阅读说明：本技术 一种铁舾管放样展开方法 (Iron outfitting pipe lofting and unfolding method ) 是由 常志军 刘畅 钟毅 于 2021-07-27 设计创作，主要内容包括：本发明公开了船舶管道连接技术领域的一种铁舾管放样展开方法,包括主视图和侧视图的获取,主视图和侧视图上做等分参考圆,利用素线法获得相贯线及围长,利用素线法获取锥形管放样展开图的下边界和柱形管的相贯线开孔实样图。本发明先通过在锥形管的主视图和侧视图中做等分参考圆的方式,配合素线法获得锥形管和柱形管的相贯线,再通过素线法获取锥形管放样展开图的下边界和柱形管放样展开图的相贯线开孔实样图,提高了铁舾管的放样展开精度,保证了锥形管和柱形管的连接精度。(The invention discloses a lofting and unfolding method for an iron outfitting pipe, which belongs to the technical field of ship pipeline connection and comprises the steps of obtaining a front view and a side view, making equal reference circles on the front view and the side view, obtaining an intersecting line and a girth by using a plain line method, and obtaining a lower boundary of a tapered pipe lofting and unfolding diagram and an intersecting line hole opening real diagram of a cylindrical pipe by using the plain line method. According to the method, the intersecting line of the conical pipe and the cylindrical pipe is obtained by matching the plain line method in a mode of equally dividing the reference circles in the front view and the side view of the conical pipe, and then the lower boundary of the conical pipe lofting development diagram and the intersecting line hole opening real sample diagram of the cylindrical pipe lofting development diagram are obtained by the plain line method, so that the lofting development precision of the iron outfitting pipe is improved, and the connection precision of the conical pipe and the cylindrical pipe is ensured.)

1. A method for lofting and unfolding an iron outfitting pipe, which comprises a cylindrical pipe (10) and a conical pipe (20) which are connected in series, the method comprising:

s1: acquiring a front view and a side view of the through connection of the cylindrical pipe (10) and the conical pipe (20);

s2: in the front view, a first reference circle (30) is made by taking a reference point on the central line of the conical tube (20) as the center of a circle and the horizontal distance from the reference point to the generatrix of the conical tube (20) as a radius, the first reference circle (30) is divided into N equal parts, and a first oblique straight line is made by passing through the vertex o and the N equal parts of the conical tube (20);

in the side view, a second reference circle (40) is made by taking a reference point on the central line of the conical tube (20) as the center of a circle and the horizontal distance from the reference point to the generatrix of the conical tube (20) as a radius, the second reference circle (40) is divided into N equal parts, a second oblique straight line is made by passing through the vertex o and the N equal parts of the conical tube (20) and is intersected with the cylindrical tube (10), and a girth intersection point is obtained;

s3: a horizontal plain line (50) is made to cross the girth intersection point and is intersected with the first oblique straight line to obtain a first intersection point;

s4: lofting and unfolding the conical tube (20), equally dividing an arc boundary N of an unfolded drawing of the conical tube (20), making a third oblique straight line through a circle center o and an N equal division point of the arc boundary, cutting a bus length equal to that of the first oblique straight line on the third oblique straight line to obtain lower boundary points, and sequentially connecting the lower boundary points by using a smooth curve to obtain a lower boundary line of the lofting and unfolding drawing of the conical tube;

lofting and unfolding the cylindrical pipe (10), making a reference bus (60) through a girth intersection point in a lofting and unfolding picture of the cylindrical pipe (10), making a vertical plain line (70) through the first intersection point to intersect with the reference bus (60) to obtain second intersection points, and connecting the second intersection points in sequence by using a smooth curve to obtain an intersecting line hole opening real sample picture of the cylindrical pipe (10);

wherein, N is more than or equal to 8 and is a multiple of 4.

2. The iron outfitting pipe lofting and unfolding method according to claim 1, wherein the reference point in the S2 is an upper end surface center point of the conical pipe (20).

3. The iron outfitting pipe lofting and unfolding method according to claim 2, wherein the S2 comprises:

s21: in the front view, firstly taking the central point o' of the upper end face of the conical tube (20) as the center of a circle and the radius length of the upper end face as the radius to make a first reference circle (30), then carrying out N equal division on the first reference circle (30), wherein the N equal division points are 1, 2 … …, N-1 and N in sequence, then extending two generatrixes of the conical tube (20) to obtain the vertex o of the conical tube (20), and finally connecting the vertex o of the conical tube (20) with the N equal division points one by one to make N first oblique straight lines;

s22: in the side view, a second reference circle (40) is made by taking the center point o' of the upper end face of the conical tube (20) as the center of a circle and the radius length of the upper end face as the radius, then the second reference circle (40) is divided into N equal parts, the N equal parts are sequentially 1, 2 … …, N-1 and N, then two generatrixes of the conical tube (20) are extended to obtain the vertex o of the conical tube (20), and finally the vertex o and the N equal parts of the conical tube (20) are connected one by one to form N second inclined straight lines and are intersected with the cylindrical tube (10) to obtain a girth intersection point.

4. The iron outfitting pipe lofting and unfolding method according to claim 3, wherein the N equal division points comprise two end points of the upper end surface of the conical pipe (20).

5. The iron outfitting pipe lofting and unfolding method according to claim 1, wherein the S4 comprises:

s41: in the main view, firstly taking the vertex o of the conical tube (20) as the center of a circle, lofting and unfolding the conical tube (20) along a neutralization axis, then carrying out N equal division on the upper arc boundary of the unfolded drawing of the conical tube (20), wherein the N equal division points are 1, 2 … …, N-1 and N, then connecting the vertex o and the N equal division points of the conical tube (20) one by one to form N third inclined straight lines, finally cutting out the bus length which is equal to that of the first inclined straight line on the third inclined straight line to obtain N lower boundary points, and sequentially connecting the lower boundary points by using a smooth curve to obtain the lower boundary line of the lofting and unfolding drawing of the conical tube.

6. The iron outfitting pipe lofting and unfolding method according to claim 5, wherein the S4 further comprises:

s42: in the front view, the cylindrical pipe (10) is firstly lofted and unfolded, the arc length between two adjacent girth intersection points is measured in the side view, then the position of each girth intersection point is determined in the lofting and unfolding image of the cylindrical pipe (10), a reference bus (60) of each girth intersection point is made, finally, a vertical plain line (70) is made to intersect with the reference bus (60) in a one-to-one correspondence mode through the first intersecting point, N second intersecting points are obtained, and the second intersecting points are sequentially connected through a smooth curve to obtain an intersecting line hole opening real image of the cylindrical pipe (10).

7. The iron outfitting pipe lofting and unfolding method according to claim 6, wherein the envelope length unfolding formula of the cylindrical pipe (10) and the conical pipe (20) is L ═ pi × (d-t), L is the end face envelope length of the cylindrical pipe (10) and the conical pipe (20), d is the end face outer diameter, and t is the pipe wall thickness.

8. The iron outfitting lofting and unfolding method according to any one of claims 1 to 7, wherein N-12.

9. The iron outfitting pipe lofting deployment method according to claim 8, wherein the projection accuracy of the horizontal plain line (50) and the vertical plain line (70) is ± 0.1mm, the girth accuracy is ± 0.3mm, and the circle bisector accuracy is ± 0.1 mm.

Technical Field

The invention relates to the technical field of ship pipeline connection, in particular to a lofting and unfolding method for an iron outfitting pipe.

Background

In the ship building process, a large amount of pipe systems and connecting fittings which run through the internal structure of the ship body need to be precisely butted through iron outfitting pipes, so that the pipe system structure is more precise, the field repair and replacement are reduced, and the assembling and welding operation of pipe system butt joint is facilitated when a large-scale block is folded. Due to the fact that the types, specifications and sizes of the internal pipe systems of the ships are different, high precision requirements are required for design and layout of the iron outfitting pipes, but the precision of the existing operation method is low, so that precision dislocation phenomenon exists in on-site assembly and connection of the iron outfitting pipes, a large amount of repair operation is caused, the shipbuilding production efficiency is low, and the development of the ship construction technology is restricted.

Disclosure of Invention

In view of the above, the present invention aims to provide a lofting and unfolding method for an iron outfitting pipe, so as to solve the technical problem that the prior lofting and unfolding precision of the iron outfitting pipe is insufficient.

The technical scheme adopted by the invention is as follows: an iron outfitting pipe lofting and unfolding method, wherein the iron outfitting pipe comprises a cylindrical pipe and a conical pipe which are connected in series, and the method comprises the following steps:

s1: acquiring a front view and a side view of the through connection of the cylindrical pipe and the conical pipe;

s2: in the main view, a first reference circle is made by taking a reference point on the central line of the conical pipe as the center of a circle and the horizontal distance from the reference point to the generatrix of the conical pipe as the radius, the first reference circle is equally divided into N parts, and a first oblique straight line is made by passing through the vertex o and the equal division point of N parts of the conical pipe;

in the side view, a reference point on the central line of the conical pipe is taken as a circle center, the horizontal distance between the reference point and the generatrix of the conical pipe is taken as a radius to form a second reference circle, the second reference circle is equally divided into N parts, a second oblique straight line is formed through the vertex o of the conical pipe and the equal division point of the N parts, and the second oblique straight line is intersected with the cylindrical pipe to obtain a girth intersection point;

s3: crossing the girth intersection point to form a horizontal plain line and intersecting the horizontal plain line with the first oblique straight line to obtain a first intersection point;

s4: lofting and unfolding the conical tube, equally dividing the circular arc boundary N of the conical tube unfolding diagram, making a third oblique straight line through the circle center o and the equal division point N of the upper circular arc boundary, cutting a bus length equal to that of the first oblique straight line on the third oblique straight line to obtain lower boundary points, and sequentially connecting the lower boundary points by using a smooth curve to obtain a lower boundary line of the conical tube lofting and unfolding diagram;

lofting and unfolding the cylindrical pipe, making a reference bus through a girth intersection point in a lofting and unfolding picture of the cylindrical pipe, making a vertical plain line through the first intersection point to intersect with the reference bus to obtain second intersection points, and connecting the second intersection points in sequence by using a smooth curve to obtain a intersecting line perforated real sample picture of the cylindrical pipe;

wherein, N is more than or equal to 8 and is a multiple of 4.

Preferably, the reference point in S2 is the center point of the upper end surface of the conical tube.

Preferably, the S2 includes:

s21: in the main view, firstly taking the central point o' of the upper end face of the conical tube as the circle center and the radius length of the upper end face as the radius to make a first reference circle, then carrying out N equal division on the first reference circle, wherein the N equal division points are 1, 2 … …, N-1 and N in sequence, then extending two generatrixes of the conical tube to obtain the vertex o of the conical tube, and finally connecting the vertex o of the conical tube with the N equal division points one by one to make N first oblique straight lines;

s22: in the side view, firstly, taking the central point o' of the upper end face of the conical tube as the center of a circle and the radius length of the upper end face as the radius to form a second reference circle, then carrying out N equal division on the second reference circle, wherein the N equal division points are 1, 2 … …, N-1 and N in sequence, then extending two generatrixes of the conical tube to obtain the vertex o of the conical tube, and finally connecting the vertex o and the N equal division points of the conical tube one by one to form N second oblique straight lines which are intersected with the cylindrical tube to obtain a girth intersection point.

Preferably, the N equal division points comprise two end points of the upper end surface of the conical pipe.

Preferably, the S4 includes:

s41: in the main view, firstly taking the vertex o of the conical tube as the center of a circle, lofting and unfolding the conical tube along a neutralization axis, then carrying out N equal division on the upper arc boundary of the conical tube unfolding graph, wherein the N equal division points are 1, 2 … …, N-1 and N, then connecting the vertex o and the N equal division points of the conical tube one by one to form N third inclined straight lines, finally intercepting the bus length equal to that of the first inclined straight line on the third inclined straight line to obtain N lower boundary points, and connecting the lower boundary points in sequence by using a smooth curve to obtain the lower boundary line of the conical tube lofting and unfolding graph.

Preferably, the S4 further includes:

s42: in the main view, the cylindrical pipe is firstly lofted and unfolded, the arc length between two adjacent girth intersection points is measured in the side view, then the position of each girth intersection point is determined in the lofting and unfolding image of the cylindrical pipe, a reference bus passing through the girth intersection point is made, finally a vertical plain line passing through the first intersecting point is made to be intersected with the reference bus in a one-to-one correspondence mode, N second intersecting points are obtained, and the second intersecting points are sequentially connected through a smooth curve to obtain an intersecting line hole opening solid image of the cylindrical pipe.

Preferably, the expansion formula of the girth of the cylindrical pipe and the conical pipe is L ═ pi (d-t), L is the girth of the end face of the cylindrical pipe and the conical pipe, d is the outer diameter of the end face, and t is the wall thickness of the pipe wall.

Preferably, N is 12.

Preferably, the projection precision of the horizontal prime line and the vertical prime line is +/-0.1 mm, the precision of the girth is +/-0.3 mm, and the precision of the circle bisection is +/-0.1 mm.

The invention has the beneficial effects that:

according to the method, the intersecting line of the conical pipe and the cylindrical pipe is obtained by matching the plain line method in a mode of equally dividing the reference circles in the front view and the side view of the conical pipe, and then the lower boundary of the conical pipe lofting development diagram and the intersecting line hole opening real sample diagram of the cylindrical pipe lofting development diagram are obtained by the plain line method, so that the lofting development precision of the iron outfitting pipe is improved, and the connection precision of the conical pipe and the cylindrical pipe is ensured.

Drawings

FIG. 1 is a front view of a tubular cylindrical and conical tubular connection of the present invention;

FIG. 2 is a side view of a tubular cylindrical and conical tubular connection of the present invention;

FIG. 3 is a schematic view of the cylindrical tube and conical tube intersection line acquisition of the present invention;

FIG. 4 is one of the partial schematic views of FIG. 3;

FIG. 5 is a second partial schematic view of FIG. 3;

FIG. 6 is a drawing of a conical tube lofting deployment process;

FIG. 7 is a lofted expanded view of a tapered tube;

FIG. 8 is a schematic view of the process of lofting and unfolding a cylindrical tube;

fig. 9 is a cylindrical tube lofting deployment view.

The reference numbers in the figures illustrate:

10-a cylindrical tube;

20-a conical tube;

30-a first reference circle;

40-a second reference circle;

50-horizontal plain line;

60-reference bus;

70-vertical plain lines;

80-circular arc element line.

Detailed Description

The following describes embodiments of the present invention in further detail with reference to the accompanying drawings. These embodiments are merely illustrative of the present invention and are not intended to limit the present invention.

In the description of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In addition, in the description of the present invention, "a plurality" means two or more unless otherwise specified.

Example, as shown in fig. 1 to 9, a lofting and unfolding method for an iron outfitting pipe, which includes a cylindrical pipe 10 and a conical pipe 20 connected in series, includes:

s1: as shown in fig. 1 and 2, a front view and a side view of the tubular column 10 and the conical tube 20 are obtained;

s2: as shown in fig. 4, in the front view, a first reference circle 30 is made by taking a reference point on the center line of the conical tube 20 as the center of a circle and the horizontal distance from the reference point to the generatrix of one side of the conical tube 20 as the radius, the first reference circle 30 is divided into N equal parts, and a first oblique straight line is made by passing through the vertex o and the N equal parts of the conical tube 20;

as shown in fig. 5, in a side view, a reference point on the center line of the conical tube 20 is taken as a center of a circle, a horizontal distance from the reference point to a generatrix on one side of the conical tube 20 is taken as a radius to form a second reference circle 40, the second reference circle 40 is divided into N equal parts, a second oblique line is formed by passing through a vertex o and an N equal division point of the conical tube 20, and the second oblique line intersects with the cylindrical tube 10 to obtain a girth intersection point;

s3: as shown in fig. 3, the crossing girth intersection point is used as a first intersection point where the horizontal plain line 50 intersects with the first oblique straight line;

s4: as shown in fig. 6 and 7, lofting and unfolding the conical tube 20, equally dividing the arc boundary N of the unfolded drawing of the conical tube 20, making a third oblique straight line through the circle center o and the equally divided point N of the arc boundary, cutting a bus length equal to that of the first oblique straight line on the third oblique straight line to obtain lower boundary points, and sequentially connecting the lower boundary points by using a smooth curve to obtain a lower boundary line of the lofting and unfolding drawing of the conical tube;

as shown in fig. 8 and 9, lofting and unfolding the cylindrical tube 10, making a reference bus 60 of a surrounding long intersection point in the lofting and unfolding image of the cylindrical tube 10, making a vertical plain line 70 at a first intersecting point to be correspondingly intersected with the reference bus 60 to obtain second intersecting points, and sequentially connecting the second intersecting points by using a smooth curve to obtain an intersecting line hole opening real image of the cylindrical tube 10;

wherein, N is more than or equal to 8 and is a multiple of 4.

According to the method, firstly, the mode of making the first reference circle 30 and the second reference circle 40 which are equally divided into N parts in the front view and the side view of the conical pipe 20 is matched with the plain line method to obtain the intersecting line of the conical pipe 20 and the cylindrical pipe 10, and then the lower boundary of the conical pipe lofting expansion diagram and the intersecting line hole opening real sample diagram of the cylindrical pipe lofting expansion diagram are obtained through the plain line method, so that the lofting expansion precision of the iron outfitting pipe is improved, and the connection precision of the conical pipe 20 and the cylindrical pipe 10 is ensured.

In the present embodiment, an example in which N is 12 and the center point o' of the upper end surface of the tapered tube 20 is used as a reference point will be described in detail. As shown in fig. 1 to 9, a method for lofting and unfolding an iron outfitting pipe, which includes a cylindrical pipe 10 and a conical pipe 20 connected in series, includes:

s1: as shown in fig. 1 and 2, according to the technical requirements of designing and manufacturing ship fittings, a front view and a side view of the external contour of a tubular column 10 and a conical tube 20 are obtained.

S21: as shown in fig. 4, in a front view, a center point o 'of an upper end surface of the tapered tube 20 (the upper end surface of the tapered tube 20 refers to an upper nozzle of the tapered tube 20) is taken as a center point, left and right end points of the upper end surface of the tapered tube 20 are 4 and 10, then the radius of 4 o' is taken as a radius (the radius is a radius of the nozzle of the tapered tube 20), a first reference circle 30 is made, the first reference circle 30 is divided into 12 equal parts, the 12 equal parts include the left and right end points 4 and 10 of the upper end surface of the tapered tube 20 in the front view, specifically, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 and 12 which are sequentially arranged, then two generatrices of the tapered tube 20 are extended to obtain an apex o of the tapered tube 20, and finally, the apex o of the tapered tube 20 is correspondingly connected with the 12 equal parts one-to-one, so as to-obtain 12 first oblique straight lines (dashed lines in the order of o1, o2, o3, o4, o5, o6, o7, o8, o1, o3, o8, o3, o 84, o3, 2, and o3, 2, and 12, 2, o9, o10, o11, o 12.

S22: as shown in fig. 5, in a side view, a center point o 'of an upper end surface of the tapered tube 20 is taken as a center, left and right end points of the upper end surface of the tapered tube 20 are 1 and 7, then a second reference circle 40 is made with 7 o' as a radius, then the second reference circle 40 is divided into 12 equal divisions, the 12 equal divisions include the left and right end points 1 and 7, 12 equal divisions of the upper end surface of the tapered tube 20 in the side view, which are sequentially 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 and 12, then two generatrixes of the tapered tube 20 are extended to obtain a vertex o of the tapered tube 20, and finally the vertex o and the 12 equal divisions of the tapered tube 20 are connected in a one-to-one correspondence manner to obtain 12 second oblique straight lines (dashed lines in the figure), which are sequentially o1, o2, o3, o4, o5, o6, o7, o8, o9, o10, o11, o 12; the second oblique line intersects the cylindrical tube 10 to obtain 12 girth intersections.

The nomenclature of 12 bisectors in S21 is kept the same as the nomenclature of 12 bisectors in S22, that is, bisector 4 in S21 is the same bisector 4 in S22.

S3: as shown in fig. 3, 12 circle-length intersection points in the cross-sectional view are taken as horizontal plain lines 50 and are intersected with the first oblique straight lines in the front view one by one to obtain 12 first intersecting points, and the first intersecting points are sequentially connected by a smooth curve to obtain intersecting lines of the conical tube 20 and the cylindrical tube 10.

S41: as shown in fig. 6 and 7, in the front view, the vertex o of the conical tube 20 is taken as the center of a circle, and the conical tube 20 is lofted and expanded into a sector along the neutral axis, wherein the lofting and expanding formula is L ═ pi (d-t), L is the lower nozzle circumference of the conical tube 20, d is the outer diameter of the lower end face, t is the wall thickness of the tube wall, and pi is the circumferential ratio; the neutral axis refers to the conical surface at the center of the wall thickness of the tapered tube 20. Dividing 12 equal divisions of an upper arc boundary or a lower arc boundary of a development drawing of the conical tube 20, wherein 12 equal divisions are 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 and 12 respectively; and then, connecting the vertexes o and 12 of the conical tube 20 in an equal-division manner one by one to obtain 12 third inclined straight lines which are o1, o2, o3, o4, o5, o6, o7, o8, o9, o10, o11 and o12 in sequence. Taking the vertex o of the conical tube 20 as the center of a circle and the generatrix length on the first oblique straight line as the radius, making an arc prime line 80 to intercept the generatrix length equal to that on the first oblique straight line on the third oblique straight line, and obtaining 12 lower boundary points, namely, the length of the line segment between the vertex o and the lower boundary point of the conical tube 20 in the expanded view is equal to the length of the line segment between the vertex o and the first intersecting point of the conical tube 20 in the main view. And finally, connecting the lower boundary points in sequence by using a smooth curve to obtain the lower boundary line of the conical tube lofting development drawing and obtain the complete conical tube lofting development drawing.

S42: as shown in fig. 8 and 9, in the front view, the cylindrical tube 10 is lofted and expanded into a rectangle, where the lofting and expanding formula is L ═ pi (d-t), L is the nozzle girth of the cylindrical tube 10, d is the nozzle outer diameter, t is the wall thickness of the tube wall, and pi is the circumferential ratio; the neutralization axis refers to the circumferential surface of the cylindrical tube 10 at the center of the wall thickness. Taking the bisector points 4 and 10 as central points, the girth of two adjacent girth intersection elements in the side view is adjusted to the cylindrical pipe 10 lofting development figure, the positions of the bisector points 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 and 12 in the cylindrical pipe 10 lofting development figure are obtained, and then a reference bus 60 (a dotted line in the figure) passing through the bisector points 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 and 12 is made. The first intersecting points are crossed with 12 vertical plain lines 70 and the reference bus 60 in a one-to-one correspondence mode to obtain 12 second intersecting points, and the second intersecting points are connected in sequence through a smooth curve to obtain an intersecting line open hole sample drawing of the cylindrical pipe 10.

Determining a three-dimensional view of the through connection of the conical tube 20 and the cylindrical tube 10, wherein the cylindrical tube 10 needs to be provided with a plurality of open holes during plate cutting and blanking, and when the conical tube 20 and the cylindrical tube 10 are spliced and assembled, the intersecting line area is welded by adopting nodes in an angle joint form to complete the product manufacturing.

Lofting and unfolding accuracy standard: the projection precision of the horizontal element line 50 and the vertical element line 70 is +/-0.1 mm, the girth adjusting precision is +/-0.3 mm, the circle bisection precision is +/-0.1 mm, and the lofting expansion girth precision is +/-0.3 mm.

Compared with the prior art, the application has at least the following beneficial technical effects:

the application provides a design, lofting and unfolding method for an iron outfitting pipe, which is used for realizing accurate connection of a conical pipe and a cylindrical pipe by designing, lofting and unfolding the iron outfitting pipe of a ship accessory. The method relates to the operation of a prime line projection, an expansion girth formula, the determination of the shape of an intersecting line and the expansion of the shape of the intersecting line into a hole-opening sample graph in circle bisection and three-side projection, and completes the innovation and the practicability of the whole production and construction process technology from the angle of design, lofting and expansion, thereby promoting the improvement of the production efficiency.

The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and substitutions can be made without departing from the technical principle of the present invention, and these modifications and substitutions should also be regarded as the protection scope of the present invention.