Survey of the development of petro-forge forming machines

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Abstract Of the many HERF hammers developed in the 50's and 60's three types have survived: Dynapak, CEFF and Petro-Forge. Dynapak and CEFF machines are pneumatically actuated devices. They continue to be used in industry, having found a segment of the market in which they compete successfully with conventional forming machines. The operational characteristics of these devices are discussed and a critical appraisal of their design features is given. Petro-Forge is a combustion actuated hammer. A survey of the development of these machines is offered within the context of the practical experience relating to Dynapak and CEFF. After discussing their operational principle, the various types and models constructed are surveyed, in particular the Petro-Forge Mk.IF and Mk.IIF, the “Slow-Speed Petro-Forge”, demonstrating that combustion actuation can be used also for relatively low impact speeds, and the “Counterblow Hammer”, the largest device built. Combustion actuation provides a 6 to 7 fold intensification of the primary power source. For the same blow energy output, a combustion actuated hammer requires a basic powerpack which is less than 1 6 th of that of any other, conventional or HERF, forming device. The smaller powerpack leads to substantially lower capital and maintenance costs and somewhat lower running costs. The automation of Petro-Forge, for hot and cold forming in single and multi-stations, fed by robots or special purpose feeding devices, is described. The designs of the automatic, adaptively controlled, Petro-Crop cropping machines are discussed. Utilizing a diameter measuring device and weighing/sorting system in conjunction with a micro-computer, these are capable of producing high quality billets with close weight tolerances from black bar. The control system of the Series F Petro-Forge and Petro-Crop machines is contrasted with that of the latest, Series G, models which are micro-computer controlled. These are capable of adapting themselves to changing operational conditions and they have built-in fault diagnostic capabilities to facilitate maintenance. Individual hammers can be controlled by a central processor and this allows a further deskilling of forming operations. Micro-computer controlled Petro-Forge/Petro-Crop machines represent a major step towards the computer integrated forming shop. The efficiency of forming machines is a product of the blow efficiency and the efficiency of energy transfer, The former is generally high, provided the machine is attached to a large foundation mass, or it is of the counterblow type or, in the case of HERF hammers, it is supported by a very low frequency suspension. The efficiency of energy transfer is related to the hardness of the blow. It can drop to low values and it is dependent on load arising when dies are allowed to clash. The effect of slight excess energy on the forming load is discussed and a method for its prediction is offered. A comparison of conventional machines and Petro-Forge hammers is offered by using the concept of the forming capacity; it is shown that the forming capacity of a Petro-Forge Mk.II machine corresponds to that of a 4–5 MN (400–500 tonf) screw press or a 4.5 MN (450 tonf) crank press. The survey is concluded by a discussion of the machine advantages/limitations in HERF machines in general and Petro-Forge in particular. High speed machines are small and compact devices; for the same forming capacity, high speed hammers are 1 9 th or less in bulk and weight in relation to conventional forming machines, irrespective of their method of actuation. In view of their small, compact size they have a significantly lower capital cost than conventional equipment. High speed machines usually do not require special expensive foundations and therefore their installation cost is also very much lower. Petro-Forge provides the additional benefits of a very high cycling rate, accurate control of the blow energy and a very short dwell time leading to improved die life in hot forming operation.