January 2010 Archives

In our tutorial #1, we've explained the mechanical LCA that corresponded to Ford-ism as "the age of fixtures". Since the technology advancement occurs on a continuous curve, it would not be appropriate to digitally divide and categorize, but for the sake of making the explanations simpler we've called the third generation manufacturing system as The Mechatronics Age, the age of Toyota style manufacturing system.

Subsequent to the advent of the Toyota manufacturing system age, the most significant difference between today and before is proliferation and utilization of computers.

Third generation LCA

In this third generation, the physically fixed motion control functions of cams/linkages are split apart into "Information" (time and position data) and "Motive power" control. With this, the "hard information" of the cams/linkages are replaced with "soft information" on computer software, and the motive power with servo motor controls, giving the new "Information Cam" scheme greater flexibility needed for a new trend in manufacturing of "Small lot/wide variety". In this period, the control scheme and equipment have rapidly advanced from [see Fig.1] relay logic sequence control >> PLC control >> PC control, requiring drastically increased participation of electric/electronic engineers.

Fourth generation LCA

Most of the fundamental componentry of LCA have emerged during the era of the third generation. Fine degree of high speed motion control was possible as long as the work piece and related tools remained unchanged. However, the era of post third generation would require the manufacturing system to adopt to decreased product life cycles and globalization. When the product life cycle becomes shorter, the used component quality tend to become more variable, and the manufacturers are required to perform the assembly work with components of varying quality. The countermeasures invented for this was to adopt experts' thought processes into computer algorithms (advancement currently continuing).

In this "Computer algorithm" generation, sensing technology and detected data processing would become important.
Furthermore, manufacturing systems with more flexibility, speediness, and lower cost of depreciation, the cell-manufacturing and one-person-manufacturing schemes where simple hardware is optimally combined with a human operator (human ingenuity) were devised and continuing to be evaluated.

LCA second generation

An LCA element "Mechanical cam/link mechanism" appeared as schemes to repeatedly produce mass quantities of goods (Ford-ism) developed.
This was an advancement from the first generation LCA elements of rotary to linear motion conversion to use as labor, and the advancement was based on the human dexterity rules replaced with cams and linkages to achieve two and three dimensional motion control.

The cam mechanism was already in existence in Leonardo da Vinci's sketch (see Fig.1). Thereafter, it was used for a variety of decorative wood working tools, then the scheme's high speed and reliability performance were further pursued for textile machinery and internal combustion engines in 1900s. Later, with the advent and advancements of NC machine tools, manufacturing of cams and linkages that are capable of complicated motion control tasks became possible, and became an important element of mass production assembly machinery.

The mechanical cam/linkage mechanism is an important element of the LCA concept due to its advantages such as stable and fast work handling capabilities for pick and place machines and indexing tables, and even for the most advanced surface mount machines for electronic components.

Advantages of the mechanical cam/linkage mechanism

	1.	Deceleration shock can be minimized by a cam curve thus high speed operation is possible.
	2.	Multiple motion tasks can be controlled simultaneously thus the machine cycle time can be shortened.
	3.	Machine size and low parts count result in good system stability and maintainability.

Examples of "Mechanical cam/linkage mechanism"