Part i - spindle facts

More documents

Recommendations

Info

Bearing Contact Angle Angular contact ball bearings are manufactured to a specification that includes a contact angle. The contact angle is the nominal angle between the ball-to-race contact line and a plane through the ball centers, perpendicular to the bearing axis. The contact angle determines the ratio of axial to radial loading possible, with radial loading being the primary benefit. Typically, contact angles of 12º, 15º, and 25º are available. The lower the contact angle, the greater the radial load carrying capacity, the higher the contact angle the higher the axial loading capacity will be. Therefore, it may be desirable to use a bearing with a contact angle of 25º for a spindle that will be used primarily for drilling, and a contact angle of 15º for a spindle that will primarily be used for milling. Bearing Precision Figure 5. Different Contact Angles All precision bearings are manufactured to a tolerance standard. The tolerances for dimensional, form and running accuracy of High precision Spindle ball bearings are specified in international (ISO 492) and national standards (DIN 620). The most commonly used standard in the United States is the ABEC standard (America Bearing Engineers Committee) This standardization has been accepted by the American National Standards Institute (ANSI) conform essentially with the equivalent standards of the International Organization for Standardization (ISO). ABEC standards define tolerances for major bearing dimensions and characteristics. They are divided into mounting dimensions (bore, I.D. and width) and bearing geometry. Accuracy ratings range from a low of ABEC 1, for a general purpose bearing, to a high of ABEC 7 and ABEC 9, which describes a high precision bearing suitable for use in a high speed spindle. Typically, spindle bearings are manufactured with geometry accuracy of ABEC 9, to provide minimum run out and rotational accuracy. Bore, O.D., and width are manufactured to ABEC 7, which allows for a more reasonable fitting and installation. The precision of a spindle bearing does affect the guiding properties or life, especially with applications at max. speed. The relationships between the various standards are explained below. ISO DIN AFBMA class 4 P4 ABEC7 class 2 P2 ABEC9 Table 1. - 7 -
Bearing Preload Angular contact ball bearings are available with a choice of pre-loading magnitude, typically designated as light, medium and heavy. Light pre-loaded bearings are designed to allow maximum speed and less stiffness. Light pre-loaded bearings are often used for very high speed applications, where cutting loads are also light, and top RPM is needed. Heavy pre-loading allows less speed, but higher stiffness. In order to provide the required load carrying capacity for a metal cutting machine tool spindle, several angular contact ball bearings are used together. This way, the bearings can share the applied loads, and increase the overall spindle stiffness. The bearings can be installed several ways, depending upon the desired characteristics. Angular contact ball bearings must be pre-loaded in order to provide axial and radial capabilities. One simple way to do this is to mount the bearings in groups of two or three, such that the preload is correctly applied to the bearings. This is possible by using duplex bearings, which are manufactured for this purpose. The inner or outer bearing races are ground, such that when clamped together the bearings will have the proper amount of pre-load. Bearing Mounting Configurations Face to Face Configuration Figure 6. FACE TO FACE DF-Mounting If the bearings are mounted face to face, this is referred to as "Face-to Face" or "X" configuration. In this configuration, the outer races are relieved When the outer races are clamped together, the relief clearance is eliminated, resulting in the correct preload. This mounting technique is not very common; however, it does provide the proper pre-loading, such that the bearing pair is capable of withstanding both axial and radial loading. - 8 -
Page 2 and 3: PART I - SPINDLE FACTS 1. Introduct
Page 4 and 5: 2. Precision Spindle Design 2.1 Lis
Page 6 and 7: otate up to the maximum speed, and
Page 10 and 11: Back to Back Configuration The most
Page 12 and 13: Motor-Spindle with Tandem Bearing P
Page 14 and 15: Bearing Lubrication Methods Angular
Page 16 and 17: There are many oils available on th
Page 18 and 19: 2.5 Spindles with Integral Motors S
Page 20 and 21: Synchronous Spindle Motor : AC asyn
Page 22 and 23: The synchronous motor built in spin
Page 24 and 25: Torque: This is the most critical a
Page 26 and 27: 2.7 Spindle Cooling Systems Heat is
Page 28 and 29: 2.8 Seal Types High precision beari
Page 30 and 31: The values are valid for spring-loa
Page 32 and 33: and the influence of higher tempera
Page 34 and 35: 2.9 Tool Retention System A high sp
Page 36 and 37: Assuming that equivalent force is a
Page 38 and 39: of tooling. This means that users m
Page 40 and 41: HSK-Clamping Unit / Design B • A
Page 42: 3. Conclusion and Future trends A h
Page 45 and 46: Dynomax’s dedication to new spind

Part i - spindle facts

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?