Development of 27-axis Large-scale NC Longmen Drilling Machine

At present, due to the rapid development of power plant equipment, seawater desalination, chemical equipment and air-conditioning industries, the plates in these industries need to be drilled and expanded to thousands or even tens of thousands of holes. The hole tolerances and hole spacing are quite high. Drilling machines are difficult to achieve such high requirements in terms of speed, accuracy and efficiency (hole tolerance is ±0.05 mm). The United States, Japan and other developed countries have all developed multi-axis gantry drilling machines, while China only has two-axis CNC swarf drilling machines in Shenyang. In order to meet the needs of the power station boiler manufacturing, the plant imported several CNC gantry drilling machines, each up to several million dollars. In order to fill the gaps in the domestic market, Shanghai Precision Machinery Manufacturing Co., Ltd. organized its efforts to develop a successful 27-axis large-scale numerical control gantry drilling machine. Its precision and efficiency have reached the world's advanced level. The machine can be extended to the two ends to make 5, 7 or 13 axes, or it can be extended to the high-end 35 axis (only made in the United States).

1, ZKM27 technical parameters

Drill shaft total number 27

Axis Machining Range Positioning for holes below φ30, drilling, expanding, reaming

Table size 7500 × 5000 mm

The largest processing area 7000 × 4500 mm

X axis stroke 7000 mm

Z axis stroke 630 mm

Y axis stroke 400 mm

X-axis servo motor power, torque 14 kW 75 N•m

Z-axis servo motor power, torque 11 kW 75 N•m

Y-axis servo motor power 5. 7 kW

Machine power 150 kW

CNC system FANUC-18 I

2, structural features

2. 1 X-axis travel

X-axis drive, by FANUC α50 servo motor, increase the torque by 1:10 reducer, drive the ball nut to rotate, so that cross carriage and gantry frame move in X direction. Due to the large size and heavy weight of the workpiece, the large-scale data portal drilling machine is fixed on the table and the gantry is movable.

The two slides are supported by four sets of high-precision linear guides. The span of the gantry is 6800mm. The gantry motion is strictly synchronized by the two servo motors. The ball screw is imported from Germany. It has a double-nut type internal circulation. The length of the screw is 9500mm, and the thread length is 7870mm. This ball screw processing, heat treatment, grinding are quite difficult. The nut rotates and the screw is fixed, which greatly reduces the required moment of inertia and torque of the servo motor, and also reduces the precision requirements for supporting the ball screw bearing. The X-axis travel is detected by a high-precision position encoder mounted on the servomotor shaft. The CNC system performs pitch error compensation on the X axis to ensure that the drilling accuracy is ≤ ±0.05 mm.

Figure 1 machine outline

2. 2 Z axis travel

The up and down stroke of the drill consists of two parts. One is that the horizontal whole moves up and down. This is done by two α50 servo motors. The second is the up and down movement of the spindle box and the drill bit, which is accomplished through the hydraulic cylinder driving the spindle box. 27 axes, 27 solenoid valves, each solenoid valve controls one cylinder up and down. When drilling is required, the numerical control program controls the corresponding solenoid valve to make the cylinder with the spindle box, the drill moves downwards, so that the drill hole to be drilled protrudes, and then drives under the Z-direction servo motor and moves downwards horizontally to complete the drilling. action. If the drill bit is passivated, broken, and the drilling force is doubled, it will automatically alarm and stop horizontally to reduce and ensure the drill bit is safe and reliable. Horizontal up and down from the left and right two α50Nm servo motor, through the MF150SL1 1: 10 reducer, so that ball screw DF1 - 8010 - 4 rotation, horizontal balance up and down. The FANUC18i makes the two motors equal in speed and strictly synchronous. Because of the imbalance of horizontal and drill cutting load, the lateral left and right sides have different numbers of drills, and the degree of wear of the drill bit is different. For this reason, there are three balanced cylinders designed for the left, center and right sides of the transverse direction to balance the load at any time. .

2. 3 Y-axis travel

The Y-axis movement is horizontally moving left and right on the cross slide. Y-axis movement is also driven by the servo motor, reducer, ball screw rotation, so that the lateral movement. The horizontal Y-direction movement is supported by three straight rails on the left and right. The overall Y-direction rigidity is good, and the stroke is short (400mm). As can be seen from the figure, only the servo motor is installed on the left side, and only the support rail is on the Y-direction of the right side. After a large number of workpiece cutting performance tests, the large-span gantry moves smoothly, with high positioning accuracy and no flutter.

2. 4 bit rotary motion

27 bits are divided into 4 groups of 7 + 7 + 7 + 6 = 27. Each group is shifted by a Y180L - A22kW motor through a gearbox to drive a set of bits. The speed of the bit is controlled by the gearbox handle. Medium and low multi-speed, to meet the needs of drilling, expansion, and reaming.

The machine also has a suspended air blowing system and a cooling system.

The machine tool applied for a number of national patents and reported the scientific and technological achievement award.

3, CNC system and electrical control

All movements of the ZKM27 machine tool are controlled by the FANUC18 i-MB CNC system. For now, the CNC system is an ideal advanced CNC system. It has many special features to meet the requirements of the ZKM27 machine. From the perspective of its A-I advance predictive control function, the ZKM27 has 27 drill shafts that require high-speed continuous control. It is necessary to compile multiple machining program segments to control the operation. If the previous machining method is used, it will affect the processing cycle.

Figure 2 machine layout

It is able to read a plurality of machining program segments in advance, achieving the best acceleration/deceleration control of the drilling speed, and effectively improving the machining speed and accuracy of the machine tool. In addition, it has a coordinate system rotation function. When the workpiece contains some graphics that are rotated from a typical shape, a subroutine of the shape can be programmed. After the rotation, it is called to make the programming of the workpiece more convenient. More flexibility. It also has a memory-type pitch error compensation function that compensates for lead screw pitch errors or mechanical system errors. The compensation data is stored in CNC memory in the form of parameters, which further improves the machine's positioning accuracy. In addition, we can use user macro/macro actuators to compile various machining programs to make some complex machining programs easy to understand.

The more important point is that it has two sets of two-axis synchronization function, especially its servo HRV control, through the rotation of the smooth servo motor, high-precision current detection, high-response and high-resolution pulse encoder and other hardware and The organic combination of servo HRV control realizes high-speed and high-precision feed control, making the two axes of ZKM27 more ideal for synchronous motion.

The electrical system of the machine tool adopts advanced design concepts and design techniques, fully integrates the principle of ergonomics, and extensively applies modern design methods and tools such as CAD to make the machine performance reliable, easy to operate, and freely controlled.

The ZKM27 uses a 10.4 inch color LCD liquid crystal display with a clear picture. The operator panel is located directly in front of the machine. The operator panel adopts FANUC's standard panel with graphic symbols and Chinese notes. The feed speed switch is set on the panel. The operator can correct the cutting parameters according to the actual conditions during the cutting process in order to obtain the best cutting results.

Adjustment parameters are:

Fast feed correction amount: F0, 10, 50, 100% 4 kinds.

Work feed corrections: 0, 1, 2, 20, 16%.

Operation box as shown in Figure 3

Large-scale numerical control equipment is widely used in a variety of mechanical processing fields, in order to meet the needs of processing some large-size, high-precision parts. The use of some large gantry type and bridge type numerical control equipment, in order to avoid damage to the gantry or bridge caused by different torques during acceleration and deceleration, synchronous control of two-axis drive is often used. The so-called synchronous control is to use a coordinate movement instruction to drive a main motor to drive a driven motor to run at the same time. Through the detection of the movement of these two motors, the displacement deviation is fed back to the CNC system to obtain synchronous error compensation. The displacement between the motors is controlled within a very small range. ZKM27 is a gantry-type large-scale mechanical equipment. The machine tool adopts two sets of synchronously controlled motion axes, namely the X-axis and Z-axis, and adopts FANUC's α50 i servo motor to drive two ball screw rods. Synchronous axis control. After the machine tool is debugged, the synchronous motor runs smoothly with good dynamic quality and control accuracy.

Fig. 3 Machine operation box

In large-scale numerical control equipment, due to its large power, the current changes abruptly when it is turned on and off, and it is easy to produce various kinds of interference. ZKM27's equipment uses a lot of anti-interference measures. In particular, attention is paid to the input interference from the power grid, and certain measures are taken to protect the abnormal input. We use a separate power supply for this equipment to prevent the use of other equipment and cause interference within the power grid. In addition, we also use a surge absorber to absorb the action of electrical components from the device and generate interference, while also being able to absorb additional noise information signals from the input system. For some of the more powerful motors, star-delta startup is used to reduce the starting current. For commonly used motors, we use line-to-line protection measures to effectively suppress interference from line to line. In the cable distribution, we strictly controlled the mixed assembly of signal lines and power lines to minimize signal crosstalk between them. The connection between FANUC servo amplifier and the system adopts the fiber (FSSB) connection, which greatly reduces the interference of the system to the inter-servo signal.

The operation of this machine is divided into manual and automatic operation methods. The commissioning of the equipment and the start-up of peripheral equipment (cooling, hydraulics, etc.) can be performed manually, while the automatic operation of the machine tool is only performed by the program in the automatic mode. 27 drill shaft debugging can be implemented by MD I method. The manual operation and the automatic operation are mutually interlocked, and when the automatic operation is performed, the manual operation is invalid, so that it is possible to avoid the damage of the workpiece due to the operation mistake.

In addition to X and Z synchronous axes linkage, the machine tool also has Y-axis movement to the left and right, 27 deep-hole drill shafts moving up and down, position detection during movement, and deep-hole drill bit wear detection and other feedback signals. Timely, correct. All this is achieved by the PLC. FANUC18i system uses the SB7 version of the PLC to prepare. Its operation speed is extremely fast, can reach 0.03μ sec / step, and the capacity can reach 64000 steps, so can fully meet the movement of ZKM27 machine tool and require high demand.

The numerical control device has many functions and can display various working conditions of the machine tool, such as the destination position of each coordinate axis, the current position, the actual feed speed, various action signals of the machine tool, and the like. Once a fault occurs in the process, the machine automatically shuts down and displays the contents of the fault. The operator can immediately analyze the cause and eliminate the fault. This brings great convenience to the maintenance work, reduces the downtime of the equipment, and improves the utilization of the machine tool. rate.

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