Reject Rate Less Than .5 Percent for Optical Lenses and Systems

The Taiwanese company E-Pin Optical Industry Co. Ltd. was founded in1979 in Taipei and initially manufactured glass lenses and prisms for thecamera industry. With the addition of injection moulding machines and amouldmaking department in 1985, production of precision plastic lenseswas initiated (Figure 1).

IMI visited the E-Pin production facility in Y-Ilan, Taiwan, to learnhow the company succeeded in gaining such customers as Canon, Ricoh, Nikon,Minolta, Sony, Matsushita, Olympus, Philips, AT&T, Murata, Vision,and Minton from all branches of the optical industry and how, with 25 employeesin Taipei and 115 employees in Y-Ilan, it manages to post annual salesof some US$ 10 million.

Research and development, along with stability and quality in the productionprocess and strict testing of parts, are part of the management conceptof Shan-Woei Shyu, the president and sole owner of E-Pin. Components withplastic lenses and prisms (Figure 2)

account for most of the sales volume. Additional manufacturing stepssuch as coating of lenses, printing of lenses, and fabrication of componentsfor the camera industry were continually requested by customers. Developmentof double lenses and the camera viewfinder forced E-Pin to start assemblingcomponents into complete units for its customers (Figure 3). Since 1989E-Pin has designed and manufactured entire optical systems. "Actually,we are a systems supplier with in-house moulding," says Shyu. Besideslenses and prisms, the "heart" of the optical systems, E-Pinnow moulds all necessary functional parts such as transport rollers, levers,snap connectors, frames, threaded bushings, and the housing itself. Onlyelectronic circuits and metal components are supplied by outside vendors.

In addition to the plants in Taipei and Y-Ilan, E-Pin operates a jointventure with the Chinese government in Nanjing, China. In another factoryin Chu-hai, China, lenses are coated under cleanroom conditions. "Injectionmoulding of lenses is not the strength of E-Pin today. Others can alsodo that. But combining injection moulding with subsequent processes suchas printing of lenses, coating of lenses with silicon dioxide (SiO2), magnesiumfluoride (MgF2) and aluminum, and fabrication of components for the cameraindustry - that's our strength," says Shyu.

In-house Manufacturing Cells

Each month, the company processes 13 metric tons of PMMA, 6 metrictons of PC, about 2 metric tons of PC/PS blend, 2 metric tons of 10 percentglass-filled ABS, and a few other plastics from Asahi, Nisseki, Teijin,and GE Plastics. Sprues and runners are sold to other injection mouldingplants to be reground and blended. The extensive range of equipment formouldmaking, glass lens manufacturing, and plastic lens processing totals130 machines. Various coating lines, screen printing as well as pad printingmachines, and an ultrasonic cleaning system are especially important forthe plastic lenses.

All moulds are designed and built in-house. In one of the numerousproduction areas, which Shyu called typical, there are five injection mouldingmachines, two each from Fanuc with 30 and 50 tons of clamp force, respectively,and one from Arburg with 70 tons of clamp force. (Figure 4).

All together, E-Pin has 43 moulding machines from Arburg, Engel, Fanuc,and Sumitomo at the various production facilities, with clamp forces rangingfrom 30 to 150 tons. Six additional fully electric machines in the 200-to 300-ton range are to be added this year.

Mounted on each machine is a three-axis robot that removes parts fromthe mould and places them on a conveyor. At the end of the conveyor, partsare degated and presorted for assembly.

Initially, plastic lenses were moulded via injection-compression onfully hydraulic machines from Engel and Arburg. With the injection-compressiontechnique, plastic is injected into a partially closed mould. Compressionoccurs only as the mould closes completely. This pressureless filling ofthe mould eliminates moulded-in stresses in the lenses. "We establishedquickly, however, that on fully electric machines, optical lenses couldbe injection moulded conventionally without moulded-in stresses,"says Shyu. E-Pin regards several aspects of the Roboshot machines fromFanuc as especially beneficial when moulding precision parts:

Another advantage of the fully electric machines is that the variousmechanical machine functions occur in parallel. Thus, the ejector pinscan advance and break off the gate during mould opening.

Round-the-clock Reliability

Shyu explained that only three-shift production 24 hours a day makesnon-stop production, low production costs, and high process stability possible.

The latest QC equipment helps to achieve complete quality control, whichextends from incoming material through production to testing of finishedparts (Figure 5). E-Pin guarantees its customers a defect rate of lessthan .5 percent for finished parts and is currently working on ISO 9001certification.

To check refraction in the lenses and measure surface quality (roughness),E-Pin uses a total of six laser interferometers from Zygo, USA, and Olympus,Japan. A computer-aided spherometer (THRS, UK), a microscope (Nikon, Japan),and 3-D coordinate measuring machines determine the wavelength and geometryof the lenses. Four spectrophotometers (Shimasu and Hitachi, Japan) measurethe intensity distribution of photographic spectra. Assembled componentsundergo a complete test at the end of the inspection line. Parts are thenpacked, driven by trucks to the nearest harbour, and finally shipped.

Contact Information: E-Pin Optical Industry Co. Ltd.Mr. Shan-Woei Shyu 4 Fl., No. 16-2, Sec. 2 Chung-Yang S. Rd. Peitou, Taipei,Taiwan, R.O.C. Phone: (886) 2 894 8691 Fax: (886) 2 891 1107

Fanuc Ltd. Oshino-Mura Yamanashi Prefecture 401-05 Japan Phone: (81)555 84 5555 Fax: (81) 555 84 5512