Across every industry, today’s state-of-the-art manufacturing environment emphasizes variable batch sizes, flexible processes, and high availability. These factors are placing higher demands on individual components, including gear motors, in the manufacturing process. Used to drive conveyor belts and assembly lines, the longevity and strength of gear motors are critical factors in increasing productivity and improving operations. Innovative engineering by Freudenberg Sealing Technologies has resulted in the MSS 1 (Modular Sealing Solution), which significantly increases the life and energy efficiency of gear motors, thus delivering higher productivity and optimizing manufacturing operations.
‘New’ Solution with 20-year History
For 20 years, a combined unit consisting of a Simmerring® Shaft Seal (radial shaft seal or RSS) and a second sealing ring with a sinus-shaped seal lip has proven its effectiveness in gear motors with remarkable reliability and success. Developed in collaboration with a major engineering drive manufacturer, Freudenberg’s sealing solution targeted applications with slow rotating shafts where robustness and long component performance were critical to industrial operations. The system has now become an industrial standard — a sealing success founded on careful analysis, understanding and then designing what customers require to maintain the productivity and profitability of their systems. Importantly, as industrial operations have evolved, Freudenberg engineers have continued to refine this unique sealing system and have now introduced a new system design for use on the high-speed gear input shafts. This MSS 1-HS (High Speed) seal offers the industry the same standard of sealing reliability and extended lifespan of the MSS 1 seal, with the added benefit of functioning in fast rotating, highly dynamic motors.
Engineering the Innovations
In industrial drive systems, there are ever-increasing stresses created due to varying rotational speeds, alternating rotational directions and frequent startup procedures. It is critical that the radial shaft seal ring — a component whose performance and service contributions to the system are frequently overlooked – reliably seals the gear unit to prevent oil leakage and environmental contamination in both rotational directions.
The modular sealing system combines two seals into a single component. This approach results in less friction and a reduced need for axial installation space compared with the standard double seal design, which features a primary seal and a redundant secondary seal. This design further results in greater robustness than a single radial shaft seal ring, providing built-in backup to the primary seal and significant risk reduction.
The RSS, acting as a secondary seal, is friction-optimized, has a dust lip and a smooth, rubberized adhering piece for a secure fit in the housing. As a standard option, it can be made from fluorocarbon rubber 75 FKM 585 or nitrile rubber 72 NBR 902, depending on the application or demand. A grease reservoir containing lubricant is attached between the dust lip and the seal edge to provide lifetime lubrication. The RSS is combined with the primary seal whose seal lip is made of 75 FKM 585.
An important special feature of the sealing system is the seal lip’s sinus-shaped line of contact on the shaft. The sinus shape serves as a bi-directional conveyor structure, distributing the lubricant in the seal gap with a wiping effect that is significantly more effective than a standard seal lip with a traditional straight line of contact. Any dirt particles in the system are kept away from the seal edge, thanks to the continual exchange of lubricant, eliminating contamination, reducing wear and significantly extending the lifespan of the gears.
Manufacturers can expect up to 20,000 in-service hours or more with this solution — under certain circumstances, as much as 30 percent longer than standard seals, within specific parameters and controlled applications. The design of the system also reduces friction by as much as 60 percent, depending upon the application, resulting in lower operating temperatures and related less wear. It also increases energy efficiency with up to 60 percent less power loss when it is applied.
Additionally, as the system does the work of two conventional seals, maintenance requirements are reduced and production processes are optimized that lead to a reduction in the overall cost of operations for a manufacturer.
Industries and Applications
Widely varied industry applications and varying parameters mean that a precise calculation of the lifespan of radial shaft seals is not possible, but it is impressive to note that during Freudenberg’s 20-year technology partnership with the drive manufacturer, more than 3 million MSS 1 sealing systems were used in gear motors without a single return from the field.
Efforts to replicate this success for high speed applications required innovation and design changes. Because the use of this sealing system is limited by a 6 m/s maximum achievable circumferential speed, engineers focused on a primary goal: reducing the mechanism’s friction and temperature development to deliver greater longevity and energy efficiency at high rotational speeds.
To achieve this, engineers focused on three key development initiatives. First, they reduced the contact pressure on the shaft at the sealing edge of the outer RSS by using a specially designed spring. Then, they enlarged the diameter of the dust lip so that it no longer has direct contact with the shaft which is not required on the motor side. Finally, they installed an additional grease reservoir between the two RSS for lifetime lubrication. With these innovations, the high-speed (HS) version of this system allows achievement of circumferential speeds as high as 8 m/s, confirmed by field testing.
Robotic applications demand high speed, with faster acceleration and deceleration, compared with standard industry gearboxes. They encompass a compact space with sophisticated load spectrums. Internal contamination is of heightened concern as well. For all these reasons, it is expected that the MSS 1-HS will have its first application in the drives of industrial robots. This new sealing solution also is important to automation, with a focus on high-reliability and a requirement to be maintenance-free. Additionally, because of its robustness, the solution is suited for other types of drives that are vertically positioned — with the motor positioned on the downside, preventing internal contamination and enhancing service life across a variety of industries.
Freudenberg produces 5 billion seals per year — more than 20 million per day — for virtually every industry from automotive to aerospace to agriculture, construction and heavy equipment, to energy, and food and beverage. The development of materials and technologies that address the unique needs of one industry’s challenges are constantly leveraged to offer innovative new solutions to other industries. In that spirit, the MSS 1 has an ever-expanding array of applications. It can be used in the gearboxes of an agricultural tractor or a piece of construction equipment or in industry for conveyor belts; as well as in the most precise industrial robotic applications.
Today’s global manufacturing environment requires optimization of every component and every process. Global design and the need for economies of scale are driving standardization. Nonetheless, regional customization is often necessary to meet various regulatory requirements. In the United States, there is a regulatory emphasis on environmental protection and energy efficiency that drives the need for these innovative custom solutions.
In that respect, this new sealing solution offers manufacturers twofold value. The custom solution delivers immediate improvement in operational efficiency, including immediate energy savings and the resultant emissions reduction. Additionally, it delivers long-term value in extended component longevity, reduced or eliminated cost of maintenance, and overall reduced cost of manufacturing.
To the industry, this solution is a game-changing innovation in custom sealing technology. It can be further adapted and customized to meet demands in specific manufacturing environments, which will lead to applications and answer demands — some not yet anticipated — that will be critical to the manufacturing industry in the future.