History of computer numerical control

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 entered the engineering hierarchy as junior professionals, while drafters languished in the drawing office (Flowers, 2006).

Michael Cooley (1972) has suggested that the drawing office has been downgraded in importance as a result of the finer division of labor in engineering that began in the 1930s. He described how the creative design element had become increasingly separated from the work of executing drawings. The fragmentation of shop floor jobs was, according to Cooley, paralleled by fragmentation of the job of the designer/drafter. Until the 1930s, drafters in Britain were responsible for designing a component, stress testing it, selecting materials for it, writing the specifications, and liaising with the shop floor and customers. But starting in the 1930s, these functions were progressively broken down into separate jobs and taken over by various specialists, such as stress testers, metallurgists, tribologists, methods and planning engineers, and customer liaison engineers, leaving drafters with only the job of drawing (3D Systems Corporation, 2001).

In effect, in the Britain of the 1930s, drafters filled a general-purpose professional engineering and design role. As the whole process of design became more complex, the role of the drafter was split into higher functions -- the specialists Cooley mentions, together with University graduate engineer designers -- and lower level jobs -- principally, drafters and support technicians. Cooley criticized the whole process of specialization and division of labor, which he termed fragmentation, on which the industrial development of the past two hundred years has been based. He writes nostalgically of the millwright who "was capable of repairing any machine in the plant in which he worked. He could predict the failure rate of bearings, select the material for new ones, and in most cases manufacture them himself." By contrast, he argued, "CAD tends to de-skill the designer, subordinate the designer to the machine and give rise to alienation. Indeed, most computerized design environments begin to display those elements which are regarded as constituting industrial alienation, in particular powerlessness, meaninglessness, and loss of self and normality" ( 1987, p. 40).

Chapter Three -- Results and Findings

Evidence supporting such views was provided by Chris Baldry and Anne Connolly on the basis of a study of seven leading CAD users in Scotland in the early 1980s (Lester, 2008). They found that much CAD work was repetitive and routine, involving details and enlargements of existing designs. Groups of drafters often worked on the same drawing, and few operators had the satisfaction of producing a complete drawing themselves. Operators had lost some elements of control over their work. The CAD system produced all drawing, labeling, and dimensioning in a standard format. Indeed, standardization of design is often a direct consequence of CAD use because CAD works most effectively if a library of standard parts and components is constructed in the computer's memory. Similarly, Kaplinsky (1982, p. 110) found that operators and management agreed that CAD reduced the skill component in drafting because it removed the craft elements associated with individually tailored layouts and lettering.

McLoughlin (1989), however, challenged Baldry and Connolly's findings on the basis of his own more recent case studies. While Baldry, Connolly, and Kaplinsky had cited the loss of manual craft skills in drawing as evidence of de-skilling, McLoughlin found that the new mental skills needed to use CAD usually compensated for the loss of manual skills. In response to the standardization argument, he pointed out that design is, in essence, a three-stage iterative process of basic conceptualization, analysis of design options, and detailed design and drawing. Most of the CAD systems in use in Britain are drafting systems, essentially electronic drawing boards serving only the third phase. They enable users to manipulate two-dimensional drawings and annotate them. CAD systems are "shape processors" analogous to word processors, which aid writers but do not reduce the need for writing skills. In addition, McLoughlin notes the increasing use of modeling systems that support more directly the earlier, more creative phases. Computer models act as malleable databases from which drawings can be extracted and displayed. They allow designers to consider several design options in some detail before deciding on a final design. They can also provide data for downstream activities such as production and thereby eliminate a great deal of routine work in recopying drawings. According to McLoughlin, "Drawing by conventional means utilizes a number of craft mental skills in manipulating the pencil, and involves a direct relationship between the thought of a user to 'draw a line' and the act of drawing." When CAD is used, "The craft skills used in actual drawing are eliminated as lines of perfect quality and weight are drawn automatically by the system. The relationship between the user and the drawing thus becomes more indirect and abstract, requiring the exercise of mental skills in understanding the capabilities of the system and in selecting appropriate routines from the menu."

Our own interviews with a small sample of CAD users tended-with some exceptions -- to support McLoughlin's findings (Watson & Petre, 2000). One user commented that CAD made his work more routine, and some complained that CAD took away the satisfaction that could be derived from producing a good drawing. The more common view, however, was that CAD increased the skills required of the designer or drafter. The most common types of positive comment made about CAD were that it made the work more interesting and less routine, and that job prospects were liable to be better in companies using CAD. For example, one CAD user commented:

Working on CAD removes a lot of the tedium of the board but also offers more avenues for being creative. It feels like you are involved with a project rather than a drawing. Creativity is improved with the greater freedom offered through, for example, the ease of iteration and change, but it is limited by the level of expertise you can develop and the poor level of system development.

Another changed his unfavorable first impressions of CAD:

I thought it took away a drafter's skills. But, after learning to use CAD, I realized that the CAD "only draws pictures.' It does not take the skills of an engineer away; it enhances them. It does not take drafting skills away. You need drafting skills to produce good work on CAD. Advantages of CAD are that it is quick and you can do more complicated things. . . . CAD makes life easier. It would be a real pain to go back to the old ways of doing things.

CAD only began to affect British engineering firms in the late 1970s and early 1980s, and did not become really significant in British design and drawing offices until the mid- 1980s. Undoubtedly, engineering and design work has become much more specialized. It is doubtful, however, that the net result has been or will be de-skilling: There appears to be little evidence for Cooley's contention that CAD has de-skilled drawing and design work and would reduce the status of the drawing office still further. Indeed, our research in the early 1980s suggested that the "glamour" of CAD was likely to restore the status of the design function and to attract University graduates into design work (Meissner, 2006).

Chapter Four - Discussions

By the mid-1970s the introduction of all the major components for highly integrated, computer-driven manufacturing was well underway. Data collection, inventory control, production planning, CAE, and CAD/CAM applications were now the norm. Numerical control tools were the other components that linked planning to actual production of goods. They were widespread by the 1980s and virtually ubiquitous in the 1990s. The important development in this second period (1960s and 1970s) was the injection of computing into machining tools.

As noted before in this thesis, the earliest tools were highly inflexible, but with the introduction of microprocessor-driven tools in the early 1970s, now called computer numerical control (CNC), machines could be quickly instructed to change their operations. That new functionality drove down labor costs, increased flexibility, and shortened the time it took to cut and bend metal, for example. Mass producers could increase the variety of products they made without building new plants. By the end of the 1970s, these tools had sensing capabilities, which meant that they could alter operations in real time, an essential requirement for the effective use, say, of robots. The availability of sensing devices drove up the sale of robotic devices; in 1981 more were sold than in all previous years combined. With such capabilities in NC equipment, manufacturing firms could extend their automation sufficiently to begin creating flexible manufacturing systems (FMS), the basic new innovation evident in the late 1980s and through the 1990s. Computers could be used to design products, develop production schedules, and then instruct machines to make them. Logistics systems could then physically transport finished goods to warehouses or load them on trucks.

As recently as the early 1960s, manufacturing executives complained that NC machining tools were too expensive and cumbersome. The situation was unimpressive. Roy A. Lindberg, a mechanical engineering professor at the University of Wisconsin, minced no words when he criticized the technology: "No manufacturer can produce an item of any consequence without knowing that it may be obsolete tomorrow." Progress in providing enhanced capabilities was slow: "The metalworking industry has been content to take automation in smaller steps" (Chandler, 1977). Standalone NC equipment at the time was made to perform screw operations, and provide electric, air, and hydraulic controls, as well as increasing amounts of tape control (which could be driven by computers since tape was a form of output and a source of programming instructions), while multiple-machine automation was in its infancy. One manufacturing expert, as late as 1973 (after the invention of the microprocessor but just before its wide application in NC tools) prognosticated that NC tools would eventually displace older technologies, although not immediately:

There are large sectors of the industrial world in which NC is basically inapplicable, and other sectors in which NC may be applicable but not economically justifiable. As a result, we can expect that NC technology will coexist with older technologies for many years to come. In fact, when these older technologies are closely examined they turn out to be themselves layered composites of still older technologies (Chandler, 1977).

This is exactly what happened. The factory of the early twenty-first century is an impressive collection of computers and robots, but the journey there has been slow and evolutionary. Numerical control was one of the gating factors for the rate of evolution to more integrated manufacturing. But slowly this new generation of equipment came online during the second half of the 1970s. In addition to being able to send instructions to individual machines, the activities of multiple devices could now be controlled and synchronized. Monitoring functions also became possible by the late 1970s. In 1981, Allen-Bradley had linked these various capabilities together, making possible updated factory operations plans. With that kind of development, processes for flexible manufacturing could be created. In effect, a majority of production steps could now be programmed in advance, started, and then controlled by computers. By having computer chips in all major factory equipment, one could communicate with machines and have them transfer data about what they were doing to each other. Two professors, experts on NC equipment and manufacturing, wrote at the start of the 1980s, after the arrival of the new generation of equipment, that "numerical control is one of the most important basic innovation of our century & #8230;it has gone far beyond the original cutting-machine tools and has revolutionized manufacturing and other areas of human productive activity" (Brown, 2009). Over 100 new types of NC equipment were reaching the market by that time.

Improvements in the ability to program and maintain this equipment in the 1980s increased the variety of uses (and hence demand) for such technology around the world, including in the United States. Traditional concerns on the part of manufacturing companies still influenced their decisions on when to acquire NC equipment: the need to lower costs of inventory, improve and maintain quality control, and operate with shorter production cycles. Economist Roberto Mazzoleni observed that "during the 1980s, the competitive strategies of U.S., European, and Japanese companies were characterized by an increasing quest for manufacturing flexibility and a movement toward small- and medium-batch production runs," which led to increased demands for this kind of technology. This execution of the strategy caused firms around the world to install applications for jig boring, gear cutting, laser cutting, electro discharges, and grinding for special purpose jobs; development of systems for rotational and prismatic parts for general purpose work; and creation of special purpose systems to support flexible transfer lines and FMS with specialized equipment. Machine and turning centers within factories also were equipped. Flexible manufacturing factories increased from 8 in the United States in 1975 to 28 in 1980. In 1995, there were approximately. In that year, Japan claimed to have 166, Western Europe 208. The point is not so much that one nation or another was ahead but rather that manufacturing had changed extensively. Large American factories tended to rely on more inflexible transfer line approaches, but even these became more flexible during the 1980s (Schroff Development Corporation, 2011). One study, comparing the number of product variants processed by FMS factories in different countries, turned up the fact that in the mid-1980s 41% of those U.S. factories that claimed to have FMS could handle up to 10 variants, another 22% could handle up to 50 variants, and another 13% up to 100 variants. This compared very closely to the Japanese production capability, whereas Western European factories had less flexibility.

Future of CNC Machines

CNC or "computer numerical controlled" machines are complicated metalworking gear that can make complex parts essential in modern machinery. Rising fast with the leaps in computer technology and sophistication, CNCs can be seen performing jobs such as lathes, milling equipment, laser scissors, abrasive jet shears, punch presses, press brakes, and various other industrial gear. The CNC term is used to define a big group of these equipment that use computer logic to organize movements and carry out the metalworking.

1. Spider-like CNC Machine

The potential and prospective future of CNC machines is expanding massively. One design under design is a spider-like machine which a spindle that is balanced by six perfectly set telescoping ballscrew struts. The struts are similar to the gears in a traditional machine, except they are circular and with the ballscrew assemblage in the middle (Lester, 2008). The movements of the spindle are carried out by an advanced computer calculating millions of mathematical formulas to guarantee accurate part functioning.

Even though, this machine can cost several million dollars to build and utilizing high level, R&D mathematics, this apparatus assures performances that were in the past unthinkable functions and uses in metal machining. Progress in processor chips and artificial intelligence will make CNC machines in the future quicker and easier to control. This will however not come reasonably, and the cost of complicated CNC machines will be further than the reach of many firms. It might, on the other hand, decrease the costs of the fundamental CNC machines carrying out the traditional three-axis movements.

2. Laser Technology-based Micromachining

In plain words laser technology core micromachining is the slicing, drilling, tearing and skiving a variety of kinds of substances such as glass, plastics and particular types of elements. The accuracy of laser technology is unrivaled and so is the pace at which it is carried out. The technology has non-staff communication with the material as a result is an effortlessness of carrying out the process. Laser micromachining is more often than not used in creating purposely small three dimensional equipments.