Transcript DT1410 - Materials and Processes in Design

Unit 8
Measurement and
Quality
CHAPTER 19 QUALITY ASSURANCE AND CONTROL
-
Quality Assurance and Control
Quality Assurance maintains Product
Quality

Source Inspection before
Manufacturing

In-process Quality Control during
Manufacturing

Product Service and Warranties after
production
Quality assurance
All activities in manufacturing are
directed toward ensuring production
of a high-quality product.
Quality control
One segment of quality assurance
often responsible for dimensional
inspection (among others) during
production.
Source Inspection before
Manufacturing

Source of materials, parts, subassemblies

Sort out/reject poor quality material at the
source

Visual Inspection – color, texture, surface
finish, appearance

Metallurgical Testing – hardness, tensile
strength, etc.

Dimensional Inspection – measuring
tools/gages

Destructive/Nondestructive Testing –
stress/xrays

Performance Inspection – testing engines,
etc.
In-process Quality Control during
Manufacturing

Same checks as with Source Inspection

Sort out/reject poor quality parts/products

Receiving Inspection – parts/matls coming
in

1st Piece Inspection – after retooling; 1st part
off the line is inspected before production
begins

In-process Inspection – machine operator/
assembler inspects

100% Inspection – often used for critical
parts; too expensive for high-volume
production

Final Inspection – last chance
Non-dimensional Quality Control

Measure Power Output

Measure Radiation Output

Microwave, radio emissions,
interference
Product Service and Warranties
after production

Guaranty of product performance
after purchase

Warranty

A guarantee of product quality
provided by the manufacturer promising
parts, service, or replacement in the
case of a product failure.
Product Testing
PROTOTYPE STAGE
CONTROLLED MARKETS
ENDURANCE TESTING
Lean Manufacturing

Lean manufacturing or lean production, often simply, "Lean," is a
production practice that considers the expenditure of resources for any
goal other than the creation of value for the end customer to be wasteful,
and thus a target for elimination.

Working from the perspective of the customer who consumes a product
or service, "value" is defined as any action or process that a customer
would be willing to pay for.

Lean is centered on preserving value with less work.
Lean Manufacturing
http://www.youtube.com/watch?v=cOAKOCxRK8M
Unit 8
Measurement and
Quality
CHAPTER 20-INSPECTION AND MEASUREMENT
Inspection and Measurement
Why Measure a Product? >

Out of Spec Product =

Wasted production costs

Product failure or non-function


Liability for consequences
How a Product is Measured

Visual Inspection

Comparison Inspection

Measurement
Measurement standards
Known standards to which production
gages and other measurement tools
are periodically compared to ensure
their conformity and accuracy.

Gage blocks are an example.
Fixed gages
Instruments used for comparison
inspection that do not display a
reading.
Inspection
Inspection Instruments (Inspection)

Plugs, rings, templates

Steel rules, protractors

Micrometers, height gages, coordinate
measuring machines

Size Specifications and Locations
(Meas.)

Form Specifications (Meas.) (Fig. 20.30

Perpendicularity, squareness, flatness,
straightness, concentricity, etc.
Comparison Inspection

Fixed Gages (Fig. 20.5, .6, .7, .8)

Compare part to gage of correct spec.

“GO/NO GO” gages (do not display a
reading)
Screw-pitch gages and Radius Gages
(Fig. 20.9 & .10)
Worker simply compares, no reading or
interpreting data 
Many different gages required 
THINGS AFFECTING MEASUREMENT
PRECISION OF INSTRUMENT
Measurement,
Precision, and
Resolution-
Resolution
Reliability and Repeatability
Condition of Surfaces of Workpiece
Worker Skill
Temperature and other
environmental factors
Precision
Repeatability


The amount of size variation (range
variation) in the component or product
features created by a manufacturing
process.
No larger than 1/10 of the tolerance
range

Tolerance range = 0.010, then

Instrument precision = 0.001
Resolution
Smallest deviation the instrument can
detect.
Measuring Tools
Direct Reading Instruments (fig.s 20.13.23)


Deviation-type gages (fig.s 20.25-.32)


Micrometers, calipers, etc. - measure
whole distance (examine Calipers)
Measure only deviation from master
Transfer-type instruments

Telescoping hole gages (fig. 20.36)
Vernier scale
An added scale that improves the
resolution of micrometers and other
precision measuring instruments

mechanically magnifies tiny variations
in a dimension.
Measuring Tools
Semiprecision Tools

Steel rule – 1/64” accuracy (Fig. 2.12)

Combination set (Fig. 20.13)

Thickness gage (Fig. 20.14)

Rule-depth gage (Fig. 20.15)
Calibration
The processes of comparing
measuring instruments and gages
against known measurement
standards and then adjusting them to
conform with the standards.
CMM

Coordinate measuring machine


a computerized measuring instrument
that precisely tracks the movement of
a probe in three-dimensional space.
The CMM records the location of the
probe as it touches the workpiece,
making the CMM useful for
measurement of size, form, and
location.
Surface finish (surface roughness)
A form specification that determines
the smoothness of the minute peaks
and valleys that compose a
machined surface.
Temperature Effects

Temperature changes cause metals to
expand and contract – this affects the
accuracy of measurements

Standard measuring temperature is 68º
F
Interchangeability
The concept that parts manufactured
by many different manufacturers to
the same dimensional specifications
may be interchanged in assemblies.

Different parts of same assembly may
come from different manufacturers
Standards
Master Measurement Standards

Maintained by NIST

National Institute of Standards and
Technology (formerly NSB – National
Bureau of Standards)
Summary
Products must be Measured to ensure proper size and form

Measuring Tools used must allow repeatable and accurate measurements

Measuring tools may be direct-reading or “Go/No Go”

“Go/No Go” measuring tools allow for faster and more accurate comparisons

Direct reading instruments produce a readout – can be slow and can be
misread

“Go-No Go” instruments do not produce a readout but can be used more
quickly than Direct reading instruments

Semiprecision Measuring Tools rely on average eyesight to achieve
reasonable accuracy
Summary
Temperature changes cause metals to expand and contract – this affects
the accuracy of measurements


Standard measuring temperature is 68º F
Interchangeability – parts manufactured by many different manufacturers
to the same dimensional specifications may be interchanged in
assemblies.
Measuring with Dial
Calipers
Dial Calipers
Dial Calipers

Dial Calipers are arguably the most
common and versatile of all the precision
measuring tools used by engineers and
manufacturers.
Dial Calipers

Dial calipers are used to perform four
common measurements on parts…
1.
Outside Diameter or Object Thickness
2.
Inside Diameter or Space Width
3.
Step Distance
4.
Hole Depth
Dial Calipers
Outside Measuring Faces
These are the faces between which outside
length or diameter is measured.
Dial Calipers
Example: Outside Diameter of object
Dial Calipers
Inside Measuring Faces
These are the faces between which inside
diameter or space width (i.e., slot width) is
measured.
Dial Calipers
Example: Inside measuring
Dial Calipers
Step Measuring Faces
These are the faces between which stepped
parallel surface distance can be measured.
Dial Calipers
Example: Step
Distance
Dial Calipers
Depth Measuring Faces
These are the faces between which the depth
of a hole can be measured.
Dial Calipers
Example: Depth Measuring
Note: Work piece is shown in section. Dial Caliper shortened for graphic purposes.
Dial Calipers
Nomenclature
Dial Calipers
A standard inch dial caliper
will measure slightly more
than 6 inches.
Dial Calipers
The blade scale shows each inch divided into
10 increments. Each increment equals one
hundred thousandths (0.100”).
Dial Calipers
Slider
Blade
The blade is the immovable portion of the dial
caliper.
The slider moves along the blade and is used to
adjust the distance between the measuring
surfaces.
Dial Calipers
Pointer
The pointer rotates within the
dial as the slider moves backand-forth along the blade.
Dial Calipers
Reference Edge
The reference edge keeps
track of the larger increments
(i.e. 0.100”) as the slider
moves along the rack.
Dial Calipers
Rack
The gear-toothed rack is used
to change linear motion (slider)
to rotary motion (pointer).
Dial Calipers
READING THE INCH DIAL
CALIPER
Dial Calipers
The dial is divided
100 times, with each
graduation equaling
one thousandth of an
inch (0.001”).
Dial Calipers
Every time the pointer completes one rotation, the reference
edge on the slider will have moved the distance of one blade
scale increment (0.100”).
Dial Calipers
To determine the
outside diameter of this
pipe section, the user
must first identify how
many inches are being
shown on the blade
scale.
Dial Calipers
The reference edge is
located between the 1 and 2
inch marks. So, the user
makes a mental note…1
inch.
The user then identifies how
many 0.1” increment marks
are showing to the right of the
last inch mark.
In this case, there are 4…or
0.400”.
1.000”
0.400”
Dial Calipers
1.000”
0.400”
+ 0.037”
1.437”
Next, the user looks at the pointer
on the dial to see how many
thousandths it is pointing to.
In this case, it is pointing to 37…or
0.037”.
The user then adds the three
values together…
Dial Calipers
1.000”
0.400”
+ 0.002”
1.402”
How wide is the block?