RU2252854C1 - Combined grinding and honing method - Google Patents

Abstract

FIELD: machine engineering, possibly effective finishing diamond-abrasive working of blanks of different metals having tendency for occurring flaws.

SUBSTANCE: method comprises steps of using combined tool having grinding disc and hone and also device for mounting them on mandrel by acute angle relative to plane normal to rotation axis; at working surfaces of revolution imparting to blank and to combined tool rotation and feed motion along worked surface; using hone having separate diamond-abrasive bars with different grain size secured to outer surface of tore-like elastic envelope; restoring worn outer diameter of hone due to supplying compressed air into elastic envelope until increasing its diameter till diameter of grinding disc.

EFFECT: enhanced efficiency and quality of working, increased useful life period of tool, quick change of one mode to other without interruption of process.

8 cl, 8 dwg

Description

The invention relates to mechanical engineering, namely to diamond-abrasive processing of materials by cutting with a combined tool with an adjustable diameter and angle of inclination of the cutting layer relative to the axis of rotation, and can be used at machine-building enterprises for the effective finishing of workpieces from various materials susceptible to defect formation.

A known method, carried out by a discontinuous abrasive wheel with an elastically damping element, compares favorably with processing by solid and other abrasive wheels in terms of productivity and quality of the surface layer of products [1]. The method made it possible to ensure high uniformity and strength of the abrasive segments, to assign increased cutting conditions in comparison with traditional abrasive wheels. An elastic-damping element introduced into the structure dampens shock pulses that occur when segments come in and out of contact with the workpiece, stabilizing the processing process and eliminating vibrations, which in turn improves the quality and productivity of processing [2].

The disadvantages of this method [1] is the lack of broad technological capabilities that allow roughing, semi-finishing, finishing and finishing abrasive processing, the inability to quickly switch from one mode to another, the inability to restore the wearing diameter of the tool, and the occurrence of burns and grinding microcracks with increasing cutting conditions and increased productivity.

The closest prototype is a combined method of quasi-continuous finishing, implemented using a combined tool head [3]. The head consists of a circle and a disk with abrasive radially expandable bars, which are run in a circular direction along the surface to be treated.

The disadvantages of this method are the lack of broad technological capabilities that allow roughing, semi-finishing, finishing and finishing abrasive processing, the inability to quickly switch from one mode to another, the inability to restore a worn out outer diameter, as well as the appearance of burns and grinding microcracks with increasing cutting conditions and increasing performance. In this case, shock pulses arising at the entrance and exit of the bars from contact with the workpiece destabilize the processing process and lead to vibrations, which in turn reduces the quality and productivity of processing

The objective of the invention is to increase productivity, processing quality and tool life by quickly restoring the outer diameter of the hone and changing the amplitude of the axially displaced cutting layer, stabilizing the processing process and eliminating vibrations by introducing an elastic damping element into the structure and the possibility of a diamond abrasive processing of a quick transition from a draft mode to a semi-finishing, finishing and finishing.

The problem is solved by the proposed combined grinding method, in which for processing the surfaces of rotation of the workpiece and the combined tool with a grinding wheel and hon located in it with working elements and the device for fastening them to the mandrel at an acute angle to a plane perpendicular to the axis of rotation, rotational movements and movement are reported feed along the machined surface, for processing flat surfaces to the combined tool rotational movement and move feeding across the surface to be machined, and the workpiece reciprocating along the surface to be machined, the hone consisting of separate diamond-abrasive bars with different grain sizes, mounted on the outer surface of the toroidal elastic shell, while restoring the worn out outer diameter of the hone is carried out by supplying a compressed air into the elastic shell from the condition of increasing the diameter to the size of the diameter of the grinding wheel. In addition, to give greater rigidity to the toroidal elastic shell, its inner surface is divided by partitions into compartments communicating with each other, while the partitions are located under bars with larger diamond-abrasive grains.

In addition, the circle and hone are mounted on a mandrel at an acute angle α to a plane perpendicular to the axis of rotation, using oblique washers located at the ends of the tool, while the angle α is assigned by the formula

α <arctan (B _w / D _w ),

where D _W and _{W W} - respectively, the outer diameter and height of the grinding wheel.

The combined method allows roughing to be performed only in a circle without participation in the operation of a hone with a diameter of the latter less than the diameter of the circle by the amount of interference N.

In this case, the semi-finished treatment is performed simultaneously with a circle and a hone with a hone diameter greater than the diameter of the circle by the amount of interference N with which the tool is pressed against the workpiece.

In addition, finishing is carried out only with hon, when its diameter is greater than the diameter of the wheel by the amount of interference N, and all the bars of the hon are involved in cutting, and the grinding wheel does not touch the work surface, due to the fact that the tool is pressed against the workpiece by half the interference value - N / 2 .

The combined method allows finishing processing, which is carried out only by hone with its diameter larger than the diameter of the circle by the interference value N, and only fine-grained hone bars located on the elastic shell in places without partitions participate in the cutting, and the grinding wheel and coarse-grained hone bars do not touch the workpiece surface.

Moreover, in the combined method, the depth of incision of the hone is set by changing the pressure in the toroidal elastic shell.

Figure 1 shows the design of a combined grinding tool, which implements the proposed combined method of grinding, a partial longitudinal section; figure 2 - a view of figure 1; figure 3 is a cross section bB in figure 1; figure 4 is a partial longitudinal section of a tool with the maximum worn hon; 5 is a General view of the tool with a zero angle of inclination of the cutting layers; Fig.6 is a diagram of the finish processing only hone; Fig.7 - the position of the honing bars during the operation of the hon in the finishing processing mode; on Fig - scan trace of the combined tool on the treated surface, operating in a semi-finished processing mode.

The proposed combined method of grinding is carried out by a tool that allows for joint and sequential processing of the grinding wheel and honing stones having a peripheral axially offset cutting layer.

At the same time, for processing the surfaces of rotation of the workpiece and the combined tool with a grinding wheel and hon located in it with working elements and the device for fastening them to the mandrel at an acute angle to a plane perpendicular to the axis of rotation, rotational movements and feed motion along the surface to be treated are reported, and for processing rotary motion and feed motion across the machined surface are reported to the combined tools on the flat surfaces, and the reciprocating motion is transmitted to the workpiece along the work surface.

The combined grinding and polishing tool that implements the method contains hone 1 and grinding wheel 2, mounted on one mandrel 3.

Hon 1 is prefabricated and consists of separate diamond-abrasive bars mounted on the outer surface of the toroidal elastic shell 4 by means of plates 5. To give greater rigidity to the toroidal elastic shell 4, its inner surface is divided by partitions 6 into compartments 7 communicating with each other [2]. Such a fastening device for the assembled hone 1 allows you to quickly, on the fly, restore the worn outer diameter of the hone by supplying compressed air P _cr to the elastic shell 4 from the condition that the diameter D _{x be} increased to a size greater than equal to or less than the diameter D _{w of the} grinding wheel 2 by the tightness N, with which the tool is pressed against the part, depending on the selected machining mode.

Diamond abrasive bars of hone 1 are taken on a flexible, for example rubber, base and their fastening to the plates 5 is carried out by gluing, while the plates 5 themselves are mounted on a toroidal elastic shell 4 by vulcanization. Hon 1 is composed of separate diamond-abrasive bars with different grain sizes. The bars with larger diamond abrasive grains 1 ^k for finishing are placed above the partitions 6 of the toroidal elastic shell 4, and the fine-grained bars 1 ^m for finishing processing are placed above the compartments 7 without partitions (Figs. 3, 5).

A toroidal elastic sheath 4 is mounted on the glue on the mandrel 3 using restrictive washers 8, oblique washers 9 and secured with a nut 10 with a washer 11.

Actuation of the operating state of a toroidal elastic sheath 4 is carried out by feeding the sheath 12 and through the transverse central longitudinal hole 13 disposed in the mandrel 3, nipple and nipple (not shown) under the pressure of compressed air P _{compression channel.}

Thanks to the oblique washers 9 located in pairs from the ends of the combined tool, hon 1 and circle 2 are set at an acute angle α to a plane perpendicular to the axis of rotation, while the angle α can vary from zero (Fig. 5) to the value assigned by the formula

α <arctan (H _w / D _w ),

where D _W and _{W W} - respectively, the outer diameter and height of the grinding wheel.

Assembly tool is as follows.

The oblique washers 9 are located on the mandrel 3 with a maximum thickness in diametrically opposite places from each end of the tool, two pieces. After installing the circle 2 and the restrictive washer 8 on the mandrel 3, install the spacer sleeve 14 and combine the hole in it with the hole 12. On the sleeve 14 fasten by gluing the toroidal elastic shell 4, pre-assembled with plates 5 and bars 1. Thus combined on the mandrel 3 the tool is fixed with a nut 10 through washers 8, 9 and 11.

Work on the proposed method is as follows.

The tool is mounted on a mandrel, which is reported rotation, and is brought to the work surface. With round grinding, the tool is informed of the longitudinal and transverse feed, and the workpiece is rotated. With flat grinding, the tool is given a transverse feed, and the workpiece is given a longitudinal feed and a feed feed.

For a complete revolution of the hone 1 and grinding wheel 2, their cutting zones located on the periphery will move along the axis of rotation equal to the amplitude A _x (Fig. 8).

Due to this axial displacement of the working cutting layer of the wheel and hon in the section A _x in the cross section, intermittent grinding and honing is observed, which is accompanied by a low cutting temperature compared to traditional grinding and honing and which guarantees a diamond-free abrasive machining.

In addition, honing is distinguished by blast-free processing, since its working cutting surface is intermittent, which allows to reduce the temperature of the surface layer at the time of interruption of the cutting process.

Grinding with a circle is a continuous cutting process that provides oscillation of the thermal field due to the increase in the contact length of the wheel 2 and the workpiece by the amplitude A _x , which depends on the angle α of the inclination of the wheel and its outer diameter D _w .

The angle of the circle allows you to increase the number of diamond-abrasive grains involved in cutting [3].

Following treatment with the surface grinding is conducted diamond abrasive processing movably fixed, honing stones, having the possibility of radial movement and pressed to the surface with a certain force, which can be constant or vary depending on the pressure P _{compression channel} compressed air supplied to the toroidal elastic sleeve.

The combined method can be implemented in several modes with a quick transition from one mode to another without stopping the process:

- roughing is carried out only with a grinding wheel without participation in the hone, when the diameter of the latter is less than the diameter of the wheel by the amount of interference N, i.e., when D _x <D _w . To do this, stop the flow of compressed air into the toroidal elastic shell and pass it into the atmosphere;

- the semi-finished treatment is performed simultaneously with a circle and a hone with a hone diameter greater than the diameter of the circle by the amount of interference N with which the tool is pressed against the workpiece, i.e. for D _x > D _w To do this, increase the pressure of compressed air in a toroidal elastic shell;

- finishing is carried out only with hon, with its diameter greater than the diameter of the circle by the amount of interference N, i.e. for D _x > D _w Moreover, all hone bars are involved in cutting, and the grinding wheel does not touch the work surface due to the fact that the tool is pressed against the workpiece by half the interference value - N / 2 (Fig. 6);

, чем крупнозернистые (на

), по причине того, что они находятся на упругой оболочке, не связанной с перегородкой, в связи с тем, что последняя менее эластична.- finishing processing is carried out only by hone with its diameter greater than the diameter of the circle by the amount of interference N, i.e. for D _x > D _w Moreover, only fine-grained hone bars located on the elastic shell in places without partitions participate in the cutting, and the grinding wheel and coarse-grained hone bars do not touch the surface to be treated (Fig. 7). Fine-grained bars are located on a larger diameter

than coarse-grained (on

), due to the fact that they are on an elastic shell that is not connected with the partition, due to the fact that the latter is less elastic.

In all modes, where working hone, honing depth can be varied and controlled pressure value P _{compression channel} compressed air supplied to the elastic toroidal shell.

Combined grinding tool operating according to the proposed method allows processing using the entire peripheral working part of the tool and preserving the advantages of intermittent grinding and honing processes.

Processing productivity increases by 2 ... 2.5 times, and surface roughness - by 1 ... 2 classes, while the consumption of diamond-abrasive material is reduced by 25 ... 30%.

Industrial tests were carried out on a mod grinding machine. 3K228B, where a through hole was polished with a diameter of D _s = 60 N7 ( ^+0.03 ) and a length of l = 60 mm. The roughness parameter of the machined surface is R _a = 0.63 μm. Side allowance h = 0.2 mm. The workpiece material is steel 45, hardened, hardness HRC 45. The machine is equipped with a device for active control of workpieces. The full feature of the grinding wheel recommended for this steel is 24A25PS25K8A. For internal grinding, it is recommended that D _k / D _z = 0.8, ... 0.9. Therefore, a circle with a diameter of D _k = 50 mm was taken. Processing was carried out under the following cutting conditions. The rotational speed of the tool was taken n _to ~ 13000 min ^-1 ; the rotation frequency of the workpiece - n _s = 200 min ^-1 . The longitudinal feed according to the recommendation was set S _m = 5390 mm / min.

Cross feed for normal circles recommended S _{t dv.kh} = _0,004 mm / dv.khhod. For this special tool, S _{t dv.x} = 0.006 mm / dv.hod was taken.

Abrasive whetstones: coarse-grained - grain material 63C, grain size M40, hardness CM1, bond - bakelite, number of whetstones - 3, length of whetstones - 30 mm, width of whetstones - 16 mm; fine-grained - grain material 63C, grain M20, hardness M1, binder - bakelite, number of bars - 3, length of bars - 30 mm, width of bars - 16 mm.

Coolant - emulsion.

Processing was carried out in 20 passes: of which

- 8 passes in rough grinding mode,

- 6 passes in the mode of semi-final grinding,

- 4 passes in the final grinding grinding mode,

- 2 passes in the finishing grinding grinding mode.

The angle of inclination of the grinding wheel and hone with abrasive bars α = 10 °. The amplitude in this case was A = 8 mm. The radial pressure in the toroidal elastic shell was 0.4 ... 0.6 MPa.

To ensure the required quality and dimensional accuracy of the processing, the main time T _o = 0.6 min was required, which is 2 times faster than with conventional grinding. The use of the combined grinding method allowed to exclude the operations of semi-grinding and honing due to the improvement of surface roughness by 1-2 grades. At the same time, the consumption of abrasive tools decreased by 30%.

Studies have shown that the proposed method and tool, combined with a high rotation speed and sinusoidal oscillation in the longitudinal direction of the heat field, intensifies the processing process due to an increase in the length of the arc of contact between the tool and the workpiece, the presence of the angle of intersection of the trajectory of the grinding wheel and hone with the direction of the initial roughness, causing a trace network and the nature of microgeometry as with honing, grinding with vibrational superposition (Fig. 8). Self-sharpening conditions of the grinding wheel and hone are improved.

Using the proposed combined method can improve the efficiency of the grinding tool as a whole, as well as parts of it - hone with movable fastening of diamond-abrasive bars through the use of a toroidal elastic shell. Execution of the tool by the teams allowed to ensure high uniformity and strength of the abrasive segments, to assign increased cutting conditions compared to traditional abrasive wheels. An elastic-damping element introduced into the structure dampens shock pulses that occur when segments come in and out of contact with the workpiece, stabilizing the processing process and eliminating vibrations, which in turn increases the quality and productivity of processing. A quick transition from one processing mode to another due to a change in pressure in the elastic shell allows high-efficiency and high-quality removal of significant allowances, i.e. work in difficult conditions.

The combined method of grinding honing broadens the technological capabilities of processing due to the combination of honing and grinding, reduces auxiliary time, increases processing productivity by 2 ... 2.5 times, improves the quality and roughness of the processed surface, and the tool is simple in design and reliable in operation.

Sources of information

1. A.S. 446408 USSR, MKI B 24 D 13/02. Intermittent abrasive wheel. Ignatov S.N., Trishin V.M., Nizhnikh I.V. and other Application No. 1871 201 / 25-8, application. 1/15/73; publ. 10/15/74. Bull. Number 38.

2. French patent 2654027, MKI B 24 V 9/14. A surface treatment tool that automatically takes the appropriate shape. Application 11/06/1989, publ. 10/05/1991. VINIPI number 19.

3. Patent 2120368 of the Russian Federation, MKI V 24 V 5/00, 1/00. The method of combined quasi-continuous finishing. Stepanov Yu.S., Afanasyev B.I. and others. Application 96116348/02, decl. 08/07/96; publ. 10.20.98. Bull. No. 29 is a prototype.

Claims (8)

1. The combined grinding method, in which for processing the surfaces of rotation of the workpiece and the combined tool with a grinding wheel and hon located in it with working elements and their mounting device on a mandrel at an acute angle to a plane perpendicular to the axis of rotation, rotational movements and feed motion along the surface being machined, and for processing flat surfaces, the rotary movement and the feed motion across the surface to be machined are reported to the combination tool sti, and the workpiece - reciprocating movement along the machined surface, characterized in that they use a hone, consisting of separate diamond-abrasive bars with different grain sizes, mounted on the outer surface of the toroidal elastic shell, while restoring the worn out outer diameter of the hone by feeding compressed air into the elastic shell from the condition of increasing the diameter of the hone to the size of the diameter of the grinding wheel. 2. The combined method according to claim 1, characterized in that to impart greater rigidity to the toroidal elastic shell, its inner surface is divided by partitions into compartments communicating with each other, and the partitions are placed under bars with larger diamond-abrasive grains. 3. The combined method according to claim 1, characterized in that the grinding wheel and hon are mounted on the mandrel at an acute angle α to a plane perpendicular to the axis of rotation using oblique washers located at the ends of the tool, the angle α being selected by the formula: α <arctan (B _w / D _w ), where D _W and _{W W} - respectively, the outer diameter and height of the grinding wheel. 4. The combined method according to claim 1, characterized in that the roughing is carried out only by the grinding wheel without participation in the work of the hone when the diameter of the latter is less than the diameter of the wheel by the amount of interference N. 5. The combined method according to claim 1, characterized in that the semi-finished processing is carried out simultaneously with a grinding wheel and hone with a hone diameter greater than the diameter of the wheel by the amount of interference N with which the tool is pressed against the workpiece. 6. The combined method according to claim 1, characterized in that the finishing is carried out only with hone, with its diameter greater than the diameter of the wheel by the amount of interference N, and all the hone bars are involved in the cutting, and the grinding wheel does not touch the work surface due to the fact that the tool is pressed to the workpiece at half the interference value N / 2. 7. The combined method according to claim 1, characterized in that the finishing treatment is carried out only with hon when its diameter is greater than the diameter of the circle by the amount of interference N, and only fine-grained hon bars located on the elastic shell in places without partitions are involved in the cutting, and the grinding wheel and coarse grained hon bars do not touch the work surface. 8. The combined method according to claim 1, characterized in that the depth of incision of the hone is set by changing the pressure in the toroidal elastic shell.

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