introduction
In the newly developed product, there is a long aluminum base of type Q7. Two flat blind holes of φ3.7×1.65 are to be processed on the top. Due to the high precision and large batch size, it is impossible to use traditional drills. Drilling machine processing is also difficult to machine on conventional milling machines, even if the processing efficiency is low, and equipment loss and power loss are also large. The processing of this workpiece is very broadly representative, and many of the products produced have similar requirements. To this end, we have designed a device for processing such products - a universal CNC drilling and milling machine.
First, the system overview
The system structure is shown in Figure 1. The control part adopts PLC and is equipped with man-machine interface for program parameter modification and setting, as well as operation status display monitoring, and programmable man-machine interface content. The three axes are all digital AC servo systems. Each axis servo motor drives the ball screw through the coupling to move the table with the linear guide and the spindle milling head. The positioning is accurate and the speed is fast. The spindle milling head is controlled by the inverter. According to the tool and the workpiece and the feed amount, the spindle is set to a reasonable speed and its start and stop is set in the program. Each axis is equipped with a two-terminal limit sensor and an origin sensor. The cooling and lubrication also have abnormal detection, and alarm information is displayed at the alarm light and the human-machine interface. In order to facilitate debugging and overhaul, all operations are equipped with manual functions, such as manual movement of each axis, spindle high and low speed rotation, cutting fluid and lubrication switch. Although the whole machine is semi-closed control, as long as the options, assembly, programming and operation are reasonable, the accuracy and stability can still meet the requirements of use.
figure 1
Second, the hardware configuration
PLC selects Yonghong's FBS-40MCT, which has high cost performance, small size, strong function, 24 points input, including 16 high-speed counter, frequency up to 120K, 16-point output, including 4-axis stepping Or the servo output is integrated inside, the output frequency can reach 120K, which makes the application very convenient and the wiring is simple. The programming software WinProladder is known as the master of ladder diagrams. It is easy to learn and use and powerful. Editing, monitoring, debugging and Other operations are very convenient. The buttons and mouse are used together with the online instant command function query and operation guide, which makes the editing and input efficiency double.
Contact distribution: Take the Z-phase signal of each axis servo motor as the origin switch, which should be tapped at several high-speed input points, use the interrupt to carry out the machine origin return, and the other limit switches such as limit switch, operation switch and liquid level detection can be used. Access in order. The X, Y, Z three-axis servo motor is connected to the front three-axis servo output point, and the spindle high and low speed, cooling, alarm, etc. are connected to the remaining output points.
The X, Y, and Z3 axis servo systems all use the same, and the ES series all-digital AC servo drive 0040E-CBCEE-02, and the 60 series small inertia servo motor 60CB040C-2DE6E. The servo system has relatively complete functions, such as energy braking, electronic gear, automatic acceleration and deceleration, etc. It has a variety of pulse train inputs, and the protection functions are relatively complete, including undervoltage, overvoltage, overcurrent, overload, stall, stall. , position error, encoder abnormality, etc. In this device, it is connected to the PLC according to the open collector drive mode. The highest pulse input frequency is 200K, and the servo ON and Z phase signals are also connected.
The inverter adopts Fuling's DZB70B0015L2A, the specification is single-phase 1500W, 400Hz, and there are multiple paces for editing. Since the speed is not changed frequently during normal use, the speed adjustment setting is not taken out. It is only adjusted on the operation panel of the inverter. Two speeds are set, high speed is used for machining, and low speed is used for tool setting. Adjust the relevant parameters to match the spindle, such as the fundamental frequency, base voltage, operating frequency upper limit, carrier frequency, etc., and change the corresponding jumper.
The main shaft is not in the traditional way, but according to the processing needs, the electric spindle used in the engraving machine is used. The ADX80-24Z/1 type of Anyang Lebitai has small volume, low noise and only 80mm in diameter, which makes the whole headstock easy. The overall sealing can effectively prevent the debris in the processing from splashing onto the screw and the guide rail of the Z-axis, and also make the appearance of the spindle head look beautiful. Its maximum speed is 24,000 rpm, which gives a suitable margin range for normal operating speeds of 6000-14000 rpm.
The man-machine interface adopts the man-machine electronic general-purpose programmable text display MD204L, which can monitor and modify the value and status of the PLC internal register or relay in the form of text or indicator light.
Third, software design
The flow chart of the machine tool is shown in Figure 2. After the power is turned on, it is first checked whether the manual switch is valid. If the manual switch is valid, the manual operation is performed by each manual control switch. If the manual switch is invalid, the origin return procedure is started, and each axis returns to the machine origin. First, return to the Z axis and then return to the other two axes. When all the axes are restored to the original point, the next step can be performed. If the tool, fixture and workpiece program are not changed, it can be reset to the machining preparation state without tool setting. If the tool is required, open the tool setting switch to start the tool setting program. The 3 axes are respectively set to the tool, that is, the workpiece origin is found. Use the manual axes to move the switch to move each axis quickly and fast, so that the three faces of the workpiece touch the tool rotating at a low speed, just hit it. After the correct, press the tool to confirm OK, then input the tool compensation, after the program processing, the workpiece origin is formed, that is, programming 0 points. According to the 0 point, the tool path is calculated according to the drawing, so that the operator can clear the mind and edit the operation. simple. The operator edits the user program, and can edit the tool path, which is the coordinate of each axis movement, as well as the movement speed, the number of cycles during cycle processing, and so on. After programming the program or using the current program, reset to the ready state: each axis moves to the initial position - a suitable position, when loading and unloading the workpiece is convenient, when the tool is not easy to touch, the workpiece is loaded, and the machining can be started by pressing the spindle. When the operation is started, the coolant is turned on, and each axis moves according to the programmed coordinates. When the machining is finished, the machine is reset, that is, each axis moves to the initial position, the spindle stops, and the cooling is turned off. At this time, the workpiece can be removed and the machining process can be completed.
figure 2
The processing flow chart of the workpiece is shown in Figure 3. Taking the Q7 product as an example, the last time the tire tool is clamped with 15 workpieces, then there are 30 flat blind holes of φ3.7, which need to be machined. The tool uses 2 blades of φ3.7. Tungsten steel end mill, drilling, drilling depth 1.65mm. In the preparatory state, the positioning of the tire is fixed against the positioning on the workbench. After starting, the spindle rotates. When the spindle is about to reach the rated speed, the X and Y axes are simultaneously operated to the first processing station, which is the first hole. The coordinate values ​​of the X and Y workpieces, when the coolant is opened and the Z axis is quickly lowered to the processing area, that is, the end face of the milling cutter is about to touch the workpiece processing surface, and the drilling process is started quickly with a slow working speed. When the machining depth reaches the set depth (1.65mm), the Z-axis drives the milling cutter to lift up quickly. The height of the lifting is that the end face of the milling cutter can not touch the workpiece and the tire in the horizontal direction. After the counter is incremented by 1, the program performs a comparison operation to determine whether the machining is completed. If not, the X and Y axes continue to run to the next machining station, and the Z-axis lowering machining operation is repeated. If the processing is finished, the output counter is incremented, the spindle is stopped, the coolant is turned off, and a 5s sound and light signal is sent to remind the operator that each axis moves to the initial position: Z axis to the upper end; X axis to the left end; Y axis To the outside. After the tire is removed, one machining cycle is completed, and the tire is loaded and the next round of machining is started.
image 3
Fourth, some important electrical measures
1. Install the leakage circuit breaker in the main circuit and install the appropriate circuit breaker in the corresponding circuit.
2. A power supply filter is added to the power supply of the PLC and servo system.
3. Each DC relay coil is connected to the anti-peak diode, and the AC contactor coil is connected to the RC absorption circuit.
4. Lubrication and spindle cooling are all equipped with low level alarms.
5. Use shielded wires for servo control lines and human-machine interface communication lines, and keep them away from the power cables.
6. Route the wires inside the chain, use a flexible flexible cable, and increase the bending radius of the chain.
7. The inverter maintains a certain distance from the PLC and servo drive.
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