A new idea of CAD lofting for the hottest round pi

2022-08-16
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New idea of CAD deployment and lofting of circular pipe elbow

introduction

circular pipe elbow refers to a rotating body elbow composed of multiple pipe joints and with bending radius. The round pipe section includes "end section" and "middle section". The end section is made of single-sided oblique cut round pipe, and the middle section is made of double-sided oblique cut round pipe. The unfolding lofting of circular elbow plays an important role in the field of sheet metal unfolding lofting. According to relevant specifications, if the included angle of the end section of the round pipe elbow is half of the included angle of the middle section, this kind of elbow is called "standard section angle elbow". The unfolding and setting out of this elbow is easy to complete with the traditional "calculation method" or "drawing method". As long as a simple end section plane unfolding diagram is completed, the plane unfolding diagram of other sections can be drawn, which is not discussed here

in practical work, there is another kind called "arbitrary section angle elbow", that is, the included angle between the end section and the middle section is arbitrary. The elbow is composed of several different end sections and middle sections, as shown in Figure 1. Because the shape of each section is different. Therefore, the plane expansion lofting of elbows requires the relevant dimensions of each section. Such elbows are lofted with the traditional "drawing method" or "calculation method", which is more complicated. Over the years, people often spend a lot of effort in the deployment and setting out of such elbows. With the continuous development of 3D CAD technology and the wide use of CAD system software, using 3D CAD technology to solve the problem of unfolding and lofting of complex sheet metal parts is the development trend in this field. Combined with my own CAD/CAM Teaching Practice and engineering design experience, the author has actively explored the application of 3D CAD in sheet metal lofting. Practice has proved that using 3D CAD to unfold and loft sheet metal parts has simple and clear steps, and the obtained data are accurate and reliable. It is a new and efficient unfolding and lofting method superior to the traditional lofting mode. Taking the complex 90 ° circular pipe elbow with arbitrary pitch angle as an example, the author expounds its unfolding and lofting process by using the three-dimensional CAD Software Solidworks. The steps are simple and clear. Readers can complete the unfolding and lofting of circular pipe elbows of various sizes and angles in practical work by referring to its process

1 round pipe elbow with any pitch angle of 90 °

Figure 1 is the stereoscopic view and projection view of round pipe elbow with any pitch angle of 90 °. Diameter of round pipe φ Therefore, the elbow radius is R300. The elbow is composed of two end sections and three intermediate sections. The included angles of the end sections are 5 ° and 10 ° respectively, and the included angles of the intermediate sections are 20 °, 25 ° and 30 ° respectively. In order to draw the plane expansion diagram of the elbow, the actual length of all five sections of the bus must be calculated, and the overall Jinan experimental machine factory Jinan new era Gold Testing Instrument Co., Ltd. has produced experimental machines for many years

Figure 1 round pipe elbow with any section angle of 90

1.1 each section of the elbow is formed by reverse arrangement φ 300 cylinder

Figure 2 shows that each section of the elbow is arranged in reverse to form a diameter of φ Cylinder view of 300. The total height of the cylinder h is calculated as follows:

Figure 2. The angle of any section is 90 °. The cylinder view of the circular pipe elbow is arranged in reverse.

h=h1+h2+h3+h4+h5=300tan5 ° +300* (tan5 ° +tan20 °) +300 (tan20 ° +tan10 °) +300 tan10 ° =482.47

2. The vertical shape of the elbow cylinder and the length of each section of the bus

according to figure 2, carry out the three-dimensional shape of the cylinder according to the following steps to calculate the length of each section of the bus

2.1 generate a three-dimensional cylinder

select "up looking datum" to draw a 2D (two-dimensional) sketch with a diameter of φ 300, "stretching boss" generates a solid cylinder with a height of 482.47, as shown in Figure 3

figure 3

2.2 generate upper and lower contour lines

according to the angle of each section, stretch and cut some entities to form the upper and lower contour lines of the end section and the middle section

1) "sketch" and "3D (3D) sketch" respectively select the upper and lower surfaces of the cylinder, and "convert solid reference" is generated φ 300 two 3D curves, as shown in Figure 4a

2) select "forward reference plane", "sketch drawing" and "straight line", and the included angle between drawing and horizontal line is 5. As shown in Figure 4b, "pull cut" removes the part below the line

3) "sketch drawing" and "3D sketch" select the oblique section and "convert entity reference" commands generated in step 2 to generate oblique section 1, as shown in Figure 4C

4) refer to step 2) and step 3) to generate oblique section 2, oblique section 3 and oblique section 4 respectively, as shown in Figure 5. The generated oblique section is the upper and lower contour of the end section and the middle section

Figure 4 Sketch Drawing

Figure 5 generate oblique section line

2.3 calculate the real length of the busbar of each section

1) select the commands of "exit sketch", "reference geometry" and "point", select 4300 column bottom circle, evenly distributed, 12 number of side lines, and generate 12 equally divided circle points, as shown in Figure 6. In China, the proportion is only 14%

2) select the commands of "sketch drawing", "3D sketch" and "centerline". Upward oblique section 1, oblique section 2, oblique section 3, oblique section 4 and cylinder top circle from each bisector φ 300 lead the vertical line to generate the busbar of the end section and the middle section, as shown in Figure 6. Because the figure is symmetrical, only 1/2 can be drawn

3) select the "rebuild model" and "smart size" commands, and measure the bus length of the end section and the bus length of the middle section at each bisection point (see Figure 6). Due to the symmetry of the figure, only the values from point 9 to point 3 are measured, and the specific values are shown in Table 1

4) select the "tools" and "measurement" commands in the main menu, and select oblique section 1, oblique section 2, oblique section 3 and oblique section 4 respectively. The measured values of the circumference of the oblique section are 944.25, 972.93, 949.47 and 949.47 respectively, which can be used as a reference for setting out

Figure 6. The bus length of each section

3 draw the plane expansion diagram of the circular pipe elbow with any section angle of 90 °

draw the plane expansion diagram of the elbow according to the data in Table 1, as shown in Figure 7. According to figure 7, any pitch angle of 90 can be carried out. The plane of each section of the circular pipe elbow is expanded and unloaded

Figure 7 plane expansion blanking figure

4 circular pipe elbow modeling deployment and setting out steps

1) according to the geometric size of the elbow, make each section arranged in reverse, and draw the three-dimensional cylindrical view of the elbow

2) according to the geometric size of the stereoscopic cylinder view, use SolidWorks solid modeling command to generate the space contour lines of each section of the elbow arranged in reverse 1:1

3) use the "point" command in "reference geometry" to divide several equal parts of the end face circumference, and use the "3D sketch" to draw the "centerline" command to draw each bus

4) exit the "3D sketch" state. Use the "smart size" command to measure the length of each bus and classify the list

of course, the fluctuation of water should be considered. 5) according to the measured actual length of each bus, draw the plane expansion graph of each section of the elbow

5 conclusion

to sum up, it can be seen that it is simple and fast to use 3D CAD SolidWorks software to carry out three-dimensional setting out of circular pipe elbows. As long as you are familiar with and master several relevant commands of the software, carry out 1:1 three-dimensional modeling of parts, form space contour lines of each section and draw several generatrixes, and then carry out "intelligent Annotation", you can accurately calculate the length of generatrix. For elbow components, regardless of their size and the included angle of each section, as long as the above steps are referred to, the results can be calculated quickly, which provides a reliable basis for plane setting out and blanking. Compared with the traditional lofting method, this method not only improves the efficiency, but also greatly improves the accuracy. Today, the application of computer-aided design 3D CAD is more and more extensive. This method is a new 3D lofting mode worthy of popularization and application. (end)

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