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EXCHANGE OF EXPERIENCE AND INFORMATION A HIGH-SPEED PNEUMATIC PRESS FOR THE OF METAL POWDERS AND HOT FORGING OF BLANKS S. P. Biryukov, V. A. Dymchenko, and V. A. Kostevskii PRESSING POROUS UDC 621.762.06 : 621.979 The hot forging of powder metallurgy materials is usually performed in ordinary mechanical presses, which allow very little control over the rate of tool travel and the work done during fcrging. This is a serious drawback both in research and development work and in standard production of parts. At the Kramatorsk Scientific-Research, Design, and Technological Institute of Machine Construction a new, impulse-action pneumatic press has been developed, and is already in operation, which is free from this drawback (Fig. 1). An important feature of the press is that the valve separating its receiver from the space above the ram operates very rapidly and has negligible aerodynamic resistance, which enables the compressed air to exert a shock action upon the ram. This has resulted in a better design of press, with smaller losses of compressed air energy. The speed of the ram and the work done during pressing can readily be regulated by varying, in the range from 10 to 120 kgf/cm 2, the pressure in the receiver. The impulse press (Fig. 2) is supported on a four-column unit formed by an upper 1 and a lower 2 cross- bar connected by columns 3. In the upper cross-bar is rigidly mounted the head section of the press, consist- ing of a receiver 4 and a working cylinder 11. Inthe upper part of the receiver is fitted a valve 6, which, in the starting position, is pressed against its seat 7 by a spring 8. The valve 6 is provided with a reverse valve 10 and a rubber shock absorber 9. The body of the working cylinder 11 and the receiver are made of a single steel forging 10. Inside the working cylinder, whose diameter is equal to the diameter of the outlet opening of the seat, is located the ram, the rod of which carries the components of the upper part of the die set 19. The lower part of the working cylinder is formed by a shell 13 fitted with a bushing 14. In its extreme upper position the ram is held by three ball catches 17 mounted in a shell 16. A controllable throttle 15 mounted in the upper part of the body of the working cylinder enables any air leaking in to escape and prevents spontaneous movement of the ram. The lower cross-bar of the press carries the stationary components of the die set 24 and a compressed air cylinder 20, whose purpose is to extract the core rod used in the pressing of parts such as bushings. To enable core rod extraction to be performed automatically by spent air, the rod cavity of the cylinder 20 is connected to the piston cavity of the working cylinder by a tube 25. The press operates as follows. Compressed air from the mains enters the cavity A through an opening in a cover 5, presses the valve 6 against its seat 7, and then flows through a passage and the reverse valve 10 into the receiver 4, filling the cavity B. To bring the press into operation, it is necessary to release air from the cavity A. When this is done, the air in the receiver rapidly lifts the valve 6, gaining access to the piston of the ram. As the diameter of the outlet opening of the valve seat is equal to the diameter of the working cylinder, the air rushes with minimum aerodynamic losses at high velocity toward the ram piston and, after striking it, propels the ram together with the die set attached to it. After the ram piston has reached its bottom position, the entry into the tube 25 opens. Spent air flows through this tube into the cylinder 20, where it moves the piston 21 with the core rod attached to it downward, and then escapes into the atmosphere through openings 26. Kramatorsk Scientific-Research, Design, and Technological Institute of Machine Construction. Trans- lated from Poroshkovaya Metallurgiya, No. 8(176), pp. 95-98, August, 1977. Original article submitted No- vember 27, 1976. This material is protected by copyright registered in the name of Plenum Publishing Corporation, 227 West 7th Street, New York, N.Y. 10011. No part $ of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, I microfilming, recording or otherwise, without written permission of the publisher. A copy of this article is available from the publisher for $ Z 50. 646 Fig. 1 Fig. 2 Fig. 1. Photograph of high-speed, impulse pneumatic press. Fig. 2. Cross section through high-speed pneumatic press (all dimensions in millimeters, = diameter). ,; ! 2 D B To at- mosphere_ 5 cylinders kgf/cm 2 ?9 alns kgYcrn 2 Q- x Fig. 3. Press control system. 647 E, kgf=m . , m/sec ,ff, Ol . g I, I I L_I m 2 10 gO JO 0 50 80 ZGP, kg: Fig. 4 Fig. 5 ;m 2 Fig. 4. Variation of piston travel rate with pressure of compressed air in receiver. Fig. 5. Variation of work done during pressing with pressure of com- pressed air in receiver. The press is controlled by means of a low-pressure compressed air system. The raising of the ram to its upper position is performed with a two-way cock 1 enabling compressed air to pass into the space under the piston in the working cylinder (Fig. 3). After the plunger has been raised and secured in place, the cock 1 is turned so as to connect the space under the piston to the atmosphere. Unless this is done, the air trapped in the space under the piston will exert a braking action on the piston. The filling of the receiver with air, from a cylinder 3, is effected by means of a cock 4, which admits low-pressure air into the space under the piston in a two-way valve 5. The rod of the valve moves up, allow- ing high-pressure air to flow into the receiver of the press. The pressure is measured with a gauge 2. To set the ram of the press in motion, the cock 4 is turned to a position in which low-pressure air flows into the rod space of the valve 5. On moving down, the valve closes the high-pressure line and at the same time allows compressed air to flow from the cavity A of the press into the atmosphere. The operation of the press could easily be automated. The key characteristics o the press are given below. The curves in Figs. 4 and 5 were obtained by measuring ram travel times with an oscillograph and suitable gauges. The pressure in the receiver has not been raised above 75 kgf/cm 2. Technical Specifications Overall dimensions, mm: height 1550 width 840 length 840 Weight of falling parts, kgf 50 Maximum air pressure, kgf/em 2 75 Piston velocity, m/sec 16.9 Total weight, kgf 983 Work done during pressing, kgf-m 7150 Ratio of impulse energy to press weight, kgf-m/kgf 7.7 Thus, the new press fulfills the force and velocity requirements of experimental researc