RU2130375C1 - Method of working the holes by grinding wheel - Google Patents

Abstract

FIELD: mechanical engineering. SUBSTANCE: hole is worked by grinding wheel which center is positioned on spindle axis parallel to axis of hole being worked. Grinding wheel is rotated about spindle axis, and feed motion is imparted to it. Operating surface of grinding wheel is made spherical. Grinding wheel is positioned at angle α to spindle axis, and rotary motion about axis of its own is imparted to it. Angle α is determined by formula: α = arcsin(B/D)-arccos[(D-2t)/D], where B and D are height and external diameter of grinding wheel sphere, respectively; t is depth of grinding. Installation of grinding wheel axis at angle to axis of hole being worked and to spindle axis enables variation of angle of abrasive grain position relative to surface being worked. Grains are placed at different angles to cutting surface in different angular positions of grinding wheel. Thus principle of unique trace is realized, that is subsequent abrasive grains do not get into notches-scratches of preceding grains cut earlier. EFFECT: improved quality of working. 2 dwg, 1 ex

Description

 The invention relates to mechanical engineering and can be used for dimensional diamond abrasive processing in finishing operations.

 A known processing scheme, where a precast grinding wheel is used, made in the form of abrasive disks fixed to a common shaft with an axial clearance relative to one another and inclined to the plane of rotation / 1 /.

 A disadvantage of the known scheme is the low quality of processing, since abrasive grains rotate in parallel planes and most do not participate in cutting, because follow cutting, maximally protruding and working mainly front edges.

 As a prototype, the classical method of processing holes with a grinding wheel, the diameter of which is less than the diameter of the hole being machined, and the spindle axis is parallel to the axis of the hole / 2 /, is selected.

 A disadvantage of the known scheme is the low quality of processing, since abrasive grains work mainly with front faces, rotate in parallel planes and most do not participate in cutting, because follow the cutting, protruding as much as possible.

 The objective of the invention is the expansion of technological capabilities and ensuring improved processing quality.

The problem is achieved by the proposed method, which consists in the fact that with this method, the grinding wheel, the working surface of which is spherical, is set at an angle α to the axis of the spindle and a complex movement is reported: rotation around its own axis, feed movement along the axis of the hole being machined and rotation around the axis spindle, and the angle "alpha" is determined from the ratio
α = arcsin (B / D) -arccos [(D-2t) / D],
where B and D are respectively the height and outer diameter of the sphere of the grinding wheel;
t is the grinding depth.

 Setting the axis of the grinding wheel at an angle to the axis of the machined hole and the axis of the spindle allows you to change the angle of the abrasive grains relative to the machined surface.

 The grains become at different angles to the cutting surface at different angular positions of the grinding wheel. The principle of trace repeatability, i.e. subsequent abrasive grains do not fall into previously cut risk-scratches of previous grains. The method provides the possibility of improved processing quality, since all cutting grains rotate in various non-parallel planes and work both front and side faces.

 In FIG. 1 is a diagram of an implementation of a method for grinding a hole; in FIG. 2 - a device for implementing the method.

The geometric center O of the grinding wheel 1 (Fig. 1) is located on the axis of the spindle of the device, and the axis of the spindle of the device is parallel to the axis of the hole of the workpiece 2, as in the usual conventional internal grinding. The axis of the grinding wheel is set at an angle α to the axis of the spindle of the device and the axis of the hole of the workpiece 2. The peripheral working surface of the grinding wheel 1 is spherical with a sphere diameter D equal to (0.7-0.8) d _{3 the} inner diameter of the workpiece (for a new, again set grinding wheel).

The angle α is determined from the relation
α = arcsin (B / D) -arccos [(D-2t) / D],
where B and D are respectively the height and outer diameter of the sphere of the grinding wheel;
t is the grinding depth.

 At smaller angles of inclination of the axis, the grinding wheel will work only with a spherical peripheral surface, which improves the conditions of self-sharpening and machining accuracy. For large grinding wheels will work not only the periphery, but also the ends, and this reduces the dimensional stability and increases the consumption of abrasive material.

When processing the grinding wheel 1 reported traffic longitudinal feed S _ave and rotation around its axis with the rotation speed n _1, the axis of the grinding wheel moves over the cone with vertex in the geometric center O of the grinding wheel due to posts s rotation around the device axis of the spindle with a frequency n ₂ . In this case, the grinding wheel removes the allowance t equal to the transverse feed for each stroke or double stroke - S _tx .

 The device for implementing the method comprises a housing 3 in which a spindle 5 is mounted in the bearings 4. A flexible wheel 6 of the wave transmission 7 is connected to the spindle 5. A wave generator 8 is mounted on the drive shaft 9. The axis of the neck 10 of the output end of the spindle 5 is inclined at an angle α to the axis spindle 5. On the neck 10 on the bearings 11 mounted grinding wheel 1, the working surface of which is made spherical. The flange of the grinding wheel 1 is rigidly connected with the shaft 12, which in turn is connected by a flexible (cardan) connection 13 with the drive shaft 9. The drive shaft 9 is mounted in bearings 14 and 15, respectively, in the housing cover and spindle 5.

 A device for implementing the method of grinding holes works as follows.

When the rotation is communicated to the drive shaft 9, through the flexible (cardan) joint 13, the rotation is transmitted to the shaft 12, and from it through the flange to the grinding wheel 1, which rotates freely on the neck 10. Simultaneously, through the wave generator 8 of the wave transmission 7, the rotation is transmitted to the flexible wheel 6, which drives the spindle 5, on which a grinding wheel is mounted on the neck 10
Since the axis of the neck 10 is inclined at an angle to the axis of the spindle 5, and the flexible (cardan) connection 13 is located in the center of the grinding wheel 1, the axis of the latter makes a movement along the generatrix of the cone with the apex in the center of the grinding wheel.

As an example, the bore hole was machined on an intra grinding machine mod. ZK227V. Workpiece material Steel 45 GOST 1050-74, HB 260, diameter of the machined hole 130 mm, cutting tool - abrasive wheel PP 100 x 20 x 32 24A25PS25K8A. The angle of inclination of the axis of the grinding wheel α = 5 ^o 10 ′.
The dressing of a new grinding wheel and subsequent dressing were carried out by grinding with a diamond pencil using a special tool that allows you to get a spherical surface with a geometric center in T.O.

Processing modes: workpiece speed V ₃ = 40.8 m / min, n ₃ = 100 rpm), tool rotation speed - V ₁ = 31.4 m / s, tool rotation speed n ₁ = 6000 r / min, speed the spindle rotation of the device with the wave gear ratio i _B = 13 was V ₂ = 2.415 m / s, which corresponds to the spindle speed n ₂ = 461.54 rpm; longitudinal feed S _ol = 4 mm / rev workpiece, S _pop = 0.008 mm / stroke. Processing was carried out in 35 passes. Coolant - emulsion.

The specified roughness parameter R _a = 0.63 μm and the hole size with the necessary accuracy were achieved after 0.94 minutes, which is two times faster than with the usual grinding method.

 At the same time, favorable cutting conditions, vibration resistance, and minimal heating of the workpiece were noted. Although the treatment was carried out with increased metal removal performance, the appearance of burns and microcracks on the treated surface was recorded on. The presence of the angle of intersection of the trajectory of the grinding wheel with the direction of the initial roughness, which determines the trace network and the nature of the microgeometry as in honing, grinding with superposition of vibrations, is noted.

 The self-sharpening conditions of the abrasive grinding wheel have improved.

 Using the method increased the processing productivity by at least 2 times, eliminated the operation of semi-grinding due to the improvement of surface roughness by 1-2 classes. At the same time, the consumption of an abrasive tool decreased by 25%.

Claims (1)

The method of processing holes with a grinding wheel, the center of which is located on the axis of the spindle parallel to the axis of the hole being machined, and the grinding wheel is informed of a rotational movement around the axis of the spindle and a feed movement, characterized in that a grinding wheel with a spherical working surface is used, set it at an angle α to the axis spindle and tell the circle a rotational movement around its own axis, while the angle α is selected by the formula
α = arcsin (B / D) -arccos [(D-2t) / D],
where B and D are respectively the height and outer diameter of the sphere of the grinding wheel;
t is the grinding depth.

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