What are the advantages of gear-hobbing machine in machining large gears?

Gear hobbing machine is one of the widely used gear processing machine tools. When using the special hob, it can cut straight and helical cylindrical gears, large gears, worm gears, sprockets, etc. It can also process splines, sprockets and other special tooth shaped workpieces. It is widely used in automobile, tractor, machine tool, engineering machinery, mining machinery, metallurgical machinery, petroleum, instrument, aircraft, spacecraft and other machinery manufacturing industries. There are many types and specifications of gear processing machine tools, including small machine tools for machining gears with a diameter of several millimeters, large machine tools for machining gears with a diameter of more than ten meters, and high-precision machine tools for machining precision gears with efficient machine tools. Here is a brief introduction to the hobbing machine.

1. Machining principle of gear hobbing machine

According to the gear forming principle, on the basis of considering the rapid follow-up requirements and transformation costs of the gear hobbing machine feed system, on the basis of retaining the original gear splitting transmission chain of the ordinary gear hobbing machine, according to the principle of the two coordinate circle, through the interpolation of the numerical control theory, the vertical feed movement and horizontal radial feed of the machine tool holder are numerically controlled to achieve gear processing.

2. Analysis of transmission chain of gear hobbing machine

The gear hobbing machine shall have the following drive chains: main drive chain, power generation drive chain, vertical feed drive chain, axial drive chain and radial feed drive chain.

3. Working action of gear hobbing machine

(1) Main motion: the main motion is the rotary motion of the hob.

(2) Motion generation: the rotation of hob and workpiece is driven by servo motor respectively. The servo motor moves according to the control command to ensure that the hob is synchronized with the workpiece. The scheme has large investment, high cost, high requirements for real-time control of motion controller, and difficult control software programming.

(3) Vertical feeding movement: vertical feeding movement refers to the continuous feeding movement of the hob along the axial direction of the workpiece to cut the tooth profile on the entire tooth width. The axial feed is driven by the servo motor, and the required feed speed can be obtained by adjusting the speed.

(4) Radial feed: feed the workpiece in the direction of hob, and process the roller gear through the vertical feed motion and radial feed linkage device. The horizontal radial feed is driven by the servo motor, and the hob is moved tangentially by the worm pair and screw pair. The required tangential feed speed can be obtained by adjusting the speed of the servo motor.

4. CNC system of gear hobbing machine

The open motion control card is used to drive the motors of each axis, giving full play to the advantages of software and hardware on the CNC platform, enriching and improving the development environment. The hardware circuit consists of peripheral equipment, signal conversion circuit and auxiliary circuit, forming a complete simple CNC system, which completes a series of functions such as program input and processing, display, motor drive, etc.

5. Precautions for gear hobbing machine

(1) When machining gears on the CNC gear hobbing machine, the position of each axis should be determined according to the drawing parameters of the workpiece, the size of the fixture, the hob parameters and the process requirements. The method of two coordinate linkage and circular arc interpolation shall be used to deal with the cylinder spur gear and helical gear with circular arc symmetrical to the tooth width of the workpiece.

(2) In order to reduce the cost and the number of CNC shafts, the original mechanical gear hobbing machine has been changed less. The drum gears of different sizes can be processed through parameter setting, which is simple and convenient to operate.

(3) The servo motor is used to control the feed axis respectively through the numerical control system. The feed system of CNC machine tool shall meet the basic requirements of no clearance, low friction and high stiffness.

(4) Whether each axis has motion error overrun, servo alarm, motion completion, limit switch action, etc. The real-time control module is implemented by the interrupt service program. It reads the position of each axis in each clock interrupt cycle, calculates new motion control instructions according to the processing requirements of the processing object, and sends them to the mover for interpretation and execution.

(5) Because gear machining is difficult, especially for the machining of superhard materials such as stainless steel and titanium alloy, special gear cutting oil should be selected to ensure the accuracy of gear workpiece.

These are the advantages of using hobbing machine to process large gears. For different gear workpieces, appropriate processing methods shall be adopted.

Foshan Nanhai Haiyu Electromechanical Industry Co., Ltd. is equipped with more than 100 sets of advanced precision processing equipment, including CNC formed grinding wheel gear grinding machine, gantry machining center, four and five axis machining center, CNC lathe, CNC gear shaper, CNC milling machine, CNC gear hobbing machine, gear chamfering machine and other processing and testing equipment, which can provide various processing and production services, such as precision gear processing, large-scale gear processing, CNC processing, CNC lathe processing, etc.