Examples of selecting a ball screw thk technical support. Lead screws and ball screws lie at the heart of screw driven stages and actuators. Department of mechanical engineering me en 7960 precision. Thomson screw product engineer, jeff johnson, overviews the anatomy of ball screws, the installation of ball screws and reloading ball bearings into a. Manufacturers are responding with product sizing and selection tools as well as services for custom designs. Determine the application parameters interim selection of ball screw specifications evaluation of various basic safety factors evaluations based on required performances.
Ball screws selection guide support units selection processdp. Selection of lead accuracy of ball screws 1 select the ball screw that satis. Ball screw drive is a popular linear actuator introduction the ball screw drive is an assembly that converts rotary motion to linear motion and vice versa. Ball screw selection and calculations university of utah. Selection of lead accuracy of ball screws 1 select the ball screw that sa. A highspeed ball screw drive system generates more heat and results in greater positioning error, adversely affecting the accuracy of machined parts. Selection of the standard to be used is an agreement between. Proper selection and application of lubricants also affects contamination, a leading cause of premature ball screw failure. Ball selection is a lowcost method that involves using preselected, oversized ball bearings to create four points of contact between the nut and screw. Selection procedure first, determine certain features of the design, such as drive mechanism, rough dimensions, distances moved, and positioning period.
Aug 24, 2012 ball recirculation inside the ball nut can affect precision and repeatability. Additionally, based on the list axial clearances of ball screws on p. By providing steel balls in between the screw shaft and the nut grooves, and the balls roll on the grooves i. As a result, ball nuts are available with a range of preload options to reduce or remove the axial play as they rotate around the screw. We offer a complete selection of ball screws, from miniature to ultralarge sizes, for machine tools, injection molding machines, and. Find out how you can install the nsk ball screw, essential for linear motion, using proper procedure. Proper ballscrew selection involves a number of design and application considerations. Ball screw examples of selecting a ball screw highspeed transfer equipment horizontal use selection conditions table mass m 1 60kg work mass m 2 20kg stroke length s mm maximum speed v max 1ms acceleration time t 1 0.
Ball screw shaft kgs series kgs precision rolled metric ball screw shafts are. Screws and support units from the previous calculations, the best selection of the ball screw is part no. With the worlds leading ball screw, nsk has been contributing to industrial growth. The circuit is closed by a ball return cap in the nut a balls to cross over adjacent ball tracks. Precision machine partsproductdaiichi sokuhan works co. Speed measured in inches or millimeters per minute. Where is torque applied to screw or nut, is linear force applied, is ball screw lead, and is ball screw efficiency.
Selection procedure lejs seriesspage 2 lejsm page 601 lejb seriesspage 7 11lejs sseries page 533 electric actuatorhigh rigidity slider type ac servo motor lecs series ball screw drivelejsm series belt drivelejb series ball screw drive11lejs series clean room specification model selection. Therefore, proceed to the following investigation using this size of ball screw. Nsk ball screws we offer a complete selection of ball screws developed through cuttingedge tribology friction control technology. A ball screw is a device comprised of a shaft and a nut where either of which can be the traversing component. Maximum load at which a lead screw assembly should be operated. For this purpose, a tool that assists designers in making quick and reliable selections is an absolute must. The selection of the correct ball screw and nut for a particular application involves five interrelated factors. Rockford ball screw products are built to the highest performance design standards. Double check your applications travel requirements, and the screw lead. Ballscrews, also called a ball bearing screws, recirculating ballscrews, etc. Dimensions of the ball screw k3 k 3 typesofballscrews k2 1. Ball screw, selection procedure, design calculation, application etc. The balls in this design tr whole circuit of the ball tracks within the nut length.
Precision machine parts are manufactured by applying the precision processing technology of issoku, an expert in precision measurement. Ball screw selection and calculations me en 7960 precision machine design topic 4 me en 7960 precision machine design ball screw calculations 42 ball screw selection criteria maximum rotational speed resonance bending of threaded shaft dn value applied load thrust force required torque stiffness ball screw selection ball screw life. A ball screw transforms rotational motion into transitional motion. This allows for better repeatability, for example, because no motion is lost from the clearance in the balls as they reengage. Specifying, selecting and applying linear ball screw drives. Machine design resources gear design and engineering. Our ball screw and acme screw product lines feature over 80 standard models and one of the largest inventories in the industry. National and international standards are used to standardize the definitions, environmental requirements, and test methods used for ball screws. The thread design is a right hand, gothic arch profile. Ball screws work similarly to ball bearings, where hardened steel balls move along an inclined. This allows for a heavier load, but the friction from the contact can reduce the life of the bearings. Before attempting to determine the ball screw and nut combination, the following values must be known. The optional inputs make it possible for the designer to.
The design load, system orientation, travel length, required life, and required velocity, are used to determine the diameter and lead of the ball screw assembly. Duffnorton offers ball nuts and also bronze or plastic acme nuts. Ball screw leadcm moment of inertia exerted on cylinders as screws and cylinders such as gears calculation of j1j4. By ball circulation method, the ball screws are divided into returnpipe type. Selection and installation of hiwin ballscrews 1 a ballscrew must be thoroughly cleaned in white spirit and oil to protect against corrosion. Since the ball retul ball return cap screw shaft ball nut ballscrew, f ball. Dynamic load rating is the maximum load which a ball bearing screw assembly can maintain for 1. Rexroth precision ball screw assemblies provide technical designers with diverse solutions for positioning and transport tasks with driven screws or also with driven nuts. New tools, services aid ball screw selection and design. Available fully machined to bosch rexroth standard. This is not surprising, because screws, and ball screws in particular, are workhorses of linear motion, with a range of styles, sizes, and performance capabilities that covers just about any application an engineer or designer can come up with. Compared with a conventional sliding screw, this product has drive torque of onethird or less, making it most suitable for saving drive motor power. To make the very best selection of a ball screw, the designer should specify such critical parameters as the load profile, the linear or rotational speed, the rates of acceleration and deceleration, the cycle rate, the environment, the required life, the lead.
Ball screws are known to encounter both compression and tensile loads. Motor sizing calculations this section describes certain items that must be calculated to find the optimum motor for a particular application. Ball screws, nuts and end bearings available in various diameter and lead combinations for complete design flexibility. Ball screws precision machine components products nsk. Consider the applicability of the following items to. Selecting and sizing ball screw drives letter thomson linear. Types of ball screws classification of ball screws for ball screws, a broad array of types are offered as standard so that the optimal product can be selected to meet diversified applications. To make the very best selection of a ball screw, the designer should consider critical parameters such as the load cycle. Insidepenton com electronic design adobe pdf logo tiny. Ball recirculation hole return tube screw shaft ball nut screw shaft end deflector ball screw b12. Feb 14, 2018 correct installation of nsk ball screw is important for long life, low friction and high accuracy. Ball screw design equations and selection criteria. Although lead screws are often seen as less expensive substitutes for ball screws, making a decision on which type of screw to use is a lot more complicated than focusing solely on cost. The ball screw assembly that provides the specified load capacity and life required for a specific application must be selected through an.
Download the rbs catalog now or request a printed version to be mailed. The fundamentals of ball screws and ball screw selection by. Therefl nut with the same load capacity as the conventional design c. Ball screw selection procedure basic ball screw selection procedure and required evaluation items are shown below. Precision rolled ball screw drives schaeffler group. Technical calculation selection method ball screws. If the rolling elements do not rotate all the way, but only halfway, and if this minute stroke is repeated, lubricant disappears from the contact surface of rolling elements and raceways, and metallic parts directly make contact each other. But because the ball nut is only one component in the ball screw assembly, and its rigidity is relatively high compared to the other components, increasing the preload from 3 percent to 5 percent, for example has a minimal effect on the rigidity of the assembly. Consider the applicability of the following items to the conditions con.
One of the first choices engineers must make is whether to use oil or. Extensive engineering expertise and a stateoftheart manufacturing facility ensure top performance and reliability in our products. The ball screw is a highefficiency feed screw with the ball making a rolling motion between the screw axis and the nut. Ball screw selection the ball screw assembly that provides the specified load capacity and life required for a specific application must be selected through an iterative process. Steel ball end cap screw shaft jlation type return caps ball nut the nut body as a through hole. Selecting a lubricant for ball screws machine design. Specifying, selecting and applying linear ball screw. Rockford ball screw s catalog contains all of the uptodate resources available on our product lines and applications, as well as corresponding technical information. Ball lead screw motor sizing forms calculate the necessary torque, speed, stopping accuracy and system inertia important when selecting a proper motor for the application.
The side contact type that uses the spiral structure of a screw and the rolling contact type that has a rapid and light movement and enables accurate positioning through the use of a ball between the screw shaft and a nut, these products have an. With a growing number of product options, engineers are looking for new tools and services to help simplify the ball screw selection process. Trichloroethylene is an acceptable degreasing agent, ensuring the ball track free from dirt and damage paraffin is not satisfactory. A682 features and types ball screw features of the ball screw driving torque one third of the sliding screw with the ball screw, balls roll between the screw shaft and the nut to achieve high efficiency. Nsk ball screws were developed through cuttingedge tribology friction control technology, and nsk manufactures the largest volume in the world with its outstanding production and quality control techniques. The steel balls make only one revolution arounl spindle.
Specifying, selecting and applying linear ball screw drives letter. Ball screw assembly kgt a precision rolled ball screw assembly kgt consists of at least one kgf or kgm nut on a screw shaft kgs. Only basic selection parameters are included in this chapter. May, 2017 one of the most popular subjects on this site is ball screwsespecially the topic of how and when to select a ball screw. Requires ball screw operating load capacity of 1,561 lbs. The selection of ballscrews is a multicriteria problem that can be very time consuming and tedious. They feature a number of variables, including type of nut, screw diameter, screw pitch, material, etc. Higher preload also correlates with higher nut rigidity, which improves the rigidity of the complete screw assembly. Design calculation of precision ball screw for portable cnc. Kgt ball screw assemblies are available in various metric diameterlead combinations. Problem 1 in this exercise you are asked to prepare an excel spreadsheet that calculates all relevant selection criteria.
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