Communications in Control Science and Engineering (CCSE) Volume 4, 2016
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Design of the NC Drilling and Milling Machine Based on Fischertechnik Creative Model Combination Shaoke Chen*1, Lin Chen*2 Mechanical Engineering Department, Shantou University, Shantou, 515063, Guangdong, China skchen@stu.edu.cn; *2chenlin@stu.edu.cn
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Abstract This paper presents a method of building a NC (Numerical Control) drilling and milling machine model with a Fischertechnik creative model combination. It introduces the simulated design and control of Fischertechnik creative model combination. It uses PLC to control step motors to drive the NC drilling and milling machine simulation model movements, including point movement, linear interpolation, circular interpolation, drilling etc. Rotary tables and drill angle adjusting devices are built based on the traditional vertical milling and drilling machines. It creates a convenient place to drill inclined holes and adjust workpieces. The design process is illustrated by examples of the traditional NC drilling and milling machine. After practice, the model is proved to be functionally reliable, and can meet the needs of teaching and scientific research. Keywords Fischertechnik; PLC; NC Drilling and Milling Machine
Introduction The Fischertechnik creative model combination is a new engineering model, which can demonstrate scientific principle and technology process, and provide simulation demonstration for enterprise research and design of industrial automatic machine. It can also be widely used as teaching aids, and can be continuously renovated and developed. The model has the advantages of less assembly time, strong technical components, convenient control interface etc. It can help realize many kinds of control modes and model designs (i.e. computer control mode, PLC control mode, single-chip microcomputer control mode) [1]. Through the design of NC drilling and milling machine based on Fischertechnik creative model combination, we can provide a theoretical basis and experimental data for the actual design of NC drilling and milling machine, thus speeding up the design process. Using Fischertechnik’s various parts, including gear, platform, upright column, worm wheel, worm gear, miniature motor, travel switch, fasteners and all kinds of connectors, the upright-drilling machine model can be built according to the design requirements. Most of these parts are made of engineering plastic, containing a considerable strength and hardness. Plus, with the processing size standards and high accuracy, the model is steadier. Function Design of NC Drilling and Milling Machine [2] Drilling machine is a machine that is used for hole drilling. The main processing is for workpieces with complex and non-symmetrical rotation axis. Drilling and milling machine is widely used. It can be used not only for drilling, expanding and hinging, but also for simple milling process. Its characteristics include the spindle axis vertical arrangement, the workpiece on the work table, the table and the feed box that can be adjusted up and down along the column. In order to adapt to different heights, the table can be horizontally and vertically fed, and the platform can be rotated. According to the drawing, the NC drilling and milling machine compiles program and transmits it to the numerical control device. The machine controls variable speed of the main movement of the tool, e.g. start and stop, feed motion direction, speed and displacement, and other factors such as choice and exchange of the tool,
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Communications in Control Science and Engineering (CCSE) Volume 4, 2016
clamping and loosening of workpiece, start and stop of the cooling lubrication. And other auxiliary devices can be strictly designed in accordance to the order, route and parameters of the NC program so as to process the shape, size, and precision that meet the requirement of parts. The design of NC drilling and milling machine includes mechanical design and its corresponding drive control design. Using Fischertechnik creative model combination, PLC, step motor and corresponding drive, the simulation model can be built. The basic processing movement of drilling and milling machine is completed through controlling PLC, including point motion, continuous motion, linear and circular interpolation etc. Traditional drilling and milling machine cannot mill circle; it also needs to readjust the clamping workpiece and install angle. Thanks to the rotary table and corresponding drive on the platform, it can be used to mill different arcs. With a rotary joint on the drill feed shaft, the adjusted angle for the drill can be read. Mechanical Structure and Design The mechanical structure of machine is the main part of the NC drilling and milling machine. All kinds of control movement and action instructions must be translated to real, accurate mechanical movements and actions through the mechanical structure in order to achieve the function of NC machine and to ensure the performance requirements. The diagram of machine structure of NC drilling and milling machine is shown in Figure 1. It is divided into four major parts, namely the under carriage, the upper carriage, the rotary table and the vertical direction shaft [3].
FIG. 1 SHCEMATIC DIAGRAM OF NC DRILLING AND MILLING MACHINE
Left and Right Movement of the Under Carriage The under carriage is driven by step motor M1. It can move from left to right and right to left. The movement range is determined by the left and right switches. Back and Forth Movement of the Upper Carriage The upper carriage is built under the upper carriage and is driven by motor M2. It can realize back and forth movement with the direction of movement; and under carriage is orthogonal. When under carriage does not move, the movement of the upper carriage is linear; when the upper and the under carriages move together, the movement will be two motion synthesis. The upper carriage can be used as a work platform, and a rotary table can also be set above it. Rotating Motion of the Rotary Table The rotary table is built on the upper carriage, and can move independently. When the upper and under carriages
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Communications in Control Science and Engineering (CCSE) Volume 4, 2016
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and rotary table move together, it will be the combination of several motions. Therefore, the reasonable control of the movement of the upper and under carriages, and rotary table, can interpolate all kinds of arcs. Feed Motion in Vertical Direction The main function of the vertical axis is vertical feed, driven by motor M4 by giving up-and-down movement. Motor M5 is responsible for the rotation of the drill or milling cutter. This design adds the adjustment devise for vertical axis. Therefore, the vertical axis increases the vertical angle adjusting mechanism in this design while the traditional ones can only feed along the vertical direction. Only adjusting the angle of the plumb line appropriately can you process the inclined hole on the rotary table. It helps avoid the problem of reinstalling, which saves time and improves work efficiency, while avoiding clamping error, and improving the machining accuracy. Drive Control Design A complete machine model not only contains mechanism model design, but also a corresponding driving control design. While using PLC control step motor, the imbedded special step motor in PLC is usually used to control the intelligent module. It helps realize the drive control. Open loop servo mechanism was driven by stepping motor in the numerical control slide of NC machine. It is composed of programmable controller, ring pulse distributor, stepper motor driver, step motor and service drive mechanism and other parts, as shown in Figure 2 [4].
FIG. 2 PLC CONTROL STEP MOTOR SCHEMATIC DIAGRAM
The PLC program includes the function of the ring distributor and power driver, and it is a novel design method. Using this method, it can help save the expensive power amplifier. Meanwhile, the control program of PLC also contains the logic connection between ring divider and drive circuit, which indicates that the control program of PLC will become very complex, and the difficulty of programming will be increased a lot. In this design, the internal structure of the step motor VEXTA-PX243-C18 is measured and the operation logic cycle is determined by experiments, so that the motor can rotate in a desired way. The following article will introduce the research and design of the driving part step by step [5]. Continuous Rotation Control Step Motor Continuous rotation is not only the basic movement of the machine, but also the main movement of the feed mechanism. Its main function is to achieve feeding or fast movement of the machine. The motor or other feed mechanism can continue to move when the control switch is connected, and it can also stop motion when the control switch is closed or other restricted movement happens (such as stroke limit or sudden stop). The current status and posture can be maintained after stopping. And exercise continues after the connection. Point Control of Step Motor The so-called point motion refers to the control procedure that the controller sends a single pulse to the motor, the rotation of the motor turns a step angle, the perform element to move a pulse equivalent and thus realize maximum accuracy. The specific performance is as follows: each time the operator touches the switch, the motor turns a step angle. Different from the control of continuous rotation, the point control needs to be restricted in the annular distribution program section. The input pulse signal is assigned to each winding of the step motor according to a certain order. PLC output ports Y0, Y1, Y2, Y3 are connected with the motor pin. The operating state of the respective caltulatos and the corresponding Y output is achieved, among which X10 is the trigger of rising edge. Every time when it is connected, it equals to a point pulse that is delivered to the motor. C0 to C3 are general
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Communications in Control Science and Engineering (CCSE) Volume 4, 2016
caltulators. Its role is to record the number of times through caltulator X10. When X10 is triggered for four times, C0~C3 will be automatically reset. Linkage Control The linkage movement not only meets the basic movement requirements, but also the requirements of transmission, including travel requirements, emergency pause requirements, reset requirements, etc. Thus, the linkage control requires to combine all kinds of basic motion control procedures and strengthen its function. All motion control program is integrated, while increasing the six stroke switch control of three motion axes, reset control of three axes, rotary working table control and two axis linkage linear interpolation control. System Test When the program is completed, it can be tested online. With the appearance of MITSUBISHI PLC and its Fxgpwin software, it is able to edit on the computer and modify the program. Through the RS232C serial communication interface, the directly-modified program can be transmitted to EPROM of PLC. Then the PLC input and output terminals can be connected to the corresponding electrical components (buttons, switches, motor), and the machine can be tested. Fxgpwin software also has the function of on-line monitoring, which can monitor the state of each I/O element directly on the computer screen during the running of the program. Conclusion Due to the high technological content and boundless creativity of Fischertechnik, not only do a lot of foreign industrial enterprises use it to simulate large-scale mechanical equipment, but also many European countries are widely using Fischertechnik as a teaching aid to implement teaching theory. The creative possibilities of Fischertechnik model combination provide inexhaustible supply for different industries. This paper shows the design of mechanical model of NC drilling and milling machine based on the Fischertechnik innovative model combination. And it analyzes its movement process by using the design process of various motions and interpolations controlled by PLC step motor. The realization of the Fischertechnik model combination facilitates the design process for people who work in the fields of innovative mechanism and automatic control. Engineers can create their own designs, and start preliminary verification and modification at a low cost. ACKNOWLEDGEMENT
The authors want to thank the special funds (No. 3013B011302009) from Guangdong Numerical Control Machinery Product Innovation Application Demonstration Project, the Co-operation of Industry-University-Research Institute (No. 201461), Jieyang, Guangdong, P.R.China, and Shantou Industrial Research Plan (No. 2013163 and No. 2013163), Guangdong, P.R.China. REFERENCES
[1] Sheng, Chen. Design on Virtual Simulation Based on the Fischertechnik Model. Mechanical Research & Application, 28 (5) 230–232, 2015. [2] Xiaojun, Tian, and Hongtao, Ren. Design Automatic Vertical Drilling-milling Machine by Fishertechnik Teaching Models Journal of Luoyang Technology College, 11 (4): 18-20, November 2001. [3] Xurong, Zhou, and Tianjun, Liu, and Jianan, Liu. The Design and Fabrication of Multi-functional Reel Whiteboard Based on Fischertechnik Model. Journal of Changzhou Institute of Technology, 27 (4): 7-11, 2014. [4] Qing, He, and Junyi, Feng. Design of Intelligent Lawn Trimmer based on Fischertechnik Model. Journal of Chinese Agricultural Mechanization, 35 (5): 99-117, 2014. [5] Liqiang, Tao, and Heng, Zhang. “Research and Application of PLC Technology on CNC Machine Tools.” Machinery &
Electronics, (1): 72-74.
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Communications in Control Science and Engineering (CCSE) Volume 4, 2016
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Shaoke. Chen Born in Shantou, Guangdong, China, on November 7, 1956. Professor at Shantou University. Studied mechanical engineering at South China University of Technology from Sept. 1977 to Jul. 1981. Taught at Huaqiao University (Fujian Province) from Sept. 1981 to Feb. 1992. Teach at Shantou University from Feb. 1992 till now. Mainly focus on teaching and research on electromechanical control, CAD/CAM, mechanical design, etc.
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