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Unit 8 Measurement and QualityCHAPTER 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 TestingPROTOTYPE 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 QualityCHAPTER 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
Measurement, Precision, and Resolution-
THINGS AFFECTING MEASUREMENT PRECISION OF INSTRUMENT
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)
Micrometers, calipers, etc. - measure whole distance (examine Calipers)
Deviation-type gages (fig.s 20.25-.32)
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
Outside Measuring FacesThese 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
Note: Work piece is shown in section. Dial Caliper shortened for graphic purposes.
Example: Depth Measuring
Dial Calipers
Dial CalipersNomenclature
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
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.
Slider
Dial Calipers
Pointer
The pointer rotates within the dial as the slider moves back-and-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
Dial Calipers READING THE INCH DIAL CALIPER
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.
1.000”0.400”
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”.
Dial Calipers
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”.
1.000”0.400”0.037”
The user then adds the three values together…
+1.437”
Dial Calipers
How wide is the block?
1.000”0.400”0.002”+1.402”
Dial Calipers