Vliv výběru CNC nástroje na proces CNC obrábění
With the rapid development of production technology, the use of CNC technology in industry has become increasingly popular, providing a new, intelligent development trend for the entire industry. The development of technology has given rise to a new process that is very different from the traditional machining process – CNC tooling. In this paper, according to the general environment of today’s scientific and technological development, elaborate on the selection of CNC tools in CNC process machining, and point out how to reasonably choose CNC tools, in order to improve the production efficiency and technology level of enterprises.
With the improvement of China’s economic and technological level, CNC tools have been developed, and a large number of new tools have entered the market, resulting in changes in CNC processing technology. In order to improve the efficiency of production and manufacturing, the enterprise has made adjustments to the relevant machinery manufacturing and construction processes, and has carried out a lot of simplification processing to minimize the processing margin. On the premise of not reducing the quality, high requirements are put forward for all parameters and quality of the whole finishing process. In order to make the numerical control tools conform to the corresponding specifications, the numerical control processing technology must be continuously improved and optimized. To some extent, the overall transformation of the numerical control processing technology is mainly due to the development of the numerical control tools. At present, in order to improve production efficiency, many modern enterprises are introducing new numerical control tools. The use of these numerical control tools also makes the new numerical control processing technology widely used. Next, the author will elaborate and analyze the specific impact of CNC tools on CNC machining process.
1. Connotation of CNC tool
The emergence of numerical control tools is actually a manifestation of the application of numerical control technology in the machinery manufacturing industry. Compared with traditional tools, numerical control tools can automatically change tools, and the quality of the tool body is also higher than that of traditional tools, which can complete efficient and high-precision operations. This requires CNC tool manufacturers to provide customized solutions according to the actual needs of CNC machining, which will greatly change the production and sales mode of the tool industry. In this way, customers can not only find the most suitable CNC tool in the sample, but also customize it according to their own needs and cutting parameters provided by customers.
CNC tools can be divided into:
- 1) Integral type, that is, the tool made of a blank, is a whole;
- 2) Welding type, that is, the tool handle and the tool tip are connected by welding;
- 3) Machine clamp type is the most commonly used tool structure for CNC machining. In addition, it also includes special tool structures such as compound type and damping type.
CNC tools are characterized by good cutting performance, long service life, high accuracy, strong self-adjusting function, reliability, modularization, standardization, etc. Specifically, the manufacturing process of traditional tools is relatively simple, while CNC tools must be processed with machines. The automatic tool change device of CNC tool can perform automatic tool change operation accurately and quickly, which improves the efficiency of production and manufacturing to a certain extent. If the management is carried out according to the original single management mode, the following drawbacks will inevitably occur.
- First, the continuous purchase of cutting tools has significantly increased the cost and expenditure of enterprises. The use of tools for individual equipment is usually managed by operators. In this case, due to different operators, there are a large number of duplicate tools in the equipment tools used, and they will hardly be used at the same time, which leads to idle waste and repeated purchase waste.
- Second, the time and cost of using tools will increase. The number of tools has increased significantly. If they are not placed according to the same identification or classification, it will increase the difficulty of using tools, thus increasing the time cost.
- Third, add the configured tool adjustment tool repeatedly. Due to different types of tools, the required adjustment tools are also different. The decentralized management mode leads to many knives being distributed together, and some will even be used and stored by other people. Although there are many tools, there are no suitable tools in the process of use.
- Fourth, when new and old employees change, separate training will improve the input of human resources. In addition, the price of some tools is relatively high. If used improperly, it will cause serious losses, resulting in higher opportunity costs for enterprises. Tool maintenance needs to be carried out without control. Some small problems can be repaired. However, due to unclear responsibilities and no one to deal with them, it is likely that the tool will be completely scrapped.
- Fifthly, decentralized management of cutting tools is not conducive to process designers to reasonably configure processing technology according to cutting tools. In production, if you cannot fully understand the use of tools, you will not be able to effectively reduce production costs.
Therefore, when conducting propaganda, we should pay special attention to the selection of CNC tools, and design the tool card according to the specific situation of the work, so as to carry out the management work in the future.
2. Features of CNC tools
With the development of today’s society, various emerging technologies have emerged as the times require. At the same time, the technological processes related to machinery manufacturing and production have also developed. As a new technology, CNC machining technology is often affected by many aspects in practical use. Among them, whether the tool selection is reasonable or not will have a great impact on the production efficiency of the CNC machining process. Therefore, in order to ensure that the selection of cutting tools will not adversely affect the results of CNC machining, it is necessary to comprehensively understand and grasp them.
The characteristics of CNC tools are as follows: First, good cutting performance, high precision and rigidity of CNC tools, capable of powerful and high-speed cutting. In use, the rigidity and accuracy of CNC tools are relatively high, suitable for cutting operations of various heights and intensities. Secondly, CNC tool materials are characterized by high performance, high toughness and high wear resistance. They have a long service life in the process of use. When they are not subject to external impact, their working life will be longer. Third, the accuracy of CNC tools is high. CNC tools can adjust in various directions during use. Using rotating blades can effectively improve the accuracy of CNC processing technology and ensure the processing quality. Fourth, CNC tools have self-adjusting efficiency. For various processing requirements, CNC tools adopt the method of internal compensation and internal presetting, which can greatly shorten the time of tool change, thus improving the speed of tool change, and have many advantages and characteristics such as modularization, standardization, reliability, etc. In view of the above characteristics, relevant technicians should not only aim at specific cutting requirements, but also take into account the actual cutting performance, detailed requirements, cutting amount and other factors in practical application, so as to reduce the impact of machining on the tool, reduce tool consumption, extend the service life of the tool, improve the processing quality of the CNC machine tool, and ensure the normal operation of the CNC machine tool.
3. Application of CNC tool selection in CNC machining
(1) Countersunk hole processing
In the CNC machining process, countersunk hole is a commonly used part hole diameter. In the traditional CNC machining process, spot facer (with guide pillar) is often used for processing, but the reamer and spot facer are not often used in the CNC machining, and will be replaced by other methods to achieve the processing purpose. The traditional countersunk hole processing is completed by spot facer, and its processing surface is generally narrow, so in the process of processing, formed tools are often used. Its cutting edge is relatively long and prone to vibration, and there are very strict regulations on right angle, profile, coaxiality, flatness and other aspects, which are mainly used for the manufacture of rivets, screws and other joints. The dimensional accuracy of such parts is not high, Moreover, the contour of the countersunk hole is completely consistent with that of the joint. In the process of numerical control machining, forming spot facer machining is not common. Most of them are realized by programming programs, and drilling is realized by numerical control milling. For example, when manufacturing cylindrical countersunk holes, flat-bottomed milling tools are usually selected, and corresponding milling programs are written to achieve the manufacturing objectives; When manufacturing convex table, vertical milling tool is usually used; For conical spot facer, the cutting tool for conical spot facer (special) will be used for processing.
(2) CNC machining of threaded parts
Thread parts are the most commonly used parts in CNC machining at present. Selecting the appropriate thread CNC tool can reduce thread burr and improve efficiency. During machining, select the appropriate screw pitch and nominal size of the spiral milling cutter. The cutter bar mainly uses the BT40-SLA flat tool shank. Thread milling cutters are widely used in various thread processing, with high adaptability. Only one thread milling cutter can complete the thread processing operations with different apertures and the same pitch. Generally, thread milling cutters with tooth profiles can also be used to process various threads, such as American threads, ISO threads, etc. Thread milling can also solve the problems of tool wear, tool bending, material “elasticity”, tapping and so on. In thread processing and manufacturing, tapping is the most difficult part, and chip removal is the difficult point in the process of tapping. An careless one will cause the tap to break, and even cause damage to the parts, while thread processing can solve the problem of chip removal very well.
Generally speaking, a milling cutter made of alloy material with rotating edge can be selected for the CNC machining of threaded parts, and the CNC machining can be carried out by whirlwind milling method. The indexable blade can be replaced reasonably according to the different thread processing, and can be switched freely during the thread processing, so as to meet the requirements of the CNC machining of threads. This kind of alloy material rotatable thread milling cutter has an internal cooling through hole, It can make the coolant reach the cutting position quickly and improve the milling quality. The thread whirlwind milling cutter is selected because it has a high-speed thread milling device. A fast rotating blade is installed on the spiral milling cutter. The suitable blade can be selected according to the requirements of the workpiece. The maximum speed of 400 meters per minute is used in CNC machining, which effectively improves the processing efficiency. This thread whirlwind milling method is very suitable for products such as screw rods, worms, and other products. In addition, it does not need to retract the tool in processing and manufacturing, and it is formed at one time. However, it should be noted that whirlwind milling has shortcomings in the processing of small diameter parts and is prone to deformation. Therefore, when using this method to process small diameter parts, attention must be paid to the alignment of the lead screw.
(3) Special workpiece processing
The body of the valve body parts is rectangular, with five round holes inside, and has the characteristics shown in Figure 1. The key points in the CNC machining process of this part are the processing of its annular inner groove, the rough and fine boring of the inner hole and the 20 ° inner cone finish milling. The processing operator conducted in-depth research on the difficulties in the part processing process and formulated the following plan:
Fig.1 Machining drawing of valve body parts
- 1) The ring groove milling cutter is used to cut the ring inner groove, and BT40-SLN ring groove milling cutter is selected according to the width and diameter of the part;
- 2) In the process of coarse and fine boring of inner hole, CBH25-47 fine boring head, RBH32-42-C coarse boring head and BT40-LBK tool shank are selected according to the characteristics of the valve body parts;
- 3) For the 20 ° short-diameter internal taper finish milling, the selection of cutters is relatively flexible, including fillet milling cutter, interpolation spiral milling cutter, ball milling cutter, etc. The CNC processing operator can select BT40-ER or BT40-SLA milling cutter according to the actual situation.
4. CNC tool selection strategy in CNC machining process
In the numerical control processing of parts, the relevant technical personnel must reasonably select the processing tools according to the processing conditions of parts to ensure the processing quality of parts. When selecting tools, the following methods can be adopted to ensure the quality of CNC machining process.
First, analyze the parts in depth. In the CNC machining process, the relevant technical staff must select the appropriate tool according to the specific characteristics of the parts through the study of the structure, cutting parameters, geometric angles, etc. of the parts to ensure the quality of the products. How to reasonably select CNC tools, how to define different cutting parameters, how to program, and after in-depth analysis of these, the workpiece can be processed finally.
Secondly, the tool selection should be reasonably configured according to the part processing technology. In actual production, a tool often cannot fully meet the actual production and processing requirements, so different parts can be properly configured according to different process conditions to improve the processing quality of products. When selecting the appropriate cutting tools, it is necessary to match the appropriate process methods reasonably to improve the process quality of the product. In addition, for the maintenance of the machine tool, the damaged parts should be replaced in time to ensure the quality of the CNC machining process.
5. Analysis of the influence of CNC tool selection on CNC machining process
CNC machining technology has a great relationship with the production quality of machining, and the selection of CNC tools has a great impact on the development of CNC machining technology. Therefore, the selection of CNC tools directly affects the development of processing technology and even the quality of products. Unreasonable selection will increase the cutting loss of the tool and reduce its accuracy and service life. In the process of mechanical manufacturing, in order to ensure the smooth development of CNC machining process, it is necessary to reasonably select CNC tools. Therefore, in the actual production, the technical operators should consider the main impact on the processing technology when selecting the tool to decide which kind of CNC tool to use. This ensures that the selection of CNC tools meets the most fundamental requirements of machining. To this end, work should be carried out from the following aspects:
- First, the quantity of processed parts is counted; For the needs of mass production and processing, the characteristics of mass order production and manufacturing should be considered in the selection of tools, and special CNC tools with high wear resistance should be selected to achieve better cost savings; For small batch orders, according to the actual production needs, standard CNC tools with higher service life should be selected, which can save more production costs. In the actual manufacturing process, according to the requirements of different processing standards, different CNC tools can be replaced to meet the production requirements of different parts, and the CNC processing parameters can be reasonably selected according to the CNC processing efficiency, accuracy requirements and the characteristics of processing materials.
- Second, select the type of machine tool reasonably; In the process of machining, not only the appropriate numerical control tool should be selected, but also the relationship between the rigidity of the machine tool and the processing object should be fully considered, so the tool with high processing performance should be selected as far as possible when selecting the appropriate tool. The type of CNC tool should be determined according to the CNC machining scheme; In the process of machining and manufacturing, when selecting cutting tools, the shape and size of the workpiece should also be considered. Select the appropriate tool according to the characteristics of the part. If the mold surface is treated, special tools are usually used to ensure that the mold surface treatment results meet the design standards, so as to maximize the accuracy and quality of the process.
- Third, the surface roughness and accuracy requirements of machining; This should also be considered when selecting tools. If the CNC machining process has high requirements for surface roughness and accuracy, then the technicians should select the corresponding tools to ensure the quality of the machining process. If in the process of rough and fine machining of the blank, the coarse tooth milling cutter can be used; In order to carry out precise cutting, it is usually necessary to use fine-tooth milling cutter for cutting. Tools can be used to meet the needs of various products. Of course, the workpiece material also has certain restrictions on the selection of tools, because different materials require different types of tools. The material of the workpiece has a great influence on the performance of the cutting tool, so the parameters, hardness and accuracy of the part itself must be comprehensively utilized. Reasonable selection of CNC tools can effectively prevent the damage of cutting tools, prevent the decline of cutting quality, and better control the cost of production and manufacturing.
To sum up, the selection of CNC tools has the most significant impact on its technological performance. Therefore, in actual production, workers need to choose the most appropriate method, which coincides with the selection criteria of cutting tools. Ensure the smooth operation of CNC machining process. In this case, professional and technical workers should master the characteristics and use of each tool. Only in this way can they select the most suitable CNC tool according to the actual situation. Through the analysis of the CNC machine tool, the quality of the CNC processing technology can be improved in an all-round way, which plays a role in promoting the mechanical manufacturing, so as to achieve the purpose of improving the level and efficiency of the mechanical manufacturing.