March 2021 – Page 12 – CNC Machining & Turning, Milling, Metal parts

CNC computer gong processing to prevent collision

Due to the high cost of NC machining, in order to save the cost, a NC machining simulation system is developed. NC machining simulation system can reduce or even completely eliminate the process of trial cutting and manual verification. Before the actual processing of new NC machining program, the programmer can use NC machining simulation system to carry out virtual machining environment and machining process on the computer, and detect the possible problems in the program design.

In the process of NC machining, it is easy to over cut, under cut and other phenomena. At the same time, the damage of the tool, or the processing of waste products, the interference and collision between parts and tools, tools and fixtures, tools and worktable, will cause a certain waste of cost to the production. The NC machining simulation system can simulate the relevant programs well and reduce the loss to the greatest extent.

Before the actual processing, the programmer can confirm whether the finished cutting product is consistent with the original design drawing through the simulation system, and can make better detail analysis.

collision detection

In the actual processing, five axis NC machining has more advantages than three-axis NC machining, can achieve a wider range, has faster material and efficiency, can reduce processing time and improve surface accuracy. However, because of the high degree of freedom of the two additional rotating shafts, it is easy to collide and damage the machine tool.

Therefore, before the actual processing, we need to use the NC machining simulation system to detect the collision. The main detection algorithms are as follows

The machine tool includes many parts, but the collision detection algorithm between different parts is similar. The simulation system takes the tool, workpiece and fixture as the main research object to detect the possible global collision.

According to the tool location, the grid voxel model of the cutter head scanning body and the grid voxel model of the cutter handle scanning body are solved respectively. The tool holder scanning body is used to detect whether there is a global collision between the tool, workpiece and fixture, and the tool head scanning body is used to calculate the intersection between the tool and workpiece.
A feature attribute of voxel model is cuboid envelope box, which is used for rough judgment. If the envelope box does not intersect, the objects surrounded in the envelope box must not intersect. At this time, the position data information of the object envelope box is updated, and other information remains unchanged, so as to prepare for the generation of the next cutter scanning volume and collision detection. Rough judgment can speed up the detection Speed.
Once a collision occurs, the system stops reading the data and reports the error information and the exact location of the collision. If there is no collision, the system will continue the teaching operation between the cutter head and the workpiece.

Characteristics of CNC machining center

CNC machining center has good processing consistency and economic benefits. Compared with other CNC machine tools, it has the following characteristics

When the workpiece is complex and the process flow is very long, it can eliminate the human interference factors in the process flow, and has high production efficiency and quality stability.
Due to the centralized working procedure and the automatic tool changing device, the workpiece can complete the complex processing of milling, drilling, boring, expanding, reaming and tapping with accuracy requirements after one clamping.
When there is an automatic exchange table, when a workpiece is being processed, the other table can realize the clamping of the workpiece, so as to greatly shorten the auxiliary time and improve the processing efficiency.
The larger the tool capacity is, the wider the machining range is, and the higher the flexible program is.

Steps of CNC machining precision parts

CNC machining mainly refers to the use of digital information recorded on the media to control the machine tool, so that it can automatically perform the specified processing tasks. Numerical control machining can ensure the products to achieve high machining accuracy and stable machining quality; the operation process is easy to achieve automation; high productivity, short production cycle; can reduce a large number of process equipment to meet the needs of rapid product upgrading; it is usually closely linked with CAD to achieve the transformation of design ideas to the final product.

In the whole CNC process, we should focus on the relationship between the processes and the significance of each step. Broadly speaking, the whole process consists of product analysis graphic design process planning path generation path simulation path output processing inspection.

Product analysis through product analysis should obtain certain composition information and some specific processing requirements.
Graphic design graphic design should be based on the detailed analysis of the product, determine the type of graphics by analyzing the processing requirements, and draw through the graphics software.
Path generation the process of path generation is that we realize the process planning by software, and optimize the tool path by setting parameters.
Through the analysis of the appearance and processing requirements of the workpiece product in the early stage of process planning, each processing step is reasonably established from the overall situation of processing.
After the path simulation path is generated, we generally have no intuitive sense of its final performance on the machine tool. Here we can check the possible problems through path simulation, so as to reduce the scrap rate of actual processing. The general inspection focuses on the effect of the workpiece appearance, whether it is overcut or undercut, and whether the process planning of the path is reasonable.
Path output path output is a necessary step for software design and programming to realize on the machine tool. Through path output, the intermediate reference can establish a connection between the two. If you have NC professional background, it can also be understood as the post-processing of tool path.

Deviation of processing accuracy of computer gong

With the rapid development of CNC machining center, the replaceable headstock machining center has appeared. It is equipped with a number of automatically replaceable multi axis headstock with cutting tools, which can process the workpiece at the same time. After decades of development, the current CNC lathe has achieved computer control and has been widely used in industry, especially in the mold manufacturing industry. Horizontal machining center generally has indexing turntable or numerical control turntable, which can process all sides of the workpiece; it can also make joint movement of multiple coordinates to process complex space surface. The vertical machining center generally does not have a turntable, only for the top surface processing. In addition, there are compound machining centers with vertical and horizontal spindles, and vertical and horizontal adjustable machining centers whose spindles can be adjusted into horizontal or vertical shafts. They can process five surfaces of the workpiece.

The automatic tool changing device of CNC machining center of milling machine is composed of tool magazine and tool changing mechanism. There are many kinds of tool magazine, including disc type and chain type. The storage capacity of chain magazine is large.

The tool change mechanism exchanges tools between the machine tool spindle and the tool magazine, commonly known as the manipulator; there are also no manipulator and the spindle directly exchanges tools with the tool magazine, known as the armless tool change device.

High precision and stable quality. It is processed according to the instruction given by the digital pattern. Under normal circumstances, there is no need for manual interference in the labor process, which eliminates the deviation caused by the dominator. When planning to manufacture CNC machine tools, many methods are adopted to make the parts of CNC machine tools reach higher accuracy and stiffness. The movement equivalent of CNC machine tool worktable is widely up to 0.01 ~ 0.0001mm, and the reverse clearance of feed transmission chain and screw pitch deviation can be compensated by CNC device. The high-grade CNC machine tool adopts the closed-loop control of grating ruler for worktable movement. The machining accuracy of CNC machine tool has improved from ± 0.01 mm to ± 0.005 mm or even higher. The positioning accuracy has reached ± 0.002mm to ± 0.005mm in the middle of 1990s. In addition, the transmission system and layout of CNC machine tools have high stiffness and thermal stability. By using the compensation technology, CNC machine tool can get higher machining accuracy than its own. In particular, the progress of a unified batch of parts production uniformity, product qualification rate is high, processing quality is stable. The selection of milling cutter diameter depends on different products and production batches, and the selection of cutter diameter mainly depends on the specifications of the equipment and the processing size of the workpiece.

Plane milling cutter

When selecting the diameter of the plane milling cutter, the power required by the cutter should be within the power range of the machine tool, and the diameter of the machine tool spindle can also be used as the basis for selection. The diameter of plane milling cutter can be selected according to d = 1.5D (D is the diameter of spindle). In batch production, the tool diameter can also be selected according to 1.6 times of the cutting width of the workpiece.

end mill

The selection of end mill diameter should mainly consider the requirements of workpiece processing size, and ensure that the power required by the tool is within the rated power range of the machine tool. If it is a small diameter end mill, we should mainly consider whether the maximum revolution of the machine tool can reach the minimum cutting speed of the tool (60m / min).

Slot cutter

The diameter and width of the groove milling cutter should be selected according to the size of the workpiece to be machined, and the cutting power should be ensured within the allowable power range of the machine tool. Before using the CNC machine tool, you should read the manual of the machine tool and other relevant information carefully, so as to operate the machine tool correctly, and pay attention to the following points:

(1) The PLC program of the machine tool is designed by the machine tool manufacturer according to the needs of the machine tool, and does not need to be modified. Incorrect modification, operation of the machine tool may cause damage to the machine tool, or even injury to the operator;

(2) It is suggested that the machine can run continuously for up to 24 hours. If the continuous running time is too long, the service life of the electrical system and some mechanical components will be affected, which will affect the accuracy of the machine

(3) The operators and maintainers of machine tools must be professionals who have mastered the corresponding professional knowledge of machine tools or have received technical training, and must operate the machine tools according to the safety operation regulations and safety operation regulations

How to process complex parts with computer gong

The continuous fine blanking die for complex parts is the frontier basic technology of fine blanking technology, and it is expected to promote the whole fine blanking technology in China. Taking the synchronizer gear ring, clutch plate, longitudinal compound continuous fine blanking process and continuous fine blanking die for complex parts as the breakthrough point, the key technology of fine blanking die design and manufacturing is studied, so as to realize the rapid improvement of fine blanking die technology in China and shorten the gap with advanced countries as soon as possible.

Study on the life promotion of fine blanking die and its related key technologies

Die life is a comprehensive reflection of die material, small craft and supporting product level,

It can not only solve the problem that the life of fine blanking die is too low, but also promote the technical development of die materials, fine blanking process, supporting tooling and other auxiliary products.

Research and development of fine blanking precision forging composite technology

Precision blanking and precision forging are two advanced manufacturing technologies developed in parallel. If the precision blanking parts are too thick and need precision forging, the precision forging must be too thin. They are closely related. The basic idea of developing precision forging and fine blanking compound process is to find the combination point of the two processes (such as gear parts with wheel hub and cam parts with short shaft). The precision forging in China has a long history and has a high level, so it is a good way to improve the overall level of precision blanking technology in China.