Just Wipe the Oil Leakage of the Harmonic Reducer with a Rag? It's Not That Simple!


Grease leakage is one of the common faults of robots. Leakage will cause the reducer to lack oil and cut oil, which will aggravate the wear of the gear meshing surface and will further lead to poor precision of robots, and more serious consequences may lead to robot accidents, resulting in economic losses of end users.

In addition, the leakage causes pollution to the environment and corrosive effects on the basic equipment, and also seriously affects the 6S construction of the plant.

At present, one of the solutions given by many robot manufacturers is wiping oil leakage with a rag, which is a solution to treat the symptoms rather than the root cause, and increases the workload of the maintenance staff.

How can we eliminate the problem of grease leakage? First, we need to analyze the cause of the reducer leakage, and then propose solutions one by one.



Causes of Leakage of Harmonic Reducer

1.Pressure difference between inside and outside of the reducer

During the operation of the reducer, various internal friction pairs generate a lot of heat, which causes the internal temperature rise to increase and the pressure to increase. Under the effect of the pressure difference, the grease leaks from the gap. The higher the temperature rise inside the reducer, the greater the risk of leakage.

2.Unreasonable design of the oil seal structure

For example, the oil seal produces pumping effect on the premise that the contact pressure peak is close to the oil side. When the pressure peak is close to the air side, the oil side pressure gradient is less than the air side pressure gradient, and the oil seal will definitely leak.

3.Unreasonable selection of oil seal materials

If the selection of oil seal materials is unreasonable, grease will accelerate the dissolution of rubber at high temperatures, resulting in early seal failure. In addition, unreasonable selection of oil seal materials may lead to early wear of the seal shaft and result in leakage.

4.Unreasonable selection of grease

The selection of grease must be made according to the type of friction pairs, operating modes, working conditions, environmental conditions and grease supply methods. Unreasonable selection of grease will accelerate wear and even cause equipment failure.

5.Not strictly controlled manufacturing and assembly process

Factors such as the amount of oil injected, the smoothness of the shaft, the inclination, and the oil seal can all cause the reducer to leakage.


Haozhi's Solution for Leakage

1. Reduce the temperature rise of the reducer

How can we reduce the temperature rise of the reducer? It is necessary to enhance the tooth shape design ability and improve the gear meshing.

Reducer manufacturers in the industry have different understandings and designs in this regard and their ultimate goal is to increase the number of teeth meshed. The tooth shape of our harmonic reducer is based on the full study of IH tooth shape and curve mapping theory. Our company positively designed and developed the SP harmonic tooth shape and convex contour curve, and obtained a national invention patent. The SP tooth shape ensures that the number of teeth meshed simultaneously can reach more than 30% of the total number of teeth.


In addition, the level of gear manufacturing is improved, such as the accuracy grade of gears and the smoothness of tooth surfaces to reduce friction and heat generation.


Picture of tooth surface of Haozhi harmonic reducer

2.Improve the lubricating ability of the tooth surface to reduce friction and heat

A·Improve the winding effect of oil film

The winding oil film on the transmission parts reduces the wear of the transmission parts, improves the strength of the oil film and reduces the temperature rise. In addition, the winding effect of the oil film has a significant effect on blocking and leak prevention.


B·bearing effect

Haozhi special grease incorporates unique nano-level special ingredients that can penetrate into every corner between parts without causing viscosity changes. In addition, the nano-scale special components function as fine bearings. The bearing effect is used to transform sliding friction into rolling friction, thereby minimizing resistance, suppressing temperature rise, and preventing deterioration of base oil.

3.Seal design

The oil seal is mainly considered from the three mechanisms of lubrication, sealing and pumping. Oil film thickness, contact load, contact width, oil seal lip angle, speed and spring offset have an effect on the pumping effect. Only when the oil-side lip angle is greater than the air-side lip angle, there is pumping, and the sealing effect is the best. When the oil side lip angle is smaller than the air side lip angle, leakage will occur.


In addition, the oil seal of ordinary materials is prone to aging and other phenomena when used for a long time under high temperature, and the choice of oil seal material is crucial.

Compared with the ordinary products in the market, the oil seal of Haozhi harmonic reducer adopts a new structural design, and the high-performance polymer material oil seal is preferred. After a large number of high-temperature aging tests according to the working conditions, the sealing performance is greatly improved.

4.Sealing shaft design

The problem of the smoothness and tilt of the sealing shaft is one of the factors leading to leakage. In order to ensure the consistency of product quality, the control and processing capabilities of the product production process are very demanding.

Haozhi has an intelligent unmanned production workshop, strictly implements the ISO9001 quality management system, ISO14001 environmental management system and is equipped with the world's top testing equipment to provide a solid quality guarantee for the consistency of product production.

The smoother the surface of the sealing shaft, the smaller the friction coefficient and the less heat generated, which reduces the starting torque while lowering the temperature. The surface roughness of Haozhi sealing shaft is strictly controlled according to Ra≤0.1μm.

5.Sealing materials

When selecting the materials of the oil seal, it is necessary to consider the materials’ adaptability to the working medium, working temperature and lip edge when the shaft rotates at high speed. Common sealing materials on the market such as NBR, PTFE and other materials have obvious disadvantages, such as poor performance in high temperature resistance, wear resistance and corrosion resistance, poor softness, inflexibility, poor elasticity, poor following features and easy to break under low temperature installation environment.

The oil seal custom-developed by Haozhi has special materials added to the rubber lip edge, which reduces the friction, makes the shaft rotation lighter and the seal more resistant to high and low temperature and wear.

About Haozhi

Guangzhou Haozhi Industrial Co., Ltd. is an environmentally-friendly high-tech, GEM listed company specializing in R&D,design, manufacturing, sales and maintenance of core components of high-precision electromechanical integration, with the stock code of 300503.


National customer hotline

400 6189 083

Guangzhou Headquarters

Address: No. 6, Jiangdong Street, YongheEconomic Zone, Economic and Technological Development Zone, Guangzhou City,Guangdong Province

Sale phone: 020-62257588

Fax (sale): 020-62868322

Fax (materials and equipment): 020-32226553

Suzhou Branch

Address: No. 888, Middle Chengbei Road, YushanTown, Kunshan City, Jiangsu Province

Sale phone: 0512-55108383


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