The application of PARA tool in graphite machining
Graphite electrodes have the advantages of small consumption of electrode, fast machining speed, good machinability, high machining accuracy, small thermal deformation, light weight, easy surface treatment, high temperature resistance, high machining temperature, and electrode bonding, etc., when compared to copper electrode. Advantages. Although graphite is a very easy to cut material, but because the graphite material used as EDM electrodes must have enough strength to avoid damage in the operation and EDM process, at the same time, the shape of the electrode (thin-walled, small rounded corners, sharp), etc. also puts forward high requirements on the grain size and strength of graphite electrodes, which leads to graphite workpiece is easy to crumble in the process, the tool is easy to wear.
Tool wear is the most important problem in graphite electrode processing. The amount of wear not only affects the cost of tool loss, processing time, processing quality, but also affects the surface quality of the electrode EDM machining workpiece material, which is an important parameter for optimizing high-speed machining. The main tool wear areas for graphite electrode material machining are the front tool face and the back tool face. On the front tool face, the impact contact between the tool and the broken chip area produces impact abrasive wear, and the sliding chips along the tool surface produce sliding friction wear.
The impact of tool wear a few things:
1, tool material
Tool material is the fundamental factor in determining the cutting performance of the tool, for machining efficiency, machining quality, machining costs and tool durability has a great impact. The harder the tool material, the better its wear resistance, the higher the hardness, the lower the impact toughness, the more brittle the material. Hardness and toughness is a pair of contradictions, but also the tool material should overcome a key. For graphite tools, ordinary TiAlN coating can be appropriate in the selection of toughness is relatively better, that is, the cobalt content is slightly higher; for diamond-coated graphite tools, can be appropriate in the selection of hardness is relatively better, that is, the cobalt content is slightly lower;
PARA cutting tools combined with many years of experience in the selection of the European famous brand of cutting tool materials.
2, tool geometry
Graphite tools to choose the right geometry angle, help reduce the vibration of the tool, in turn, the graphite workpiece is not easy to chipping;
(1) the front angle, the use of negative front angle graphite machining, the cutting edge of the tool edge strength is better, impact resistance and friction performance is good, with the reduction of the absolute value of the negative front angle, the rear face of the wear surface area does not vary much, but the overall trend is decreasing, with a negative front angle of the graphite cutting edge strength, impact resistance and friction performance is good. With the decrease of the absolute value of the negative rake angle, the wear area of the back face does not change much, but the overall trend is decreasing. When machining with a positive rake angle, the strength of the cutting edge of the tool is weakened by the increase of the rake angle, which leads to the increase of the back face wear instead. Negative front angle machining, cutting resistance is large, increasing the cutting vibration, using a large positive front angle machining, tool wear is serious, cutting vibration is also larger.
(2) rear angle, if the rear angle of the increase, the tool edge strength is reduced, the rear face wear area gradually increased. After the tool rear angle is too large, the cutting vibration is strengthened.
(3) helix angle, helix angle is small, the same cutting edge at the same time cut into the graphite workpiece on the edge of the longest, cutting resistance is the largest, the tool to withstand the cutting impact is the largest, and therefore the tool wear, milling force and cutting vibration is the largest. When the helix angle to go larger, the direction of the milling force deviates from the surface of the workpiece to a large extent, the graphite material due to the cutting impact caused by the collapse of increased, and thus tool wear, milling force and cutting vibration have increased.
Therefore, the influence of tool angle change on tool wear, milling force and cutting vibration is produced by the combination of the front angle, the back angle and the helix angle, so more attention must be paid to the selection.
By doing a lot of scientific tests on the machining characteristics of graphite materials, PARA tools optimize the relevant tool geometry angle, which makes the overall cutting performance of the tool greatly improved.
3, tool coating
Diamond coated tools have the advantages of high hardness, good wear resistance, low coefficient of friction, etc. At this stage, diamond coating is the best choice for graphite processing tools, which also best reflects the superior performance of graphite tools; diamond coated carbide tools have the advantage of integrating the hardness of natural diamond and the strength and fracture toughness of cemented carbide; however, in the Domestic diamond coating technology is still in its infancy, as well as the cost of investment are very large, so diamond coating in the near future will not have much development, but we can be in the ordinary tool on the basis of optimizing the angle of the tool, the selection of materials and other aspects and improve the structure of the ordinary coatings, to a certain extent, it can be applied in graphite processing.
The geometric angle of diamond coated tools and ordinary coated tools are fundamentally different, so in the design of diamond coated tools, due to the specificity of graphite processing, the geometric angle can be appropriately enlarged to accommodate the cutting groove is also larger, and will not reduce the abrasion resistance of its tool sharpness; for the ordinary TiAlN coating, although more than the uncoated tool has a significant increase in wear resistance, but compared to the diamond coating, in the processing of graphite, the diamond coating can be applied in the processing of graphite, but it can be used in the processing of graphite, but it can also be used in the processing of graphite. For ordinary TiAlN coating, although it has a significant increase in wear resistance than the uncoated tool, but compared to the diamond coating, its geometric angle should be appropriately reduced when machining graphite in order to increase its wear resistance.
For diamond coating, many coating companies in the world have invested a lot of manpower and material resources to research and develop the relevant coating technology, but so far, foreign mature and economic coating companies are only limited to Europe; PARA, as an excellent graphite processing tools, the same use of the world's most advanced coating technology on the surface of the tool to ensure that the machining life of the At the same time, to ensure that the tool is economical and practical.
4, tool edge strengthening
Tool edge passivation technology is a tool edge is not yet generally valued, but is a very important issue. Diamond grinding wheel sharpened carbide tool edge, there are varying degrees of microscopic gaps (i.e., tiny chipping and saw kerf). Graphite high-speed cutting and machining tool performance and stability put forward higher requirements, especially diamond coated tools in the coating before the cutter must be passivated to ensure the firmness of the coating and service life. The purpose of tool passivation is to solve the above mentioned defects of microscopic notches on the cutting edge of the tool after sharpening, so that its edge value is reduced or eliminated to achieve the purpose of rounded and smooth, both sharp and strong and durable.
5, tool machining conditions
Select the appropriate processing conditions for the life of the tool has a considerable impact.
(1) cutting mode (smooth milling and reverse milling), smooth milling cutting vibration is less than the reverse milling cutting vibration. Shun milling tool cutting thickness from the maximum reduced to zero, the tool cut into the workpiece will not appear because of cutting chips caused by the phenomenon of popping knife, the rigidity of the process system is good, cutting vibration is small; reverse milling, the tool cutting thickness from zero to the maximum, the tool cuts into the initial period due to the thin thickness of the cutting will be in the surface of the workpiece scratches a section of the path, at this time, if the edge encountered in the graphite material in the hard point or residual chip particles in the workpiece surface, will cause the tool to be cut into the surface, the cutting vibration will be less than the cutting vibration, and the cutting vibration will be less than the cutting vibration. Chip particles, will cause the tool popping or chattering, so the cutting vibration of reverse milling;
(2) blowing (or vacuuming) and impregnated with EDM fluid processing, timely cleanup of the graphite dust on the surface of the workpiece, which is conducive to reducing the secondary wear of the tool to extend the tool's service life, and to reduce the impact of the graphite dust on the machine tool screws and guideways;
(3) select the appropriate high speed and corresponding large feed.
Summary of the above points, the tool material, geometric angle, coating, edge strengthening and machining conditions, in the service life of the tool plays a different role, indispensable and complementary. A good graphite tool should have a smooth graphite powder chip removal groove, long service life, able to deep carving processing, can save processing costs.
6, application examples
Workpiece size: 600 × 400 × 90
Graphite material: ISO-63 (Toyo Carbon)
Electrode shape: home appliances cooling outer cover
Tools used: PARA ￠6 RO (finishing the bottom)
PARA ￠6 R3 (finishing the side walls)
S=17 000 F= 6000mm/min
Machining time: 15 hours of continuous machining
Wear condition: the tip of the blade <0.02mm, coating intact
S=17 000 F= 6000mm/min
Machining time: 8 hours of continuous machining
Wear condition: the tip of the blade <0.02mm, coating intact
Wear condition: the tip of the blade Tip<0.03mm
/qikan/periodical.Articles/tsjs/tsjs99/tsjs9901/990107.htm
Introduction of Numerical Control Graphite Electrode Processing Line
WANG Mingqi
INTRODUCTION OF NUMERICAL CONTROL TECHNIQUE IN MACHINING PROCESS OF GRAPHITE ELECTRODES
Wang Mingqi
(Jilin Carbon Group Co Ltd,Jilin 132002)
1 Preface
Since the 1970s, the rapid development of microelectronics technology, represented by large-scale integrated circuits and microelectronic computers, has been rapidly applied to production practice, with the emergence of a wide variety of computer-controlled machine tools and automated production lines with flexible functions. CNC machine tools are a kind of mechatronics equipment. The so-called numerical control is digital control, according to the production of the program using electronic computers to carry out digital calculations, and then control the production process in order to realize the production process automation of a technology. With the development of electronic computers, the application of numerical control technology is becoming more and more popular, one of the aspects of the development of a particularly rapid, is the CNC machine tools.
The machining of graphite electrodes is the last process of graphite electrode production, and its processing method is similar to that of metal products. CNC electrode machining machine tools have become an important development direction for electrode machining machine tools due to their high efficiency, high precision, high degree of automation and ease of adjustment.
Carbon enterprises from the late 80s began to use CNC electrode processing machine tools, such as Jilin Carbon Group Co., Ltd. and Lanzhou Carbon Co., Ltd. at the same time the introduction of the U.S. Ingersoll company manufactured by the CNC electrode machining automatic line (hereinafter referred to as the U.S. line), and then Jilin Carbon Group Co., Ltd. and the introduction of Japan's FUJIKOSHI manufactured by the CNC electrode machining automatic line (hereinafter referred to as the Japanese line). (hereinafter referred to as Japanese line). From the use of the situation, the effect is obvious, not only reduce the labor intensity of workers, improve the production environment, improve labor productivity, but also due to the use of CNC technology, so that the processing quality of graphite electrodes significantly improved.
2 Mechanical Processing of Graphite Electrodes
After the graphite electrode is pressed, its size and shape have been determined, but after the raw products after pressing are roasted and graphitized, due to a certain degree of deformation, and some filler and other impurities are adhered to the surface, it appears to be irregular in shape and the surface is rough and uneven, which can not meet the requirements for use, and it has to be mechanically processed before it can be It must be mechanically processed in order to be used.
The mechanical processing of graphite electrode includes boring, turning and milling threads, which is similar to the processing of metal products. According to the production characteristics of graphite electrode machining, CNC electrode machining machine tools generally adopt a 3-unit structure to complete boring, turning and milling threads respectively.
The first process of graphite electrode machining is boring and rough flattening of the end face, the cutting amount of the end face is generally set to less than 30mm, after boring, the hole wall is required to leave a certain amount of machining allowance for milling threads, about 2mm.
After boring and rough flattening of the end face, the machining of the outer circle, the machining amount of the outer circle is generally less than 15mm.
The process is simple, as long as the adjustment of the outer circle, the machining tool to meet the machining of the outer circle, the machining of the outer circle, the machining tool to meet the machining requirements. The process is simple, as long as the adjustment of the external turning tool to meet the processing quality requirements can be.
The most important process of graphite electrode machining is thread milling, the quality of which is directly related to the use of graphite electrodes. In the processing of milling threads, there are strict requirements for the taper, aperture and buckle shape of the threads, and connection test should be carried out.
3 CNC technology in graphite electrode machining applications
3.1 Structure of CNC electrode machining machine
CNC electrode machining machine consists of CNC (CNC), servo system and machine body 3 parts, as shown in Figure 1.
Figure 1 structure of CNC processing machine tools
The reliability of CNC machine tools depends mainly on the CNC system, the development direction of the CNC system is to improve the processing speed and control accuracy, enhance the ability to enhance anti-interference, increase the reliability, reduce the size and so on. "Japan line" machine tool FANUC-18TEA CNC system and "U.S. line" machine tool AB-7360 CNC system compared to these aspects are greatly improved.
Servo system is also called the actuator, its performance directly affects the machining accuracy, feed speed and productivity. Servo system according to the control principle of open-loop, semi-closed-loop and fully closed-loop system; according to the implementation of the components used in hydraulic servo, DC electric servo and AC electric servo system. Early introduction of CNC electrode machining machine tools more than the use of hydraulic servo system drive, sensor positioning, only in the high-precision milling thread workstation using DC electric servo system drive. A new generation of CNC electrode processing machine tools all use AC electric servo system with ball screw drive, increase centering, length measurement system, so that the design structure greatly improves the positioning accuracy of the processing system and machining accuracy.
CNC electrode machining automatic line of the machine tool body part of the general design of the structure of the three units, respectively, to complete the boring, turning and milling threads.
3.2 Two processing methods of graphite electrode threads
The most important process of graphite electrode machining is milling threads, which can be attributed to two processing methods from the viewpoint of CNC electrode processing machine tools used in domestic carbon factories at present: one is the "U.S. line" made by Ingersoll of U.S.A., and the other is the "U.S. line" made by FUJIKOSHI of Japan, which is the "U.S. line" made by FUJIKOSHI of Japan. Japan's Fujikoshi company made the "Japanese line".
Ingersoll designed and manufactured by the United States of America, this CNC electrode machining machine adopts the following machining method: as shown in Figure 2, the beginning of the process, the spindle equipped with a comb knife to the electrode center axis as the center of the rotation at a speed of 60r/min, while the processing tool in the control of the CNC, through the x-direction and z-direction synthetic movement to complete the processing of threads. During the whole machining process, the electrode remains motionless. The US wire machine adopts multiple cycles to complete the thread machining of one electrode, taking the spindle rotation of 720° as a single cycle. In order to ensure the quality of machining, the number of cycles can be selected, generally 9 cycles are used, and the amount of feed for each cycle is decreasing, with the last feed as the minimum to ensure the finish of the thread.
Figure 2: Principle diagram of thread milling of "American Line" machine tool
The disadvantage of this method is that the completion of thread processing of an electrode requires frequent reciprocating movements of x-axis and z-axis, which greatly increases the workload of CNC and servo system, and the finish of the thread is not good, although the number of cycles can be increased to improve the finish of the thread. Although the thread finish can be improved by increasing the number of cycles, it will increase the cycle time and reduce the working efficiency. CNC electrode processing machine tools after more than twenty years of development, processing methods have become more mature, the current CNC electrode processing machine tools are mostly used in the "daily line" processing method.
"Japanese" machine tool electrode thread processing method and "American line" is very different, it is in the milling thread process using the processing method is: the electrode itself to 1.8r/min speed rotation, the processing tool to 1000r/min speed of high-speed rotation, while machining At the same time, the tool rotates at a speed of 1000r/min, and the threading process is completed by the synthesized movement in the x-direction and z-direction under the control of CNC, and the electrode rotates by 365° during the whole process. As shown in Figure 3, OO′ is the centerline of electrode rotation, PP′ is the centerline of tool rotation, and PP′ varies with the z-direction movement of the tool.
Figure 3 "Japanese line" machine tool milling thread machining schematic
3.3 Workpiece program design
FANUC CNC control system of CNC electrode machining automatic line made by Japan's FUJIKOSHI company as an example, to study the design of the workpiece program.
3.3.1 Boring and rough flattening the end face
The 1st process of graphite electrode machining is boring and rough flattening the end face. As shown in Fig. 4 is the x-axis controlled by CNC, L1 is the distance of the bottom tool of the hole from the surface of the blank, which is calculated from the data of centering and length measurement, L2 is the depth of the hole, and L3 is the cutting amount set by digital switch. The machining process is as follows:
Figure 4 Schematic diagram of the boring and rough flattening end face machining process
The machining starts with the x-axis fast positioning, the hole bottom cutter is close to the surface of the electrode, and then the x-axis starts to work into the x-axis, and the work into the x-axis is generally used in 2 feed speeds, first at 400mm/min, and then when the end face cutter starts to process, the cutting volume increases and feeds at 200mm/min.
At the end of machining, the spindle stops, the x-axis returns to zero, and then starts the next cycle. The program is as follows:
N010 #501=L1;
N020 #502=L1 + L2;
N030 #503=L1 + L2 + L3;
N040 M15; (Spindle Rotation)
N050 G90G00X-#501;
N060 G01X-#502F400;
N070 G01X-#503F200;
N080 M11; (spindle stop)
N090 G90G00X0.0;
N0100 M30 ;
This process is simple to process, CNC control of one axis can be completed, in the case of hardware system functions are available, the workpiece program can be prepared very simple.
3.3.2 Fine Flat Face and Milling Threads
As shown in Figure 5 is the machining schematic diagram of the fine flat face, #100 is the x-axis positioning value, #110 is the y-axis positioning value, #111 is the y-axis end position value. The machining process is as follows:
Figure 5 Schematic diagram of the machining process of fine-flat endface
Machining starts, the x-axis is quickly positioned, then the clamp clamps the electrode, the spindle motor drives the electrode to rotate at a speed of 12r/min for fine-flat endface. The fine leveling of the end face starts, the y-axis is quickly positioned, and then the work is carried out, the feed speed is 180mm/min, and the processing time is 5s. After the fine leveling of the end face is finished, the y-axis returns to zero point.
The program is as follows:
N010 M16; (spindle orientation)
N020 M98P1632; (tuning subroutine)
N030 G00X-#100;
N040 M10; (clamping electrodes)
N050 S60M03 ;
N060 G00Y-#110;
N070 G01Y-#111F180;
N080 G04X5.0;
N090 G28Y0;
The process of milling threads is shown in Figure 6.
Fig. 6 Schematic diagram of thread milling process
Description: x-axis rapid traverse is #122=-10mm, time 2s, 2s spindle rotates 1.8/60*2 revolutions, so the z-axis rapid traverse should be #123=8.4667*1.8*2/60/COS (9.462322) mm, feed rate #127=10.8*2/60/COS (9.462322) mm, and feed rate #127=10.8*2/60/COS (9.462322) mm. Feed speed #127=10/(1.8*2/60). 365° milling thread, z-axis feed amount should be #124=8.4667*365/360/COS(9.462322), feed speed #128=8?4667/COS(9.462322) mm/r. Fast backturn amount is the same as fast draft amount.
Start thread milling, x-axis fast positioning to milling thread position, z-axis fast positioning to 50mm from the machining position, and then work into the machining position, the feed rate is 500mm/min. start milling thread, spindle speed is 1.8r/min, x-axis and z-axis fast tool eating, and then 365 ° thread milling, x-axis and z-axis fast retract.
When the thread milling is finished, the clamping device is released and the axes return to zero, ready to start the next cycle. The program is as follows:
N110 M15;
N120 G00X #120;
N130 G00Z [-#129 + 50];
N140 G01Z-#129F500;
N150 S9M03;
N160 G99G32X #122Z #123F #127;
N170 Z #124F #128;
N180 X #125Z #126F #127;
N190 G98G28Z0;
N200 G00X0;
< p> N210 M30;Dateline adopts a new processing method, which improves the processing quality of graphite electrodes, and quality problems are easy to find and correct.
4 Analysis of the use of CNC electrode processing machine tools
The introduction of the "U.S. line" not only reduces the labor intensity of workers, improve the production environment, but also make the electrode yield and quality has improved substantially, to meet the requirements of modernization and large-scale production. The "American line" can process electrodes with a diameter of 250-800mm. In order to expand the scale of production, Jilin Carbon Group Co., Ltd. introduced a CNC electrode processing automatic line from Japan Fujikoshi Company in 1995. This set of CNC machining system, whether it is the CNC device, servo system, or the overall design level of the machine tool represents the international advanced level of CNC electrode processing machine tools in the 1990s. The "Japanese line" can process electrodes with a diameter of 400-700mm, and now it has been modified to have the ability to process deep hole electrodes. "The machine was put into production in April, 1996, and has been running well. Graphite electrode machining the most important process is milling threads, "Japan line" product threads, whether taper, aperture or finish are better than past products, and "Japan line" installed with a very strong operating system, problems are easy to correct.
5 Conclusion
China's carbon industry from the 1950s to the present has been developed for more than 40 years, in the past, most of the carbon plant there is a low degree of automation of the equipment, aging problems, since the reform and opening up, many of the large carbon plant to introduce and develop a lot of modern equipment, the use of the effect is obvious. In terms of mechanical processing of electrodes, the design level of domestic processing line and manufacturing process is not yet pass, there is a low degree of automation, processing quality is not good, low productivity and high failure rate shortcomings, and some even failed to form production capacity. It is hoped that the discussion in this paper can promote and facilitate the development of domestic electrode processing machine tools.
Author: Wang Mingqi male born in October 1968, electrical engineer. 1991 graduated from Huazhong University of Science and Technology, Department of Electronics. He is now working in Jilin Carbon Group Co., Ltd. three zero four workshop, engaged in automated machine tool computer control system maintenance and management, completed more than 10 technical innovation projects.
Author: Wang Mingqi (Jilin Carbon Group Co., Ltd. Jilin 132002)
References
[1] Wu Zuyu, Qin Pengfei? CNC Machine Tools? Shanghai: Shanghai Science and Technology Press, 1990
[2] Wu Jiliang, Li Xiangkun? Microcomputer application of one hundred cases? Beijing: Machinery Industry Press, 1985
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Talking about graphite electrodes in the mold processing applications
www.zs91.com Source: "CADCAM and Manufacturing Information Technology Time: 2006-4-12
In recent years, with the introduction of precision molds and high-efficiency molds (mold cycle is getting shorter and shorter), people are increasingly demanding mold production, due to the copper electrode itself, the limitations of various conditions, has been more and more unable to meet the requirements of the development of the mold industry. Graphite as EDM electrode material, with its high cutting, light weight, fast forming, expansion rate is very small, small loss, easy to repair and other advantages, has been widely used in the mold industry, instead of copper electrode has become inevitable.
I. Graphite Electrode Material Characteristics
1. Fast CNC machining speed, high cutability, easy to trim
Graphite machining speed is fast, for the copper electrode 3 to 5 times, finishing speed is particularly prominent, and its strength is very high, for ultra-high (50 ~ 90mm), ultra-thin (0.2 ~ 0.5mm) electrode, processing is not easy to deformation. And in many cases, the product is required to have a very good grain surface effect, which requires the electrode made as far as possible into the overall male electrode, and the overall male electrode production of all kinds of hidden clear angle, due to the graphite easy to trim the characteristics of this problem can be easily solved, and greatly reduces the number of electrodes, while the copper electrode can not be done.
2. Fast EDM molding, small thermal expansion, low loss
As the conductivity of graphite is better than copper, so its discharge rate is faster than that of copper, 3 to 5 times as fast as copper. And its discharge can withstand the larger current, EDM roughing more favorable. At the same time, under the same volume, graphite weight is 1/5 times of copper, greatly reducing the load of EDM. It is very advantageous for making large electrodes and overall male electrodes. The sublimation temperature of graphite is 4200℃, which is 3~4 times that of copper (the sublimation temperature of copper is 1100℃). Under high temperature, the deformation is extremely small (1/3~1/5 of copper under the same electrical conditions) and does not soften. The discharge energy can be transmitted to the workpiece with high efficiency and low consumption. As graphite strength is rather enhanced at high temperature, it can effectively reduce the discharge loss (graphite loss is 1/4 of copper) and ensure the processing quality.
3. Light weight, low cost
A set of mold production costs, the electrode CNC machining time, EDM time, electrode loss accounted for the vast majority of the overall cost, and these are determined by the electrode material itself. Graphite compared with copper, graphite machining speed and EDM speed are 3 to 5 times that of copper. At the same time, the characteristics of minimal wear and the overall male graphite electrode production, can reduce the number of electrodes, which also reduces the electrode consumables and machining time. All of these, can greatly reduce the cost of making molds.
Second, graphite electrode electromechanical processing requirements and characteristics
1. Electrode production
Professional graphite electrode production is mainly used in high-speed machine tools to process, the stability of the machine tool should be good, the three-axis movement should be uniform and stable without vibration, and like the spindle of these rotary precision as well as as possible good. The general machine tool can also complete the processing of electrodes, only the preparation of the knife path of the process is different from the copper electrode.
2. EDM
Graphite electrodes are carbon electrodes. Because graphite has good electrical conductivity, it saves a lot of time in EDM, which is one of the reasons for using graphite as an electrode.
3. Characteristics of graphite electrode machining
Industrial graphite is hard and brittle, and the wear of the tool is more serious in CNC machining, and it is generally recommended to use carbide or diamond-coated tools. Graphite in roughing the tool can be directly in the workpiece under the knife, finishing in order to avoid the occurrence of chipping, cracking, often use a light knife fast way of processing. Generally speaking, graphite in the depth of cut less than 0.2mm rarely occurs in the case of chipping, will also obtain a better sidewall surface quality. Graphite electrode CNC machining dust is relatively large, may invade the machine tool guide screw and spindle, etc., which requires graphite processing machine tools have the appropriate treatment of graphite dust device, machine tool sealing should also be good, because graphite is toxic.
Third, the processing of graphite electrode examples
As shown in Figure 1 is the hanging panel injection mold fixed mold core graphite electrode, the blank size of 182mm × 42mm × 65mm, the middle of the maximum width of the small groove 3.1mm, the maximum depth of the groove is 5.1mm, the overall machining height of 64mm.
This type of electrode is medium-sized external dimensions, shape More complex, in the graphite electrode for the more common model. The entire model was CNC machined using Wildfire 2.0 in Pro/ENGINEER, however, it was soaked in kerosene for a few hours prior to machining to reduce its brittleness. Due to the small and irregular intermediate slots, the machining strategy of CAM is to rough the overall shape, then finish the shaped surface and the lower connected surface, then rough the small intermediate slots, and finally finish the small intermediate slots.
Figure 1 Graphite electrode for the fixed mold core of the injection mold for the panel of the hook-up machine
1. Overall rough machining
Using D20 (R1) coated insert milling cutter, adopting spiral machining mode (TYPE_SPIRAL), the depth of cut (STEP_DEPTH) is 0.35mm, the step spacing (SIDE_STEP) is 8mm, and the contour allowance (PROF_STOCK_ALLOW) is 0.5mm. STOCK_ALLOW) 0.35mm, Roughing allowance (ROUGH_STOCK_ALLOW) 0.35mm, Bottom allowance (BTTOM_STOCK_ALLOW) 0.35mm, Machining mode (ROUGH_OPTION) ROUGH_ONLY, Safe height (CLEAR_DIST) 5mm. Spindle speed (SPINDLE_SPEED) 2500r/min, feed speed (CUT_FEED) 800mm/min.
Using the Screen Play function, the machining tool trajectory is shown in Figure 2.
Figure 2 Roughing the overall profile
Meanwhile, the machining is checked by simulation simulation (NC Check) and overcut check (GougeCheck). The milling cutter did not enter the interior of the intermediate slot, and the entire electrode profile was milled out in accordance with the process. Exit by the completion sequence (DoneS w q). The time calculated by the program is 50s, and the machining time is 2.1h.
2. Finishing I
Finishing is done by using a D16 (R8) ball end milling cutter with surface milling (SurfaceMilling), with a step spacing (SIDE_STEP) of 0.2mm, a contour allowance (PROF_STOCK_ALLOW) of - 0.25mm, cutting angle (CUT_ANGLE) 45°, machining type (SCAN_TYPE) TYPE_3, safety height (CLEAR_DIST) 5mm, spindle speed (SPINDLE_SPEED) 2500r/min, feed rate (CUT_FEED) 650mm/min. Using the Screen Play function, the machining toolpath is displayed. Screen Play) function, the machining tool trajectory is shown in Figure 3. At the same time, the machining is checked by simulation (NC Check) and overcut check (Gouge Check). The milling cutter does not enter the interior of the intermediate slot, and the negative allowance (spark gap, i.e., the amount of rocking) for machining the molded surface defined on the outside of the slot is removed, which is in accordance with the process requirements. Exit by completion sequence (Done Swq). The program calculates a time of 130s, and the machining time is 1.5h.
Figure 3 Finishing a molded surface
3. Finishing II
Using a D20 (R1) coated insert milling cutter, machining type (SCAN_TYPE) TYPE_2, depth of cut (STEP_DEPTH) 0.35mm, step (SIDE_STEP ) 8mm, contour allowance (PROF_STOCK_ALLOW) -0.25mm, roughing allowance (ROUGH_STOCK_ALLOW) 0.35mm, bottom allowance (BTTOM_STOCK_ALLOW) 0mm, machining mode (ROUGH_OPTION) PROF_ONLY, safety height ( CLEAR_DIST) 5mm, spindle speed (SPINDLE_SPEED) 2500r/min, feed speed (CUT_FEED) 800mm/min. Using the Screen Play function, the machining tool trajectory is shown in Figure 4. At the same time, the machining is checked by simulation (NC Check) and overcut check (Gouge Check). The milling cutter performs side machining and the electrode side is milled in place to meet the requirements of the process. The exit is made according to the completion sequence (Done Swq). The program calculates a time of 45s, and the machining time is 2h.
Figure 4 Finishing the side
4. Roughing the small intermediate groove
Using a D2 (R0.4) coated bullnose milling cutter with spiral machining (TYPE_SPIRAL), depth of cut (STEP_DEPTH) 0.25mm, stepover ( SIDE_STEP) 0.8 mm, contour allowance (PROF_STOCK_ALLOW) - 0.25 mm, roughing allowance (ROUGH_STOCK_ALLOW) - 0.25 mm, bottom allowance (BTTOM_STOCK_ALLOW) - 0.5 m m, machining method (TYPE_SPIRAL) 3 5 m m, machining mode (ROUGH_OPTION) ROUGH_ONLY, safety height (CLEAR_DIST) 5mm, spindle speed (SPINDLE_SPEED) 3500r/min, feed speed (CUT_FEED) 450mm/min.
Using the Screen Demonstration (Screen Play) function, the machining tool trajectory is shown in Figure 5.
Meanwhile, the machining is checked by simulation simulation (NC Check) and overcut check (GougeCheck). The milling cutter enters the interior of the intermediate slot and the profile of the slot is milled out to meet the requirements of the process. Exit according to the completion sequence (Done Swq). The time calculated by the program is 30s, and the machining time is 1h.
Figure 5 Roughing the small intermediate slot
5. Finishing III
Finishing is done by using a D1 (R0.5) ball-end milling cutter with surface milling (SurfaceMilling), with a step spacing (SIDE_STEP)of 0.2mm, and contouring allowance (PROF STOCK_ALLOW) -0.25mm, cutting angle (CUT_ANGLE) 45°, machining type (SCAN_TYPE) TYPE_3, safety height (CLEAR_DIST) 5mm, spindle speed (SPINDLE_SPEED) 3500r/min, feed speed (CUT_FEED) 400mm/min. /Using the Screen Play function, the machining tool trajectory is shown in Fig. 6. At the same time, the machining is checked by simulation (NC Check) and overcut check (Gouge Check). The milling cutter enters the interior of the intermediate slot, and the negative allowance (spark gap, i.e., rocking amount) of the machined shaped surface defined inside the slot is removed, in compliance with the process. Exit by the completion sequence (DoneS wq). The time calculated by the program is 60s, and the machining time is 0.5h.
Figure 6 Finishing small intermediate groove
Four, editing the machining work instructions
The CNC machining work instructions are shown in Figure 7.
Figure 7 Example of machining work instructions
V. Conclusion
In view of the future development trend of the mold industry, who can complete the mold in the shortest possible time, who will win the customer and win the market. As graphite electrode (compared with copper) has less electrode consumption, fast discharge processing speed, good machining performance, light weight, small coefficient of thermal expansion and other superiority, has been gradually recognized and accepted. With graphite electrode, we have the mold tomorrow! (Jiangsu Chunlan Machinery Manufacturing Co., Ltd., Zhang Xiaolu)