KEVOS® MAKEOS · Power Transmission
Linear Guide Selection (Carriage Loads, Life and Static Safety)
What load does the most heavily loaded carriage of this linear guide carry, including the offset and acceleration, and how long will the guide last?
Selection check of a profile-rail linear guide with four carriages on two rails: the static load on each carriage from a load offset along and across the rails, the extra load on the leading and trailing carriages from acceleration at the load’s height, the cubic mean load over constant-speed and accelerating travel, nominal life in kilometres on the 50 km basis with a load factor, life in hours from stroke and cycle rate, and the static safety factor.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Moving mass | kg | Mass carried by the four carriages. |
| Carriage spacing along the rail | mm | Distance between the two carriages on each rail. |
| Rail spacing | mm | Distance between the two rails. |
| Load offset along the rail | mm | Distance of the load’s centre of mass from the carriage pattern centre, along the rails. |
| Load offset across the rails | mm | Distance of the load’s centre of mass from the centre, across the rails. |
| Height of the load centre above the carriages | mm | Height of the load’s centre of mass above the carriage mounting faces. |
| Acceleration | m/s² | Acceleration and deceleration of the axis. |
| Share of travel spent accelerating | % | Share of each stroke spent accelerating or decelerating. |
| Dynamic load rating per carriage | kN | Dynamic load rating of one carriage on the 50 km basis (from the maker). |
| Static load rating per carriage | kN | Static load rating of one carriage (from the maker). |
| Load factor (shock and vibration) | Load factor for shock and vibration (about 1.0–1.5 smooth, 1.5–2 with shock). | |
| Stroke | mm | Length of the stroke. |
| Cycles per minute (out and back) | Number of out-and-back cycles per minute. | |
| Life required | h | Life the machine needs. |
| Least static safety factor | Least static safety factor you require. |
Method and formulas
- Carriage at (±L₀/2, ±W₀/2): P = W ÷ 4 ± W x ÷ (2L₀) ± W y ÷ (2W₀) for weight W = m g.
- Acceleration adds ± m a h ÷ (2L₀) to the leading and trailing carriages.
- Mean load P_m = ³√(s P_acc³ + (1 − s) P_run³) for the most loaded carriage, s = share accelerating.
- Life L = 50 km × [C ÷ (f_w P_m)]³; hours = L ÷ (2 × stroke × cycles per minute × 60); static factor = C₀ ÷ P_acc.
- Example: the worst carriage carries 388.18 N running and 471.51 N accelerating; life is about 45,549 h.
Limitations
- Rigid table and equal carriage stiffness; real load sharing depends on mounting accuracy.
- Lift-off and side loads on the carriages are not included.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Choose a linear guide size for a gantry or slide
- Check life when the load is off-centre
- See how acceleration loads the carriages
Who it is for
- Machine designers
- Automation engineers
- Design engineers
What you get
- Load on each carriage at constant speed
- Peak load during acceleration and the mean load
- Life in km and hours, static safety factor
Interpreting the result
- Centring the load and spreading the carriages cut the worst carriage load the most.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 2365–2416. Topic reference; no source tables or recommended settings are reproduced.
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Open the Linear Guide Selection (Carriage Loads, Life and Static Safety) calculator
