Reaming eccentric transition calculation guide. Construction of developments of surfaces of geometric bodies. Calculation of cone development

We often encounter surface developments in everyday life, in production and in construction. To make a case for a book (Fig. 169), sew a cover for a suitcase, a tire for a volleyball, etc., you must be able to construct developments of the surfaces of a prism, ball and other geometric bodies. A development is a figure obtained by combining the surface of a given body with a plane. For some bodies, scans can be accurate, for others they can be approximate. All polyhedra (prisms, pyramids, etc.), cylindrical and conical surfaces, and some others have precise developments. Approximate developments have a ball, a torus and other surfaces of revolution with a curved generatrix. We will call the first group of surfaces developable, the second - non-developable.

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When constructing developments of polyhedra, you will have to find the actual size of the edges and faces of these polyhedra using rotation or changing projection planes. When constructing approximate developments for non-developable surfaces, it will be necessary to replace sections of the latter with developable surfaces close in shape to them.

To construct a scan of the lateral surface of the prism (Fig. 170), it is assumed that the scan plane coincides with the face AADD of the prism; other faces of the prism are aligned with the same plane, as shown in the figure. The face ССВВ is preliminarily combined with the face ААВВ. Fold lines in accordance with GOST 2.303-68 are drawn with thin solid lines with a thickness of s/3-s/4. Points on the scan are usually denoted by the same letters as on the complex drawing, but with index 0 (zero). When constructing a development of a straight prism according to a complex drawing (Fig. 171, a), the height of the faces is taken from the frontal projection, and the width from the horizontal one. It is customary to build a scan so that the front side of the surface is facing the observer (Fig. 171, b). This condition is important to observe because some materials (leather, fabrics) have two sides: front and back. The bases of the ABCD prism are attached to one of the faces of the side surface.

If point 1 is specified on the surface of the prism, then it is transferred to the development using two segments marked on the complex drawing with one and two strokes, the first segment C1l1 is laid to the right of point C0, and the second segment is laid vertically (to point l0).

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Similarly, a development of the surface of the cylinder of rotation is constructed (Fig. 172). Divide the surface of the cylinder into a certain number of equal parts, for example 12, and unfold the inscribed surface of a regular dodecagonal prism. The sweep length with this construction turns out to be slightly less than the actual sweep length. If significant accuracy is required, then a graphic-analytical method is used. The diameter d of the circumference of the base of the cylinder (Fig. 173, a) is multiplied by the number π = 3.14; the resulting size is used as the development length (Fig. 173, b), and the height (width) is taken directly from the drawing. The bases of the cylinder are attached to the development of the side surface.

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If point A is given on the surface of the cylinder, for example, between the 1st and 2nd generatrices, then its place on the development is found using two segments: a chord marked with a thick line (to the right of point l1), and a segment equal to the distance of point A from the upper base of the cylinder , marked in the drawing with two strokes.

It is much more difficult to construct the development of a pyramid (Fig. 174, a). Its edges SA and SC are straight general position and are projected onto both projection planes with distortion. Before constructing the development, it is necessary to find the actual value of each edge. The size of the edge SB is found by constructing its third projection, since this edge is parallel to the plane P3. The ribs SA and SC are rotated around a horizontally projecting axis passing through the vertex S so that they become parallel to the frontal plane of projections P (the actual value of the rib SB can be found in the same way).

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After such a rotation, their frontal projections S 2 A 2 and S 2 C 2 will be equal to the actual size of the ribs SA and SC. The sides of the base of the pyramid, like horizontal straight lines, are projected onto the projection plane P 1 without distortion. Having three sides of each face and using the serif method, it is easy to construct a development (Fig. 174, b). Construction begins from the front face; a segment A 0 C 0 = A 1 C 1 is laid out on a horizontal straight line, the first notch is made with a radius A 0 S 0 - A 2 S 2 the second - with a radius C 0 S 0 = = G 2 S 2 ; at the intersection of the serifs, point S„ is obtained. Accept the order side A 0 S 0 ; from point A 0 make a notch with radius A 0 B 0 =A 1 B 1 from point S 0 make a notch with radius S 0 B 0 =S 3 B 3 ; at the intersection of the serifs, point B 0 is obtained. Similarly, the face S 0 B 0 C 0 is attached to the side S 0 G 0 . Finally, a base triangle A 0 G 0 S 0 is attached to side A 0 C 0 . The lengths of the sides of this triangle can be taken directly from the development, as shown in the drawing.

The development of a cone of rotation is constructed in the same way as the development of a pyramid. Divide the circumference of the base into equal parts, for example into 12 parts (Fig. 175, a), and imagine that a regular dodecagonal pyramid is inscribed in the cone. The first three faces are shown in the drawing. The surface of the cone is cut along the generatrix S6. As is known from geometry, the development of a cone is represented by a sector of a circle whose radius is equal to the length of the cone generatrix l. All generatrices of a circular cone are equal, therefore the actual length of the generatrix l is equal to the frontal projection of the left (or right) generatrix. From the point S 0 (Fig. 175, b) a segment of 5000 = l is laid vertically. An arc of a circle is drawn with this radius. From the point O 0, the segments Ol 0 = O 1 l 1, 1 0 2 0 = 1 1 2 1, etc. are laid off. By setting aside six segments, we get point 60, which is connected to the vertex S0. The left part of the scan is constructed in the same way; The base of the cone is attached below.

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If you need to put point B on the scan, then draw the generatrix SB through it (in our case S 2), apply this generatrix to the scan (S 0 2 0); rotating the generatrix with point B to the right until it aligns with the generatrix S 3 (S 2 5 2), find the actual distance S 2 B 2 and set it aside from the point S 0. The found segments are marked on the drawings with three strokes.

If it is not necessary to plot points on the cone scan, then it can be constructed faster and more accurately, since it is known that the scan sector angle is a=360°R/l, the radius of the base circle, and l is the length of the cone generatrix.

To make machine casings, machine enclosures, ventilation devices, pipelines, it is necessary to cut out their developments from sheet material.

Surface development polyhedron is a flat figure obtained by combining with the drawing plane all the faces of the polyhedron in the sequence of their location on the polyhedron.

To construct a development of the surface of a polyhedron, you need to determine the natural size of the faces and draw all the faces sequentially on the plane. The true dimensions of the edges of the faces, if they are not projected in full size, are found by the methods of rotation or changing projection planes (by projecting onto an additional plane) given in the previous paragraph.

Let's consider the construction of surface developments of some simple bodies.

Development of the surface of a straight prism is a flat figure made up of side faces - rectangles and two equal base polygons. For example, a regular right hexagonal prism is taken (Fig. 176, a). All side faces of the prism are rectangles, equal in width a and height H; The bases of the prism are regular hexagons with a side equal to a. Since we know the true dimensions of the faces, it is not difficult to construct a development. To do this, six segments are sequentially laid on a horizontal line equal to the side of the base of the hexagon, i.e. 6a. From the obtained points, perpendiculars equal to the height of the prism H are constructed, and a second horizontal line is drawn through the end points of the perpendiculars. The resulting rectangle (H x 6a) is a development of the lateral surface of the prism. Then the base figures are placed on one axis - two hexagons with sides equal to a. The outline is outlined with a solid main line, and the fold lines are outlined with a dash-dotted line with two dots.

In a similar way, you can construct developments of straight prisms with any figure at the base.

Development of the surface of a regular pyramid is a flat figure made up of lateral faces - isosceles or equilateral triangles and a regular base polygon. For example, a regular quadrangular pyramid is taken (Fig. 176, b). Solving the problem is complicated by the fact that the size of the side faces of the pyramid is unknown, since the edges of the faces are not parallel to any of the projection planes. Therefore, the construction begins with determining the true value of the inclined edge SA. Having determined by the method of rotation (see Fig. 173, c) the true length of the inclined edge SA, equal to s"a` 1 (Fig. 176, b), an arc of radius s"a` 1 is drawn from an arbitrary point O, as from the center. Four segments are laid on the arc, equal to side the base of the pyramid, which is projected in the drawing to its true size. The found points are connected by straight lines to point O. Having obtained a development of the lateral surface, a square equal to the base of the pyramid is attached to the base of one of the triangles.

Development of the surface of a right circular cone is a flat figure consisting of a circular sector and a circle (Fig. 176, c). The construction is carried out as follows. Draw an axial line and from a point taken on it, as from the center, with a radius Rh equal to the generatrix of the cone sfd, outline an arc of a circle. In this example, the generator, calculated using the Pythagorean theorem, is approximately equal to

A development is a figure obtained by combining a surface with a plane. Naturally, a closed surface cannot be combined with a plane without discontinuities. The surface is first cut along certain lines and then aligned with the plane. The construction of surface developments is of great practical interest in the design of various structures and products made from sheet material. The development stores the lengths of the lines lying on the surface, the values ​​of the angles between the lines and the areas of the figures formed by closed lines. To construct a surface development, it is necessary to know the law of transformation of surface guide lines into lines on the development plane and the law of distribution of straight lines corresponding to the surface generatrices. The law for converting a surface into a development can be specified both by analytical dependencies and by a graphical algorithm.

Already in the very first works on descriptive geometry, algorithms for constructing precise developments of a cylinder, cone and torso of a helicoid (an open helical surface) were well developed. Surface development means the alignment of a part (compartment) of a surface with a plane. Part of the cylinder is cut by one of the generatrices and aligned with the plane. The development of the lateral surface of a right circular cylinder is depicted as a rectangle with a height l and length πd, Where l– length of the generatrix of the cylindrical surface, d– diameter of the cylinder base (Fig. 5.19).

Rice. 5.19. Development of a right circular cylinder

In addition to straight lines of bending and torsion, many other straight lines can be drawn on a development, which correspond to geodesic lines on the surface that determine the shortest distances between points on the surface. On a cylindrical and conical surface, the geodesic line is a helix.

The development of a right circular cone is a sector of a circle with a radius l and angle φ , equal to or 2π∙cosβ, Where l– length of the generatrix, d– diameter of the base of the cone (Fig. 5.20). The cone and cylinder are considered as a special case of a surface with a return edge, when the return edge degenerates into a finite and infinitely distant point. The conical surface also has two floors lying on opposite sides of the top of the cone.

Rice. 5.20. Development of a right circular cone

In Fig. 5. 21 shows an example of constructing a development of one floor of a helicoid limited by a return edge (helis - a cylindrical helical line with a diameter d), horizontal planes with a distance between equal h(height h). The surface is cut along the return edge and one of the generatrices and aligned with the plane. The helix on the development is converted into a circular arc with a radius ρ and angle φ . The length of the circular arc is equal to the length of the helix ( L=π d/cosβ). Radius value ρ we determine from the equality 2 π ρ φ/360°= π d/ cosβ. Where ρ = d 180°/ cosβ∙φ. The generators of the helicoid are parallel to the generators of the guide cone, hence the sum of the angles between the generators of the helicoid is equal to the sum of the angles between the guides of the cone ( φ = 2π∙cosβ). If instead φ substitute its value, we get ρ = d / 2cosβ 2.

A surface with a return edge has two floors lying on different sides of the points of contact. If the return edge is a flat curved line, then the surface turns into a plane.

On ruled surfaces of a general type, compression lines can be distinguished (the throat of a single-sheet hyperboloid, the narrowing line of an oblique plane, the striction lines of a cylindroid, etc.), at which nearby generating surfaces intersect. Compression lines are an analogue of the return edge, with the only difference being that the generators do not touch the compression line, but intersect it at some angle. Cylindrical, conical and return-edge surfaces can be obtained from the development plane using bending deformation. Ruled surfaces of a general form are obtained from the development plane using torsional and bending deformations. We also note that it is possible to obtain a surface from the development plane using bending only theoretically, but in practice the presence of compression and tension deformations is inevitable, since there are no products without thickness.

Rice. 5. 21. Development of an involute (open) helicoid

Development of the surface of a straight closed helicoid compartment with a step N and the diameter of the cylindrical helix d is an incomplete ring (Fig. 5.22). The pitch of the helical surface unfolds into the length of an arc of a circle with a diameter d 1, Then, Н = π d 1 ∙ φ/360°. Let's determine the angle φ from the obtained dependence: φ = N ∙360°/π d 1.The helical line unfolds into the length of an arc of a circle with a diameter D. Then, L = πd/cosβ = π D ∙ φ/360°. D = d + d 1. Let's substitute the value D into the previous expression: L = πd/cosβ = π(d + d 1) ∙ φ/360°. Let's determine the angle φ , φ = πd360°/cosβ(d + d 1). Diameter size d 1 can be determined from a comparison of formulas for determining the angle φ : d 1 = Нd cosβ/(π 2 d – Нcosβ) or d 1 = d sinβ/(π –sinβ).

Rice. 5.22. Development of a straight closed helicoid

Development of the surface of a compartment of an annular closed helicoid with a step N and the diameters of the internal and external cylindrical helical lines d And d׳ is also an incomplete ring (see Fig. 5.22). The inner helix unfolds into the length of an arc of a circle with a diameter d'.Then, L׳ = πd/cosβ = π d׳ ∙φ/360°. Let's determine the angle φ , φ = d360°/cosβ d׳. The outer helix unfolds into the length of an arc of a circle with a diameter D. Then, L = πd/cosβ = π D ∙ φ/360°. D = (d – d׳ ) + d 1. Let's substitute the value D into the previous expression: L = πd/cosβ = π(d – d׳ + d 1) ∙ φ/360°. Let's determine the angle φ , φ = d360°/cosβ(d – d׳ + d 1).

The development of the surface of a compartment of an oblique closed helicoid is a twisted ring; the forming surfaces on the development touch a circle of a certain radius. The development of the surface of a compartment of a single-sheet hyperboloid of revolution is also a twisted ring, the forming surfaces on the development touch a circle of a certain radius. The throat of the surface unfolds into the circular arc of the inner circular arc, and the base of the single-sheet hyperboloid unfolds into the circular arc of the outer circular arc. To construct a development of a ruled surface, it is necessary to know the law of transformation of the guide lines of the surface into lines on the development plane and the law of distribution of straight lines corresponding to the generatrices of the surface. The law for converting a surface into a development can be specified both by analytical dependencies and by a graphical algorithm. A development of a ruled surface is constructed for one floor of a limited part of the surface. The division of the surface into floors occurs along the compression line.

If the pattern of transition from the surface to the development is unknown, then an approximate development is constructed. To do this, the surface is replaced by an inscribed or circumscribed polyhedral surface and its development is constructed. If the surface is divided into many triangles, then the method is called triangulation. The construction of a development is associated with determining the natural size of each face. The metric problems discussed in previous lectures are integral part construction of a sweep. Constructing sweeps is a complex metric task in which it is important to rationally organize graphical constructions in order to achieve accuracy and speed of construction.

For a truncated cylinder and a cone, as well as for inclined cylindrical and conical surfaces and other surfaces, approximate developments are constructed, since the issues of constructing developments have not been sufficiently studied: it is necessary to establish a geometric projection relationship between surfaces and their developments.

Let's consider an example of constructing a development of a prism using the rolling method and the normal section method. Let's cut the prism along the edge AA׳ and we will rotate its faces around the edges until they align with the frontal plane passing through the edge AA׳ . Points IN, IN ׳ , WITH And WITH When rotating, they move in planes perpendicular to the ribs (Fig. 5.23). From point A 2 draw an arc of radius A 1 B 1 to the intersection with the perpendicular from AT 2 To A 2 A 2׳ and we get V o. We obtain the remaining points in the same way. Let's attach the lower and upper bases and get a full development of the prism. Let's cut the prism with a plane α , perpendicular to the ribs, and determine the natural size of the section A"B"C" ׳ , for example, combining it with π 1. A normal section unfolds into a straight line A o B o C o.

Rice. 5.23. Development of an inclined prism

In practice, developments are also constructed for non-expanding non-ruled surfaces; for this purpose, they are approximated by developable surfaces (they are divided into parts, which are replaced by planes or developable surfaces, i.e., several cylindrical, conical or other surfaces are inscribed or described around them), and then constructed sweeps for them. The resulting development of the entire surface is conditional, since it consists of many individual flat figures; to obtain a surface, they must be glued together and individual sections must be subjected to compression and tension. The greater the number of partitions, the smaller the pieces into which the surface breaks up. This is the fundamental difference between conditional and approximate sweeps.

The invention relates to metal forming and can be used in the manufacture of eccentric transitions between large-diameter pipes in the production of heat exchangers. A straight cone blank is obtained, from which a truncated eccentric cone blank is formed with bases of small and large diameters and a conical surface, one of the lines of which is perpendicular to the bases. The formation of a truncated eccentric cone blank is carried out by trimming the ends of a straight cone blank. An eccentric transition is obtained by flanging large and small diameters using a punch and a matrix. Moreover, for flanging a small diameter, the workpiece of a truncated eccentric cone is placed vertically with the small diameter upwards, the matrix is ​​placed around the small diameter with its inner surface touching the outer surface of the workpiece at at least four points, the punch is advanced inside the small diameter of the workpiece parallel to the line on the conical surface perpendicular to the bases. For large-diameter flanging, a punch is used instead of a matrix and, accordingly, a matrix is ​​used instead of a punch. Technological capabilities are expanding. 7 ill.

Drawings for RF patent 2492016

The invention relates to metal forming and can be used in the manufacture of eccentric transitions between large-diameter pipes in the production of heat exchangers.

There is a known method for manufacturing pipes in cold pipe rolling mills, according to which a pre-prepared initial hollow billet is fed along the rolling axis by a certain amount (feed amount) into the deformation zone and is compressed by rotating rolls with a variable radius of the stream while simultaneously moving the rolling stand (direct movement of the stand) in direction of supply of the workpiece (Technology and equipment of pipe production; tutorial for universities / V.Ya. Osadchiy, A.S. Vavilin, V.G. Zimovets, A.P. Kolikov. - M.: Intermetengineering, 2007. - pp. 448-452). In the final (extreme) position of the stand, the strands of the rolls form a caliber, the size of which ensures the free passage of the workpiece through it (the idle section of the longitudinal development of the strand profile). At this moment, the workpiece with the mandrel is rotated around its axis at a given angle (turned), after which the rolling stand moves in the opposite direction to its original position (reverse stroke of the stand) with simultaneous deformation of the workpiece section that was previously compressed during the forward stroke of the stand. Next, the workpiece is bent again and the above-described cycle of processing the workpiece on the mandrel is repeated many times until a finished pipe is obtained.

The described method of rolling pipes involves metal deformation using interchangeable tools and equipment in the form of gauges, gears and racks, made up of pairs of absolutely identical parts, which creates symmetry of the deformation process relative to the horizontal plane. In this process, the mandrel is self-aligned in the radial direction relative to the inner diameter of the pipe, which does not significantly reduce the value of the eccentric component of the wall difference and reduces the accuracy of cold-deformed pipes obtained by this method. In addition, high rolling forces, which require an increase in the mass of deforming equipment and cause large elastic deformations stands also lead to a decrease in the accuracy of finished pipes, including those made of hard-to-deform steels and alloys.

The closest to the proposed method is the method of manufacturing pipes with an eccentric transition by relative displacement of sections of a tubular blank with a conical transition, according to which a cylindrical section with a smaller diameter is rigidly fixed, and an internal support is created on a cylindrical section with a larger diameter, then it and the conical transition are sequentially bent relative to a cylindrical section with a smaller diameter (USSR Author's Certificate No. 806210, published 02/23/1981 - prototype).

The known method can only be applied to pipes of small diameter and does not allow the production of transitions of large diameter, i.e. diameter more than 1 m.

The problem is solved by the fact that in the method of manufacturing an eccentric transition, including obtaining a blank of a straight cone, forming from it a blank of a truncated eccentric cone with bases of small and large diameters and a conical surface, one of the lines of which is perpendicular to the bases, according to the invention, the formation of a blank of a truncated eccentric cone is carried out by cutting the ends of the workpiece of a straight cone, which is placed with a large diameter downwards, tilted until one line is taken on its conical surface in a vertical position, from the top point of which a horizontal line is drawn, along which the upper part of the workpiece of a straight cone is cut off, and its lower part is cut off along a horizontal line, drawn from the top point of the large base, raised when tilted, the eccentric transition is obtained by flanging large small diameters using a punch, and for flanging a small diameter, the workpiece of a truncated eccentric cone is placed vertically with the small diameter upward, the matrix is ​​placed around the small diameter with its inner surface touching the outer surface of the workpiece at no less than four points, the punch is advanced inside the small diameter of the workpiece parallel to a line on the conical surface perpendicular to the bases, and for flanging of a large diameter, a punch is used instead of a matrix and, accordingly, a matrix is ​​used instead of a punch.

The essence of the invention

In the field of mechanical engineering, and more precisely in the field of manufacturing heat exchangers, today there is the task of manufacturing eccentric transitions between large-diameter pipes with flanged ends. This task, as a rule, is either not performed or is performed using workaround technologies that damage the structure of the metal. Existing equipment is not adapted to solve these particular problems, and enterprises that have this equipment are often still forced to resort to workaround technologies when fulfilling orders.

The proposed invention solves the problem of manufacturing an eccentric transition of large diameter.

A general view of the eccentric transition is shown in Fig. 1. In Fig.1, d is the small diameter of the transition, D is the larger diameter of the transition, I is the length of the cylindrical part of the transition of small diameter, L is the length of the cylindrical part of the transition of a larger diameter, S is the thickness of the transition wall, H is the length of the transition.

When manufacturing an eccentric transition, a reamer is made, from which a blank for the future transition is subsequently produced by sharp welding and shaping.

The workpiece is bent using a 3-roll machine. Figure 2 shows a diagram of the bending of the transition blank on a three-roll machine: 1 - transition blank, 2 - ends of the blank, 3 - rolls. After bending, the workpiece is butt welded at the ends 3. A straight cone of the workpiece is obtained. Next, begin trimming the ends of the workpiece. For ease of marking when cutting the ends of a straight cone, self-aligning construction laser levels are used to mark the vertical and horizontal planes simultaneously. Figure 3 shows the marking diagram: 4 - self-aligning construction laser levels, 5 - vertical planes, 6 - horizontal planes, 7 - cone generatrix. A straight cone 8 is placed with a large diameter at the bottom. The straight cone is tilted so that one line on the surface of the cone 8 takes a vertical position in the vertical plane. From the top point “A” of the vertical line, draw a horizontal line 9. Along this line, cut off the upper part of the cone 8. From the top point “B” on the larger diameter of the cone 8, which turns out to be raised when tilted, draw a horizontal line 10. Along this line, cut off the lower part cone 8. An eccentric cone 11 is obtained. Thus, an eccentric cone blank is made from a simple truncated cone, taking into account allowances by cutting off part of a straight cone. As a result, we obtain a flattened workpiece of the eccentric transition.

Prepare the matrix and punch for each end of the transition based on the thickness of the matrix and punch of at least 5 sizes of the cylindrical part of the transition I and L. For a small diameter of the transition, the preparation diagram is shown in Fig. 4 and 5, for a larger diameter of the transition - in Fig. 6 and 7.

In Figs 4 and 5 the following are indicated: 11 - eccentric cone, 12 - matrix, 13 - stops, 14 - zones for removing weld reinforcement, 15 - punch, 16 - cup, 17 - press. The width of the matrix 12 and the punch 15 is assigned to at least 3 corresponding thicknesses of the transition wall S. The matrix 12 and the punch 15 are equipped with devices for carrying out lifting operations (not shown). For a small transition diameter d, the diameter of the punch 15 is selected as nominal with a tolerance of + for the tolerance for changes in the thickness of the transition metal, the diameter of the matrix 12 is calculated from the diameter of the punch, +2 wall thickness S, +2 tolerance for wall thickness, +1.5 mm. For a larger transition diameter D, the main one is the matrix, and the derivative is the punch (the matrix diameter is chosen at nominal value with a tolerance in - for the tolerance for changes in wall thickness, the punch diameter is calculated from the matrix diameter, - 2 wall thickness, - 2 tolerances for wall thickness, - 1, 5 mm). The roughness of the working surfaces of the punch and matrix is ​​at least grade 11.

Figures 6 and 7 indicate: 11 - eccentric cone, 14 - zones for removing weld reinforcement, 17 - press, 18 - matrix, 19 - stops, 20 - punch, 21 - cup.

Prepare the equipment.

On the punch 15 for a small diameter and, accordingly, for a matrix with a larger diameter 18, after the radius of curvature of the inlet part there is a section with a slope of 20°±1°, the cylindrical part of the punch 15 or matrix 18 is at least half of their thickness. For a small diameter transition for the punch 15, a glass 16 is used for attachment to the press 17 with the possibility of removing the punch from the glass. The height of the cup 16 is calculated from the condition of the transition length H with tolerances + 3 punch thickness. For matrix 12, at least 3 stands are prepared with a height of 3 matrix thicknesses.

For a larger transition diameter, a glass 21 is prepared for the matrix and a stand for the punch 20 similarly to the above (Fig. 6).

A small diameter transition is flanged. To do this, the weld reinforcements in the stamping zone 14 are first removed (Fig. 4, Fig. 6). A matrix 12 is placed on a vertically mounted eccentric cone 11 with a small diameter upwards and installed in the working position, i.e. position of matrix 12 during stamping. The oval of small diameter is expanded in the area of ​​the smaller axis, and the oval is adjusted to the circle. For expansion, a hydraulic set is used, for example, for straightening bodies with a maximum force of at least 3 tons and a set of extensions. Ensure that the inner surface of the matrix 12 and the outer surface of the eccentric cone 11 touch at least 4 points “B” (for flanging of a larger diameter “D”). Check the largest gap between the matrix 12 and the eccentric cone 11. This affects the size of the gap between the lower plane of the matrix and the welded stops. From below, under the matrix, 4 stops are welded to the eccentric cone diametrically in 2 perpendicular planes with a gap equal to the thickness of the transition wall + half the maximum gap (Fig. 4). For stamping, a press with a maximum force of at least 100 tons and a span height capable of placing a pre-assembled structure under the working cylinder is used. Under the working cylinder, a structure is assembled from a matrix 12 on supports and an eccentric cone 11 with a glass 16 inserted into it with an installed punch 15. The glass 16 is attached to the platform of the working cylinder of the press 17. Lubricant (graphite or a mixture) is applied to the punch 15 and the inner surface of the eccentric cone 11 graphite powder and industrial oil or a mixture of talc and liquid soap). Turn on the press 17, move the punch 15 inside the eccentric cone 11 parallel to the vertical plane 5. Upon completion of stamping, remove the punch 15 from the glass 16 and the eccentric cone 11 from the glass 16. Flanging of the small diameter is completed.

For flanging of a larger diameter, preparatory operations are performed similar to those for flanging of a small diameter, with a difference in the operations for the punch and the matrix (instead of the matrix - a punch and, accordingly, instead of a punch - a matrix) (Fig. 6). Subsequently, flanging of a larger diameter is performed (Fig. 7).

Example of concrete execution

A transition with a flange of 1100-1600×12 mm is made. The flange size is 40 mm at both ends. According to Fig.1 d=1100 mm, D=1600 mm, I=L=40 mm, S=12 mm, r=R=20 mm, H=1500 mm.

The operations are performed according to Figs. 1-7. An eccentric transition with high surface quality is obtained.

Application of the proposed method will make it possible to perform an eccentric transition of a larger diameter.

CLAIM

A method for manufacturing an eccentric transition for connecting large-diameter pipes, including obtaining a straight cone blank, forming from it a truncated eccentric cone blank with bases of small and large diameters and a conical surface, one of the lines of which is perpendicular to the bases, characterized in that the formation of a truncated eccentric cone blank is carried out by cutting the ends of the straight cone workpiece, which is placed with a large diameter downwards, tilted until one line is taken on its conical surface in a vertical position, the upper part of the straight cone workpiece is cut off along a horizontal line drawn from the top point of the vertical line of the conical surface, and its lower part is cut off along the horizontal line drawn from the top point of the large base, raised when tilted, flanging of large and small diameters is carried out using a punch and a matrix, and for flanging a small diameter, a truncated eccentric cone blank is placed vertically with the small diameter upward, the matrix is ​​placed around the small diameter touching its inner surface the outer surface of the workpiece at at least four points, the punch is advanced inside the small diameter of the workpiece parallel to a line on the conical surface perpendicular to the bases, and for flanging a large diameter, a punch is used instead of a matrix and, accordingly, instead of a punch, a matrix is ​​used.

Picture 1

For the transition shown in rice. 1, the given values ​​are: hole diameter d, sides of the base a And b, height N.

Having drawn horizontal projections of the upper and lower bases, i.e. circle and rectangle, connect the vertices of the rectangle with points 0 and 3 of the circle, then construct a frontal projection of the transition.
The lateral surface of such a transition is a combined surface: it consists of four flat triangles marked on Fig.1, but in numbers I And II, and from four conical sections indicated by the number III. The vertices of these four equal conical surfaces lie at the vertices of the rectangle ( points s), and their bases coincide with the circle of the upper base of the transition.

On rice. 1, b the construction of the transition scan began with the construction of triangle I along the side b and height H1, equal to the segment s'ABOUT'(Fig. 1, a). Attached to it on both sides are developments of conical surfaces adjacent to it and tangent to it. III.

Natural lengths of the generatrices S 0 1 0 , S 0 2 0 , S 0 3 0 defined on rice. 1,a way right triangle and are correspondingly equal S 0 1 0, S 0 2 0, S 0 3 0. The length of the side l is taken to be equal to the length of the chord of one division of the base. Further construction of the development is clear from the drawing.

The error when replacing an arc with a chord for the corresponding number of divisions will be for the angle α = 30º ~ 1%(with the number of divisions 3), and with the number of divisions equal to four ( α = 22.5º), ~ 0,56% . (This does not take into account errors associated with graphical construction scans).

Analytical calculation

The natural lengths of the generators can be calculated using the formula

Formula 1
Where

• Lk - natural length of the corresponding generatrix;
• kα - the angle that determines the position of the projection of the generatrix;
• α = 180º/n when dividing half the base of a circle into n equal parts.

To do this, you need to first determine the value With.

From Figure 1, it is clear that:

Formula 2

Then, the divisions of the circle of the base of the transition must be numbered: put the number 0 at the horizontal projection of the largest generatrix and start counting the angles kα from it.
Size cos kα for the corresponding division can be determined from the table.

Figure 2

For its manufacture, in addition to dimensions H, d and a, you need to set the size e(displacement of the centers of the upper and lower bases). As in the previous case, connecting points s with points 0 And 3 circles, divide the lateral surface of the transition into four conical surfaces, indicated by numbers IV and V, and four triangles labeled I, II, III and tangents to conical surfaces.

The construction of the scan is similar to the previous one and is not shown in the drawing. The only difference is that the developments of the conical elements IV and V will in this case be unequal, and for triangles we will also have three different shapes.

Oblique transition from square to round cross-section

Figure 3

Lateral surface of transition to Fig.3 broken differently than the transitions shown in rice. 1 and 2. The midpoints of the sides of the base a and b (points s and s1) are connected to points 2 of the circle.

As a result of this construction side surface the transition will consist of eight triangles I and II tangent to four conical surfaces III And IV. The construction of this development is clear from Fig.3, b. It is similar to the previous ones, but requires more constructions.

Based on materials:
“Technical development of sheet metal products” N.N. Vysotskaya 1968 “Mechanical Engineering”