Research on the production of CNC machining technology

    CNC is also called computer gongs, CNCCH or CNC machine tools. Some people in Guangzhou, Jiangsu, Zhejiang and Shanghai are called "CNC machining centers". (Numerical control machine tool) is the abbreviation of computer numerical control machine tool (Computer numerical control), which is an automatic machine tool controlled by a program. The control system can logically process the program specified by the control code or other symbol instructions, and decode it by the computer, so that the machine tool can operate and process the parts. CNC machining (CNC Machining) CNC machining refers to the use of CNC machining tools for processing, by CNC machining language programming control, usually G code. CNC machining G code language to tell the CNC machine tool processing tool using what kind of Cartesian position coordinates, and control the tool feed speed and spindle speed, as well as tool converter, coolant and other functions. General CNC machining refers to precision machining, CNC machining lathes, CNC machining milling machines, CNC EDM wire cutting (EDM wire cutting), etc.

With the large number of applications of CNC machine tools and the rapid reduction of CNC machining costs, people find that CNC machining has greater advantages over manual machining, not only high dimensional accuracy, fast speed, but also competitive cost. CNC machining can produce parts with complex shapes that cannot be completed by manual machining, making it possible to manufacture a large number of hand models. Usually, the machining workshop uses CAM (computer aided manufacturing) software to automatically read CAD (computer aided design) files and generate G code programs to control CNC machine tools. CNC machining technology, as a product of the rapid development of modern industrialization, involves programming, processing, grinding, spraying and assembly of various production processing links, the overall quality of CNC hand model put forward higher requirements.

Splitting of hand model parts processing

For models with complex structures and thicker plastic plates, the processing and production of hand models often need to be split and spliced, and three-dimensional modeling software such as UG can be used for automatic layering. CNC hand board model has good processing accuracy and high strength, so considering the material cost and the processing time required to complete the overall hand board project, try to adopt the overall processing instead of splitting. For the processing of many plastic shells, ordinary three-axis machining knives cannot be extended, and multi-axis machining is not necessarily applicable, so it is necessary to separate the parting surface for processing and splicing. General parts design has taken into account the mold processing conditions, so there are few hand model parts that must be disassembled. Another case of the split of the hand model is that the extended part of the model is relatively large. In order to save materials and reduce processing time, if the accuracy allows, the necessary long extended parts are cut off and processed independently, and then spliced. When the model processing of hollow structure needs to be split, the installation datum should be added to avoid plane contact without positioning.

Workpiece Blank Setting

The setting of blank is the basis of processing programming, including size setting and position setting. When setting the external dimensions of the workpiece, the length, width and height dimensions are directly input to the actual blank. Before blanking, the recommend uses the envelope boundary method to select geometric objects in the drawing area, and the system uses the envelope shape of the selected objects to define the size of the workpiece. Blank expansion can be based on the accuracy of the blanking machine, in line with the principle of saving materials, generally add 3 xiu, size automatically generated and then rounded. The position coordinates of the blank should conform to the processing habits and be consistent with the actual situation. Usually, the top surface of the model is set to zero, and the center of the blank is used as the programming origin. In order to reduce the possibility of error, it is recommended to move the center of the blank to the origin of coordinates.

surface machining error

In CNC machining, programming software Mastercam provides 8 kinds of rough machining path and 11 kinds of finishing path, can basically meet the requirements of surface processing, but the efficiency and effect of various types of processing path is not the same, the choice must be careful. The main daily processing methods are: flat form processing, contour processing, curved surface grooving rough processing, projection processing, intersection angle clearing spike processing, ring equidistant finishing. Groove digging is used most in roughing. Due to good cutting performance, semi-finishing such as roughing of residual materials is rarely performed in plastic processing. In finishing, the surrounding equidistant finishing has a good cutting effect, and the intersection line clear angle finishing is very useful in model processing, and the processing efficiency is high.

CNC system generally can only linear, circular interpolation, and for other curves are approximate processing, CNC system by adjusting the processing step to control the error, but this is not infinite, not only by the machine tool motion accuracy restrictions, and tool path fitting error is too small, may make the processing program length multiplied, CNC machine tool processing efficiency is reduced. General finishing to take 0.0 l-0.02mm, in the rough machining and program debugging stage can be increased to 0.1mm or more, in order to improve the programming efficiency and processing efficiency. Theoretical research and experiments show that the roughness of surface machining mainly refers to the residual height between the tool paths, which is determined by the line spacing between the tool paths, related to the tool radius and the surface curvature of the T-piece, and is the main source of surface machining error.

Reduce the length of the tool path

The tool motion includes a cutting motion and a non-cutting motion. The non-cutting motion itself does not take much time, but the frequent conversion of the machine tool between the non-cutting motion and the cutting motion will cause the increase of the acceleration and deceleration time. Machining programming can be multi-choice around the cutting mode. Under the premise of a given cutting speed and feed rate, the length of the tool path is directly related to the cutting efficiency. During the machining process, the shorter the total length of the tool path, the less the machining time. The hand model is generally manufactured by direct cutting of the whole piece of free cutting material. At present, the most widely used is plastic, multi-use glue installation, should take different processing ideas and metal processing. When the plastic model is glued and installed, the whole bottom surface is stable and can be directly cut into the cutting tool. The cutting tool can realize split cutting from the material, and all blank materials should be avoided. It is generally believed that bidirectional cutting has changed the processing method of forward milling and reverse milling, which is unfavorable to machine tools, tools and processing quality, but the plastic is softer and the ball screw clearance of CNC machine tools is small, so the impact is not large. It can be boldly used in the processing of hand models.

CNC hand model making is a complex system engineering, involving CAD, CAM, CNC machining, plastic cutting technology and other aspects. The plastic, aluminum and other materials used in the CNC model are consistent with many products, and the cutting efficiency is high. It is the first choice for the enterprises of the model. In the current situation that rapid prototyping technology has not yet been popularized, the prototype manufacturers equipped with ordinary CNC machine tools can improve the processing accuracy and efficiency by optimizing the programming to meet the production needs. Beijing Jingke, as a professional CNC hand model making company, is equipped with advanced production equipment and facilities to meet the diversified production needs of customers, including: Swiss Mikrone high-speed machining center, gantry CNC machining center, high-precision engraving and milling machine, as well as two-dimensional processing equipment cars, milling, grinding machine tools, wire cutting and electric spark machines, etc. Jingke Xingye Handplate Factory, with complete production and processing equipment, perfect management system and experienced production and management team, always adheres to the quality innovation and development, gives full play to the brand advantages in the industry, and serves every customer professionally and sincerely.