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Note: other names for Roller bearings are Track-Rollers, Track-Followers, and Cam-Followers.
To Calculate Roller Life, you must :
Parameters tab STEP 1:Enable Show Roller and Cam Life STEP 2:Enter a Safety Factor (CAM) The Roller's Safety-Factor is equal to the Square of the Cam's Safety-Factor. See Parameters tab > Enable Lifetimes, Edit Safety-Factor Roller Life tab STEP 3:Select a Roller bearing manufacturer and Roller bearing If you Enable ISO 281 Modification Factors. STEP 4:Select or enter a Reliability Factor STEP 5:Enter the Oil Operating Temperature, and Viscosity at two other Temperatures (usually 40ºC and 100ºC) STEP 6:Enter the Lubrication Type and select the Contamination Level. Review the Roller's Lifetime |
2D-Cam dialog-box > Roller Life tab
Select a Manufacturer and Bearing Part-Number of Parameter
STEP 1: Select a Roller bearing Manufacturer
STEP 2: Select a Roller Bearing
You can see immediately the Basic Rating Life, in the L10 for Roller: Part Number separator. |
To see these factors, enable the ISO 281 Modification Factors The data allows us to calculate the and modification factors. ![]() ISO 281 Modification Factors
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Filtration Ratio and Filtration Code |
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; ISO 4406 Code; -/13/10 |
; ISO 4406 Code; -/15/12 |
; ISO 4406 Code; -/17/14 |
; ISO 4406 Code; -/19/16 |
Oil Filtered Off-Line
Select, in the drop-down list box, the Cleanliness Codes, according to ISO 4406, that best represents the anticipated operating condition.
Filtration Code |
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ISO 4406 Code; -/13/10 |
ISO 4406 Code; -/15/12 |
ISO 4406 Code; -/17/14 |
ISO 4406 Code; -/19/16 |
ISO 4406 Code; -/21/18 |
Grease
Select, in the drop-down list box, the Level of Contamination that best represents the anticipated operating condition.
Level of contamination |
Operating conditions |
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High cleanliness |
Very clean assembly with careful flushing; very good sealing in relation to operating conditions; re-greasing carried out continuously or at short intervals Sealed bearings, greased for life with effective sealing capacity in relation to operating conditions |
Normal cleanliness |
Clean assembly with flushing; good sealing in relation to operating conditions; re-greasing according to manufacturer’s specification Sealed bearings, greased for life with proper sealing capacity in relation to operating conditions, e.g. shielded bearings |
Slight to typical contamination |
Clean assembly; moderate sealing capacity in relation to operating conditions; re-greasing according to manufacturer’s specifications |
Severe contamination |
Assembly in workshop; bearing and application not adequately washed after mounting; poor sealing capacity in relation to operating conditions; re-greasing intervals longer than recommended by manufacturer |
Very severe contamination |
Assembly in contaminated environment; inadequate sealing; long re-greasing intervals |
These parameters are calculated automatically when you select a Roller, and/or enable ISO 281 factors. ![]() Life for the seleced Roller(Cam-Follower Bearing) Basic Rating Life,This states that if the bearing load, , is equal to the Basic Dynamic Load Rating, , then there is a 90% reliability that the bearing will survive at least 1 million rotations, if manufactured with commonly used high quality material, of good manufacturing quality, and operating under conventional operating conditions.
Modified Rating Life,Two factors must be calculated: • - a factor for Reliability - see below • - a factor calculated with a System Approach - see below
Operating LifeThe operating life is defined as the life actually achieved by the bearing. It may differ significantly from the calculated life. The operating life cannot be calculated! Due to the wide variety of possible installation and operating conditions, it is not possible to precisely predetermine the operating life. The most reliable way of arriving at a close estimate is by comparison with similar applications. Possible factors influencing the operating life
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The Reliability Factor is constant for all application conditions. The drop-down list has the standard Reliability Factor percentages (90 to 99.95%), as given in ISO 281. Modified Life Rating (at reliability) (millions of revolutions)
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The Life Modification factor, , is a complex interaction between Oil or Grease Viscosity Grade, Filtration, Contamination, Oil Operating Temperature, the Fatigue load capacity of the Roller, the rotational-speed of the Roller, and the diameter of the Roller. The equations given in ISO 281 to calculate these factors are empirical, quite complex, and interrelated. All of the factors, except , are a function of the bearing speed and bearing load. Since, in a cam mechanism, the speed and load on the roller are continually changing, we must calculate the factors at each step and integrate them to find their equivalent values.
Fatigue Limit of Bearing. () If the Fatigue Limit of the Roller bearing is not in the Catalogue, we calculate its value. In analogy to the static load rating in ISO 76, is defined as the load at which the fatigue stress limit, , is just reached in the most heavily loaded raceway contact. For bearing steels, this is typically 1500MPa. The ratio can be approximated by the ratio Contamination Factor, To calculate the Contamination Factor, , you must select the Lubrication-Type and its Contamination Level. The Contamination Level is also a function of the Viscosity Ratio - see below. Lubrication Type We can choose from three Lubrication-Types: •Circulating oil with the oil filtered in-line before being supplied to the bearings. •Oil bath lubrication or circulating oil lubrication with off-line filters. •Grease lubrication. Oil Filtration There are three types of filtration •In-Line Filtration •Off-Line Filtration Grease Contamination Level For grease, the level of contamination is a function of the •assembly conditions for the machine/mechanism, the •operating conditions, and the •protection from dirt ingress into the Grease. Grease Contamination Each Lubrication-Type has a list of Contamination Levels from which you can choose.
Contamination Levels ISO 4406 The table below provides scale values as a function of particle concentration (particles/ml) - it is from ISO 4406 A three number code defines the amount of contamination at 4, 6, and 14 μm. Each time a scale number increases the quantity of particles is doubled. Example: ISO code = 21 / 19 / 17 This Contamination Class describes a fluid containing: •between 10 000 and 20 000 particles ≥ 4 μm(c) per 1 ml •between 2 500 and 5 000 particles ≥ 6 μm(c) per 1 ml •between 640 and 1 300 particles ≥ 14 μm(c) per 1 ml If the leading number is missing, then that size of particle is not counted.
Viscosity-Ratio, The viscosity ratio, , is an indication of the quality of lubricant film formation. The effectiveness of the lubricant is primarily determined by the degree of surface separation between the rolling contact surfaces. If an adequate lubricant separation film is to be formed, the lubricant must have a given minimum viscosity when the application has reached its operating temperature. The condition of the lubricant separation is described by the viscosity ratio, , as the ratio of the actual kinematic viscosity, , to the reference kinematic viscosity,. The kinematic viscosity, , is considered when the lubricant is at operating temperature.
- Reference Kinematic Viscosity. is the viscosity that should separate the rolling elements from the raceways, to give a Film Thickness Ratio, . It assumes that the oil is a mineral oil, with a Viscosity-Index of approximately 100. Synthetic Hydrocarbon SHC type synthetic oils can be used. - Viscosity at Operating Temperature We calculate the viscosity at the Operating Temperature from the viscosity, , at two other temperatures. The Viscosities at ( ) and ( ) are usually specified on the data sheet of the lubricant. If you have manufactured the internal and/or external raceways, then it is better to calculate the Viscosity Ratio from:
Notes: A Viscosity-Ratio less than 0.1 is outside of the limits of ISO 281. It is very close to metal-to-metal contact. A Viscosity-Ratio greater than 4 is the maximum that can be used by ISO 281. However, ISO 281 simply states that the Viscosity-Ratio is equal to 4 if it is actually greater than 4. A viscosity-ratio greater than 4 is getting too high for the bearings. The needles or balls may slide and refuse to roll in the 'thick-oil', or the oil may churn and increase the oil and bearing temperatures. A viscosity of approximately 2-3 is approximately ideal. |