The L10 service life of a LinRol recirculating roller guide defines the travel distance — in 10⁵ m (100 km) — that at least 90 % of a similarly designed series of guides achieves, calculated using L10 = (C/P)^(10/3) per ISO 14728-1. How long a guide actually lasts in service depends on the load, lubrication, and operating conditions.
L10 is the distance in 10⁵ m (equivalent to 100 km) that at least 90% of a similarly designed series of guides achieve. The concept originates from roller bearing technology and has been adapted for linear recirculating roller guides. The formula is simple—but applying it correctly requires careful calculation of the equivalent load P.
Key takeaway: The L10 formula for roller guides
L10 = (C / P)10/3
C = dynamic load rating [N] from the catalog | P = equivalent dynamic operating load [N] | Result in units of 10⁵ m (= 100 km of travel). The exponent 10/3 applies to rollers (line contact); for balls (point contact), 3 applies.
Fundamentals: Dynamic Load Rating, Equivalent Operating Load, and L10
The L10 calculation is based on three factors, the precise definition of which is crucial for a reliable result:
Dynamic load rating C
The dynamic load rating C is a manufacturer's specification from the catalog. It describes the constant load at which a group of identical guides achieves a nominal service life of exactly 10⁵ m (= L10 = 1 in the standardized unit). C is measured in newtons (N) or kilonewtons (kN) and is specified separately for each roller recirculating carriage.
Equivalent dynamic operating load P
P is the load acting on the guide carriage that is used for the service life calculation. For a purely radial, constant load, P is equal to the radial force. In practice, however, multiple force components often act simultaneously (radial, axial, moment). In this case, P must be determined as an equivalent load based on the actual forces—the calculation method is provided by the manufacturer or the ISO 14728-1 standard.
For an initial estimate, the Service Life Calculator can be used. For a complete system design including guide selection, use the tool Linear guide sizing.
L10 definition and the lifetime exponent
L10 is the running distance that at least 90% of a similarly designed series of guides achieves. The life exponent depends on the contact geometry of the rolling elements:
- Rollers (line contact): Exponent p = 10/3 ≈ 3.33 — applies to roller recirculating guides (ISO 14728-1)
- Balls (point contact): Exponent p = 3 — applies to ball guides
The higher exponent for rollers means that doubling the C/P ratio increases the service life of roller guides by a factor of 210/3 ≈ 10 — for ball guides, the factor is only 2³ = 8. Roller guides therefore benefit disproportionately from a reduction in operating load. For a direct comparison of both guide types, see Ball guide vs. roller guide.
Step-by-step calculation
Step 1 – Look up the dynamic load rating C in the catalog
C is listed in the product catalog under the dynamic characteristics of the selected carriage. Be sure to note the direction specification (radial C may differ from axial C).
Step 2 – Determine the equivalent operating load P
Determine all forces and moments acting on the carriage and use them to calculate P according to the manufacturer’s formula or ISO 14728-1. For a simple, purely radial load, P = Fr (radial force).
Step 3 – Calculate L10
Formula
L10 = (C / P)10/3
Result in units of 10⁵ m = 100 km distance traveled
Sample calculation
Given:
- Dynamic load rating: C = 20 kN
- Equivalent operating load: P = 4 kN
Calculation:
L10 = (20 / 4)10/3 = 53.33 ≈ 214
L10 ≈ 214 × 10⁵ m ≈ 21,400 km travel distance
In other words, 90% of guides of this type reach at least 21,400 km under this load.
Check static load safety separately
In addition to the L10 service life, the static load safety must be verified, particularly under impact loads or when the guide is stationary under load. The static load rating C0 from the catalog specifies the maximum permissible static load. The static load safety factor is calculated as follows:
S0 = C0 / P0
P0 = maximum static operating load (peak load, static weight load)
The required minimum value for S0 depends on the load type. The following guideline values from linear guide technology apply (manufacturer specifications, e.g. THK, Bosch Rexroth):
| Machine type / operating condition | Minimum value S0 (guideline) |
|---|---|
| General machinery, without shocks/vibration | 1.0–1.3 |
| General machinery, with shocks/vibration | 2.0–3.0 |
| Machine tools, without shocks/vibration | 1.0–1.5 |
| Machine tools, with shocks/vibration | 2.5–7.0 |
A too-small S0 leads to permanent indentations in the raceways (brinelling) and thus to increased noise, play, and premature failure. The binding value is always the minimum stated in the guide manufacturer's catalogue.
Factors affecting actual service life
The L10 formula calculates the nominal service life under ideal conditions. The actual service life achievable depends on additional operating parameters, which can be taken into account using correction factors (extended service life calculation according to ISO 14728-2):
Lubrication
Inadequate or improper lubrication is the most common cause of premature failure. A lack of lubricant increases friction and Hertzian contact stresses—the effective load P increases without the formula directly reflecting this. The correct type, amount, and interval of lubrication are crucial. For details, see Roller Guide Maintenance & Lubrication.
Cleanliness and sealing
Particles and moisture that penetrate the system significantly accelerate wear and corrosion on raceways and rolling elements. Appropriate seals, scrapers, and protective covers are essential in environments containing chips, dust, or coolant.
Temperature
High operating temperatures reduce the load-carrying capacity and impair lubrication performance. At temperatures above 100 °C, heat-resistant lubricants and, if necessary, adjusted load-carrying capacity reduction factors must be used.
Shock loads and preload
Dynamic impact loads increase the effective load P beyond the statically calculated load. An impact factor (typically 1.5–3.0) should be taken into account when determining the load. Excessive preload also shortens the service life, as it increases the effective operating load.
Extended service life: modification factors per ISO 14728-2
While L10 describes the basic rating life for a reliability of 90 %, the modified rating life per ISO 14728-2 additionally accounts for the required reliability as well as lubrication and contamination conditions:
Lnm = a1 · aISO · L10
a1 = life modification factor for reliability | aISO = life modification factor for lubrication and contamination
The factor a1 reduces the service life when a higher reliability than the usual 10 % failure margin is required (values per ISO 281, adopted by analogy for linear guides):
| Reliability | Service life | Factor a1 |
|---|---|---|
| 90 % | L10 | 1.00 |
| 95 % | L5 | 0.64 |
| 96 % | L4 | 0.55 |
| 98 % | L2 | 0.37 |
| 99 % | L1 | 0.25 |
The factor aISO evaluates the lubricant film formation (viscosity ratio κ) and the degree of contamination. With clean operation and a sufficient lubricant film, aISO > 1 is possible and the service life increases; with insufficient lubrication or contamination, it drops well below 1. aISO is determined from the diagrams in the standard — in practice, consistent lubrication is therefore the most effective lever for a long service life.
Practice: Wear Limit and Replacement Point
The L10 service life is a statistical design value, not a specific failure date. In practice, it is recommended to plan replacements before L10 is reached to avoid unplanned downtime. The first signs of guide wear are:
- Increased noise (rumbling, rattling) during travel
- Noticeable clearance in the guide carriage
- Positioning accuracy deteriorates measurably
- Increased friction or uneven force distribution
Lifetime-lubricated or maintenance-free roller guides—such as TEA’s LinRol series—are factory-filled with a permanent lubricant that significantly extends the relubrication interval or eliminates the need for relubrication altogether. This reduces maintenance requirements and lowers the probability of failure during the early stages of operation.
Practical tip from TEA:
Set a fixed replacement interval based on the calculated L10 service life—for example, 80% of L10 as a replacement trigger. At the same time, keep a logbook recording mileage and lubrication events. This will allow you to detect early on if actual wear deviates from the forecast. Detailed information on lubrication and maintenance intervals can be found in the article Roller Guide Maintenance & Lubrication.
Design a roller guide and calculate its service life
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