At present, carving machines have gradually become essential professional tools for various industries. With the development and application of CNC technology combined with high-performance variable frequency controllers and servo drive equipment in various production industries, CNC carving machines have become the mainstream configuration in today's carving industry. The main transmission system of CNC engraving machine tools mostly adopts stepless variable speed. Inorganic variable speed systems mainly include two types: variable frequency spindle systems and servo spindle systems. Due to the high cost-effectiveness of variable frequency drives, they are widely used in machine tools. The spindle system is an important component of a CNC engraving machine, and its performance has a crucial impact on the overall performance of the CNC engraving machine. As the heart of the spindle system, the frequency converter is an indispensable key component. This article introduces the application of Dongli Kechuang CT100 series frequency converter in the spindle drive system of CNC engraving machine.
Introduction to the Electrical Control Principle of CNC Carving Machine
Composition of the electrical control system for CNC engraving machine
The electrical control system of a CNC engraving machine mainly consists 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: Pattern design and layout are carried out through specialized carving software configured in the computer. The design and layout information is transmitted to the carving machine controller through the computer, and then the controller converts this information into pulse signals that can drive stepper motors or servo motors. The positioning system completes the design and layout pattern model by receiving the pulse signals for positioning.
Servo positioning system: Three axes perpendicular to each other can be used to complete three-axis positioning in three-dimensional space. Therefore, the three sets of servo positioning systems receive pulse signals from the CNC numerical control system to perform carving and tool positioning on the X, Y, and Z axes, thus completing any sample model in three-dimensional space.
Spindle machining system: The servo positioning system completes the pattern model sampling, and the corresponding carving work needs to be completed at the corresponding sampling position to complete the CNC numerical control system layout of the carved items. Therefore, high-speed rotation of the spindle is required to complete the carving work. Different carving materials and differentiated carving accuracy require the rotating system to have flexible speed regulation function.
Control requirements of frequency converter for carving machine spindle processing system
Performance requirements of the system for frequency converters
(1) The speed range is wide, and the operating speed is generally between 0-24000r/min.
(2) Small speed fluctuations within the entire speed range;
(3) Low speed torque is large, which can ensure low-speed cutting;
(4) Try to keep the acceleration and deceleration time as short as possible.
Functional requirements of the system for the frequency converter
(1) The control mode is selected as V/F control to adapt to the control requirements of wide speed range, weak magnetic properties, good driving stability, etc
(2) Terminal control start stop, realizing remote start stop and forward/reverse switching;
(3) Analog setting operating frequency, capable of accepting 0-10VDC voltage output;
(4) The speed range is 0-2400r/min, and the operating frequency of the frequency converter is converted to 0-400Hz (secondary high-speed motor);
(5) The acceleration and deceleration time is short, usually within 3-5 seconds. Due to the high operating speed, a frequency converter with a braking unit is required;
(6) Need fault output signal to ensure timely protection of the system in case of spindle failure; A fault reset signal is required to ensure remote reset and restart when the fault is resolved.
The start stop method of the frequency converter is terminal start stop, which means that the digital input terminals of the CNC numerical control system are used to give the DI1/DI2 commands to the frequency converter to achieve the start stop and forward/reverse switching of the spindle motor. Considering that rapid braking may be required in case of emergency system failure to avoid mechanical damage, the emergency stop function is implemented through DI3 as the terminal. The fault signal of the frequency converter is output through the programmable relay terminal, and the system receives the fault signal to avoid mechanical damage caused by misoperation when the frequency converter fails. After the fault is cleared, the fault lock can be released through the reset terminal. The system speed regulation method is digital to analog conversion of the numerical control system. The frequency converter receives a 0-10V voltage signal from the numerical control system as a frequency signal and automatically adjusts the carving speed.
Technical Features
◆ Accurate motor parameter self-learning: Accurate self-learning of rotating or stationary motor parameters, easy debugging, simple operation, providing higher control accuracy and response speed
Vectorized V/F control: automatic stator voltage drop compensation and slip compensation, ensuring excellent low-frequency high torque and torque dynamic response even in VF control mode
◆ Software current and voltage limiting function: Good voltage and current limiting, effectively limiting key control parameters to reduce the risk of inverter failure
◆ Multiple braking modes: Provides multiple braking modes to ensure stable, accurate, and fast system shutdown
◆ Strong environmental adaptability: high overall overheating point, independent air duct design, thickened three proof paint treatment, more suitable for occasions with high metal powder and heavy oil pollution in the machine tool industry
◆ Speed tracking restart function: achieve smooth start of rotating motors without impact
◆ Automatic voltage adjustment function: When the grid voltage changes, it can automatically maintain a constant output voltage
Comprehensive fault protection: overcurrent, overvoltage, undervoltage, overtemperature, phase loss, overload and other protection functions
Conclusion
The spindle drive part of a CNC engraving machine may seem simple, but in reality, the performance and stability of the frequency converter are rigorously tested due to high high-frequency speed, large low-frequency output, and harsh operating environments.