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Setting the seal on success

New seals boost worm gear efficiency

Professional worm gearbox manufacturer Fixed Star specializes in transmission machinery and has over 30 years of experience in the industry. When the company began assessing how to make its aluminum case range more efficient, it found room for improvement in one area of components in particular: the seals.

Fixed Star Power Transmission Group is a leading small-sized worm gear provider, originating in China. Constantly striving to ensure and enhance quality in its products, Fixed Star regularly assesses its product range for improvements. In one product line of the company’s portfolio, the worm gear reducers include an aluminum case which offers the benefit of being lightweight and non-rusting. To ensure continued quality for the products in this range, Fixed Star wanted to carry out a technical review.

Defining goals: what was Fixed Star looking for?

While the aluminum case range of worm reducers is a successful line of products, the company sought to increase efficiency and lower operating temperatures. Assessments began on the in-house components and Fixed Star also recognized that the seals used could be improved in order to boost performance. The company conducted a two-year-long search period spanning China, Taiwan, Japan, and Europe with rigorous testing rounds. SKF was chosen to provide the seals for the aluminum case range—but the worm gear producer received much more than a product.

An experienced partner in seals

With specialist experience with seals in all kinds of industries, SKF provided Fixed Star with detailed information. For example, the term ‘contact seal’ implies that the seal edge is in contact with the rotating shaft during operation. In fact, a well-designed seal actually runs on a micro film of oil between the shaft and the seal, thus creating much less friction and heat. Fixed Star learned why its seals were not delivering the efficiency desired in the first place and SKF advised them on the ideal seal for the job.

6% increase in gearbox efficiency

Pumping ability: a crucial function

The Fixed Star engineers also received advice on “pumping ability”, which has a considerable effect on the performance of the seal in the short term and the long term. Pumping ability relates to a situation where molecules of oil escape from the oil side of the seal (inside) to the air side of the seal (outside). A seal with poor pumping ability will lose lubricant through leakage, leading to increased temperature and poor lubrication of the gear mesh and bearings. But a seal with good pumping ability returns the oil from the air side to the oil side to maintain lubrication with consequently lower heat generation and reduced component wear. Pumping ability is an important consideration as reduced friction means increased resistance to wear and ageing and much lower operating temperatures.

Operating temperatures reduced by 25%

Sealed with the future in mind

The seal chosen for this case was a radial shaft seal with rubber outer diameter. Although its design looks simple, the final form, material thickness, spring tension, strength of flex section, and angular surfaces of the seal lip are precisely designed to achieve maximum performance. Having installed this type of seal made from a nitrile rubber compound, Fixed Star has received seals with good wear resistance and compatibility to most mineral and synthetic oils and greases. In addition, the company received guidance on what makes a good seal and what to look for when choosing seals in the future. For example, whether it has a sealing lip for optimal fit and sealing ability. Or, if it has a spring-loaded lip capable of dynamic runout to maintain sealing ability even after excessive wear or shaft misalignment has occurred.

Not only did we learn a lot about seals and sealing mechanisms, we also learnt that SKF is as good a designer and manufacturer of seals as they are of bearings.

Mr. Fugen Gao, Chairman of Fixed Star

Project completed, but the journey goes on

Overall, the worm gear manufacturer was very pleased with both product and service. And the results: gearbox efficiency increased around 6% and operating temperatures decreased by around 25%. Fixed Star not only gained a wear-resistant product to achieve its goals of efficiency and lowered temperatures, but also in-depth guidance that it can use to continue optimizing performance in the future.

The seal chosen for this project was from the HMSA10 range of radial shaft seals. Find more information on this seal type and designs on the SKF website.