CNC compound high speed micro automatic cutting tool system
2018-10-16 12:04:19
In recent years, the development and application of CNC multi-axis controlled composite cutting, high-speed cutting, micro-precision cutting and ultra-precision cutting technology have attracted attention. At the same time, the tool system technology has also made significant progress. It is characterized by high rigidity in the multi-axis controlled compound cutting, high-speed cutting and high-precision cutting of CNC. Stability; in the structural design, the spindle, tool holder and tool are designed in an integrated design to minimize system components and provide excellent high-speed rotation characteristics.
The latest developments in tool system development
(1) CNC composite cutting tool system
The so-called CNC composite cutting refers to a variety of cutting tasks, such as milling cutters such as milling cutters and drills, and fixed tools such as turning tools. To this end, the tool system used must be multifunctional. When CNC mold cutting technology and corresponding tool system are used to process mold parts, in the past, multiple processes were used to complete the processing. Now, only one process can complete all the processing operations including deep holes, which greatly simplifies the process and improves the process. Processing quality. The new product of CNC compound cutting tool system includes two types of products, one is the tool system for rotating tools; the other is the tool system for non-rotating tools, the connection structure with the main shaft is the same as the tool system for rotating tools. .
The various tool systems and spindle connection structures currently used have not only the original design structure of each tool factory, but also standard structures such as BT and HSK, which brings trouble to the user to select the tool system. For the convenience of users, in the fall of 2004, experts and scholars from machine tool factories, tool factories, tool system manufacturers, users and related universities put forward proposals for standardization of tool systems, and proposed to adopt the HSK tool system that is undergoing international standardization (ISO). Structure, and held a seminar to exchange views on its standardization issues.
On the other hand, the use of hot-mounted tool systems has increased due to the increased overhang of the tool-extracting tool system chuck. The hot-mounted tool system is a tool system that uses the thermal expansion and contraction characteristics of metal materials to clamp the tool. It has the characteristics of simple structure, high speed and high rigidity, high diameter jump accuracy, and easy access to the workpiece.
From the development trend, it can be predicted that with the popularization and application of CNC composite cutting technology, new cutting tools and tool systems will be required. Through the joint research and development of tools, tool systems and machine tools, it will appear for CNC composite cutting. New tool system.
(2) High-speed milling tool system
In the vertical milling process, the spring collet type tool system was mainly used in the past, and the clamping methods mainly include the nut press-in type and the pull-in type. With the popularization of high-speed end-milling technology, the spindle speed of CNC machine tools such as machining centers is getting higher and higher, and a new tool system is needed. In order to meet the needs of high-speed milling, the structure, accuracy and high-speed performance of the collet-type tool system have been improved. However, from the comparison with the hot-mounted tool system, the spring collet tool system still needs further improvement and improvement in terms of high-speed rotation rigidity, diameter jump accuracy and performance close to the workpiece.
From the characteristics of several representative tool systems currently on the market, the hot-mounted tool system has obvious advantages in terms of high-speed rotational rigidity, run-out accuracy and performance in the cutting zone, so its application is rapidly increasing. In the fall of 2004, the tool system manufacturer conducted a survey of the tool systems used in the machining center, and the results showed that the application of the hot-mounted tool system was the most popular.
(3) Micro-tool high-speed precision cutting tool system
In recent years, milling with a micro end mill having a diameter of φ1 mm or less has attracted attention, and an ultra-high-speed precision machining center has also been born. For example, machining a square cavity with a side length of 100 μm and a depth of 40 μm with an end mill with a diameter of φ60 μm requires a tool with a track jump accuracy of a few micrometers or less. Therefore, the machining center, the tool system, and the machining integration system should have extremely high dynamics. Stiffness and balance performance.
The clamping method of directly clamping the end mill on the spindle of the machining center is an effective measure to ensure the accuracy of the tool clamping, and its application will continue to increase.
Reliability of hot-mounted tool systems
The hot-fit tool system heats the shank to expand it, inserts the tool, and then cools it to shrink the clamping tool. Due to the repeated cycles of the heating-cooling process, will the metal structure and hardness of the shank change and the performance of the tool system be degraded? Yamanashi Industrial Technology Center of Japan and YS Electronics Industry (heating equipment manufacturing plant for hot-mounted tool systems) jointly tested and analyzed the reliability of the hot-mounted tool system, and reached the following conclusions:
1 1700 heating-cooling cycle tests were performed on the hot-fit shank, and no dimensional accuracy was observed;
2 Observing the cross-sectional structure of each test piece, no structural changes due to the heating-cooling cycle were found; there were signs of wear on the axial surface due to the extraction of the tool, but no cracks;
3 The test results of the hardness of the tool holder section showed that the hardness was slightly reduced (about 100 HV) in the range of 20 μm or less from the outer surface, but no change in the hardness distribution due to the difference in the number of heating-cooling cycles was observed.
4 After the completion of the heating-cooling cycle test, the clamping force of the shank was measured by a press-in tester, and even if the number of test cycles was increased, no change in the clamping was observed.
Hot-mounted tool system and high-frequency induction heating
The hot-loading tool system heats the clamping tool to about 300 ° C to expand it, then inserts the tool shank for cooling, and clamps the tool through the cooling contraction of the heated shank, which requires corresponding heating equipment.
The existing hot-packing equipment has two categories: hot air type and induction heating type. The hot air type has the lowest price and the most use, but the disadvantages are low thermal efficiency and long heating time; the induction heating type has a short heating time, and the frequency is divided into two types: 50 kHz or less and 2 MHz or more. In the European region, induction heating devices of 50 kHz or less and 40 kHz or more are popular. The Japanese market also sells heating devices with frequencies below 50 kHz. At the same time, Japan is also developing high-frequency heating devices of 1 MHz or more.
Table 1 Comparison of heating methods for different heating methods - price - applicable range Hot air heating -20 ~ 800,000 yen - only for φ20 or more stainless steel, not for tool steel
25kHz induction heating 1H (15kW) - about 6 million yen - suitable for φ6 or more stainless steel and tool steel, not suitable for φ6 and below specifications high frequency induction heating 1H (10kW) - about 5 million yen - for stainless steel and tool steel High-frequency induction heating 1H (1kW) - about 2 million yen - for φ12 and below stainless steel and tool steel, not for φ12 or above
Compared with the hot air heating type, the non-magnetic holder hot charging with a 1 kW induction heating device can greatly shorten the heating time. With high frequency heating above 1MHz, not only is the power consumption and initial cost low, but it is also suitable for small diameter tools of non-magnetic metal materials such as stainless steel and titanium. The power supply part of the device can be miniaturized. In principle, a circuit with low conversion signal-to-noise ratio is adopted, which has high frequency conversion efficiency (about 98%), energy saving, miniaturization and low noise.
Automated tool change automation
The general tool change automation program is as follows:
(1) Manually load the tool on the tool system, and then confirm the accuracy of the path jump of the cutting edge of the tool on the tool presetter;
(2) Manually load the tool that is clamped on the tool system and has passed the test and confirmed the accuracy to be loaded into the tool magazine of the CNC machine such as the machining center;
(3) According to the NC program command input to the CNC machine tool, the tool system that automatically removes the loaded tool from the tool magazine is mounted on the machine tool spindle;
(4) After the cutting process is completed, the tool is automatically released from the spindle and returned to the tool magazine according to the NC program command;
(5) Manually remove the used tool from the magazine and put it back into the tool room, and remove the tool from the tool system.
With the rapid development of high-speed, precision, and automated cutting, the requirements for the tool's run-off accuracy and high-speed rigidity have reached several micrometers. To this end, the research has developed a hot-loading tool automatic loading and unloading (tool change) device that meets the requirements of precision and rigidity. This is a perfect system for automatic loading and unloading and measurement of tools and tool holders. The system consists of a unit consisting of a tool magazine, a tool holder library, a tool and tool holder mounting part library, and an induction heating unit for loading and unloading tools and tool holders, a transfer unit and a CNC control unit. The unit that automatically mounts the tool such as the end mill on the shank is the core part, and the insertion gap of the tool should be controlled within a few microns. The suction and extrusion technology is used to locally heat (high-frequency induction heating) at the tool insertion part of the shank, and the tool is sucked into the air by the air, and the tool is cooled and clamped. After the machining is completed, the tool is ejected by the NC adjustment lever. The NC adjustment lever has various functions such as tool presetting, ejection of the tool when unloading, Z-direction adjustment, and confirmation of the gripping state of the tool system.
The system is equipped with a non-contact automatic detection system that confirms the tool and tool holder assembly status. It is also possible to check the applicable tool specified by the NC program command in advance. With the automatic transfer function, the tool system consisting of the tool and the tool holder can be mounted on the tool magazine of a CNC machine such as a machining center, so that high-speed, high-precision machining with long-term stable automatic operation can be realized.
The latest developments in tool system development
(1) CNC composite cutting tool system
The so-called CNC composite cutting refers to a variety of cutting tasks, such as milling cutters such as milling cutters and drills, and fixed tools such as turning tools. To this end, the tool system used must be multifunctional. When CNC mold cutting technology and corresponding tool system are used to process mold parts, in the past, multiple processes were used to complete the processing. Now, only one process can complete all the processing operations including deep holes, which greatly simplifies the process and improves the process. Processing quality. The new product of CNC compound cutting tool system includes two types of products, one is the tool system for rotating tools; the other is the tool system for non-rotating tools, the connection structure with the main shaft is the same as the tool system for rotating tools. .
The various tool systems and spindle connection structures currently used have not only the original design structure of each tool factory, but also standard structures such as BT and HSK, which brings trouble to the user to select the tool system. For the convenience of users, in the fall of 2004, experts and scholars from machine tool factories, tool factories, tool system manufacturers, users and related universities put forward proposals for standardization of tool systems, and proposed to adopt the HSK tool system that is undergoing international standardization (ISO). Structure, and held a seminar to exchange views on its standardization issues.
On the other hand, the use of hot-mounted tool systems has increased due to the increased overhang of the tool-extracting tool system chuck. The hot-mounted tool system is a tool system that uses the thermal expansion and contraction characteristics of metal materials to clamp the tool. It has the characteristics of simple structure, high speed and high rigidity, high diameter jump accuracy, and easy access to the workpiece.
From the development trend, it can be predicted that with the popularization and application of CNC composite cutting technology, new cutting tools and tool systems will be required. Through the joint research and development of tools, tool systems and machine tools, it will appear for CNC composite cutting. New tool system.
(2) High-speed milling tool system
In the vertical milling process, the spring collet type tool system was mainly used in the past, and the clamping methods mainly include the nut press-in type and the pull-in type. With the popularization of high-speed end-milling technology, the spindle speed of CNC machine tools such as machining centers is getting higher and higher, and a new tool system is needed. In order to meet the needs of high-speed milling, the structure, accuracy and high-speed performance of the collet-type tool system have been improved. However, from the comparison with the hot-mounted tool system, the spring collet tool system still needs further improvement and improvement in terms of high-speed rotation rigidity, diameter jump accuracy and performance close to the workpiece.
From the characteristics of several representative tool systems currently on the market, the hot-mounted tool system has obvious advantages in terms of high-speed rotational rigidity, run-out accuracy and performance in the cutting zone, so its application is rapidly increasing. In the fall of 2004, the tool system manufacturer conducted a survey of the tool systems used in the machining center, and the results showed that the application of the hot-mounted tool system was the most popular.
(3) Micro-tool high-speed precision cutting tool system
In recent years, milling with a micro end mill having a diameter of φ1 mm or less has attracted attention, and an ultra-high-speed precision machining center has also been born. For example, machining a square cavity with a side length of 100 μm and a depth of 40 μm with an end mill with a diameter of φ60 μm requires a tool with a track jump accuracy of a few micrometers or less. Therefore, the machining center, the tool system, and the machining integration system should have extremely high dynamics. Stiffness and balance performance.
The clamping method of directly clamping the end mill on the spindle of the machining center is an effective measure to ensure the accuracy of the tool clamping, and its application will continue to increase.
Reliability of hot-mounted tool systems
The hot-fit tool system heats the shank to expand it, inserts the tool, and then cools it to shrink the clamping tool. Due to the repeated cycles of the heating-cooling process, will the metal structure and hardness of the shank change and the performance of the tool system be degraded? Yamanashi Industrial Technology Center of Japan and YS Electronics Industry (heating equipment manufacturing plant for hot-mounted tool systems) jointly tested and analyzed the reliability of the hot-mounted tool system, and reached the following conclusions:
1 1700 heating-cooling cycle tests were performed on the hot-fit shank, and no dimensional accuracy was observed;
2 Observing the cross-sectional structure of each test piece, no structural changes due to the heating-cooling cycle were found; there were signs of wear on the axial surface due to the extraction of the tool, but no cracks;
3 The test results of the hardness of the tool holder section showed that the hardness was slightly reduced (about 100 HV) in the range of 20 μm or less from the outer surface, but no change in the hardness distribution due to the difference in the number of heating-cooling cycles was observed.
4 After the completion of the heating-cooling cycle test, the clamping force of the shank was measured by a press-in tester, and even if the number of test cycles was increased, no change in the clamping was observed.
Hot-mounted tool system and high-frequency induction heating
The hot-loading tool system heats the clamping tool to about 300 ° C to expand it, then inserts the tool shank for cooling, and clamps the tool through the cooling contraction of the heated shank, which requires corresponding heating equipment.
The existing hot-packing equipment has two categories: hot air type and induction heating type. The hot air type has the lowest price and the most use, but the disadvantages are low thermal efficiency and long heating time; the induction heating type has a short heating time, and the frequency is divided into two types: 50 kHz or less and 2 MHz or more. In the European region, induction heating devices of 50 kHz or less and 40 kHz or more are popular. The Japanese market also sells heating devices with frequencies below 50 kHz. At the same time, Japan is also developing high-frequency heating devices of 1 MHz or more.
Table 1 Comparison of heating methods for different heating methods - price - applicable range Hot air heating -20 ~ 800,000 yen - only for φ20 or more stainless steel, not for tool steel
25kHz induction heating 1H (15kW) - about 6 million yen - suitable for φ6 or more stainless steel and tool steel, not suitable for φ6 and below specifications high frequency induction heating 1H (10kW) - about 5 million yen - for stainless steel and tool steel High-frequency induction heating 1H (1kW) - about 2 million yen - for φ12 and below stainless steel and tool steel, not for φ12 or above
Compared with the hot air heating type, the non-magnetic holder hot charging with a 1 kW induction heating device can greatly shorten the heating time. With high frequency heating above 1MHz, not only is the power consumption and initial cost low, but it is also suitable for small diameter tools of non-magnetic metal materials such as stainless steel and titanium. The power supply part of the device can be miniaturized. In principle, a circuit with low conversion signal-to-noise ratio is adopted, which has high frequency conversion efficiency (about 98%), energy saving, miniaturization and low noise.
Automated tool change automation
The general tool change automation program is as follows:
(1) Manually load the tool on the tool system, and then confirm the accuracy of the path jump of the cutting edge of the tool on the tool presetter;
(2) Manually load the tool that is clamped on the tool system and has passed the test and confirmed the accuracy to be loaded into the tool magazine of the CNC machine such as the machining center;
(3) According to the NC program command input to the CNC machine tool, the tool system that automatically removes the loaded tool from the tool magazine is mounted on the machine tool spindle;
(4) After the cutting process is completed, the tool is automatically released from the spindle and returned to the tool magazine according to the NC program command;
(5) Manually remove the used tool from the magazine and put it back into the tool room, and remove the tool from the tool system.
With the rapid development of high-speed, precision, and automated cutting, the requirements for the tool's run-off accuracy and high-speed rigidity have reached several micrometers. To this end, the research has developed a hot-loading tool automatic loading and unloading (tool change) device that meets the requirements of precision and rigidity. This is a perfect system for automatic loading and unloading and measurement of tools and tool holders. The system consists of a unit consisting of a tool magazine, a tool holder library, a tool and tool holder mounting part library, and an induction heating unit for loading and unloading tools and tool holders, a transfer unit and a CNC control unit. The unit that automatically mounts the tool such as the end mill on the shank is the core part, and the insertion gap of the tool should be controlled within a few microns. The suction and extrusion technology is used to locally heat (high-frequency induction heating) at the tool insertion part of the shank, and the tool is sucked into the air by the air, and the tool is cooled and clamped. After the machining is completed, the tool is ejected by the NC adjustment lever. The NC adjustment lever has various functions such as tool presetting, ejection of the tool when unloading, Z-direction adjustment, and confirmation of the gripping state of the tool system.
The system is equipped with a non-contact automatic detection system that confirms the tool and tool holder assembly status. It is also possible to check the applicable tool specified by the NC program command in advance. With the automatic transfer function, the tool system consisting of the tool and the tool holder can be mounted on the tool magazine of a CNC machine such as a machining center, so that high-speed, high-precision machining with long-term stable automatic operation can be realized.
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