Based on the general guiding ideology and on the basis of fully considering the characteristics and difficulties of the proposed large gear measurement, the key technical problems of large gear on-machine measurement can be summarized as follows:

(1) Reduce the problem of structural size of measuring device

Due to the large size of the gear to be measured, the problems of measuring the volume and size attached to the machine tool can not be ignored. Adopting new measuring principles and methods to reduce the structural size of additional devices is one of the problems that must be solved in on-machine measurement.

(2) Precise angle measurement

Because the diameter of the precision angle measuring element is much smaller than that of the measured gear, the problem of linear value amplification of the error of the angle measuring element is prominent. At the same time, due to the particularity of the workbench structure of the large precision hobbing machine, it is very difficult to install the angle measuring element and the workbench coaxially. Design the precision angle measuring device and explore its effective and reasonable installation method, It is an important prerequisite for gear angle signal measurement.

(3) Error separation and accuracy compensation

The machine tool on which the on-machine measurement depends has large original error, and the additional device inevitably has original error, which affects the measurement accuracy. Under the idea of “compensating stiffness with flexibility”, make full use of the software function of the computer to separate and compensate the above errors, so as to eliminate or reduce the influence of these error factors, which is a problem that must be faced by on-line measurement.

(4) Solve the inertia problem in the measurement process

The inertia of the measured gear is very large, and the additional measuring device also has great inertia. The problem that the moving parts can not be accurately positioned in the measurement is prominent. Completing effective measurement operation under the condition of continuous rotation of the measured gear is another problem that must be solved in on-machine measurement. This mainly refers to the probe tracking problem in tooth pitch measurement and helical gear tooth direction measurement under the condition of continuous rotation of the measured gear.