RU2270747C1 - Cone opening honing method - Google Patents

Abstract

FIELD: machine engineering, possibly finish operations of grinding and honing cone surfaces of parts of hard-to-form materials having trend for occurring burnings and micro-cracking.

SUBSTANCE: method comprises steps of imparting rotation and reciprocation feed motion to blank and to honing head while using honing head with body in the form of elastic tore-like envelope and hollow spindle with central lengthwise opening for supplying compressed air to body. Diamond-abrasive beams with flexible binder are secured to flexible base and are arranged along periphery of wheel. Head is provided with mechanism for controlling inclination angle of body relative to plane normal to lengthwise rotation axis. Said mechanism consists of two washers jointly coupled one to other; one washer is rigidly secured to spindle and other is secured to end of body. Helical cylindrical compression spring is arranged between washers in place diametrically opposite relative to said articulation joint. On end of body opposite relative to said mechanism spherical and conical mutually adjoined washers are mounted. Rough working is realized at minimum inclination angle of body and finish working is realized at maximum inclination angle of body. Invention provides controlled distribution of specific pressure acting upon worked surface without preliminary adjustment according to conicity degree.

EFFECT: enhanced accuracy and efficiency of working, lowered thermal stresses due to using head with intermittent and oscillating cutting layer.

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Description

The invention relates to mechanical engineering for metalworking, and in particular to methods for finishing abrasive-diamond processing and can be used in finishing operations by grinding and honing conical surfaces from hard-to-work materials that are prone to burns and microcracks.

A known method of honing conical surfaces with a honing head containing a housing in which the upper and lower cones are mounted with the possibility of contact with blocks carrying abrasive blocks and a rod for radial movement of the cones, and it is equipped with an additional spring-loaded rod installed inside the main rod for radial movement of the blocks, on which the lower cone is mounted, located towards the upper [1].

The disadvantages of the known method and the head are: complicated removal of sludge from the treatment zone, there is a tendency to grease the bars and to reduce their cutting properties due to the fact that when honing conical surfaces using the head, the abrasive bars are constantly in contact with the treated surface.

In addition, due to the difficult penetration of the coolant into the treatment zone, the temperature in it rises, which reduces the quality of the surface layer, while the complicated drive requires significant costs for the modernization of honing equipment, which allows to drive an additional rod inside the main rod, and this increases the cost of manufacturing, reduces productivity and processing quality.

There is a method of honing conical surfaces with a honing head containing a housing, which at the same time is also the housing of pneumatic cylinders, on which holders with bars are mounted by means of rods, axles and flat springs [2].

In the axial plane, the profile of the working surface of the bars is an arc of a circle. The radial movement of the bars is provided by pistons located in the chamber of the pneumatic cylinder.

Each holder can freely rotate on an axis in the axial plane of the head. To press the bars to the workpiece surface, compressed air is supplied into the chamber through the nozzle and the channel in the housing. To remove the bars, air is supplied to the rod cavities through the nozzle and channels.

Before processing, the head is set so that the axis of symmetry of the bars coincides with the middle of the length of the profile of the surface to be treated.

A significant drawback of the known method and the head is the unevenness of the removed allowance in cross sections with the minimum and maximum diameter of the workpiece, because with a longitudinal oscillating feed of the head with amplitude A when moving from a larger internal diameter to a smaller one, the pistons approach the longitudinal axis, which causes an increase in the pressure air in the chambers, and therefore, an increase in the radial force acting on the abrasive bars.

This causes a deviation from a given slope and a deviation of the shape of a given profile of the conical inner surface, which leads to marriage, reduces productivity and processing quality.

Another disadvantage is the complicated design of the Hong-head and large overall dimensions, which require significant costs for the manufacture of tools and the modernization of honing equipment, which allows to drive the Hong-head, and this increases the cost of manufacturing workpieces.

The objective of the invention is to increase the accuracy and productivity of processing by ensuring the regulation of the distribution of specific pressure on the surface without pre-setting the taper, as well as increasing the cutting conditions and reducing heat stress of the process through the use of a tool with an oscillating and intermittent cutting layer, which facilitates the removal of sludge from the zone processing, promotes self-sharpening and improving cutting properties, as well as free penetration of coolant in processing zone and lowering the temperature in it, which increases the quality of the surface layer.

The tasks are solved using the proposed method of honing conical holes, including the message of rotational movements and reciprocating motion of the feed along the longitudinal axis of the workpiece surface of the workpiece and the honing head containing a spindle and a housing carrying diamond abrasive bars, using a honing head having a housing in in the form of an elastic shell in the form of a torus, into which compressed air is fed through the central longitudinal hole of the spindle, the angle control mechanism and the inclination of the housing to a plane perpendicular to the longitudinal axis of rotation, consisting of two washers pivotally connected to each other, one of which is rigidly mounted on the spindle, and the other on the end of the housing, and a helical compression coil spring located between the washers in a diametrically opposite place from the hinge, as well as spherical and conical washers, mating with each other and installed from the opposite angle control mechanism of the end face of the body, while using diamond-abrasive bars on a flexible bond ennye in a flexible manner and arranged on the periphery of the housing and the roughing process is performed with a minimum angle of inclination of the housing, and finishing - with maximum.

Features of the proposed method are illustrated by drawings. Figure 1 shows a diagram of the finishing of a conical hole with a honing head with a maximum angle of inclination, a partial longitudinal section; figure 2 - head, left view of figure 1; figure 3 - scheme of roughing a conical hole with a honing head with a minimum angle of inclination, a partial longitudinal section; figure 4 is a transverse section bB in figure 3.

The proposed method of honing conical holes is carried out by a special honing head, rotational movements are reported to the workpiece, and rotational and reciprocating feed movements along the longitudinal axis of the machined surface are reported to the head.

The honing head that implements the proposed method comprises a spindle 1 on which a body 2 is mounted, carrying diamond abrasive bars 3. The hollow spindle 1 has a central longitudinal hole 4, through which a compressed one is supplied into the body 2, made in the form of an elastic shell in the shape of a torus air pressure P variable _{compression channel.}

The head is equipped with a mechanism for adjusting the angle of the axis of inclination of the housing to a plane perpendicular to the longitudinal axis of rotation. The mechanism consists of two washers 5 and 6, while one washer 5 is rigidly fixed to the spindle 1, and the other washer 6 is rigidly fixed to the end of the housing 2. The washers 5 and 6 are pivotally connected to each other, for example, using a loop with an axis 7 and equipped with a coil spring compression 8 located between the washers 5 and 6 in a diametrically opposite place from the hinge 7.

The head is equipped with spherical 9 and conical 10 washers, mating with each other and installed from the opposite end angle control mechanism of the housing 2. These washers are made according to GOST 13438-68 and 13439-68.

Diamond-abrasive bars 3 are used on a flexible bond, located on the periphery of the housing 2 and are fixed on a flexible base 11, for example on a fabric. To reduce the cost of manufacturing tools as a diamond-abrasive whetstones 3 used waterproof sandpaper on a fabric basis (GOST 13344-79). The material of abrasive grains of skins are normal electrocorundum grades 13A, 14A, 15A or white electrocorundum 23A, 24A, 25A or others, as well as natural or artificial diamonds.

The fastening of the diamond-abrasive bars 3 on the housing 2, which is a flexible pneumatic shell, is carried out by gluing, vulcanization or other known methods.

Actuation of head operating state is performed by supplying pressurized P _{compression channel} compressed air to the elastic shell of the housing 2 through 4, an axial and a transverse bore 12 in the spindle 1.

The high pressure compressed air _{compression channel} P is supplied to the elastic shell of the housing 2, the more compressed the spring 8, the smaller the angle α of inclination is set housing to the plane perpendicular to the longitudinal axis of rotation.

It becomes possible to automatically control the amplitude A _{of the} oscillation of the cutting layer by changing the pressure of the supplied compressed air, thereby controlling the heat intensity of the honing process.

Processing conical holes according to the proposed method is as follows.

Roughing is carried out with a minimum angle of inclination of the body to a plane perpendicular to the longitudinal axis of rotation, with a maximum pressure of compressed air supplied to the elastic shell of the body, and finishing is carried out with a maximum angle of inclination of the body with a minimum pressure of compressed air.

In the idle state without compressed air in the elastic shell, the outer diameter of the body along the diamond-abrasive bars is less than the inner diameter of the hole being machined, so the head is freely inserted into the billet hole.

The head is attached rigidly to the machine spindle, the workpiece, for example, the outer ring of the bearing, lies on the hard bearings 13 and 14 (shoes) and is pressed with a flat polished end to the rotating electromagnetic cartridge 15 on the headstock spindle, due to which the workpiece receives a rotational movement V _s .

Precise self-centering of the head bars is ensured by the elastic shell of the housing.

Mounting the workpiece on the spindle of the machine can be using other known devices.

The head rotates at a speed of V _and , the reciprocating motion of the longitudinal feed S _pr , and the radial feed S _{p of} diamond-abrasive bars is carried out by supplying compressed air to the elastic shell of the housing, expanding the bars.

Thus, honing occurs with the oscillation of honing bars, which significantly improves the quality of the processed surface and increases several times the productivity.

Oscillations of the bars in combination with the rotational and reciprocating movements of the honing head create a cross movement of the abrasive grains and periodically change the cutting direction and friction force, forcing the abrasive grains of the bars to cut not by one face, as in traditional honing, but by several faces.

Thanks to this, material removal and chip formation are facilitated, grain self-sharpening is improved, and variable forces are actively redistributed in the cutting plane and the friction force is reduced several times.

Cross oscillating movement increases the number of actively working abrasive grains and intensifies the cutting of protrusions of surface irregularities.

At the same time, a wear-resistant regular microrelief is formed on the treated surface with the cross direction of the marks and roughnesses of small and uniform height.

The advantages of the proposed method for diamond-abrasive honing of conical holes: more smooth processing; greater rigidity of the technological system; the quality and accuracy of processing are increased, technological capabilities are expanded and it becomes possible to process both conical and cylindrical, as well as shaped openings; the possibility of removing large uneven allowances; processing productivity is increased by a factor of 2–3 due to the large contact area of the tool with the workpiece and the reduction in the number of passes when switching to oscillating honing mode. Quickly setting the optimum angle of inclination of the case and changing its value depending on specific conditions also helps to increase productivity.

Due to the use of an elastic shell and uniform distribution of compressed air pressure on all the bars, regardless of the random different thickness of the diamond-abrasive layer on the bars and other errors in the manufacture and assembly of the head, the bars evenly distribute the removed allowance.

Example. A through conical bore of the outer ring of the bearing 27310N GOST 7260-70 ⌀110 × ⌀50 × 29.25 mm was processed on an internal grinding machine mod. 3K228V. The workpiece material is steel ШХ15, hardened, hardness HRC 45. The method of fastening the workpiece is in the cartridge. The technological system machine - tool - tool - workpiece is quite rigid.

The roughness parameter of the treated surface is Ra 0.32 μm. The head is made ⌀ 80 mm high 30 mm on an elastic basis, the bars of the skin with grain size on one side 14A4. The allowance is 0.05 mm, the head rotation frequency is 13,000 min ^-1 (V _c = 34 m / s), the workpiece rotation frequency is 191 min ^-1 (V _c = 0.5 m / s), the longitudinal feed is S _pr = 0.05 m / s. Coolant - 5% aqueous solution of emulsol in water.

To obtain the necessary accuracy and roughness, it took half the time than with traditional processing.

The method improves productivity and quality of processing, simplifies and reduces the cost of tool design, extends technological capabilities and allows you to process non-circular holes.

Information sources

1. A.S. 1174238 USSR, MKI V 24 V 33/02. Honing head. 1985.

2. Patent 2074082 of the Russian Federation, MKI 6 V 24 V 33/08. Honing head for machining conical surfaces. 1995 - prototype.

Claims (1)

A method for honing conical holes, including communicating rotational and reciprocating feed along a longitudinal axis of the workpiece surface with a workpiece and a honing head containing a spindle and a housing carrying diamond abrasive bars, characterized in that they use a honing head having an elastic shell body in the form of a torus, into which compressed air is fed through the central longitudinal hole of the spindle, a mechanism for adjusting the angle of inclination of the housing to the plane, perpendicular a bright longitudinal axis of rotation, consisting of two washers pivotally connected to each other, one of which is rigidly fixed to the spindle, and the other on the end of the casing, and a coil compression spring located between the washers in a diametrically opposite place from the hinge, as well as a spherical and conical washers, mating with each other and installed from the opposite end face angle control mechanism, using diamond abrasive bars on a flexible bond, mounted on a flexible base and located on eriferii housing, and roughing is performed with a minimum angle of inclination of the housing, and finishing - with maximum.

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