Application of frequency converter in CNC engraving machine

At present, engraving machines have gradually become an essential professional tool for production in various industries. With the development and application of CNC numerical control technology combined with high-performance inverter controllers and servo drive equipment in various production industries, CNC engraving machines have increasingly become the mainstream configuration of the engraving industry today. . Most of the main drive systems of CNC engraving machine tools use infinitely variable speed. Inorganic variable speed systems mainly include frequency conversion spindle system and servo spindle system. Due to the high cost performance of frequency converters, frequency converters are widely used in machine tools. The spindle system is an important component of the CNC engraving machine, and its performance has a crucial impact on the performance of the CNC engraving machine. As the heart of the spindle system, the frequency converter is an indispensable key component. The following introduces the application of Dolycon CT100E Variable Frequency Drive in the spindle drag system of CNC engraving machine.

Introduction to the control principle of CNC engraving machine

CNC engraving machine control system composition
The CNC engraving machine control system is mainly composed of three parts: CNC numerical control system, spindle positioning system and spindle rotation system. The functions of each part are as follows:

CNC numerical control system: The design and typesetting are carried out through the special engraving software configured in the computer, and the information of design and typesetting is transmitted to the controller of the engraving machine through the computer, and then the controller converts the information into a stepper motor or servo drive. The pulse signal of the motor, the positioning system completes the design and layout pattern model by receiving the pulse signal to complete the positioning.

Servo positioning system: The three-axis positioning can be completed by using three axes that are perpendicular to each other in the three-dimensional space. Therefore, the three sets of servo positioning systems respectively receive the pulse signals from the CNC numerical control system to carry out the engraving and positioning of the X, Y, and Z axes. , you can complete any pattern model in three-dimensional space.

Spindle processing system: The servo positioning system completes the pattern and model setting, and the corresponding engraving work needs to be completed at the corresponding fixed-sample position to complete the engraving items typed by the CNC numerical control system. Therefore, the high-speed rotation of the spindle is required to complete the engraving work. Different engraving materials and differentiated engraving precision also require the rotating system to have a flexible speed regulation function.

The control requirements of the spindle processing system of the engraving machine to the frequency converter

The performance requirements of the system to the Frequency Inverter
(1) The speed regulation range is wide, and the running speed is generally 0~24000r/min.
(2) The speed fluctuation is small in the full speed range;
(3) The low speed torque is large, which can ensure low speed cutting;
(4) The acceleration and deceleration time should be as short as possible.

The functional requirements of the system to the VFD
(1) The control mode is selected as V/F control to meet the control requirements of wide speed regulation range, good magnetic weakening performance and good driving stability
(2) Terminals control start and stop to realize remote start and stop and forward and reverse switching;
(3) The running frequency is set by the analog quantity, and the voltage output of 0～10VDC can be accepted;
(4) The speed regulation range is 0~24000r/min, and the operating frequency of the inverter is 0~400Hz (secondary high-speed motor);
(5) The acceleration and deceleration time is short, generally 3~5s. Because the running speed is relatively high, a frequency converter with a braking unit is required;
(6) The fault output signal is required to ensure that the system protects in time when the spindle fails; the fault reset signal is required to ensure that the fault can be reset and restarted remotely.

Dolycon CT100E Frequency Inverter Solution

The start-stop method of the frequency converter is terminal start-stop, that is, the forward and reverse start-stop and forward-reverse switching of the spindle motor are realized through the digital input terminal of the CNC numerical control system to the frequency converter DI1/DI2 command. Taking into account that the system may need to brake quickly to avoid mechanical damage in case of emergency failure, the emergency stop function is realized through DI3 as the terminal. The inverter fault signal is output through the programmable relay terminal, and the system receives the fault signal when the inverter fails to avoid mechanical damage caused by malfunction. After the fault is cleared, the fault lock can be released through the reset terminal. The speed regulation mode of the system is digital-to-analog conversion of the numerical control system. The frequency converter receives the 0~10V voltage signal given by the numerical control system as the frequency signal, and automatically adjusts the engraving speed.

Since the CNC engraving machine needs to start and stop suddenly, this process will generate a large energy feedback, so it is necessary to install a braking resistor. CT100E Frequency Inverter below 45kw have built-in braking unit, and the braking resistor can be directly connected.

CT100E Frequency Inverter technical description

Shenzhen Dolycon Technology Co., LTD CT100E Frequency Inverter takes the DSP control system as the platform, adopts the domestic technology-leading non-PG vector control technology, and cooperates with various protection methods, which can be applied to asynchronous motors and provide excellent driving performance. The product has greatly improved the ease of use and environmental adaptability of customers in terms of air duct design, hardware configuration, and software functions.

Technical Features

◆ Accurate motor parameter self-learning: accurate rotating or stationary motor parameter self-learning, easy debugging, simple operation, providing higher control accuracy and response speed
◆Vectorized V/F control: automatic stator voltage drop compensation and slip compensation to ensure excellent low-frequency large torque and torque dynamic response in VF control mode
◆ Software current limiting and voltage limiting function: good voltage and current limiting, effective limiting of key control parameters to reduce the fault risk of the inverter
◆ A variety of braking modes: provide a variety of braking modes to ensure that the system stops stably, accurately and quickly
◆ Strong environmental adaptability: higher over-temperature point of the whole machine, independent air duct design, thickened three-proof paint treatment, more suitable for occasions where there are many metal powders and heavy oil pollution in the machine tool industry
◆ Speed tracking restart function: realize the smooth start of the rotating motor without impact
◆ Automatic voltage adjustment function: when the grid voltage changes, it can automatically keep the output voltage constant.
◆ Comprehensive fault protection: over current, over voltage, under voltage, over temperature, phase loss, overload and other protection functions

The spindle drive part of the CNC engraving machine seems to be simple, but the actual control has a severe test on the performance and stability of the inverter due to the requirements of high frequency speed, high low frequency output, and harsh operating environment. CT100E Frequency Inverter is a high-performance Open Loop Vector VFD newly developed by Shenzhen Dolycon Technology Co., LTD. Its excellent performance and rich functions make it very well used in CNC engraving machines.