High-speed Spindle Units Research Articles

Recommendations on Diagnostics of Support Condition of High-Speed Spindle Units

In the course of the study, amplitude-frequency characteristics of the responses of vibrational acceleration of the spindle unit were obtained experimentally with a short-term impact of a force directly on its spindle. By analyzing the frequency composition of amplitude spectra, the peaks of natural frequencies of the spindle unit were determined at various values of the preload, and, accordingly, the operating modes of the spindle unit were selected, which would reduce its vibration activity and increase processing accuracy.

Computational-experimental research of the stiffness of high-speed spindles

The stiffness indices of high-speed spindle units on angular contact ball bearings at high rotational speeds are investigated. It is found, that the spindle rotational speed, radial load, bearing temperature, type and magnitude of the preload in the bearings significantly affect the stiffness of the spindle unit. Keywords: high-speed spindle unit, angular contact ball bearing, elastic-deformation model. i.a.zverev@stankin.ru

Особливості формування професійної компетентності майбутніх фахівців машинобудівної галузі під час вивчення теми «Безпечне конструювання високошвидкісних шпиндельних вузлів на пневматичних опорах»

The article analyzes the learning process of the students of the machine-building industry. It is established that engineering thinking occupies a special place among professional competences needed for the successful professional activity of a technical specialist. The aim of the article is to analyze the peculiarities of forming the professional competence of future specialists of the machine-building industry during the study of the topic "Safe construction of high-speed spindle units on the pneumatic supports". Studying of this topic provides acquiring by the students the knowledge and skills of designing of efficient and safe elements of the mechanical equipment. First of all the stress is made on the safety of the machines and mechanisms for metal working, being designed. This stipulates the proposal to use pneumatic supports for spindle units, which are designed for high-speed machine-tools of high precision and allow to increase the rigidity and technological capabilities of the spindle at its high efficiency and satisfy the requirements of electrical, explosion and fire-safety, allowing students to form the culture of safety, which is decisive for the formation of professional competence. We believe that the proposed method of calculating the pneumatic supports with the required static stability of its equilibrium position ensures their efficient and safe use, as well as generates technical thinking and professional competence of future specialists. In addition, this technique of forming technical thinking while studying the topic of safe construction of high-speed spindle units on pneumatic supports, in the conditions of the reduction of time for training of future specialists of the machine-building industry, allows moving from the reproductive training to searching training.

Характеристики конічних підвісів з поздовжніми глухими мікроканавками постійної ширини і різним профілем по глибині

Gas bearings with longitudinal grooves are successfully used in high-speed spindle units of drilling and grinding machines, processing equipment for processing crystals and precision instruments. But a small viscosity and compression of gas requires a detailed study of all factors that affect their work. The reliability of gas bearings depends on the compliance of the calculated values of the lifting force, the moment of reaction and the rigidity of the working gas layer from the external load, and the economy — on the gas flow. Engineers and scientists constantly search for structures and methods for calculating gas bearings with maximum power characteristics with minimal gas consumption. This is achieved using external chokes, a combination of external and internal throttling of the gas flow. The use of gas bearings with longitudinal grooves is determined by the manufacturability of their manufacture and high reliability in operation. But bearings of this type are significantly inferior in their characteristics to bearings with pressure regulators outside the carrier gas layer with a relative bearing length of l £ 3. To improve the characteristics of bearings with longitudinal grooves, it is necessary to reduce costs and harmful circular flow of gas in the working gap from the section of increased pressure to the lower side. This is achieved by using variable profile grooves with a maximum depth of grooves in the compressed gas supply zone for working of gas bearings. The proposed application of stepped longitudinal micro-grooves and micro-grooves, the depth of which varies according to the linear law with the maximum depth at the line of pressure of compressed gas into the working gaps of the conical bearing, leads to an increase in the efficiency of Eε (Kε*/Q* ratio) of the use of tapered bearings in spindle units, devices and etc. from 13,9 to 16,8 % for α = 2° and from 1,2 to 16,5 % for α = 6° and reduces the radial displacement of the axis of the shaft with the coaxial with the body of the position by 17…27 % compared with the bearings with the micro-grooves constant depth (with the same external load), which increases the reliability of the work of the spindle units. The profile of longitudinal micro-grooves has an insignificant effect on the angular and axial stiffness of the bevel bearing and greatly affects the radial stiffness.

Experimental Investigation of Mechanical Micro Machining for AL6061-T6 Material

This paper is to experimentally investigate the mechanical micro machining properties of AL6061-T6 using tungsten-carbide micro end mills. The cutting simulation based on Finite Element Analysis (FEA) method is also conducted to estimate cutting forces, cutting temperature, and minimum chip thicknesses. The simulation results are used for the determination of experimental machining conditions such as depth of cut, feed rates and cutting speeds. A number of slot micro-milling experiments were performed using 400um diameter micro end mills on a 3 Axis CNC machining center attached with a high precision and high speed spindle unit. The machined surface quality, geometric feature shape, cutting burr generation as well as build-up edges are observed in the cutting experiments. Optimum cutting parameters for a better surface quality and smaller burr sizes are suggested.

Experimental Study on Tilted Planetary Motion Drilling for CFRP

The study deals with a proposal and experimental study on the tilted planetary motion drilling for CFRP. The authors have modified cutting mechanism principle of the orbital drilling, which named as the tilted planetary motion drilling. Its axis of tool rotation spindle is not parallel to the axis of planetary revolution. The tilted angle is adjustable from 0 to 2 degrees. Because of tool rotation axis is tilted, penetration is not caused by outermost cutting edges but inner cutting edges. If penetration could be occurred, the inner cutting edges penetrate firstly, then the outermost edges enlarge drilled hole and these sequence can avoid generation of delaminations and burrs. The tilted planetary motion drilling has been demonstrated by the practical fundamental drilling experiment by use of a high-speed spindle unit and a lathe as imitating tilted planetary motion. From the experimental result, capability of tilted planetary motion drilling has been realized and no burrs and delaminations are observed on the workpiece.

Thermal Model of High-Speed Spindle Units

For the purpose to facilitate development of high-speed Spindle Units (SUs) running on rolling bearings, we have developed a beam element model, algorithms, and software for computer analysis of thermal characteristics of SUs. The thermal model incorporates a model of heat generation in rolling bearings, a model of heat transfer from bearings, and models for estimation of temperature and temperature deformations of SU elements. We have carried out experimental test and made quantitative evaluation of the effect of operation conditions on friction and thermal characteristics of the SUs of grinding and turning machines of typical structures. It is found that the operation conditions make stronger effect on SU temperatures when rpm increases. A comparison between the results of analysis and experiment proves their good mutual correspondence and allows us to recommend application of the models and software developed for design and research of high-speed SUs running on rolling bearings.

Model of Rotation Accuracy of High-Speed Spindles on Ball Bearings

For the purpose to improve a design quality of high-speed spindle units, we have developed mathematical models and software to simulate a rotation accuracy of spindles running on ball bearings. In order to better understand the mechanics of ball bearings, the dynamic interaction of ball bearings and spindle unit, and the influence of the bearing imperfections on the spindle rotation accuracy, we have carried out computer aided analysis and experimental studies. When doing this, we have found that the spindle rotation accuracy can vary drastically with rotational speed. The influence of bearing preload has a secondary importance. Comparison of the results of these studies has demonstrated adequacy of the models developed to the real spindle units.

Design on High-Speed Precision Grinder

As one of the modern manufacture technology, high-speed precision grinding takes an important part in the modern manufacture field. With the development of the technology on high-speed spindle unit, linear precision high-speed feed unit, manufacture of grinding wheel, measurement etc, a great deal of research achievements make it possible for high-speed precision grinding. In this paper, using PMAC (Programmable Multi-Axis Controller)—PC as the central controller, a new kind of high-speed precision grinder is designed and manufactured. The servo control technology of linear motor is investigated. The dynamic performances of the machine are analyzed according to the experimental results. Elliptical workpieces have been machined with this new high-speed precision grinder. Based on these research results, a very helpful approach is provided for the precision grinding of complicated workpieces, and these results promote the development of high speed grinding too.

Thermal model of high-speed spindle units

For the purpose to facilitate development of high-speed spindle units (SUs) running on rolling bearings, we have developed a beam element model, algorithms, and software for computer analysis of thermal characteristics of SUs. The thermal model incorporates a model of heat generation in rolling bearings, a model of heat transfer from bearings, and models for estimation of temperature and temperature deformations of SU elements. We have carried out experimental test and made quantitative evaluation of the effect of operation conditions on friction and thermal characteristics of the SUs of grinding and turning machines of typical structures. It is found out that the operation conditions make stronger effect on SU temperatures when rpm increases. A comparison between the results of analysis and experiment proves their good mutual correspondence and allows us to recommend application of the models and software developed for design and research of high-speed SUs running on rolling bearings.

Thermal characteristics of the spindle bearing system with a gear located on the bearing span

High cutting speeds and feeds are essential requirements of a machine tool structure to accomplish its basic function which is to produce a workpiece of the required geometric form with an acceptable surface finish at as high a rate of production as is economically possible. Since bearings in high speed spindle units are the main heat source of total cutting system, in this work, the thermal characteristics of the spindle bearing system with a tilting axis were investigated using finite element method to improve the performance of the spindle bearing system. Based on the numerical results, a specially designed prototype spindle bearing system was manufactured. Using the manufactured spindle bearing system, the thermal characteristics were measured and compared to the numerical results. From the comparison of the numerical results with the experimental results, it was found that the finite element method predicted well the thermal characteristics of the spindle bearing system.