Samadhan D. Bhosale, S.C.Shilwant, S.R. Patil / International Journal of Engineering Researchand Applications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.832-837832 | P a g eQuality improvement in manufacturing processes using SQC toolsSamadhan D. Bhosale1, S.C.Shilwant2, S.R. Patil31PG Student (Department of Mechanical Engineering), Sinhgad Academy of Engineering,Pune University, India.2Professor, (Department of Mechanical Engineering), Sinhgad Academy of Engineering,Pune University, India.3Assistant Professor, (Department of Mechanical Engineering), Sinhgad Academy of Engineering,Pune University, India.ABSTRACTThe aim of this paper is to apply thequality tools to find out the root causes of thequality problems related to manufacturing ofmechanical seal. The modes of defects onproduction line are investigated through directobservation on the production line and statisticaltools like Check sheets, Histogram, Paretoanalysis, Cause and Effect diagram etc are usedin enhancing the process by continuousmonitoring through inspection of the samples.The work shows utility of quality tools to find theroot causes of the problems and eliminate them.A case study has been carried out in ‘EKK EagleProducts India Pvt. Ltd’ company thatspecializes in manufacturing of mechanical seal.Keywords- Control Charts, Cause and effectdiagram, Histogram, Pareto Analysis, MechanicalSeal, Statistical Quality control.1. INTRODUCTIONQuality concepts have changed over time.Quality of product means the product must bewithin the acceptable limits. Edwards Deming,explained chain reaction in his book "out of thecrisis" published in 1986. The benefits from qualityand process improvements to organization are:a. Improved Qualityb. Less rework, fewer mistakes and hencecost decreasedc. Capture the market with better quality andlower priced. Improved Businesse. Improved productivity The most common process of continuousimprovement is the PDCA Cycle shown in “Fig.1”which was first developed by Walter Shewhart inthe 1920s and promoted by quality preceptors DrEdwards Deming. PDCA-cycle consists of fourconsecutive steps, as follows:• Plan – Perception for improvement• Do – Implementation of the changes that isdecided in the Plan.• Check – a) Control and measurement of processesand products in accordance with changes in previousstepsb) Policy, goals and requirementsc) Report on resultsd) Decision making• Act – a) Adoption of the changes or run throughPDCA-cycle againb) Repetition of cycle for continuous improvement.Figure 1. PDCA cyclePDCA-cycle is required in processimprovement. When the process improvement startswith careful planning results in corrective andpreventive actions supported by appropriate qualityassurance tools. Application of seven basic qualitytools in correlation with four steps of PDCA-cycle isshown in Table 1. As shown in Table 1, for problemidentification Flow chart, Cause-and-Effectdiagram, Check sheet, Pareto diagram, Histogramand Control charts can be used. For problemanalysis Cause-and-Effect diagram, Check sheet,Pareto diagram, Scatter plot and Control charts toolscan be used. When the team is developing a solutionfor analyzed problem Flow chart and Scatter plotcan be useful. For evaluation of results, Check sheet,Pareto diagram, Histogram, Scatter plot and Controlcharts can be used.
Samadhan D. Bhosale, S.C.Shilwant, S.R. Patil / International Journal of Engineering Researchand Applications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.832-837833 | P a g eTable 1. Seven basic quality tools (7QC tools) incorrelation with PDCA-cycle stepsSeven basicquality tools(7QC tools)Steps of PDCA-cyclePlanPlan,CheckPlan, Act CheckProblemidentificationProcessanalysisSolutionsdevelopmentResultevaluationFlow chart √ √Cause-and-effectdiagram√ √Check sheet √ √ √Paretodiagram√ √ √Histogram √ √Scatter plot √ √ √Controlcharts√ √ √.Receiving Inspection Stock parts Part Supply AssemblyFinal Inspection Packing In-Process Inspection Appearance CheckFigure 2. Process flow chartA case study has been carried out at EKKEagle Products India Pvt. Ltd to monitor the processof manufacturing mechanical seals. Process flowchart at EKK Eagle Products India Pvt. Ltdproducing mechanical seals is as shown in “Fig 2.”The data was collected for improving the quality ofmechanical seals and reducing the defects2. THE SQC TOOLSQuality tools can be used in all phases ofproduction process, from the start of productdevelopment up to product marketing and customersupport. The 7 QC Tools are simple statistical toolsused for problem solving. These tools weredeveloped by the Quality preceptors such as Demingand Juran. Ishikawa has stated that these 7 tools canbe used to solve 95 percent of all problems. Thefollowing are the 7 QC Tools:1) Histogram2) Check Sheet3) Pareto Diagram4) Brainstorming5) Cause & Effect Diagram6) Control Charts7) Scatter Diagram2.1. HistogramA histogram is one of the basic qualitytools. It is used to graphically summarize anddisplay the distribution and variation of a processdata set. A frequency distribution shows how ofteneach different value in a set of data occurs. Themain purpose of a histogram is to determine theshape of data set. We can present the sameinformation in a table; but the graphic presentationshows relationship. Based on the frequency ofdistributed values, one can come to a conclusionwhether the values falls within the specified valuesand gives a normal distribution curve out of it. This can be achieved by Histogram. It is a usefultool for breaking out process data into regions fordetermining frequencies of certain events orcategories of data.Typical applications of histograms in root causeanalysis include:1) Presenting data to determine which causesdominate2) Understanding the distribution ofoccurrences of different problems, causes,consequences, etc.Table 2 Shows Seal Ring height data of mechanicalseal. It shows the cell boundaries of Seal Ringheight and frequency of them. “Fig.3” showshistogram for Seal Ring height data of mechanicalsealTable 2. Cell boundaries of Seal Ring height dataClassCell Boundaries(mm)Frequency1 1.00 1.05 02 1.05 1.10 03 1.10 1.15 04 1.15 1.20 05 1.20 1.25 56 1.25 1.30 267 1.30 1.35 188 1.35 1.40 1
Samadhan D. Bhosale, S.C.Shilwant, S.R. Patil / International Journal of Engineering Researchand Applications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.832-837834 | P a g eFigure 3. Histogram of seal ring height data.2.2. Check Sheet.Data collection is important because it isthe starting point for statistical analysis. Thefunction of a check sheet is to present information inan efficient, graphical format. Check sheets help toorganize data by category. They show frequency ofeach particular value and their information. Checksheets are tools that make the data collection processeasier. Their power is greatly enhanced when theyare used in conjunction with other quality tools suchas histograms and Pareto analysis. The check sheetshown in Table 3 was created by tallying each typeof mode of defect of mechanical seal during aspecified time. It shows the type of defects and howmany of each type occurred during that period.2.3. Pareto analysisIt can be described as the 80/20 ruleapplied to quality-control. The 80/20 rule wasformalized by economist Pareto after studying thedistribution of wealth. He observed that about 80%of wealth was held by about 20% of the population.Joseph Juran applied this principle to quality-control. Pareto Analysis states that 80% of qualityproblems in the end product or service are caused by20% of the problems in the production or serviceprocesses. In practice it is beneficial to separate “thevital few” problems from “the trivial many”.2.3.1 Pareto ChartA Pareto Chart is simply a frequencydistribution (or Histogram) of attribute data. ThePareto Chart is named after Italian economistPareto; A Pareto Chart is a series of bars whoseheights reflect the frequency or impact of problems.The bars are arranged in descending order of heightfrom left to right. This means the categoriesrepresented by the tall bars on the left are relativelymore significant than those on the right. This barchart is used to separate the “vital few” from the“trivial many”. These charts are based on the Paretoanalysis which are useful for the user to focusattention on a few important factors in a process.Pareto chart shown in “Fig.4” wasconstructed based upon the data collected by checksheet shown in Table 3 for various modes of defectswith their respective frequency and percentage ofmechanical seal. The figure reveals that themechanical seal has vital few modes of defects andrepresents around 80 % of total cumulativepercentage of non-conformities.Figure 4. Pareto chart for mode of defectsTable 3. Check sheet for various modes of defectswith their respective frequency and percentage2.4 BrainstormingBrainstorming is a tool used by teams tobring out the ideas of each individual and presentthem in an orderly fashion to the rest of the team.The key ingredient is to provide an environment freeof criticism for creative and unrestricted explorationof options or solutions.Sr.no.Mode ofdefectProductionvolume(No.s)No. ofdefectivecomponents(No.s)% ofdefectCumulative qty(No.s)Cumulative %1SealRingpore93823528 35.22 528 35.222latexcoating 277 18.48 805 53.703MRchipping 232 15.48 1037 69.184 US leak 225 15.01 1262 84.195Projection 122 8.14 1384 92.326stationary leak 48 3.20 1432 95.537Dropsample 35 2.33 1467 97.868 load 7 0.47 1474 98.339 other 25 1.67 1499 100.00Total 93823 1499100.00 1499 100.00
Samadhan D. Bhosale, S.C.Shilwant, S.R. Patil / International Journal of Engineering Researchand Applications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.832-837835 | P a g eSome of the specific benefits of Brainstorming arethat it1. Encourages creativity. It expands thinking toinclude all aspects of a problem or a solution withwide range of options.2. Rapidly produces a large number of ideas byencouraging people to offer creative and justifiedideas.3. Equalizes involvement by all team members. Itprovides a nonjudgmental environment thatencourages everyone to offer ideas. All ideas arerecorded.The recommended sequence for conductingBrainstorming and some suggestions for conductingthe session effectively are provided below: Review the rules: describe how the session willbe conducted. Set a time limit: assign a timekeeper and datarecorder. State the topic: Write down and publicize it.Ensure that everyone understands it. Collect everyone’s ideas: After allowing a fewminutes for the participants to think about thequestion, ask them to give their ideas. Record ideas: Display the ideas where everyonecan see them. Having the words visible toeveryone at the same time avoidsmisinterpretation and duplication. Clarify each idea: After all ideas have beenpresented, to ensure that all members have thesame understanding of it. Eliminate duplications: Repeated ideas are to beeliminated.2.5 Cause & Effect DiagramProcess improvement involves takingaction on the causes of variation. A team typicallyuses Cause-and-Effect (C&E) diagrams to identifyand isolate causes of a problem. The late Dr. KauroIshikawa, Japanese quality expert, developed thetechnique and hence it is called as Ishikawadiagram.  The Diagram is a tool to showsystematic relationship between a result or asymptom or an effect and its possible causes. It is aneffective tool to systematically generate ideas aboutcauses for problems and to present them in astructured form.2.5.1 StructureThe symptom or result or effect for whichone wants to find causes is put in the dark box onthe right. The lighter boxes at the end of the largebones are main groups in which the ideas areclassified. Usually four to six such groups areidentified.Figure 5. Cause & effect diagramIn a typical manufacturing problem, thegroups may consist of five Ms - Men, Machines,Materials, Method and Measurement. The six MMoney may be added if it is relevant. In some casesEnvironment is one of the main groups. Importantsubgroups in each of these main groups arerepresented on the middle bones and these branchoff further into subsidiary causes represented assmall bones. The arrows indicate the direction of thepath from the cause to the effect. Brainstorming technique is therefore veryuseful in identifying maximum number of causes.The cause & effect diagrams shown in “Fig.5” wereconstructed by quality team and throughbrainstorming sessions involving all employeestaking part in the related production and testactivitiesCause and effect diagram shown in Figure5 shows major factors that can cause latex coatingdamage of cartridge of mechanical seal. Thediagram was constructed by quality improvementteam through brainstorming sessions involving alloperators taking part in the related production andtest activities.2.6 Control ChartControl charts are the one of the mostimportant and effective statistical tools fordetermining the process stability and variability. These charts contain the upper control limit andlower control limit .Control charts are statisticaltools used to analyze and understand processvariables, to determine a process’s capability toperform with respect to those variables and to
Samadhan D. Bhosale, S.C.Shilwant, S.R. Patil / International Journal of Engineering Researchand Applications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.832-837836 | P a g emonitor the effect of those variables on thedifference between customer needs and processperformance.Every process has variation that can beclassified as the result of either common causes orspecial causes. Common causes of variation areinherent in a process while variation created byspecial causes is not normally present in the process.Control charts are used to identify and distinguishbetween those two different causes of variation. Onegoal of using a Control Chart is to achieve andmaintain process stability.We get benefit from using a Control Chart when we1. Monitor process variation over time.2. Distinguish between special cause andcommon cause variation.3. Assess the effectiveness of changes toimprove a process.4. Communicate how a process performedduring a specific period.“Fig.6” shows X and R chart for Seal ring height ofmechanical seal. The figure illustrates naturalprocess limits controlled within specification limits(1.00 to 1.40 mm)Machine Name Finish Grinding M/cOperation Seal Ring GrindingCharacteristic Seal Ring HeightSpecification/ Tolerance 1.2 ± 0.2HourSampleX1 1.31 1.32 1.32 1.31 1.32 1.28 1.34 1.35X2 1.32 1.35 1.34 1.33 1.27 1.30 1.32 1.32X3 1.30 1.32 1.35 1.32 1.3 1.32 1.34 1.34X4 1.29 1.31 1.34 1.32 1.28 1.29 1.31 1.30X5 1.31 1.34 1.33 1.32 1.28 1.3 1.34 1.36X 1.306 1.328 1.336 1.320 1.290 1.298 1.330 1.334R 0.03 0.04 0.03 0.02 0.05 0.04 0.03 0.05X 1.318 UCL X 1.337 LCL X 1.2891.361.341.321.301.281.2220.127.116.11 2 3 4 5 6 7 8R 0.036 UCL ( R ) 0.0766 LCL ( R ) 00.080.070.060.050.040.030.020.0101 2 3 4 5 6 7 8Sub GroupsX & R Control Chart1 2 3 4 5 6 7 8AverageHeightRangeFigure 6. Control Chart2.7 Scatter DiagramIt is also called as scatter plot or X–Ygraph. A scatter diagram is a tool for analyzingrelationships between two variables. One variable isplotted on the horizontal axis and called independentvariable; the other is plotted on the vertical axis andcalled as dependent variable. The pattern of theirintersecting points can graphically show relationshippatterns. Scatter diagrams are used to evaluate causeand effect relationships. The assumption is that theindependent variable is causing a change in thedependent variable.3. RESULTS AND DISCUSSIONBefore implementation of SPC tools,production process at EKK Eagle products IndiaPvt. Ltd. was not in normal condition. After thetechniques were built into the process, themanagement and operators had understood the costwastage due to rejection of work piece.As seen from these studies, statistical processcontrol and statistical quality control were effectivein improving a process, irrespective of itsapplication, and are key success factors to stay inbusiness and the achievement of customersatisfaction and business excellence.1. A histogram is a picture of the datadistribution that includes its spread and shape.This can provide clues about the variation thatexists in the work performed. Histogram forSeal Ring height is normal and bell shaped. Itshows Cp is greater than 1.2. Check sheets help to organize rejection data bycategory.3. Pareto analysis states that 80% of rejection isdue to a) Seal Ring poreb) Latex coating damagec) Mating Ring Chipd) US leak4. Cause and effect diagram identify and isolatecauses of problems.5. Using control charts and by making changes inprocesses, we can make processes stable.4. CONCLUSIONIt has been shown that with use of basicquality tools, organization can monitor, control andimprove their processes. The seven basic qualitytools in general have demonstrated a great capacityin the improvement of manufacturing and serviceindustries across the world. There are basically fivereasons behind this:1. They are proven techniques for improvingproductivity;2. They are effective in minimization of defects;3. They prevent unnecessary process adjustments;4. They provide diagnostic information;5. They provide information about processcapability to meet customer requirements.REFERENCES Mohamed Aichouni, “On the use of thebasic quality tools for the improvement ofthe construction industry: A case study of aready mixed concrete production process”,International Journal of Civil &
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