Use of the robust design methodology for identification of factors that contribute to the intensity of the “orange peel” aspect on painted bumper surfaces

Abstract Even with the considerable development of techniques for automotive paint in recent decades, the bumper is a car part that still has many problems related to the aspect of its painted surface. This study aimed to identify the clear coat application factors that affect on the intensity of orange peel appearance on painted bumpers surfaces and offer an optimum design of factors through the robust design methodology. In this research conducted in automated paint sector of a bumper company, the robust design helped in the identification of variability cause in a production process by applying an experiment and statistical techniques, in an agile and with little waste material way. The experiment tested various combinations of levels of the clear coat application factors (speed, flow, revolution per minute, operation voltage, atomizing air pressure) in the bumper samples. The intensity of the orange peel on coated surfaces samples was measured by a Wave Scan device that provides the wavelength reading as a function of two measures: Long Wave and Short Wave. The main results obtained by variance analysis of noise signal ratio showed that the factors that have significant effects on the value of the Short Wave response wavelength are: revolution per minute, operation voltage and the interactions flow*operation voltage and speed*operation voltage. The factors that significantly affected the response value of the Long Wave wavelength are: flow, atomizing air pressure, revolution per minute, operation voltage and the interaction speed*operation voltage. As a result of analysis of the noise signal mean, it is presented the factors optimum design: speed = 920 m / s; flow = 160 ml/min; atomizing air pressure = 180 bar; revolution per minute = 90 revolutions / minute; operation voltage = 180 kilovolts.

摘要 尽管近数十年来汽车涂装技术已取得长足发展，但汽车保险杠的涂装表面仍存在诸多外观质量问题。本研究旨在明确影响保险杠涂装表面橘皮纹（orange peel）强度的清漆（clear coat）施工参数，并通过稳健设计（robust design）方法得出最优参数组合。本研究依托某保险杠企业的自动化涂装车间开展，通过实验与统计技术，以高效低耗的方式识别出了生产过程中的变异性成因。实验针对保险杠试样，测试了清漆施工参数（喷涂速度、流量、转速、工作电压、雾化气压）各水平的多种组合。涂层试样表面的橘皮纹强度通过橘皮检测仪（Wave Scan）进行测量，该设备通过两项指标——长波（Long Wave）与短波（Short Wave）来输出波长读数。通过信噪比方差分析得到的主要结果显示：对短波响应波长值具有显著影响的参数包括转速、工作电压，以及流量与工作电压、喷涂速度与工作电压的交互作用；对长波响应波长值具有显著影响的参数则包括：流量、雾化气压、转速、工作电压，以及喷涂速度与工作电压的交互作用。通过信噪比均值分析，最终得到最优参数组合：喷涂速度=920 m/s；流量=160 ml/min；雾化气压=180 bar；转速=90 r/min；工作电压=180 kV。