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The inverter — a special mechanism that serves as a converter for flexible electric motor controlling. To put it simply, the inverter expands functionality, allowing the spindle to move smoothly at start and finish of the process, provides constant spindle voltage and more. Read more about everything in our article below!
Functions and tasks of an inverter in a CNC machine
Adjusting the spindle speed
The inverter allows flexibility to change the rotation speed of the spindle motor — a necessity when working with different types of materials. For example, cutting metal requires a high rotational speed, while processing soft materials or drilling requires a lower one. Controlling the frequency and voltage on the spindle motor avoids overheating and overloading the equipment.
Smooth start and braking
The inverter ensures a smooth increase and decrease in engine speed. This helps to minimize the mechanical and thermal stress on the machine components, extending their service life. Smooth start-up also reduces shock loads, which is especially important for high-speed machine tools and systems with heavy elements.
Energy saving
The use of frequency converters reduces power losses, as they adapt the power supply depending on the current load on the spindle. In alternating inverter operation, this significantly reduces power consumption.
Engine and system protection
The inverter protects the motor from overloads, overheating, power surges and short circuits. Integrated monitoring and parameter control systems prevent damage to motor windings and other electrical components.
Constant moment feedback and support
Modern inverters can operate with speed and torque feedback, which ensures stable maintenance of the set torque on the motor shaft, even when the load changes. This is especially important for high-precision milling machines and machines working with hard materials.
Multiple engine control
Some inverters can work with multiple motors at once. This is useful if one CNC machine uses multiple spindles or additional drives.
Types of inverters and their features
By connection type
- Single-phase (220 V): Usually used in small and medium-sized machines where the total drive power does not exceed 2.2-3.0 kW. They are connected to a standard household network and are a more economical option.
- Three-phase (380 V): They are used in industrial machines and allow you to connect equipment with high power (from 4 kW and above). They provide more stable operation and withstand heavy loads.
By type of control
- Vector control: Allows you to maintain the exact value of the torque and speed of the engine. This is the most common type of inverters for machines, as it ensures high accuracy and stable operation.
- Scalar control (V/Hz): Provides easier operation without feedback. It is used for simple tasks such as ventilation or pumping units, but is not recommended for machines due to low control accuracy.
By frequency range and power
Inverters for machines usually operate in the frequency range 0-800 Hz. This allows you to vary the speed from 0 to maximum. The power of the inverter must match the power of the motor or be 10-20% higher to ensure a margin.
How to choose an inverter for a CNC machine
Determination of inverter power
Calculate the power of the inverter depending on the spindle power of the machine. For example, if the spindle consumes 5.5 kW, the inverter must be at least 6 kW. The power of the inverter is selected with a margin to avoid overloads.
Selection by type of management
For most CNC machines, it is recommended to use inverters with vector control. They ensure precise maintenance of speed and torque, which is critical for complex machining processes.
Compatible with CNC system
Make sure that the inverter supports the communication interfaces that are used in your machine’s CNC system. The most common interfaces are RS-485, Modbus, and analog inputs/outputs.
Protective functions
Choose an inverter with advanced protection features such as overload protection, overheating protection, automatic restart, and the ability to operate at unstable voltage.
Manufacturer and build quality
Give preference to proven brands (for example, Siemens, Delta, Schneider, ABB). They guarantee high build quality, stable operation and reliable support.
Additional recommendations for the installation and operation of the inverter
Correct parameter settings
Before installing the inverter, it is necessary to set the appropriate motor parameters such as rated voltage, maximum frequency and rated current. This will avoid mistakes and incorrect operation.
Organization of ventilation and cooling
The inverter must be installed in a place with good ventilation or cooling, as it can become very hot when operating at high frequencies. When used in dusty rooms, it is recommended to install the inverter in an airtight cabinet.
Installation and connection
Make sure that all connections are made correctly and securely. Incorrect connection may cause the inverter or motor to malfunction.
Checking before the first run
After installation and connection, before starting the machine, check all the parameters and connections to make sure that everything is working correctly.
Conclusion
The CNC inverter of the machine is one of the most important parts of the machine, which ensures the stability and quality of processing, protects the equipment and reduces energy consumption. When choosing an inverter, many parameters should be taken into account: power, control type, frequency range and supported protection functions. The correct selection of the inverter, taking into account the requirements of specific equipment and its operating conditions, will not only optimize machine performance, but also extend the service life of all its components. This approach will ensure reliable and efficient operation of the CNC equipment in the long term.
