Theory and Design of CNC Systems (Springer Series in Advanced Manufacturing)
Language: English
Pages: 456
ISBN: B004G09O4S
Format: PDF / Kindle (mobi) / ePub
Computer Numerical Control (CNC) controllers are high value-added products counting for over 30% of the price of machine tools. The development of CNC technology depends on the integration of technologies from many different industries, and requires strategic long-term support. “Theory and Design of CNC Systems” covers the elements of control, the design of control systems, and modern open-architecture control systems. Topics covered include Numerical Control Kernel (NCK) design of CNC, Programmable Logic Control (PLC), and the Man-Machine Interface (MMI), as well as the major modules for the development of conversational programming methods. The concepts and primary elements of STEP-NC are also introduced. A collaboration of several authors with considerable experience in CNC development, education, and research, this highly focused textbook on the principles and development technologies of CNC controllers can also be used as a guide for those working on CNC development in industry.
The Progress Direction of the CNC System Over the last 50 years, the advance of NC and CNC can be summarized as shown in Fig. 1.18. NC systems developed in the 1950s were implemented based on hardware and research for replacing the hardware components with software components got under way. The advancement of electrical technology in the 1970s - 1980s, especially, meant that the NC system became a CNC system whose functions were executed by a micro processor. However, the CNC system is a closed
next interpolated point to P(ui+1 ). To calculate the speed to P(ui+1 ) from P(ui ), it should be assumed that the previous interpolated points P(ui−2 ), P(ui−1 ), and P(ui ) are located on the same circle. It is assumed that the successive interpolated point P(ui+1 ) is located on the same circle. Based on these assumptions, the curvature of the partial circle from P(ui ) and P(ui+1 ) is extrapolated from the curvature of the circle defined from P(ui−2 ), P(ui−1 ), and P(ui ). Using the maximum
Input Pulse: Δ X(k) 10 10 10 10 10 10 10 10 0 0 0 0 80 Output of Adder: 5 15 35 45 50 50 50 50 45 35 15 5 Output Pulse: Δ Xo (k) 1 3 7 9 10 10 10 10 9 7 3 1 80 4.2 Acc/Dec Control After Interpolation 117 10 9 8 7 6 5 4 3 2 1 0 2 4 6 8 10 12 14 Fig. 4.8 Output of circuit for S-shape curve 4.2.2.3 Exponential-type Acc/Dec Control Figure 4.9 shows the Exponential-type Acc/Dec control circuit that is constructed using DDAs unlike the Linear-type Acc/Dec control circuit and the
of the two time–pulse graphs in Fig. 4.13b and Fig. 4.13d. As shown in Fig. 4.14, in Continuous Mode, reduction of speed does not occur at the corner between two success blocks join. The speed is accelerated or decelerated considering the difference in the feedrate of the two blocks. Pulse Pulse Acc/Dec control Time Block 1 Block 2 Time Block 1 Block 2 Fig. 4.14 Time–pulse graph for two successive blocks 4.3 Acc/Dec Control Before Interpolation Unlike ADCAI-type NCK, ADCBI-type NCK
detected, a critical gain (Ku ) and critical frequency (Tu ) can be extracted. Finally, the PID controller’s gains are obtained by the equations shown in Table 5.1. If system oscillation does not occur, even when the proportional gain is increased, this method cannot be applied. The Ziegler–Nichols method is good and simple for gain tuning, but needs a fine tuning process by a tuning expert. Also, it cannot achieve satisfactory control performance in the case of a system having small damping