The spindle of traditional grinding machine is directly started by the power frequency, and the spindle grinding wheel motor operates according to the traditional start-up circuit. When there is a certain fluctuation of the grid voltage, there will also be a fluctuation of the spindle speed, which will affect the grinding accuracy of the workpiece. So considering of improving the processing quality and efficiency, the frequency control technology is applied to the grinder to achieve satisfying results, but gradually, the general inverter could not meet the site requirements due to the weak ability of environmental resistance. And the high performance VC inverter with large torque at low frequency and high protection degree could meet the on-site requirements of grinder.
2. Process Requirements
Grinding machine is a machine using grinding tools to grind the workpiece surface. The high speed rotating grinding wheel is used to grind the workpiece in most of the grinding machines. The requirements of VFD control solution for high-speed spindle are as follows:
1. Large torque at low frequency. During the rough processing, spindle runs at low speed, but the general inverter outputs lower torque at this time, resulting in the failure of processing. Therefore, large torque at low frequency is required for inverter;
2. Spindle running with stepless speed regulation. According to the requirements of workpieces, the spindle can be set at different speeds, so the ability of stepless speed control is required;
3. High-precision speed running. Speed precision of spindle directly affects the accuracy of workpieces, so the VFD is required to have high precision rotary speed;
4. High degree of protection. Grinding machine works in high oil, high dust and high humidity environment, and the inverter is required to have a high degree of protection, otherwise there will be short circuit damages or even fires;
5. Small vibration and low noise.
3. Solution of VEICHI Products
VEICHI AC80C high performance VFD is used for driving the spindle motor. As a high protection degree closed-loop VC VFD , basing on a new hardware platform, AC80C can adapt to all kinds of damp, dust and other harsh environments, and effectively against dust, oil, high humidity, acid corrosion substance and other high pollutants, to ensure safe use of inverter in extremely harsh environment. It could well meet the requirements of grinder, improving efficiency and greatly reducing the failure rate, which has been highly recognized by customers.
The cylindrical grinder system with VEICHI inverter could achieve steady and reliable operation, and gain high economic benefits for customers. And VEICHI overall solution is highly praised by customers through the actual production test. The specific advantages are as below:
1. Large torque at low frequency. 0.3Hz with 200% of start-up torque under open-loop VC mode, to ensure the normal processing of system at low frequency;
2. High accuracy of steady speed. Under open-loop VC mode, the speed accuracy is 0.2%, to ensure the machining accuracy;
3. Wide speed regulation range. 1:200 speed regulation range to ensure stepless speed regulation.