Ball Screw & Nut Part Number Description

Transcription

1 Ball Screws & Nuts A Ball Screw is a threaded shaft that provides a spiral raceway for the ball bearings assembled in a nut. This combination provides a precision screw to enable controlled rotational motion to be converted into linear motion. Ball Screws are able to withstand high thrust loads with minimal internal friction. They are made to close tolerances and are therefore suitable for use in applications where high precision is necessary. While reducing friction, Ball Screws can operate with some preload, effectively eliminating backlash between input rotation and output linear motion. This feature is essential when they are used in computer-controlled motion-control systems e.g. CNC machines tools. The four preload classes available in our standard nuts are P0 With Backlash, P1 No Backlash, P2 Light Preload and P3 Heavy Preload. These low friction Ball Screws yield high mechanical efficiency compared to other alternatives. A typical Ball Screw may be 90% efficient, versus 50% efficiency for a trapezoidal thread of equal size. This low internal friction also means Ball Screws can be back driven (depending upon their lead angle) and therefore are usually unsuitable for hand operated machine tools, in which case trapezoidal thread spindle is the better choice. Ball Screws are fabricated as either ground or rolled screw shafts. Although Ground Ball Screw is designed for the highest precision requirements, Rolled Ball Screw, which is less precise and considerably less expensive, is still a mechanically efficient product to be considered. Rolled Ball Screw can have positional precision as low as 0.003mm over 300mm of travel for the highest precision grade (C0) and 0.05mm for the same length of travel for the lowest grade available (C7). Whether using Ground or Rolled Ball Screw great care is needed to avoid contamination by dirt and other abrasive particles so as to maintain the inherent accuracy and ensure long life. This is easily and simply achieved by using rubber or leather bellows to completely or partially enclose the working surfaces. 286

2 a Ball Screw & Nut Part Number Description 2R25-05A2-2-FSED C 7 - R-P2 Axial clearance and preload code: PO : with backlash, P1 : No-backlash, P2 : light preload, P3 : heavy preload R: Rolled ball screw G: Ground ball screw Accuracy grade code: C0, C1, C2, C3, C5, C7 (more details see pg. 295) Overall length of shaft (mm) Thread length (mm) Flange cut type: N : Full flange S : Flange cut on one side D : Flange cut two sides Circuit Type: W: External type U : Internal type DIN69051 I : Internal circulation E : High lead type K : Miniature type C : Low noise type Y : Cylindrical type (with keyway) Nut type: S : Single nut D : Double nut Flange: F : with flange R : without flange X : special flange Number of nuts on one screw shaft Quantity of circulation tubes Effective ball circuits: T : 1 circuit A : 1.8 circuits B : 2.5 circuits C : 3.5 circuits (mm) Screw nominal O.D. Thread direction: R : right, L : left Number of threads 287

3 Type FSU - flanged single nut, internal circuit type DIN69051 Type FSI - flanged single nut, internal circulation 288

4 Type FDU - flanged double nut, internal circuit type DIN69051 Type FDI - flanged double nut, internal circulation 289

5 Type FSW - flanged single nut, external circuit type 290

6 Type FDW - flanged double nut, external circuit type 291

7 Type FSC - flanged single nut, low noise type Left helix option 292

8 Type FSE - flanged single nut, high lead type Type RSW - single nut, external circuit type 293

9 Type RSU - single nut, internal circuit type DIN69051 Type FSK - flanged single nut, miniature type 294

10 295

11 Selection of Nut 296

12 297

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