Dimensional Tolerance - MethodsMethods
 Allowances : the specified difference in dimensions between the
mating parts.
 Basic size : Dimension from which limits of size are derived with
the use of tolerances and allowances.
 Bilateral tolerance : The variation is permitted in both positive and
negative directions from the nominal dimensions.
 Unilateral tolerance : The variation from the specified dimensions
is permitted in only one direction, either positive or negative.
 Limit dimensions : Alternative method to specify the permissible
variation in a part feature size. They consists of the maximum and
minimum dimensions allowed.
 Zero line : Reference line along with the basic size from which a
range of tolerances and deviations are specified.
 Feature : A physically identified portion of a part, such as hole,
slot, pin, or chamfer.

Dimensional Tolerance -Dimensional Tolerance - MethodsMethods
Bilateral tolerance Unilateral tolerance Limit dimensions

Dimensional Tolerance –Dimensional Tolerance – Shaft & holeShaft & hole
Allowance=SPH-LPS
Max.Clearance
=LPH-SPS
(=LPH–SPH)
(=LPS–SPS)
LPH : Largest Possible Hole
SPH : Smallest Possible Hole
LPS : Largest Possible Shaft
SPS : Smallest Possible Shaft

DimensionalDimensional
Tolerance –Tolerance –
Shaft & holeShaft & hole

Dimensional Tolerance –Dimensional Tolerance – ISO 286 ; 1988ISO 286 ; 1988
-- ANSI B4.2 :1978ANSI B4.2 :1978
- EN 20286 : 1993- EN 20286 : 1993
 Deviation : Difference between the size and the corresponding
basic size. The basic size is assigned as limits of deviation. it is
same for both parts of their fits.
 Lower Deviation : Difference between the min limit of part's size
and corresponding basic size. It is designated "EI" for Hole, "ei" for
shaft.
 Upper Deviation : Difference between the max limit of part's size
and the corresponding basic size. It is designated "ES" for hole,"
es" for shaft.
 Fundamental Deviation : One of the deviations closest to the basic
size.
 Tolerance : The algebraic difference between the max and min
limits on the part.

Measurement InstrumentsMeasurement Instruments
Surface Plate
 A large solid block whose top surface is finished to a flat
plane.
 Most surface plates today are made of granite. Granite has
the advantage of being hard, non-rusting, non magnetic, long
wearing, thermally stable, and easy to maintain.

Graduated & Non-graduated measuring devices
 Graduated measuring devices include a set of markings
(called graduations) on a linear or angular scale to which the
object’s feature of interest can be compared for
measurement.
 Non-graduated measuring devices posses no such scale and
are used to make comparison between dimensions or to
transfer a dimension for measurement by a graduated
devices.

Steel Rule
 The most basic of the graduated measuring device.
 It used to measure linear dimensions.
 Rules are available in various length.

Calipers
 It is available in either non-graduated or graduated styles.
 Outside caliper & Inside caliper.
Non-graduated :
Inside & Outside
Outside - Graduated
Inside - Graduated

Vernier Caliper

Vernier Caliper – a reading example

Micrometer

Micrometer – a reading example

Vernier Height Gauge
 A height gauge is a measuring
device used either for
determining the height of
something, or for repetitious
marking of items to be worked
on.
 These measuring tools are
used in metalworking or
metrology to either set or
measure vertical distances; the
pointer is sharpened to allow it
to act as a scriber and assist in
marking out work pieces.

26
Dial Indicator
 It converts and amplifies the linear movement of a contact pointer
into rotation of a dial needle.

Dial Indicator – an example in Shaft Alignment
 Shaft alignment is the process to align two or more shafts with
each other to within a tolerated margin. It is an absolute
requirement for machinery before the machinery is put in service.
Types of misalignment
Methods of shaft alignment

Vernier Protractor – Angular Measurements
 A vernier protractor is used to obtain a very accurate
measurement of angles through the vernier scale.

Surface textureSurface texture
 Nominal surface ;
- It representing the intended surface contour of the part, and is
defined by lines, ideal circles, round holes, and other edges and
surfaces that are geometrically perfect.
 Surface texture;
- Surface Texture or Surface Topography is the local deviations of a
surface from a perfectly flat plane. The measure of the surface
texture is generally determined in terms of its roughness,
waviness, lay, and flaws.

 Roughness; refers to the small, finely spaced deviations from the
nominal surface that are determined by the material
characteristics and the process that formed the surface.
 Waviness ; is defined as the deviations of much larger spacing;
they occur because of work deflection, vibration, heat treatment,
and similar factors. Roughness is superimposed on waviness.
 Lay ; is the predominant direction or pattern of the surface. It is
determined by the manufacturing method used to create the
surface, usually from the action of cutting tool.
 Flaws ; are irregularities that occur occasionally on the surface;
these include cracks, scratches, inclusions, and similar defects in
the surface.

LO #4 Measurement & Inspection :
Part 2 - SPC (Statistical Process Controls)
- Reference e-textbook (P. 1061 ~ 1064)

Statistical Process Control
Terminology
UCLUCL
LCLLCL
Statistical process control (SPC)
involves the use of various
statistical methods to assess and
analyze variations in a process.
SPC methods include simply
keeping records of the production
data, histograms, process
capability analysis, and control
charts. Control charts are the most
widely used SPC method.
Groover, Mikell P. Fundamentals of Modern
Manufacturing: Materials,

Process Capability and Tolerance
 In any manufacturing operation, variability exists in the process
output. In a machining operation, which is one of the most
accurate processes, the machined parts may appear to be
identical, but close inspection reveals dimensional differences
from one part to the next. Manufacturing variations can be divided
into two types ; random and assignable.
 Random variations are caused by many factors: human variability
within each operation cycle, variations in raw materials, machine
vibration, and so on. It is normal statistical distribution. It said to
be in Statistical Control.

Process Capability and Tolerance
 Assignable variations indicate an exception from normal operating
conditions. Something has occurred in the process that is not
accounted for by random variations. Reasons for assignable
variations include operator mistakes, defective raw materials, tool
failures, machine malfunctions, and so on. Assignable variations
in manufacturing usually betray themselves by causing the output
to deviate from the normal distribution. The process is no longer
in statistical control.

Terminology
A control chart is a graphical technique in which statistics computed
from measured values of a certain process characteristic are plotted
over time to determine if the process remains in statistical control. The
general form of the control chart is illustrated in Figure 40.1. The chart
consists of three horizontal lines that remain constant over time: a
center, a lower control limit (LCL), and an upper control limit (UCL).
The center is usually set at the nominal design value. The upper and
lower control limits are generally set at +/-3 standard deviations of the
sample means.

Basic types of Control Charts
 Control charts for variables require a measurement of the quality
characteristic of interest.
 Control charts for attributes simply require a determination of
whether a part is defective or how many defects there are in the
sample.
Control Charts for Variables
 The x-chart (call it “x bar chart”) is used to plot the average measured
value of a certain quality characteristic for each of a series of samples
taken from the production process. It indicates how the process mean
changes over time.
 The R-chart plots the range of each sample, thus monitoring the
variability of the process and indicating whether it changes over time.

Process Control Charts – An Example
11 22 33 44 55 66 77 88 99 1010
Sample numberSample number
UpperUpper
controlcontrol
limitlimit
ProcessProcess
averageaverage
LowerLower
controlcontrol
limitlimit
Out of controlOut of control

A process is in control if……
1. … no sample points outside limits
2. … most points near process average
3. … about equal number of points above and
below centerline
4. … points appear randomly distributed

X-bar Chart

X-bar Chart Example

X-bar Chart Example (Cont.)

Statistical Process ControlR - Chart

Statistical Process ControlR – Chart Example

Statistical Process ControlR – Chart Example (cont.)
∑R
k
R = = = 0.115
1.15
10
UCL = D4R = 2.11(0.115) = 0.243
LCL = D3R = 0(0.115) = 0
Retrieve Factor Values D3 and D4

Statistical Process ControlR – Chart Example (cont.)
UCL = 0.243
LCL = 0
Range
Sample number
R = 0.115
|
1
|
2
|
3
|
4
|
5
|
6
|
7
|
8
|
9
|
10
0.28 –
0.24 –
0.20 –
0.16 –
0.12 –
0.08 –
0.04 –
0 –

Statistical Process ControlSequence to solve problems

Statistical Process ControlExample

LO #4 Measurement & Inspection :
Part 3 – Fit, Limits & GT (Geometric Tolerance)
- Reference pages in e-textbook
(P. 96 ~ 97 & 834 ~ 837 )

Fit and Limits
 Clearance : The space between mating parts.
 Fit : The range of looseness or tightness that can result from
the application of a specific combination of allowance and
tolerance in design of mating-part feature.
Terminology
 Clearance fit : Fit that allows for rotation or sliding between
mating parts.
 Transition fit : A fit with small clearance or interference that
allows for accurate location of mating parts.
 Interference fit : A fit having limits of size so that
interference always results when mating parts assembled.

Fit and Limits
Examples of Fit
 Clearance fit : Bicycle chain
– Clearance required
between pins and bushes.
 Transition fit : Crank shaft joints –
Crank shaft must run with minimum
least clearance to avoid vibration.
 Pump shaft & casing assembly by
press machine

Fit and Limits
Examples of Fit
 Interference fit: Shrink – fitting
Shrink-fitting is a technique in which an interference fit is achieved by
a relative size change after assembly. This is usually achieved by
heating or cooling one component before assembly and allowing it
to return to the ambient temperature after assembly, employing the
phenomenon of thermal expansion to make a joint

Fit and Limits Examples of Fit

 MMC (Maximum Material Conditions) : The point at which a feature
contains the most amount of material within its acceptable size
limit. The smallest acceptable hole and the largest acceptable
shaft are examples of MMC.
 LMC (Least Material Conditions) : The point at which a feature
contains the least amount of material within its acceptable size
limit. The largest acceptable hole and the smallest acceptable
shaft are examples of LMC.
Fit and Limits

Maximum Material Condition
Least Material Condition
Fit and Limits

Examples of FitFit and Limits

Examples of Fit
 When the specified size limits of mating part features always result
in clearance at assembly, the parts are said to have a clearance fit.
EXAMPLE: In the drawing above, even when the fastener is at its
MMC size of .747 and the hole is at its MMC size of .750, there is
clearance.
 When the specified size limits always produce interference at
assembly, mating part features are said to have an interference fit.
EXAMPLE: In the center drawing, even when the fastener is at its LMC
size of .5012 and the hole is at its LMC size of .5007, there is
interference.
 When mating part features do not fit together in their maximum
material condition, but do fit at some point as they approach their
least material condition, they are said to have a transition fit.
EXAMPLE: In the drawing on the right, when the fastener is at its
maximum material condition size of .5003, it will not fit the hole at
its MMC size of .5000. However, when both features are
manufactured at their least material condition size, they will fit
Fit and Limits

Fit and Limits
The hole-basis Vs Shaft-bases system

Fit and Limits
The hole-basis system

Fit and Limits

The hole
-basis system

Geometric Tolerance & Symbols
 A Datum is a reference point, axis, or plane is identified in the
engineering drawings, it is used to measure and specify the part
features or measurements from.
 It is a theoretical exact feature from which dimensions may be
taken.
 A Datum is generally chosen as an edge or feature which has the
greatest influence in a specific measurement.
Terminology

Geometric Tolerance & Symbols
 Geometric Dimensioning and
Tolerancing (GD & T) : GD & T
method is used to control
location, form, profile,
orientation, and run out on a
dimensional feature. Its
purpose is to ensure proper
assembly and/or operation of
parts, and especially useful in
quantity production of
interchangeable parts.
Terminology

Geometric Tolerance – Symbols & Tolerance Characteristics
 Straightness

 Flatness
 Circularity
(Roundness)

 Cylindricity
 Profile
– Line & Face

 Parallelism

 Angularity

 Perpendicularity

 Position
- Line
- Holes

 Concentricity
 Symmetry

 Run-Out

Ex) Bearing Housing
Section dwg.
ISO dwg.

Lo #4 manufacturing technology (jan 2016)

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