Rated Load and Nominal Life

Rated Loads in All Directions

For Model VR

Load direction
Basic dynamic load rating C (kN)
Basic static load rating C0(kN)

* For Z/2 , truncate the decimals.

For Model VB

Load direction
Basic dynamic load rating C (kN)
Basic static load rating C0(kN)

Static Safety Factor f_S

Models VR and VB may receive an unexpected external force while it is stationary or operative due to the generation of an inertia caused by vibrations and impact or start and stop. It is necessary to consider a static safety factor against such a working load.

fS	Static safety factor (see Table1)
C0	Basic static load rating (kN)
Pc	Calculated load (kN)

Table1 Static Safety Factor (f_s) (Guideline)

Load conditions1	Lower limit of fs
Without vibration or impact	1 to 1.3
With vibration or impact	2 to 3

• 1 In general, factors that cause vibration and impacts include acceleration and deceleration, sudden starts and stops, transmission of vibration and impacts from external devices and machines, and changes in processing force over time.

Calculating the Nominal Life

The nominal life is defined as 50 km for a THK LM Guide with balls and 100 km for an LM Guide with rollers. The nominal life (L₁₀) is calculated from the basic dynamic load rating (C) and the load acting on the LM Guide (P_C) using the following formulas.

• LM Guide with balls (50 km basic dynamic load rating)

  

  L10	Nominal life (km)
  C	Basic dynamic load rating (kN)
  PC	Calculated load (kN)

• LM Guide with rollers (100 km basic dynamic load rating)

  

When comparing the nominal life (L₁₀), you must take into account whether the basic dynamic load rating was defined based on 50 km or 100 km. Convert the basic dynamic load rating based on ISO 14728-1 as necessary.
ISO-regulated basic dynamic load rating conversion formulas:

• LM Guide with balls

  

  C50	Basic dynamic load rating based on a nominal life of 50 km
  C100	Basic dynamic load rating based on a nominal life of 100 km

• LM Guide with rollers

  

Calculating the Modified Nominal Life

During use, a cross-roller guide/ball guide may be subjected to vibrations and shocks as well as fluctuating loads, which are difficult to detect. In addition, the surface hardness of the raceways, the operating temperature, and having blocks arranged directly behind one another will have a decisive impact on the service life. Taking these factors into account, the modified nominal life (L_10m) can be calculated according to the following formulas (3) and (4).

Modified factor α

α	Modified factor
fT	Temperature factor (see Fig.1 on A7-6)
fW	Load factor (see Table 2 on A7-6)

Modified nominal life L_10m

• LM Guide with balls

  

  L10m	Modified nominal life (km)
  C	Basic dynamic load rating (kN)
  PC	Calculated load (kN)

• LM Guide with rollers

  

Calculating the Service Life Time

When the nominal life (L₁₀) has been obtained, if the stroke length and the number of reciprocations per minute are constant, the service life time is obtained using the following equation.

Lh	Service life time (h)
ℓS	Stroke length (mm)
n1	Number of reciprocations per minute(min-1)

f_T : Temperature Factor

If the temperature of the environment surrounding the operating model VR or VB exceeds 100℃, take into account the adverse effect of the high temperature and multiply the basic load ratings by the temperature factor indicated in Fig.1 .

Note) If the environment temperature exceeds 100℃, con- tact THK.

f_w : Load Factor