Analysis of high-speed CNC machining technology overview

Paper Keywords: CNC high speed machining Technology, CNC machining Technology

Abstract: High-speed cutting Technology is the inevitable trend of machinery manufacturing Industry, its application will greatly improve processing efficiency and processing quality of high-speed cutting Technology is not only related to the high-speed machining Technology and high-speed cutting mechanism, but also high-speed cutting tool with the , machine tools and many other factors. This article focuses on high-speed cutting of the dynamic-related technology research, and high-speed cutting technology prospect.


First, the advantages of high speed machining technology

High-speed machining in the cutting principle is a breakthrough in understanding the traditional cutting. According to information in foreign high-speed machining trials have confirmed that when the cutting speed exceeds a certain value (V = 600m/min), the cutting speed and then increased, cutting temperature but lower in the cutting process heat from the workpiece into the cutting and place were taken away. experimental conditions, the test demonstrated that in most applications, cutting the workpiece temperature rise no more than 3 ℃. Accordingly, the has been given metal removal rate, when the cutting speed exceeds a certain value, the actual cutting force will be approximately unchanged.

After the ideal high-speed machining, the chip deformation and contraction process of implementation and application of the aviation Industry has an important significance. High-speed machining itself must be a coordination of all relevant elements of the system is more comprehensive application of advanced technologies for The machine manufacturer should be vigorously developed, introduced and new technologies related to high-speed processing equipment.


Second, the current development of CNC high speed machining

Practical high-speed processing technology to follow the introduction of advanced CNC automatic production line, tool (tool), CNC machine tools (equipment), widely used in mechanical manufacturing Industry, the appropriate management, technology, philosophy along with integration into the enterprise in China's space, aviation, turbine, mold and other industries, different levels of application of high-speed processing technology, the gap between the state of the Industry is invested, how much support the introduction of policies, as well as entrepreneurs of high-speed processing system the depth of technical understanding. relative to the automobile manufacturing Industry, such machinery manufacturing industry is essentially discrete manufacturing process its characterization of high-speed machining technology mainly in high-speed CNC machine tools and tool technology, which currently has the introduction of domestic processing centers, CNC boring, Milling spindle speed is generally ≤ 8 000r/min (rarely 12 000r/min), fast-forward speed ≤ 40m/min. of aluminum, wrought aluminum alloy body, high-strength cast iron and structural steel, the use of ultra-fine hard alloy, coated cemented carbide tool material and the structure of various types of standard tooling. superhard cutting tool materials and tool-specific applications have less structure, coupled with low spindle speed, generally can not enter the field of high-speed cutting. by milling, for example These aluminum parts processing industry: cutting speed <1 000m/min, feed rate <15m/min, feed per tooth volume of <0.35mm. turning: cutting speed <700m/min. milling cast iron, structural steel (including stainless steel ) parts: cutting speed <500m/min, feed rate <10m/min, feed per tooth volume of <0.3mm. the industry, CNC equipment utilization rate is only about 25%. Expected to "15" period, the industry will be in the application of high-speed processing technology have taken place in the progress and development by leaps and bounds.


Third, high-speed CNC machine tools of the key technologies

High-speed high-speed cutting machine is a prerequisite and key high-speed spindle with high accuracy with high precision control of high-axial feed rate and feed acceleration of axial feed system is the key to high-speed machine tools. are as follows:
1 high-speed spindle
High speed cutting spindle is one of the most critical components present in the spindle speed 10 000 ~ 20 000 r / min machining centers is becoming increasingly popular, the speed up to 100 000 r / min, 200 000 r / min, 250 000 r / min practical high-speed spindle is also being developed in high speed high speed spindle, spindle parts under the centrifugal force vibration and deformation, high-power built-in high speed friction and heat generated by the motor will cause high temperatures and deformation, it must be strictly controlled. as This high-speed spindle to make the following performance requirements: (1) high speed and high-speed range; (2) sufficient rigidity and high precision rotary; (3) good thermal stability; (4) power; (5) advanced lubrication and cooling systems; (6) reliable spindle monitoring system.

2 fast feed system
High-speed cutting, in order to maintain the tool feed rate per tooth is essentially the same, with increased spindle speed, feed rate must also dramatically improve present high-speed cutting feed speeds of up to 50m/min ~ 120m/min, to and precise control to achieve such a feed speed of the machine guides, ball screws, servo systems, table structure and put forward new demands, and, because the machine is generally a shorter trip on the linear motion, high-speed machine tools to achieve higher acceleration and deceleration of the feed makes sense. In order to meet the feed requirements of high-speed movement, high-speed machine tools mainly on the following measures: (1) using a new linear motion guide, linear motion guide rail and steel ball bearings in contact area between the small, the friction coefficient of slotted rails 1 / 20 or so, and the use of linear motion guide, the "crawling" phenomenon can be greatly reduced; (2) high-speed feeding of large-size organizations with small pitch high-quality ball screw or ball screw coarse pitch long, and its purpose is not to reduce the accuracy of the premise to obtain a higher feed rate and feed rate of addition and subtraction; (3) high-speed feed servo system has been developed for the digital, intelligence and software, high-speed cutting machine tools has started all-digital AC servo motor and control technology; (4) In order to minimize the table but not the weight loss of stiffness, high-speed feed mechanism is usually made of carbon fiber reinforced composite materials; (5) To improve the feed rate, more advanced, more high-speed linear motor has been developed. linear motor eliminates the mechanical transmission of the gap, elastic deformation and other problems, reducing the friction drive, almost no backlash. linear motor with high acceleration and deceleration characteristics, acceleration up to 2g, for the traditional drive of 10 to 20 times the feed rate of the traditional 4 to 5 times, with linear motor drive, the thrust per unit area with a large, easy to produce high speed, the mechanical structure is not need to maintain the obvious advantages.

Links to free download http://www.hi138.com 3. High-speed cutting tool technology
(1) tool materials requires high-speed cutting tool material and processed materials of chemical affinity is smaller, and has excellent mechanical properties and thermal stability, impact resistance, wear now commonly used in high-speed cutting tool material single or multi-coated cemented carbide coatings, ceramics, cubic boron nitride (CBN), polycrystalline diamond and so on.

(2) high-speed cutting tool structure. High-speed centrifugal force caused by high-speed cutting in bending strength and fracture toughness will have a lower blade fracture, in addition to damage to the workpiece, the machine will be the operator and dangerous, so In addition to high-speed cutting tools to meet the balance between static balancing must also meet the requirements. Balancing the general requirements of small-diameter tool lax on the large-diameter cutter or disc-type knives demanding. Overhang longer tool, balancing the need for addition need the tool, chuck, spindle, etc. balance each component separately , but also the tool and chuck combination to balance. Finally, the tool spindle together with balance, but balance is still no uniform standard of ISO1940-1 standard in the balance of mass G is balanced standards have different views Some enterprises to G1 as a standard (the so-called G1, that is, at 10 000r/min rotary cutter, the rotary axis and tool center only difference between the 1Lm), some of the G215 standard.

(3) high-speed cutting tool geometry. High-speed cutting tool edge shape is toward the high-rigidity, composite, multi-edge and surface super-finishing direction. Tool geometric parameters on processing quality, tool life has a great impact on the general high-speed cutting tool rake angle than the average small traditional cutting tools 10b, about big horn 5b ~ 8b. In order to prevent thermal wear at the tip, the main and secondary cutting edge rounding should be used to connect at the tip or bevel tip, in order to increase the knife sharp corners and increase knife near the blade tip area the length of the cutting edge to improve cutting tool rigidity and reduce the probability of blade breakage.

(4) high-speed cutting tool holder system machining center spindle and tool connection they use 7B24-sided clamping taper shank system, ISO, CAT, DIN, BT, etc. fall into this category. Used in high speed machining, which class system in a number of issues, mainly as follows: lack of rigidity, ATC (automatic tool change) the repeatability of instability, influenced by the effect of centrifugal force, Taper, it is not conducive to rapid tool change and the miniaturization of machine tools. To solve these problems, to improve the connection between the tool and spindle rigidity and clamping accuracy, high speed machining technology to adapt to the needs of development, have developed a knife handle and the spindle bore taper and end at the same time snapping both sides of the positioning of the knife handle. on both sides Positioning handle are two major categories: one is for the existing 7B24 taper shank design improvements, such as BIG-PLUS, WSU, ABSC systems; the other is the use of new ideas designed 1B10 short hollow cone knife handle system, there developed in Germany HSK, KM and the development of the United States developed in Japan NC5 several forms.

4 high-speed cutting process
High-speed cutting with high efficiency, high precision, single-piece processing and low cost. High-speed machining and conventional machining processes are different, that the traditional processing, high efficiency from low speed, large depth of cut, creep feed, single stroke, In the high-speed processing, high speed, the depth of cut, fast-forward to more travel is more favorable. high-speed cutting as a new cutting method is currently no complete the processing parameter table to choose from, there is no more processing examples for reference, has yet to establish a database of practical high-speed cutting, high-speed machining process parameters optimization, but also a lot of work needs to be done. HSM NC programming standard operating procedures need to be modified. part program requires precise and must ensure stable cutting load Most automatic CNC programming software still can not meet the requirements of high-speed machining, need to be supplemented by a manual programming. should adopt a new way of programming, the cutting data for high-speed spindle power curve now, Cimatron, Mastercam, UG, Pro / E and other CAM software, have been added for high-speed cutting programming module.

5 high-speed machine bed, column and table
Through computer-aided engineering methods, especially the use of finite element optimal design can be to reduce weight and improve rigidity of the bed and table.


IV Conclusion

High-speed machining technology is one of the modern advanced manufacturing technology, which produces a variety of economic globalization and the market development of the combined result of advanced technology in this context, high-speed processing technology came into being, and gradually developed into a comprehensive systems engineering, and to be more widely used. The great attraction of high-speed machining is to achieve high-speed processing, while ensuring high-speed precision. aerospace, automotive and high-speed machining of mold manufacturing industry recognition and strong demand, driving high-speed machining technology international development.


References:
[1] Bin Hongzan. CNC machining process [M]. Wuhan: Huazhong University Press, 2004.

[2] Zhu Xiaochun. CNC Technology [M]. Beijing: Mechanical Industry Press, 2004.

[3] Zhou Zheng dry, Wangmei Qing, Li Heping. The core of high-speed machining techniques and methods [J]. Aeronautical Manufacturing Technology, 2000 (3) Links to free download http://www.hi138.com