Countermeasures for technical difficulties in gear cutting

1.Synchronous phase locking

Synchronous phase locking is a method of frequency capture in the field of communication, in order to achieve frequency synchronous tracking. On the gear NC machine tool, the rotation angle of gear cutting tool hob, gear cutting grinding wheel or slotting tool and gear workpiece are detected by encoder or circular grating and transformed into pulse signal through conversion circuit. The number of pulses is directly proportional to the rotation angle, and the frequency of pulses is directly proportional to the rotation speed. Theoretically, the expression f * C of the motion frequency ‘of the workpiece shaft for gear cutting is:


K – number of heads or teeth of gear cutting tools (hob, grinding wheel or slotting tool);

Z – number of teeth of gear cutting workpiece;

NB – resolution of axis angle of gear cutting tool;

NC – resolution of shaft rotation angle of gear cutting workpiece;

FB – working frequency of gear cutting tool shaft.

If the working frequency of the actual gear cutting workpiece shaft is FC, the number difference of corner pulses is:

If you want to guarantee Δ If it is fixed, it should always be true, which is the reason for using synchronous phase-locked method.

The frequency and phase discriminator uses the pulse insertion method to improve the phase resolution, which is taken as times or times, so as to be easy to implement. The frequency and phase discriminator must also have the storage and memory function of pulse difference to prevent step loss and ensure that the gear cutting tool is synchronized with the position and speed of the workpiece. The function of the converter is to transform the control signal into the form required by the driving circuit and design it according to the specific requirements. For the servo motor is DC motor, the converter is designed as an all digital generator. The controller model is a digital controller with a certain range of adaptive parameter tuning function. In the dynamic process, the controller takes zero pulse difference as the control target to ensure effective and rapid reduction until the tracking lag error caused by sudden change of speed and load is eliminated. At the same time, the function of modifying the pulse difference comparison benchmark is also set, so that the relative position of the workpiece can move forward or backward in the dynamic process, so as to realize the function of manually adjusting the grinding amount on both sides of the gear tooth on the gear cutting and grinding machine.

2.Electronic differential synthesis

Using pulse signal synthesis method to complete the function similar to mechanical differential chain is called electronic differential synthesis. The CNC system carries out helical gear hobbing and deep creep grinding based on “difference method”. Taking the coordinate as the detection coordinate, the detection signal is led to the synthesis circuit after proportional transformation. The synthesis circuit is the key circuit to complete the synthesis function. Its function is to add and subtract the two pulse signals according to the pulse number. Before addition and subtraction, the two pulse signals must be staggered.

3.Automatic parameter programming

Gear workpiece, gear cutting tool and machining process data all have obvious parameter characteristics and have the basis of parametric programming. Firstly, the characteristic parameters representing gear workpiece, machining tool and process are extracted and organized into parameter table. Secondly, the undetermined parameter table and database are composed of independent parameters and compliance parameters, including database and mathematical model library. After the undetermined parameter input is determined, it is processed by the parameter processing software to obtain the coordinate motion relationship table of the machine tool. Finally, after post-processing, it is transformed into a machine tool processing program.

The prepared gear cutting program is directly transmitted to the machine tool motion drive software through the communication line for gear cutting, or stored in the intermediate storage medium for call.

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