FACTORY AUTOMATION

Production automation is fundamental to Japan's competitiveness in terms of the cost and quality of its consumer electronic products. In addition, a growing labor shortage, demands for improved working environments, and company-wide computer-integrated manufacturing have made automation a necessity for many companies. Since most fabrication activities have already been automated, the current focus of attention is on the automation of assembly lines, where labor content has been highest.

There are several stages of assembly line automation, with varying impacts on flexibility and product design. The move from hand assembly to robot assembly of existing products can be termed "first-generation" automation. "Second-generation" lines require some product design changes for assembly line automation. Automation that requires broad product design changes is termed "third-generation" automation.

The JTEC panel observed widespread automation during its plant tours. The leading Japanese electronic companies have implemented the following FA concepts (Kahaner 1993, 33-56):

Key benefits cited for the use of automation include reducing factory set-up time, manufacturing defects, product lead time, and direct labor, and increasing the ability to rapidly deploy manufacturing operations around the world.

Sony management described the following as an example of the benefits gained from the company's factory automation activities: It took three to four months to start up Sony's original production lines in Japan, but it required only two to three weeks to bring replicated lines up to speed in Singapore and France. Changing models required only 9.1% of additional capital investment in Sony's first changeover, 3.5% in the second changeover, and only 1.5% in the third changeover. In addition, the move to automation resulted in improved quality. The best defect rate using manual labor was 2000 parts per million (PPM), compared to 20 PPM after the first week of automation. Sony's personnel policy was to remove employees from manual labor jobs through automation so that "they could become more creative in solving problems and improving operations." Due to Sony's strong knowledge base in automation and its focus on design for manufacturability, between 1987 and 1990 it increased sales by 121% with an increase of only 35 employees.

Automation for Miniaturization

Japanese electronics companies have made and continue to make large investments in production technologies and factory automation because of their commitment to miniaturization as well as to high product reliability and low product cost. As electronic components shrink to as small as 1.0 mm by 0.5 mm (called "1005" parts), and as component lead pitch approaches 0.2 mm, human assembly is no longer feasible.

The Japanese strategy to develop key components for use in electronic products has also required investments in equipment development. "Off-the-shelf" equipment is generally inadequate to meet the manufacturing needs of new component technologies. Without exception, each Japanese company the JTEC panel visited was designing and building critical equipment in-house. According to these companies, equipment provides a major competitive advantage because it is designed to respond to the specific manufacturing requirements of the companies' components or products.

The JTEC panel was impressed by the fact that some Japanese component suppliers also supplied buyers with the equipment required to assemble their advanced components. TDK, Murata, and Matsushita, for example, developed internally the production technology to make 1005 parts, and they also supplied the assembly equipment required for customers to utilize these ultrasmall parts in SMD assembly. The equipment makers introduced the equipment at the same time as the new miniature parts were made available to the market. The production technology is being developed to ensure that new components are rapidly included in next-generation product designs.

Miniaturization is forcing assembly technologies to become faster and more precise. Precision robots have improved repeatability from .05 to .01 mm over the past decade. Matsushita's latest SMT placement machine incorporates 11 placement heads with .01 mm placement repeatability. Sony's high-speed robots now work at .012 mm repeatability. These levels of precision are beyond human capabilities. As Figure 5.7 shows, Japanese electronics firms use miniaturization technologies to a much greater degree than U.S. firms.


Figure 5.7. Predominant pitch capability for low-cost
electronic packaging (MCC Portable Electronics Packaging Project).

Final Assembly Design Techniques

In assembly operations, parts handling and feeding and line control are very complex; however, with the advances made in equipment, production control, and computers over the past decade, automated assembly lines are no longer unusual. Until now, such automation has been focused on high-volume, low-cost production operations like the manufacture of consumer electronics products or other products with relatively simple design structures.

Recent advances in production technology include robots and sensors, component feeding, line control, and production management techniques. There are three critical advances (Kahaner 1993, 34):

Positioning is the most common problem for assembly automation. Different sizes and shapes of components make assembly difficult. Precision positioning of parts for printed circuit boards in consumer electronic products is especially challenging. If the board is out of position, the problem is compounded. This is a problem with board warpage where accurate sensor detection is especially difficult. NEC in Gunma Prefecture developed a triangular measuring optical sensor that is used in a procedure to detect the height of three points on a printboard. A two-dimensional curving warp can be represented by three points, so the company had to come up with innovations in measurement point selection and interpolation techniques.

Jigs are fundamental to positioning parts properly before assembly. Complex part shapes can make such positioning difficult. Visual sensors can detect the positions of parts and also allow for mixed-flow production operations. These sensors can also detect parts' shapes and therefore are useful in product quality control applications. Toshiba's most recent application of CCD technology to visual sensors has allowed for 0.02 mm positioning accuracy. More typical sensors, combined with the mechanical error of a robot, result in errors of several hundred microns.

Flexible lines are required to cope with the demands of multiple-model, mixed-flow production. Movable jigs and visual sensors are used to adjust to changing parts shapes. In mixed-flow assembly lines, product model information must be controlled to match parts with the models on the line. Some companies have used memory cards on parts pallets to achieve this control. Integration of such parts flows with mixed-line assembly is based on sophisticated parts-feeding equipment, which may account for 80% of the automation success.

Modular product designs are used to reduce equipment costs and to improve product reliability. It is essential to implement design features that are compatible with automated assembly operations. It is then possible to simplify assembly and enhance operational reliability by orienting all the assembly steps in one direction or employing connection techniques amenable to automation. For complex assembly operations that could be handled by robots, Fujitsu developed special supplemental mechanisms that required changes in such details as screw shape.

Product structures are divided into a number of modules for design purposes. Each module is assembled on a subline, and the assembly operations not amenable to automation are concentrated in the final assembly line. It is easy to achieve higher automation rates in the total assembly process because each module is designed to be compatible with automated assembly. In the personal computer, for example, every component used in final assembly simply slides into a slot or connector without difficulty. At NEC's PC assembly factory, each module is designed to be compatible with automation of the total assembly process.

Now that robots have become highly functional, Seiko Epson has designed its printers for the lowest total manufacturing cost and then constructed its assembly line accordingly. It has set about improving the automation rate while developing ways to handle multiple-module, mixed-flow production. The mixed-flow production approach helps hold down equipment costs and allows for flexibility in adjusting to demand fluctuations. Development of designs compatible with assembly automation is a new key concept that has great potential.


Published: February 1995; WTEC Hyper-Librarian