Rail Systems For Long Travel Applications

PBC Linear often gets inquiries from customers interested in the plain bearing feature of our Gliding Surface Technology in order to solve their long travel applications. Some specific products within this family includes Uni-Guide, Low Profile Uni-Guide, and Mini Rail. In addition, our ceramic coated shafting, also known as aluminum feather shafting, and ceramic coated rail, or feather rail, both fall under the gliding surface category.

Corrosion resistance and light weights are attractive features for these product lines. Although all of them are excellent products and great choices for a wide range of applications, they do not lend themselves well for end joining. The simple reason is that linear plain bearings and carriages that employ plain bearing technology have a precise running clearance for which alignment is critical, and these end joints have a high probability for binding due to misalignment. Also, the carriages for Uni-Guide, Low Profile Uni-Guide, and Mini-Rail are matched to the rail, making the addition of rails problematic.

As previously mentioned, the product families that contain wheels, rollers, or balls are the best candidates to transition a joint along a rail/raceway. We will explore some of those product families that are suited for long-lengths, starting with Roller Pillow Blocks and following with Redi-Rail, Hevi-Rail, and IVT linear guides.

Roller Pillow Blocks use round shafting as the raceway. Large cam followers in the roller pillow block deliver industrial strength performance over long travel lengths while excelling in dirty environments. For very long runs, we recommend the hardened steel or hardened stainless steel shaft be supported by the aluminum support rail. The shaft and support rail assembly (SRA) can be butt joined for long runs, and the low-friction rollers easily navigate joined or misaligned shafts, accounting for any shaft deflection.

– Maximum continuous length for one rail: 15 feet (4.57 meters).
– End joining: low-friction rollers will absorb moderate misalignment and shaft deflection.

Redi Rail is a very versatile product and can be mounted to utilize either the radial load capacity or the axial load capacity. Referencing the coordinate axis below, a load applied in the Y direction makes use of the radial load capacity. A load in the Z direction applies force in the axial loading condition. The Redi-Rail metric series is available in 3-, 4-, and 5-wheel carriage options, and offers a preload feature.

Maximum continuous length for one rail: 19 feet (5.79 meters).
End joining: jointed rails are sufficiently precise in pick and place applications. No self-aligning features or floating option, so alignment is important and one of the main challenges for parallel designs.

Hevi Rail is typically used in applications that require moderate accuracy. Since the rails are mild structural steel, they are easily weldable, making it possible to grind the joint smooth for ease of transition from one rail to another. The heavy load capacity makes this a good choice for those heavy-duty applications that also require long travel.

- Maximum continuous length for one rail: 23 feet (7 meters).
- End joining: easily weldable.

Integral-V Technology offers a range of rail profiles and corresponding carriage sizes. The maximum length of most profiles is about 12 feet, making it sufficient for most applications, but is easily butted end to end for longer runs. The V-profile wheel easily transitions the joint between rails. Most profiles allow use of a single rail due to high moment load capacity. The adjustable preload feature, combined with a maximum speed of 10 m/s makes the IVT a unique choice for a range of applications.
- Maximum continuous length for one rail: 12 feet (3.66 meters).
- End joining: V-profile wheel easily transitions the rail joints.