Due to inflation, labor costs have been steadily increasing-particularly in the industrialized countries. These costs have not been matched, in many cases, by a corresponding increase in the productivity of labor. Accordingly, it has become increasingly difficult for companies in high labor cost areas to compete efficiently in world markets.
In an effort to remain competitive, various labor-saving devices have been adopted by companies whose labor costs are high. As an example, computers are now widely used to carry out a whole variety of operations which were, at one time, done manually. Through the use of computer technology, the industrialized nations have managed to remain competitive in spite of the rapidly escalating cost of labor.
In the design of a new product, it is generally necessary to first prepare a working drawing of the proposed product. In making a working drawing, it is frequently very desirable to make the drawing to a very accurate scale since the drawing may then be used in determining the desired tolerances for the various components.
In many cases, an overall design may require the efforts of a large number of designers in which one group may design one component while other groups design other components of the complete structure. Finally, when the efforts of all of the groups have been completed, the separate designs are put together to produce a master drawing in the form of a complete assembly or, in the case of a manufacturing facility, in the form of a complete layout.
Not surprisingly, when the work efforts of a large number of people are assembled in the form of a master drawing, the master drawing may reveal errors in the individual designs as, for example, when the parts of a complex machine do not properly fit together. Also, in a plant layout or building design, a master drawing may indicate that the individual designs are conflicting. Thus, the master layout may indicate that an air-conditioning duct may pass through a beam or that lubricant lines for a given piece of machinery may pass through a space reserved for process piping.
For the reasons indicated, it is frequently necessary that drawings be made with great accuracy. To do this manually may be both time consuming and expensive. Accordingly, drafting machines have been developed in which the output from a computer may be used to move tools in a very accurate manner relative to a working surface such that the drawing is prepared automatically.
Previous drafting machines have had certain drawbacks, particularly when the movement of the tools relative to the working surface was relatively rapid. In this instance, the tools were frequently not positioned relative to the working surface with the desired degree of accuracy. When the speed of movement of the tools relative to the working surface is increased, the tools may have a tendency to move away from the working surface and the accuracy of the resulting drawing is, thereby, impaired.
Accordingly, it would be desirable if a machine could be devised for more accurately preparing drawings since this would reduce the cost of the drawings. Further, it would be desirable to provide a machine in which the forces applied by the tools against the working surface could be varied in proportion to the speed of movement of the tools relative to the surface. This would then provide a means for overcoming the tendency of tools to move away from the working surface as the speed of movement of the tools is increased.
Additionally, it would be desirable to provide improved tools, particularly an ink-supplied pen of greater simplicity and accuracy. Desirably, such a pen would be able to ride over minor irregularities in the working surface without damage to the pen point. Also, it would be desirable to control the ink flow from the pen onto a working surface in proportion to the speed of movement of the pen relative to the surface. This would provide an increased ink flow rate onto the working surface when the pen was moved at higher speeds with respect to the working surface. However, at the same time, with the pen at rest or being moved slowly with respect to the working surface, the ink flow rate would be reduced so as to not drip ink onto the working surface.
The above need for great accuracy and speed in the making of drawings is particularly acute in the making of drawings on a plastic surface. For example, drawings may be made on a sheet of Mylar having a thin ruby coating thereon of approximately one mil in thickness. By either scribing lines on the ruby coated surface or by cutting the ruby coated surface to remove portions of the coating, the resulting drawing may exhibit great contrasts in color. Where the ruby coating remains intact, the surface coloration will be a reddish color. However, where the ruby coating has been removed, the Mylar will appear transparent. Thus, the drawing exhibits the contrast that is provided by having transparent lines or areas viewed against a reddish background.
In cutting a ruby coating to make a drawing on Mylar, great accuracy is required since it is essential that the cut lines in the ruby coating meet very precisely. Also, it is necessary that the cut lines or scribing lines only penetrate through the ruby coating while not marring the underlying sheet of Mylar. Also, the resistance of the ruby coating to cutting will vary in proportion to the speed of the blade with respect to the coating. This variation will have a tendency to move the cutting tool away from the working surface as the speed of movement of the cutting tool is increased relative to the surface. If the cutting tool is moved sufficiently away from the working surface, the tool will not perform its intended function in an accurate manner and the resulting drawing will be flawed.