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CNC compaction
The quest for high performance parts in the PM industry is leading manufacturers to demand ever more sophisticated process control functions for production equipment. Computerized numerical control &NC) potential/y offers the manufacturer a means of maintaining dimensional control, achieving full densify and preventing crack propagation in the production of PM components.
Theory Manufacturers are increasingly turning to more advanced equipment for producing intricate shapes and maintaining high product quality. Computerized numerical control (CNC) is being used in the powder metallurgy (PM) industry because it offers an effective means of solving technical problems. CNC allows the manufacturer full control of all stages of the compaction process: powder fill, compression and ejection. These steps may all be managed quantitatively and accurately to optimize processing and produce high performance parts.
Equipment Dorst GmbH of Kochel am See, Germany, manufactures a range of hydraulic automatic CNC presses. The ‘TPA-H’ and ‘TPA-HMP’ presses also feature electronic visual display terminal (VDT) control, standard adaptor systems and multiplaten adaptors. Dorst says its presses are designed to meet the highest demands for precision in the production of intricate components. The presses are capable of performing an optimum sequence of movements. When connected to a standard adaptor, a range of movements can be performed: l 3 closed loop controlled axes Axis 1 (top ram); Axis 2 (lower ram/die); Axis 3 (filler movement); l 2 open loop controlled axes Axis 4 (secondary lower ram) ; Axis 5 (secondary top ram). If multiplaten adaptors are used, up to 10 closed loop controlled axes will be made available. Dorst says it designed the equipment to be user friendly. The main axes of the system, the top ram and die, are programmed when the system is first set-up to be run. This sequence of movements 46
MPR October 1996
may then be optimized in ‘free mode’ by changing and adding further steps. For complicated programs and sequences, all available axes may be completely defined in free mode. A useful feature of the Dorst CNC presses is electronic VDT control, providing speed and a computing capability, to allow maximum precision in processing extensive closed loop control programs. The unit allows high resolution of the position measuring systems at the main axes, and by eliminating reference marks, also reduces limitations of tool design. It also provides an electronic compensation for elongation which ensures precision in component height, .even in cases of major filling height adjustments, or variations in powder fill. Osterwalder AG of Lyss, Switzerland, also designs and manufactures hydraulic powder presses. Its ‘CA-NC’ and ‘UPP’ presses are CNC, and the company says their modular designs offer maximum flexibility and good accessibility. Osterwalder says its presses are built to meet the most demanding process requirements, from simple to complex multi-level compacts. The presses offer a freely programmable control for optimal press cycles. In the CA-NC, a multiprocessor technique allows short controlling cycles for complex and fast processes. In the UPP presses, up to 16 closed loop controlled axes may be made available. The presses also provide a high number of strokes, and can offer up to three filling devices. A selection of withdrawal and ejection modes are possible, with a high withdrawal force, and a large space for tooling. Statistical process control makes it possible to assess the pressing cycle, allowing automatic adjustment of the cycle parameters.
Applications Osterwalder CNC presses may be used in the production of parts in a range of PM applications. Hard materials such as sintered carbides, diamond powder and cermet metal ceramics are processed to produce a range of components such as cutting tools and hard wearing dies. Other materials include light alloys, metals, graphite, ceramics, uranium oxide and composites. Keystone Powdered Metal Co of St Marys, Pennsylvania, USA, uses a Dorst CNC press in the production of parking gears and drive sprockets for automotive transmission. The press offers what the company says is unparalleled accuracy. It allows the processing of multi-level PM configurations wiyiththinner cross-sections and larger diameters that were previously thought impossible. Keystone says it can also now compact to net shape parts that were originally machined from wrought materials. The near net shape capability of the CNC press eliminates the need for expensive post sintering machining operations, resulting in considerable cost reductions. The company says that a significant feature of the press is that, unlike in conventional presses, metal powder can be transferred without necessarily compressing it. This unique mix transfer capability is possible because the press can drive the powder upward as well as dowmvard with its six plungers, and up to nine axes for filling and compaction. A major barrier preventing the use of CNC presses in industry is the cost of the equipment, and the expense of installing t,he system. In an overview of the present status of the industry in Japan (‘CNC presses open new possibilities for powder compacting ~ overview of current development in Japan’, Proc. 1995 European Co’olzferenceon Advanced PM Materials, pp. 29-36) H. Tsuru and T. Nakagawa suggest that a minimum of functions specified for hardware, accuracy and control could reduce these cost,s. They say research efforts to determine optimum powder characteristics for CNC compaction will also be important.
Theory Manufacturers are increasingly turning to more advanced equipment for producing intricate shapes and maintaining high product quality. Computerized numerical control (CNC) is being used in the powder metallurgy (PM) industry because it offers an effective means of solving technical problems. CNC allows the manufacturer full control of all stages of the compaction process: powder fill, compression and ejection. These steps may all be managed quantitatively and accurately to optimize processing and produce high performance parts.
Equipment Dorst GmbH of Kochel am See, Germany, manufactures a range of hydraulic automatic CNC presses. The ‘TPA-H’ and ‘TPA-HMP’ presses also feature electronic visual display terminal (VDT) control, standard adaptor systems and multiplaten adaptors. Dorst says its presses are designed to meet the highest demands for precision in the production of intricate components. The presses are capable of performing an optimum sequence of movements. When connected to a standard adaptor, a range of movements can be performed: l 3 closed loop controlled axes Axis 1 (top ram); Axis 2 (lower ram/die); Axis 3 (filler movement); l 2 open loop controlled axes Axis 4 (secondary lower ram) ; Axis 5 (secondary top ram). If multiplaten adaptors are used, up to 10 closed loop controlled axes will be made available. Dorst says it designed the equipment to be user friendly. The main axes of the system, the top ram and die, are programmed when the system is first set-up to be run. This sequence of movements 46
MPR October 1996
may then be optimized in ‘free mode’ by changing and adding further steps. For complicated programs and sequences, all available axes may be completely defined in free mode. A useful feature of the Dorst CNC presses is electronic VDT control, providing speed and a computing capability, to allow maximum precision in processing extensive closed loop control programs. The unit allows high resolution of the position measuring systems at the main axes, and by eliminating reference marks, also reduces limitations of tool design. It also provides an electronic compensation for elongation which ensures precision in component height, .even in cases of major filling height adjustments, or variations in powder fill. Osterwalder AG of Lyss, Switzerland, also designs and manufactures hydraulic powder presses. Its ‘CA-NC’ and ‘UPP’ presses are CNC, and the company says their modular designs offer maximum flexibility and good accessibility. Osterwalder says its presses are built to meet the most demanding process requirements, from simple to complex multi-level compacts. The presses offer a freely programmable control for optimal press cycles. In the CA-NC, a multiprocessor technique allows short controlling cycles for complex and fast processes. In the UPP presses, up to 16 closed loop controlled axes may be made available. The presses also provide a high number of strokes, and can offer up to three filling devices. A selection of withdrawal and ejection modes are possible, with a high withdrawal force, and a large space for tooling. Statistical process control makes it possible to assess the pressing cycle, allowing automatic adjustment of the cycle parameters.
Applications Osterwalder CNC presses may be used in the production of parts in a range of PM applications. Hard materials such as sintered carbides, diamond powder and cermet metal ceramics are processed to produce a range of components such as cutting tools and hard wearing dies. Other materials include light alloys, metals, graphite, ceramics, uranium oxide and composites. Keystone Powdered Metal Co of St Marys, Pennsylvania, USA, uses a Dorst CNC press in the production of parking gears and drive sprockets for automotive transmission. The press offers what the company says is unparalleled accuracy. It allows the processing of multi-level PM configurations wiyiththinner cross-sections and larger diameters that were previously thought impossible. Keystone says it can also now compact to net shape parts that were originally machined from wrought materials. The near net shape capability of the CNC press eliminates the need for expensive post sintering machining operations, resulting in considerable cost reductions. The company says that a significant feature of the press is that, unlike in conventional presses, metal powder can be transferred without necessarily compressing it. This unique mix transfer capability is possible because the press can drive the powder upward as well as dowmvard with its six plungers, and up to nine axes for filling and compaction. A major barrier preventing the use of CNC presses in industry is the cost of the equipment, and the expense of installing t,he system. In an overview of the present status of the industry in Japan (‘CNC presses open new possibilities for powder compacting ~ overview of current development in Japan’, Proc. 1995 European Co’olzferenceon Advanced PM Materials, pp. 29-36) H. Tsuru and T. Nakagawa suggest that a minimum of functions specified for hardware, accuracy and control could reduce these cost,s. They say research efforts to determine optimum powder characteristics for CNC compaction will also be important.