RU2279330C2 - Method for working large-diameter openings in elongated cylindrical articles - Google Patents

Abstract

FIELD: mechanic working systems, working of accurate- size openings in screw-cutting lathes with elongated housing.

SUBSTANCE: method comprises steps of mounting and securing article to lathe for further working of opening by means of tool head mounted on end of stem at relative rotation and axial feed of article and tool and at withdrawing cuttings out of working zone. In order to enlarge manufacturing possibilities and to improve quality of worked surface, at mounted article guiding rod is inserted to worked opening. Said rod is centered and fixed. Before working axial tension effort is applied to said rod and said effort is kept for whole period of working opening. Opening is worked at rotation of article and at axial motion of stem with tool head by sliding fit along positively extended guiding rod. The last may be one-piece rod or built-up one. It is possible to work opening by turning, honing or burnishing.

EFFECT: enlarged manufacturing possibilities of method, improved quality of worked surface.

6 cl, 4 dwg, 1 ex

Description

The present invention relates to the field of mechanical processing and can be used on screw-cutting lathes with an elongated bed to obtain precise holes of large (over 80-100 mm) diameters in long-length (more than 2000 mm) cylindrical workpieces, for example, in hydraulic lock cylinders.

Known widely used in production is the method of processing these holes, described in the "Handbook of a manufacturing engineer", ed. A.G. Kosilova and R.K. Meshcheryakova. - M .: Mechanical Engineering, 1973, p. 249. The method consists in sequentially, from two sides, boring a part with its revolution on a horizontal boring machine with a mandrel without additional support for the spindle. Moreover, the boring length L on each side should not exceed 5d, where d is the diameter of the boring hole. With an increase in the boring length L> 5d, boring is used with boring bars with supports in the spindle and the backrest of the back support or in two backrests located in front and behind the workpiece. In the latter case, due to the hinged connection of the boring bar with the spindle, the influence of inaccuracy of the machines on the accuracy of processing is eliminated. The straightness of the axis of the bored hole is ensured by the alignment of the lunette bushings and the straightness of the boring bar.

There are also known methods of deep boring in compression and in tension, described in the book "Processing of deep holes", ed. N.F. Utkina, L. "Mechanical Engineering", 1988, p.28. When implementing these methods, the workpiece rotates, and the tool has a translational movement, while the axial component of the cutting force P _x creates in the stem, depending on the scheme of boring, compressive or tensile stresses.

However, a number of disadvantages do not always allow the efficient use of the described technological solutions when boring holes in long parts. In particular, when the length of the hole being machined increases to 4000 mm or more, the influence of such destabilizing factors as the longitudinal instability (nonrigidity) of the stem, the error in the direction of the tool, the imperfection of its design, irrational technology, etc., which sharply increasing the magnitude of the displacement of the axis of the hole, virtually exclude the possibility of processing it in such ways. It is necessary to exclude these factors as much as possible or to take into account their influence by a deliberate change in the position of the axis of the hole being machined during boring in accordance with a certain predetermined law, i.e. produce controlled deep boring.

So, there are known methods of processing deep holes on horizontal boring machines with active monitoring of the position of the cutting tool as a function of deviating the axis of the bored hole from the axis of rotation of the machine spindle and compensating it during processing (see "Progressive technology for processing deep holes". reports edited by N.F. Utkin, M., 1978, p. 185-187). To monitor the position of the tool, it was proposed to equip the machines with adaptive control systems (ACS), in particular, containing various sensors as sensitive elements associated with actuators, for example, electro-hydraulic, as well as multi-parameter tracking systems with N inputs.

The disadvantages of the known methods of processing deep holes on horizontal boring machines are:

- monitoring the position of the tool with the help of an automatic control system does not guarantee the stability of the axis offset at certain boundaries, which does not allow them to be used for boring holes with a narrow tolerance field, i.e. exact, for example, according to the 2nd class, holes;

- the creation of a multi-parameter tracking system is almost impossible due to the lack of sufficient information about the influence of individual destabilizing factors on the accuracy of processing;

- the complexity and comparative cost of tracking systems;

- the absence of such systems in the reviewed sources for considered in this application deep holes of large diameters.

A known method of boring the central hole in the turbine rotors with a tool with a correction mechanism based on an eccentric element with a step drive, described in the book. "A new highly effective cutting tool and tool-means of intensification of machine-building production", L., LDNTP, 1989, p.8. When the specified permissible displacement of the axis of the hole is reached, the rotation drive of the eccentric element is activated by a command from the control unit, due to which oscillations of the correcting cutter are created at the frequency of rotation of the part in antiphase with beats of the displaced hole. As a result of the separation of the metal by the corrective cutter, a forced cyclic displacement of the axis of the hole is carried out until it coincides with the geometric axis of the part, after which the correction mechanism is disabled.

However, the boring head used in the known method, operating in an environment of cutting fluid (coolant) and a large volume of chips, will quickly fail, which makes the method inoperative.

There is also a known method of processing, in particular boring on horizontal single spindle deep drilling machines, described in the book "Processing of deep holes", ed. N.F. Utkina, L .: Engineering, 1988, p. 91. To implement the known method, a lathe is used, in the spindle chuck of which the workpiece is fixed and rotated. The right end of the workpiece is based in the oil receiver, and the middle part is based on intermediate lunettes. The tool, fixed in the tool head, at the beginning of processing is guided by the conductor sleeve of the oil receiver. As the tool feeds, the resulting chip from the cutting zone enters through the tool stem into the chip collector. Coolant supply to the cutting zone - external, through the oil receiver.

The disadvantages of this method include the characteristic defects of the holes that appear during deep drilling or boring, the main of which are:

- withdrawal and axial linearity;

- cut;

- nadir, scratches, increased roughness.

The main causes of withdrawal include:

- copying with the tool the error of the location of the axis of the hole, available at the point of contact of the guides with the surface of the bored hole;

- the bend of the stem due to transverse vibrations of the tool with the speed of rotation of the workpiece, resulting from the basing of the tool on the surface of the hole having a radial runout, and due to the different machinability of the material over the cross section of the workpiece, as well as the unevenness of the removed allowance;

- transverse vibrations of the workpiece due to its deformation during installation and processing;

- bending of the mandrel under the action of the force of its weight.

The withdrawal may weaken or increase depending on the specific processing conditions, namely, on:

- construction of the technological process;

- processing lengths;

- bending stiffness of the stem;

- errors of sharpening and installation of cutting blades along the axis and others.

The cut is formed only with transverse vibrations of the tool with a frequency close to the frequency of the relative rotation of the workpiece. At the same time, the formation of a facet is affected by the frequency of natural vibrations of the tool, which, in turn, changes as the hole is machined, since the fixation pattern of the tool changes (the relative position of the supports along the length of the tool changes); design parameters of the tool; errors in setting up the technological system for the operation; kinematic processing scheme (the tool rotates or does not rotate) and others.

Nadira, scratches often occur due to chips falling under the guide elements, as well as when the coolant film ruptures under the guides.

Closest to the claimed technical essence and the achieved effect, i.e. the prototype is a method of boring holes, carried out on a boring machine described in ed. St. USSR No. 1748967, IPC ⁵ V 23 V 41/00, 1989. According to the description, the workpiece is installed and clamped on the table of the machine. Then, a hole is bored, while the part has translational movement with the table, and the tool head, mounted on the end of the stem, rotates. To increase rigidity and thereby the accuracy of processing, a compression force is applied to the tool stem during boring. Chip formed during hole processing is diverted.

However, the known prototype method is intended, as a rule, for processing holes in products whose length is less than or equal to its five diameters, and cannot be used for boring long parts for the following reasons. Thus, an increase in the rigidity of the boring bar due to the application of compression forces to it when machining long holes can lead to longitudinal bending of the boring bar and a violation of the accuracy of the machined hole. In addition, when boring a long part, the rod compressing the boring bar may lose longitudinal stability, while the compressive pressure on the boring bar will be directed at an angle to its axis, which will practically exclude the possibility of processing such products. In the processing scheme used in the known method: the tool rotates, and the part has a translational motion, the rotating tool is a source of additional errors, in particular, more favorable conditions are created for the formation of faceting.

When creating the present invention, the task was to eliminate or minimize the above disadvantages, namely: expanding the technological capabilities of the hole processing method by increasing its diameter and length, as well as improving the quality of processing by achieving the required accuracy and surface roughness of the hole.

The problem is achieved in that in the method of processing holes of large diameters in long cylindrical products, including installing and securing the product in the machine, followed by machining the hole with a tool head mounted on the end of the stem, with relative rotation and axial feeding of the product and tool and removal of chips from the zone processing, according to the claimed invention, after installing the product in the hole to be machined, a guide rod is inserted, which is centered and fixed, and before processing a tensile force is applied to it in the axial direction, which is maintained throughout the entire hole processing process, and hole processing is carried out during rotation of the product and axial movement of the stem with the tool head to slide along a forcibly extended guide rod.

Other differences of the present invention are that for the processing of holes using a guide rod, made either as a single unit, or detachable, consisting of two parts.

In addition, the differences of the proposed method is that the processing of the holes is carried out either by boring, or honing, or rolling.

Comparative analysis with the prototype shows that the inventive method is characterized by the presence of new actions, the sequence and conditions for their implementation.

A search conducted by the St. Petersburg Territorial Patent Fund showed that at present there is no known method for processing large-diameter holes in long cylindrical products, which has the same set of essential features as the proposed one. This allows us to conclude that the claimed method meets the criteria of the invention of "novelty."

When studying the level of technology known in this field, the features that distinguish the claimed invention from the prototype were not identified and therefore they provide the claimed technical solution with the criterion of "inventive step".

Using for processing (boring, honing, rolling) the holes of the guide rod, passed through the workpiece and the tool stem and under the action of tensile stress, allows you to maintain a strictly rectilinear movement of the enclosing stem with the tool head during the entire processing of the hole, significantly reducing errors in the location of its axis along product length; reduce transverse vibrations of the tool and the workpiece, eliminate the bending of the stem under the action of weight. These factors, with the correct construction of the technological process, sharpening and installation of the cutting tool, will significantly reduce the withdrawal and indirectness of the axis of the bored hole. These same factors reduce the frequency of natural vibrations of the tool and save it along the entire length of the hole being machined, which reduces or completely eliminates the formation of cuts. Using in the inventive method of processing a tool with certainty of basing on the machined hole allows you to set the cutting edge of the cutter and the guides at an angle to the horizon, which will reduce the ingress of chips under the guides and, as a result, improve the surface cleanliness. If the length of the machine bed allows you to accommodate the double length of the workpiece and the stem with the tool head, then the guide rod can be integral and after processing is removed to the right from the workpiece, ensuring its removal from the machine, otherwise the guide rod is detachable.

The above proves that the claimed technical solution can be widely used in technology for processing deep holes of large diameters and lengths with high surface quality, in particular for boring holes with a diameter of 80-100 mm or more in long (more than 2000 mm) cylindrical workpieces, t .e. it meets the criteria of the invention of "industrial applicability".

The proposed processing method is schematically illustrated by the drawing, where Figs. 1-4 show parts of a single circuit of a machine designed for its implementation.

Consider the implementation of the method on a specific example, when the hole is machined by boring on a screw-cutting machine. This example does not limit all the possibilities of the proposed method.

The machine for carrying out the method comprises a bed 1, supporting lunches 2 installed on it and a support 3 with a stem 4 and a boring head 5 fixed thereon. A detachable guide cylindrical rod 7 having a right passes through the spindle of the headstock 6 of the machine, the boring head 5 and stem 4 8 and the left 9 parts. The left 9 part of the rod 7 is centered by bushings 10, 11, mounted on the front headstock coaxially with the axis of the machine spindle, and supporting struts 12. On the lower part of the rod 7, the teeth forming the gear rack 13 are cut. Due to the gear transmission 14, the rod 7 has the possibility of horizontal movement : mechanical - from the gearbox 15 and manual - from the helm 16. This movement is limited by limit switch 17 to the left and bypass limit switch 18 - to the right. In the right end position (working), the left 9 part of the rod 7 is fixed with a special lock 19, which is extended from the hydraulic cylinder 20. The latch limits both horizontal movement of the rod 7 and prevents it from turning when making and unscrewing from the right 8 part. The gearing 14 of the rod - the gear of the gearbox is fixed with a key that slides along the longitudinal groove of the rod 21 when moving it.

The right 8 part of the rod 7 is centered by the fastening mechanism 22 on the machine support and the supporting column 23. This part of the rod rotates from the helm 24, while both parts of the rod 7 are screwed up. The connector location in figure 2 is indicated by 25. The screwing is performed using a rectangular double thread, the length of which is calculated in such a way as to ensure the strength of the rod when it is stretched. The tension of the rod 7 is produced from the hydraulic cylinder 26, placed on the rack 27 (figure 4). The grooves 28 are made along the entire length on the stem body in the horizontal plane, along which the grips 29 of the stem supporting the stalk 30 are moved during the working movement of the caliper. On the body of the stem 4, a groove is milled to accommodate the tube 31 for supplying cooling and leaching chips from the cutting zone. The stem 4 with the boring head 5 is moved by inserts 32 along the guide rod 7 along the sliding fit.

The inventive method is as follows.

In the initial state, the tensile stress from the guide rod 7 is removed and it is unscrewed by the helm 24. The left 9 part of the rod with the help of the gearbox 15 is taken to the leftmost position until it stops in the limit switch 17.

On the lunettes 2 of the machine, a workpiece 34 of steel 45 with a length of 2000 mm and a hole with a diameter of 120 mm is mounted and fixed in the cartridge 33. Leave the left 9 part of the rod 7 into the hole of the part as far as it will go into the bypass limit switch 18, while its departure beyond the end of the part will be at least 100-150 mm. Summarize the right 8 part of the rod and manually control the rod 24 of the hydraulic cylinder 26 and both parts of the rod are connected into a single unit. In the hydraulic cylinder 26 include pressure, thereby providing its tension with an applied force of 22-25 kgf / mm ² , while the rod 7 becomes an internal guide to ensure the cutting process. The cutter of the boring head is finally adjusted to the required size. The support of the machine boring head is brought to the end of the workpiece, while the limit switch 18 is retracted. Turn on the rotation of the part, the supply of coolant and tool and produce boring holes. At the end of the treatment, the caliper is returned to its original position.

Next, replace the rough boring head with a fine one or install another processing tool according to the manufacturing process and repeat the processing cycle. After finishing the hydraulic cylinder 26 is removed from the guide rod 7 tensile stress. Use the steering wheel 24 to unscrew the left and right parts of the rod, move the left part to its original position and remove the part.

When implementing the proposed method, the processing of the holes can be performed by honing or rolling.

At a certain length of the machine bed, which allows you to place the double length of the workpiece and the stem with the tool head and to complete the withdrawal of the rod from the hole of the workpiece, the rod 7 can be one-piece.

Claims (6)

1. The method of processing holes of large diameters in long cylindrical products, including installing and securing the product in the machine, followed by machining the hole with a tool head mounted on the end of the stem, with relative rotation and axial feeding of the product and tool and removal of chips from the processing zone, characterized in that after installing the product in the hole being machined, a guide rod is inserted, which is centered and fixed, and before processing, an axial force is applied to it yazheniya which was maintained throughout the hole processing, the hole treatment is performed when the article is rotating and axially moving the stem with the tool head on sliding fit on the guide rail forcibly stretched. 2. The method according to claim 1, characterized in that for the processing of the holes using a guide rod made in a single unit. 3. The method according to claim 1, characterized in that for processing the holes using a guide rod made detachable. 4. The method according to claim 1, characterized in that the processing of the holes is carried out by boring. 5. The method according to claim 1, characterized in that the processing of the holes is carried out by honing. 6. The method according to claim 1, characterized in that the processing of the holes is carried out by rolling.

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