Variable-frequency ultrasonic machining system for computer numerical control milling machine

Patent metadata

Field	Value
Publication number	US-11554512-B2
Application number	US-202017014648-A
Country	US
Kind code	B2
Filing date	Sep 8, 2020
Priority date	Mar 27, 2020
Publication date	Jan 17, 2023
Grant date	Jan 17, 2023

Abstract

A variable-frequency ultrasonic machining system for a computer numerical control milling machine including a cutting force detection unit, a temperature sensing unit and a processor. The processor receives sensing signals of the cutting force detection unit and the temperature sensing unit, processes the received sensing signals according to a set program, and sends control signals to an ultrasonic drive power supply and a corresponding servo motor, respectively. By adjusting the ultrasonic vibration frequency or the frequency of the frequency converter of the CNC milling machine in the machining process, the system ensures the continuity of ultrasonic-assisted milling of a part with a complex curved surface in case of uneven cutting allowance, and improves efficiency of ultrasonic machining.

First claim

The invention claimed is:

1. A variable-frequency ultrasonic machining system for a computer numerical control (CNC) milling machine, comprising:
a frame;
a vertical spindle, rotatably provided on the frame;
a spindle servo motor, for driving the vertical spindle;
a worktable, provided below the vertical spindle, for clamping a workpiece and driving the workpiece to perform feed motion;
a feed servo motor, for driving the worktable to perform the feed motion;
a milling cutter shaft; and
a milling cutter connected to the milling cutter shaft;
wherein, the variable-frequency ultrasonic machining system further comprises:
a connecting shaft, connected to the vertical spindle;
a wireless transmission transmitting winding unit, fixed around the connecting shaft;
a wireless transmission receiving winding unit, connected to the connecting shaft, and spaced apart from the wireless transmission transmitting winding unit located above;
a cutter shaft drive motor, connected under the wireless transmission receiving winding unit and having a hollow shaft, wherein power of the cutter shaft drive motor is connected from the wireless transmission receiving winding unit and introduced through a cavity of the hollow shaft;
a transducer, connected to the shaft of the cutter shaft drive motor, wherein power of the transducer is connected from the wireless transmission receiving winding unit and introduced through the hollow shaft of the cutter shaft drive motor;
a horn, wherein an upper end of the horn is connected to the transducer, and a lower end thereof is connected to the milling cutter shaft;
a cutting force detection unit, provided under the worktable, for sensing and transmitting a current cutting force;
a temperature sensing unit, provided on one side of the milling cutter, for sensing and transmitting a current cutting temperature;
an ultrasonic drive power supply, for providing power for the wireless transmission transmitting winding unit; and
a processor, for receiving sensing signals of the cutting force detection unit and the temperature sensing unit, processing the received sensing signals according to a set program, and sending control signals to the ultrasonic drive power supply and a corresponding servo motor, respectively;
wherein the processor comprises:
a first programmable logic controller (PLC) module;
a second PLC module; and
a central processing unit (CPU), wherein
an input terminal of the CPU receives a cutting force signal or a temperature signal sent from the cutting force detection unit or the temperature sensing unit, and processes the cutting force signal or the temperature signal according to a set program, to obtain a first digital control signal for controlling an output torque and speed of a corresponding servo motor and a second digital control signal for controlling an output voltage or current of the ultrasonic drive power supply;
the first digital control signal and the second digital control signal are respectively transmitted from corresponding output terminals of the CPU to an input terminal of the first PLC module and the second PLC module;
the first PLC module and the second PLC module respectively perform digital-to-analog (D/A) conversion on the first control digital signal and the second digital control signal to obtain a first analog control signal and a second analog control signal in correspondence; and
the first analog control signal and the second analog control signal are respectively transmitted from an output terminal of the first PLC module and the second PLC module to a corresponding servo motor and the ultrasonic drive power supply.

2. The variable-frequency ultrasonic machining system for a CNC milling machine according to claim 1 , wherein the set program comprises:
1) Calculating a change of a cutting force or temperature detected in a set time, to obtain a corresponding cutting force change value ΔF or temperature change value ΔT;
2) Setting a cutting force change threshold ΔF 1 or a temperature change threshold ΔT 1 ;
3) Reducing a current speed of the vertical spindle and a current feed rate of the worktable each by 5% when ΔF>ΔF 1 ; and
increasing the current speed of the vertical spindle and the current feed rate of the worktable each by 5% when ΔF<ΔF 1 ;
or: reducing the current speed of the vertical spindle and the current feed rate of the worktable each by 5% when ΔT>ΔT 1 ; and
increasing the current speed of the vertical spindle and the current feed rate of the worktable each by 5% when ΔF<ΔF 1 .

3. The variable-frequency ultrasonic machining system for a CNC milling machine according to claim 2 , wherein the feed motion of the worktable is performed in three-dimensional (3D) directions comprising X, Y and Z, and is driven by a corresponding servo motor in the respective directions.

4. The variable-frequency ultrasonic machining system for a CNC milling machine according to claim 2 , wherein a bearing seat is fixed on the frame, and the vertical spindle is rotatably connected in the bearing seat.

5. The variable-frequency ultrasonic machining system for a CNC milling machine according to claim 4 , wherein
the wireless transmission transmitting winding unit comprises a first toroidal shell and a transmitting winding, a first resistor and a first capacitor accommodated in the first toroidal shell;
one end of the transmitting winding is sequentially connected in series with the first resistor and the first capacitor;
at least one end of the first capacitor and the other end of the transmitting winding constitute a power input terminal;
the power input terminal is used to connect an output terminal of the ultrasonic drive power supply to obtain required power;
a winding structure of the transmitting winding is adapted to a cavity structure of the first toroidal shell;
the transmitting winding is fixed, through the first toroidal shell, on the bearing seat that rotatably supports the vertical spindle, and the first toroidal shell is around the connecting shaft.

6. The variable-frequency ultrasonic machining system for a CNC milling machine according to claim 5 , wherein
the wireless transmission receiving winding unit comprises a second toroidal shell and a receiving winding, a second resistor and a second capacitor accommodated in the second toroidal shell;
one end of the receiving winding is sequentially connected in series with the second resistor and the second capacitor;
at least one end of the second capacitor and the other end of the receiving winding constitute a power output terminal of the transducer;
the power output terminal is used to connect a power input terminal of the transducer to enable the transducer to obtain required power;
at least one end of the second capacitor and a center-tapped end of the receiving winding constitute a power output terminal of the cutter shaft drive motor;
the power output terminal is used to connect a power input terminal of the cutter shaft drive motor to enable the cutter shaft drive motor to obtain required power;
a winding structure of the receiving winding is adapted to a cavity structure of the second toroidal shell;
the receiving winding is fixed on a circumferential side of the connecting shaft through the second toroidal shell.

7. The variable-frequency ultrasonic machining system for a CNC milling machine according to claim 6 , wherein the second shell is spaced 3-5 mm apart from the first shell located above.

8. The variable-frequency ultrasonic machining system for a CNC milling machine according to claim 1 , wherein the feed motion of the worktable is performed in three-dimensional (3D) directions comprising X, Y and Z, and is driven by a corresponding servo motor in the respective directions

Assignees

• Univ Nanjing Aeronautics & Astronautics

Inventors

• Xu Juan
• Wang Hengchang
• Zuo Hongfu
• Huang Weiqing

Classifications

• B06B3/00

  Methods or apparatus specially adapted for transmitting mechanical vibrations of infrasonic, sonic, or ultrasonic frequency · CPC title

• B23Q17/099

  by measuring features of the machined workpiece (arrangements for measuring workpiece characteristics B23Q17/20) · CPC title

• B23C3/16

  Working surfaces curved in two directions · CPC title

• B26D5/005 Primary

  Computer numerical control means · CPC title

• B26D7/086 Primary

  by vibrating, e.g. ultrasonically · CPC title