Unit 8 Measurement and Quality CHAPTER 19 - QUALITY ASSURANCE AND CONTROL

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