Takeuchi Precision Works Co.,Ltd.

Features of LMB Guides Series / System　| Accuracy Tolerance　|　Mounting Shoulder Height and Corner Shape
Recommended Accuracy of Mounting Surface　| Installation Procedures　|　> Life

> Life

1.Definition of Rated load
2.Factor of Permitted Static Load
3.Determination of Rated Fatigue Life
4.Calculation of Slide Unit Load

1. Definition of Rated load

Basic Dynamic Load C
All LMB guides runs under operation load, so the contact stress acts on the steel balls and the raceways, and the damage called "flacking phenomenon" which is occurred by fatigue of steel in the repeated load. The basic dynamic load is the operating load which specifies 50km of travel for 90% of LMB guides without flacking phenomenon.
Basic Rated Static Load Co
When an LMB guide is given the excessive load or an enormous shock loading, a local permanent deformation takes place partially. When the permanent deformation reaches a certain point, it can prevent a smooth movement. The basic rated static load Co is the load which is total permanent deformation of the raceway and steel ball equal to 1/10000 of ball diameter.
Rated Static Torque M A, M B, M C
The rated static torque M is the torque which causes a permanent deformation equal to 1/10000 of ball diameter at the contact point between the raceway and the steel ball when a moment load is applied.The rated static torque is considered only when the rigidity of the base is insufficient, or being used in the position mentioned in the following table.

Position of Guide	Rated StaticTorque Necessary to be Considered
Ｂ１，Ｗ１	M A, M B, M C
Ｂ１，Ｗ２以上	M A, M B
Ｂ２以上、Ｗ１	MC

The data for C, Co, MA , MB , MC , are included in each dimensional table.
The basic load rating listed in the dimensional table is good in any directions because TSK LMB guide has the same dynamic load capacity in four directions.

2. Factor of Permitted Static Load

In general, the maximum permitted static load against the slide unit is equivalent to the rated static load Co. In repeated linear motion applications, however, unexpected load is caused by the inertia when the slide unit starts or stops. Consequently, the factor of permitted static load fs should be applied to the calculation to decide the correct value.

Operating Condition	fs
Normal Operation	1-2
Smooth running required	2-4
Operation with Impact or Vibration	3-5

* The value of fs for general use is shown in table

3. Determination of Rated Fatigue Life

Basic rated dynamic load, load on slide unit and rated fatigue life are related as follows;

In the case that the stroke ls(m)and the number of return strokes per minute n1(c.p.m)are constant, the rated fatigue life Lh(hr)is calculated by the following formula.

4.Calculation of Slide Unit Load

1.Driving Facto
The load acting against the slide unit is composed of the external load, such as the weight of the table, the cutting force and the inertia force caused by the change in speed or by heavy impact or vibration. These latter types of loading are often difficult to calculate. Therefore, the applied load should be multiplied by a driving factor fd to give the effective external load on the slide unit.
In case of using low hardened steel such as stainless steel or when operating temperature may exceed 100°C, it is necessary to multiply by an additional factor. In such a case, please contact us.

Ｐ＝ｆｄ・Ｐｃ・・・・・・・（４）
　P ：スライドユニットにかかる荷重　［Ｎ］

　　　load on slide unit
fd ：運転係数
　　 driving factor
Pc ：理論的な計算荷重　［Ｎ］
　　 applied load

Operating Condition	fd
Smooth Running without Impact	1.0-1.2
Speed under 15 m/min	1.0-1.2
Running with Light Impact	1.2-1.5
Speed under 60 m/min	1.2-1.5
Running with Heavy Impact	1.5-3.0
Speed over 60 m/min	1.5-3.0

2.Effect of Preload on Internal Load Slide Unit
Internal load PA is determined by external force F and preload of slide unit PPL.

3.Resultant Force of Vertical Load and Horizontal Load
Resultant force of vertical load and horizontal load is determined as follows.

4.Resultant Force of Radial Load and Moment Load
Resultant force of radial load F and momentload is determined as follows.

5.Calculation of Load Variation relating Mean Load
In applications where the load to the slide unit varies, mean load should be used instead of discrete load variations P1P2...Pn.
The mean load is the constant value of load giving the life equal to the life that the average value of the collection of all varying loads allows to give.

1) For cases when the load and travel vary gradually

2) For cases where the load is relatively unchanged

3) Sinusoidal Load Change

6.Frictional Sliding Resistance
For correct load calculation, knowing the frictional resistance of slide unit becomes necessary.
The calculation of frictional resistance is as follows.

Ｆ＝μＷ＋ｆ　・・・・・・・・・・・・（９）
　Ｆ：摩擦抵抗力　［Ｎ］
　　　 frictional resistance force
　Ｗ：スライドユニット荷重［Ｎ］
　　　 slide load
　μ ：摩擦係数
　　　 coefficient of friction
　ｆ：シ－ル抵抗力　［Ｎ］
　 seal resistnce force

The coefficient of friction for TSK Precision LMB Guide is 0.003-0.005 with no preload.
It grows with the preload set or the biased load operated. Further, please contact our company.

> Example
For a slide load(ｍ)of 1600kgf on 4 slide units of HS25T-type, the frictional resistance"F" is calculated:

Ｆ＝9.8μｍ＋ｆ
＝(9.8ｘ0.004ｘ1600)+(4.9ｘ4)
＝82.3Ｎ

7.Load Distribution to Slide Unit
For the life calculation, it is necessary to examine how the extended load operating on an LMB guide is destributed to each slide unit. As general examples, four plane of horizontal axis, perpendicular horizontal axis, vertical axis and acceleration/deceleration are shown below.