Sheet metal parts is a widely used in electrical and mechanical, light industry, automotive industries parts, the past the traditional production method, because a long life cycle, the efficiency is low, the poor quality faults already more and more not adapt to the modern design requirements, in order to overcome these shortcomings, people began to use advanced CAD system, on microcomputer with CAD drawing simple and intuitive, and of great significance.
Sheet metal parts can generally be divided into three categories:
Flat kind points to the general plane shearing pieces.
(2) bending class according to the design CAD graph again on bending and welding.
(3) forming kind of forming methods such as drawing processing from the rules of surface or free surface parts. These parts are made by flat workpieces by cutting and deformation on the way and came out of the stamping process, they and general machining way out of the parts processing is very big difference. In stamping processing way, the bending deformation is make sheet metal parts have complex space position of the relationship between the main processing mode.
2, Sheet metal parts figure modelling of the die design requirements in the process, Sheet metal parts is the shape of the main basis of the mould design, it had decided the mold the general structure and the shape. And sheet metal parts dimensional tolerance will influence the working parts of the mould (such as punch mould and so on) the size and the shape of tolerance. In addition, sheet metal parts of the materials, form and position tolerances and technical requirements of the working parts of mould have a major influence. Therefore, sheet metal parts model should be included in the shape information outside, still must contain parts dimensional tolerance, precision, material and technical requirements and other information, so that we can guarantee the accuracy of the mould design results. Sheet metal parts model is the follow-up mold design application different kinds of information carrier, which requires the parts model can reflect the characteristics of sheet metal parts, specifically is to reflect the sheet metal parts of the engineering semantic, make the mould design application can understand easily extracted with the information they need. On the other hand, 3 d sheet metal parts with complex general position of spatial relationship, only according to the shape of the Sheet metal parts structure characteristics, just may simplify user operations.
So far, the geometricl characteristic and brought out geometric design method, the main use CAD 2 D Sheet metal parts and the geometrical modelling of 3 D sheet metal parts of the geometry of the model. The former is using CAD 2 d drawing, and then put the graphics into AP100 CNC punching software programming (simple graphics as long as in the material such as direct shearing machines cut square and rectangular, etc.). In CNC punching out after the model, in bending machine to bend. The latter is according to the shape of the parts in CAD drawing directly after open mold, then rushed out of the required shape. The above all modelling method has common faults is when CAD graphics when something goes wrong, change is very troublesome, may even need to.
The pieces of metal characteristics description:
Through the above the sheet metal parts characteristics and requirements of the parts model analysis, as well as to some existing sheet metal parts of the geometrical modelling method introduction, can see, to establish a not only reflect the characteristics of sheet metal parts and to meet the requirements of the system for CAM CAD model sheet metal parts, using feature modeling technology is an effective way. It besides can offer sheet metal parts of the complete information model outside, but also can solve the existing some geometric design method of the existing problems. Now some of the modelling of commercial systems such as Pro/Engineering is using feature modelling method to model the expression of the parts.
Is the product description of the characteristics of information collection, it not only has according to certain of topological relationships of the special shape, but reflect specific engineering semantic, used in design, analysis and manufacturing in use. Characteristic is to achieve CAD/key of integration. Feature can be divided into: shape characteristics, precision characteristics, material characteristics and so on, which is key to shape characteristic, is the other characteristics of the carrier or matrix, it can be defined as having some engineering significance geometric shapes or entities. And CAD is 2 d drawing the most simple software, so in a certain extent, CAD is instead of other software in sheet metal field foundation. From the point of view of the configuration characteristic, sheet metal parts is composed of a series features structure, the relationship between them constitute a complete parts. According to the characteristics of metal sheet, can induce the following features:
(1) plane nature of graphics directly at a cut.
(2) is to use the plane bending features on bending forming again.
(3) hole features it as a general characteristics and the son of attachment to other features, such as in the plane or bend characteristics punching. Holes in the data structure and plane basically the same characteristics. In the picture plane is directly according to size hole draw.
Local forming characteristics of local forming process by in stamping on the shape of the produce. Usually it's fixed shape, size is different, so can use parameters to express.
Among them, the pieces of metal plane and bending surface is mainly features, and punching and local forming characteristics as the main characteristics of subsidiary description. Each plane feature can be connected with multiple bend characteristics, and each bend characteristics can only at the ends and two plane characteristics connected.
The characteristic information form feature is the most important design information! Also called the geometry of the feature! So the information around the shape characteristics of! And the most important part of shape characteristic is launched, according to the design of your own drawing on the right.
The realization of the characteristic model in this paper, choose AutoCAD as the characteristic model established part product model of sheet metal design platform, and introduce parametric technology, features of the nature of the parametric, its attribute to the form of parameters to express. Designer established beforehand feature library, including sheet metal parts of the common features, such as flat, hole and all kinds of chamfer, design is first the general information input parts, choose feature library of substrate characteristics, generating matrix characteristics, based on this, the features of assembly model. And then from feature library circulation to select the characteristics, through the characteristic parameter table and positioning parameter table gives characteristic parameters and positioning parameters, and features of assembly, form characteristic model. Finally the input other characteristics information, set up product characteristic model.
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