The process of anodising of aluminium pistons has been analysed. The analysis has been conducted with the use of a control chart, which is one of the traditional quality management tools. Its purpose is consistent and effective elimination of faults by means of identification of their actual causes and applying appropriate preventive measures. It has been determined that even the most complex control chart, the X̅ and R chart, can indicate problems within the anodising process and contribute to its improvement

A. Gazda

A. Pacana

N. Życzyński

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349METALURGIJA 57 (2018) 4, 349-352A. PACANA, A. GAZDA, N. ŻYCZYŃSKIMONITORING THE PROCESS OF ANODISING OF VW70U PISTONS USING THE CONTROL CHARTReceived – Primljeno: 2018-02-12Accepted – Prihvaćeno: 2018-05-20Preliminary Note – Prethodno priopćenjeA. Pacana – Rzeszow University of Technology, Faculty of Mechanical Engineering and Aeronautics, Rzeszow, PolandA. Gazda (agazda@prz.edu.pl), N. Życzyński - Rzeszow University of Technology, Faculty of  Management, Rzeszow, PolandThe process of anodising of aluminium pistons has been analysed. The analysis has been conducted with the use of a control chart, which is one of the traditional quality management tools. Its purpose is consistent and effective elimination of faults by means of identification of their actual causes and applying appropriate preventive meas-ures. It has been determined that even the most complex control chart, the X̅ and R chart, can indicate problems within the anodising process and contribute to its improvement. Key words: aluminium pistons, process of anodising, film thickness, control chartINTRODUCTIONDynamic market changes require using more ad-vanced and improved methods of production, employ-ing competent personnel and using management skills. [1] Although these requirements are very high, in prac-tice, most market leaders can skilfully adapt to the de-manding business environment. Therefore, quality management or lean manufacturing instruments are gaining in importance. The implementation of these methods and tools allows to lower the costs of produc-tion and improve the quality of products. Various meth-ods of quality improvement are available. [2-4] One of them is the use of a statistical process control (SPC) tool, such as the control chart. The grounds of the SPC method were developed in the 20th century by Walter A. Shewhart. [5] They are still helpful in controlling the changes and stability of the process. The major purpose of the SPC method is analysing the process in terms of its correct-ness and efficiency within the specified limits. The SPC method is used in supervising processes and delivery control, as well as in monitoring of measurement equip-ment. This tool ensures measurable effects, contributing to the reduction of various costs, from those related with the manufacturing process, and ending with the costs of complaints. Control charts enable to indicate specific areas for improvement and suggest corrective actions that would allow to avoid similar faults in fu-ture. Quality management procedure based on the use of the control chart has been conducted with a piston manufacturer from the Subcarpathian Region in Poland. The described tool has been used in stabilising the pro-duction process of a new piston, undergoing the anodis-ISSN 0543-5846METABK 57(4) 349-352 (2018)UDC – UDK 546.621:669.719:/621-24:531.717:658.562=111ing procedure. [6-8] This particular operation, due to difficult control, has been analysed with the use of a control chart. ANALYSISPurpose of analysisThe aim of the analysis was the assessment of stabil-ity of the anodising process performed on pistons to be introduced to production, with the use of the X-R con-trol chart. The preliminary step was the analysis of po-tential causes and effects of failures (FMEA), which indicated that one of the most significant potential sources of problems could be the thickness of the an-odic film. [9, 10] Stability of production process of other pistons have been analysed before. [11, 12] How-ever, those analyses concerned structural dimensions. [13, 14] Their purpose was to determine if, and to what extent, the difficult piston anodising process was out of adjustment. Anodising Anodising process is performed in the electrolyte with the following composition: Sulphuric acid 260-300 g/litre, Ecolyte HA 99,4 - 1218 g/l (oxalic acid 6,5-8,5 g/litre, boric acid 2,5-3,5 g/l), max. aluminium (Al) content 6 g/l, temperature -5 - + 9 º C.Optimum electrolyte composition parameters and optimum process parameters are as follows:I Electrolyte composition:sulphuric acid: 290 g/l,oxalic acid: 15 g/l,AlOx: 1:10 %;II Process parameters:Current strength: 4 A350A. PACANA et al.: MONITORING THE PROCESS OF ANODISING OF VW70U PISTONS USING THE CONTROL CHART METALURGIJA 57 (2018) 4, 349-352Time: 180 s,Temperature: 10 0C.The analyses have been conducted at the manufac-turing plant in Poland with the following types of pis-tons:VW 70A/; SN2 material,VW 70U/; S2F material (forged pistons). Methodology of analysisThe company uses 10 anodising lines, including 2 automatic and 8 manual. The anodising process is per-formed with 22 types of pistons. The company, in coop-eration with the Institute of Precision Mechanics in Warsaw, is performing a research project aimed at test-ing new technologies of anodising without the use of Cr6+. The goal is to obtain anodic film with lower coarseness. For that reason, the company decided to perform a thorough monitoring of the process. The re-quired parameters of anodic films of pistons manufac-tured at the described plant are as follows:thickness: 10-20 micrometres,hardness: > 270 HV,coarseness: Ra< 2,5um.This study focuses on the analysis of results of an-odic film thickness tests (it should be from 10 to 20 mi-crometres, as it has been specified above). The quantity of test pieces for analysis was deter-mined mainly on the basis of the costs of control, the character of the process, and also technical and organi-sational capabilities. Considering the method of collec-tion and the cost of that procedure, the average quantity of 1 test piece per shift has been determined. It would allow to get reliable data and results for further analyses and to avoid high costs of control. It has also been de-cided that test piece measurements would be performed in 4 repetitions. Each measurement was performed by the materials laboratory technicians with the use of ZEISS micro-scope. 200 x magnification and accuracy scale of 0,01 um were used. The test pieces were cut out using the Brilliant 250 cutter and then mounted in order to ensure appropriate position and quality of specimen.RESULTS AND DISCUSSIONCalculated using statistical formulas and statistical analysis IT tools, including Mnitab software.The test concerned anodising capability of the VW70U piston. Results and calculations are presented in Table 1 and Figures 1, 2.The spreadsheet presented in Figure 2 has been ob-tained. This model has been generated with Microsoft Excel software, due to its easy operation and costs sav-ings.The introduction of the X̅ and R control chart will allow to continue process regulation monitoring. The application of this statistical tool allows to take almost immediate actions if any hazardous deviations occur. It is comfortable for the manufacturer and facilitates con-stant improvement of products. The introduction of control charts in the described processes may be consid-ered a sort of experiment that allowed to extend the knowledge concerning, among others, the factors that may have effect on the quality of the process.One of the examples was the occurrence of devia-tions in the control chart of the VW70U pistons anodis-Table 1 Measurements per formed with VW70U pistonsTest piece No.Part No.1. 2. 3. 4.1 13,53 12,99 13,13 13,992 15,23 15,44 16,03 15,553 16,04 16,09 15,26 15,564 15,89 15,23 15,96 15,785 13,03 13,63 14,22 14,636 15,86 15,23 16,03 16,027 17,63 15,63 15,96 15,748 16,08 16,23 16,22 15,569 16,67 15,88 14,79 14,3010 14,77 14,13 16,32 13,2111 13,96 14,64 15,23 13,0312 17,01 16,25 14,99 17,2313 16,55 16,33 14,23 13,6614 14,53 14,36 15,36 15,1215 16,18 16,75 15,26 15,4516 16,89 15,52 15,26 15,4517 16,31 14,36 15,85 15,6318 15,86 15,03 16,23 14,0119 16,33 16,33 16,23 13,3320 13,12 14,95 14,56 16,25Figure 1  Normal distribution of anodic film thickness results for the VW70U piston  351A. PACANA et al.: MONITORING THE PROCESS OF ANODISING OF VW70U PISTONS USING THE CONTROL CHARTMETALURGIJA 57 (2018) 4, 349-352ing process. Regularly entered results indicated changes that could be verified, diagnosed and corrected. The company has decided that control charts would be intro-duced and used as tools for recording results, monitor-ing and improving the quality of company operations.It has also been agreed that control cards would be introduced in future for analysing other processes. Fur-thermore, the decision has been made that in the nearest time the control chart form would be supplemented with additional data, while in future the company would endeavour to get access to software dedicated mainly for statistical analyses. To sum up the conducted analy-ses, the system presented herein requires many im-provements, and above all, experience of the users.Skills in interpreting results and making appropriate decisions are also important. The use of the control charts has confirmed that anodising processes of select-ed piston types were properly adjusted, and good in terms of quality. CONCLUSIONThe described company is a manufacturer of pis-tons supplied to clients all over the world and used mainly in combustion engines. Buyers of pistons sup-plied by the company-based plant more often trust the quality of the delivered parts and resign from special verification. Figure 2 The X̅  and R control chart352A. PACANA et al.: MONITORING THE PROCESS OF ANODISING OF VW70U PISTONS USING THE CONTROL CHART METALURGIJA 57 (2018) 4, 349-352 Quality monitoring, performed mainly with the use of the Control Chart, has indicated that this particular change in the anodising process resulted in better aes-thetics of pistons and improved functional properties, mainly hardness, thickness and coarseness.The control chart, integrated with the Control Plan, has proved to be a quite effective quality control tool in piston manufacturing, including its integral part, that is the anodising process.REFERENCES[1] D. Zimon: Impact of the implementation of quality mana-gement system on operating cost for small and medium-sized business organizations affiliated to a purchasing group, International Journal for Quality Research 4 (2015), 551-563[2] A. Pacana, A. Gazda, D. Malindžak, R. Štefko: Study on improving the quality of stretch film by Shainin method. Przemysł Chemiczny 2 (2014), 243-246[3] A. Gazda, A. 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Etsion: Testing piston rings with partial laser sur-face texturing for friction reduction. Wear 7-8 (2006), 792-796 [9] K. Xu, L.C. Tang, M. Xie, et al.: Fuzzy assessment of FMEA for engine systems. Reliability Engineering & Sy-stem Safety 1(2002), 17-29[10] K.S. Chin, A. Chan, J. B. Yang: Development of a fuzzy FMEA based product design system. International Journal Of Advanced Manufacturing Technology 7-8 (2008), 633-649[11] W. Zhang, E. Becker, Y. Wang, et al.: Investigation of Scuffing Resistance of Piston Rings Run Against Piston Ring Grooves. Tribology & Lubrication Technology 5(2013), 50-55[12] F. Riddar, A.K. Rudolphi: Comparison of friction perfor-mance of four anodised aluminium surfaces for use in a clutch actuator. Wear 1-2 (2014), 227-233 [13] S.M. Goushegir, J.F. dos Santos, S.T. Amancio-Filho: In-fluence of aluminum surface pre-treatments on the bon-ding mechanisms and mechanical performance of metal-composite single-lap joints. 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Monitoring the process of anodising of VW70U pistons using the control chart

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