TECHNOLOGICAL ASPECTS OF ENSURING QUALITY OF PARTS PRODUCED BY CUTTING-PUNCHING OPERATION DURING PNEUMATIC IMPACT STAMPING

Abstract

The paper considers the issues related with technological capabilities and features of the process of cutting-punching of sheet-metal parts with an elastic medium of pneumatic impact stamping, taking into account the indicators of their quality and accuracy, and also suggests effective ways to improve them. One of the promising methods for producing high-precision parts, including those with a complex profile, is a shaping method based on the technology and equipment of pneumatic shock stamping with an elastic medium on the TA-1324 in-stallations. The advantages of this method are environmental cleanliness, safe operation, wide technological capabilities, mobility and versatility, low labour and energy costs. At these installations it is advisable to perform formative operations of separation (cutting-punching) and shallow shaping both as a separate operation and together with cutting-punching. As a workpiece for the study the sheet material of the following grades was used: steel 08kp, aluminium alloy AMG-M, steel 12X18H10T. The thickness varied within the range from 0.5 to 2.5 mm. Dies and copier punches were made of U8A steel, followed by heat treatment to a hardness of HRC 56-62. An analysis of the experimental studies of punching-cutting processes allows us to conclude that with an increase in the number of stamped parts, there is an increase in size deviations from their nominal values. This increase is due to the wear of operating elements (copier punches and dies). At the same time, the sizes of the copier punches are reduced, and the sizes of the matrices are increased. The absolute values of deviations do not depend on the type of operations; their values, both during cutting and punching, are almost the same in each of the samples taken. The process of pneumatic impact stamping, where a hammer with a bevelled end was used, has a similar character. The paper also proposed and tested ways to improve pneumatic impact stamping, providing cutting, punching of parts from sheet copper, aluminium alloys with a thickness of 0.3 to 3 mm and mild steel up to 3 mm thick. The roughness of the cutting surface is in the range Ra = 0.3 to 0.6 μm, and in the case of high-strength materials up to 2.5 mm thick, the roughness of the cutting surface is Ra = 0.6 to 1.0 μm, depending on the contour configuration that is cut down or punched.