Application of PLC in low space drop hammer hydraulic automatic pile driver

I. INTRODUCTION The low-space drop-hammer hydraulic automatic pile driver is a new type of construction machinery. Its outstanding feature is that it can complete the piling task under low space conditions. Therefore, the pile driver better solves the problem of piling in low space such as the elevation of old houses, the correction of buildings, and the reinforcement of building foundations. Programmable Logic Controller (PLC) is an industrial computer designed for industrial applications. It is small in size, reliable in operation and rich in functions. It can perform various logic operations, sequence control, timing, counting, step control and online monitoring. Features. Therefore, the hydraulic automatic pile driver can be controlled by PLC.

Second, the low-space drop hammer hydraulic automatic pile driver hydraulic system introduction The composition and working principle of the pile driver is detailed in the literature [1]. This article only refers to the hydraulic system schematic, as shown in Figure 1. In the figure, the Hydraulic Cylinder 10 is a clamping cylinder, which functions to clamp the pile driver on the support rail, and the pressure relay 9 functions as a complete protection to ensure that the pile driver can work normally only when the pile driver is clamped. . The hydraulic cylinder 11 controls the raising/lowering of the weight. The working stroke of the weight is adjusted by the travel switches XK1, XK2 mounted on the carriage. The hydraulic cylinder 14 controls the raising/lowering of the carriage. The electromagnetic spill valve 16 allows the hydraulic system to be unloaded during periods of inactivity to reduce power loss in the hydraulic system.

According to the composition of the hydraulic system and the working requirements of the pile driver, the action cycle table of the automatic pile driver is shown in Table 1.

The whole machine clamps the jog to adjust the carriage ascending the carriage, the descending carriage, the floating hammer, the hook, the drop hook, the hanging hammer, the hammer, the whole machine, the stop, the note: the power is turned on, indicating that the power is off, 7YT indicates that the control hook is loosened/clamped by the electromagnet. PLC control system design 1. Hardware design Because the working environment of the pile driver is the construction site, the dust and humidity are large. If it is controlled by the traditional contact relay, it is bulky, inconvenient to transport, and the contacts are easily damaged. For this purpose, the currently widely used F1 series PLC controllers are selected. According to the number of input/output points of the control object, F1-20MR is selected, and its I/O is allocated as follows.

Input point: Output point: Clamp button: X400 clamping electromagnet 1YT: Y430 release button: X401 hammer electromagnet 2YT: Y431 hammer button: X402 drop hammer electromagnet 3YT: Y432 drop hammer button: X403 carriage rise Electromagnet 4YT: Y433 carriage rise: X404 carriage drop magnet 5YT: Y434 carriage down: X405 unloading electromagnet 6YT: Y435 oil pump start: X406 hammer electromagnet 7YT: Y436 oil pump stop: X407 pump start contactor KM : Y437 travel switch XK1: X machine tool electrical appliance 2000 No. 2 computer? PLC application pressure relay YJ: X automatic / jog conversion: X PLC external wiring diagram shown in Figure 2.

2. Software Design The functions to be realized by this pile driver are as follows: Clamping and loosening of the clamping cylinder? The rise and fall of the carriage? Jog adjustment and automatic piling? The positive and negative movements of each hydraulic cylinder are interlocked, and there is a delay link? The weight movement and the carriage movement interlock, and the solenoid valves and the oil pump motor are interlocked. When the weight or the carriage does not work intermittently for more than the specified time, it will be unloaded automatically.

According to this functional requirement, the control program is mainly composed of the following links.

(1) The rise and fall of the carriage can only rise or fall after the oil pump motor starts and the pressure relay (YJ) operates. Since the carriage will only operate in the case of picking up the pile, it is a short-time work system, so jog operation can be used.

The control ladder diagram is shown in Figure 3.

(2) Jog adjustment of the hammer and automatic piling section This function link is the core content of the control program. The ladder diagram is shown in Figure 4.

In this ladder diagram, X is an automatic/jog transfer switch, X and X are the upper and lower limit switches of the weight working stroke, respectively, and X402 and X403 are the weight rising and falling buttons, respectively. The on/off of the electromagnet (Y436) of the hammer is instantaneously related to the on/off of the stroke switch, and there is a delay between the on/off of the electromagnet that controls the rise/fall of the weight. This is because when the hook hangs the weight and moves up to the stroke switch XK1, the hammer electromagnet is energized immediately, and the hook releases the weight. At this time, the movement of the weight is the upward movement, that is, the weight is still raised. The rise time is t /2g. Therefore, when the hammer electromagnet is energized and released, it is not appropriate to immediately start the electromagnet that controls the drop of the hook, but there must be a certain delay time, and the drop of the weight is a quasi-free fall motion. The speed is greater than the downward movement speed of the hydraulic cylinder control hook, so when the hook hits the XK2, the weight has completed the piling movement and stays on the pile cap. However, considering the mechanical inertia of the hydraulic solenoid valve commutation, a short delay link [2] is also set to ensure the reliability of the system operation.

(3) Unloading link When the hydraulic cylinder that controls the movement of the weight and the carriage does not work intermittently for more than the specified time, the hydraulic system automatically realizes the unloading function. The ladder diagram is shown in Figure 5. It is equipped with a timer and a counter to realize the timing function. The working pause time can be set arbitrarily (X =1 , 2 , 3 ,...

computer? PLC application machine tool electrical appliance 2000 No. 2 points).

IV. Conclusion 1. The low-space drop-type hydraulic automatic pile driver is controlled by F1-20MR programmable controller. Its outstanding features are: small size, light weight, convenient handling, and reliable operation in harsh construction environment. The performance price is relatively high.

2. Using PLC control, the design and production cycle of the electrical control part is very short. By changing the program, various working cycle states can be changed, which is very convenient and flexible to use.

3. Using PLC's internal timer and counter, it is convenient to control the length and accuracy of delay time, which has unparalleled superiority compared with contact time relay.

1 Zhang Shiliang, Luo Zhonghui. Research on low space drop hammer hydraulic automatic pile driver.

2 Luo Zhonghui. The application of PLC timer in machine tool electrical control. In the machine tool electric programming, the timer cascade uses the precise timing of the timing value. The chronograph of the clock counting and counting instructions of the Wangzhong 8.3 factory in Hanzhong can expand the timing range of the timer, and it needs timing and delay in industrial production and scientific research experiments. It is often used from time to time. For generally less precise timing or delay, the PLC scan period (CEs series 0.02s) may be disregarded, but for some more demanding experiments or timings in the production process, it has to be considered. The following is an example of the problem of accurate timing of the timer in the CE-I series PLC.

In CE-I, the maximum preset value of each timer is 999.9s, and the maximum preset value of each counter is 9999. If the required preset value exceeds the maximum preset value, several timers and counters can be passed. A cascade connection to extend the range of preset values.

For example: a motor requires 30 minutes to start, because 30 × 60 = 1800s, greater than the maximum preset value, can be achieved by the cascade connection of the timer and the counter, as shown in Figure 1.

T613 is a self-reset timer with a preset value of 2s. When the contact is turned on, T613 is turned on every 2s, and each turn-on time is one scan period. Counter C614 performs a normally open contact on this clock pulse. The output relay 21 is turned on, and the drive motor is started.

However, for accurate timing, it should be considered that the timer T613 takes one scan period (0.02s) each time it is turned on, then the counter C614 counts the pulse signal 900 times and will have 900×0.02 = 18s. That is to say, the precise timing should be 900×2 900×0.02 =1818s, which is 18s longer than the original set time. This may not cause accidents for some equipment and process requirements, but if it is required for high precision and process comparison Complex CNC machine tools may cause motion disorder, the consequences of workpiece scrapping, to accurately time, you should consider the scan cycle, you can set the counter's set value to X, then the timing of 30 minutes is calculated as follows: 2X 0.02X = 1800, the solution is 0.18s, which is much smaller than the original error and can meet the requirements.

Machine Tool Electric 2000 No. 2 computer? PLC application