RU2237568C1 - Method of abrasive working - Google Patents

Abstract

FIELD: mechanical engineering.

SUBSTANCE: method includes using assembled tool made of at least three abrasive tab disks. The disks are secured at an angle to the plane perpendicular to the axis of rotation with an axial clearance. The middle disk is mounted on the shaft via a slide bearing for permitting free rotation with the frequency of rotation of a blank. The tabs are made of an ellipsoidal double-sided emery cloth and arranged transversely to the axis of rotation. The small axis of the ellipse is equal to the diameter of the disk. The great axis is determined depending on the inclination of the disks.

EFFECT: expanded functional capabilities.

2 cl, 8 dwg

Description

The invention relates to mechanical engineering for the machining of metals and can be used for grinding and polishing the surfaces of parts with their dimensionless final machining with flap wheels.

A known method of abrasive machining with a combined tool made in the form of a pair of abrasive wheels fixed at an angle to each other on a common shaft with an axial clearance [1].

The disadvantages of this method and tool are the limited technological capabilities for decorative finishing and finishing of shaped surfaces, as well as the difficulty in achieving a wide range of quality of the machined surfaces, while having minimal axial rigidity and working with only one side of the peripheral abrasive surface, it is impossible to achieve high performance.

A known method of abrasive machining with a combined tool made in the form of a pair of abrasive wheels fixed at an angle to each other on a common shaft with an axial clearance, the tool being provided with a tension spring located between adjacent ends of the abrasive wheels that are mounted with the possibility of angular rotation [2].

The disadvantages of the known method and tool are:

- minimum axial rigidity of the tool, not allowing to achieve high performance;

- work on only one side of the peripheral abrasive surface of the tool greatly increases the complexity of processing;

- limited technological capabilities for decorative finishing and finishing of shaped surfaces;

- difficulties in achieving a wide range of quality of the treated surfaces.

All this reduces processing productivity, quality and leads to increased tool consumption.

The objective of the invention is to expand the technological capabilities of the method by providing the possibility of processing with two ends of the petals of the tool, which is installed at an angle to the axis of rotation, increasing productivity by increasing the axial rigidity of the tool due to the use of abrasive petals in the form of an ellipse mounted across the axis, and also improving the quality of processing due to cross longitudinal-transverse intersection of the trajectories of the polishing wheels.

The problem is solved by the proposed method of abrasive treatment, in which at least three abrasive flap wheels are mounted on the spindle at an angle α to a plane perpendicular to the axis of rotation of the circles, with an axial clearance, and at the same time carry out preliminary and final polishing, for which at least one middle the circle is set by means of a bearing from the condition of rotation, with the rotation speed of the workpiece due to friction forces and oscillations of the working cutting layer of the circle, the middle circle consists of le of a tight, made of double-sided sanding and disposed transversely to the axis of rotation, wherein the petals are shaped like an ellipse whose minor axis is equal to the diameter of the tool, and the major axis is determined by the formula

b = D / cosα,

where b is the major axis of the ellipse, mm;

D is the outer diameter of the circle, mm;

α is the angle of inclination of the circles to a plane perpendicular to the axis of rotation, which is determined by the formula

α ≤ arctg (A _o / D),

where And _about - the amplitude of the oscillating cutting zone of inclined circles, taken - And _about ≤;

In - the height of the middle circle, mm

In addition, the remaining circles are rigidly fixed to the spindle and consist of petals located along the axis and are mounted radially.

At the same time, the graininess of the middle circle is one more than the graininess of the extreme circles.

The invention is illustrated by drawings.

Figure 1 shows the design of a precast abrasive wheel that implements the proposed method, a partial axial section; figure 2 - General view of the precast circle, rotated half a turn relative to the position shown in figure 1; figure 3 is a section aa in figure 1; figure 4 is a view along A ’in figure 1; figure 5 is an ellipsoidal petal from a double-sided grinding skin; in Fig.6 - element B in Fig.1, the position of the petals of the middle circle in the zone of contact with the treated surface; in Fig.7 - element B in Fig.2, the position of the petals of the middle circle in the zone of contact with the treated surface; on Fig - scan trace of the precast circle on the work surface when it is rotated by one revolution and the direction of movement of the abrasive grains of various circles.

The proposed method of abrasive processing - polishing is carried out by a prefabricated abrasive flap wheel and allows finishing in both longitudinal and transverse directions both with round and flat polishing.

In the middle circle, the working cutting elements of the prefabricated wheel are ellipsoid petals 1 of a double-sided grinding skin located across the axis of rotation, and the remaining circles are composed of petals of an abrasive skin located radially in the longitudinal direction.

The combined abrasive wheel is made in an amount of at least three abrasive flap wheels 2, 3 and 4, fixed at an acute angle α to a plane perpendicular to the axis of rotation, on a common spindle 5 with an axial clearance. The middle circle 3 is mounted on the spindle 5 by means of a bearing assembly 6 with the possibility of free rotation and consists of petals 1 made of double-sided grinding skin and located across the axis of rotation. The bearing assembly 6 includes a sleeve 7 with oblique ends and an angular arrangement of the axes of the inner and outer surfaces, a flange 8, which is mounted on a rolling bearing using spring thrust concentric rings (taken, for example, according to GOST 13940-80 and GOST 13941-80). On the flange 8 using the nut 9, the petals 1 of the movable circle 3 are fixed.

Petals 1 have the shape of an ellipse, the small axis of which is equal to the diameter of the tool, and the large axis depends on the angle of rotation and is determined by the formula

b = D / cosα,

where b is the major axis of the ellipse, mm;

D is the outer diameter of the circle, mm;

α is the angle of inclination of the circles to a plane perpendicular to the axis of rotation, which is determined by the formula

α ≤ arctan (A _o / D),

where And _about - the amplitude of the oscillating cutting zone of inclined circles, adopted And _about ≤;

In - the height of the middle circle 3, mm

The remaining circles are 2, 4, etc. rigidly fixed to the spindle using oblique washers 10, 11, nuts 12 and consist of petals located along the axis and are mounted radially (see figure 4).

The granularity of the middle circle 3 is greater by number than the extreme ones, i.e. the middle circle with a larger grain is intended for pre-polishing. Extreme circles 2, 4, etc. fine-grained are intended for finishing processing.

The prefabricated wheel is installed on a circular, internal or surface grinding machine, and the workpiece in the appropriate device. The rotation V is reported to the spindle 5, the tool is tightened by means of a transverse feed S _pop and a longitudinal feed to the workpiece S _pr , and also during circular and intra-grinding work, the workpiece is rotated. For a full spindle revolution, circles 2 and 4 smoothly change their angular position to the left and to the right of the normal by an angle α with respect to the work surface.

The circle 3, movably mounted with the help of the bearing assembly 6 on the spindle 5, is run around the machined surface and, thanks to its inclination in the contact zone with the workpiece, makes oscillating oscillations along the longitudinal axis of rotation.

Moving along the surface of the workpiece machined by circle 2, the movable circle 3 in the contact zone cuts off microroughnesses in the direction perpendicular to the risk-scratches cut by circle 2 (see Fig. 8); during the reverse stroke, moving along the machined circle 4. Due to the inclination of the middle circle and the interference carried out by S _pop , the main force on the surface being machined is carried out by the parts of the petals located on the periphery and having the greatest deflection (see Fig.6-7). The direction of the deflection of the petals varies depending on the angular position of the circle. If the contact zone of the middle circle with the workpiece is located to the right of the normal (see Fig. 6), then the direction of deflection is to the right, while the petals work with the left abrasive end, if the contact zone is to the left of the normal, then the direction of deflection is to the left, and the petals work with the right abrasive end (see Fig.7).

When polishing is carried out for a long time as the petals wear, under the action of the transverse feed S _{pop, the} weakened transverse interference is restored and the design provides an improved quality of processing in terms of reducing the roughness of the processed surface of the workpiece.

In connection with the foregoing, during this longitudinal-transverse polishing by the proposed method, it is possible to remove large allowances (for example, up to 0.3 mm) when using coarse abrasive skins (grain size 16-80) and high cutting speeds (15-35 m / s).

This process is actually a form of grinding and is effective for preparing surfaces for fine polishing and before metal coating.

Polishing by the proposed method with a prefabricated flap wheel is intended to reduce the surface roughness parameter (to Ra = 0.1 ... 0.8 μm) without eliminating the deviations in the shape of the parts.

The greatest effect of the use of oscillating polishing is achieved during decorative finishing and finishing of shaped surfaces, for example, polishing cylindrical and conical surfaces, processing of molds, dies, etc., polishing curved surfaces of automobile bodies, refrigerators, and others for painting.

Polishing by the proposed method is carried out mainly according to one cutting pattern, which is based on the use of high cutting speeds (10 ... 40 m / s), approaching the grinding speed. The peripheral speed of a circle during oscillating polishing of parts made of steel, nickel and chromium is 20 ... 35 m / s; copper, brass and bronze - 16 ... 25 m / s; aluminum, zinc and lead - 12 ... 20 m / s.

However, low speeds S _{pr the} movement of the workpiece (which is typical for flat polishing) contribute to improving the quality of processing.

The most applicable for the proposed method are circles made of electrocorundum and silicon carbide skins on a fabric and paper basis with a grain size of 8-M40, as well as diamond and elbor skins with a grain size of 12-MZ on an elastic bond, while the latter are highly resistant.

To work on this method, circles of water-resistant diamond-abrasive skins are used when processing parts made of steel, cast iron and brass, an emulsion is used as a cooling liquid; from non-waterproof skins - mineral oils.

The proposed method prefabricated petal wheel expands technological capabilities by providing the possibility of processing with two ends of the petals that make up the middle circle, improves productivity and quality of processing by installing circles at an angle to the axis of rotation and free installation of one of the circles, increasing axial stiffness due to the use of abrasive elliptical petals.

Sources of information

1. A.S. USSR 689823, MKI B 24 D 5/00. Prefabricated abrasive tool, 1977.

2. A.S. USSR 1692824, MKI B 24 D 13/00. Prefabricated abrasive tool. A.V. Chemersky and V.N. Cheshev, No. 4700372/08, declared 04/18/89, publ. 11/23/91, Bull. No. 43 is a prototype.

Claims (3)

1. The method of abrasive treatment, in which at least three abrasive flap wheels are mounted on the spindle at an angle α to a plane perpendicular to the axis of rotation of the circles, with an axial clearance, characterized in that simultaneously carry out preliminary and final polishing, for which at least one the middle circle is established by means of a bearing from the condition of rotation with the rotation speed of the workpiece due to friction and oscillation of the working cutting layer of the circle and consists of petals made of double-sided grinding Shaft skins and disposed transversely to the axis of rotation, wherein the petals are shaped like an ellipse whose minor axis is equal to the diameter of the circle, and the major axis is determined by the formula b = D / cosα, where b is the major axis of the ellipse, mm; D is the outer diameter of the circle, mm; α is the angle of inclination of the circles to a plane perpendicular to the axis of rotation, determined by the formula α ≤ arctg (A _o / D); A _o - the amplitude of the oscillating cutting zone of inclined circles, taken A _o ≤ B; In - the height of the middle circle, mm 2. The method according to claim 1, characterized in that the remaining circles are rigidly fixed to the spindle and consist of petals located along the axis and mounted radially. 3. The method according to claim 1 or 2, characterized in that the graininess of the middle circle is more than the graininess of the extreme circles.

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