Research on three coordinate measurement and rever

CMM and reverse engineering research

1. Overview

since the development of human society, it has experienced thousands of years of research and exploration, and has accumulated rich knowledge wealth and scientific and technological achievements in all aspects. It is the foundation of product development and the precious wealth of mankind. However, due to historical limitations, in the era without computers, most of the heritages are recorded by simulation. In today's digital era, it is inconvenient to use these knowledge and achievements quickly. This requires a lot of analog information to be transformed into digital models for future product development. In mechanical products, we can use the idea of reverse engineering to quickly complete the conversion with CMM

turning over the history of human exploration and research for thousands of years, you will find that each achievement is achieved by imitating the things, animals or people with corresponding specialties and characteristics in the relevant fields of nature and human society on the basis of previous studies. Seeing the birds in the sky, we imitated the aircraft, but the aircraft flew higher, faster and farther than the birds; Seeing the whales in the midstream of the sea, people imitated submarines, but submarines dive deeper, larger and have stronger ability to continue diving than whales That is to say, human beings have been learning the existing things. The Waterford Institute of technology in Ireland and the Engineering School of the National University of justice in Thailand will bring lectures on "the use of hydrogels from contact lenses to medical catheters, absorbable medical devices and regenerative medicine", study existing things and copy existing things, that is, human beings have been working in the way of reverse engineering, not only copying the prototype, but also surpassing the prototype

the process of developing products through samples is called reverse engineering, which is opposite to the forward design process of products. Reverse engineering mainly refers to the process of studying others or existing systems or products, discovering their laws, and copying, improving and surpassing existing products or systems. Reverse engineering is not only the imitation of the real world, but also the transformation of the real world. It is a kind of transcendence. The key technologies involved in it mainly include: 3D solid geometry data acquisition, regular or large amount of discrete data processing, 3D solid model reconstruction, machining and so on

2. CMM is the data collector and data source of reverse engineering.

CMM is an efficient and high-precision measuring instrument produced with the rapid development of computer and machine tool industry in recent decades. It adopts the principle of coordinate measurement, and completes the three coordinate data acquisition of workpiece geometric dimension and geometric tolerance under the control and drive of computer software. It organically combines input parameters with digital control technology, uses computer software technology, adopts advanced position sensing technology and precision mechanism technology, and makes it a perfect combination. It conforms to the development direction of hardware and software technology with high accuracy and sensitivity for the measurement and control of load, deformation and displacement. What should be paid attention to, such as tooth 2 and the selection of universal material testing machine? Wheels, cams, turbine rods, etc. used to require special testing equipment to complete the workpiece. Now the general CMM can be used for data collection, combined with the corresponding measurement and evaluation software to achieve professional detection and evaluation functions

by understanding the principle of CMM, people can easily know its superior characteristics: high efficiency, high precision, high flexibility and considerable specificity. Adopting advanced sensing technology, digital control technology, computer software control and processing technology, the CMM has high data acquisition and processing efficiency; It is based on the precise mechanical body, adopts software control and compensation technology, and is equipped with high-precision position sensors to achieve high precision. It realizes the measurement of spatial coordinate points, and uses computer software to complete the evaluation of product geometric dimensions and geometric tolerances. Different types of products can be completed as long as the software is adjusted, which not only makes the CMM machine highly flexible, but also has the corresponding specificity

if reverse engineering wants to copy samples, it must have corresponding data information. Data collection is the starting point and basic activity of reverse engineering

based on the above three coordinate characteristics, it can be said that CMM is an ideal data collector for reverse engineering

3. Data collection planning in reverse engineering

collection planning aims to make the collected data correct and efficient. Correct means that the collected data is sufficient to reflect the characteristics of the sample without misleading; High efficiency means that when the product characteristics can be correctly expressed, the collected data should be as few as possible, the path should be as short as possible, and the time should be as little as possible

there is a basic principle for product data collection: follow the characteristic direction and the normal direction. Just like a train, it walks along the track and collects digital information along the sleeper. This is a general principle, which should be determined according to specific products and reverse engineering software. The following is divided into three aspects

data acquisition planning for regular shapes:

for regular shapes such as points, straight lines, arcs, planes, cylinders, cones, balls, etc., as well as extended regular shapes such as hyperbolas, helixes, gears, cams, etc., contact probes with high accuracy are used for data acquisition. Data acquisition planning is carried out according to the point information required for mathematical definition of these elements, which will not be explained here. Although we attribute the shapes of some products to features, the actual products cannot be theoretical shapes. The differences in processing, use and environment also affect the shapes of products. As the measurement planning of reverse engineering, we should not only focus on the extraction of "features", but also consider the change trend of products, that is, analyze the geometric tolerance

the following table is the minimum number of data points required for mathematical description of each rule element. To describe its tolerance and change, more points need to be measured