RU2586185C1 - Method of processing tooth profile of splined broaches - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: method consists in grinding teeth profile drawing in two stages. At first stage profile of rough and transition teeth is ground to passage with reverse taper. At second stage profile of finishing and gaging teeth is polished with zero reverse taper. Grinding is made by radial sections at top of grinding wheel profile at matched drawing continuous rotation and vertical movement of grinding wheel, circular section centre coordinate of which is connected with turning angle of drawing by given system of equations.

EFFECT: higher quality of treatment due to making of cutting teeth with shaped cutting arrangement.

1 cl, 1 tbl, 7 dwg

Description

The invention relates to metalworking and can be used in tool production, namely in the manufacture of slotted broaches.

A known method of processing the profile of the broach, including installing the broach broach in the center of the dividing head or dividing headstock of the grinding machine, raising the rear center relative to the front and grinding the profile of the teeth of the broach to the passage with a shaped grinding wheel (Broaches for machining holes / D.K. Margulis, M.M. Tverskoy, V.N. Ashikhmin and others .-- M .: Mechanical Engineering, 1986. - S. 190-191).

This method is implemented on universal slot grinding machines (for example 3451A, 3451B, etc.) and allows you to get a broach that works according to the generator cutting scheme, in which each tooth forms a small portion of the side surface of the profile of the extended workpiece.

The disadvantages of the method include significant errors in the circumferential pitch due to deviations from the alignment of the spindle of the dividing head and broaches that occur when the rear center is very high. This drawback can be eliminated by applying a laid table, by turning which the rear center is lifted. Another significant drawback of the method is the narrow technological capabilities that limit its use only for the manufacture of generator broaches, providing low purity of the extended profile, the presence of steps and low resistance associated with intensive wear of the corners of the cutting teeth that directly form the profile of the extended surface.

The manufacture of solid spline broaches working according to the profile scheme is technologically much more complicated, since this requires the use of a grinding wheel of very small diameter, as well as a non-optimal design of the broach with increased tooth pitch. In this case, the formation of the profile of the teeth of the broach can be carried out by movement of the backing in a straight line. However, in practice, due to the great complexity, this method is not used.

The problem of obtaining slotted broaches of a profile cutting scheme is solved both by the creation of new designs of broaches and by improving the technology for their manufacture.

For example, a spline broach is known, comprising a tail portion, front and rear guides, and a cutting portion including bevel, round and spline teeth with spline protrusions having a sectional structure, and after the main spline teeth there is a group of three to five additional spline teeth, spline protrusions of which are equipped with lateral cutting edges, with outer diameters equal to the diameters of the last main spline teeth, and spline protrusions are 0.05-0.20 mm wider, and the front surfaces are stupas are made of a radial shape with a radius increasing from the top to the base of the spline protrusion so that they form front angles γ = 10-15 ° and inclination angles γ = 5-10 ° at the lateral edges (patent RU No. 71087, B23D 43/00 ( 2006/01), published on 02.27.2008).

The broach design is equipped with a group of additional teeth with a larger thickness, which remove the allowance along the width of the splined cavity and eliminate microroughness in the form of steps. However, the manufacturability of such a broach is significantly impaired. This is due to the fact that when grinding on the passage of the main teeth, it is necessary to ensure the exit of the grinding wheel, while in this design additional, having a large thickness, are located behind the main teeth. To ensure the exit of the grinding wheel, a constructive deterioration of the broach is inevitable, namely, a significant gap between the main and additional teeth, equal to at least 3 ... 4 tooth steps.

Another approach is to develop prefabricated broaches. So known prefabricated broach for machining internal surfaces, mainly splined, containing a mandrel with front and rear shanks and removable working sections with cutting and calibrating teeth and a guide section mounted on the mandrel in the technological sequence with their central mounting holes, and the mandrel, at least the place of installation of removable sections, made in the form of a rod with an external equiaxial triangular PK profile, and the landing holes of the sections are made in the form of reciprocal PK -profile of the mandrel (patent RU No. 90002, B23D 43/00 (2006.01), publ. 27.12.2009).

Also known is the design of a prefabricated broach for processing involute splines, comprising a housing with shanks and a cutting part made thereon, made according to the generator pattern and having teeth with a corrected profile, at least two cutting discs containing lapping teeth made according to the profile pattern and oriented relative to each other by means of eccentrics located in the holes of one disk and entering into the grooves on the other disk and the guide sleeve, rigidly fixed to the housing and pressing the drive disks to the generator part of the broach in the axial direction, and the total feed A of the final teeth is chosen from the following condition:

A> S _z sin δ / cos β,

where S _z - the feed of the teeth of the generator part of the broach, mm;

δ is the angle of undercut;

β is the angle of the profile of the generating teeth (patent RU No. 70473, B23D 43/02 (2006.01), publ. 27.01.2008).

The execution of the broach team, equipped with interchangeable sections, allows you to provide them with any desired profile with optimal rear angles. For this, each section is made separately, after which they are all mounted on a mandrel. Broaches of a similar design can be made with generator, profile or combined cutting schemes. There is no need to technologically increase the dimensions of the broach (as in the previous version).

For the manufacture of such tools, a method of manufacturing a prefabricated calibrating broach for slotted holes can be applied, including grinding the side surfaces of the profile of the cutting elements mounted on the broach, when installing the rear end of the broach above the front one, and the cutting elements are placed on the broach before grinding in the reverse order to their location in working position, and after grinding rearrange, arranging in the order of the working position (AS USSR No. 998023, M. C. ³ B23D 43/02, publ. 02.23.1983).

The manufacture of broaches according to this method allows you to get a small increase in the width of the profile on the teeth, which provides a profile cutting scheme. The method allows both broaches operating only according to the profile cutting scheme, and combined, when the first teeth work according to the generator cutting scheme and effectively remove the main part of the allowance, and the last few teeth work according to the profile scheme, remove a small allowance along the width of the depression and strip the sides of the splines. In its performance, the method is fully consistent with the methods of processing generator broaches.

The disadvantage of this method is its applicability only for modular broaches, which have lower accuracy compared to whole. The reason for this is a large number of elements processed in different basing cycles, as well as a large number of conjugations with a certain non-rigidity. In addition, as the broach is used, it is assembled and disassembled to replace the cutting elements, wear of the landing elements occurs, which also reduces the accuracy of the location of the cutting elements.

There is a method of adjusting the broach profile for processing involute splines, which consists in the fact that the correction is carried out in two stages, the first is grinding the arc (a) and its continuation, the arc (d) with a small inverse taper, and the second stage is grinding the arc (b) with greater inverse taper, the grinding wheel has a profile in the form of an arc of a circle with a radius corresponding to the arc (a) and, accordingly, (b), and in the case of high profiles at the first stage, at different sections of the broaching length, it is performed with different radii (RO No. 87337, IPC B23F 21/26, publ. 30.07.1 985).

The method can be implemented on most modern machines. For example, on a CNC machine according to the patent of the People’s Republic of China No. 201519895, it is possible to install broach blanks in centers with the possibility of controlled rotation. The carriage is installed on the machine, providing movement of the grinding wheel in at least three directions (along the axis of the broach, in the transverse direction and radially). Thus, the machine provides at least four controllable coordinates.

The method provides receiving on the spline teeth of the broach large values of the gap on the sides, which reduces the friction of the teeth on the already processed sections of the side sides of the splines of the part. However, the obtained broach also works according to the generator circuit and will form a stepped profile on the part.

The technical problem to which the invention is directed is to improve the method of manufacturing broaches and provide the possibility of processing their spline teeth with a variable (increasing) tooth thickness to implement a profile cutting scheme.

This problem is solved by the fact that in the method of processing the profile of the teeth of the slotted broaches, including grinding the profile of the teeth of the broaches in two stages, at the first of which the profile of the rough and transition teeth is ground for passage with inverse taper, in the second stage the profile of the fine and calibrating teeth is ground with zero the inverse taper of the radius sections at the top of the grinding wheel profile with consistent continuous rotation of the broach and vertical movement of the grinding wheel, the coordinate Z _{i of the} center of the radius section to otoro connected with the angle of rotation of the broach φ _{i the} following system of equations:

where Y ₀ is the ordinate of the center of the radius of the grinding wheel;

D _b - the diameter of the main circle of the involute profile of the teeth of the broach;

θ is half the angular width of the depression along the diameter of the main circle;

α _i is the pressure angle of the involute at the contact point of the lateral involute surface of the broaching tooth and the radius section at the top of the grinding wheel;

R _k is the radius at the top of the grinding wheel,

the center of the grinding wheel is located at a distance l from the top of the grinding tooth in the longitudinal direction, which is determined by the following relationship:

l = (t-Δ) / 2,

where t is the tooth pitch of the broach;

Δ is the gap between the surface of the grinding wheel and the cutting edge of the next tooth broach.

The implementation of the method of processing the profile of the teeth of the slotted broaches, including grinding the profile of the teeth of the broach in two stages, the first of which grind the profile of rough and transition teeth in the passage, in combination with grinding in the second stage of the profile of the fine and calibrating teeth with zero inverse taper radius sections at the top of the grinding wheel profile with consistent continuous rotation of the broach and vertical movement of the grinding wheel, the coordinate Z _{i of the} center of the radius portion of which is related to the angle of rotation the broach company φ _{i by the} reduced system of equations, and the location of the center of the grinding wheel at a distance l from the top of the grinded tooth in the longitudinal direction, determined by the given dependence, will allow to draw a broach of the combined cutting pattern, with rough and transition teeth, according to the generator cutting pattern (tooth thickness is variable, decreasing), and with fine and calibrating teeth according to the profile cutting scheme (tooth thickness is variable, increasing and constant), having significant rear angles on the side st orony. Broaches made using this method will provide higher quality of the processed surface and accuracy of the splined hole.

The applicant does not know how to process the profile of the teeth of the slotted broaches with the specified combination of features, and the claimed combination of features does not follow explicitly from the existing level of technology, which confirms the compliance of the claimed technical solution with the criteria of "novelty" and "inventive step".

The claimed technical solution is illustrated by drawings, where:

FIG. 1 - grinding the profile of the teeth of the rough and transition teeth of the broach;

FIG. 2 is a section AA in FIG. one;

FIG. 3 - cyclogram of the process of grinding the profile of rough and final teeth broaching;

FIG. 4 - grinding the profile of the fine and calibrating teeth of the broach;

FIG. 5 - remote element B in FIG. four;

FIG. 6 is a view B in FIG. 5;

FIG. 7 is a diagram for calculating the parameters of rotation of the broach and vertical movement of the grinding wheel.

The method of processing the profile of the teeth of the slotted broaches consists in grinding the profile of the teeth of the broach 1 in two stages. At the first stage, the profile of rough and transition teeth 2 is ground to the passage with reverse taper. At the second stage, the profile of the fine and calibrating teeth 3 is ground with zero inverse taper. Grinding is performed with radius sections 4 at the top of the profile of the grinding wheel 5. In this case, a continuous rotation of the broach 1 and vertical movement of the grinding wheel 5 occurs, the coordinate Z _{i of the} center of the radius section 4 of which is related to the angle of rotation of the broach φ _{i by the} following system of equations (Fig. 7) :

where Y ₀ is the ordinate of the center of the radius of the grinding wheel;

D _b is the diameter of the main circumference of the involute profile;

θ is half the angular width of the depression along the diameter of the main circle;

α _i is the pressure angle of the involute at the contact point of the lateral involute surface of the broaching tooth and the radius section at the top of the grinding wheel;

R _k is the radius at the top of the grinding wheel.

The center of the grinding wheel 5 is located at a distance l from the top of the grinding tooth 6 in the longitudinal direction, which is determined by the following dependence:

l = (t-Δ) / 2,

where t is the tooth pitch of the broach;

Δ is the gap between the surface of the grinding wheel and the cutting edge of the next tooth broach.

The processing process of a spline involute broach is as follows. The workpiece broach 1 with pre-cut teeth set in the centers 7 of a grinding and grinding machine with CNC (not shown). The front shank of the broach is clamped in the cams 8 of the lead cartridge (Fig. 1 and 4). The rotation of the broach sets the verticality of the plane of symmetry of the first splined cavity on the broach tooth. Then grind the rough and transition teeth 2 broaches on the passage with reverse taper. In this case, the grinding wheel is moved according to the NC program along the X axis with a slight movement along the Z axis according to the sequence diagram shown in FIG. 3. In the direction of movement of the grinding wheel 5, the sides of the rough and transition teeth are located on the same surface (Fig. 2). Due to this, it is possible to grind them with high performance. After grinding one spline cavity, the grinding wheel is raised along the Z axis, the broach is turned by the angular pitch of the splines, and the next cavity is ground. As a result, teeth are formed on the broach with a variable (decreasing) thickness of the slot and small posterior angles (10 ′ ... 15 ′) on the sides. After processing all the depressions on the rough and transition teeth, the profile of the final and calibrating teeth 3 is ground with the same grinding wheel (Fig. 4). To do this, the grinding wheel is moved along the X axis by a distance l from the top of the first final tooth 6 (Fig. 5, 6). Then include the coordinated rotation of the broach 1 and the vertical movement of the grinding wheel 5 (Fig. 7). Based on the above mathematical dependencies, the speeds of these movements are determined, the point is contacted on the radius section 4 of the grinding wheel 5 and the side of the slot on the grinding tooth. After processing one side of the cavity, the grinding wheel is returned to its original position, and with the opposite direction of rotation of the broach, the second side of the cavity is ground. After that, the grinding wheel is raised along the Z axis, the broach is turned by an angular step, and the treatment is repeated for the next cavity. After processing all the sides of the splines of one tooth, the grinding wheel is moved to the next tooth and the treatment is repeated. As a result, teeth are formed on the broach with a variable (increasing) or constant thickness of the slot and acceptable rear angles (1 ° 30 ′ ... 2 °) on the sides. After processing the sides on all finishing and calibrating teeth, sharpen the rear corner along the tops of all the teeth and remove the broach.

The implementation of the method will be considered on the example of the manufacture of broaches for processing the internal involute splines of the pinion drive gear.

Initial data:

m = 2.5 mm - module;

Z = 20 is the number of splines;

α = 30 ° - profile angle;

D _a = 55.3 mm - the maximum diameter of the tops of the teeth of the broach;

D _l = 50,605 - the diameter of the boundary points of the profile of the teeth of the broach;

θ = -0.37081 ° - half the angular width of the depression along the diameter of the main circle;

R _k = 1.44 mm is the radius at the top of the grinding wheel.

Y ₀ = 0.1619 mm - the ordinate of the center of the radius of the grinding wheel;

t = 16 mm - the pitch of the teeth of the broach;

Δ = 1 mm - the gap between the surface of the grinding wheel and the cutting edge of the next tooth broach.

The diameter of the main circle:

D _b = mzcosα = 2.5 · 20 · cos30 ° = 43.300127 mm.

A number of points are distinguished on the tooth profile, a greater number of which will provide higher profile accuracy. In this example, nine points are selected on the profile, the diameters of which D _i are selected with a uniform pitch in the range D _l ... D _a .

For each profile point, the involute pressure angle is calculated using the formula α _i = arccos (D _b / D _i ). Further, substituting all the values calculated above into the system of equations and solving it numerically for each profile point, we obtain the values of the turning angle φ _i and the coordinate of the center of the radius section of the grinding wheel Z _i . The calculation results are presented in table 1.

Based on the calculation results, a control program is generated for the CNC grinding machine. An example of the control program code for grinding one side of the cavity is presented below (coordinate A - rotation of the broach around the X axis):

G1 A0.0541 Z26.0761

A0.5294 Z26.3914

A1.0143 Z26.7053

A1.5081 Z27.0180

A2.0104 Z27.3296

A2.5205 Z27.6402

A3.0382 Z27.9500

A3.5630 Z28.2588

A4.0946 Z28.5669

The distance from the center of the grinding wheel to the top of the grinding tooth in the longitudinal direction is determined by the formula

l = (t-Δ) / 2 = (16-1) / 2 = 7.5 mm.

The method of processing the profile of the teeth of the slotted broaches can be implemented on modern equipment using well-known materials and modern tools, which meets the criterion of "industrial applicability".

Claims (1)

A method of processing the profile of the teeth of a slotted broach, including grinding the profile of the teeth of the broach in two stages, at the first of which the profile of rough and transition teeth is ground for passage with inverse taper, characterized in that at the second stage the profile of fine and calibrating teeth is ground with zero inverse taper radius areas at the top of the grinding wheel profile with consistent continuous rotation of the broach and vertical movement of the grinding wheel, the coordinate Z _{i of the} center of the radius portion of which is connected with the rotation angle φ _{i of the} following system of equations:

where Y ₀ is the ordinate of the center of the radius of the grinding wheel;
D _b is the diameter of the main circumference of the involute profile of the broach tooth;
θ is half the angular width of the depression along the diameter of the main circle;
α _i is the pressure angle of the involute at the contact point of the lateral involute surface of the broaching tooth and the radius section at the top of the grinding wheel;
R _k is the radius at the top of the profile of the grinding wheel,
the center of the grinding wheel is located at a distance l from the top of the grinding tooth in the longitudinal direction, which is determined by the following relationship:

where t is the tooth pitch of the broach;
Δ is the gap between the surface of the grinding wheel and the cutting edge of the next tooth broach.

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