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1. Brief description

The following explains the application of stepper motor in wire EDM machine tool. WEDM machine is mainly composed of coordinate table, high-speed wire-feeding mechanism, bed, working fluid system, pulse power supply and controller. Among them, the X and Y coordinate table is used to clamp the workpiece to be processed. The X axis and Y axis send out the feed signal by the controller, respectively control the two stepper motors to run the predetermined trajectory.

2.1.1 High-speed wire travel mechanism

The high-speed wire feeding mechanism is mainly composed of the upper and lower carriages of the wire storage cylinder assembly, the gear pair, the screw pair, the reversing device and the insulating parts. The high-speed wire feeding mechanism is mainly used to drive the electrode wire to move at a certain linear speed, and arrange the electrode wire neatly on the wire storage drum.

2.1.2 Motion system of electrode wire The wire frame guide wheel mechanism and the wire travel mechanism constitute the motion system of the electrode wire. The main function of the wire frame is to

When the electrode wire moves at a given linear speed, it supports the electrode wire and keeps the working part of the electrode wire at a certain geometric angle with the plane of the workbench. The guide wheel is located at the end of the cantilever of the wire frame, and the wire frame supports the electrode wire through the guide wheel. According to the function, the wire frame can be divided into three types: fixed type, lifting type and offset type; according to the structure, it can be divided into cantilever type and gantry type.

2.1.3 Working fluid circulation and filtration system

The working fluid system is used to supply working medium with certain insulating properties—working fluid during the WEDM process, to cool the electrode wire and the workpiece, and remove the electro-corrosion products, etc., so as to ensure the continuous spark discharge. The working fluid system of general wire cutting machine tools includes: working fluid tank, working fluid pump, flow control valve, liquid inlet pipe, liquid return pipe and filter screen, etc. Among them, the cleanliness of the working fluid plays an important role in the stability of the processing.

2.1.4 WEDM pulse power supply

Wire EDM pulse power supply is usually called high frequency power supply. It is the main component of CNC wire EDM machine tools and one of the main factors affecting the process indicators of wire EDM. The basic composition of the wire cutting pulse power supply The wire cutting pulse power supply is composed of four parts: the pulse generator, the push stage, the power amplifier and the DC power supply.

2.2 Composition of Coordinate Workbench

The coordinate table is mainly composed of four parts: carriage, guide rail, screw motion pair, gear pair or worm gear transmission pair.

1. Drag board

The carriage is mainly composed of four parts: the lower carriage, the middle carriage, the upper carriage and the workbench. Usually the lower carriage is fixedly connected to the bed; the middle carriage is placed on the lower carriage, and the movement direction is the coordinate Y direction; the upper carriage is placed on the middle carriage, and the movement direction is the coordinate X direction; the worktable passes through the insulator Connect with the upper carriage. Among them, one end of the upper and middle carriages is in the form of a cantilever to place the drag motor.

2. Rails

The vertical and horizontal carriages of the coordinate table move back and forth along the guide rails. Therefore, there are higher requirements for the accuracy, rigidity and wear resistance of the guide rail. In addition, the guide rail should make the carriage move flexibly and smoothly. Wire cutting machine tools often use rolling guides. Because the rolling guide rail can reduce the frictional resistance between the guide rails, it is convenient for the table to achieve precise and micro movement, and the lubrication method is also simple. The disadvantage is that the contact surfaces are not easy to maintain

Oil film, poor vibration resistance. There are several forms of rolling guides, such as ball guides, roller guides and needle guides.

3. Screw drive pair

The function of the screw drive pair is to convert the rotational motion of the drive motor into the linear displacement motion of the carriage. To make the lead screw pair transmission accurate, the lead screw and nut should be accurate, and the accuracy should be guaranteed to be grade 6 or higher.

4. Gear pair

The transmission between the stepping motor and the lead screw is usually realized by a gear pair. Due to the influence of the backlash, the clearance between the shaft and the bearing, and the elastic deformation in the transmission chain, when the driving gear on the main shaft of the stepper motor changes the transmission direction, there will be a transmission idling. In order to reduce and eliminate the backlash of the gear drive, the following measures should be taken:

(1) Use as few gear reduction stages as possible, and strive to reduce the error of gear transmission accuracy from the structure.

(2) The center distance of the gear pair can be adjusted by changing the fixed position of the stepping motor.

(3) Divide the driven gear or intermediate wheel into the form of double wheels along the axial direction. The two-tooth profile should be guaranteed during assembly