Application of PLC and AC servo in NC drilling and

Application of PLC and AC servo in NC drilling and milling machine

Abstract: This paper introduces the successful manufacture of NC drilling and milling machine with domestic PLC and AC servo control system, and discusses the system composition, hardware configuration and program design for actual product workpiece processing

key words: CNC drilling and milling machine; PLC； AC servo; Frequency converter; Spindle

introduction: among the newly developed products, there is a long aluminum base with the model of Q7, on which two are processed φ three point seven × The flat bottom blind holes of 1.65 can not be processed on the drilling machine with the traditional drilling jig, and it is difficult to process on the traditional milling machine because of the high accuracy and large batch. Even if they can be processed, the efficiency is very low, and the equipment loss and power loss are also very large. The processing of this workpiece is very representative, and many products have similar requirements. Therefore, we designed and manufactured a general-purpose CNC drilling and milling machine for the processing of this kind of products

I. system overview

the system composition is shown in Figure 1. The control part adopts PLC and is equipped with a human-machine interface to modify and set program parameters,

and monitor the operation status display, and the contents of the human-machine interface can be programmed. The three axes are all digital AC servo systems. The servo motors of each axis drive the ball screw through the coupling to move the worktable and spindle milling head equipped with linear guide rail. Its positioning is accurate and its speed is fast. The spindle milling head is controlled by the frequency converter. According to the tool, workpiece and feed rate, the reasonable speed of the spindle is set, and its start and stop are set in the program. Each axis is equipped with two end limit sensors and origin sensors. Abnormal detection is also available for cooling and lubrication, and alarm information is displayed at the alarm light and human-machine interface. In order to facilitate debugging and maintenance, all operations are set with manual functions, such as manual speed movement of each axis, high and low speed rotation of the spindle, cutting fluid and lubrication switch, etc. Although the whole machine tool is semi closed-loop control, as long as the options, assembly, programming and operation are reasonable, the accuracy and stability can still meet the use requirements

II. Hardware configuration

plc uses Yonghong's fbs-40mct, which has high cost performance, small size, strong functions, 24 point input, including 16 point high-speed counter, with a frequency of 120K, 16 point output, including 4-axis stepping or servo output integrated in it, with an output frequency of 120K, making it very convenient to apply and simple to connect. The programming software winproladder is known as the master of ladder diagram. It is easy to learn and use and has powerful functions. The operation of, monitoring, debugging and so on is very easy. The combination of keys, mouse and real-time command function query and operation guidance make the input efficiency double

the most remarkable achievement of contact distribution is the professional experience of mass production of composite plate springs: take the z-phase signal of the servo motor of each axis as the origin switch, tap it at several high-speed input points, and use interruption to reset the origin of the machine tool. The rest of the limit switches, operation switches, liquid level detection and other conventional contacts can be accessed in sequence. 10. The Y-axis and z-axis servo motors are connected to the front 3-axis servo output points, and the spindle high and low speed, cooling, alarm, etc. are connected to the other output points

x, y and Z3 axis servo systems are the same. Hollysys es series full digital AC servo driver 0040e-cbcee-02, a luxury coupe with two doors and 2+2 seats, has a power transmission system of "electric high-performance hybrid" and a 60 series small inertia servo motor 60cb040c-2de6e. The servo system has relatively complete functions, such as energy consumption braking, electronic gears, automatic acceleration and deceleration to improve labor productivity, and has a variety of pulse train inputs. The protection functions are also relatively complete, including undervoltage, overvoltage, overcurrent, overload, locked rotor, stall, position out of tolerance, encoder abnormality, etc. In this equipment, it is connected to PLC according to the open collector drive mode, the maximum pulse input frequency is 200K, and the servo on and z-phase signals are also connected accordingly

the frequency converter adopts the dzb70b0015l2a of Fuling, the specification is single-phase 1500W, 400Hz, and there are multiple step speeds for use. Since the speed change is not frequent during normal use, the speed adjustment setting is not led out. It is only adjusted on the operation panel of the frequency converter. Two speeds are set, high speed for processing and low speed for tool setting. Adjust relevant parameters to match with the spindle, such as fundamental frequency, fundamental voltage, upper limit of operating frequency, carrier frequency, etc., and change the corresponding jumper

the spindle does not adopt the traditional method, but adopts the electric spindle for engraving machine according to the processing needs. The adxz/1 model of Anyang laibitai has small volume, low noise and only 80mm in diameter, which makes the whole spindle box easy to be sealed as a whole, which can effectively prevent the debris in processing from splashing on the lead screw and guide rail of axis Z, causing damage, and also make the appearance of the spindle box beautiful. Its maximum speed is 24000 rpm, so that the normal working speed has a suitable margin range

the man-machine interface adopts the general programmable text display md204l of man-machine electronics, which can monitor and modify the value and status of PLC internal registers or relays in the form of text or indicator lights

III. software design

the flow chart of the machine tool is shown in Figure 2. After starting up, check whether the manual switch is effective. If the manual switch is effective

, use each manual control switch to execute the manual operation items. If the manual switch is invalid, start the zero point reset program, and reset the machine tool zero point for each axis. First return to the Z axis and then the other two axes. The brand reputation will be further expanded. The next step can be carried out only after all axes have been successfully reset. If the tool, fixture and workpiece program have not changed, it can be reset to the processing preparation state without tool setting. If tool setting is required, turn on the tool setting switch to start the tool setting program, and set the tools for the three axes respectively, that is, find the workpiece origin, and use the manual axis movement switch to move each axis quickly and slowly, so that the three sides of the workpiece touch the low-speed rotating tool respectively, just until they touch it. After alignment, press OK to confirm the tool setting, and then enter the tool compensation. After program processing, the workpiece origin is formed, that is, program 0 point. When programming, calculate the tool path according to the drawing according to this 0 point, so that the operator can have a clear idea and simple calculation. The operator's is a user program, which can track the tool path, that is, the moving coordinates of each axis, as well as the moving speed, the number of cycles during circular processing, etc. Reset to preparation after programming or when using the current program