However, with the improvement of industrial technology and the growth of economic environment, the functional requirements of any general product are no longer the only condition to win market competitiveness under the high quality requirements of consumers. Under the impetus of modern high-function CAE software, the emerging field of "industrial design" (also known as "product design") has been paid more and more attention. Any product not only requires advanced functions, but also needs to be designed in the appearance of its objects to attract consumers' attention. This kind of modeling design is mostly aimed at the aesthetic appearance of products. In the process of forward engineering, mechanical engineers under traditional training are incompetent. Some designers with artistic background can use CAE technology to conceive innovative aesthetic appearance, and then make models by hand, such as wood mold, gypsum mold, clay mold, wax mold, engineering plastic mold, glass fiber mold and so on. And then the CAD drawing of free-form surface model is established through three-dimensional measurement. This program has the concept of reverse engineering, but it is still a part of forward engineering, with the concept of object-oriented, and the company also retains the intellectual property rights of design drawings. The modeling and design process in this forward engineering is shown in Figure 2-2.
Therefore, forward engineering can be summarized as function-oriented, object-oriented, defined model, future system and legacy system.
Before computer drawing, engineering drawings were mostly drawn by hand. At this time, the 2D sketch is the main construction drawing, and the assembly part describes the 3D structure. At this time, 2D and 3D are drawn separately, so it cannot be called forward engineering. With the development of hardware and software, computer drawing has replaced manual drawing. In this process, the 2D graphic files drawn by computer can be arranged properly, and the three-dimensional diagram can be drawn conveniently. This process can be said to be a kind of forward engineering, in which concepts and dimensions are expressed on the 2D plan (most early masters can only understand the 2D plan), and then a 3D stereo map is drawn with 2D pixels and related dimensions.
2D Sketch → 3D Stereograph
L 2D plane drawing file: generally speaking, AUTOCAD_XX is the most commonly used software in the industry, such as (FIG. 1- 1). Of course, other well-known softwares include CADKEY, PRO_E, CATIA… and so on.
L File transfer: If the same software is used to draw 2D plan (2D drawing module) between different modules, then continue to build 3D stereogram after drawing. Because it is on the same software operating platform, there is no file transfer problem. Unfortunately, no software has absolutely powerful functions in all professional applications; For example, in the drawing of plane engineering drawings, professional draftsmen can use AUTOCAD quite well. Although AUTOCAD can also draw regular three-dimensional drawings of mechanical parts, once complicated surface changes are encountered, it may be more efficient to use professional three-dimensional drawing software at this time, and we will encounter the problem of conversion between drawings and files. For 2D graphics, the file extension is DWG DXF ... and so on, while 3D space is more common.
DXF: 2D graphics exchange file between different softwares.
DWG: Drawings with this extension are unique to AutoCad.
IGES: (Initial Graphic Exchange Specification) In different software.
Graphic exchange file between 2D and 3D.
Commercial CAD/CAM software: Generally speaking, we can divide it into parametric CAD/CAM software and nonparametric CAD/CAM software; CAD/CAM Software Based on Curved Surface Structure and Stereo Structure
Parametric CAD/CAM software: PRO_E, UG, CATIA…
Nonparametric CAD/CAM software: EUCLID, STRIM 100…
SRUFACE architectural CAD/CAM software: EUCLID, STRIM 100… as shown in figure (FIG: 1-2).
CAD/CAM software of entity building: PRO_E, UG, CATIA…
Creative design (original product design)
Standard mechanical component design
Shape design (drawing method of sports shoes)
What is reverse engineering?
L reason
Reverse engineering usually simulates the model in the form of projects. Often, a product to be produced has no original design drawings, but a sample or model, such as wooden shoe molds and golf clubs, is sent by the entrusting unit, and the production unit is required to copy it. The traditional copying method is to use a three-dimensional engraving machine or a hydraulic three-dimensional copying milling machine to make one-to-one proportional molds, as shown in Figure 2-3, and then carry out mass production. This method is called analog copy. It can't create a graphic file of workpiece size or make any shape modification, and it has been gradually replaced by a new digital reverse engineering system.
At present, the so-called reverse engineering is to accurately and quickly measure the contour base of an existing workpiece (sample or model) with a 3D digital measuring instrument, then construct a curved surface, edit and modify it, and then transmit it to a general CAD/CAM system, and then send the NC machining path of the cutter shell generated by CAM to a CNC machining machine to make the required mold, or to a rapid prototyping machine to make the sample model. This process is called reverse engineering, as shown in Figure 2.
Therefore, reverse engineering can be summarized as function-oriented, description mode, system as it is and non-legacy system.