Welcome To Silverstone Machinery Industry Co., Ltd.   
  • Load Rating
  • Rating Life
  • Frictional Resistance
  • Ambient Working Temperature
  • Lubrication and Dust Prevention
  • Structure and Features

Basic Dynamic Load Rating (C)

This term is arrived at based on an evaluation of a number of identical linear systems individually run in the same conditions, if 90% of them can run with the load ( with a constant value in a constant direction ) for a distance of 50 km without damage caused by rolling fatigue. This is the basis of the rating.

Allowable Static Moment (M)

This term defines the allowable limit value of static moment load, with reference to the amount of permanent deformation similar to that used for evaluation of basic rated load (Co).

Static Safety Factor (Fs)

This factor is used based on the application condition as shown in Table 1.

Condition of use Low limit of fs
When the shaft has less deflection and shock 1 to 2
When elastic deformation should be considered with respect to pinch load 2 to 4
When the equipment is subject to vibration and impacts 3 to 5

Basic Static Load Rating (Co)

This term defines a static load such that, at the contacting position where the maximum stress is exercised, the sum of the permanent deformation of the rolling elements and that of the rolling plane is 0.0001 time of the diameter of the rolling elements.

Rating Life of the Lineat System

As long as the linear system reciprocates while being loaded, continuous stress acts on the linear system to cause flaking on the rolling bodies and planes because of material fatigue. The travelling distance of linear system until the fist flaking occurs is called the life of the systems. The life of the system varies even for the systems of the same dimenstions, structure, material, heat treatment and processing method, when used in the same conditions. This variation is brought about from the essential variations in the material fatigue itself. The rating life defined bellow is used as an index for the life expectancy of the linear system.

Rating Life (L)

Rating life is the total travelling distance that 90% of a group of systems of the same size can reach without causing any flaking when they operate under the same conditions. The rating life can be obtained from the following equation with the basic dynamic load rating and the load on the linear system:

L:Rating life (km)     C:Basic dynamic load rating (N)       P:Load (N)

Consideration and influence of vibration impact loads and distribution of load should be taken into account when designing a linear motion system, It is difficult to calculate the actual load. The rating life is also affected by the operating temperature. In these conditions, the expression(1) is arranged as follows:

L:Rating lift (km)     C:Basic dynamic load rating (N)     P:Load (N)    FT:Temperature coefficient    FH:Hardness factor    Fc:Contact coefficient    Fw:Load coefficient

The rating life in hours can be calculated by obtaining the travelling distance per unit time. The rating life in hours can be obtained from the following expression when the stroke length and the number of strokes are constant:

Lh:Rating life in hours (hr)     L :Rating life (km)     N1:No. of strokes per minute (cpm)

Hardness Factor (FH)

The shaft must be sufficiently hardened when a linear bushing is used. If not properly hardened, permissible load is lowered and the life of the bushing will be shortened.

Temperature Coefficient (Fr)

If the temperature of the linear system exceeds 100℃, hardness of the linear system and the shaft lowers to decrease the permissible load compared to that of the linear system used at room temperature. As a result, the abnormal temperature rise shortens the rating life.

Contact Coeffcient (Fc)

Generally two or more linear bushings are used on one shaft. Thus, the load on each linear system differs depending on each processing accuracy. Because the linear bushings are not loaded equally, the number of linear bushings per shaft changes the permissible load off the system.

Number of linear systemsper shaft Contact coefficient fc
1 1.00
2 0.81
3 0.72
4 0.66
5 0.61

Load Coefficient (fw)

When calculating the load on the linear system, it is necessary to accurately obtain object weight, inertial force based on motion speed, moment load, and each transition as time passes. However, it is difficult to calculate those values accurately because reciprocating motion involves the repetition of start and stop as well as vibration and impact. A more practical approach is to obtain the load coefficient by taking the actual operating conditions into account.

Operating Conditionss Fw
Operation at low speed (15m/min.or less)
without impulsive shock from outside
1.0 to 1.5
Operation at intermediate speed (60m/min.or less)
without impulsive shock
1.5 to 2.0
Operation at high speed (over 60m/min.)
With impulsive shock from outside
2.0 to 3.5

The static frictional resistance of the KBS linear system is so low as to be only slightly different from the kinetic frictional resistance, enabling smooth linear movement from low to high speeds. In general, the frictional resistance is expressed by the following equation.

F:Frictional resistance    μ:Coefficient of friction      W:Load weight    f:Sealing resistance

The frictional resistance of each KBS linear system depends on the model, load weight, speed, and lubricant. The sealing resistance depends on the lip interference and lubricant, regardless of the load weight. The sealing resistance of one linear system is about 200 to 500 gf. The coefficient of friction depends on the load weight, moment load, and preload. Table 6 shows the coefficient of kinetic friction of each type of linear system which has been installed and lubricated properly and applied with normal load (P/C=0.2)

Linear System Type Models Coefficient of Friction
Linear Bushing LM LME LMB 0.002 to 0.003

The ambient working temperature range for each KBS linear system depends on the model. Consult KBS on use outside the recommended temperature range.

Linear System Type Models Ambient Working Temperature
Linear Bushing LM LME LMB -20 to 80℃
Linear Bushing LM-A LME-A LMB-A -20 to 110℃

Using KBS linear systems without lubrication increases the abrasion of the rolling elements, shortening the life span. The KBS linear systems therefore require appropriate lubrication. For lubrication KBS recommends turbine oil conforming to ISO Standards G32 to G68 or lithium base soap grease No.1. Some KBS linear systems are sealed to block dust out and seal lubricant in. If used in a harsh or corrosive environment, however, apply a protective cover to the part involving linear motion.

The KBS linear bushing consists of an outer cylinder, ball retainer, balls and two end rings. The ball retainer which holds the balls in the recirculating trucks in held inside the outer cylinder by end rings.

Those parts are assembled to optimize their required functions.

The outer cylinder is maintained sufficient hardness by heat treatment,therefore if ensures the bushing projected travel life and satisfactory durability.

The ball retainer is made from steel or synthetics resin. The steel retainer has high rigidity, obtained by heat treat meant.The synthetics resin retainer can reduce running noise. The user can select the optimum type for meeting the users service conditions.

1.High Precision and Rigidity

The KBS linear bushing is produced from a solid steel outer cylinder and incorporates an industrial strength resin retainer.

2.Ease of Assembly

The standard type of KBS linear bushing can be loaded from any direction. Precision control is possible using only the shaft supporter, and the mounting surface can be machined easily.

3.Ease of Replacement

KBS linear bushings of each type are completely interchangeable because of their standardized dimensions and strict precision control.Replacement because of wear or damage is therefore easy and accurate.

4.Variety of Types

KBS offers a full line of linear bushing:the standard, integral single-retainer closed type, the clearance adjustable type and the open types. The user can choose from among these according to the application requirements to be met.