Development of ultrasonic machining technology with a five-fold increase in cutting efficiency – Hermann Sauer and Deckel Maho's breakthrough in the processing of hard and brittle materials.
The introduction of new materials promotes changes in processing methods All technical departments are conducting trials of new materials and have entered the practical stage. High-performance materials such as industrial ceramics, optical glass, and hard alloys have superior properties. However, the precise forming of these difficult-to-cut materials is a very difficult problem for manufacturing technology. Thanks to the combination of ultrasonic technology and advanced machine technology, Germany's Her-mann Sauer and Deckel Maho offer the best solutions for this.
When using difficult-to-machine glass, ceramic, and hard alloy materials, the efficiency of processing and finishing is a problem. Because these materials are mostly non-conductors, not the object of electrical processing technology. Similarly, laser processing technology, because the basis of the processing is the use of heat, it is not a problem to exclude thermal damage and micro cracking of the material, which is also a big problem.
In the conventional cutting method, it takes a long time to work hard to meet the processing requirements. In this case, not only the tool wear is large, but also the surface quality is not ideal. In response to the above problems, the department developed a new ultrasonic machining technology at Hermann Sauer in Stipshausen, central Germany, which is five times more efficient in machining hard brittle materials than the original method.
Principles of new technology processing methods The basis of the new technology is the ultrasonic machining process based on the combination of the ultrasonically controlled machining spindle and the latest processing machine. It is a high-frequency vibration motion added to the original machining process (é•—, grinding, milling).
The piezoelectric transducer of the ultrasonic spindle converts the electrical high-frequency signal of the ultrasonic generator into mechanical motion (longitudinal vibration) according to a fixed frequency of 20 kHz which is adapted to various tool components. This vibration is sent from the converter to the amplifier. This amplifier can accommodate a wide variety of needs and can control the increase in travel. The patented conical tool holder finally transmits the vibration to the tool, which is the diamond tool. In deep machining, approximately 20,000 pulse movements per second are produced - longitudinal motion during contour machining.
In the original machining without ultrasonic, the cutting process generates a large amount of cutting heat due to friction, and fine cracks are generated on the workpiece. In terms of quality, these workpieces must be ground again, and the tool wears quickly. . However, when ultrasonic machining is used for impact machining, about 60% to 70% of the efficiency is activated. Therefore, the rotary tool movement is not wasted, and most of it is used for the removal of the workpiece particles. Because of the low thermal impact, the tool has a short contact time, a small cutting force, and no cracking or edge damage.
Since the surface quality is improved by using an abrasive (maximum Ra < 0.2 μm), the machining can be omitted, and the load and friction of the tool are also reduced. There is also the advantage that water can be used as a cleaning agent due to the removal of tiny chips and fine debris.
After the special diamond tool ultrasonic assembly and tool holder are required, the design of the diamond tool is the key to the success of the ultrasonic machining process. Ultrasonic machining, on the one hand, guarantees cutting performance and on the other hand enables the tool to achieve a long life. Special requirements are placed not only on the diamond abrasive but also on its combination.
The natural diamond abrasive Prema DiaPDA665 is the most suitable abrasive in diamond tools. This sharp abrasive grain has excellent micro-breaking properties when subjected to an impact load. Diamond tools have a self-sharpening effect during processing. Hermann Sauer uses diamond abrasive grains from 6μm to 90μm in the manufacture of tools for boring, grinding and milling. In order to keep the tool wear within the minimum limits, the company developed a special connection method for transmitting mechanical vibration without damaging the tool. This is called the connection of glass and ceramics, which is brazed under high vacuum; it is the combination of diamond abrasive particles and the basic material of the tool. This combination is not only mechanical but also chemical. The chemical combination prevents the early abrasive particles from peeling off, has a high bonding force, and has the advantage of maximizing heat dissipation at the blade portion.
Ultrasonic machining of the control system with teaching function requires adaptive control. To this end, Sauer and Fagor have jointly developed numerical control devices for ultrasonic machining. Its essence is adaptive control (ADR) and volume control (ACC), with two teaching methods for teaching functions. In order to meet the processing requirements, it can be used alone or in combination. Regardless of adaptive control and volume control, it must be adapted to the amount of operation and control of the usual process management and processing. Therefore, it can recognize the contour error in time. In addition, the wear of the tool is almost negligible. Adapting control, tools become the basis of process control, this method can achieve the most appropriate feed rate. The ACC receives and manages the volume signal, for which the process can be optimized in real-time processing. ACC is for workpieces, and this method is mainly used to obtain the best surface quality. The combination of ADR and ACC provides the best flexibility for machining operations. ADR can be used for maximum machining speed during machining, and the control system automatically switches to Volumetric Process Control (ACC) when the best surface quality is required. This system is currently equipped with DMS 35 and DMS 50 ultrasonic machines as standard. The stroke of the DMS 35 machine is 240mm (Y-axis), 340mm (Z-axis) and 350mm (X-axis); while for the DMS 50, the X-axis travel is 500mm. The motor has a power of 1.8/1.3 kW (40% ED/100% ED) and a spindle speed of 3000 r/min (option 60 000 r/min). The maximum feed rate is up to 5000mm/min. Since the fixed frequency is 20 kHz, it is ensured that the frequency band is in the range of 17.5 kHz to 21.5 kHz.
Finally, due to the superior characteristics of the ultrasonic machining method, the cutting amount is increased, the feed performance is improved, and the productivity can be increased up to four times as compared with the original processing method.
Application examples are expanding, for example, in medical technology (such as endoscopy), when the optical glass must be used, the machine is used. The diamond reaming drill of DMS 35 ultrasonic processing machine can produce glass rods with a diameter of 2mm-202mm and a maximum length of 160mm. During processing, depending on the type of material, the machining feed rate can be 25mm/min to 50mm/min, and the spindle rotation speed is 800 to 3000r/min. Using these processing parameters, the processing time is 1.5 min - 2 min. It takes 2 to 3 times longer to use the original processing method. The unique advantage of this machine is that water can be used as a cooling and cleaning agent. When oil is used before, there is a risk of fire, and a monitor must be placed during processing. When using the DMS 35 ultrasonic machine, it can be cross-worked for several months to achieve continuous unmanned operation.
Yet another example is the use of a diamond reaming drill to machine a 12 mm diameter ceramic blank made of zirconia. User requirements significantly reduce processing time. In the previous processing method, the blank was rotated at 8000 r/min and the feed rate was 12 mm/min. In order to achieve surface quality RaO. For the 4μm requirement, a grinding is also required. When using ultrasonic machining, the spindle speed is 3000r/min, the feed rate can be increased by 4 times, about 48mm/min, and the surface quality can be achieved without further grinding.
Another example is the use of ultrasonic machining to economically process parts made of difficult-to-machine materials such as glass, ceramics, and cemented carbide. The harder the harder the more processed, the better the effect.
In addition to ceramics, glass, hard alloys, various gemstones (corundum, agate, ruby, etc.), reinforced fiber plastics, silicon, graphite and other materials can use this ultrasonic processing method.
The introduction of new materials promotes changes in processing methods All technical departments are conducting trials of new materials and have entered the practical stage. High-performance materials such as industrial ceramics, optical glass, and hard alloys have superior properties. However, the precise forming of these difficult-to-cut materials is a very difficult problem for manufacturing technology. Thanks to the combination of ultrasonic technology and advanced machine technology, Germany's Her-mann Sauer and Deckel Maho offer the best solutions for this.
When using difficult-to-machine glass, ceramic, and hard alloy materials, the efficiency of processing and finishing is a problem. Because these materials are mostly non-conductors, not the object of electrical processing technology. Similarly, laser processing technology, because the basis of the processing is the use of heat, it is not a problem to exclude thermal damage and micro cracking of the material, which is also a big problem.
In the conventional cutting method, it takes a long time to work hard to meet the processing requirements. In this case, not only the tool wear is large, but also the surface quality is not ideal. In response to the above problems, the department developed a new ultrasonic machining technology at Hermann Sauer in Stipshausen, central Germany, which is five times more efficient in machining hard brittle materials than the original method.
Principles of new technology processing methods The basis of the new technology is the ultrasonic machining process based on the combination of the ultrasonically controlled machining spindle and the latest processing machine. It is a high-frequency vibration motion added to the original machining process (é•—, grinding, milling).
The piezoelectric transducer of the ultrasonic spindle converts the electrical high-frequency signal of the ultrasonic generator into mechanical motion (longitudinal vibration) according to a fixed frequency of 20 kHz which is adapted to various tool components. This vibration is sent from the converter to the amplifier. This amplifier can accommodate a wide variety of needs and can control the increase in travel. The patented conical tool holder finally transmits the vibration to the tool, which is the diamond tool. In deep machining, approximately 20,000 pulse movements per second are produced - longitudinal motion during contour machining.
In the original machining without ultrasonic, the cutting process generates a large amount of cutting heat due to friction, and fine cracks are generated on the workpiece. In terms of quality, these workpieces must be ground again, and the tool wears quickly. . However, when ultrasonic machining is used for impact machining, about 60% to 70% of the efficiency is activated. Therefore, the rotary tool movement is not wasted, and most of it is used for the removal of the workpiece particles. Because of the low thermal impact, the tool has a short contact time, a small cutting force, and no cracking or edge damage.
Since the surface quality is improved by using an abrasive (maximum Ra < 0.2 μm), the machining can be omitted, and the load and friction of the tool are also reduced. There is also the advantage that water can be used as a cleaning agent due to the removal of tiny chips and fine debris.
After the special diamond tool ultrasonic assembly and tool holder are required, the design of the diamond tool is the key to the success of the ultrasonic machining process. Ultrasonic machining, on the one hand, guarantees cutting performance and on the other hand enables the tool to achieve a long life. Special requirements are placed not only on the diamond abrasive but also on its combination.
The natural diamond abrasive Prema DiaPDA665 is the most suitable abrasive in diamond tools. This sharp abrasive grain has excellent micro-breaking properties when subjected to an impact load. Diamond tools have a self-sharpening effect during processing. Hermann Sauer uses diamond abrasive grains from 6μm to 90μm in the manufacture of tools for boring, grinding and milling. In order to keep the tool wear within the minimum limits, the company developed a special connection method for transmitting mechanical vibration without damaging the tool. This is called the connection of glass and ceramics, which is brazed under high vacuum; it is the combination of diamond abrasive particles and the basic material of the tool. This combination is not only mechanical but also chemical. The chemical combination prevents the early abrasive particles from peeling off, has a high bonding force, and has the advantage of maximizing heat dissipation at the blade portion.
Ultrasonic machining of the control system with teaching function requires adaptive control. To this end, Sauer and Fagor have jointly developed numerical control devices for ultrasonic machining. Its essence is adaptive control (ADR) and volume control (ACC), with two teaching methods for teaching functions. In order to meet the processing requirements, it can be used alone or in combination. Regardless of adaptive control and volume control, it must be adapted to the amount of operation and control of the usual process management and processing. Therefore, it can recognize the contour error in time. In addition, the wear of the tool is almost negligible. Adapting control, tools become the basis of process control, this method can achieve the most appropriate feed rate. The ACC receives and manages the volume signal, for which the process can be optimized in real-time processing. ACC is for workpieces, and this method is mainly used to obtain the best surface quality. The combination of ADR and ACC provides the best flexibility for machining operations. ADR can be used for maximum machining speed during machining, and the control system automatically switches to Volumetric Process Control (ACC) when the best surface quality is required. This system is currently equipped with DMS 35 and DMS 50 ultrasonic machines as standard. The stroke of the DMS 35 machine is 240mm (Y-axis), 340mm (Z-axis) and 350mm (X-axis); while for the DMS 50, the X-axis travel is 500mm. The motor has a power of 1.8/1.3 kW (40% ED/100% ED) and a spindle speed of 3000 r/min (option 60 000 r/min). The maximum feed rate is up to 5000mm/min. Since the fixed frequency is 20 kHz, it is ensured that the frequency band is in the range of 17.5 kHz to 21.5 kHz.
Finally, due to the superior characteristics of the ultrasonic machining method, the cutting amount is increased, the feed performance is improved, and the productivity can be increased up to four times as compared with the original processing method.
Application examples are expanding, for example, in medical technology (such as endoscopy), when the optical glass must be used, the machine is used. The diamond reaming drill of DMS 35 ultrasonic processing machine can produce glass rods with a diameter of 2mm-202mm and a maximum length of 160mm. During processing, depending on the type of material, the machining feed rate can be 25mm/min to 50mm/min, and the spindle rotation speed is 800 to 3000r/min. Using these processing parameters, the processing time is 1.5 min - 2 min. It takes 2 to 3 times longer to use the original processing method. The unique advantage of this machine is that water can be used as a cooling and cleaning agent. When oil is used before, there is a risk of fire, and a monitor must be placed during processing. When using the DMS 35 ultrasonic machine, it can be cross-worked for several months to achieve continuous unmanned operation.
Yet another example is the use of a diamond reaming drill to machine a 12 mm diameter ceramic blank made of zirconia. User requirements significantly reduce processing time. In the previous processing method, the blank was rotated at 8000 r/min and the feed rate was 12 mm/min. In order to achieve surface quality RaO. For the 4μm requirement, a grinding is also required. When using ultrasonic machining, the spindle speed is 3000r/min, the feed rate can be increased by 4 times, about 48mm/min, and the surface quality can be achieved without further grinding.
Another example is the use of ultrasonic machining to economically process parts made of difficult-to-machine materials such as glass, ceramics, and cemented carbide. The harder the harder the more processed, the better the effect.
In addition to ceramics, glass, hard alloys, various gemstones (corundum, agate, ruby, etc.), reinforced fiber plastics, silicon, graphite and other materials can use this ultrasonic processing method.
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