CN106204736B - Unfolding lofting manufacturing method of three-dimensional surface triangle unfolding method - Google Patents
Unfolding lofting manufacturing method of three-dimensional surface triangle unfolding method Download PDFInfo
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- CN106204736B CN106204736B CN201610113012.4A CN201610113012A CN106204736B CN 106204736 B CN106204736 B CN 106204736B CN 201610113012 A CN201610113012 A CN 201610113012A CN 106204736 B CN106204736 B CN 106204736B
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Abstract
The invention relates to a three-dimensional surface unfolding lofting manufacturing method, in particular to a three-dimensional surface unfolding lofting manufacturing method by using AutoCAD software. The method comprises the following steps: respectively creating a three-dimensional solid model and a three-dimensional wire frame model of a three-dimensional surface by using AutoCAD according to a ratio of 1: 1; dividing the circumferences of upper and lower bottom surface curves/line segments of the three-dimensional wireframe model equally, connecting equal division points of the circumferences in sequence and counting the length; comparing the three-dimensional solid model with the three-dimensional wire frame model; sequentially drawing the line segments in the three-dimensional line frame model in a two-dimensional plane, and marking the sizes of all the line segments; guiding the three-dimensional side development image into a numerical control machine tool for cutting operation, or drawing a large sample according to the equal proportion of the development image 1:1 and manually cutting the large sample; and rolling the cut steel plates and then welding the rolled steel plates. The method can replace the three existing expansion lofting methods, does not need to use the traditional triangle expansion method to calculate and solve the real length of each side of each triangle, and expands the area range which is not suitable for the three traditional expansion lofting methods.
Description
Technical Field
The invention relates to a three-dimensional surface unfolding lofting manufacturing method. In particular to a method for making a three-dimensional surface unfolding lofting by using 'AutoCAD two/three-dimensional drawing', 'triangle unfolding method', 'space vector and solid geometry', 'definite integral', 'numerical control cutting' (optional).
Background
At present, the three-dimensional surface unfolding lofting is performed by adopting the following method:
in the traditional unfolding lofting, limited by the current lofting drawing environmental conditions, the self knowledge reserve of lofting personnel and the prior lofting method, the unfolding lofting method of the three-dimensional surface is usually adopted: the three methods are used for unfolding and lofting the three-dimensional surface, namely converting a three-dimensional real object into three-dimensional plane projection processing and unfolding (namely converting three-dimensional stereo into two-dimensional plane graph), and for the irregular three-dimensional surface, the lofting process is complex, the required data calculation is complex, errors are easy to make, and the correctness is not easy to check before assembling and forming.
A parallel line expansion method: the unfolding principle is that the surface of the solid is regarded as a plurality of parallel plain lines, the tiny area enclosed by two adjacent plain lines and two end points thereof is taken as a plane, and the unfolding picture of the surface of the solid is obtained as long as the real size of each facet is sequentially drawn on the plane.
Radiation expansion method: the expansion principle is that the cone surface is divided into a plurality of triangular small planes with the same top by using emission lines, after the actual size is obtained, the small planes are still sequentially marked on the same plane in a radioactive ray mode, and the expansion image of the cone surface is obtained. The ray method is suitable for a cone with a point intersected by a prime line of a three-dimensional surface.
A triangle expansion method: the expansion principle is that the solid surface is divided into a certain number of triangular planes, then the real length of each side of each triangle is obtained, and the real shape of each triangle is sequentially drawn on the planes, so that the expansion diagram of the whole solid surface is obtained. The triangle expansion method is suitable for the parallel line expansion method, the radioactive ray expansion method and other solid geometrical shapes which are not suitable for the first two expansion methods.
The traditional method of the three methods adopts a general three-dimensional three-view projection rule that the main depression length is aligned, the main left height is flush, and the depression left width is equal to describe the unfolding lofting, and uses a two-dimensional plane graph to describe the three-dimensional solid, but the three-dimensional solid with the solid surface geometry of non-linear edges and non-circular edges is obviously limited by the fact that the projection rule cannot accurately, simply and efficiently describe and draw.
After the three methods are used for unfolding the three-dimensional surface, a larger space error exists between the unfolded shape of the three-dimensional surface and the actual shape, and practice proves that the larger the geometric size of the three-dimensional surface is, the more the geometric shape is complex, and the larger the generated space position error is.
Disclosure of Invention
The invention aims to fill the area range which is not suitable for the three traditional unfolding lofting methods, and provides a set of novel three-dimensional surface unfolding lofting manufacturing method which is simple, clear, accurate in processing, safe, reliable, easy to learn and easy to meet by combining the existing technical means with the theory of forming a highly optimized, unified and effective novel unfolding method of the three traditional lofting methods.
The technical scheme adopted by the invention for solving the problems is as follows:
the invention relates to a new method for making an unfolding lofting of a three-dimensional surface triangular unfolding method, which comprises the following steps (taking the simple unfolding lofting of the side surface of an elliptic cone frustum with parallel upper and lower bottom surfaces as an example):
1. establishing an upper elliptical round bottom and a lower elliptical round bottom of an elliptical frustum body in an XYZ coordinate system in a UCS (unified description system) world coordinate system of the three-dimensional modeling working space according to the geometric dimension requirement of a ratio of 1:1 by using an AutoCAD (automatic computer aided design) E LL IPSE (Internet protocol Security) elliptical command in the three-dimensional modeling working space, and establishing a three-dimensional entity model of the elliptical frustum body by using a L OFT (open field test) lofting command;
2. establishing an upper elliptical round bottom and a lower elliptical round bottom of an elliptical frustum body in an XYZ coordinate system in a UCS (unified cooling system) world coordinate system of the three-dimensional modeling working space according to geometric dimension requirements of a ratio of 1:1 by using an AutoCAD (automatic computer aided design) E LL IPSE (Internet protocol Security) ellipse command in the AutoCAD, and respectively connecting four quadrant points of the upper elliptical round bottom and the lower elliptical round bottom by using a L INE straight line command, so as to form an elliptical frustum body three-dimensional wire frame model consisting of the upper elliptical bottom, the lower elliptical bottom and connecting lines of the quadrant points;
3. equally dividing the circumferences of an upper elliptical bottom and a lower elliptical bottom of the elliptical frustum three-dimensional wire frame model into the same number of parts by using a DIV (digital image converter) constant number equal division command (since the figure limit points are used for convenient positioning, all the parts are generally integral multiples of 4, and the points can be equally divided by using alphanumeric marks), and selecting a point sample type convenient for observation by using a point pattern command;
4. drawing elliptical frustum body element lines on the circumference equal points of the upper elliptical bottom and the lower elliptical bottom of the elliptical frustum body three-dimensional line frame model according to a one-to-one correspondence relationship;
5. the circumference equal points of the upper ellipse bottom and the lower ellipse bottom of the three-dimensional wire frame model of the elliptical frustum body are staggered by one equal point and then are connected according to a one-to-one correspondence relationship, so that a plurality of sequentially adjacent space triangles (similar to the traditional 'triangle expansion method') formed by the element line, the circumference equal point connecting line (chord length) of the upper ellipse bottom, the circumference equal point connecting line (chord length) of the lower ellipse bottom and the staggered point connecting line of the circumference equal point of the upper ellipse bottom and the circumference equal point of the lower ellipse bottom are formed, and the space positioning of the end points of each space triangle line segment in the three-dimensional wire;
6. superposing the three-dimensional solid model of the elliptical frustum body created by the L OFT lofting command with respective reference points of the three-dimensional wire frame model of the elliptical frustum body formed in the step 5, visually detecting the spatial position deviation of each line segment in the three-dimensional wire frame model of the elliptical frustum body and the three-dimensional solid model of the elliptical frustum body, and repeating the steps 3 to 6 by using more equant points if the spatial position deviation does not meet the requirement;
7. after the spatial position deviation of each line segment in the three-dimensional wire frame model of the elliptical frustum body meets the requirement, sequentially counting the length of the line segments in all the three-dimensional wire frame models of the elliptical frustum body by using L IST 'list display' command (or other modes);
8. three line segments (respectively using arc lengths of elliptic arcs between equal points of the circumferences of an upper ellipse and a lower ellipse) of each space triangle in the three-dimensional line frame model of the elliptic frustum body to replace chord lengths) are sequentially drawn into triangles according to corresponding lengths on a two-dimensional plane (unfolded according to a traditional triangle unfolding method);
9. using an SP L INE 'spline' command to sequentially and respectively connect the segment endpoints of the arc length of the elliptic arc on each side in the side development graph of the elliptic cone body on the two-dimensional plane;
10. marking the sizes of all line segments in the development graph on the side surface of the elliptic cone body respectively (the line segments of the arc length of the elliptic arc on each side can be marked in a group respectively), and selecting the line segments of part of special position points as reserved rolling alignment lines to realize the effects of manually drawing a large sample on a plate material in a ratio of 1:1 and rolling, correcting and aligning;
11. and at this moment, the side surface of the elliptic cone is unfolded and lofted. The cutting tool can be directly led into a numerical control machine tool to carry out automatic cutting operation, and also can be used for drawing a large sample on a plate according to the proportion of the marked dimension 1:1 of an expansion drawing and carrying out manual cutting operation;
12. and (3) rolling the cut plate according to the positioning inspection requirement of the reserved rolling alignment line, and then correcting welding according to the reserved rolling alignment line group to finish the surface unfolding lofting and manufacturing operation of the elliptical cone table body.
Description of the drawings:
FIG. 1 is a top view and a side view of the three-dimensional solid model of the elliptical frustum with parallel upper and lower bottom surfaces in step a.
Fig. 2 is a top view and a side view of the three-dimensional wire frame model of the elliptical frustum with the upper and lower bottom surfaces parallel to each other in step a.
Fig. 3 is a top view and a side view of each line of the three-dimensional wire frame model of the elliptical frustum with the upper and lower bottom surfaces parallel to each other in steps c, d, and e.
Fig. 4 is a comparison diagram of the three-dimensional solid model surface and the three-dimensional wire frame model of the elliptical frustum body with the upper and lower bottom surfaces parallel in step g.
Fig. 5 is a top view and a side view of the three-dimensional wire frame model of the side surface of the elliptical frustum body with the upper and lower bottom surfaces parallel to each other in steps e, f and h.
The specific implementation method comprises the following steps:
the invention is described in detail below with reference to the accompanying drawings and examples.
With reference to the attached drawings, the unfolding lofting and making novel invention method of the stereoscopic surface triangle unfolding method is implemented according to the following steps:
1. as shown in fig. 1, according to the specific geometric parameters of the elliptical frustum to be expanded, an AutoCAD is used to build a body model in a three-dimensional space. As shown in fig. 2, a simple three-dimensional wire frame model is built in a three-dimensional coordinate space;
2. the perimeter of the upper elliptical bottom and the perimeter of the lower elliptical bottom of the three-dimensional wire frame model of the elliptical frustum body are equally divided (DIV commands), the number of the equally divided perimeters is required to be as large as possible, the concept of 'straight curve instead of curve' in 'fixed integral' is realized (the total perimeter of the upper elliptical bottom and the lower elliptical bottom is ensured to be unchanged, the phenomenon of 'distortion' of a final expanded graph is caused by too few equally divided perimeters, the more equally divided perimeters are, the more vivid the final expanded graph is, and the greater the expansion complexity is), the 'point style' command is set to display equally divided points, the equally divided points of the perimeters of the upper elliptical bottom and the lower elliptical bottom of the three-dimensional wire frame model of the elliptical frustum body are respectively connected by line segments, and the length of each line segment is counted.
3. As shown in fig. 3, the reference points of the three-dimensional model and the three-dimensional wire frame model are superimposed, and the coincidence relation between the positions of the line segments on the three-dimensional wire frame model and the three-dimensional model is observed. If the anastomosis is better, the deployment can be continued; otherwise, returning to the above step, and reselecting the equant points.
4. According to the length of each line segment counted, each line segment in the three-dimensional line frame model of the elliptical frustum is sequentially drawn in a two-dimensional plane according to the unfolding drawing method of the traditional triangle unfolding method, and after all the line segments are drawn, the equant points of the ellipses on the upper bottom and the lower bottom of the elliptical frustum unfolded in the two-dimensional plane are sequentially connected by using a spline curve so as to form a smoothly-transitional outer contour (note that the mutual positions of all positioning points of the outer contour of the unfolding diagram are sequentially and gradually increased or decreased for smooth transition, and the mutual positions of all the positioning points are severely fluctuated, so that errors can occur).
5. The lengths of all line segments of the side development image of the elliptical cone are respectively marked with dimensions, and a part of reserved rolling alignment lines are selected from the line segments, so that 1:1 large drawing and rolling correction alignment inspection on a plate can be manually realized, and the requirements of different elliptical arc radiuses of the elliptical cone are adjusted.
6. The side surface development figure of the elliptic cone frustum can be led into a numerical control machine tool control system for automatic cutting operation, and a large sample can be drawn on a plate according to the equal proportion of the marked dimension 1:1 of the development figure for manual cutting operation.
7. And rolling the cut plate in a segmented and graded manner according to a preset positioning line. And after the correction, the steel plates are butt-welded, and the surface of the elliptic cone is unfolded, lofted and manufactured.
Claims (1)
1. An unfolding lofting manufacturing method of a three-dimensional surface triangle unfolding method is characterized by comprising the following steps:
a. establishing an upper elliptical round bottom and a lower elliptical round bottom of an elliptical frustum body in an XYZ coordinate system in a UCS (unified description system) world coordinate system of the three-dimensional modeling working space according to the geometric dimension requirement of a ratio of 1:1 by using an AutoCAD (automatic computer aided design) E LL IPSE (Internet protocol Security) elliptical command in the three-dimensional modeling working space, and establishing a three-dimensional entity model of the elliptical frustum body by using a L OFT (open field test) lofting command;
b. establishing an upper elliptical round bottom and a lower elliptical round bottom of an elliptical frustum body in an XYZ coordinate system in a UCS (unified cooling system) world coordinate system of the three-dimensional modeling working space according to geometric dimension requirements of a ratio of 1:1 by using an AutoCAD (automatic computer aided design) E LL IPSE (Internet protocol Security) ellipse command in the AutoCAD, and respectively connecting four quadrant points of the upper elliptical round bottom and the lower elliptical round bottom by using a L INE straight line command, so as to form an elliptical frustum body three-dimensional wire frame model consisting of the upper elliptical bottom, the lower elliptical bottom and connecting lines of the quadrant points;
c. equally dividing the circumferences of the upper elliptical bottom and the lower elliptical bottom of the elliptical frustum three-dimensional line frame model into the same number of parts by using a DIV constant number equal division command, and selecting a point sample type convenient to observe by using a point pattern command;
d. drawing elliptical frustum body element lines on the circumference equal points of the upper elliptical bottom and the lower elliptical bottom of the elliptical frustum body three-dimensional line frame model according to a one-to-one correspondence relationship;
e. the circumference equal points of the upper ellipse bottom and the lower ellipse bottom of the three-dimensional wire frame model of the elliptical frustum body are staggered by equal points and then connected according to a one-to-one correspondence relationship, so that a plurality of sequentially adjacent space triangles formed by element lines, the circumference equal points of the upper ellipse bottom, the circumference equal points of the lower ellipse bottom, and the staggered point lines of the circumference equal points of the upper ellipse bottom and the lower ellipse bottom are formed, and the space positioning of the segment end points of each space triangle in the three-dimensional wire frame model of the elliptical frustum body is realized;
f. superposing the three-dimensional solid model of the elliptical frustum body created by the L OFT lofting command with respective reference points of the three-dimensional wire frame model of the elliptical frustum body formed in the step e, visually detecting the spatial position deviation of each line segment in the three-dimensional wire frame model of the elliptical frustum body and the three-dimensional solid model of the elliptical frustum body, and repeating the steps c to f by using more equant points if the spatial position deviation does not meet the requirement;
g. after the spatial position deviation of each line segment in the three-dimensional wire frame model of the elliptical frustum body meets the requirement, sequentially counting the lengths of the line segments in all the three-dimensional wire frame models of the elliptical frustum body by using an L IST 'list display' command;
h. three line segments of each space triangle in the three-dimensional line frame model of the elliptical frustum body are respectively replaced by arc lengths of elliptical arcs between equal points of the circumferences of an upper ellipse and a lower ellipse, and triangles are sequentially drawn on a two-dimensional plane according to the corresponding lengths of the three line segments;
i. using an SP L INE 'spline' command to sequentially and respectively connect the segment endpoints of the arc length of the elliptic arc on each side in the side development graph of the elliptic cone body on the two-dimensional plane;
j. marking the sizes of all line segments in an expanded view on the side surface of the elliptic cone body respectively, marking a group of line segments of the arc length of an elliptic arc on each side, and selecting line segments of part of special position points as reserved rolling alignment lines to realize the effects of manually drawing a large sample on a plate material in a ratio of 1:1 and rolling, correcting and aligning;
k. at this moment, the side surface of the elliptic cone frustum is unfolded and lofted, and the side surface is directly led into a numerical control machine tool to carry out automatic cutting operation or large samples are drawn on the plate according to the proportion of the dimension 1:1 marked by an unfolded drawing, and manual cutting operation is carried out;
and l, rolling the cut plate according to the positioning inspection requirement of the reserved rolling alignment line, and then correcting welding according to the reserved rolling alignment line group to finish the surface unfolding lofting and manufacturing operation of the elliptic cone frustum.
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| CN106780763B (en) * | 2016-12-31 | 2021-09-03 | 山东世联环保科技开发有限公司 | Solid surface intersecting line section geometric figure and space broken line expansion method |
| CN108765552B (en) * | 2018-05-17 | 2022-05-10 | 中船黄埔文冲船舶有限公司 | Unfolding method of runner transition plate |
| CN109829254B (en) * | 2019-03-19 | 2022-05-06 | 中国十九冶集团有限公司 | Method for drawing positioning line of diaphragm plate after top and bottom plates of curved steel box bridge are unfolded |
| CN112848363A (en) * | 2021-01-05 | 2021-05-28 | 北京卫星环境工程研究所 | Unfolding design method for spacecraft thermal control multilayer model |
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