Frequency Domain Analysis and Precision Realization in Deterministic Figuring of Ultra-Precision Shaft Parts

Abstract

An aerostatic spindle is a core component in ultra-precision machine tools. The rotor of the spindle has extremely high manufacturing accuracy, which cannot be directly achieved via traditional machining, but always via manual grinding. The deterministic figuring theory is introduced into the machining of shaft parts, which overcomes many shortcomings of manual grinding. The manufacturing error of the shaft’s surface contains different frequency components, which have different effects on its working performance and the figuring process. Because the deterministic figuring method can only correct the error within a limited frequency range, in order to ensure high efficiency and high precision of the figuring process, we need to use reasonable filtering parameters to filter out the error with unnecessary frequencies. In this paper, the influence of contour error with different frequencies and amplitudes on the air film are analyzed using computational fluid dynamics (CFD) software, and the amplitude–frequency analysis as a function of the power spectral density (PSD) characteristic curve is used to study the filtering parameters of the measured data. After the figuring experiment using the filtering parameters obtained from the analysis, the average roundness of the shaft converged from 0.419 μm to 0.101 μm, and the cylindricity converged from 0.76 μm to 0.35 μm. The precision reached the level of manual grinding, which proves the rationality of the analysis using filtering parameters in a shaft’s deterministic figuring.

Research on the Integrated Process Method of In-Situ Measurement and Machining for the Mandrel of Aerostatic Spindle

“…The processing technology for mandrel parts mainly encompasses traditional precision turning [9], traditional precision grinding [10], manual polishing [11], and timecontrolled grinding technology [12][13][14][15]. Traditional precision turning and grinding involve using a lathe or grinder to process the mandrel, with the final surface accuracy depending on the precision of the machine tool employed.…”

“…Manual polishing, which relies heavily on the experience and skill of the engineer, often results in lower efficiency and limited environmental adaptability [17]. Time-controlled grinding technology is a type of deterministic machining technology [18] proposed by the National University of Defense Science and Technology in 2019 [15,19]. This method involves four key steps: off-position measurement of the mandrel's cylindricity error, calculating processing dwell times based on the error distribution, clamping the mandrel for processing and subsequent measurement, and iterating this process until the desired accuracy is achieved.…”

“…After conducting a comprehensive analysis, it can be known that the machining accuracy achieved through time-controlled grinding technology surpasses that of traditional machining and manual polishing methods. However, according to currently available information [15,16], this advanced technology has only been proven effective for high-precision machining of a specific spindle with a diameter of 100mm and a length of 35mm. The processing of high-precision spindles of similar machining accuracy but greater length has not been mentioned yet.…”

“…Chen's study on a steel shaft with a height and diameter of 100mm demonstrated that time-controlled grinding technology could reduce cylindricity from 6.899 µm to 2.078 µm through several iterations [20]. Sun [15,16] conducted experimental research on time-controlled grinding for a mandrel with a diameter of 100mm and a length of 35mm, further optimizing the process of time-controlled grinding technology and achieving roundness and cylindricity of 0.15 µm and 0.35 µm, respectively. However, its processing length is comparatively short, with a mere length of 35mm.…”

Fast and Precise Non-Contact Measurement of Cylindrical Surfaces with Air Gauges

“…The harmonic components of the roundness profile are very common in industry, where they are used for the description of the rotor's geometry, since its variations cause local stiffness deviations [5]. The various frequency characteristic components result in different impacts on the operation of the ultra-precise shafts due to the manufacturing errors on the components' surfaces [6]. As well as measurement and analysis of the surface topography of an engine cylinder-as a fingerprint of the manufacturing process [7]-it is also necessary to assess its meso-and macro-features: roundness and cylindricity.…”