RU2437751C2 - Grinding wheel fastener - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to abrasive processing of the bodies of revolution, particularly, to abrasive tool fasteners. Proposed fastener comprises fixed flange whereon grinding wheel is secured by means of moving flange. Said fixed flange is made integral with the rotor and arranged on its periphery. Twisted magnetic duct is arranged on rotor end faces with short-circuited secondary. Rotor and stator with twisted magnetic duct on end face make end induction motor. Magnetic duct grooves accommodate mi-phase primary. Rotor runs in thrust bearings fitted in support cup press fitted in stator central bore.

EFFECT: higher quality of machined surface, reduced consumption of abrasive tool, improved operating performances.

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Description

The invention relates to the field of manufacturing equipment for attaching abrasive tools and can be used in the final abrasive treatment of surfaces of bodies of revolution.

A known method and device for attaching the grinding wheel, established by GOST 2270-78, depending on the shape and size of the abrasive tool [1].

The disadvantages of attaching the grinding wheel during its operation by the periphery are as follows. Use of the useful part of the circle within

m = 0.137D, mm

where D is the outer diameter of the circle, mm,

leads to a decrease in cutting speed to 40% of the original [2]. This causes, as the wheel wears, a decrease in its diameter, a deterioration in the quality of the machined surface and an increase in the consumption of the wheel.

The objective of the invention is to expand technological capabilities, to increase the frequency of rotation of the wheel as its diameter decreases and the initial grinding speed remains, as well as improving the quality of the processed surface and reducing the consumption of abrasive tools.

The problem is solved using the proposed device for attaching the grinding wheel, containing a fixed flange, on which the grinding wheel is rigidly fixed with bolts of the movable flange, the fixed flange is made on the periphery and at the same time with a rotating rotor, on the end of which there is a twisted magnetic circuit having in grooves a secondary short-circuited winding, the aforementioned rotor being a part of a mechanical induction motor, the latter in addition to the rotor, contains a stator with a twisted magneto rovodom at the end, which is located in the grooves m _1-phase primary winding, moreover, a rotor rotatably movably via thrust bearings is mounted with the gap between the ends of the magnetic cores on the reference glass, pressed into the central opening of the stator.

The essence of the proposed device for mounting the grinding wheel is illustrated by drawings.

Figure 1 shows the design of the proposed device for mounting the grinding wheel, working in the periphery, a longitudinal section; figure 2 is a General side view; figure 3 is a left view along A in figure 1, an end view; figure 4 - to calculate the maximum value of the use of the working part of the grinding wheel during its operation by the periphery.

The proposed device is intended for finishing abrasive-diamond processing of workpieces such as bodies of revolution.

The device comprises a fixed flange 1, on which a grinding wheel 4 is rigidly fixed with a movable flange 2 by bolts 3. The fastening elements of the circle: a fixed flange, bolts and a movable flange, for example, can be made according to GOST 2270-78.

The fixed flange is integral with the rotating rotor 5 and is located on its periphery. At one end of the rotor is a twisted magnetic circuit 6 having a secondary short-circuited winding in the slots.

The rotor 5 is part of the mechanical induction motor (TAD) [3 ... 5]. TAD in addition to the rotor contains a stator 7 with a twisted magnetic circuit 8 at the end. In the grooves of the magnetic circuit 8 of the stator is m _1- phase primary winding.

The rotor is movable with the possibility of rotation, thanks to the thrust bearings 9, is fixed taking into account the gap Δ between the ends of the magnetic circuits 6 and 8 on the support cup 10, pressed into the Central hole of the stator 7.

After connecting the winding of the stator magnetic circuit to the network, which is carried out using a current collector (not shown), as a result of the action of a rotating magnetic field on the conductors of the short-circuited winding of the rotor magnetic circuit, the latter is rotated at a speed of V _AND . The resulting axial forces of the magnetic circuits of the rotor and stator are perceived by the thrust bearing 11. Due to the fact that the thrust bearing 11 is installed outside the magnetic circuits of the rotor and stator, therefore, the diameter of its raceway is large enough, the rotor's stability against the eversion action of the forces required for effective grinding increases .

This is how an end induction motor works.

The support cup 10 forms an outer annular protrusion 12 for fixed connection of the device, for example, with the spindle 13 of a grinding machine (not shown), on which grinding is carried out.

The fixed mounting of the stator of the proposed device relative to the spindle is made by screws 14, which are screwed into the threaded stator sockets.

In order to prevent dust and dirt from entering the thrust bearing 11 mounted between the rotor and the stator, a groove for the rubber ring 15 or the stuffing felt ring (according to GOST 6418-67) covering the stator 7 is drilled in the hole of the stationary flange 1.

The spindle 13 of a grinding machine (not shown) rotates with its own speed V _W , while the rotor TAD rotates with a speed V _AND , then the tool - grinding wheel will rotate with a speed equal to the sum of the speeds V _Σ = V _И + V _Ш.

The proposed device can operate in two modes:

- in the mode of increasing the rotational speed of the wheel as its diameter decreases and the initial grinding speed is maintained;

- in the mode of high-speed grinding at a speed of rotation of the wheel equal to V _Σ = V _AND + V _W.

The proposed device, operating in the first mode, expands the technological capabilities, provides an increase in the rotational speed of the wheel as its diameter decreases and the initial grinding speed is maintained.

The device allows to improve the quality of the processed surface and reduce the consumption of abrasive tools. Increasing the rotational speed of the circle as it wears out intensifies the process and allows you to increase processing productivity, reduce the complexity and cost of the operation.

The second high-speed grinding mode (carried out at a speed of 35 ... 60 m / s, according to GOST 23505-79), implemented by the proposed device, can be carried out in different ways:

1. Grinding with an increased speed of rotation of the wheel without changing the other components of the grinding mode (without changing the frequency of rotation of the workpiece, transverse feeds of the circle and longitudinal feeds of the workpiece). In this case, low roughness parameters of the surface of the workpiece to be grinded and increased wheel durability will be ensured, which will reduce the number of edits, the wear rate of the wheels and the auxiliary time.

The grinding process occurs at lower forces.

2. Grinding with an increased speed of rotation of the wheel while simultaneously proportionally increasing the speed of rotation of the workpiece. In this case, the processing productivity increases with a decrease in machine time in proportion to an increase in rotational speed and wheel durability.

The surface roughness and grinding force will be the same as before increasing the speed of rotation of the circle.

These methods can be used for finishing operations to ensure specified deviations of the shape and size of the workpiece, as well as the roughness of the surface to be grinded.

Disadvantages of high-speed grinding: grinding power increases; increased heat generation, which can lead to burns. Burns can be avoided by increasing the speed of the workpiece and improving the compositions and methods for supplying cutting lubricants (COTS).

In the mode of preservation of the initial grinding speed and high-speed grinding, it is necessary to increase the requirements for balancing fast-rotating workpieces, machine and wheel.

The proposed device should have increased dynamic stiffness and drive power.

The choice of grinding mode is determined by the requirements for the workpiece. Moreover, in all cases, one should proceed from the economic efficiency of the operation.

The main factors influencing the performance of grinding modes are the following: peripheral speeds of the grinding wheel and workpiece; cross feeds; properties and methods of supplying SOTS; frequency of corrections and properties of ruling tools (diamond rollers, blocks, plates); quality and size of grinding wheels; rigidity of the technological system (machine - fixture - tool - part).

When working in high-speed mode (at a wheel speed of up to 35 ... 60 m / s) and increasing the feed and drive power of the wheel, grinding performance increases by 1.4 ... 1.7 times; when using special SOTS supplied to the cutting zone under high pressure - up to 1.5 times; while increasing the cutting ability of the wheel with the help of its frequent corrections and the use of effective ruling tools (diamond rollers, blocks, plates) - by 1.3 ... 1.5 times.

Example. On the circular grinding machine mod. ZM151 by longitudinal feed to the passage, we polished a shaft section with a diameter of 40h8 mm and a length of 210 mm; shaft length 260 mm. The roughness of the treated surface Ra = 1.0 μm. The allowance on the side of 0.2 mm. The workpiece material is steel 40X hardened by hardness HRC 52. The method of fastening the workpiece is in the centers.

We chose a grinding wheel. For round external grinding with longitudinal feed, surface roughness Ra = 1.0 μm, structural hardened steel with HRC> 50, the recommended characteristic: 24A40NSM25K8. The material of abrasive grains was white electrocorundum grade 24A.

The choice of this brand of white electrocorundum is due to the high hardness of the workpiece being grinded and the requirements for the accuracy and roughness of the processed surface. The characteristics accepted: grain size No. 40, hardness CM2 and ceramic bond (K).

Brief substantiation: grit index B (the content of the main fraction with grit No. 40 45%); took the average circle structure No. 5 (for circular external grinding in the centers, structures No. 5 and 6 are usually recommended); indicate the type of accepted ceramic bond K8 (for electrocorundum circles); indicate the type of circle.

On circular grinding machines, PP and LDPE circles are usually used. We accept the type of LDPE (flat with double-sided undercut), which provides convenient and reliable fastening of the circle on the spindle of the grinding head using the proposed device; accept the class of circle A; indicate the permissible peripheral speed of the circle of 60 m / s (high-speed grinding).

Marking of the full characteristics of the circle: PVD 24A40NSM25K8 60 m / s. Dimensions of the new circle: diameter D = 600 mm, circle width (or height) H = 63 mm. The diameter of the hole in the circle is d = 305 mm. The maximum value of the used part of the circle m = 0,137D = 82.2 mm (see figure 4). Diameter of clamping flanges D _Ф = 365 mm; unused flange-free part of the circle a = 5 mm [2]. Cutting modes: according to the passport data of the machine mod. ЗМ151 grinding wheel speed 1590 rpm, i.e. V _W = 50 m / s, it is within the recommended range; peripheral speed of the workpiece (rotation speed) is recommended 15 ... 55 m / min. We accept an average value of 35 m / min (0.58 m / s); determine the rotational speed corresponding to the adopted peripheral speed of 280 rpm The found value of 280 rpm can be set on the machine mod. ZM151, which has stepless speed control of the workpiece within 50 ... 500 rpm. Grinding depth (lateral feed of the wheel) recommended 0.005 ... 0.015 mm / table stroke; taking into account the requirements for processing accuracy (eighth grade-8h) and surface roughness Ra = 1.0 μm, we take 0.005 mm / stroke.

Longitudinal feed per revolution of the part S _PR = 18.9 mm / rev.

The longitudinal speed of the table is 5.3 m / min (0.09 m / s). The found speed value of 5.3 m / min can be set on the machine used, which has stepless speed control of the longitudinal stroke of the table within 0.1 ... 6 m / min. The power spent on cutting is 5.5 kW. Engine power of the grinding head of the machine mod. ЗМ151 - 10 kW, i.e. processing is possible. Machine time - 2.22 minutes.

With the wear of the wheel, the processing speed decreased and at maximum wear (D _OIH = D _Ф + 2а = 365 + 10 = 375 mm) it will reach 31.2 m / s. Thus, the cutting speed decreased by 37.6%.

To preserve the initial grinding speed (V _Ш = 50 m / s), the rotational speed of the wheel was increased to 2550 rpm due to the inclusion of a mechanical induction motor mounted in the device for mounting the wheel, i.e. TAD rotor was accelerated to a speed of 960 rpm.

The proposed device helps to increase the durability period between regrinding of the used diamond-abrasive tool, increases accuracy, quality and productivity.

The proposed device has the shortest additional kinematic chain of the drive of the tool, expands the technological capabilities, provides an increase in the frequency of rotation of the wheel as it wears and its diameter decreases and maintains the initial grinding speed, improves the quality of the machined surface and reduces the cost of an abrasive tool, increases tool life and improves tool performance : vibration resistance, strength, and also allows the use of harder and less granular tools mental material through the use of high-speed grinding modes.

Literature

1. Kashchuk V.A., Vereshchagin A.B. Handbook grinder. - M.: Mechanical Engineering. 1988. - P.411 ... 427.

2. Abrasive materials and tools: Industry. cat. VNIIASH. - M.: VNIITEMR. 1990. - S.288 ... 299.

3. Zagryadtsky V.I., Kobyakov E.T., Stepanov Yu.S. Face asynchronous electric motors and electromechanical units. / Under the general ed. Doctor of Technical Sciences, prof. Yu.S. Stepanova - M .: Engineering - 1, 2003 - S.6-15, Fig. 1.4-1.5.

4. Patent RU 2058655, C6 Н02К 5/16, 17/00. End electric asynchronous machine / Zagryadtsky V.I., Kobyakov E.T. 1996. Bull. No. 11.

5. Patent RU 2140700, C1 6 Н02К 5/173, 5/16, 17/16. End electric asynchronous machine / Zagryadtsky V.I., Kobyakov E.T., Sidorov E.P. 1999. Bull. No. 30.

Claims (1)

A device for attaching a grinding wheel containing a fixed flange, on which a grinding wheel is rigidly fixed with bolts and a movable flange, characterized in that the fixed flange is made on the periphery and in one piece with a rotating rotor, on the end of which there is a twisted magnetic circuit with grooves a secondary short-circuited winding, while the aforementioned rotor is part of a mechanical induction motor, the latter in addition to the rotor contains a stator with a twisted magnetic circuit at the end, in the grooves of which olozhena m _1-phase primary winding, the rotor being rotatably movable by means of thrust bearings fixed with the gap between the ends of the magnetic cores on the reference glass, pressed into the central opening of the stator.

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