快速成型技术采用离散/堆积成型原理，根据三维CAD模型，对于不同的工艺要求，按一定厚度进行分层，将三维数字模型变成厚度很薄的二维平面模型。再将数据进行一定的处理，加入加工参数，产生数控代码，在数控系统控制下以平面加工方式连续加工出每个薄层，并使之粘结而成形。实际上就是基于“生长”或“添加”材料原理一层一层地离散叠加，从底顶完成零件的制作过程。快速成型有很多种工艺方法，但所有的快速成型工艺方法都是一层一层地制造零件，所不同的是每种方法所用的材料不同，制造每一层添加材料的方法不同。

Rapid prototyping technology adopts the principle of discrete/stacked molding. Based on the three-dimensional CAD model, for different process requirements, it is layered according to a certain thickness, transforming the three-dimensional digital model into a two-dimensional flat model with very thin thickness. Further process the data, add machining parameters, generate CNC codes, and continuously process each thin layer in a flat machining manner under the control of the CNC system, and make it bond and form. In fact, it is based on the principle of "growth" or "addition" of materials, layer by layer discrete stacking, completing the manufacturing process of parts from bottom to top. There are many process methods for rapid prototyping, but all of them involve manufacturing parts layer by layer. The difference is that each method uses different materials and the method of adding materials to each layer is different.

快速成型的工艺过程原理如下

The process principle of rapid prototyping is as follows

三维模型的构造:在三维CAD设计软件中获得描述该零件的CAD文件。一般快速成型支持的文件输出格式为STL模型，即对实体曲面做近似的所谓面型化(Tessellation)处理，是用平面三角形面片近似模型表面。以简化CAD模型的数据格式。便于后续的分层处理。由于它在数据处理上较简单，而且与CAD系统无关，所以很快发展为快速成型制造领域中CAD系统与快速成型机之间数据交换的标准，每个三角面片用四个数据项表示。即三个顶点坐标和一个法向矢量，整个CAD模型就是这样一个矢量的集合。在一般的软件系统中可以通过调整输出精度控制参数，减小曲面近似处理误差。如Pre/1E软件是通过选定弦高值(ch-chordheight)作为逼近的精度参数。

Construction of 3D model: Obtain the CAD file describing the part in the 3D CAD design software. The file output format supported by general rapid prototyping is STL model, which approximates the solid surface through the so-called Tessellation process, using planar triangular patches to approximate the model surface. To simplify the data format of CAD models. Facilitate subsequent hierarchical processing. Due to its simplicity in data processing and independence from CAD systems, it quickly developed into a standard for data exchange between CAD systems and rapid prototyping machines in the field of rapid prototyping manufacturing, with each triangular surface represented by four data items. The entire CAD model is a collection of three vertex coordinates and a normal vector. In general software systems, surface approximation processing errors can be reduced by adjusting the output accuracy control parameters. Pre/1E software uses the selected chord height as the accuracy parameter for approximation.

三维模型的离散处理:在选定了制作(堆积)方向后，通过专用的分层程序将三维实体模型(一般为STL模型)进行一维离散，即沿制作方向分层切片处理，获取每一薄层片截面轮廓及实体信息。分层的厚度就是成型时堆积的单层厚度。由于分层破坏了切片方向CAD模型表面的连续性，不可避免地丢失了模型的一些信息，导致零件尺寸及形状误差的产生。切片层的厚度直接影响零件的表面粗糙度和整个零件的型面精度，每一层面的轮廓信息都是由一系列交点顺序连成的折线段构成。所以，分层后所得到的模型轮廓已经是近似的，层与层之间的轮廓信息已经丢失，层厚越大丢失的信息越多，导致在成型过程中产生了型面误差。

Discretization processing of 3D models: After selecting the production (stacking) direction, the 3D solid model (usually STL model) is discretized in one dimension through a dedicated layering program, that is, slicing along the production direction to obtain the cross-sectional profile and solid information of each thin layer. The thickness of the layers is the thickness of the single layer stacked during molding. Due to layering, the continuity of the CAD model surface in the slicing direction is disrupted, inevitably losing some information of the model, resulting in errors in part size and shape. The thickness of the slicing layer directly affects the surface roughness of the part and the overall surface accuracy of the part. The contour information of each layer is composed of a series of intersection points connected by a sequence of folded line segments. So, the model contour obtained after layering is already approximate, and the contour information between layers has been lost. The thicker the layer, the more information is lost, resulting in surface errors during the forming process.