RU2365484C1 - Method for centrifugal processing of parts and device for its realisation - Google Patents

Abstract

FIELD: technological processes, metal working.

SUBSTANCE: invention is related to the field of machine building and may be used in grinding, polishing and strengthening of internal surfaces of rings or bushes, mostly with complicated profile, by granulated working mediums. Parts are installed in container. Processing medium is supplied and sectionally compacted by tool with radial blades until abrasive bars are created inside processed surface. Radial gap Δr is set between tool blades and processed surface, value of which is selected based on the following condition: Δr ≤5Z, where Z is size of the main fraction of particles of processing medium. Tool blades are arranged with longitudinal slots, in which replaceable pads are fixed in the form of plates with transverse slots for location of fastening elements. Cylindrical tail of tool is installed with the possibility of rotation in cover, which tightly seals container. Container is arranged with two cylindrical belts and is rigidly joined to enveloping mount holder. The latter is installed in vibrator body by means of conic tailpiece. Annular bores are arranged on container and holder walls with creation of sealed toroid cavity connected to system of forced circulation of cooling liquid.

EFFECT: improved efficiency and quality of processing.

5 cl, 6 dwg, 1 ex

Description

The invention relates to finishing and hardening processing of parts and can be used for grinding, polishing and hardening with granular working media of the inner surfaces of rings or bushings, mainly of a complex profile, in machine and instrument engineering.

There are various methods of treating parts with a hydroabrasive medium, in which the treatment is carried out with continuous circulation of the suspension relative to the surfaces of the parts, and the abrasive fraction of the suspension is compacted by centrifugal forces arising from the rotation of a drum or sectional tool equipped with radial blades [1, 2, 3, 4 ], as well as devices for their implementation [5, 6].

In known methods and devices, the processing is carried out by free abrasive particles located in a liquid, which are compacted by transforming the abrasive fraction of the suspension into a dense cutting layer or bars during rotation of the drum or multi-section blade tool.

A disadvantage of the known methods and devices is the instability of quality indicators of the surface along the inner profile of the rings or bushings after processing.

The compaction of abrasive particles by rotation of a drum with a hydroabrasive suspension does not allow creating the contact pressure necessary for processing on internal surfaces by partially immersing a part in a compacted abrasive layer formed on the periphery of a rotating drum.

More effective for treating the inner surfaces of rings or bushings is the compaction of the abrasive slurry by rotating the sectional tool with radial blades until dense abrasive bars are moved in the inter-blade space, moving at high speed relative to the surface being treated.

However, it is difficult to provide a radial clearance at which there will be no slipping of abrasive particles relative to the impeller blades, especially during multi-transition processing, when polishing is carried out with a change in the grain size of the grinding material to reduce particle size. In addition, unequal contact pressure in different sections of the shaped profile eliminates uneven allowance and reduces the accuracy of machining parts.

Devices for the implementation of centrifugal processing provide the transformation of particles of a hydroabrasive slurry into a cutting tool during rotation of a drum or sectional tool equipped with blades. The compaction of the particles of the abrasive fraction of the suspension occurs under the action of inertial forces arising from the rotation of the drum or tool equipped with blades. A disadvantage of the known devices is the problematic nature of the processing of the internal surfaces of parts with a complex shape of the working profile, since with an increase in the radial clearance between the impeller blades and the machined surface, the metal removal rate decreases and the required qualitative surface characteristics are not achieved.

Closest to the claimed invention are the "Method of processing products" according to ed. testimonial. No. 468769 [2] and "Machine for polishing with a free abrasive of hollow products" by ed. testimonial. No. 831573 [6].

A feature of the prototype method is the sealing of a hydroabrasive working medium with a sectional tool with a continuous supply of abrasive mixture into the treatment zone. However, with an increase in the depth of the part’s profile, dense bars slip relative to the impeller blades, which is accompanied by intensive abrasive wear of the tool blades and leads to a sharp decrease in processing efficiency with the appearance of “stagnant” zones on curved sections of the part’s profile with the formation of non-uniform qualitative characteristics along the processed profile that are not allow to achieve stable surface quality. Unequal contact pressures of dense bars along the part profile lead to different metal removal rates and distortion of the profile, especially on protrusions and sections perpendicular to the part axis, which limits the technological capabilities of the method during the finishing of parts, the surfaces of which are subject to stringent requirements for the accuracy of the form.

A distinctive feature of the prototype device is the formation of elastic bars during rotation of the tool, equipped with radial blades in a closed volume of the internal cavity of the workpiece in the absence of circulation of the polishing mixture, and to increase the contact pressure, the tool blades are connected by an elastic partition to form an auxiliary cavity filled, for example, with lead shot. This design solution allows to reduce the frequency of rotation of the tool while maintaining the desired value of the contact pressure. But the abrasive cutting process is accompanied by intense heat generation, which can lead to structural changes in the surface layers of hardened parts or metal burns, and the presence of a radial gap between the tool blades and the machined surface leads to slipping of particles and wear of the blades, and this makes it difficult to obtain a stable quality of the processed surface.

The technical result of the claimed invention is to increase processing productivity and surface quality.

The technical result is achieved by the fact that the radial clearance Δr between the radial blades of the tool and the machined surface is selected from the condition

Δr≤5Z,

where Z is the size of the main fraction of the particles of the processing medium, and the abrasive bars, compacted by the blades of the tool, report axial oscillating movements relative to the treated surface in accordance with the condition

where A and ω _о are the amplitude and circular frequency of the oscillations, respectively;

ω _u is the angular velocity of rotation of the sectional tool;

R is the radius of the workpiece surface;

K is the reliability coefficient;

f is the coefficient of friction of the particles of the processing medium and the surface of the part,

moreover, the processing is carried out in a closed volume of the container, and the walls of the container are cooled by forced circulation of the coolant.

The device for implementing the method is equipped with a tool, the blades of which are made with longitudinal grooves, in which removable linings are fixed in the form of plates with transverse grooves for accommodating fasteners, and the cylindrical shank of the tool is mounted to rotate in the lid hermetically closing the container, while the container is equipped with two cylindrical belts and rigidly connected, for example, by screws, with a female mounting collar, which is mounted by means of a conical shank in the vibrator housing the rotor, and on the cylindrical belts centering the container in the holder, sealing elements are provided, and ring bores are made on the walls of the container and the sleeve to form a sealed torus cavity, which is connected, for example, by fittings, to the forced circulation system of the coolant.

The proposed method and device for its implementation can improve the processing performance and surface quality by preventing slipping of dense bars relative to the blades of the sectional tool and aligning the contact pressure along the processed profile, which optimize the radial clearance between the tool blades and the surface of the part, and axial oscillating movements are reported to the bars, which allows you to remove ring risks and create conditions for uniform removal of metal by processing th contour and for removing heat generated in the closed container volume with vigorous abrasive cutting is carried out forced circulation of the cooling liquid relative to the container walls.

A device for implementing the method allows you to adjust the radial clearance by means of interchangeable pads in the form of plates with transverse grooves mounted in longitudinal grooves made on the blades of the tool, the container with parts mounted in a female clip mounted in the vibrator body, and annular bores on the container walls and clips form a sealed torus cavity connected to the forced circulation system of the coolant, while the replaceable plates on the tool blades are made of resistant polymer material and installed with the ability to control the radial clearance between the tool blades and the workpiece by moving the plates in the transverse grooves relative to the fasteners, such as screws. Such a constructive solution allows to optimize the radial clearance depending on the size and particles of the processing medium, to provide intensive heat removal by cooling the container with the parts and to obtain a stable quality of the treated surfaces of the parts.

A comparison of the known technical solutions with the claimed one showed that the essential distinguishing features of the method are the creation of an optimal radial clearance Δr between the tool blades and the workpiece, the value of which is determined from the condition Δr≤5Z (Z is the particle size of the main fraction of the processing medium), as well as the message to the abrasive bars sealed with tool blades, axial oscillating movements in accordance with the condition

where A and ω _о are the amplitude and circular oscillation frequency, respectively, mm and s ^-1 ;

ω _u is the angular velocity of rotation of the tool, rad / s;

R is the radius of the machined surface of the part (for the profile surface the largest radius), mm;

K is the coefficient of reliability, K = 1 for the initial roughness of the treated surface R _a ≤2.5 μm and K = 1.5 for a rougher roughness;

f is the coefficient of friction of the particles of the processing medium and the surface of the part, while the processing is carried out in a closed volume of the container, and the walls of the container are cooled by forced circulation of the coolant.

The device for implementing the method is also characterized by significant distinguishing features, a set of new functional units and connections, which are the tool, the blades of which are made with longitudinal grooves, in which removable linings are fixed in the form of plates with transverse grooves for accommodating fasteners (this allows you to adjust the radial clearance) and interchangeable pads are made of wear-resistant polymer material, for example polyurethane, while the cylindrical shank of the tool is installed the possibility of rotation in the lid, hermetically closing the container with parts, and for centering in the mounting clip mounted in the vibrator body, the container is equipped with two cylindrical belts and is rigidly connected to the covering mounting clip, and ring bores are made on the walls of the container and the clip to form a sealed torus cavity , which is connected to the system of forced circulation of the coolant (this allows you to report oscillating movements to the abrasive bars relative to the processing washable surfaces of the parts and provide cooling of the container and parts).

No technical solutions with similar distinctive features were found in the patent and scientific and technical literature, therefore, the claimed method and device have significant differences.

Figure 1 shows a schematic structural diagram for implementing the proposed method; figure 2 is a transverse section aa in figure 1 of the container and tool; figure 3 - the blade of the tool with a removable pad; figure 4 is a transverse section bB of the blade in figure 3; figure 5 - the shape of the groove on the installation sleeve (view In figure 1); figure 6 is a bar of abrasive particles, sealed by the blades of the tool.

A device that implements the method consists of a sectional tool 1 (Fig. 1) equipped with blades 2 with overlays 3 (Figs. 2, 3 and 4), fixed with screws 4, machined parts 5 with a profile inner surface installed in the container 6, lids 7, the mounting clip 8, the vibrator 9 and the cartridge 10. The workpiece 5 (rings) are installed in the container 6, the processing medium (water-abrasive suspension) is poured, the section tool 1 is inserted and the container is closed with a lid 7. The assembled container is placed in the installation ymu 8 and is rigidly fixed, for example, screws. The container is centered by cylindrical belts 11 and 12, made on the outer surface of the container 6, and the tightness of the torus cavity 13 is achieved through the use of sealing elements, for example, rubber rings 14 and 15. The tightness of the container is achieved by installing sealing elements (rings) 16, 17 and 18 in the mating of the shank of the sectional tool 1 with the lid 7 and the lid 7 with the inner surface of the container 6. The mounting sleeve 8 by means of a conical shank with a threaded hole is rigidly connected to the vibration torus 9, and the cylindrical shank of the sectional tool 1 is clamped in the cartridge 10 of the drive (not shown).

Installation of interchangeable linings 3 made of wear-resistant polymer material, for example polyurethane, is performed in longitudinal grooves made on the blades 2 (see Fig. 4) of the section tool 1, and the fastening is carried out by screws 4. To adjust the radial clearance, loosen the screws 4 (see figure 3) and move the interchangeable lining 3 in the grooves 19, and then fix them in position with screws 4. To connect the torus cavity 13 (see figure 1) with a coolant circulation system (not shown), fittings 20 and 21 are provided. For easy removal of con teiner 6 in the housing of the mounting sleeve 8 provides a groove 22 (figure 5). The dampers 23 and 24 prevent the collision of the sectional tool 1 with the end wall of the container 6 and the lid 7 during axial oscillations of the container.

The method of centrifugal processing of parts is as follows. The workpieces 5 are installed in the container 6, pour the waterjet suspension of the required concentration, insert the sectional tool 1, close the container with the lid 7 and clamp the package of parts in the axial direction. The assembled container is placed in the mounting clip 8 and rigidly connected to the clip with screws. The mounting sleeve 8 is centered in the vibrator 9 body with a tapered shank and secured with a rod screwed into the threaded hole on the sleeve shank. The cylindrical shank of the sectional tool 1 is clamped in the drive chuck 10 and the tool is informed to rotate with an angular velocity ω _u .

Under the action of the rapidly rotating blades 2 of the sectional tool 1, the abrasive mixture is compressed by centrifugal forces and transformed into dense bars (6), which, rotating together with the blades of the tool, process the surfaces of the parts.

To prevent intensive slipping of abrasive particles relative to the tool blades and to reduce their abrasive wear, the radial clearance Δr between the tool blades and the surface to be machined is chosen from the condition

Δr≤5Z,

where Z is the size of the main fraction of the particles of the processing medium.

To prevent abrasive wear of the blades, smooth cylindrical surfaces are machined without a gap, and with an increase in the radial gap of more than 5Z, particles are not fixed in the gap between the blades and the surface of the part, which leads to intensive slipping of particles relative to the blades, a decrease in the efficiency of metal removal from the treated surface and a catastrophic wear of the blades, which are profiled according to the shape of the parts. To increase the productivity of processing and equalizing the contact pressure along the contour of the profile being machined, the mounting sleeve 8 and the container 6 and parts 5 rigidly connected to it, axial oscillating movements are reported relative to the abrasive bars sealed by inertial forces. The elasticity of the compacted abrasive bars avoids the breakdown of the profile, leads to a more uniform removal of metal from the shaped surface and creates favorable conditions for processing hard-to-reach sections of the profile. The drive oscillatory movements of the vibrator 9 include after the rotation of the sectional tool 1 from the cartridge 10 with a shutter speed of 5 ... 10 seconds, necessary for the formation of dense bars by the tool blades. Thus, in the process of processing, conditions are created that are similar to honing the inner surface with elastic abrasive bars - “hons”.

To ensure effective axial movement of the entire set of particles sealed by the tool blades into bars, it is necessary to choose the oscillation parameters from the condition

where A and ω _о are the amplitude and circular oscillation frequency, respectively, mm and s ^-1 ;

ω _u is the angular velocity of rotation of the tool, rad / s;

R is the radius of the machined surface of the part (for the profile surface the largest radius), mm;

K is the coefficient of reliability, K = 1 for the initial roughness of the treated surface R _a ≤2.5 μm and K = 1.5 for a rougher roughness;

f is the coefficient of friction of the particles of the processing medium and the surface of the part.

When this condition is met, the inertia forces from the oscillating movements of the part are sufficient to create the axial momentum necessary for the displacement of the particles of the solid fraction pressed by centrifugal forces along the generatrix surface. The value of the coefficient of reliability K is recommended to be taken equal to unity for the initial roughness of the treated surface R _a ≤2.5 μm and K = 1.5 for a rougher roughness.

To remove heat that occurs during abrasive cutting in a closed container volume, simultaneously with the rotation of the tool, a cooling fluid is supplied under pressure into the torus cavity surrounding the container, and it is forced to circulate, which reduces the temperature in the container and ensures a stable surface quality of the workpieces.

A device for implementing the method works as follows. On a sectional tool 1 (see Figs. 1–4), lining 3 of polymer material is installed in the longitudinal grooves of the blades 2 and, by moving the lining in the transverse grooves 19, the required radial clearance Δr is set, and the lining is fixed with screws 4. The workpieces 5 are installed in the container 6, forming an axially rigid package. Then the processing medium is poured and the sectional tool 1 is inserted. The container is hermetically sealed with a cover 7. The coupling of the cylindrical shank of the sectional tool 1 with the cover 7 provides centering of the tool in the container, and the sealing elements (rings) 16, 17 and 18 create a tightness of the working cavity of the container. The mounting sleeve 8 with a tapered shank is centered in the body of the vibrator 9 and is rigidly fixed by means of a rod screwed into the threaded hole at the end of the shank. The container 6 assembly with the help of the centering belts 11 and 12 is installed in the sleeve 8 and connected to it by means of screws rigidly fixing the flanges of the cover 7 and the holder 8 and the package of parts 5 in the axial direction. The cylindrical shank of the tool is clamped by the chuck 10 of the drive. The torus cavity 13 through the fittings 20 and 21 is connected to the forced circulation system of the coolant. Sealing elements 14 and 15 is achieved by sealing the torus cavity 13.

The drive is turned on and through the cartridge 10, rotation with an angular velocity ω _u is transmitted to the tool. The blades 2 during rotation of the sectional tool 1 compacts the solid fraction of the suspension to form dense bars (see Fig.6), which copy the profile of the machined surfaces of the parts. Simultaneously with the drive rotation of the tool in the torus cavity 13 is supplied under pressure coolant to remove heat from the walls of the container and to cool parts.

With a shutter speed of 5 ... 10 seconds, the oscillator moves the drive of the vibrator 9. The vibrations from the mounting sleeve 8 and the container 6 are transmitted to the parts 5. The dampers 23 and 24 are designed to prevent collision of the section tool 1 with the container 6 and the cover 7 when setting the vibrator.

At the end of the processing time determined by the state of the initial surface, the tool rotates the drive by means of a time relay. At the same time, the vibrator drive 9 and the coolant circulation pump are switched off. The cams of the cartridge 10 and the screws connecting the flanges of the cover 7 and the cage are unfastened. Using a puller through the groove 22, the container 6 is moved to the left and removed from the cage 8. The cover 7 is removed with the section tool 1, the suspension is poured into the tank, the container is rinsed, and the processed parts are removed 5. A new batch of parts is installed, and the processing cycle is repeated as described above.

EXAMPLE

Processing exposed hardened to a hardness of 60 ... 62 LDCs _E spinning ring with a profiled inner surface (the largest radius of the inner surface of R = 23 mm, the ring height h = 10 mm, the material - stal45 after carbonitriding and quenching), and the sleeve of the brake cylinders (stal45, quenching to hardness 41 ... 46 HRC _E ), inner radius of the smooth cylindrical surface of the sleeve R = 33.75 mm, height of the sleeve h = 218 mm). The initial surface roughness R _a = 2.5 μm.

As a grinding material, we used a water-abrasive slurry of white alumina grade 25A of grit 80 with a concentration of abrasive in liquid 2: 1.

Technological processing modes:

- the angular velocity of rotation of the tool ω _u = 100 rad / s;

- circular oscillation frequency ω _o = 251.2 s ^-1 ;

- oscillation frequency ν = ω _o / 2π = 40 Hz;

- the amplitude of the oscillations A = 1.5 mm;

- radial clearance between the tool blades and the machined surface - Δr = 1.5 mm - for spinning rings;

- for smooth surfaces of liners of brake cylinders, processing is performed without a gap between the radial impeller blades and the liner;

- main (machine) processing time t = 120 s.

The friction coefficient of abrasive particles on the metal f = 0.25; reliability coefficient (at R _a ≤2.5 microns) K = 1.

The roughness of the working surface of the spinning rings after processing was R _a = 0.16 ... 0.18 μm, and the liners of the brake cylinders R _a = 0.18 ... 0.2 μm.

Compared with the prototype, the machine processing time is reduced by 1.5 ... 2 times, a uniform surface roughness along the part profile is achieved, manual labor is excluded on the polishing of hard-to-reach sections of the ring profile.

The wear resistance of the tool blades when using pads made of polyurethane increased up to 20 times compared with hardened steel blades.

When the radial clearance increases to Δr = 2.25 mm, unpolished sections appear on the contoured surface of the spinning rings, which requires manual polishing of the rings.

Claims (5)

1. The method of centrifugal processing of parts, including the installation of parts in a container, the supply of the processing medium and its compaction with a sectional tool with radial blades until abrasive bars are formed inside the surface to be machined, characterized in that they set a radial clearance Δr between the radial blades of the sectional tool and the surface being machined, the value which is selected from the condition:
Δr <5Z,
where Z is the size of the main fraction of the particles of the processing medium. 2. The method according to claim 1, characterized in that the abrasive bars, sealed with radial blades of the sectional tool, report axial oscillating movements relative to the machined surface in accordance with the condition:

where A and ω ₀ are the amplitude and circular oscillation frequency, respectively, mm and s ^-1 ;
ω _and - the angular velocity of rotation of the tool, rad / s;
R is the radius of the surface of the workpiece, and for the profile surface is the largest radius, mm;
K is the coefficient of reliability, K = 1 for the initial roughness of the treated surface R _a ≤2.5 μm and K = 1.5 for a rougher roughness;
f - coefficient of friction of the particles of the processing medium and the surface of the part. 3. The method according to claim 1 or 2, characterized in that the treatment is carried out in a closed volume of the container, the walls of which are cooled by forced circulation of the liquid. 4. A device for centrifugal processing of parts, containing a container with parts filled with a processing medium, and a sectional tool with radial blades mounted with a gap relative to the surface to be machined, characterized in that the tool blades are made with longitudinal grooves in which replaceable plates in the form of plates are fixed with transverse grooves for accommodating fasteners, and the cylindrical shank of the tool is mounted to rotate in the lid, hermetically closing the container, with this container is made with two cylindrical belts and is rigidly connected, for example, by screws with a female mounting sleeve that is mounted by means of a conical shank in the vibrator body, and sealing elements are provided on the cylindrical belts centering the container in the holder, and annular rings are made on the walls of the container and holder boring with the formation of a sealed torus cavity, which is connected, for example, by fittings with a system of forced circulation of the coolant. 5. The device according to claim 4, characterized in that the replaceable pads in the longitudinal grooves of the blades are mounted with the possibility of adjusting the radial clearance between the tool blades and the workpiece surface by moving the pads in the transverse grooves relative to the fasteners, for example screws, and the replaceable pads are made of wear-resistant polymer material, such as polyurethane.

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