What Is Pre-Process of Rapid Prototyping？

Rapid prototyping (RP) technology is an advanced manufacturing technology developed in the 1990s. It is a key common technology serving the development of new products for manufacturing enterprises. RP technology plays a positive role in promoting product innovation, shortening the development cycle of new products and improving product competitiveness. Since the advent of this technology, it has been widely used in the manufacturing industry of developed countries, resulting in a new technology field.

Today we will introduce pre-process of rapid prototyping.

 

 

Building 3D Model

Because the rapid prototyping system can only accept the three-dimensional model (stereogram) of the product constructed by computer, and then can slice it. Therefore, the first step is to digitize the design idea on the computer, that is, to input the shape and characteristics of the product into the computer. At present, there are two main ways for data input of rapid prototyping machine: one is to design three-dimensional models according to the requirements of products by using computer-aided design software (such as Pro/Engineering, SolidWorks, IDEAS, MDT, Auto CAD, etc.), or to convert the two-dimensional three-view of existing products into three-dimensional model; the other is to have already done so. Some objects can be digitized, such as hand-made models, handicrafts or human organs. The physical shape information can be collected and processed by means of three-dimensional digitizer, CT and MRI, and then transformed into the input data accepted by rapid prototyping machine through corresponding software.

 

 

Approximate Processing 3D Model

Because there are often some irregular free-form surfaces in products, they must be approximated before processing. In the current rapid prototyping system, the most common approximation method is to use a series of small triangular planes to approximate free-form surfaces. Each triangle is described by coordinates of three vertices and a normal phasor. The size of triangle is optional, so different surface approximation accuracy can be obtained. The three-dimensional model files that have been approximated above are called STL format files (many CAD software provide this function, such as Pro/Engineering, SolidWorks, IDEAS, Auto CAD, MDT, etc.), which are composed of a series of connected spatial triangles. Typical CADs have interfaces for converting and outputting STL format files, but sometimes there are a few errors in the output triangle, which need to be modified locally.

 

 

Slicing Processing 3D Model

Because rapid prototyping is processed by layers of cross-sectional contours, it is necessary to slice the three-dimensional model along the height of the prototyping at regular intervals before processing in order to extract the cross-sectional contours. The size of the interval is selected according to the requirements of the precision and productivity of the formed parts. The smaller the interval is, the higher the precision is, and the longer the forming time is. The interval range is 0.05-0.5 mm, which is about 0.1 mm in common use. Under this value, a fairly smooth forming surface can be obtained. When the slice interval is selected, the thickness of each layer of superimposed material should be appropriate. Various rapid prototyping systems are equipped with slice processing software, which can automatically extract the cross-section profile of the model.