Milling Machine Case - INVT Goodrive35 Series VFD

Abstract: There are always has high requirements in the machine tolls industry, the mainly required for the drive of the CNC machine tool is not in function, but the basic performance requirements, including the size of the output torque, the speed stability under heavy load conditions, anti-oil anti-corrosion properties, low-torque maintaining zero speed and etc.

Keywords: Goodrive35 Milling machine, High speed Spindle, Close-loop vector control

1.Introduction

Processing efficiency and accuracy is the eternal pursuit target of the metal processing field. During the continuous development of numerical control technology, computer technology, machine technology and processing technology, The traditional processing concept has cannot be unable to meet the people on the processing speed, efficiency and accuracy requirements. The composite processing technology is introduced in this context.

With the continuous advancement of inverter technology, the drive has been able to achieve the similar position function as the servo drive; it can be well used in CNC machine tool spindle position control.

Picture 1 Milling machine main control system

2.Control requirements

This article will introduce INVT inverter application in a lathe factory on integrated machine,the Specific control requirements as following ：

Customers two 4 KW, one of the them to be used to control the spindle, The spindle motor are high-performance induction motor, rated speed at 7000 rpm. The requirements of the converter and control performance include:

a) Large output torque at low frequency, there are high torque output in the milling industry.

b) The stable high-speed operation When the closed-loop control , the machine speed will up to 8000 rpm.

c) High-precision positioning control, with the same precision servo positioning function, to achieve the spindle positioning.

d) There is not shake and a relatively high torque output when Zero speed operation.。

e) A very short deceleration and Acceleration time to ensure the work efficiency of the machine.

f) Good anti-jamming performance when operating at high speed pulse control.

Picture2 the scene pictures

3.INVT Goodrive35 inverter introduce

Goodrive35 inverter is a new high-performance closed-loop vector inverter which developed by Shenzhen INVT Electric Co., Ltd., it has 3 control models: V/F, Vector without PG, and Vector with PG. Wherein in case of sudden addition and subtraction load, speed fluctuation is very small; and also it can drive permanent magnet synchronous motor, inverter motor, direct-drive motors, etc., Customers no longer need to stock different drives for different motors, it can reduce inventory.

G35 has the accurate motor parameters Auto-tuning function, and support rotation and static Auto-tuningWhere the static self-learning can accurately learn the parameters of the motor when the motor cannot be disengaged from the case load; With advanced full three-phase modulation mode, the motor run more smoothly, quieter; Other parameters, functions in the following table:

4.System wiring and debugging

Throughout the system, the run commands and frequency reference given are from the CNC controller.

System debugging

The debugging need to solve several mainly problems：

a.Interference is the biggest problem encountered during debugging

b.Low-frequency torque output capability

c.Speed stability during high-speed operation

d.Spindle positioning accuracy

Because of CNC system via high-speed pulses to control the drive speed, and high speed spindle motor, up to the 8,000 rpm, so the interference of the inverter itself at such a high speed will affect the high frequency pulse command, the pulse control is affected, it can eliminate the interference by the terminal board for updates and add-PE GND terminal.

Motor high speed response, the client asks the spindle motor at start and stop to have a very short time, the setting is 1 second, so the speed loop gain adjustment is relatively large

Torque output, In the lathe and milling process mainly trial  the torque output capability and stability of the inverter，By adjusting the parameters of motor and adjustment current loop parameters allows the output torque greater to meet customer requirements demand even extreme situations。

Spindle positioning accuracy, the customer through multiple operation and CNC machine tool spindle back to zero degree test, to test the positioning precision of frequency converter.

The inverter which used in this system has the short circuit, overload, over voltage, loss phase, stall and so on the many kinds of protection and fault output function, and it can effectively ensure safe and efficient operation system.

5.Conclusion

The Integrated milling machine tool industry is the advanced models and into milling machining center, used in high-end devices such success reflects our Goodrive35 drive inverter products already have a very high control and drive performance. Some cases may have been replaced by a servo control system.

Reference

[1] 《Operation manual for Goodrive35》 Shenzhen INVT Electric Co., Ltd.