Error Compensation for Backlash and Pitch Error of Screw Gear of Numerical Control Equipment

China Man wide gland S pitch error Qiaopu compensation numerical control equipment screw gear table 1 table 2 measuring point position mm correction value mm position error (measured) mm position error after correction mm average error mm compensation value compensation data average positive direction negative direction The positive direction and the negative direction ABCDEF=D-CG=E-CH=(F+G)/21=H/X As the use time of numerical control equipment increases, the lead screw, gear gap and pitch error will change greatly. In order to maintain the processing accuracy of CNC equipment, regular accuracy testing of the equipment and compensation of the backlash and pitch error of the CNC equipment have become an important task to strengthen the later management of the equipment.

0-MD as an example, talk about the compensation method for backlash and pitch error.

1. The parameters and descriptions related to compensation and the setting of the initial backlash compensation direction are the positive direction, and 1 is the negative direction.

PML1, PML2: Pitch error compensation magnification (used for all axes), the true value is shown in Table 1. BKW: Backlash compensation amount, the distance between the two set points when the setting range is compensated, that is, the pitch error compensation point The minimum value of the interval is 8000mi/nn (maximum feedrate compensation stroke=compensation interval x127. That is, each compensation point parameter, the setting value is ±7 (error value pm/compensation magnification).

The last digits X, Y, Z, and 4 of the parameter name in the number comparison table respectively represent each numerical control axis D 2. The measurement method and the determination of the compensation data are measured with a dial indicator: the dial indicator base is fixed on the bed, The probe refers to the end face of the shaft to be measured, moves the shaft to be measured, makes the dial indicator zero, and the position display of the control system is also cleared. Use jog to move the measured axis in the opposite direction until the dial indicator pointer changes. At this time, the displacement amount displayed by the control system minus the pointer change amount is the lead screw gear clearance of the shaft.

Measured with a dual-frequency laser interferometer: The absolute value of the difference between the forward measurement data curve and the reverse measurement curve at the commutation point is the screw gear gap of the shaft.

When the gap value reaches a certain value, that is, the finishing equipment reaches 10pn, and the roughing equipment reaches 50mm, please check whether the screw connection nut is loose.

Pitch error compensation parameter value The methods usually used to measure the pitch error include block gauge measurement, step gauge measurement, optical reader measurement method, and dual-frequency laser interferometer measurement method. Each unit can be selected according to the actual situation.

It needs to be explained that when the power supply voltage and frequency are constant, the operating performance of the asynchronous motor changes with the size of the load. Therefore, changing the load reasonably to improve the performance index of the motor cannot be ignored. This is the rationalization and energy saving of production, which is another aspect that complements the rationalization and energy saving of electricity. At the same time, in the development of production and market competition, enterprises will inevitably involve adjustment of product structure, production process innovation, optimization of operation methods, transformation or updating of mechanical equipment, etc., which will cause load changes and may cause new non-economic operations. Therefore, the economic operation and management of electric motors is a daily and long-term task coexisting with the life of the enterprise. W01.10-10 [Edit Wu Siming] □ Zhou Jiajian excitation generator, given speed nil voltage negative feedback current positive feedback -mIV (current differential feedback number for planers produced before the 1960s, most of the electric drive system adopts alternating magnetic expansion The speed control system of DC generator and DC motor has complicated electrical control parts and many components, which have been aging and are mostly obsolete products. It has brought a lot of trouble to maintenance. In recent years, due to the high-power thyristor rectifier device The application provides the possibility for the technical transformation of these old planer planers, but the SCR rectifier is expensive, and the cost of refitting a planer planer is more than 100,000 yuan. Our factory has two BQ2020 type (planing table length 6m) This is the case for the planer. We decided to make technical reforms on the electrical control part of the planer ourselves. The specific content is as follows: cancel the cross-magnet expansion unit, and use a low-power controllable voltage-regulating power supply to excite the generator to achieve activation The voltage and speed regulation of the motor, and the feedback control adopts negative speed feedback, which realizes closed-loop control, thus improving the stability of operation and speed regulation range, and greatly simplifies the principle of electrical control.

The limit switch of the planer was changed from the original mechanical switch to the non-contact proximity switch; the old-fashioned DC relay was replaced with a new type of high-reliability relay; the excitation generator was cancelled and replaced with a transistor rectifier; the original control cabinet was deleted All of the large fixed resistors and adjustable resistors are replaced by three potentiometers. The schematic diagram of the original speed control system is as shown. The schematic diagram of the improved speed regulation system is shown in the figure.

After improvement, the control performance of the planer is greatly improved, and the effect is remarkable.

Simplifies the control principle, improves the stability and reliability of operation, and has few failures; the speed control performance is significantly improved, mainly to improve the stability of low-speed operation, and can be used as a guide rail grinder after improvement; due to the cancellation of the cross-magnetic expansion unit And the excitation generator, thus reducing energy consumption and noise (the speed of the amplifier is 3000r/min, and the noise frequency is high).

Through this technical transformation, we have the experience that people thought that to improve the old planer, the generator set must be eliminated and replaced by a high-power controllable rectifier power supply, which can significantly save energy and improve performance. In fact, Not at all. According to measurements, the no-load loss of the unit accounts for 12% to 15% of the rated power, that is, during the planing process, the unit is also under light load most of the time, and the energy consumption is not much in the original speed control system schematic diagram. The DC generator set and the planer drive motor have the same operating conditions, and the structural performance and service life are also matched, so it is completely feasible to retain the generator set. The large-capacity controllable rectifier power supply device is not only expensive, but the control principle is also complicated, and the technical requirements for maintenance electricians are correspondingly high, so it is not necessarily cost-effective. The comprehensive cost of our transformation plan is only about 25,000 yuan, so the technical performance and economic effect are still very good. The planer has been running smoothly for nearly two years. W01.10-12① The measured axis returns to the origin (determine the origin of error compensation). ② Clear the display position data of the measuring instrument (meter) and the control system to zero. ③Compile and run the automatic start-stop cycle program (the function is: after running the compensation interval distance, stop for enough time to read the data, then run, and then stop, the number of cycles is the maximum compensation stroke/compensation gap). Read and record each data. Or use the MDI method to read and record the data every time the interval is compensated for movement. After reaching the maximum stroke, return to measurement and record. Repeated measurement data recording table and processing method (Table 3) 1. Before compensation, record and repeatedly check all the parameters of the system.

Set the following parameters (the general information of the setting method is described) pitch error compensation zero point; pitch error compensation interval.

After shutting down and returning to the machine origin, measurement is performed.

Set the measured pitch error compensation amount and backlash compensation amount.

The machine tool returns to the origin.