Benefits of Guide Roller Technology
Modern Linear products incorporate the benefits of guide roller technology. Guide roller benefits are numerous compared to competing technologies. They are smooth, fast, quiet, and extremely durable. From DNA scanners to CNC tables to robotics to drawer slides, guide roller components excel in a wide variety of industries and applications. The versatility of guide roller components offer unlimited integration possibilities. Modern Linear guide rollers, bushings and tracks are completely interchangeable with industry standard products.
Our guide roller benefits are as follows:
Linear guide rollers are based on the design of radial ball bearings. The load carrying balls travel in a circular path and are retained and separated from one another. Current ball bushing and ball rail linear systems have a recirculation path that requires the balls to make a quick change in direction. Vibration occurs when the balls collide entering and leaving the load zone.
Linear guide rollers are very quiet due to ball separation. The internal ball bearings are separated by a nylon retainer. This feature reduces noise common in recirculating ball systems. Noise is amplified in recirculating guide systems when each ball collides with the next in the ball path.
Rugged. The radial bearings of Modern Linear guide rollers are offered with shields or rubber seals. The seal is superior to wipers common in recirculating ball guides. Debris caught between the wheels and track is wiped away naturally. Ball bushings and ball rails use the shaft or rail as the inner race of the bearing, making them susceptible to contamination failure. 440c stainless steel guide rollers and track are also available for corrosive environments.
Recirculating ball guides are limited by the sharp turn the balls must make as they enter and leave the load zone. Guide rollers are only limited by the rotary speed of the radial bearing. Maximum guide roller speeds are up to 2x faster than ball bushings or ball rails.
Modern Linear guide rollers are simple to design, install and maintain. In operation, the guide system is compliant and forgiving to mis-alignment and machining inaccuracies. These features result in lower initial, installed, and total cost.
Components vs. Linear Guides
Individual components (guide rollers, bushings, and track) offer the widest variety of design flexibility for automated machinery. Components can be integrated into a preexisting machine frame for the most discrete solution. Additionally, part cost will always be lower with components than with pre-assembled linear guides.
Pre-assembled linear guides (Vector Trio/Quad, DT Linear Guide) offer the greatest simplicity of design and low cost installation. No need to align parallel track components or assemble carriages. When total cost is the highest priority, pre-assembled linear guides may be favorable. Whatever you choose, combinations of guide rollers, track and linear guides can be selected for optimum cost and machine performance.
Lubrication in Linear Motion
Lubrication plays a critical role in extending the life of mechanical equipment.
With that said, there are many issues related to the application and use of lubrication in mechanical systems.
In linear motion systems that involve metal guide rollers or recirculation ball slides, lubrication is preferred and often necessary where there is metal to metal contact.
Some applications make the use of lubrication difficult. Environmental conditions such as high or low temperature, washdown or heavy contamination may necessitate the use of: special lubrication types, special methods of lubrication dispensing, or prevent the use of lubrication at all. Some applications make the manual application of lubrication and other routine maintenance activities difficult or impossible.
Internal Components of a Guide Roller
Linear guide rollers use the basic construction and design of a double row, angular contact, radial bearing. The metal to metal contact between the balls and inner and outer races are lubricated with grease that is captured by either metal shields or nitrile molded seals. The balls are retained and separated by a Nylon 66 molded ball retainer. The rollers are pre-filled with NLGI #2 grease and considered “lubed for life”.
Internal Grease Options
Modern Linear offers options in: lubrication specification, ball retainer material and seals/shields. Options allow the rollers to withstand environmental conditions and extend life when requirements include: High/low temperature, vacuum/cleanroom and washdown.
External Lubrication: Roller/Track Interface
With v-groove guide rollers running on v-edge track, there is also a metal to metal contact area between the groove and v-edge. In most applications, maintaining the presence of some lubrication is desirable. Exceptions would be applications having very light loads or very low duty cycles. In applications where conditions are not extreme and routine maintenance can be performed, the track should be periodically wiped down with a clean oily rag to add a layer of oil film to the metal surface. This oil will be picked up and redeposited by the rollers as they move back and forth along the track. The oil film with also add a level of corrosion resistance to the track if it is inactive at times. This activity should easily fit into the schedule with other maintenance tasks. As in most lubrication tasks, excess lubrication is not better. It only needs to be in the right place to be effective.
Extreme Conditions
In extreme conditions there are many lubrication options to maximize the life of the system, including none at all. V-groove roller systems are durable by design. In conditions that make lubrication at the roller track interface impossible, the system is still capable of operating sufficiently as the design parameters allow. Without lubrication, the friction between the surfaces of the roller groove and track v-edge will increase wear at these points. The wear may announce itself as an increase in noise as the system travels, and over time create a clearance between the mating parts. This will certainly affect the performance of the machine and function of the slide system that will indicate a need for maintenance or rebuild. It is rare for these systems to fail catastrophically or lock up completely causing damage to other expensive machine components. If a linear system is required to operate in extreme conditions where no additional maintenance can be performed, v-guide roller based systems are tough to beat.
Extending Life
In applications where lubrication can be used, but intermittent maintenance schedules are undesirable, there are several options. Coating processes that incorporate Teflon can be added to the track sections. This creates the same lubricious area at the contact points between the roller and track. The material is picked up by the rollers and tends to remain in the contact area longer than applied oil. The Teflon coating gives additional corrosion protection to the non-v-edge section of the track. Additionally, Modern Linear offers fixed felt lubricators as an option to the linear guide carriages for Vector Quad and Double Track Linear Guide. The lubricator is a fixture for a block of oil impregnated felt. The felt is positioned between the rollers and track so that a film of oil is continuously distributed on the v-edge. The only maintenance is the infrequent addition of oil injected in the felt through small holes in the fixture.
Comparison to Recirculating Ball Guides
Recirculating ball slides don’t have the benefit of continuous seals to retain the lubricant in the area of contact between the ball and races. The shaft that the bearing block rolls on, acts as the inner race of the bearing. By design they are vulnerable to contamination and extreme environmental conditions. Good machine design requires that these guides be completely covered by shrouds or bellows or completely isolated from the environment. When contamination is present and cannot be kept away from the shaft and bearing block, it is pulled into the recirculating ball path. Most commonly, failure results when the contamination causes the block to jam and lock up. This has the potential to cause major damage to other expensive parts of the machine.
Conclusion
Lubrication is important, but not always necessary when implementing v-groove roller systems in machine design. Modern Linear has many options to consider when applying linear systems in a machine design.
A Word About Failure
The definition of failure is different for all machine components. Failure of linear systems can be based on many factors but is usually defined as a reduction in position accuracy that affects the overall performance of the machine or application. In some cases it can be as simple as an increase in noise. It could also be that the only definition of failure is
catastrophic: the moving carriage breaks or seizes, causing the machine to stop running.… Kaboom!
In contaminated environments the life of the system is often the most important design consideration. Recirculating ball guide systems are sensitive to contamination but can be protected by bellows, covers and shields. This increases component and installation cost. Guide roller systems excel in contaminated conditions for several reasons:
- The radial bearings are sealed keeping particulates away from the ball bearing complement.
- Contaminants that land between the guide roller and track are naturally swept away by the wiping action of the roller.
- Costs remain low due to the economy of guide roller components, the ease of installation and the lack of additional components to isolate the guide.
When all factors are considered, guide roller technology is an excellent choice for a wide variety of applications.