The CNC ensures production rate

Helping to optimise production in series are, for example, systems of control in high end of the Series 30i/31i/32i of GE Fanuc. They are equipped with the most advanced processors for high speed, an internal high speed bus and a powerful servo control system. In addition to rapid cycles of servo control and head, the high resolution of the encoders for position, they offer up to 16 million pulses per revolution, is very advantageous. Especially practical is also the PLC integrated with its own processor of high speed, which reaches speeds of implementation of up to 25 ns/step programme of contacts, and can run up to three of them simultaneously. Peripheral devices that are part of the complete process, such as changers tools, feeders of parts, etc., can thus handle quickly and smoothly.

Automated processes typically exercise an important role in mass production. The basic requirement for this is the provision of a communication structure, which machines are connected through their CNC Controls. Systems network, such as Ethernet, and the transfer of data via FL-net, Profibus and other bus systems provide all the necessary information as required.

As Edgar Weiter, expert in applications of complex machines of GE Fanuc Automation CNC Europe, know from experience: "load data, put it in place and leave to work on its own - this is as production managers can see the ideal automated production." The burden of the pieces, checking of components, the re-mecanizado and the withdrawal of the pieces has undergone a tremendous change in recent years. "Often are systems of robots, which have evolved to become more effective and affordable, those responsible for these changes." Sensors and vision systems ensure that robots act very quickly and accurately. They can, for example, take not classified billets, classify them, supply them to the machine and even separate the wrong parts.

For all these solutions of automation, communication with the CNC is essential. GE Fanuc has a long experience in this field. On the one hand, the production of Fanuc in Japan, at the foot of Mount Fuji, is highly automated; on the other hand, Fanuc is also one of the leading manufacturers of robots. While the robots have their own systems of control, they can communicate with CNC machine tool via a simple field bus link. Connecting a cable and loading the software, the user creates a direct link, that even can be after sunset in motion of the machine tool. In addition, so it is not necessary to make major changes in the software of the machine or the robot.

But not only is the environment of the machines which should be designed for the production on a large scale, since that also own machines contribute greatly to the success of the production. The control system of CNC, in fact the brain of the machine, is responsible for the machine to move in such a way that, even hundreds of thousands of times, an equal and high qualitative value component is produced in the shortest possible time. To this end, GE Fanuc, leader of the world market in CNC technology, has developed special features that the end user can be applied as needed.

One of these functions is integrated in the system control of CNC series 30i. The "learning the piece" allows control system to learn from the mistakes. Edgar Weiter describes this function in the following way: "With the learning of the piece can optimize axial movements for each component during the milling or turning and, with some depending on the speed, increase the precision." "The shape of the piece and axial movements are captured by the measurement system and transmitted to the CNC, which optimizes your settings accordingly to generate optimized movements, with minor vibration errors and greater precision in the following piece."

The learning of the piece can not of course, transgress the laws of physics, such as for example the relationship of interdependence between speed and accuracy. But just compensating for thermally errors and inaccuracies caused mechanically, the function can be achieved in most cases a clear increase in the speed with the same accuracy. And, as already mentioned: during mass production, every second counts.

To start learning, the user must first to operate the machine with two or three pieces to obtain the necessary data for comparison. The CNC control system automatically optimizes the whole process and fixes incorrect values caused by wear and tear, the raising of the temperature and other factors that usually occur during the production of large series.

This function limits depend on in part from the main memory of the CNC control system, control system must be able to store all the measured values and compare them with those who had already picked up. For this reason, in order to use the learning of the piece, a coded program not be unlimited long and complex. A length of two-minute program is currently possible, and this value will be gradually increasing with the constant improvements in the hardware and the ever-increasing storage capacity.

The function called the selection of the conditions of machining is also used to optimize the relationship between the speed of machining and precision, although not through the values measured for the component, or not automatically. In this case, is primarily a simple system with ten selectable levels, ranging from the highest precision (at low speed) at the highest speed (with less accuracy). Depending on the type of machining, from the pre-desbaste to the fine finish, the user can select the appropriate level and modify it at any time by pressing a key. Even during mass production, worth investing some time and run several cycles to test mode. The optimal settings determined in this way both rewarded more the greater is the number of pieces in the series.

Processing of binary data: the shortest path

In the manufacture of piston engines and similar components, during which recur frequently subprogrammes, GE Fanuc CNC control systems can also be programmed directly using binary data. This has the advantage that it is not necessary to move data to the control system, and can be directly channelled to the axes. Times of interpolation very low and high machining speeds can be achieved in this way. Edgar Weiter gives an example: "In France just a machine for milling of crankshafts with this processing of binary data." In this application, both the central core, and the eccentric stumps are milled in a revolution. This is done via a blade of milling that it moves back and forth, depending on the shape. The data for the process of milling are saved in binary format, that the procedure is repeated for each crankshaft. "This represents a clear saving in time with respect to the use of the subprogramme, for which the ASCII data must be read and compiled". The user is still the possibility of introducing some data correction, although the program itself is processed in binary format.

' Until now, a drawback of the processing of binary data was the large volume of data for programs of machine, because each segment of interpolation must be described. However, thanks to the ever greater storage capacity available, the area of application of this type of programming is spreading.

The use of binary data it is also interesting in relation to the operation function history table, that facilitates the interpolation and timing of different axes and simplifies the programming of multi-channel operations. The conventional subprogrammes for such applications consist of several blocks, in which the time and the speed which is must interpolate a particular position is defined for all axes. The operation with table background, on the other hand, for each individual axis is available a subprogramme which is function of a magnitude or control variable. Edgar Weiter explains: "In principle, is like a table in which the first column contains variable control, on the basis of which they are given all the others." This variable control is usually a time, but can also be a position of the head or shaft. "The programmer instructs then the positions of the axis sequentially for each individual axis according to that variable's control."

These individual subprogrammes are stored in the control system or later, can be processed directly from a PC, which are compiled as binary data. Edgar Weiter said his relationship with series production: "The transaction history table is used with complex machines for applications that use multiple axes, usually distributed in different channels." The function operates through different channels, since they can be available according to a common timeline. These machines are mainly used in mass production, as that may be involved in an extensive programming work. "Through the operation with table background, this effort is reduced significantly."