Manufacturing Process - Aspects of Manufacturing

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Page 1: Manufacturing Process - Aspects of Manufacturing

LECTURE 2

~ ASPECTS OF MANUFACTURING ~

Prepared by:

En. Masjuri Bin Musa @ OthmanLecturer

Department of Design & InnovationFaculty of Mechanical EngineeringUniversiti Teknikal Malaysia Melaka

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SELECTING MANUFACTURING PROCESSESSELECTING MANUFACTURING PROCESSES 1

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SHAPES & COMMON METHODS OF PRODUCTIONSHAPES & COMMON METHODS OF PRODUCTIONSelected shape and production method:

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SELECTING MANUFACTURING PROCESSESSELECTING MANUFACTURING PROCESSES 2

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SELECTING MANUFACTURING PROCESSSELECTING MANUFACTURING PROCESSMany processes are used to produce parts with certain shapes. More than one methodof manufacturing can be used:

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SELECTING OF MATERIALSSELECTING OF MATERIALS 3

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- To design and manufacture a good, usable and dependable product:

i) Understand the various properties of the materials.

ii) Able to select the right materials for the right application.

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SELECTING OF MATERIALSSELECTING OF MATERIALS 4

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Consideration of selecting materials for products – Consideration of selecting materials for products – PROPERTIES OF MATERIALSPROPERTIES OF MATERIALS

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SELECTING OF MATERIALSSELECTING OF MATERIALS 5

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SELECTING OF MATERIALSSELECTING OF MATERIALS 6

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- Combination of mechanical & physical properties will create two kinds of ratio of materials,which are:

i) Strength to weight ratio of materials.

ii) Stiffness to weight ratio of materials.

- Both ratio of materials particularly are very important especially for the industries ofaerospace and automotive, as well as for sports equipment.

- For example: Aluminum, titanium, and reinforced plastics, generally have higher such ratiosthan steels and cast irons.

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SELECTING OF MATERIALSSELECTING OF MATERIALS 7

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ALLOY CASTABILITY WELDABILITY MACHINABILITY

Aluminum E F E,G

Copper G,F F G,F

Gray cast iron E D G

White cast iron G VP VP

Nickel F F F

Steels F E F

Zinc E D E

GENERAL MANUFACTURING CHARACTERISTICS OF VARIOUS ALLOYSGENERAL MANUFACTURING CHARACTERISTICS OF VARIOUS ALLOYS

Note: E-excellent; G-good; F-fair; D-difficult; VP-very poor.

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SELECTING MANUFACTURING PROCESSESSELECTING MANUFACTURING PROCESSES 8

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Consideration on the manufacturing process selected to produce parts.Consideration on the manufacturing process selected to produce parts.

1) Dimensional accuracy and surface finish.1) Dimensional accuracy and surface finish.

- The complexity of the dimensions as well as the shape of the part/product, affected theselection of the manufacturing processes.

- Example: Flat parts with thin cross-sections cannot be cast properly.

- Complex parts cannot be formed easily and economically, whereas they may be cast orelse fabricated from individual pieces.

- Dimensional tolerances and surface finish obtained in hot-working operations cannotbe as fine as those obtained in cold-working (forming at room temperature). This isdue to dimensional changes, warping, and surface oxidation occur during processingof materials at elevated temperatures.

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SELECTING MANUFACTURING PROCESSESSELECTING MANUFACTURING PROCESSES 9

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2) Operational and manufacturing cost.2) Operational and manufacturing cost.

- Other major consideration are the design and cost of tooling, the lead time required tostart production, and the effect of work piece material on tool and die life.

- Depending on product size and shape, the cost of tooling can be substantial.

- Availability of machines and equipment, and the experience of operating personnel arealso important cost factors.

- If these capabilities are not available, some parts have to be manufactured by outsidecompany (outsourcing).

- Example: automakers and appliance manufacturers.

- The quantity of parts to be made and the production rate (pieces per hour) are important in determining the processes to be used and the economics of production –project production, job shop, batch production or mass production.

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SELECTING MANUFACTURING PROCESSES/MATERIALSSELECTING MANUFACTURING PROCESSES/MATERIALS 10

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CONSEQUENCES OF IMPROPER SELECTION OF MATERIALS AND PROCESSESCONSEQUENCES OF IMPROPER SELECTION OF MATERIALS AND PROCESSES

A component or a product generally is considered to have failed when:

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SELECTING MANUFACTURING PROCESSES/MATERIALSSELECTING MANUFACTURING PROCESSES/MATERIALS 11

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SELECTING MANUFACTURING PROCESSESSELECTING MANUFACTURING PROCESSES

Example of the product: “Trek mountain bicycle”.

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SELECTING MANUFACTURING PROCESSES/MATERIALSSELECTING MANUFACTURING PROCESSES/MATERIALS 12

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As we plan the manufacture of any product, we need to answer the following questions:

- How do we choose the specific manufacturing processes?

- How do the materials selected influence the choice of manufacturing processes?

- Would product function or performance issues influence our choice processes?

- What criteria should we use to select processes?

- Which criteria are most important?

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TYPES OF MANUFACTURING PROCESSESTYPES OF MANUFACTURING PROCESSES 13

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Manufacturing processes can be categorized:

1) PRIMARY MANUFACTURING PROCESSES- Are used principally to alter the material’s shape or form.

- Example: Casting – to transform rectangular ingots of steel into cylindricalbrake drum.

Injection molding – to convert pellets of thermoplastic polyethyleneInto telephone handset.

Rolling – to flatten slabs of steel.

Sheet metalworking – to band steel sheets into refrigerator housings.

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2) SECONDARY MANUFACTURING PROCESSES- Used to add or remove geometric features from the basic forms.

- Example: the brake drum casting, undergoes secondary machining operationssuch as turning and grinding of the friction surface.

Refrigerator housings are frequently drilled or hole-punched.

In injection molded parts will have surplus flash-trimmed.

3) TERTIARY MANUFACTURING PROCESSES-Related to the surface treatments such as polishing, painting, heat treating, etc.

TYPES OF MANUFACTURING PROCESSESTYPES OF MANUFACTURING PROCESSES

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ASPECTS OF MANUFACTURINGASPECTS OF MANUFACTURING 15

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GLOBAL COMPETITIVENESS AND MANUFACTURING COSTGLOBAL COMPETITIVENESS AND MANUFACTURING COST

- The economics of manufacturing is one of the major consideration, due to global competitiveness for high quality product (world class manufacturing), and low priceshave become a necessity in worldwide markets.

- The following trends developed, have had a major impact on manufacturing:

Global competition increased rapidly, and the markets became multinational anddynamic.

Market conditions fluctuated widely.

Customers demanded high quality, low cost products and on time delivery.

Product variety increased substantially and products became complex, and product lifecycles became shorter.

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ENGINEERING METROLOGY & INSTRUMENTATIONENGINEERING METROLOGY & INSTRUMENTATION 16

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- Engineering metrology is defined as the measurement of dimensions such as length,thickness, diameter, taper, angle, flatness, profile, and etc.

- Post process inspection: measurement which made after the part has been produced.

- Real time inspection/in process/on line: measurement are being made while the part isbeing produced on the machine.

- Selection of measuring instruments are also depending on:

a) Size and type of parts to be measured.

b) The environment – temperature, humidity, dust, etc.

c) Operator skills required.

d) The cost of the equipment.

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ENGINEERING METROLOGY & INSTRUMENTATIONENGINEERING METROLOGY & INSTRUMENTATION 17

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GENERAL CHARACTERISTICS AND SELECTION OF MEASURING INSTRUMENTSGENERAL CHARACTERISTICS AND SELECTION OF MEASURING INSTRUMENTS

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- Factors contribute to the subsequent deviation in the dimension – can be due to:

i) Technical factor.

ii) Human factor.

- Static and dynamic deflections of the machine because of vibrations and fluctuatingforces.

- Distortion of the machine because of thermal effects caused by such changes as intemperature of the environment, of metal working fluid, and of machine bearings andvarious components.

- Wear and tear of tools, dies, and molds.

- Human errors and miscalculations.

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TYPES OF MEASUREMENTS & INSTRUMENTSTYPES OF MEASUREMENTS & INSTRUMENTS 19

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TABLE 35.1Sensitivity

Measurement Instrument m in.Linear Steel rule

Vernier caliperMicrometer, with vernierDiffraction grating

0.5 mm252.51

1/64 in.100010040

Angle Bevel protractor, with vernierSine bar

5 min

Comparative length Dial indicatorElectronic gageGage blocks

10.10.05

4042

Straightness AutocollimatorTransitLaser beam

2.50.2 mm/m

2.5

1000.002 in./ft

100Flatness Interferometry 0.03 1Roundness Dial indicator Circular tracing 0.03 1Profile Radius or fillet gage

Dial indicatorOptical comparatorCoordinate measuring machines

11250.25

40500010

GO-NOT GO Plug gageRing gageSnap gage

Microscopes Toolmaker’sLight sectionScanning electronLaser scan

2.51

0.0010.1

10040

0.045

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TYPES OF MEASUREMENTS & INSTRUMENTSTYPES OF MEASUREMENTS & INSTRUMENTS 20

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Vernier caliper

(a)

(c)

Analog micrometer

Digital micrometer

Dial indicators

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Bevel protractor(measuring angle)

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Vernier for anglemeasurement

The use of sine bar forprecision measurementof w/piece angle

TYPES OF MEASUREMENTS & INSTRUMENTSTYPES OF MEASUREMENTS & INSTRUMENTS

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Figure 35.7 An electronic gage for measuring bore diameters. The measuring head is equipped with three carbide-tipped steel pins for wear resistance. The LED display reds 29.158 mm. Courtesy of TESA SA.

Electronic gagesElectronic gages

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TYPES OF MEASUREMENTS & INSTRUMENTSTYPES OF MEASUREMENTS & INSTRUMENTS

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Figure shows (a) Schematic illustration of “out of roundness” (exaggerated). Measuring roundness using (b) V-block and dial indicator, (c) part supported on centers and rotated, and (d) circular tracing, with part being rotated on a vertical axis. Source: After F. T. Farago.

TYPES OF MEASUREMENTS & INSTRUMENTSTYPES OF MEASUREMENTS & INSTRUMENTS

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Figure shows a measuring profiles with (a) radius gages and (b) dial indicators.

Figure shows a measuring profiles with (a) radius gages and (b) dial indicators.

Measuring profilesMeasuring profiles

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TYPES OF MEASUREMENTS & INSTRUMENTSTYPES OF MEASUREMENTS & INSTRUMENTS

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Coordinate measuring machineCoordinate measuring machine

Figure shows (a) Schematic illustration of one type of coordinate measuring machine. (b) Components of another type of coordinate measuring machine. These machines are available in various sizes and levels of automation and with a variety of probes (attached to the probe adapter), and are capable of measuring several features of a part. Source: Mitutoyo Corp.

TYPES OF MEASUREMENTS & INSTRUMENTSTYPES OF MEASUREMENTS & INSTRUMENTS

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ENGINEERING METROLOGY & INSTRUMENTATIONENGINEERING METROLOGY & INSTRUMENTATION 26

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GEOMETRIC DIMENSIONING AND TOLERANCINGGEOMETRIC DIMENSIONING AND TOLERANCING

- Individually manufactured parts and components eventually are assembled into products.- Therefore, each of the mating parts, might be neither too tight nor too loose.

- Example: the replacement of a broken or worn bolt on an old machine.

Dimensional tolerances- Defined as the permissible or acceptable variation in the dimensions such as height,width, depth, diameter and angles, of a part.

- Tolerances are unavoidable – impossible to manufacture two parts that have precisely thesame dimensions.

- Close dimensional tolerances can increase the product cost and vice versa.

Importance of tolerance control- Some of the parts really need a very good control of tolerances.

- Dimensional tolerances are very important when the parts are to be assembled or mated to form a complete product.

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- Example: Assembly of a simple round shaft (axle) and a wheel with a round hole. Assumethat we want the axle’s diameter to be 25mm. If we go to any hardware storeslooking for this both axle and wheel, do we really can get the rod which can fit into the hole without forcing it or will it be loose in the hole?

- The 25mm dimension is known as the nominal size of the shaft. If we purchase such a rodfrom a different store, at a different time, and select one randomly from a large lot, thechances are that each rod will have a slightly different diameter.

- Machines with the same set up may produce rods of slightly different diameters, dependingon few factors, such as speed of operation, temperature, lubrication, and variations in theproperties of the incoming material.

- In this particular case, we need to have a range of diameter for both rod and the hole ofthe wheel.

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- Limits and fits are essential in specifying dimensions for holes and shafts.

- There are two standards on limits and fits, which are:i) traditional inch unit.ii) metric unit.

- Capital letters refer to the hole and lowercase letters refer to the shaft.

Inch units: Running and sliding fits, location clearance fits, location transition fits,location interference fits, force and shrink fits.

Metric units: clearance fits, transition fits, interference fits.

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QUALITY ASSURANCE & TOTAL QUALITY MANAGEMENT (TQM)QUALITY ASSURANCE & TOTAL QUALITY MANAGEMENT (TQM)30

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- The degree to which the design specifications for a product or service are appropriateto its function and use, and the degree to which a product or service conforms to itsdesign specifications.

- “Quality assurance” is defined as all actions necessary to ensure that quality requirementswill be satisfied.

- “Quality control” is the set of operational techniques used to fulfill quality requirements.

- It cover several types of parameters, such as dimensions, surface finish, tolerances, composition, and color, as well as mechanical, physical, and chemical properties.

- An important aspect of quality assurance is the capability to:

a) Analyze defects as they occur on the production line.

b) Promptly eliminate them or reduce them to acceptable levels. - QA involves evaluating the product and customer satisfaction.

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QUALITY ASSURANCE & TOTAL QUALITY MANAGEMENT (TQM)QUALITY ASSURANCE & TOTAL QUALITY MANAGEMENT (TQM)31

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- In order to control quality, we have to be able to:

Measure quantitatively the level of quality.

Identify all of the material and process variables that can be controlled.

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TOTAL QUALITY MANAGEMENT (TQM)TOTAL QUALITY MANAGEMENT (TQM)- TQM is a system which emphasizes the concept that quality must be designed and builtinto a product.

- The approach of this system:

Both management & employees make a concerted effort to consistently manufacturehigh quality products.

Leadership & teamwork in the organization are essential to ensure the goal of continuous improvement in manufacturing operations – thus reduce the productvariability & improve customer satisfaction.

Control the process & not the parts produced – so that the variability is reduced andno defective parts are allowed to continue through the production line.

- The concept of TQM’s system:

1) Quality circle.

2) Quality engineering as a philosophy.

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QUALITY ASSURANCE & TOTAL QUALITY MANAGEMENT (TQM)QUALITY ASSURANCE & TOTAL QUALITY MANAGEMENT (TQM)33

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1) Quality circle1) Quality circle

- Consists of regular meetings by groups of employees (workers, supervisors, engineers,and managers) – discuss about how to improve & maintain product quality at all stagesof the manufacturing operation.

- Worker involvement, responsibility, creativity, and team effort are emphasized.

- Comprehensive training is provided – worker can become conscious of quality and becapable of analyzing statistical data, identifying causes of poor quality, and taking immediate action to correct the situation.

2) Quality engineering as a philosophy2) Quality engineering as a philosophy

- The implementation of the quality concepts & methods which had a major impact onmodern manufacturing – philosophies of Deming, Juran, & Taguchi.

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History……….

- During WWII, a group which lead by Dr. W. Edwards Deming, developed new methods ofstatistical process control for wartime-industry manufacturing plants.

- The methods of statistical control arose due to the variations in the:

● Performance of machines and people.

● Quality & dimensions of raw materials.

- Deming was also looking for a new way in manufacturing operations – that is, from theperspective of improving quality while lowering the costs.

- Deming has came out with 14 ideas/points as a checklist or menu of task, in order toproduce high-quality goods.

- He emphasis more on communication, direct worker involvement, and education instatistics, and modern manufacturing technology.

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DEMING’S 14 POINTSDEMING’S 14 POINTS

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QUALITY ASSURANCE & TOTAL QUALITY MANAGEMENT (TQM)QUALITY ASSURANCE & TOTAL QUALITY MANAGEMENT (TQM)36

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QUALITY ASSURANCE & TOTAL QUALITY MANAGEMENT (TQM)QUALITY ASSURANCE & TOTAL QUALITY MANAGEMENT (TQM)37

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- Emphasized on:

Recognizing quality at all levels of an organization, including upper management.

Fostering a responsive corporate culture.

Training all personnel in how to plan, control, and improve on quality.

- An organization’s customers may be external (the end users who purchase the productor service), or they may be internal (the different parts of an organization that rely onother segments of the organization to supply them with products and services).

- “Planners” in the organization will develop the product & process designs to respond tothe customer’s needs.

- Later, all these plans are turned over to those who are in charge for the operations toimplement both quality control & continued improvement in quality.

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QUALITY ASSURANCE & TOTAL QUALITY MANAGEMENT (TQM)QUALITY ASSURANCE & TOTAL QUALITY MANAGEMENT (TQM)38

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- A method of controlling quality that emphasizes robust product design and the qualityloss function (QLF).

- QLF: The financial loss to society (customers) after the product is shipped, with the following result:

- QLF measure the success or failure of quality control.

Poor quality leads to customer dissatisfaction.

Costs are incurred in servicing and repairing defective products.

The manufacturer’s credibility in the marketplace is diminished.

The manufacturer eventually loses its share of the market.

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QUALITY ASSURANCE & TOTAL QUALITY MANAGEMENT (TQM)QUALITY ASSURANCE & TOTAL QUALITY MANAGEMENT (TQM)39

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Therefore, to satisfy customers, manufacturers should provide products with thefollowing characteristics:

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STATISTICAL PROCESS CONTROL (SPC)STATISTICAL PROCESS CONTROL (SPC) 40

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- If the number of parts that do not meet specification/set standards (which also knownas defective parts), and this phenomena happened during a production run, thereforewe must be able to determine the cause.

- The defect parts occurred might probably due to incoming materials, machine controls,degradation of metalworking fluids, operator boredom, and etc.

- SPC is an approach or technique which advises us to take certain measures and actions and when to take them in order to avoid producing further defective parts.

- The SPC consists the elements of:

1) Control charts and control limits.

2) Capabilities of the particular manufacturing process.

3) Characteristics of the machinery involved.

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0

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BETTER

109.07 Upper Control Limit 98.63 Process Average 88.19 Lower Control Limit

ANALYSISProcess average appears excellent, and can be little improvedupon. A very positive trend is evident when compared to mostprevious scattergrams. There remains some variation in thesystem but no data point is reported to be beyond controllimits. The sources of variation should be explored andremedied. The system is under statistical process control.

The Custodial Staff is to be complemented.

SCATTERGRAM FOR 01/ 25/ 02

NUMBER OF SITES VISITED

PER

CEN

T O

F SU

CCE

SS R

EPO

RTED

Lower Control Limit

Average

2000 READING MEAP SCATTERGRAM

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TEACHERS

PE

RC

EN

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MEAP READING 2002 and 2000 Scattergrams Imposed over 1996 Base Year Scattergram

Current Process Average

Lower Statistical Control Limit

121.81 Upper Control Limit78.82 Process Average [2002]35.98 Lower Control Limit

The process average appears good, but can be improved upon. While there remains a substantial amount of variation in the system, the range of variation has tightened and the process average over the most recent three years has improved from 66.41 to 78.82 percent.

BETTER

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- Control charts graphically represent the variations of a process over a period of time.

- It consist of data plotted during production, and typically there are two plots: x (averagefor each subset of samples taken/inspected) and R (range of the values in the samples).

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- The frequency of sampling depends on the nature of the process; some processes mayrequire continual sampling, whereas some may require only one sample per day.

Frequency distributioncurve

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¯ AND R CHARTS (SHEWHART CONTROL CHARTS)¯ AND R CHARTS (SHEWHART CONTROL CHARTS)xx

OVER TIME

MEA

SU

RE

MEN

T

process average

Upper Control Limit [UCL]

Lower Control Limit [LCL]

(VARIABLE CONTROL CHARTS)(VARIABLE CONTROL CHARTS)

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- When using variables control charts, there are two measures of interest:

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i) Central tendency.ii) Dispersion.

- In an application, it is generally necessary to ensure that the dispersion is in controlbefore examining the central tendency.

- The dispersion is controlled with the range (R) chart or the standard deviation (S) chart.

- The central tendency can be controlled with the mean (X-bar) chart.

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UCL = Process Average + 3 Standard Deviations

LCL = Process Average - 3 Standard Deviationsy

Central Line or Process Average CL

UCL

LCL

x

+ 3

- 3

TIME

Unacceptable Deviation, beyond control limits

Upper Control Limit

Lower Control Limit

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n – size of the sample (sometimes called a subgroup).

m – number of samples selected.

xi – average of the observation s in the i th sample (where: i = 1, 2, ….., m).

x – grand average or “average of the averages” (this value is used as the center lineof the control chart).

If x1, x2, …, xn is a sample of size n, then he average of this sample is

n

xxxx n21

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Ri – range of the values in the i th sample:

Ri = xmax – xmin

R – average range for all m samples.

Control limits for the x chart

UCL = x + A2R

Centre line = x

LCL = x - A2R

Note: A2 is found in Appendix VI for various values of n.

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Control limit for the R chart

UCL = D4R

Center line = R

LCL = D3R

Note: D3 and D4 are found in Appendix VI for various values of n.

The standard deviation equation will be:

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Figure shows control charts used in statistical quality control. The process shown is in statistical control because all points fall within the lower and upper control limits. In this illustration sample size is five and the number of samples is 15.

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(a) Process begins 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 set properly; 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).

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- It is a short trends in the data occur inrepeated patterns of the both peaks (highand low).- Causes of the cycles: temperature, humidity changes, operator fatigue, rotation ofoperators, electrical fluctuations, worn toolsor dies.

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- The changes occurs slowly.- Causes of the cycles: change in themaintenance program, introductionof new materials over time, changesin the fixtures.

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- In this case, the points tend to fall near tothe UCL and LCL, with the presence offluctuations near the middle.- Causes of the cycles: differences in materials, drifts in automatic control anddifferences in measuring equipment.

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- The cycles fluctuating naturally inside limits,which in very close to the CL.- Causes of the cycles: incorrect calculation ofthe control limits.

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- Occurs by an instantaneous change in onedirection or the other.- Causes of the cycles: change to a new typeof material, new operator, new machines.

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- Random fluctuation with more points nearthe UCL/LCL.- There could be a point rising followedby a point falling, or two points up followedby two points down.- Causes of the cycles: differences in testingequipment, differences in production lines ifsampling is on a rotation basis.

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- A continuous movement of observationsup or down.- Causes of the cycles: tool wear, aging ofmachinery, improper maintenance, changesin production quantities required, changesin operator techniques.

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FISH BONE DIAGRAM /CAUSE & EFFECT DIAGRAM/ISHIKAWA DIAGRAMFISH BONE DIAGRAM /CAUSE & EFFECT DIAGRAM/ISHIKAWA DIAGRAM

- Fish bone diagram is an analysis tool that provides a systematic way of looking at effectsand causes that create or contribute to those effects.

- Invented by Dr. Kaoru Ishikawa, a Japanese quality control statistician.

METHODS MATERIALS MANPOWER

MACHINESMOTHER NATURE(ENVIRONMENT)

MEASUREMENT

1) 6 M’s (recommended for manufacturing industry)

- More to the brainstorming session.

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2) 8 P’s (recommended for administration and service industry)

PRICE PROMOTION PEOPLE

PLACE POLICIES PROCEDURES

PROCESSES

PRODUCT(SERVICE)

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3) 4 S’s (recommended for service industry)

SURROUNDINGS SUPPLIERS

SYSTEMS SKILLS

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