Manufacturing Simulation, Reverse-engineering and Virtual Optical Test Technologies Used to Improve Plastic Optical Lens from Injection Molding

綜合應用類比製造、逆向工程及虛擬光學測試技術來改進注塑成型的光學透鏡的照明效果

李衛珍(Weizhen Li) ； 王松浩(Songhao Wang) ； 楊俞青(Yu-Ching Yang)

《中國機械工程學刊》 38卷3期 (2017/06) Pp. 267-277

摘要

With the development of optical technology, the requirement of plastic lens’ manufacture precision was very high. However, due to shrinkage from injection molding process, it’s very difficult to produce satisfactory product especially for medium to large size. Traditional manufacture process for plastic optical lens was as follows: polishing the mold; injection molding and then optically testing. The cycle repeated several times until qualified lens was obtained. Quite a lot of processing attempts were conducted: using different mold materials; changing injection molding process parameters at trial stage; or even polishing the mold surface repeatedly to obtain specified precision. Although some achievements were made, but these processes still had the same shortcomings: lack of repeatability; time consuming; heavy physical labor and uneconomical. In this research, the error of plastic optical lens was corrected with modern engineering tools and even before actual mold was made. Through theoretical analysis as well as optical experiments, the combinations of Manufacturing Simulation (MS) with Reverse-engineering (RE) technology were proved very powerful in the quality improvement of injection molding optical lens. In the study, an optical lens sized □69×30 mm was designed first. Under ordinary injection molding conditions, the maximum deviation value from the originally designed contour in the X direction and Z direction respectively was 0.5529mm and 0.2714mm. With combination of MS and RE technology, the deviations were greatly reduced through only one correction and the deformations were mostly offset. The surface quality of the plastic lens was greatly improved. And the experiment proved this conclusion. Since the corrections could be made before the actual mold was made, this process was effective and economical for obtaining high-quality plastic lenses. Moreover, this technology could also be utilized to other plastic parts that were difficult to manufacture, especially for curved surfaces with high precision requirements.

關鍵字

plastic optical lens ； injection molding ； manufacturing simulation ； reverse-engineering ； virtual optical test

並列摘要

随着光学技术的发展，对塑料光学透镜的制造精度要求越来越高。但是由于透镜在模塑过程中容易产生收缩，要获得高质量的透镜存在困难，特别是尺寸偏大的透镜。传统的光学透镜制作过程大致如下：抛光模具成型面、注塑成型透镜，然后对透镜进行光学测试。要获得光学效果良好的透镜这一过程得反复多次。在实际生产过程中已经尝试很多方法去减少收缩变形：使用不同的透镜材料；在试制阶段试用不同的注塑模参数；甚至对模具成型表面反复抛光处理以获得理想精度。尽管取得一定成效，但是这些途径都有其缺点：缺乏可重复性、耗时长、劳动强度大且非常不经济。本文提出一种新的研究方法，该方法融合了现代工程的优点，把模拟制造（MS）及逆向工程（RE）结合起来，对透镜可能产生的由于收缩引起的几何误差在成型模具制造前进行及时补偿纠正，尽量降低透镜的形状误差。通过理论分析及实验验证，该方法对注塑光学透镜表面质量可以起到非常大的改进作用。该研究设计了一尺寸为∅ 69×30 mm 的平凸透镜，材质为PMMA，结合使用Matlab 对其曲面曲线进行设计，其曲面形状保证了光在指定平板上的照度的均匀性。在透镜的实际注塑成型过程中，在一般的注塑条件下，透镜在如图示的X、Y、Z 三个方向都产生收缩变形，X、Z 方向变形相对严重，分别达到0.5529mm 及0.2714mm，表面形状的变化导致光的照度均匀性大大降低。该技术通过模拟制造（MS）及逆向工程（RE）结合应用一次后，透镜变形量被大部分补偿，光的照度均匀性提高。而且非常关键的是这种高质量透镜表面可以在模具制造前获得，大大减少了注塑生产过程中的实际变形，体现了这种方法的高效性、经济性。最后通过对设计方案进行实物制作及光学实验模拟，发现结果与理论吻合。这种方法可以对有复杂曲面、高精度要求的塑料制件进行推广应用。