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Design Framework and Manufacturing of an Active Magnetic Bearing Spindle for Micro-Milling Applications

Kazi Sher Ahmed, Bekir Bediz

Abstract

Micro-milling spindles require high rotational speeds where conventional rolling element bearings face limitations such as friction and thermal expansion. Active magnetic bearings (AMBs) address these challenges by providing non-contact and lubrication-free operation at ultra-high speeds with the ability to actively regulate spindle dynamics. The existing literature on AMB spindles has mainly reported specific prototype realizations or control system implementations for specific spindle dynamics. Consequently, design knowledge remains fragmented across isolated successful studies. This paper addresses this gap by presenting a systematic and iterative framework to design and manufacture a micro-milling AMB spindle. The process involves a multidisciplinary design flow with a focus on critical practical aspects of manufacturing. The realized spindle is reported as a case study.

Design Framework and Manufacturing of an Active Magnetic Bearing Spindle for Micro-Milling Applications

Abstract

Micro-milling spindles require high rotational speeds where conventional rolling element bearings face limitations such as friction and thermal expansion. Active magnetic bearings (AMBs) address these challenges by providing non-contact and lubrication-free operation at ultra-high speeds with the ability to actively regulate spindle dynamics. The existing literature on AMB spindles has mainly reported specific prototype realizations or control system implementations for specific spindle dynamics. Consequently, design knowledge remains fragmented across isolated successful studies. This paper addresses this gap by presenting a systematic and iterative framework to design and manufacture a micro-milling AMB spindle. The process involves a multidisciplinary design flow with a focus on critical practical aspects of manufacturing. The realized spindle is reported as a case study.
Paper Structure (36 sections, 15 equations, 17 figures, 4 tables)

This paper contains 36 sections, 15 equations, 17 figures, 4 tables.

Table of Contents

  1. Introduction
  2. Design Framework
  3. Step 1: Requirements and Feasibility
  4. Step 2: Drive System Design
  5. Step 3: Rotor Design
  6. Step 4: Design of Electromagnetic Components
  7. Step 5: Backup (Auxiliary) Bearing Design
  8. Step 6: Housing Design
  9. Step 7: Cooling Design
  10. Step 8: Manufacturing and Assembly
  11. Case Study
  12. Application-specific requirements
  13. Micro-milling forces and unbalance
  14. Rotational speed
  15. Negative stiffness
  16. ...and 21 more sections

Figures (17)

  • Figure 1: Design flowchart for a micro-milling AMB spindle.
  • Figure 2: Predicted cutting forces in x, y, and z directions for a slot-milling operation using a two-flute tool.
  • Figure 3: Turbine torque as a function of nozzle diameter with turbine power efficiency range 0.18-0.48. Selected nozzle diameter 1.5 mm results in 2.65 N mm of torque with conservative power efficiency of 0.18.
  • Figure 4: Air turbine components. (a) Turbine buckets and splitter machined into the rotor. (b) Nozzle plate with push-in pneumatic fittings.
  • Figure 5: Rotor Campbell diagram showing rigid body (cylindrical and conical) and bending modes.
  • ...and 12 more figures