RU2205100C1 - Intermittent grinding method - Google Patents

Abstract

FIELD: deep circumferential grinding of parts of hard-to-grind materials having trend for occurring flaws such as burnouts and microcracking. SUBSTANCE: method is realized with use of builtup grinding wheel mounted by acute angle relative to plane normal to spindle rotation axis. Method comprises steps of imparting to grinding wheel rotation and motion relative to worked article; using grinding wheel having at least three abrasive discs; mounting disc axes with eccentricity value ε of geometrical axis of spindle by means of eccentric rings with opening shifted by value ε relative to their outer surface; placing symmetry axes of abrasive discs by the same central angles one relative to another. EFFECT: lowered grinding temperature, enhanced strength and size stability of tool due to eccentric mounting of abrasive discs of grinding wheel by inclination angle, enhanced efficiency, improved grinding quality. 5 dwg

Description

 The invention relates to deep peripheral grinding of hard-to-grind materials susceptible to defect formation in the form of burns and microcracks.

 A known method of profile diamond grinding, in which rotation is communicated to the wheel, and longitudinal feed is supplied to the workpiece, while the axis of rotation of the wheel is offset from its geometric axis by a distance h> t / 2, where t is the grinding depth in one pass [1].

 The disadvantage of this method is the imbalance of the processing process, which increases with each revolution of the circle and leads to vibrations and, as a result, to a decrease in the quality of the processed surface and productivity.

 A known method of intermittent grinding, in which the grinding wheel is informed of the rotation and movement relative to the workpiece, and the wheel is composed of several cutting wheels, and set it at an angle (selected by the above formula) to a plane perpendicular to the axis of rotation, while editing as it becomes dull and salting of the circle is carried out at a zero angle of inclination [2].

 The disadvantage of this method is the relatively high consumption of the abrasive tool, since after wear of any sections of the composite wheel, it is necessary to remove the abrasive layer along the entire peripheral profile, while the process imbalance increases during processing, which leads to vibrations and, as a consequence, to a decrease in quality surface finish and performance.

 The objective of the invention is to increase the accuracy and productivity of processing, reducing the grinding temperature and consumption of the abrasive tool due to a change in the kinematics of the abrasive process.

 The problem is solved using the proposed method of intermittent grinding, in which a composite grinding wheel, set at an acute angle to a plane perpendicular to the axis of rotation of the spindle, is informed of the rotation and movement relative to the workpiece, while taking a circle that is composed of several (at least three) abrasive discs, and set the axis of the latter eccentrically with an eccentricity ε of the geometrical axis of the spindle using special eccentric rings offset from the surface of the hole with an eccentricity ε of the hole, and the axis of symmetry of the eccentric abrasive discs being placed at equal central angles to each other, in addition, the eccentricity value is assigned based on the formula ε> h, where h is the grinding allowance.

 In FIG. 1 schematically shows a tool for implementing the proposed method of intermittent grinding, side view, longitudinal section along BB in FIG. 2; in FIG. 2 is the same, front view along A in FIG. 1; in FIG. 3 is a processing diagram of the proposed method, in the cutting zone is an abrasive disk 2; in FIG. 4 - scan trace of the circle on the surface; in FIG. 5 is a section along BB in FIG. 1.

 According to the proposed method of intermittent grinding, the tool and the device for its fastening work as follows.

 The grinding wheel is made up of several (at least three) abrasive discs 1, 2, 3, the number of which is determined by the width of the surface to be grinded and the required performance.

The circle thus formed is mounted on the spindle 4 at an acute angle α to the plane perpendicular to the axis of rotation, using fastening flanges 5 with beveled ends, spacers 6 and nuts 7. Abrasive discs 1, 2, 3 can be located both parallel and inclined to the plane perpendicular to the axis of rotation, while the smooth adjustment of the angle α of the inclination of the disks is carried out by mutual rotation of the flanges 5, in which the beveled ends are made at an angle α _max / 2, and the rotation of one flange from one end to some angle The ol relative to the axis of the spindle should correspond to rotation by the same angle of the other flange from the other end of the composite circle.

 Spacer washers 6, the thickness of which affects the heat intensity of the grinding process, are taken with a height equal to not more than half the height of the abrasive disk.

 An increase in the angle α of the inclination of the circle has a positive effect on the free running of hard-to-grind materials that are prone to defect formation in the form of burns and microcracks.

Another design feature of the compound wheel is the eccentric installation of the abrasive disks 1, 2, 3 on the spindle 4. The abrasive disk 1 is mounted on the spindle 4 using a special eccentric ring 8, in which the axis of the hole is offset by the amount of eccentricity ε relative to the outer surface, the disk 2 - with using ring 9 and disk 3 - using ring 10, etc. In this case, the axis of symmetry of the eccentrically mounted abrasive disks are placed at equal central angles β = 360 ^o / n to each other, where n is the number of abrasive disks. For example, in a circle made up of three discs, the axis of symmetry Г ₁ О _{ш of the} first disk is positioned at a central angle β = 120 ^o to the axis of symmetry Г ₂ О _{ш of the} second disk and Г ₃ О _ш - of the third one (see Fig. 2).

When assembling a composite wheel, the installation of eccentric abrasive disks at equal central angles β to each other can be carried out, for example, using longitudinal marks Ж ₁ , Ж ₂ , Ж ₃ (see Fig. 5), which are applied to spindle 4.

In the extreme working position, for example, of the disk 2 (see Fig. 3) its axis O ₂ -O ₂ (see Fig. 1) is shifted by a distance ε from its geometric axis O _W - O _W , and ε> h, where h is the total allowance left for grinding. Another extreme position of this disk, when it is out of contact with the workpiece and rotated 180 ^o relative to the axis O _W - O _W spindle. As seen in FIG. 3, the second abrasive disk contacts the surface to be machined along the arc G ₂ D ₂ , through β = 360 / n = 120 ^{o the} rotation of the spindle, the third disk will enter into contact with the workpiece section G ₃ D ₃ , then the first disk section G ₁ D ₁ and etc. (see Fig. 4). In this way, an intermittent peripheral cutting surface of the assembly wheel is formed, contributing to a reduction in grinding temperature.

After the profile of each disk is worn in sections G ₁ D ₁ , G ₂ D ₂ , G ₃ D _3, they are rotated around the axis O _w -O _w
α _d = arccos [(D-2h) / D]
using the scale 11, applied on the rings 8, 9, 10, and continue grinding.

Under these conditions, the circle does not work on the entire peripheral surface, but in small sections G ₁ D ₁ , G ₂ D ₂ , G ₃ D ₃ . Therefore, these sections wear out first, and then other (not worn out sections, _etc. ) are introduced into the work (when the disks are turned through the angle α _d ). This allows maintaining a sufficiently high and identical accuracy of a large batch of parts due to grinding without additional restoration of the profile of the circle and helps reduce abrasive consumption.

 It should be noted that a circle with worn sections of the profile can be repeatedly used for preliminary grinding with the successive replacement of more worn sections with less worn ones. In this case, the total grinding depth should be less than the height of the profile remaining on the working area of the wheel.

 As the circle is used, the arc length of the contacts of the protrusions of the disks with the surface being machined increases due to self-sharpening, and the intermittent grinding process stabilizes: vibration decreases, heat stress decreases, surface quality improves, metal removal and productivity increase.

Example. Samples were processed from steel 12X18H10T (HRC 65 ... 75) with a composite circle of three electrocorundum 24A25CM17K43 PP disks 200x10x32 according to GOST 2424-83, inclined at an angle α = 6 ^o , on a surface grinding machine mod. 3E711IV. The grinding allowance is 0.3 mm. The disks were installed with an eccentricity ε = 0.5 mm, while the axis of symmetry of the disks were located at an angle β = 360 ^o / 3 = 120 ^{o to} each other. The longitudinal clearance between the discs was maintained with 5 mm spacers. Processing modes: tool rotation speed - 35 m / s, part feed longitudinal speed - 30 m / min, cutting depth in one pass t = 0.03 mm. Coolant - emulsion.

 Abrasive processing according to the proposed method of intermittent grinding made it possible to increase the cutting depth by 2 ... 2.5 times in comparison with the traditional one, in which a high-quality machined surface of the required roughness (Ra = 0.63 μm) was obtained without burns and microcracks due to the oscillating cutting zone and reduce the consumption of abrasive by 2 ... 2.4 times.

 Changing the kinematics of the grinding process by eccentric fastening the abrasive discs of the composite wheel and installing them at an angle to the axis of rotation reduces the grinding temperature, increases the dimensional and overall tool life, productivity and quality of processing.

Sources of information
1. A. p. 1742038 USSR, MKI V 24 V 1/00. The method of profile grinding.

 2. Patent 2123925 of the Russian Federation, MKI B 24 V 1/00, 5/02, 7/02. Discontinuous grinding method. Stepanov Yu.S., Afanasyev B.I., Borodin V.V. Application 98102725/02, decl. 02.16.98, publ. 12/27/98. Bull. 36 is a prototype.

Claims (1)

 Discontinuous grinding method, comprising communicating to a composite grinding wheel set at an acute angle to a plane perpendicular to the axis of rotation of the spindle, rotation and movement relative to the workpiece, characterized in that they use a grinding wheel composed of at least three abrasive disks, the axes of which are mounted eccentrically geometric the axis of the spindle with eccentricity ε by means of eccentric rings with a hole offset by a value ε from the outer surface, with the symmetries of the abrasive discs are placed at equal central angles to each other, and the eccentricity ε is chosen from the condition ε> h, where h is the total allowance for grinding.

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