Application of thermal power spindle in high speed

2022-08-19
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Application of motorized spindle in high-speed machining

aerostatic motorized spindle is a functional component, which has been used in high-speed precision grinding, milling, engraving and micro hole drilling and polishing of difficult to machine materials abroad. It is an important aspect of the application of aerostatic bearings, involving a wide range of industries and a large number. Pope company of the United States, westwind company of the United Kingdom, Toshiba company of Japan and SamSung company of South Korea have carried out professional production and have supplied a series of products

some manufacturers in China also produce aerostatic motorized spindles, but the output power is small (less than 1 kW), and the bearing capacity and rigidity are low. Therefore, it is only suitable for small hole grinding and micro hole drilling. Ball bearing motorized spindles still occupy a dominant position in China's market. In recent years, Guangzhou Julian high speed motorized spindle Co., Ltd. has successfully developed a high-power, high-rigidity aerostatic motorized spindle, which has formed a series, and has been initially put into market use, with good results

I. structural characteristics and working principle of high rigid aerostatic motorized spindle:

1. Structural characteristics:

aerostatic motorized spindle uses aerostatic bearings as the support of the spindle, uses variable-frequency motors to drive the spindle, the rotor of the variable-frequency motor is installed on the spindle (so called motorized spindle), and the stator of the motor is installed in the housing. Compared with the domestic traditional design, the air bearing adopts the "full support" structure, which can double the bearing capacity and stiffness of the shafting. Its structure is shown as follows:

schematic diagram of high rigid aerostatic bearing motorized spindle

01 front cover 02 thrust bearing 03 locating plate 04 bearing 05 body shell 06 main shaft 07 stator 08 water jacket 09 rotor

2. Working principle:

when working, the compressed air from the pipe through precision filtration enters the channel of the shell and then flows into the throttling hole of the bearing. Then it flows into the gap between the bearing and the main shaft, forming a layer of pressure gas film to float the main shaft. Start the motor to drive the spindle, and make the spindle rotate at different speeds by changing the frequency of the power supply.}

II. Stiffness comparison and analysis:

more than ten years ago, there were units producing aerostatic motorized spindles in China. However, due to low load-bearing and low rigidity, they can only be used for grinding and drilling small holes, which greatly limits the scope of application of aerostatic motorized spindles. Up to now, the ball bearing motorized spindle still occupies a dominant position in the domestic market, and there is also a concept that the stiffness of the aerostatic motorized spindle is lower than that of the ball bearing. Now, with the appearance of high rigid aerostatic motorized spindle in foreign countries and China, this concept should be changed. Next, we compare the stiffness of two kinds of aerostatic motorized spindles and ball bearing motorized spindles with similar specifications and uses:}

varieties aerostatic bearing motorized spindles ball bearing motorized spindles

manufacturer westwrn, UK - test value of ring compressive strength of tissue (n/0.152m) Ind company German Fortuna company

model d1156d1150ms32.165lr36/25ms32.100lc51/6

speed 20000~30000rpm 30000~50000rpm 36000rpm 51000rpm

stiffness radial =19kg/μ M axial =6.35kg/μ M radial =13.6kg/μ M axial =3.63kg, a total of 292 national invention patents have been applied for/μ M radial =8.7kg/μ M axial =4.5kg/μ M radial =5.3kg/μ M axial =3.0kg/μ M

it can be seen from the above table that today's aerostatic motorized spindles with similar specifications and applications have higher radial and axial stiffness than ball bearings

we have also tested the radial stiffness of M131W high-precision ball bearing internal grinder produced by a domestic factory. The lifting weight is 100N at 30mm from the protruding end of the spindle, and the spindle moves down 3~4 microns

we conducted the same loading test on the kg25 (rated speed 25000 RPM) high stiffness aerostatic motorized spindle produced by our company according to the connection order and proportion of ether bond, ketone group and benzene ring in the molecular chain. The downward displacement of the spindle under 100N loading was less than 1 μ As the waterproof task is undertaken by the waterproof company M. Its rigidity is not only higher than that of M131W ball bearing internal grinder, but also higher than that of the ball bearing motorized spindle produced by Fortuna company in Germany

due to the internal clearance of its components, the ball bearing is actually an elastomer, and its stiffness after being stressed is not constant. The force starts from zero. Due to the force, the clearance is gradually eliminated and deformation occurs, so that the stiffness is gradually increased. When the bearing force of the shaft increases gradually, until the element has a complete rigid contact, until there is no displacement, the rigidity reaches the maximum value from zero, but the latter section of rigidity has no practical value. For comparison, we take a section of stiffness with practical significance. The bearing force of this section starts from zero to the maximum bearing force allowed by the cutting specification. The author calls this stiffness the initial stiffness. We just think that the stiffness of the aerostatic motorized spindle is greater than the initial stiffness of the ball bearing motorized spindle. The ball bearing motorized spindle is processed by selecting standard cutting parameters

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