in the progressive die, the shape of the stamping is formed by punching the remaining material around the stamping. the main reason for the turning and twisting of punching parts is the influence of punching force. when punching, due to the existence of the punching gap, the material is stretched on one side of the die (the material is warped upward) and compressed on the side of the punch. when using the unloading plate, use the unloading plate to press the material to prevent the material on the die side from warping upwards. at this time, the stress state of the material changes accordingly. as the unloading plate increases its pressing force, the material on the side of the punch is stretched (the compression force tends to decrease), while the material on the die surface is compressed (the tension tends to decrease). the overturning of the stamping part is caused by the stretching of the material on the die surface. therefore, when punching, pressing and compressing the material is the key point to prevent the punching from turning over and twisting.
in daily production, there will be situations where the size of the punching hole is too large or too small (may exceed the specification requirements) and the size of the punch is quite different from that of the punch. in addition to considering the design size, processing accuracy and punching in addition to factors such as gaps, the following aspects should also be considered to solve.
(1). when the punching edge is worn, the tensile stress on the material increases, and the tendency of stamping parts to turn over and twist increases. when material turning occurs, the size of the punching hole will become smaller.
(2). the strong pressure on the material will cause plastic deformation of the material, which will cause the size of the punching hole to become larger. when the strong pressure is reduced, the punching size will become smaller.
(3). the shape of the cutting edge of the punch. if the end is trimmed with a slope or an arc, the punching force will be reduced and the punching will not be easily turned over and twisted, so the punching size will tend to be larger. however, when the end of the punch is flat (no slope or arc), the size of the punching hole will be relatively smaller.
in specific production practice, specific analysis should be made for specific problems, so as to find out the method to solve the problem. the above mainly introduces the reasons and countermeasures for the turning and twisting of stamping parts during punching.
reasons and countermeasures for turning over and twisting of stamping parts during bending
(1). it is caused by the burr of the punched parts during punching. it is necessary to study the punching edge, and pay attention to check whether the punching gap is reasonable.
(2). turnover, twisting and deformation of punched parts have occurred during punching, resulting in poor forming after bending, which needs to be solved at the punching and unloading station.
(3). due to the instability of stamping parts during bending. mainly for u-shape and v-shape bending. to deal with this problem, guiding the stamping parts before bending, guiding them during the bending process, and pressing the material during the bending process to prevent the stamping parts from slipping during bending are the key points to solve the problem.
method of suppressing turning over and twisting of stamping parts
(1). reasonable mold design.
in the progressive die, the arrangement of the blanking sequence may affect the forming accuracy of the stamping parts. for the blanking of small parts of stamping parts, it is generally arranged to arrange larger area punching blanking first, and then arrange smaller area punching blanking to reduce the influence of punching force on the forming of stamping parts.
(2). press the material.
to overcome the traditional mold design structure, open a material-holding gap on the stripping plate (that is, when the mold is closed, the stripping plate and the die fit together, and the gap between the stripping plate and the die at the place where the material is accommodated is the material thickness t-0.03 ~0.05mm). in this way, the unloading plate moves smoothly during stamping, and the material can be compressed. the key forming part, the unloading plate must be made into an insert structure, so as to facilitate the solution of the wear (pressure) damage caused by the long-time stamping on the pressing part of the unloading plate, and the material cannot be compressed.
(3). added pressure function.
that is, thicken the size of the pressing part of the unloading insert (normal unloading insert thickness h 0.03mm) to increase the pressure on the material on the die side, thereby inhibiting the stamping parts from turning over and twisting during punching.
(4). the end of the cutting edge of the punch is repaired with a slope or an arc.
this is an effective way to reduce the stress of cutting. reducing the buffer cutting force can reduce the tensile force on the material on the die side, thereby achieving the effect of inhibiting the stamping parts from turning over and twisting.
(5). during daily mold production, care should be taken to maintain the sharpness of punching and concave die edges. when the punching edge is worn, the tensile stress on the material will increase, so that the stamping parts will tend to turn over and twist.
(6). unreasonable blanking clearance or uneven clearance is also the cause of turning over and twisting of stamping parts, which need to be overcome.