Research Paper on "History of CNC Computer Numerical Control"

Research Paper 18 pages (5340 words) Sources: 20 Style: Harvard

[EXCERPT] . . . .

History of CNC (Computer Numerical Control)

CNC Machines and How They Work

Computer-Aided Design

Future of CNC Machines

Spider-like CNC Machine

Laser Technology-based Micromachining

SSD technologies

Robotics Applications

This research paper will trace the history of Computer Controlled Machines from their inception to current sophistication levels. We shall also delve into their usage and benefits in various industries. The paper heavily references industry specific research from relevant eras to chronicle the evolution of CNC uses.

Rapid increases in the power of semiconductors and reductions in their costs made it possible to produce small, very powerful, relatively cheap minicomputers that could be used to control machine tools. The resulting computer-controlled machine tools (CNC) with a computer built into the machine tool allow for programming and editing by operators. In contrast, the hard-wired NC machine tools they replaced required programmers to produce and edit programs in offices away from the shop floor.

CNC Machines and How They Work

The mechanical part of the CNC machine has to be firm and sturdy to hold up to the quickly moving components. The spindle is typically the toughest part and is supported by huge bearings. Whether the spindle carries out the work or the tool, a mechanical clamping attribute allows the spindle to quickly clamp and unclamp throughout the program operation.

Found at the side of the machine is a magazine of diverse tools. A transport arm, on occasion called the tool bar, takes a tool from the machine, sets it into the magazine, chooses another tool from the magazine, and transfers it to the machine fed by instructions in the code. Usual cycle time necessary for this process is two to eight seconds. Several machines may hold up to 400 tools in large "hives," each routinely laden in series as the program functions.

The bed or worktable of the machine is held up on toughened steel "ways" which are more often than not protected by supple guards (Hatsopoulos, 2005). Cast iron or Meehanite utilized to be the element of choice for metal working equipment. In present day, the majority machines make widespread use of weldments of hot-rolled steel and shaped items such as stainless steel to decrease price and let production of other complex frame blueprints.

A few machines are planned as cells, due to which, they have a precise cluster of parts they are intended to produce. Cell machines are made of huge tool magazines to bear sufficient tools to do an assortment of operations on every one of the diverse parts, big worktables or the capability to modify worktables, and particular provisions in the regulator for coding and data inputs and commands from extra CNC machines. This permits the CNC machine to be constructed with other equally equipped machinery into a Flexible Machining Cell, which can create more than one part concurrently. A collection of cells, some comprising of 20 or 30 machines, is known as a Flexible Machining System. These arrangements of CNC's can manufacture accurately hundreds of diverse parts in unison with slight human intervention. A number of them are intended to run day and night with no supervision in what is known as "lights out" mechanization (Hatsopoulos, 2005).

While Wilkinson had considered one case study on CNC an Anglo-German research team concentrated on studying the implications of this new technology for organization and manpower, and tried to assess whether it was leading to de-skilling (see Hartmann et al., 1984). Their hypothesis was that the work traditions in different societies would not be changed as a consequence of technological change, but would be expressed in new ways, particularly as far as skills were concerned (Flowers, 2006). This hypothesis was verified by their study which found that CNC technology was extremely "malleable" and that there was no single simple effect of the use of CNC as such.

Like Bell in relation to hard-wired NC, they found that CNC had different effects according to such technical and economic factors as batch size, cutting technology, and machine type. For example, the allocation of programming tasks is strongly influenced by the time needed to write a program. In general, the longer it takes to write a program, the less likely are programming functions to take place on the shop floor, because the program can only be made when the machine is idle. But this is not invariably the case, as some machines permit the operator to program the next job, and sometimes operators draft programs after working hours. In turning especially, the author noted an increasing tendency for operators to program and perform programming-related functions such as speed and feed modification of previously prepared programs.

For such reasons, they concluded that the decision as to whether to allocate programming functions to shop floor personnel or to technicians working in a separate office cannot be determined easily in accordance with clearly defined technical and economic criteria. There is considerable scope for societal factors to intervene. Indeed, the study found that there was a consistently greater use of operator programming in Germany, while separation of programming and operation was more usual in Britain. These general patterns exhibited stability over time and considerable continuity between NC and CNC policies.

The researchers related the patterns to the differentiation between craft and technician trainees in Britain, in contrast to German practices in which technician status is acquired by a further stage of training of workers who had previously received craft-training. In Britain, those performing planning and programming functions are granted white-collar status. In Germany, those functions are frequently carried out by blue-collar workers. The absence of a status barrier between programming and machine operation makes it possible to rotate German workers between craft and technical functions without any fear of losing status. In Germany, formal qualifications are common in both small and large firms, while in Britain there are very few formally qualified workers in small plants.

The researchers noted several tendencies common to both countries, especially trends to greater component variety and smaller batch size. As a consequence, CNC operators were likely to have to deal with a wider range of jobs and more frequent changes. This brought with it the need for greater skills relating to tooling, materials, feeds, speeds, faults, and breakdowns, which, in turn, required greater craft shop floor skills rather than less. According to the author, companies, particularly in Germany, were increasingly seeing the merits of craft skills. While the data were only indicative, it appeared that the German pattern of use of more skilled labor was more efficient and that there was a trend in this direction in both countries (Hatsopoulos, 2005). As Stratasys, (2001) suggests in relation to British machine shops, "there are clear examples of where the new technology has been used to de-skill workers in machine shops rather than re-skill them, although the commercial wisdom of such a policy is being increasingly questioned."

Chapter Two - Methodology

As automated equipment such as CNC machine tools comes into more widespread use, there is an increasing need for proper maintenance to ensure that the equipment fulfills its potential for economic production of high-quality goods. Kaplinsky (1984, p. 137) suggested that the maintenance of high-technology automated equipment had been de-skilled through the use of printed circuit board replacement procedures. If an automatic diagnostic system can signal the location of the faulty board, the maintenance task can be reduced to simply replacing the faulty board with a new one and either discarding the faulty board or sending it to a specialized department for analysis and repair.

Fig. 1.1

Research in both the United Kingdom (Senker et al., 1981; Cross, 1984) and the United States (Small, 2003) casts doubt on this de-skilling scenario. Certain maintenance tasks-in particular, the replacement of printed circuit boards -- do, indeed, require little skill. But the maintenance of high-technology manufacturing systems more typically requires the ability to diagnose faults efficiently and rapidly that are not so simply identified. Specifically, defects are often concealed within hydraulic or mechanical subsystems. Repair and maintenance people working with automated equipment require less intimate knowledge of a single process or task, but they need a general knowledge of more tasks (Lester, 2008).

Computer-Aided Design

In Britain until the 1940s, the aspiring apprentice tried to get into the drawing office because it offered the terms and conditions of white-collar employment with good chances of promotion. Many "draftsmen" (male drafters) without University degrees gained access to professional and managerial careers by achieving technical qualifications through part-time study. Traditionally, in Britain, drafters completing their apprenticeships started work as detail drafters, progressed to more complex drawing work, and finally to design work.

By the 1960s, however, drawing office employment had become less attractive for two principal reasons. First, improved conditions of service on the shop floor and lower pay differentials offered craft workers benefits comparable to those of drafters. Second and more important, easier access to higher education increased competition for the professional and management jobs to which drafters had previously aspired. University-educated engineers bypassed the drawing office and… READ MORE

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