Determination of injection molding process window based on form accuracy of lens using response surface methodology

• Published in: International journal of advanced manufacturing technology 2014-11, Vol.75 (5-8), p.947-958
• Main Authors: Tsai, Kuo-Ming, Tang, Bin-Hong
• Format: Article
• Language: English
• Subjects: Accuracy; CAE) and Design; Computer-Aided Engineering (CAD; Curve fitting; Design factors; Design parameters; Engineering; Factorial experiments; Form accuracy; Industrial and Production Engineering; Injection molding; Lenses; Mechanical Engineering; Media Management; Molds; Original Article; Parameter identification; Plastics industry; Response surface methodology
• ISSN: 0268-3768; 1433-3015
• DOI: 10.1007/s00170-014-6185-9

The purpose of this study is to establish a process window of injection molding process for the optimal form accuracy of spherical lenses. First, the significant factors influencing lens form accuracy are identified by Taguchi parameter design. These key factors are used to perform full factorial experiments and to establish the response surface model. Next, the concave response surface of form accuracy is obtained by Central Composite Design via sequential searching. The curve fitting is then used to obtain the injection molding process window for given spherical lens form accuracy. As a result, the injection molding process window is elliptical, the best form accuracy is 0.3758 μm at the elliptical center when the mold temperature is 85 °C, the cooling time is 9.6 s, and the packing time is 1.9 s. The average error is 7.92 % based on experimental verifications for three mold temperatures. In addition, a lens with a form accuracy of 0.5 μm is taken as an example to validate the injection molding process window. The results show that the average error between the experimental data and the prediction values is 10.58 %. Therefore, the proposed method for constructing a process window is reasonably accurate.