Model-Based Design of Motorized Spindle Systems to Improve Dynamic Performance at High Speeds

High-speed motorized spindle systems are subjected to several effects during high-speed rotations that can cause substantial changes in their dynamic and thermal behaviors, leading to chatter, bearing thermal seizure, or premature spindle bearing failures. Therefore, it is important to consider these high-speed effects in the design stage of high-speed motorized spindles. This paper first develops a design flow chart to represent the overall spindle design problems. Based on this flow chart, eight design parameters are identified. A design sensitivity analysis of these eight design parameters is then conducted based on an integrated finite element method model to investigate their influence on the natural frequencies of the spindle system. Based on the rule of Maximum Improvement First, a set of systematic design procedures is proposed to suggest design changes to a custom-designed motorized spindle rated at 32 kW and 25,000 rpm. Based on the simulation results, it is shown that the first-mode frequency of this spindle system can be improved from 790.7 Hz to 934 Hz at 25,000 rpm by simply adjusting the front and rear bearing locations. At the optimal design, the first-mode frequency can reach 1454.3 Hz at 25,000 rpm, which represents more than 80 percent improvement over the original design.