Discussion on 3D Solid Modeling Based on AutoCAD
With the rapid development of computer technology, 3D CAD software is becoming more and more mature, and 3D solid modeling has begun to be widely used in product or engineering design. At present, commonly used 3D modeling software mainly includes AutoCAD, Pro/Engineer, UG, Solidwork, CAXA and so on. Although the three-dimensional modeling function in the above several softwares is weak in AutoCAD, it is difficult to construct a shape with complex shape, and it is inconvenient to modify. However, for teachers or technicians with AutoCAD 2D drawing foundation, it is easy to learn, easy to master, and get started. fast. The author below combines the teaching practice of AutoCAD 3D solid modeling to talk about some experiences. 2.2.2 Setup Settings Layer Next page Here you can find the related products in Temperature Transmitter, we are professional manufacturer of Temperature Transmitter,Pneumatic Temperature Transmitter,Temperature Sensor Transmitter,Thermometer Transmitter. We focused on international export product development, production and sales. We have improved quality control processes of Temperature Transmitter to ensure each export qualified product. Temperature Transmitter,Pneumatic Temperature Transmitter,Temperature Sensor Transmitter,Thermometer Transmitter Xi'an Gavin Electronic Technology Co., Ltd , https://www.gaimcmeaso.com
Combining examples from UCS coordinate system, solid layer, multi-viewport, and entity editing to generate 3D solids from 2D graphics, the 3D solid modeling is studied and studied to improve the efficiency of 3D solid modeling.
1 3D solid model overview
The three-dimensional model includes a wireframe model, a surface model, and a solid model. The solid model includes all the information of lines, faces and bodies, and is the most advanced of the three models. It not only has physical properties such as mass and volume, but also is closer to real objects, and Boolean operations such as parallel, cross, and difference can be performed between entities to create more complex solid models and to perform blanking, coloring, and rendering. In addition, the solid model can also generate 2D plan view, section view and section view. The solid model data output by AutoCAD can also be provided to subsequent NC machining and finite element analysis.
2 AutoCAD 3D solid modeling
2.1 Modeling ideas and methods
When creating a 3D solid model, the structure of the model is first analyzed. No matter how complex the structure of the model, it is always composed of several simple entities. Therefore, the process of building a complex model is actually a process of constantly creating and combining simple entities. Of course, there may be several schemes for building complex models, and a more convenient and reasonable solution should be chosen for modeling. Then use the primitive or stretch or rotate the 2D graphics to create individual entities. Finally, each simple entity performs a Boolean operation such as merging, difference, and intersection, and various editing operations to obtain more complex entities.
2.2 Modeling skills
2.2.1 Learn to establish and manage user coordinate systems
In AutoCAD, the coordinate system is divided into two types: the world coordinate system (WCS) and the user coordinate system (ucs). The coordinate systems used in 2D drawings are mostly world coordinate systems, which are unique and unchanging. However, in the process of 3D drawing, in order to facilitate drawing and viewing graphics, in addition to WCS, the user can establish his own coordinate system--user coordinate system (ucs) according to the needs, such coordinate system its origin position and x, y, z axis Directions can be moved and rotated at will, and can even vary depending on a particular object in the drawing. Learning to build a user coordinate system will simplify the 3D modeling process and is the key to 3D modeling.
As shown in Figure 1, the three-dimensional solid model uses the world coordinate system (wcs) when drawing the cylinder A. When the cylinder B is drawn, the current coordinate system should be rotated 900 around the rub axis. When the cylinder C is drawn, the current coordinates are drawn. The system should be rotated 90 around the y-axis. When drawing the cylinder D, you should specify the face or three points to establish the UCS.
In addition, to draw complex three-dimensional graphics, due to the large number of UCSs that need to be established, in order to avoid frequent coordinate system transformation, users can pre-define and save UCS in different directions through the UCS manager, and call them whenever necessary. 
Layers are one of the most effective tools for AutoCAD organizations to manage graphical objects. By placing objects of different nature on different layers, it is easy to display and edit objects by controlling the characteristics of the layers. 3D graphics are more complex than 2D graphics and have more visual interference, so layers should be used to manage graphics. The layering of the 3D solid model can be based on the body analysis method, and the individual entity objects that make up the model are placed on different layers and distinguished by different colors for more clear mapping for subsequent coloring processing and material distribution. Convenient. When interference occurs, some entities can be invisible by closing or freezing certain layers for the positioning or selection of other entity objects. In addition, when managing three-dimensional graphics with layers, generally do not rush to perform Boolean operations on solid objects between different layers, unless the entire three-dimensional graphics have been drawn, it is not conducive to the subsequent editing work.
2.2.3 Application of multiple viewports
When drawing complex 3D graphics, you can do it directly in a 3D view, but there are often problems such as inconvenient expression and low efficiency. These problems can be solved by establishing a multi-viewport. AutoCAD allows you to divide the drawing area into multiple windows (viewports) and allows different UCS to be used in different viewports. Therefore, when drawing and observing complex 3D graphics, divide the drawing area into multiple viewports, and create or use different UCSs according to needs in each viewport, set different observation points or choose to display different views, etc. The four viewports of the two display the main view, the top view, the left view, and the isometric view of the three-dimensional graphics, so that different parts of the figure can be drawn and observed in different viewports, greatly reducing the UCS coordinate system and view. The conversion work, and regardless of drawing or modifying in that viewport, the final result will be displayed in the other viewports as well. When there is interference between simple entities that make up a 3D solid, you can also draw different simple entities in different viewports.
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