ASSEMBLY PROCESS:CURRENT DEVELOPMENTS

CURRENT DEVELOPMENTS

Today’s competitive environment is characterized by intensified competition resulting from market saturation and increasing demands for a customer-oriented production. Technological innovations also have an influence on the competitive environment. These facts have dramatically altered the character of manufacturing. Meeting customers’ demands requires a high degree of flexibility, low-cost / low- volume manufacturing skills, and short delivery times. Production and thereby manufacturing per- formance thus have gained increasing significance and are conceived as a strategic weapon for achieving and maintaining competitiveness (Verter and Dincer 1992). Especially in high-tech markets, where product technology is rapidly evolving, manufacturing process innovation is becoming an increasingly critical capability for product innovation. To meet the requirements of today’s markets, new paths must be trodden both in organizational methods and in manufacturing and automation technology (Feldmann and Rottbauer 1999).

General Developments in Assembly

The great significance of assembly in a company’s success is due to its function- and quality- determining influence on the product at the end of the direct production chain (Figure 1). Rational- ization of assembly is still technologically impeded by high product variety and the various influences resulting from the manufacturing tolerances of the parts to be joined (To¨nshoff et al. 1992). As a result, considerable disturbance rates are leading to reduced availability of assembly systems and delays in assembly operations. This complicates efficient automation and leads to consideration of displacing assembly plants into lower-cost regions. Assembly is also influenced by innovative de- velopments in the manufacturing of parts, such as surface technology or connecting technology, which can have an important influence on assembly structures. The complex reflector assembly of a car headlight, for example, can be substituted for by surface coating technology.

Due to the rapidly changing market and production conditions, the role and the design of the individual functions within the entire value-adding chain are also changing. Other factors helping to bring this about include by the influence of microelectronics on product design and manufacturing structure and global communication possibilities. Facing the customer’s demands for the after-sales or service functions, for example, is becoming of increasingly important to a company’s success. More and more customers would like to purchase service along with the product contract.

The growing complexity of the manufacturing process in industry has its origin in the globalization of the markets, customer demands for systems instead of single products, and the introduction of new materials and technologies. Designing a product for ease of assembly using design for manu- facture and assembly (DFMA) methodology leads to a reduced number of variants and parts, higher quality, shorter time-to-market, lower inventory, and few suppliers and makes a significant contri- bution to the reduction of complexity in assembly (Boothroyd 1994).

The influence of the different branches and product structures is more evident in the range of assembly technology than in prefabrication. This also has a lasting impact on site selection because of the required workforce potential. Therefore, the global orientation of the assembly plants should be clarified on the basis of four major product areas (Figure 2).

Car assembly can be characterized as a serial assembly with trained workers. In contrast, the machine tool industry is characterized by a high degree of specializiation and small lot sizes, requiring highly skilled workers for assembly tasks. This makes the global distribution of assembly plants difficult, especially because the close interaction of development, manufacturing, and start-up still plays an important role. In contrast, the assembly of electronic components, inspired by the tech- nological transition to surface mount technology (SMT), has been rapidly automated in recent years. In view of the small remaining share of personnel work, labor costs do not have a major influence on site selection in this product area any longer. In contrast to car assembly, the electronics industry is characterized by a more global distribution of production sites and comparatively smaller produc- tion units. However, this simplifies the regional or global distribution of assembly plants. Product size as well as logistical costs for the global distribution of products from central assembly sites are generally lower than in the automotive industry. In the white goods industry, a relatively small ratio of product value to product size is decisive. Serving global markets under minimized logistical costs requires corresponding global positioning of distributed assembly plants.

In general, for all industries, four fundamental solutions in assembly design can be distinguished (Figure 3). Manual assembly in small batch sizes is at one end and automated serial assembly at the other. Thus, the introduction of flexible assembly systems is reinforced. Again, these flexible auto- mated assembly systems offer two alternatives. The integration of NC axes increases the flexibility of conventional machines, whereas the introduction of robot solutions is aimed at opening up further assembly tasks for efficient automation. There have been many technological responses to the global demand for large product variety coupled with short delivery times. In this context, the concept of human-integrated production systems is gaining ground. The intention here is to allow the human operator to be a vital participant in the future computer integrated manufacturing systems. This also has an impact on the design of assembly systems.

stronger concentration on higher functional density in subsystems (Figure 4). In car assembly, this means preassembling complex units like doors or cockpits; in electronics, this means circuit design with few but highly integrated circuits.

The new paradigm in manufacturing is a shift from Taylorism and standardization to small-lot, flexible production with emphasis on short lead-time and responsiveness to market. Organizational decentralization in autonomous business units, called fractals (Warnecke 1993), has also encouraged the distribution of assembly plants. The reduction of production complexity as a prerequisite for a faster, more flexible, and self-organizing adaptation of business units to changing market conditions is based on a redistribution of decision making responsibilities to the local or distributed unit.

The managing of complexity in manufacturing by outsourcing is rather common in the prefab- rication field, whereas the reduction of production depth and the resulting cost advantages contribute to keep assembly sites in the countries of origin. In turn, the formation of decentralized business units results in more favorable conditions for the relocation of specific assembly tasks to other regions.

Impact of Electronics on Assembly

Within the framework of assembly rationalization, electronics almost has a double effect (Figure 5). In the first step, efficient assembly solutions can be built up by electronically controlled systems with programmable controllers and sensors. In the second step, the assembly task can be completely replaced by an electronically provided function. Examples are the replacement of electromechanical fluorescent lamp starters by an electronic solution and, on a long-term basis, the replacement of technically complex letter-sorting installations by purely electronic communication via global com- puter networks. Not only does the replacing electromechanical solutions with electronic functional carriers reduce assembly expenditure, but electronics production can be automated more efficiently. In many cases, the functionality and thus the customer benefit can be increased by the transition to entirely electronic solutions.

The further development of semiconductor technology plays an important role in electronics production. In addition to the direct consequences for the assembly of electronic components, further miniaturization, increasing performance, and the expected decline in prices have serious effects on the assembly of electronic devices and the further development of classical engineering solutions. Within a certain range, the degree of automation in mechanical assembly can be increased only up to a certain level. In contrast, in electronics assembly, there is greater higher potential for increasing the degree of automation. This also has consequences for product design. Figure 6 shows a com- parison of the degree of automation in mechanical and electronics assembly.

Today’s paradigms for manufacturing require a holistic view of the value-adding chain. The disadvantages of breaking up the value-adding chain and distributing the single functions globally can be compensated for by models and tools supporting integrated process optimization. Examples of this are multimedia applications based on new developments in information technology and the

concept of virtual manufacturing, which is based on simulation technology. The diffusion of systems such as electronic data interchange (EDI) and integrated service digital network (ISDN) allows a more efficient communication and information exchange (Figure 7).

Distributed and decentralized manufacturing involves the problem of locally optimized and iso- lated applications as well as incompatibilities of process and system. To ensure synergy potentials and stabilize the productivity of the distributed assembly plants, an intensive communication and data

exchange within the network of business units is vital (Feldmann and Rottbauer 1999). New infor- mation technologies provide correct information and incentives required for the coordination of ef- ficient global production networks. For instance, the diffusion of systems such as EDI and ISDN allows more efficient communication and information exchange among the productive plants linked in the same network. Furthermore, high-efficiency systems such as satellite information systems have contributed to perform operations more efficiently with regard to the critical success factors. For instance, tracking and expediting international shipments by means of preclearance operations at customs leads to a reduction in the delivery time. The coordination of a network of transplants dispersed throughout the world provides operating flexibility that adds value to the firm. From that

point of view, a decisive improvement in the conditions for global production networks has come about through the influence of microelectronics with the new possibilities in telecommunications.

As data definitions become more sophisticated under emerging standards such as STEP, corporate server networks can distribute a growing wealth of product and process information among different parts of the organization and its associates. Processing programs developed worldwide can be used in all production sites by means of direct computer guidance (Figure 7). The diagnosis of assembly systems is coordinated from a central control center. In this way, it becomes possible to transmit the management of a project in the global production network around the clock.