Precision planetary reducer and its manufacturing difficulties

Planetary reducer is a high-precision reducer, which can be said to be the most precise reducer at present. Especially in the robotics industry, planetary reducers specifically designed for industrial robots have small size, light weight, high load-bearing capacity, long service life, stable operation, low noise, unique characteristics of power splitting and multi tooth meshing. Their performance can be comparable to other military grade planetary reducer products, and they have the same price as industrial grade products, making them widely used in industrial settings.

The planetary reducer is mainly composed of internal gears (planetary carriers), sun gears, planetary gears, output flanges, etc.

The characteristics of planetary reducers include:

(1) High torque and impact resistance: The planetary gear reducer can achieve 360 degree load on the contact surface. Compared with traditional point contact compression drive, it can avoid the problem of high single point load and easy fracture. The planetary gear structure has the characteristic of high torque and impact resistance;

(2) Small size and light weight: Traditional gear reducers require a certain distance between the large and small gears to mesh, occupying a large overall space and volume. Planetary reducers can achieve repeated connections, effectively improving space and volume issues;

(3) High efficiency and low backlash: The planetary gear can achieve multi-point uniform sealing, and the outer gear ring is tightly combined with the planetary gear to improve the efficiency of the reducer.

Difficulties in manufacturing planetary reducers
The main technical difficulty of precision planetary reducers lies in the production and processing of the three major components: sun gear, planetary gear, and internal gear ring.
 

Gear machining: Traditional precision lathes need to be upgraded to CNC lathes, using dedicated high-speed CNC dry cutting and hobbing machines, and supporting the development of high-speed series dry cutting and hobbing tools to optimize process parameters.

Planetary carrier processing: Automated combination machining machines and combination fixtures are required to achieve precision machining.

Internal gear ring machining: The accuracy of the gear ring directly affects the transmission quality. The machining process of thin-walled gear ring parts mainly includes forging blanks → turning machining → quenching and tempering → turning machining → gear hobbing → nitriding heat treatment and other multiple steps, which are relatively complicated and require high accuracy.

Planetary gear machining: Differences in size or accuracy of individual planetary gears can lead to uneven load distribution and significantly shorten their lifespan. The processing difficulty needs to ensure that the tooth thickness deviation (≤ 0.005mm) and common normal length deviation (≤ 0.008mm) of multiple planetary gears are consistent. During processing, it is necessary to use "grouping selection" (grouping planetary gears according to size tolerances, with an internal error of ≤ 0.003mm in each group) to achieve this, but it increases the cost of processing and testing.