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Linear Guide Life Calculator

Worst-block load, static safety factor and rated life for profile rail guides.

Calculate the load on the most heavily loaded block of a profile rail linear guide from vertical and lateral forces, pitching moment and rolling moment. The calculator handles one or two rails with two, three or four blocks per rail.

  • Live results
  • Full step-by-step working
  • PASS / FAIL checks
  • Free PDF report

Inputs

Results

Max block load PE
1667 N
Static safety fs
22
PASS
Travel life
123019 km
Service life
205031 h
PASS
Step-by-step calculation (8 steps)
  1. 1Vertical load per block
    FormulaPv = Fz / (nr·nb)
    SolutionPv = 4000 / (2 × 2)
    ResultPv = 1000 N
  2. 2Extra load from pitching moment (worst block)
    FormulaΔPp = cp·Mp / (nr·Lb), cp = 1
    SolutionΔPp = 1 × 150000 / (2 × 200)
    ResultΔPp = 375 N
  3. 3Extra load from rolling moment (worst block)
    FormulaΔPr = Mr / (W·nb)
    SolutionΔPr = 100000 / (300 × 2)
    ResultΔPr = 166.7 N
  4. 4Lateral load per block
    FormulaPt = Fy / (nr·nb)
    SolutionPt = 500 / 4
    ResultPt = 125 N
  5. 5Equivalent load on worst block
    FormulaPE = (Pv + ΔPp + ΔPr) + Pt
    SolutionPE = (1000 + 375 + 166.7) + 125
    ResultPE = 1667 N
  6. 6Static safety factor
    Formulafs = C₀ / PE
    Solutionfs = 36700 / 1667
    Resultfs = 22 ≥ 2PASS
  7. 7Rated travel life (ISO 14728, ball type)
    FormulaL = 50 × [(fH·fT·fc / fw)·(C / PE)]³ km
    SolutionL = 50 × [(1 × 1 × 1 / 1.2) × (27000 / 1667)]³
    ResultL = 123019 km
  8. 8Service life in hours
    FormulaLh = L × 10⁶ / (2·ls·n₁·60)
    SolutionLh = 123019 × 10⁶ / (2 × 500 × 10 × 60)
    ResultLh = 205031 h ≥ 20000 hPASS

Engineering takeaways

  • Calculation uses the worst-loaded block and conservative PE = radial + lateral. For roller guides use exponent 10/3 and the catalogue reference distance (100 km for some makers).
  • Confirm rail mounting accuracy, preload class and lubrication interval with the guide supplier.

The PDF report contains every input, formula, substitution and check shown above, in LTM calculation-sheet format.

Worked Example

The calculator then applies hardness, temperature, contact and load factors to give the static safety factor and the ISO 14728 rated travel life in kilometres and operating hours for your stroke and cycle rate.

The calculator above opens with this example. Change any input to run your own case.

Inputs

Basic dynamic load rating C (per block)27000 N
Basic static load rating C₀ (per block)36700 N
Vertical load Fz (total, through carriage centre)4000 N
Lateral load Fy (total)500 N
Pitching moment Mp (about lateral axis)150 N·m
Rolling moment Mr (about travel axis)100 N·m
Number of rails2 rails
Blocks per rail2 blocks
Rail span W (centre to centre)300 mm
Block spacing Lb (outermost blocks)200 mm
Stroke length500 mm
Reciprocating cycles per minute10 cpm
Load factor fw1.2 light impact, v ≤ 1 m/s
Hardness factor fH1.00 raceway ≥ 58 HRC
Temperature factor fT1.00 ≤ 100 °C
Contact factor fc1.00 blocks normally spaced
Required life20000 h
Required static safety factor2.0 normal machine use

Results

Max block load PE1667 N
Static safety fs22 PASS
Travel life123019 km
Service life205031 h PASS

Linear Guide Life Formulas Used

Block load from vertical force

Pv=Fznr nbP_v = \frac{F_z}{n_r\,n_b}
  • nrnumber of rails
  • nbblocks per rail

Moment loads (worst block)

ΔPp=cp Mpnr Lb,ΔPr=MrW nb\Delta P_p = \frac{c_p\,M_p}{n_r\,L_b},\qquad \Delta P_r = \frac{M_r}{W\,n_b}
  • Lbouter block spacing
  • Wrail span
  • cp1.0 for 2 or 3 blocks, 0.9 for 4 equally spaced

Equivalent load

PE=(Pv+ΔPp+ΔPr)+PtP_E = (P_v + \Delta P_p + \Delta P_r) + P_t
  • Ptlateral load per block

Rated travel life

L=50(fH fT fcfw⋅CPE)3 kmL = 50\left(\frac{f_H\,f_T\,f_c}{f_w}\cdot\frac{C}{P_E}\right)^3\ \text{km}
  • Cbasic dynamic load rating (50 km basis)

Service life

Lh=L×1062 ls n1 60,fs=C0PEL_h = \frac{L\times 10^6}{2\,l_s\,n_1\,60},\qquad f_s = \frac{C_0}{P_E}
  • lsstroke (mm)
  • n₁cycles per minute

Basis: ISO 14728-1 dynamic rating life; ISO 14728-2 static rating. Results are for preliminary design and should be confirmed against supplier data and the governing standard.

Linear Guide Life Calculator FAQ

How is linear guide life calculated?

Life is based on the load on the worst block compared with its dynamic rating C. For ball guides L = 50 × (C/P)³ km, corrected by hardness, temperature, contact and load factors. The calculator then converts distance into hours from your stroke and cycle rate.

What static safety factor do I need?

Use at least 1.5 for smooth motion, 2.0 for normal machine use, and 3.0 or more where there is impact, vibration or overhung loads. Static safety protects the raceways from permanent indentation.

Why do moments matter so much?

A moment is resisted by a force couple across the block spacing or rail span. Short block spacing turns a modest moment into a large extra block load. Increasing block spacing is often the cheapest way to extend life.

Is the 50 km or 100 km rating basis used?

ISO 14728 ball guides use 50 km. Some manufacturers quote C on a 100 km basis; convert with C50 = 1.26 × C100 before entering the value.

Can I use this for roller guides?

The structure is the same but roller guides use exponent 10/3 instead of 3. The calculator uses the ball exponent, which gives a conservative life for roller guides.

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