Transfer Lines for Modular Components / 1981
Engine Parts Called 'Modules'
Engine parts such as cylinder heads and crankcases are often referred to as 'modules.' As simplistic as the term might sound, the production of these modules implies a great degree of model-specific investment for the necessary dies, jigs, and mechanical equipment. Moreover, there is a considerable span of time, once product development has begun, until actual production is launched, during which the manufacturer is subject to losses stemming from unforeseen problems. In this way, the production of modular parts is similar to that of body assemblies.
The module machine unit at work. The ganged head is set on the rail in the center.
Since its establishment Honda has endeavored to implement the optimal production systems for all these parts. In keeping with the company's desire to meet the changing needs of an increasingly advanced society, sophisticated processing technologies, line systems, and mechanical devices have helped make that possible.
Through years of accumulated expertise, Honda has directed considerable effort to the improvement of production lines for modular engine components. Some of these efforts have promoted process integration and streamlined the production cycle, using equipment to perform several procedures simultaneously on multiple axes. Others were intended to reduce less safe and repetitive tasks by automating the installation, removal, and transport of workpieces. As a result, Honda has built some of the world's most efficient mass-production systems, earning a reputation for high quality with single, mass-production models.
These production lines were, dedicated lines, however, each planned and installed for a specific model. Therefore, for the first several years, each new model launch required, new machinery or modifications to existing lines. Moreover, those lines could not be used to produce other models, even if given a drop should occur in the production volume of a target model. Eventually this would lead to diminished efficiency on the line, resulting in a cost increase.
In an effort to enhance its capability to produce multiple models, Honda also examined a combination line system consisting of core machines that were dedicated to common machining steps and NC (Numerical Control) machines which were designed for processing different parts of various models. However, parts-handling capabilities for such a system were limited to pieces with a certain degree of similarity. Since modular engine components usually require between ten and forty steps per machining surface, the handling of these various machining steps individually-or, axis by axis-was in conflict with company production principles.
Modular Components: A New Concept in Processing
The first worldwide oil crisis in October 1973 pressured industries in all sectors of commerce to become more energy-conscious.
However, consumers were at the time becoming more selective, and their increasingly diverse needs meant that manufacturers had to develop more products offering different features. Nowhere was this more evident than in the motorcycle market.
The untimely change in consumer buying habits came as something of a surprise to Honda, which in producing various types of engines for use in its motorcycles, automobiles and power products had to ensure the viability of its marketing on a worldwide basis. In particular, the company sensed the need for a new system that could produce the modular components needed for its motorcycle engines, yet accommodate a rapid response to the market's call for model diversity.
Such a new system would have to achieve greater productivity in the processing of engine parts for several different models. Moreover, it would have to achieve that with less of an investment and a shorter downtime for adjustment when a new model was launched.
The DE (Development Engineering) Division of Honda Manufacturing Machinery initiated a new research project in February 1974 aimed at creating a processing machine for such parts. Called the 'module center,' it would provide the much-needed increase in flexibility for use in multiple model lines. It began with a two-man shop, with Takao Shirokawa, an engineer experienced in designing combined-layout machines, and Shougo Kurihara, who was then in charge of engineering at DE.
It was an urgent assignment for Shirokawa and Kurihara. Since they had believed that consumers would demand a greater variety of small motorcycles - meaning shorter model cycles. Thus, the existing production facilities, with dedicated machines, would soon fail to cope with demand. Focusing on the production of multiple varieties in relatively small volumes, they looked at various ideas regarding the concept for a prototype machine. They wanted a processing system that could handle numerous processing conditions with greater adaptability and reliability.
The structure permits easy change-out of ganged heads, facilitating multiple-variety/small-volume production.
Their design concept employed a simple, NC mechanism featuring a variable-speed DC motor to drive the main processing axis. This would allow the operator to change cutting and feed patterns more flexibly than before. In addition, they modified the dedicated processing section used with specific models, in order to reduce startup costs and depreciation. For example, a ganged head was designed with a 25-mm cast-iron jig plate, allowing the attachment of multiple blades. A blade-rotation mechanism using the engine's timing belt was incorporated into the head structure in such a way that each head, which comprised a main-axis drive part and a rotational drive mechanism, could be connected to or disconnected from the main unit with just a one-touch operation. Due consideration was given to maintenance, allowing ganged heads to be changed manually or via a rotary index mechanism. The basic specifications of the machine-itself a major departure from the conventional concept-were intended to integrate the advantages of NC and multiple-axis processing.
The module center project was moved to EG in July 1974 for continued evaluation. Previous evaluations in the research stage had anticipated that the machine would not provide sufficient reliability or cost-effectiveness in daily production. This was an understandable concern, given the fact that in those days both the drive belts adopted by the module center and NC motor for use in controlling blade rotation and feed were still in the earliest stages of development, even among specialized manufacturers.
According to Jinsei Ida, then an engineer with the First Design Block, "I think Mr. Oishi (Katsura Oishi, then managing director of EG) had hoped it would become something of a press machine, since the relationship between dedicated processing modules and the machine center was similar to that between dies and a press machine." Ida, in fact, was later appointed LPL (Large Project Leader) for the second-phase development aimed at mass-production applications for the machine. A press machine offers a significant degree of flexibility, because different specifications can be handled by replacing the dies rather than changing the machine. In a similar way, the module center was intended to facilitate processing for different specifications simply by changing its ganged heads. The concept of enabling flexible combinations via ganged heads suggested there was the potential for dramatic changes in the conventional production line system.
A Machine with Dedicated Processing Modules
The year, 1975, got into full swing amid increased competition in the motorcycle market, and EG was under considerable pressure to complete the module center quickly, in order to facilitate its integration with the line.
An evaluative meeting was held at EG in November 1975, where it was decided that the direction of the module center's development would be altered.
Essentially, the machine's objective and application would change from multiple-variety, small-volume production to multiple-variety, large-volume production. Accordingly, it was to be determined as soon as possible whether the machine was feasible; whether or not it could replace the current motor technology, gear-train technology, and various other means applied to dedicated systems. Based on the directional shift, the theme of research was changed to 'module machine.'
The organization of a project group was also stepped up, thus introducing a new theme. Joining the team effort were Ida, who was designing mass-production machines for engine/transmission parts, and Mitsuo Suzuki, an engineer with the First Engineering Block who had been planning machining lines for engine parts. Assuming the actual mass-production settings, they worked to identify specific target requirements, among which were the achievement of a cycle time and reliability equal to those of the lines using dedicated machines. Still, it had to be accomplished with maximum cost-effectiveness and flexibility in order to make the module machine a reality.
The newly expanded team, seeking the assurance of reliability, changed the blade-drive mechanism from belts to gears, adopting a pulse motor for the feeding of blades. Furthermore, they decided to automate the ganged head change process and design a structure having loop-shaped rails around the drive portion. Four ganged heads were set on loops, meaning that any specific head could be easily connected to the drive portion and perform the desired process.
A special meeting for evaluation was held in mid-December, at which the team exhibited its prototype module machine and described the anticipated benefits of the final version. They also addressed the possibility of dramatic enhancements to the machining line with the introduction of this new machine. Thus, their presentation marked the end of the research phase and the start of a new phase in the development of Honda's module machine.
Phase two kicked in at EG immediately following that meeting. Ida was appointed LPL for the project, the purpose of which was now to apply the machine to mass production.
Just Like a Press Machine
February 1976 saw the market introduction of Honda's new 50-cc family bike, the Road Pal. It was an immediate hit, creating a boom in family bikes, thanks in large part to the hugely successful TV commercial featuring Italian actress Sophia Loren and the fad phrase, "La-tta-tta." Following the Road Pal's success, the company adopted a strategy of introducing a whole series of new models, hoping the move would solidify Honda's position in the motorcycle market. First, however, a flexible system of production had to be established, and it had to be soon.
The development team was at the time busy designing a new gear train under Ida's supervision. The effort began as a tedious, manual process of drawing circles on the blade layout using a compass. Work efficiency was soon improved, however, with the development of original design software for gear trains, allowing the team to proceed to its next target. The changeover speed for ganged heads - which now weighed 500 kg, due to the gear train - was to be brought up to that of the machining center.
It normally took around four seconds to change blades on a conventional machine. However, the engineers, each of whom was highly experienced in machining, believed it would not be possible to achieve that speed with the new machine while maintaining the required precision. It was common knowledge that processing machines could only perform operations at high levels of precision when there was a secure connection between the ganged head and drive portion and the head's weight was fully supported by rigid construction. No company - not even a manufacturer of general machining tools - had ever conceived of a machine capable of changing such heavy ganged heads in a matter of a few seconds.
Recalling that period of Honda's history, Ida said "The objective of a general machine-tool manufacturer is to compete with rival manufacturers and maintain its market lead. However, that was not the case with us. For us it was more important to develop the optimal manufacturing facility at Honda, thereby ensuring that production would start on schedule for each of the new model series the company was to release. In other words, our target was to maintain a lead over rival manufacturers in manufacturing Honda products."
The module machine had initially adopted a pulse motor for the control of blade rotation and feed - the core function of the machine - in order to ensure reliability, cost-effectiveness, and a stable driving force. However, further study found that this type of motor was incapable of sufficient control reliability. Accordingly, the development team changed the drive mechanism to a hydraulic cylinder system. This was only two months before the start of the mass-production-monitoring program scheduled to take place at Hamamatsu Factory. Concurrently, they adopted a semiconductor sequencer system that would allow the machine to control blade rotation and feed during processing, according to a predetermined sequence. The development team, in its rapid implementation of these features, was able to complete its first module machine. Moreover, their system had the ability to change ganged heads in just 2.8 seconds!
"When he saw the machine," Ida recalled, "Mr. Oishi told us, 'Well done. You have created something just like a press machine with an automatic die-change function.'"
The mass-production-monitoring program for the module machine got under way at Hamamatsu in July 1976. The reason for the program was that in actual mass-production problems not previously identified could sometimes occur. Such monitoring programs provide an invaluable opportunity to enhance machine development, reflecting the input of people who actually use the machines.
The module machine actually did encounter a problem during the mass-production run. Fluctuations in feed speed were experienced during processing, as a result of increased operating temperatures in the hydraulic cylinders. That diagnosis meant the line staff had to rewrite and adjust the relay switches while checking the rotation and feed action of the blades currently processing the workpiece. The interruption threw the mass-production line into complete chaos. Since the new machine employed different wiring, both the maintenance staff at the factory and EG's electrical engineers worked frantically to restore the line. It was dirty, uncomfortable work, and it was not long before their bodies were covered head to toe in oil.
Monitoring periods like these were part of the overall process, though. Tiresome as it was, the line test and subsequent adjustments had finally brought the new machine to completion.
Birth of the Module Transfer Line
Popularity of motorcycles began to take off in 1978 even among middle-aged men, increasing the size of the overall market. In fact, a full-scale motorcycle boom was underway, including larger models as well as the family-bike segment.
In February 1978, Honda installed a machining line incorporating the new module machines at Saitama Factory's Wako Plant, with the objective of processing engine heads and casings for its larger motorcycles. Then, in February and August 1979, module machines were introduced as independent units at the Kumamoto and Hamamatsu factories, respectively.
EG was then engaged in an effort to reduce the investment required for ganged heads. In order to reduce their cost for use in the new mass-production machine, various methods were examined from every perspective, including the possibility of changing the entire approach to production. Consequently, several cost-reduction measures were implemented, including the adoption of modular designs for various standard parts, new processing methods, and more effective subcontracting and purchasing with regard to parts.
The 50 cc Tact scooter made its market debut in September 1980. It was then that the scooter market, which had been largely dominated by import models, became a battleground for domestic manufacturers. In short, a boom in scooters had been triggered by the stylish little Honda.
The development team at EG was at the time busy with a project to enhance the operating efficiency of the module machine. Their goal was to make it a comprehensive processing station by designing a new jig base on which to set the workpiece. Additionally, they were developing a device that could change the ganged heads automatically.
In fact, their innovative jig-base concept not only allowed the workpiece to be installed or removed amid processing, but also provided a 180-degree rotating mechanism that would allow the work to be processed on both sides. Thus, the module machine became a full-fledged production facility with setting adjustments capable of handling production volumes ranging between 10,000 and 40,000 units per month, per model.
The automatic ganged-head changeover device was designed for enhanced efficiency in mixed production. Located directly above the base machine, the space-saving system could change the upper and/or lower ganged heads using a lift mechanism. Further, it allowed automatic head changes among eight units, even in the middle of a cycle. The use of an additional transfer device made it possible to replace the ganged heads with units stored outside the machine itself.
The module machine's productivity and flexibility were further improved with the installation of a high-speed palette transfer device on the jig base. With that, the module transfer system was complete. In comparison with conventional transfer machines designed for high-volume production, Honda's new system was far more flexible in production. In fact, it accommodated processing for up to four different models on each machine.
The loop-type module transfer machine.
The Tact scooter was succeeded by the Karen in February 1981, concurrent with the U.S. market debut of several larger models from Japanese manufacturers.
Then, in November of that year, EG began operating its new module transfer line for engine heads and casings at Hamamatsu Factory, with the goal of increasing the production of Honda's larger, U.S.-bound models in time for the Christmas season. Eight new lines went into operation during the following year despite the fact that Honda, from 1979 to 1983, was busy battling Yamaha for market dominance. The module transfer lines, however, did more than answer an urgent call for multiple models in order to fight back the competition. They continued to drive the company after that period, bringing new flexibility to automobile production.
The new module transfer lines changed Honda's entire production approach, allowing it to process motorcycle engines for multiple models - each of which was based on a completely different design - with the same efficiency afforded by advanced lines of automation. No longer was it necessary to install a new line each time a new model was launched. The factory was now able to examine the available capacity of existing lines and adjust its lines to accommodate a new model. Accordingly, these new lines could alternate in the production of new models, thus optimizing the balance of processing throughout the plant.
It had also become possible to configure a specific line suitable to the characteristics of target parts, such as the engine block and cylinder head, by combining the desired components with the module machine's main units. Since the components comprising the line were standardized, the main units could be ordered to begin constructing the line before detailed specifications were determined for the new model. Design and production of the model-specific portions of the machines, such as the ganged heads and jig bases, could start after the final drawings were issued by the R&D Center, with ample time left for any necessary adjustments. Accordingly, when introducing a new model to an existing line at the factory, a trial line could be set up at the EG facility in order to verify its manufacturing feasibility. This could be done while development was still in the mass-production prototype stage, using the completed ganged-heads and jig bases. The entire process minimized the facility investment and startup costs associated with new models, facilitating smooth mass production and reduced lead times. These advantages represented significant benefits for the preproduction process.
It was also possible for the factory to configure a transfer line according to the specified volume of production, by using a quarter-line (suitable to 10,000 units per month), a half-line (20,000 units per month), or full line (40,000 units per month). The full line, for example, would accommodate the mixed production of four different products, while a half-line could handle two products. Moreover, each of these lines could easily handle various production volumes within its specification range. This made it possible to maintain a high rate of operation for each line.
The module transfer line brought forth new possibilities in mass production, shifting the focus to flexible use of lines. It was a breakthrough duly recognized by the Japan Society for Precision Engineering, which in October 1983 honored the development team with its Precision Machinery Award.
Honda's new module machines, which had originally been created as a means of facilitating multiple-model parts production for motorcycles, had thus evolved to encompass the modular engine parts used in automobiles. When the module machine was first developed, no one had imagined that so many different types of automobile engines would be available.
Thus, over the years, the design of module transfer lines has undergone continuous enhancements as part of an effort by both motorcycle and automobile production factories to achieve more stable operations. It was through this diligence that the design became the complete system it is today.