Precision rail guides Contents SKF – the knowledge engineering company . . . . . . . . . . . . . 4 1.9 Calculation of bearing loads .................... 26 1.9.1 Transfer of external loads to F, F, M, M, M . 26 y z x y z 1 General information . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.9.2 Preload force ......................... 27 1.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.9.3 Transfer of F, F, M, M, M to one load ..... 27 y z x y z 1.2 Features and benefits .......................... 7 1.9.4 Influence of stroke length on equivalent 1.3 Product overview ............................. 8 dynamic load rating .................... 28 1.4 ACS in general ................................ 10 1.9.5 Equivalent dynamic mean load ............ 28 1.5 SKF precision rail guides in kit packaging ............ 12 1.9.6 Maximum resulting load ................. 28 1.6 Technical data ................................ 13 1.9.7 Elaborated equation for the static safety factor 29 1.6.1 Materials ............................. 13 1.9.8 Elaborated equation for the rating life ....... 29 1.6.2 Coating ............................... 13 1.10 Example dimensioning calculation ............... 30 1.6.3 Permissible operating temperatures ......... 13 1.11 Rigidity calculation ........................... 36 1.6.4 Permissible speed and acceleration ......... 13 1.11.1 Determination of elastic deformation 1.6.5 Permissible minimum load ................ 13 using the nomogram ................... 36 1.6.6 Permissible maximum load ............... 13 1.11.2 Determination of resulting deflection of 1.6.7 Friction ............................... 13 a rail guide system ..................... 42 1.6.8 General rigidity behaviour ................. 14 1.11.3 Calculation example for the resulting 1.6.9 Precision classes of rails .................. 14 deflection ............................ 43 1.6.10 Precision of rolling elements ............... 15 1.12 Technical data of precision rail guides with 1.6.11 Dimensional accuracy .................... 15 slide coating ................................ 44 1.6.12 Grading .............................. 15 1.12.1 Surface pressure ...................... 44 1.6.13 Jointed rails ........................... 16 1.12.2 Wear ............................... 44 1.7 Dimensioning of precision rail guide systems. . . . . . . . . 17 1.12.3 Frictional properties .................... 44 1.7.1 The concept of static safety factor calculation .. 17 1.12.4 Temperature range .................... 45 1.7.2 The method of static safety factor calculation .. 17 1.12.5 Chemical and humidity resistance ......... 45 1.7.3 Rating life ............................ 18 1.13 Legend .................................... 46 1.7.4 Rating life calculation .................... 18 1.7.5 Service life ............................ 18 2 Product data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 1.7.6 Cross reference to related chapters .......... 18 2.1 LWR / LWRB ................................ 47 1.8 Determination of effective load ratings ............. 19 2.2 LWRE ..................................... 52 1.8.1 Static and dynamic load ratings given in 2.3 LWRE ACS ................................. 57 the catalogue .......................... 19 2.4 LWRE / LWRB ACSM .......................... 61 1.8.2 Influence of hardness ................... 20 2.5 LWRM / LWRV .............................. 65 1.8.3 Influence of operating temperature ......... 20 2.6 LWM / LWV ................................. 69 1.8.4 Rail guide arrangements ................. 21 2.7 LWM / LWV ACSZ ............................ 73 1.8.5 Rail guide kinematics .................... 21 2.8 LWRPM / LWRPV ............................ 77 1.8.6 Number of rolling elements z, z ........... 24 2.9 Other products .............................. 80 T 1.8.7 General geometry of a rail guide system ...... 25 2.9.1 LWML / LWV .......................... 80 2.9.2 LWN / LWO ........................... 80 2.9.3 LWJ / LWS flat rail guides ................ 80 2.10 GCL / GCLA standard slides ..................... 81 2.11 LZM miniature slide .......................... 86 3 Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90 3.1 Design rules ................................. 90 3.1.1 Designated use ......................... 90 3.1.2 Typical mounting – clamped arrangement .... 90 3.1.3 Accuracy of mounting surfaces ............. 90 3.1.4 End pieces logic ........................ 91 3.1.5 Chamfers on the precision rail guides ........ 92 3.1.6 Tolerance of distance between mounting holes . 92 3.1.7 Calculation of J dimension ................ 92 1 3.1.8 Special mounting screws LWGD ............ 93 3.1.9 Preloading ............................ 94 3.1.10 Tightening torques for mounting screws ...... 94 3.2 Mounting .................................... 96 3.2.1 Important requirements .................. 96 3.2.2 General mounting rules .................. 96 3.2.3 Mounting of rail guides without Anti-Creeping System ................... 96 3.2.4 Mounting of rail guides with Anti-Creeping System ................... 97 3.3 Maintenance ................................. 98 3.3.1 Lubrication ............................ 98 3.3.2 Relubrication interval .................... 98 3.3.3 Repairs ............................... 98 3.3.4 Stationary conditions / shipping / storage ..... 98 3.4 Ordering code ................................ 99 3.5 Specification sheet ............................ 103 3 SKF – the knowledge engineering company From one simple but inspired solution to a misalignment problem in a textile mill in Sweden, and fifteen employees in 1907, SKF has grown to become a global industrial knowledge leader. Over the years, we have built on our exper- Meeting the toughest challenges Working for a sustainable future tise in bearings, extending it to seals, mecha- Our network of knowledge and experience, Since 2005, SKF has worked to reduce the tronics, services and lubrication systems. along with our understanding of how our negative environmental impact from our Our knowledge network includes 46 000 core technologies can be combined, helps operations and those of our suppliers. Our employees, 15 000 distributor partners, us create innovative solutions that meet the continuing technology development resulted offices in more than 130 countries, and a toughest of challenges. We work closely with in the introduction of the SKF BeyondZero growing number of SKF Solution Factory our customers throughout the asset life portfolio of products and services which im- sites around the world. cycle, helping them to profitably and prove efficiency and reduce energy losses, re spon sibly grow their businesses. as well as enable new technol ogies har- Research and development nessing wind, solar and ocean power. This We have hands-on experience in over forty combined approach helps reduce the en vir- industries based on our employees’ know- on mental impact both in our oper ations and ledge of real life conditions. In addition, our our customers’ oper ations. world-leading experts and university part- ners pioneer advanced theoretical research and development in areas including tribol- ogy, condition monitoring, asset manage- ment and bearing life theory. Our ongoing commitment to research and devel opment helps us keep our customers at the forefront of their industries. Working with SKF IT and logistics systems and application experts, SKF SKF Solution Factory makes SKF knowledge and manu facturing expertise Authorized Distributors deliver a valuable mix of product and application available locally to provide unique solutions and services to our customers. knowledge to customers worldwide. 4 Design and develop pecificatio n Manufacture an S d t e Our knowledge SKF Life Cycle st Management – your success n SposuflKa ctFtch feLeosi rf asme fs ussCle y,at csn llueidfs eMat adcaiyvnncaaalnegbc,el eetmdo a eshnneedtrl p vpisi rco oheufosri,wt caa ubwnsldeet o .c amopmperlbysi ntthoee bomeu ram tto eercaehc nho slotagyg e Maintain and repair Operate and monitor In stall and comoisims Bearings Working closely with you SKF is the world leader in the design, development Our objective is to help our customers and manufacture of high performance rolling improve productivity, minimize main ten- bearings, plain bearings, bearing units and housings. ance, achieve higher energy and resource efficiency, and optimize designs for long service life and reliability. Machinery maintenance Condition monitoring technologies and main- Innovative solutions tenance services from SKF can help minimize Whether the application is linear or rotary unplanned downtime, improve operational efficiency and reduce maintenance costs. or a combination, SKF engineers can work with you at each stage of the asset life cycle to improve machine performance by looking at the entire application. This approach Sealing solutions doesn’t just focus on individual components SKF offers standard seals and custom engineered like bearings or seals. It looks at the whole sealing solutions to increase uptime, improve application to see how each com po nent in- machine reliability, reduce friction and power losses, and extend lubricant life. teracts with each other. Design optimization and verification SKF can work with you to optimize current Mechatronics or new designs with proprietary 3-D mod- SKF fly-by-wire systems for aircraft and drive-by- ell ing software that can also be used as a wire systems for off-road, agricultural and forklift virtual test rig to confirm the integrity of the applications replace heavy, grease or oil consuming mechanical and hydraulic systems. design. Lubrication solutions From specialized lubricants to state-of-the-art lubrication systems and lubrication management ser vices, lubrication solutions from SKF can help to reduce lubrication related downtime and lubricant consumption. Actuation and motion control With a wide assortment of products – from actu- ators and ball screws to profile rail guides – SKF can work with you to solve your most pressing linear system challenges. 5 1 General information 1.1 Introduction If cage creeping is likely, in particular when the guide is mounted vertically, preci- As the world’s leading rolling bearing manu- sion rail guides with anti-creeping systems facturer, SKF supplies practically every type (ACS) are an obvious choice, as they will of bearing for rotational and linear motion. eliminate this problem. They are available SKF is therefore in a position, both techni- for nearly all types of rolling elements. cally and economically, to meet almost any For applications characterised by high customer requirement. accelerations or short strokes of high fre- This catalogue covers the entire range of quency, SKF rail guides with slide coating SKF precision rail guides and accessories. are recommended. These rail guides are SKF precision rail guides are highly accurate also suitable for machine tool applications products for linear motion and are ideally where the damping properties of the guides suited for use in a wide variety of machine are of greater importance than is the lower tools, machining centres, handling systems friction of rolling element rail guides. For and special machinery, as well as in meas- those applications where precision rail uring and testing equipment and semi-con- guides are unsuitable, for instance because ductor production machines. of their limited travel, SKF can supply alter- SKF precision rail guides are available in native forms of linear guidance systems, like many different designs, sizes and standard profile rail guides or linear ball bearings. lengths and which incorporate ball, roller or All fast-selling precision rail guides are needle roller assemblies and slide coatings. also available in convenient kit packaging. They are supplied with the required acces- This ensures the complete delivery of all sories for attachment and sealing. The use components including end pieces and of SKF precision rail guides enables the con- screws in one package from stock. struction of economical, clearance-free lin- This catalogue brings together all the ear guides of almost any type and length, basic data that we believe will be of interest according to the building block principle. to customers. For further specialised advice, please contact your nearest SKF sales office. The characteristics of the precision rail guides include: • A constant, high degree of running accuracy. • Low-friction, stick-slip free operation. • High speed of travel. • Low heat generation. • Low wear and high reliability. • High rigidity. • Excellent load carrying capacity. 6 1.2 Features and benefits 1 Cage creep test results Anti-creeping system SKF developed the industry’s first anti-cage-creep solution. It keeps the movement of the cage in the required position at the loaded zone, avoids cage Axial displacement [mm] creep from high operational speed and acceleration to uneven load distribu- 35 tion and weak adjacent parts, and prevents unplanned downtime and addi- 30 tional maintenance. In addition, due to defined cage position, SKF precision rail guides with 25 without anti-creeping system anti-creeping system, or ACS, enable increased accuracy, higher accelera- 20 tions (tested up to 160 m/s2), and reliable vertical installation. 15 10 5 with anti-creeping system 0 0 10 20 30 40 50 60 70 80 90 100 Distance travelled [km] Higher load rating and rigidity Compared to conventional LWR precision rail guides, SKF optimized the inter- nal geometry and developed LWRE precision rail guides for applications that demand robust performance. Part of our modular range, LWRE precision rail guides feature rollers with a 33% larger diameter and utilize the entire roller length than those in LWR rail guides. These LWRE design upgrades fivefolded the load ratings and doubled the rigidity vs. LWR rail guides. In operation, the increased load rating and rigidity helps to increase process stability and reliability, ultimately extending equipment service life and reducing total cost of ownership. Permissible deviation in parallelism between reference surfaces Extreme accuracy and positioning repeatability and raceways Compared to other linear guiding products, precision rail guides provide the highest linear guiding accuracy. Precision rail guides from SKF are available Deviation in parallelism [µm] in three different precision classes to meet a range of requirements for preci- 10 sion. The increased accuracy and repeatability enables higher productivity 9 and product quality in diverse applications, e.g. semi-conductors, machine 8 P10 tools, measurement and testing equipment, and medical equipment. 7 6 5 P5 4 3 P2 2 1 0 100 200 300 400 500 600 700 800 9001 000 Rail length [mm] Modular range With the SKF modular range of precision rail guides, outer rail dimensions B remain the same, but rolling elements are interchangeable to best meet application demands. With this design modularity, customers can easily increase load rating or extend rating life without having to redesign the equipment. The SKF modular range of precision rail guides covers 80% of dimensions on the market. Additionally, the customer can chose between ball assemblies, crossed roller assemblies, crossed roller assemblies with ACS/ A ACSM, needle roller assemblies and slide coatings. 7 1.3 Product overview 8 SKF can offer a large assortment of preci- The following table shows the complete sions († fig . 1). For fast delivery, please sion rail guides († table 1). The different range of SKF precision rail guides, together refer to the rail guides that are available in 1 versions, mainly characterized by their type with all available sizes. The blue shaded areas kit packaging. of rolling elements, are as follows: indicate the sizes included in the Modular Range. Contrary to the current lack of uni- • Ball assemblies of LWRB series. formity within the market, the interchange- • Ball assemblies with Anti-Creeping able precision rail guides of the Modular System of LWRB ACSM series. Range are all within the same outer dimen- • Crossed roller assemblies of standard LWR series. Fig . 1 • Crossed roller assemblies of optimised LWRE series. • Crossed roller assemblies with Anti- Creeping System of LWRE ACS series. • Crossed roller assemblies with Anti- Creeping System of LWRE ACSM series. • Needle roller assemblies of LWRM/LWRV series. Market situation • Needle roller assemblies of LWM/LWV series. • Needle roller assemblies with Anti-Creep- ing System of LWM/LWV ACSZ series. • Slide coating of LWRPM/LWRPV series. SKF modular range Table 1 Product overview Type A Size (A¥B mm) 1 2 3 2211 4 6 9 12 15 B 8,5¥4 12¥6 18¥8 22¥11 25¥12 30¥15 31¥15 40¥20 44¥22 50¥25 58¥28 60¥35 70¥40 71¥36 80¥50 LWRB X X – – – – – – – – – – – – – LWRB ACSM – L – – – – – – – – – – – – – LWR – – X – – – X – X – L – – – – LWRE – – X L X – X – X – – – – – – LWRE ACS – – X L L – X – L – – – – – – LWRE ACSM – – X L L – X – L – – – – – – LWRM / V – – – – – – X – X – – – – – – LWM / V – – – – – X – X – X – L L – L LWM / V ACSZ – – – – – L – L – L – L L – L LWRPM / V – – X – – – X – X – – – – – – X = Prompt delivery in standard lengths (see specific product tables) = Modular range L = Delivery time on request – = Not available 9 1.4 ACS in general Many users are familiar with “cage-creep- LWRE with ACS ing” in conventional precision rail guides. This occurs when the cage moves out of its intended position, adversely affecting performance and possibly requiring service. This effect may occur, for example, as a result of high acceleration, uneven load distribution or vertical mounting. SKF has solved this problem by offering highly sophisticated Anti-Creeping Systems (ACS) for most guiding types. Advantages: • Cage-creeping eliminated. • Suitable for high acceleration, vertical mounting and uneven load distribution. • Increased accuracy due to defined posi- tion of the cage. • Easily interchangeable with standard precision rail guides because they have identical dimensions. LWRE with ACSM • Less downtime and maintenance. LWRE with ACS The original anti-creeping system for all types of LWRE rail guides. LWRE with ACSM Refinement of our own ACS solution led to version ACSM for LWRE rail guides with a maximum length of 400 mm. The cage, with an involute-toothed control gear made of brass, and involute teeth directly machined into the rail, are especially suitable for high accelerations. LWM / LWV with ACSZ For precision rail guides with needle roller cages, SKF can offer version ACSZ. Both rails are equipped with gear racks made of steel. The cage carries two steel LWM / LWV with ACSZ control gears that help to ensure the correct cage position. 10