RU2155661C2 - Method of surface grinding by wheel with intermittent and continuous operating surface - Google Patents

Abstract

FIELD: deep peripheral grinding. SUBSTANCE: method is used for deep grinding of materials predisposed to formation of defects such as burns and cracks. Grinding of surfaces is performed by wheel with intermittent and continuous operating surface. Use is made of grinding wheel with body shaped as truncated cone and with abrasive-carrying ring mounted by means of locks. Ring has roughing sections positioned on side of end faces and finishing section arranged between them. Rotation is imparted to wheel, and the latter moves with respect to article being machined. Abrasive- carrying ring is mounted on body so that roughing sections overhang above body. They are provided with intermittent operating surface and with hollows in form of through radial recesses and cantilever damping projections. In process of grinding roughing sections distribute allowance between cutting grains of damping projections uniformly due to pliability of cantilever projections and serve as roll-threading lip. Finishing section is calibrating part of wheel. Grinding method makes it possible to enlarge cutting capabilities, to enhance cutting tool strength and to extend period of wheel burnless operation due to use of intermittent grinding. EFFECT: improved quality of machined surface. 5 dwg

Description

 The invention relates to deep peripheral grinding of materials susceptible to defect formation in the form of burns and cracks.

 A known method of processing parts with an abrasive wheel having a zone of increased wear and areas not subjected to increased wear, having a relief in the form of protrusions surrounded by closed grooves, under conditions of relative movement of the circle and the part [1].

 The disadvantage of this method is the reduction in processing productivity and tool life, having areas with formed wearing microrelief. In addition, the formation of protrusions by chipping abrasive grains sharply reduces the active cutting ability of the circle and the number of cutting grains. The grains of the protrusions, surrounded by closed grooves and devoid of connection with neighboring grains, quickly crumble due to loss of strength of the ligament and the circle quickly loses its cutting properties and dimensional accuracy.

 The objective of the invention is to improve the quality of the machined surface, increasing the tool life and processing productivity in a continuous process while maintaining the advantages of intermittent grinding.

 The problem is solved by the proposed method of grinding surfaces in a circle with an intermittent and continuous working surface, while the grinding wheel is informed of the rotation and movement relative to the workpiece, in addition, they use a grinding wheel consisting of a case in the form of a truncated cone and an abrasive ring mounted on it, having, from the side of the ends, draft sections cantilever hanging over the body with a discontinuous working surface and a number located between them a commercial section with a continuous working surface, and the discontinuous working surface of the draft sections has hollows in the form of through radial grooves forming cantilever damping protrusions, due to the flexibility of which the rough sections evenly distribute the grinding allowance between the cutting grains of the damping protrusions and perform the functions of the intake cone.

 In FIG. 1 shows a distribution pattern of stock between cutting grains of a cantilever damping protrusion; in FIG. 2 - grinding wheel with a discontinuous and continuous peripheral surface, a longitudinal section; in FIG. 3 is a view B in FIG. 2; in FIG. 4 is a general view of the grinding wheel with rough from the end side and the finishing, located between them sections; in FIG. 5 - the same, second option, where the grooves of the draft sections are staggered.

 Processing of blanks by the proposed method is performed by a grinding wheel with intermittent 1 and continuous 2 sections of the peripheral working surface. In this case, the grinding wheel consists of a housing 3 in the form of a truncated cone with a base surface 4, on which an abrasive bearing ring 5 is installed, having a similar landing conical surface 6.

 To fix the abrasive ring 5 on the housing 3, screws 7 are used, which are screwed into the holes located on the generatrices of the cones, the combined seating surfaces of the housing and the ring. Due to the fact that the threaded surface in the hole for the screw 7 is made only on the body 3, the screw 7 when it is screwed in exerts pressure on the ring 5, producing the axial displacement of the latter relative to the housing 3. The screws are provided with slotted grooves for the screwdriver.

 The abrasive bearing ring 5 has discontinuous sections 1 of the peripheral working surface, which are located coaxially at the ends, and placed between them section 2 with a continuous peripheral working surface. The landing surface 6 of the abrasive ring 5 is located under section 2 with a continuous peripheral working surface, and the discontinuous sections 1 of the peripheral working surface of the ring cantilever overhang the casing 3.

 The discontinuous sections 1 of the peripheral working surface of the ring 5 have depressions in the form of through radial grooves 8, forming cantilever damping protrusions 9, which ensure the operation of the discontinuous sections of the circle in the damping mode.

 When the wheel is operating, the cantilever damping protrusions 9, successively crashing into the surface to be treated, remove the layer 10, while, as follows from FIG. 1, due to the flexibility of the cantilevered protrusion 9 of the intermittent grinding section 1 by the value t (cutting depth), the distribution of the allowance between the cutting grains changes in the direction of a more uniform distribution among themselves, i.e. the allowance distribution pattern approaches ordinary grinding in a continuous circle with a fence cone when the allowance begins to be cut from a minimum to a maximum. In addition, the intermittent sections of 1 circle when grinding with a longitudinal feed cut off the entire allowance in the intermittent cutting mode, and section 2 performs finishing and serves as a calibrating part of the tool, which forms the final roughness and accuracy of the machined surface.

 The implementation of the damping protrusions 9 cantilever in the form of springs makes it possible to smoothly increase the load on the cutting grains located on these protrusions during the entry of the rough grinding section into the processed material, which is equivalent to maintaining a constant cutting rigidity and, accordingly, optimal processing conditions both for impacts and vibrations, and according to distribution of the removed allowance between the cutting grains of a circle.

The departure length of the cantilever damping protrusion is determined from the value of the greatest deflection, taken equal to the cutting depth t, according to the formula
l = (3EJ _x t / P _y ) ^1/3 ,
where E is the modulus of longitudinal elasticity;
J _x = ba ^3/12 - axial moment of inertia of the cross section of the console damping protrusion about the longitudinal axis;
bx a - cross-sectional dimensions of the cantilever damping protrusion;
P _y is the radial component of the cutting force.

 Intermittent cutting by the damping protrusions of section 1 with the subsequent continuous machining by section 2 of the grinding wheel according to the proposed method allows to increase the cutting conditions and the runtime of the wheel until structural changes (burns) occur in the surface layer of the machined parts, reduce the greasing of the wheel, heat stress of the grinding process, forces cutting, etc., which leads to an increase in the quality of the grinding surface.

Comparative tests of known continuous circles and circles by the proposed technical solution have been carried out. The surface of the plank was 110 mm wide; 280 mm long. The height of the strap is _20-0.05 mm; allowance on the side of 0.35 mm; roughness parameter R _a = 1.25 μm; the workpiece material is steel 45 GOST 4543 - 81, hardness HRC 50. Six workpieces (in two rows, three workpieces in each) were installed on the magnetic rectangular table of the surface grinding machine model ZP722.

Grinding was carried out according to the proposed method with a grinding wheel consisting of a body made of aluminum alloy and a steel ring with an abrasive layer attached by gluing. Marking of the full circle characteristics - ПП 14А 25П СМ2 6Б2 35 m / s. The diameter of the new circle is 450 mm; height (width) - 80 mm. The length of the cantilever damping protrusion is l = 21 mm; the cross-sectional dimensions of the cantilever damping protrusion - and xb = 5 x 20 mm; the width of the cavity (groove) is 9 mm. Cutting modes: circle speed at an adopted peripheral speed of 35 m / s - n _k = 1500 min ^-1 ; workpiece movement speed - 16 m / min; cross feed of a circle - 32 mm / table stroke; vertical feed of the circle to a depth of passage S _tx = 0.03 mm (to reverse the grinding headstock). Coolant - emulsion.

The specified roughness parameter R _a = l, 25 μm and the size of the height of the strip with the required accuracy were achieved after 0.99 min, 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, no burns and microcracks appeared on the treated surface.

 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 one third.

The inventive method of grinding surfaces in a circle with a discontinuous and continuous working surface allows you to:
- increase the resistance of the cutting tool having discontinuous sections with cantilever damping protrusions, which, due to the provision of damping operation, create favorable cutting conditions;
- to increase the period of free running of the wheel due to the use of the effect of intermittent grinding, which allows to reduce the heat stress in the contact zone with the treated surface;
- increase processing productivity and tool life.

Sources of information
1 Auto USSR N 1542788, class 24 V 53/04, Bull. N 6, 1990.

Claims (1)

 A method of grinding surfaces in a circle with an intermittent and continuous working surface, characterized in that the grinding wheel is informed of rotation and movement relative to the workpiece, using a grinding wheel consisting of a case in the form of a truncated cone and an abrasive bearing ring mounted on it, having the ends of the draft sections cantilever overhanging over the body sections with a discontinuous working surface and the finishing section located between them with continuous working surface, the working surface roughing discontinuous portions having cavities in the form of through radial slots forming dampening projections cantilever due pliability which rough portions uniformly distributed machining allowance for grinding grains damping between the cutting ridges and the function of the intake cone.

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