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- Evolmec S.r.l.
- High precision bearings for combined loads - EVOLMEC - EVMU - 07.2021
High precision bearings for combined loads - EVOLMEC - EVMU - 07.2021
High precision bearings for combined loads - EVOLMEC - EVMU - 07.2021
- Features: The EVRT and EVRTS series are ready-to-fit, high precision bearings with identical mounting dimensions. They are preloaded radially and axially after fitting.
- Applications: EVRT series is suitable for low-speed applications like indexing tables, while EVRTS is ideal for direct drive axes due to high limiting speeds and low frictional torque.
- Components: Include axial needle or cylindrical roller assemblies, outer rings, and shaft locating washers. They are easy to fit due to fixing holes.
- Sealing and Lubrication: Supplied without seals and lubricated with SHELL grease, suitable for temperatures between -30°C and +120°C.
- Features: The EVLDF series is designed for high-speed applications with long operating durations, characterized by high tilting rigidity and low friction.
- Components: Comprise a single-piece outer ring, two-piece inner ring, and ball and cage assemblies with a 60° contact angle.
- Sealing and Lubrication: Have sealing shields on both sides and are lubricated with SHELL grease, suitable for temperatures between -30°C and +120°C.
- Basic Rating Life: Load carrying capacity and life must be checked for radial and axial components.
- Static Load Safety Factor: Indicates security against permanent deformations, recommended to be > 4 for machine tools.
- Limiting Speeds: Guidelines provided for different series, with specific conditions for high-speed operations.
- Design Regulations: Recommendations for minimizing heat flow and ensuring rigidity in rotary table designs.
- Temperature Management: Importance of managing temperature distribution in rotary axis systems to prevent deformation and ensure accuracy.
- Bearing Preload: Bearings are clearance-free and preloaded after fitting, with temperature differences affecting preload and operating life.
- Frictional Torque: Influenced by lubricant viscosity, quantity, and bearing preload. Initial operations may exhibit increased frictional torque.
- Relubrication: Guidelines for relubrication intervals and quantities, with emphasis on avoiding overheating due to overlubrication.
The document discusses the impact of washer thickness and geometrical accuracy on the frictional torque of axial/radial bearings, specifically EVRT, EVRTS, and EVLDF series. Frictional torque values are determined at a measurement speed of n = 5 min-1. Deviations in tightening torque of fixing screws can significantly affect preload and frictional torque, with potential increases by a factor of 2 to 2.5 at higher speeds.
Design and Construction:
Geometrical defects in screw mounting surfaces can influence running accuracy and preload. The adjacent construction must meet specific tolerance requirements to ensure optimal bearing performance. The document provides detailed tables for tolerance classes and maximum corner radii for fit surfaces.
Fitting and Mounting:
Recommendations for fits include transition fits, clearance fits, and interference fits, depending on the bearing series and application. The document emphasizes the importance of correct fit to avoid increased friction, heat generation, and reduced bearing life. Specific guidelines are provided for shaft and housing fits, including tolerance zones and dynamic characteristics.
Accuracy and Rigidity:
The document outlines the importance of static rigidity and its influence on machining accuracy. It provides rigidity values for complete bearing positions, considering deflection and deformation. Dimensional tolerances are based on tolerance class P5, with geometrical tolerances corresponding to P4 according to DIN 620.
Technical Features:
Details on mounting dimensions, L-section ring configurations, and the impact of support rings on rigidity and frictional torque are provided. The document also includes instructions for tightening fixing screws in a crosswise sequence to specified torques to ensure proper bearing function.
- Load Capacities: Crossed roller bearings can handle axial loads (Fa), radial loads (Fr), and tilting moments (MK).
- Lubrication: Bearings can be lubricated with oil or grease. Oil lubrication is suitable for speeds up to 8 m/s, while grease lubrication is recommended for speeds up to 4 m/s.
- Operating Temperature: Suitable for temperatures ranging from -30°C to +80°C.
- Shim Thickness and Preload: The required shim thickness (X) is calculated using the formula X = X1 - A - V, where X1 is the provisional shim thickness, A is the measured axial internal clearance, and V is the preload.
- Rigidity: High axial and radial load carrying capacity due to the large number of rollers and line contact with raceways.
- Sealing: Bearings are open design, and sealing arrangements can be customized within the adjacent construction.
- Grease Lubrication: Use high-quality lithium soap grease, such as SHELL GADUS S5 V100 2. For vertical axes, a baffle plate is recommended to minimize grease escape.
- Oil Lubrication: Suitable oils include CLP to DIN 51517 or HLP to DIN 51524 with viscosity classes ISO VG 46 to ISO VG 68.
- Static Load Safety Factor: Check the static load safety factor using equivalent static operating values like bearing load (Foq) and tilting moment load (Moq).
- Dynamic Load Calculation: The equivalent dynamic bearing load (P) is calculated based on axial and radial forces.
- Preload Force: Calculated differently based on whether Ka is less than or greater than 2.114 * FV.
- Mounting Tolerances: Inner rings have a loose fit, while outer rings have a tight fit. Specific tolerances are provided for shaft and housing diameters.
- Fixing Screws: Use screws of grade 10.9 or 12.9 for securing bearing rings. Avoid spring or split washers.
- Fitting Guidelines: Ensure clean and burr-free surfaces, lightly oil or grease seating surfaces, and avoid direct blows on bearing rings during installation.
- Running Tolerances: Based on DIN 620-2 and DIN 620-3, with main dimensions produced to tolerance P5.
- Dimensional and Runout Tolerances: Detailed tables provide specific tolerances for both metric and inch-sized bearings.
The document outlines the dimensional tolerances and runout specifications for bearings in both metric and inch sizes. Key parameters include outer diameter deviation, width deviation, radial runout, and axial runout. The tolerances vary based on the size range of the bearings, with specific upper and lower limits provided for each size category.
Dimensional Tables for Thrust Crossed Roller Bearings:
The document includes detailed dimensional tables for various series of thrust crossed roller bearings, such as EVZ 98, EVZ 69, EVZ 26, and EVXR series. These tables provide critical information on main dimensions, mounting dimensions, basic load ratings, limiting speeds, axial spring constant, and mass. The tables also specify the initial grease quantity and preload force where applicable.
Quality and Standards:
EVOLMEC products comply with international quality standards, specifically ISO 9001:2015. This ensures high-quality processes and products tailored to meet client needs.
Contact Information:
The document provides contact details for EVOLMEC, including their head office and registered office addresses in Italy, along with a telephone number and email address for inquiries.
Catalog excerpts
High precision bearings for combined loads
Open the catalog to page 1
Axial/radial bearings Axial angular contact ball bearings Features Areas of application Axial/Radial Bearings Axial angular contact ball bearings Suffixes for available designs Basic rating life Static load safety factor Static limiting load diagrams Limiting speeds Temperature distribution in the rotary axis system Design regulations Bearing preload Frictional torque Relubrication and initial operations Design of adjacent construction Fitting Static rigidity Accuracy Dimensional tables - EVRT Series Dimensional tables - EVRTS Series Dimensional tables - EVLDF Series Thrust crossed roller bearings...
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Axial/radial bearings - Axial angular contact ball bearings Axial/radial bearings - Axial angular contact ball bearings Technical features Technical features Axial/radial bearings Axial angular contact ball bearings Axial/radial bearings EVRT and EVRTS and axial angular contact ball bearings EVLDF are ready-to-fit high precision bearings for high precision applications with combined loads. Axial/radial bearings EVRT and EVRTS have an axial component and a radial component. Axial angular contact ball bearings EVLDF comprise a single-piece outer ring, a two-piece inner ring and two ball and cage...
Open the catalog to page 3
Axial/radial bearings - Axial angular contact ball bearings Axial/radial bearings - Axial angular contact ball bearings Technical features Technical features Basic rating life Static limiting load diagrams The load carrying capacity and life must be checked for the radial and axial bearing component. The static limiting load diagrams can be used: Please contact our technical department in order to check the basic rating life. The speed, load and operating duration must be given. • For rapid checking of the selected bearing size under predominantly static load • For calculation of the tilting...
Open the catalog to page 4
Axial/radial bearings - Axial angular contact ball bearings Axial/radial bearings - Axial angular contact ball bearings Technical features Limiting speeds In bearing selection, the following guidelines and the limiting speeds must be observed, see dimension tables. If the environmental conditions differ from the specifications in relation to adjacent construction tolerances, lubrication, ambient temperature, heat dissipation or from the normal operating conditions for machine tools, the stated limiting speeds must be checked. Please contact us. Axial/radial bearings EVRT Axial/radial bearings...
Open the catalog to page 5
Axial/radial bearings - Axial angular contact ball bearings Axial/radial bearings - Axial angular contact ball bearings Technical features Technical features Frictional torque Guide values for frictional torque MR Relubrication and initial operations Initial operations The bearing frictional torque MRL is influenced primarily by the viscosity and quantity of the lubricant and the bearing preload: The stated frictional torques MR are statistically determined guide values for bearings with grease lubrication after a grease distribution cycle (Figure 14 - page 11). Figure 11 shows measured frictional...
Open the catalog to page 6
Axial/radial bearings - Axial angular contact ball bearings Axial/radial bearings - Axial angular contact ball bearings Technical features Technical features Design of adjacent construction Geometrical defects in the screw mounting surfaces and fits will influence the running accuracy, preload and running characteristics of the bearing arrangement. The accuracy of the adjacent surfaces must therefore be matched to the overall accuracy requirement of the subassembly. The tolerances of the adjacent surfaces must lie within the running tolerance of the bearing. The selection of fits leads to transition...
Open the catalog to page 7
Axial/radial bearings - Axial angular contact ball bearings Axial/radial bearings - Axial angular contact ball bearings Technical features Technical features Fit selection depending on the screw connection of the bearing rings Geometrical and positional accuracy of the adjacent construction If the bearing outer ring is screw mounted on the static component, a fit seating is not required or a fit seating can be produced as stated, see tables, pages 14 and 15. If the values in the table are used, this will give a transition fit with a tendency towards clearance fit. The values given in the following...
Open the catalog to page 8
Axial/radial bearings - Axial angular contact ball bearings Axial/radial bearings - Axial angular contact ball bearings Technical features Mounting dimensions H1 and H2 If the height variation must be as small as possible, the H1 dimensional tolerance must conform to the tables, pages 18 and 19, and Figure 16. The mounting dimension H2 defines the position of any worm wheel used, Figure 16 and Figure 17 L-section ring with support ring. Technical features In the case of EVRT...VSP, the L-section ring must also be axially supported over its whole surface in order to achieve the stated rigidity...
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Axial/radial bearings - Axial angular contact ball bearings Axial/radial bearings - Axial angular contact ball bearings Technical features Technical features EVLDF Dimensional tolerances and mounting dimensions The dimensional tolerances are derived from tolerance class P5. Dimensional tolerances The diameter tolerances stated are mean values in accordance with DIN 620. The geometrical tolerances correspond to P4 in accordance with DIN 620, see table. Mounting dimensions EVLDF Dimensional tolerances and mounting dimensions The bearing bore in series EVRT and EVRTS may be slightly conical in the...
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Axial/radial bearings - Axial angular contact ball bearings Axial/radial bearings - Axial angular contact ball bearings Dimensional tables Dimensional tables EVRT Series Axial-radial bearings, double direction Hole pattern ① Two retaining screws For EVRT 80 and EVRT 100 ② Screw counterbores open 5) Fixing holes Inner ring Outer ring 1) Including retaining screws or threaded extraction holes. Rigidity of bearing position Rigidity of rolling element set 2) Tightening torque for screws to DIN 912 (UNI 5931), grade 10.9. 3) Rigidity values taking account of the rolling element set, the deformation...
Open the catalog to page 11
