More info

How to choose the right telescopic guide

HOW TO CHOOSE THE RIGHT TELESCOPIC GUIDE
Four tips from Rollon to help selecting the right telescopic guide for an intended application.

The telescopic bearings from Rollon deliver high load capacity and rigidity for applications in harsh industrial environments. If your application requires one, there are some things you’ll want to consider like material and stroke options, load placement and life calculation. Here are some pointers to help you pick the right bearing for your application.

MATERIAL:

To minimize deflection, carefully consider all possible materials for your telescopic bearing. Some common materials, along with their pros and cons, include:

Stamped steel: easily the most economical choice, stamped steel doesn’t handle vibration and shock loads as well as other materials.

Aluminum: even though it’s a good choice for lightweight and low duty applications, aluminum has more deflection than other materials.

Cold rolled steel: cold rolled steel is another low cost option that doesn’t undergo heat treatment. However, in case of heavy loads, pitting and denting occurs in raceways since the ball hardness is greater than the rail and slider.

Hardened cold rolled steel: for the most robust designs, hardened cold rolled sliders and raceways are your best bet. Even though they’re most expensive to manufacture and assemble, this material lets you preload for better rigidity and less deflection.

STROKE OPTIONS:

When picking a telescopic bearing, there are three stroke options to choose from: partial, full and over-extension. Telescopic guides also come with dual or double stroke  configurations, allowing loads to move in both directions while maintaining the same closed length.
 
Partial extension stroke: refers to an extension length that’s 50 to 65% less than the closed length. 
Full extension stroke: refers to an extension length that’s equal to the closed length. 
Over-extension stroke: refers to an extension length that’s up to 200% greater than the closed length.

LOAD PLACEMENT:

Another important factor to consider is load placement. The load’s center of gravity should be placed as close as possible to the centre of the moving element for even load distribution among the balls. Since load calculations are usually made with the assumption that the load is properly distributed, when calculating the static load a safety factor S has to be used. This factor takes into account the basic parameters of the application and it can have a value between 1 and 3,5 in the following formula:

P/C ≤ 1/S

where:
P = effective load
C = permissible load
S = safety factor

LIFE CALCULATION:

When sizing a telescoping bearing for continuous operation, make sure you use the right life calculation and dynamic load capacity.

Some manufacturers express load and deflection specifications based on the slides being used in pairs, while others think of load capacity using a single rail. It’s essential to take the time to understand how the slides are rated and what specifications the manufacturer provides.

The service life of a telescopic rail is dependent on several factors, such as the effective load, the installation precision, occurring shocks and vibrations, the operating temperature, the ambient conditions and the lubrication.

The service life can be calculated with the following formula:
LKm = 100 * ( δ/W * 1/fi )3

where:
LKm = calculated service life in Km
δ = load capacity factor in N
W = equivalent load in N
fi = application coefficient

BOX

ROLLON’S TELESCOPIC GUIDES are the best solution in numerous industrial sectors and improved performance of machine tools.

Telescopic Line is Rollon’s product line for telescopic guides, and it’s developed in three product families: Telescopic Rail, Hegra Rail and Light Rail. Telescopic guides from Rollon are available in differents profiles, with hardened or unhardened raceways, to meet the various requirements in terms of load capacity, rigidity and smoothness, even at maximum extraction. Thanks to their features, Rollon’s telescopic guides are used in numerous industrial sectors, such as: railway, aeronautics, medical, logistics, special vehicles, industrial machines and even in the most demanding furniture applications.

The Telescopic Rail family includes telescopic guides with ball cage, high load capacity and reduced deflection. Guides have optimal running properties due to induction hardened steel raceways. The rail geometry has been designed to offer a minimum deflection even under maximum load and when the rails are fully extended.

The Hegra Rail family includes various telescopic guide profiles with ball cage for partial, full and overextension up to 200% of closed length. Available in different materials such as steel, aluminium or stainless steel for better loads handling and minimal bending.

The Light Rail family includes full or partial extension lightweight telescopic guides to be used in environments allowing only reduced weight components. Elastic shock absorption avoids permanent distortion. The self-cleaning raceways mounted on the Light Rail telescopic rails ensure safe operation and less frequent maintenance. Smooth and quiet operation is ensured even with heavy loads.

Rollon Group is present in India with a direct branch in Bangalore to provide and develop the best solutions, following the local markets and individual needs.