What is Cam Roller Technology (CRT)?
Cam rollers (also called Track Rollers, Backup Rollers or Cam Followers) are self-retaining, single row or double row ball or needle roller bearings – somewhat similar to a radial ball bearing. Usually, these bearings have a much thicker walled outer ring than their radial ball bearing cousins. These outer rings are often profiled to match the mating surface – flat, gothic arch, “V” and convex are the four most common profile shapes. Unlike most radial ball bearings, these bearings are designed to support both radial and axial forces, typically in both directions.
Cam roller bearings are available with and without a shaft, sometimes called a “yoke”. The options with a shaft will often come in a concentric version and an eccentric version. In designs where a specific preload is important, engineers will often place fixed (concentric) cam rollers on one side of the rail and adjustable (eccentric) rollers on the other side.
PBC Linear uses the abbreviation “CRT” for Cam Roller Technology.
If I design my own rolling carriage, where do I place the adjustable (eccentric) rollers?
The concentric (fixed) rollers should be placed on the side of the rail that sees the higher load. The eccentric (adjustable) rollers would be placed on the opposite side.
If I design my own rolling carriage, do I really need adjustable (eccentric) rollers?
This depends on your accuracy/repeatability requirements for your application and the accuracy of the mounted rail, more specifically the parallelism between the two or more rails. If you have a low accuracy requirement (e.g. a sliding door) then you may be able to use only concentric rollers. However, if your sliding door is attached to a sheet metal assembly, then you may need an eccentric roller to make up for the stack up of tolerances in your assembly. If you have a precision application, then eccentric rollers are almost always required.
Do engineers design CRT or IVT systems with three or more rails?
While single rails are the most common for Redi-Rail and Commercial Rail applications, two rails can be used in parallel. Two rails are almost always used for component products like Hevi-Rail and V-Rail.
While it is not very common, the use of three rails is occasionally implemented. In this case, typically two of the rails would be used for guiding the system’s motion and the third rail would only be used to counteract a moment that is applied in a single direction. An example would be if you were designing a punch press or hydraulic cylinder that needed to move back and forth along an axis. Two rails would be used to guide the end of arm tooling back and forth and the third rail would be used to counteract the moment applied to the carriage each time the punch press or cylinder was actuated.
What are the benefits of cam rollers compared to other bearing types?
There are numerous benefits to Cam rollers over other bearing types. Typically, the maximum speed of a cam roller will be higher than a plain bearing or a recirculating ball bearing (round or profile rail). Cam roller bearings can typically be used in dirtier environments as the balls inside of the cam roller are sealed.
What applications are best suited for cam roller systems?
High speed, high acceleration and dirty environments are where cam roller bearings excel. Also, because cam roller bearings can be installed one bearing at a time, these can be adapted to various different designs – especially where two rails would be far apart (like a sliding door). Cam rollers can be installed in applications where the mounting surface is less precise, like weldments or sheet metal assemblies because they are more tolerant of misalignment between two parallel rails.
What materials are used in PBC Linear Cam Rollers?
PBC Linear Cam rollers can be steel or stainless steel. Some products also offer polymer rollers.
How do cam rollers handle high-speed and heavy-duty applications?
Because the balls inside of the bearings do not recirculate, they don’t have to go in and out of a load zone and reverse direction, so cam rollers are more tolerant of high-speed applications.
Are cam roller systems resistant to contamination?
Yes – for two reasons:
Can cam rollers handle cantilevered loads?
Like any type of linear motion design, the engineer should do their statics and dynamics calculations to determine the force acting upon each bearing (Fx, Fy, Fz, Mx, My, Mz). The benefit to cam rollers is that an additional cam roller could be added to a design where needed to overcome the moment created by a cantilevered load.
How do cam rollers perform in environments with high vibration or shock?
Cam rollers perform well in high vibration and shock environments; however, like all bearing systems, there may be a reduction in expected life as a result of the vibration and shock. Refer to the technical section of each product catalog for any de-rating factor.
What maintenance is required for a PBC Linear Cam Roller systems?
The cam roller bearings are lubricated for life (with the exception of Hevi-Rail which offer lubrication ports). The outer surface of the cam roller will require lubrication against the rail (with the exception of polymer rollers). PBC LINEAR offers lubrication wipers for Redi-Rail and IVT to automatically apply lubrication.
How do I choose the right Cam Roller system for my application?
Note: If you describe your load in [metric] tons, then Hevi-Rail is likely your best option.
The first thing to do is to decide whether you want a pre-designed rail and carriage (e.g. Redi-Rail, Commercial Rail, Integral-V, etc.) or if you want to design your own moving system with independent rails (e.g. V-Rail, Hevi-Rail, Integral-V, etc.). Within each category of products, there are several options based on the performance characteristics (life, load, price, etc.). You will need to calculate the performance requirements of your application then compare those against the available product options to determine the best fit.
If you need additional assistance, please contact our applications engineers for assistance. Click on the ‘Ask an Engineer’ link at the bottom of the page.
What is the OD tolerance of the radial Hevi Rail rollers?
+0/-0.04mm
Can you interchange to/provide this cam roller?
PBC Linear does not offer the standard type of cam roller. Although the product line Cam Roller Technology seems to allude to this product offering, it simply refers to products using track-style rollers and combined bearings, NOT cam rollers. Please refer to the online catalog pdf for available products