The CNC forming wheel gear grinding machine adopts the latest forming wheel gear grinding machine design concept. It is a complex and high-end technology that integrates mechanical, electrical, hydraulic, automation technology, servo control technology, precision measurement technology, computer software technology and other disciplines. CNC machine tools can process straight (oblique) involute gears and other arbitrary tooth shapes, such as cycloid gears, arc gears, etc., with high efficiency, high precision, and high reliability.

1. High efficiency

Adopting profile grinding, the grinding wheel and gear are in line contact, and the grinding rate is high; the machine tool is equipped with a high-pressure and large-flow cooling device, which is suitable for high-power, large-depth-of-cut grinding processing, reduces the number of rough grinding cycles, and improves the grinding efficiency of the machine tool. It is a traditional machine tool 3-5 times the efficiency.

2. High precision

Adopt digital servo system, select high-precision grating ruler, fully closed-loop control, smooth movement, no impact, and achieve high movement accuracy; grinding expert system has error correction function, which can compensate grinding machining errors and improve machine tool grinding accuracy .

3. High reliability

High rigidity design is adopted to ensure the high geometric accuracy of the machine tool; the key points of the machine tool are arranged with cooling spray and temperature control measures to ensure the thermal stability of the machine tool; the machine tool is equipped with various sensors such as temperature, pressure, flow, and vibration to work on the machine tool. The status is monitored in real time to ensure the high reliability and stability of the machine tool.

 

3. New technology application

 

1. Design and manufacturing technology of large-scale CNC forming gear grinding machine

(1) Modular design technology

The machine tool adopts a vertical structure and a modular design, which shortens the development cycle and improves the reliability of the machine tool. The machine tool mainly includes the bed, column, worktable, workpiece column, slide plate, dresser, abrasive tools and other components. The layout of the machine tool is shown in Figure 2.

 

 

 

 

 

 

 

 

 

 

(2) High rigidity design and manufacture

 

The forming grinding load is large, and the rigidity of the machine tool is high. In the design, perform finite element analysis and structural optimization of the machine tool and its key components to ensure the high rigidity of the machine tool; perform modal experiment analysis on key components to make the natural frequency of the machine tool much higher than the excitation frequency during grinding; The key joint surface is precisely scraped to ensure the contact stiffness.

 

(3) Thermal characteristics control technology of large gear grinding machine

 

In the working process of the large gear grinding machine, thermal deformation occurs under the combined action of internal and external heat sources, which affects the relative position between the workpiece and the grinding wheel, and reduces the gear processing accuracy. Studies have shown that in precision machining, the proportion of machining errors caused by thermal deformation is 40%-70%. Therefore, reducing thermal deformation and making the machine tool reach thermal equilibrium as soon as possible are essential to improve machining accuracy and stability.

 

The main methods adopted for this are:

 

①Thermosymmetric design of machine tool and optimization of cooling channel. Through the finite element analysis of the thermal deformation of the machine tool, optimize the layout of the machine tool, adopt a thermally symmetric structure, optimize the flow channel design of the machine bed, increase the flow of coolant around the machine bed, make the temperature distribution more uniform, and improve the thermal characteristics of the machine tool.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

②Isothermal grinding control technology. Real-time detection of the internal and peripheral temperature of the machine tool, automatic adjustment of the temperature of the grinding coolant, to keep the temperature difference between the internal temperature of the machine tool and the environment within a stable range, reduce errors caused by thermal deformation, minimize the deformation of the machine tool during work, and meet high-precision grinding Cut requirements.

 

(4) Design and manufacturing technology of hydrostatic guide rail and hydrostatic bearing. The closed hydrostatic guide rail is used to solve the crawling and lagging of the linear guide under heavy load. The linear axis repeat positioning accuracy reaches 0.002mm, the rotary axis positioning accuracy reaches ±3 arc seconds, and the maximum load of the machine tool is 2t, which meets the product design requirements.

 

(5) Application of composite materials. In the assembly process of the machine tool, the geometric accuracy adjustment requires multiple repairs of the guide rail joint surface. When the large machine tool joint surface is repaired, the lifting, turning, and scraping work of large parts is very heavy. The new composite material is used to realize the precision of the machine tool guide rail at one time. It can meet the accuracy requirements, reduce the assembly workload, and improve the assembly accuracy of the machine tool.

 

2. Development of Grinding Expert System

 

The Grinding Expert System is the core software system of the profile grinding wheel gear grinding machine, which solves the cumbersome calculation and programming of the machine tool operator. It can recommend the grinding process according to the user's requirements for grinding the workpiece, and allows the user to choose a variety of grinding methods. , Grinding wheel dressing method, automatically generate machine tool processing program, guide users to carry out precise and efficient grinding, and improve the efficiency of machine tool processing.

 

The main function modules include the following items:

 

(1) Tooth profile modification based on optimization of meshing error under working conditions

 

Gearbox gears have edge contact due to machining, assembly errors, load deformation, etc., resulting in stress concentration, which has a great impact on transmission stability and life. Therefore, precise modification of the tooth profile is required to reduce edge contact and stress concentration. The machine tool adopts form grinding, which can accurately interpolate the tooth profile modification through the fully closed loop servo axis, and realize the accurate three-fold maintenance of the tooth profile.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(2) Tooth surface distortion control technology

 

When grinding helical gears, the contact line between the grinding wheel and the tooth surface is a spatial curve. It is necessary to adjust the angle of the axis of the grinding wheel and the workpiece, change the relative position of the contact line, and avoid the contact line between the grinding wheel and the tooth surface at the same time. Unevenness, there is a knife, resulting in distortion of the tooth surface. The tooth surface distortion control technology developed by the machine tool automatically optimizes and adjusts the angle of the grinding wheel axis according to the workpiece parameters, changes the relative position of the contact line, and improves the tooth surface distortion.

 

(3) Surface quality grinding control technology of workpiece

 

Research on the grinding process of large gears, collect and analyze high-efficiency gear grinding process data, establish a process parameter database, and find suitable grinding process parameters for users to choose from gears with different materials and different heat treatment requirements. The process parameters mainly include grinding wheel abrasive, particle size, dressing feed rate, grinding feed speed, coolant flow and pressure, etc., to guide users to achieve precise and efficient grinding, eliminate grinding burns and cracks, and improve grinding efficiency.

 

(4) Intelligent monitoring of grinding status

 

After secondary development, the AE (acoustic emission) device integrated in the grinding wheel spindle can realize automatic tool setting, automatic allowance distribution, real-time monitoring of the grinding process and grinding wheel wear, and control the automatic dressing of the grinding wheel to keep the grinding wheel sharp and ensure Grinding quality. AE's anti-collision protection function can perform emergency retreat function of the machine tool to protect the safety of workpieces and equipment in the event of tool biting or partial wear.

 

3. On-machine detection and comprehensive error compensation technology

 

(1) On-machine measurement technology

 

The mass of large gears is relatively large, the disassembly and inspection of the gears are not convenient, and the off-machine measurement is time-consuming and laborious. It is necessary to configure the on-machine measurement function on the machine tool. The on-machine measurement function of the machine tool uses the CNC axis of the machine tool to measure the gear, and the measurement data is returned to the grinding expert system to compare with the set target and automatically adjust the processing parameters of the machine tool to realize precision grinding under closed-loop control.

 

The on-machine measurement system of the machine tool mainly measures the gear tooth profile, tooth direction, pitch and cumulative total deviation of the tooth pitch.

 

 

 

 

 

 

(2) Machine tool comprehensive error test compensation technology

Use the laser tracker to measure the various errors of the machine tool servo axis, establish the machine tool space error model, and apply the dynamic operation function of the numerical control system to compensate for the error between the axes. The self-developed transmission chain error tester is used to measure and analyze the machine bed axis motion error, multi-axis linkage error, and interpolation error, and adjust the machine parameters to achieve the best compensation effect.

 

 

 

 

 

 

4. Application of machine tool working status monitoring, early warning and fault diagnosis technology

 

(1) The machine tool has no additional sensor monitoring and early warning

 

Through the built-in position, speed, torque, current, voltage and other interfaces of the machine tool numerical control system, the dynamic response signal of the machine tool can be obtained, the early weak fault characteristics of the machine tool feed system can be extracted, and the dynamic error and various vibrations can be monitored in real time. When the error trend begins to increase and the fault signs begin to appear, early warning of machine tool faults will be carried out in time to improve the stability and reliability of the machine tool.

 

 

 

 

 

 

(2) Application of remote fault diagnosis technology

The machine tool remote diagnosis function realizes the remote control between the external computer and the machine tool industrial computer, so as to perform online operations such as fault diagnosis and parameter modification of the machine tool. When the customer's machine tool fails, the maintenance personnel can deal with the machine failure without going to the site, shortening the maintenance time of the machine tool, improving the working efficiency of the machine tool, and making machine tool user service more convenient and faster.