3D模型創建

3D model creation

由于實現快速成型的系統只能接受計算機構建的產品的三維模型（立體圖），然后才能進行切片加工，所以要在計算機上實現設計思想的數字化，即即，將產品的形狀、特性等數據輸入計算機。目前，快速成型機的數據輸入主要有兩種方式：

Because the rapid prototyping system can only accept the three-dimensional model (stereogram) of the product built by the computer, and then can carry out slicing processing, it is first necessary to digitize the design idea on the computer, that is, input the shape, characteristics and other data of the product into the computer. At present, there are two main methods for data input of rapid prototyping machine:

一是設計人員利用計算機輔助設計軟件（如Pro/Engineering、SolidWorks、IDEAS、MDT、AutoCAD等）根據產品要求設計3D模型，或將現有產品的2D和3D視圖轉換為3D模型；

First, designers use computer-aided design software (such as pro/engineering, Solidworks, ideas, MDT, AutoCAD, etc.) to design 3D models according to product requirements, or convert 2D and 3D views of existing products into 3D models;

另一種是將現有對象數字化，可以是手工模型、手工藝品，也可以是人體器官。這些物體的形狀信息可以通過3D數字化儀、CT和MRI等手段進行采集和處理，然后通過相應的軟件將獲得的形狀信息等數據轉化為快速成型機能夠接受的輸入數據。

The other is to digitize the existing objects, which can be manual models, handicrafts, or human organs. The shape information of these objects can be collected and processed by means of 3D digitizer, CT and MRI, and then the obtained shape information and other data can be transformed into input data that can be accepted by the rapid prototyping machine through corresponding software.

3D模型的近似處理

Approximate treatment of 3D model

由于產品上經常有一些不規則的自由曲面，在加工前必須進行近似。在目前的快速成型系統中，常用的逼近方法是用一系列小三角形平面來逼近自由曲面。其中，每個三角形由3個頂點的坐標和一個法線相量來描述。

Because there are often some irregular free-form surfaces on the products, they must be approximated before machining. In the current rapid prototyping system, the common approximation method is to use a series of small triangular planes to approximate the free-form surface. Each triangle is described by the coordinates of three vertices and a normal phasor.

可以選擇三角形的大小以獲得不同的曲面逼近精度。經過上述近似處理后的3D模型文件稱為STL格式文件（很多CAD軟件都提供此功能，如Pro/Engineering、SolidWorks、IDEAS、AutoCAD、MDT等），由一系列相連的空間三角形組成。

You can select the size of the triangle to obtain different surface approximation accuracy. The 3D model file after the above approximate processing is called STL format file (many CAD software provide this function, such as pro/engineering, Solidworks, ideas, AutoCAD, MDT, etc.), which is composed of a series of connected spatial triangles.

典型的計算機輔助設計具有用于轉換和輸出STL格式文件的接口。但是，有時輸出的三角形會有少量誤差，需要在本地進行修改。

A typical CAD has an interface for converting and outputting STL format files. However, sometimes the output triangles have a small amount of error and need to be modified locally.

切片3D模型

Slice 3D model

山東快速成型提醒您，由于快速成型是逐層斷面輪廓加工的，所以在加工前需要將三維模型沿成型高度方向每隔一定的間隔進行切片，以便提取橫截面的輪廓。

Shandong rapid prototyping reminds you that since rapid prototyping is processed layer by layer, it is necessary to slice the 3D model at certain intervals along the molding height direction before processing, so as to extract the profile of the cross section.

間隔的大小根據成型零件的精度和生產率的要求來選擇。間隔越小，精度越高，成型時間越長；相當光滑的成型表面。切片間隔選定后，每層疊加的材料厚度應與之相適應。各種快速成型系統都配備了切片軟件，可以自動提取模型的橫截面輪廓。

The size of the interval is selected according to the accuracy and productivity requirements of the formed parts. The smaller the interval, the higher the precision and the longer the forming time; Fairly smooth formed surface. After the slice interval is selected, the superimposed material thickness of each layer shall adapt to it. Various rapid prototyping systems are equipped with slicing software, which can automatically extract the cross-sectional profile of the model.

這里介紹快速成型的過程之前處理準備的相關內容。您可以訪問我們的網站www.ebook5.cn進行咨詢以獲取更多信息。

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