Application of stepping motor in WEDM
2.1.1 high speed wire cutting mechanism
The high-speed wire-traveling mechanism is mainly composed of upper and lower carriage plates, gear pairs, screw pairs, reversing devices and insulating parts. The high-speed wire-feeding mechanism is mainly used to drive the wire to move at a certain linear velocity, and the electrode wire is neatly arranged on the storage tube.
2.1.2 Movement of the wire electrode The wire frame guide wheel mechanism and the wire-traveling mechanism constitute the movement system of the wire electrode. The main function of the wire frame is in electricity.
When the filament moves at a given linear velocity, the electrode wire is supported to maintain a certain geometric angle between the working portion of the electrode wire and the plane of the work platform. The guide wheel is located at the end of the cantilever of the wire frame, and the wire frame supports the wire by the guide wheel. According to the function, the wire frame can be divided into three types: fixed type, lift 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 a working medium having a certain insulating property to the working fluid in the WEDM process to cool the electrode wire and the workpiece, and to eliminate the electrolytic corrosion product, so as to ensure the spark discharge continues. The working fluid system of the general wire cutting machine tool includes: a working liquid tank, a working fluid pump, a flow control valve, an inlet pipe, a liquid return pipe and a filter net. The cleanliness of the working fluid plays an important role in the stability of the processing site.
2.1.4 EDM wire cutting pulse power supply
The electric discharge wire cutting pulse power supply is usually called high frequency power supply. It is the main component of the CNC electric discharge wire cutting machine tool and one of the main factors affecting the wire cutting process index. The basic component of the wire-cut pulse power supply line cutting pulse power supply is composed of pulse generator, push stage, power amplifier and DC power supply.
2.2 The composition of the coordinate workbench
The coordinate workbench is mainly composed of four parts: the carriage, the guide rail, the screw movement pair, the gear pair or the worm gear transmission pair.
Drag board
The carriage is mainly composed of a lower carriage, a middle carriage, an upper carriage and a workbench. Usually, the lower carriage is fixedly connected with the bed; the middle carriage is placed on the lower carriage, the movement direction is the coordinate Y direction; the upper carriage is placed on the middle carriage, the movement direction is the coordinate X direction; the worktable passes the insulator Connected to 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. Guide rail
The longitudinal and horizontal carriages of the coordinate table are reciprocated along the guide rails. Therefore, there is a high requirement for the accuracy, rigidity and wear resistance of the guide rail. In addition, the guide rails should make the carriage movement flexible and stable. Rolling guides are often used for wire cutting machines. Because the rolling guide can reduce the frictional resistance between the guide rails, it is convenient for the worktable to achieve precise and slight movement, and the lubrication method is also simple. The disadvantage is that it is not easy to maintain between the contact surfaces.
Oil film, anti-vibration ability is poor. The rolling guide has several forms such as a ball guide, a roller guide and a needle guide.
3. Screw drive pair
The function of the screw drive pair is to change the rotary motion of the drive motor into a linear displacement motion of the carriage. In order to make the lead screw drive accurate, the lead screw and nut should be accurate, and should be guaranteed to be 6 or higher.
4. Gear pair
The drive between the stepper motor and the lead screw is usually realized by a gear pair. Due to the flank clearance, the gap between the shaft and the bearing, and the elastic deformation in the drive chain, the drive lost motion occurs when the drive gear on the stepper motor spindle changes the drive direction. In order to reduce and eliminate the gear transmission lost motion, the following measures should be taken:
(1) Use as few gear reduction stages as possible to reduce the error of gear transmission accuracy from the structure.
(2) The adjustable structure of the gear center distance can be realized by changing the fixed position of the stepping motor.
(3) The driven gear or the intermediate wheel is axially divided into two wheels. Two-tooth profile should be ensured during assembly
They are respectively in contact with the two sides of the active tooth profile, and when the stepping motor changes the direction of rotation, the screw can be quickly reflected accordingly.
