1. Sheet metal stamping introduction
At room temperature, make use of the stamping die to apply pressure to the sheet metal material on a stamping press. Then, use a tool and die surface to form metal parts with the required shape and size. And this forming process is called stamping. Stamping includes a lot of sheet metal forming manufacturing processes. For example, bending, deep drawing, stretching, spinning, shaping, swelling, flanging, shrinking.
Metal stamping dies are process equipment that make sheet metal material to workpieces or semi-finished parts in the stamping process. When using a stamping die to produce the finished part, we can adopt rolled steel plates or steel strips mass-produced by foundries as blanks. In addition, there is no need to heat during manufacturing processes. Sheet metal stamping operations have advantages of high quality, high production efficiency, light weight and low cost. So people can see cold stamping products everywhere in airplanes, tractor, the automotive industry, motors, electrical appliances, instruments, etc. For example, stainless steel lunch boxes, dinner plates, cans, car covers, bullet shells, aircraft skins, etc. According to incomplete statistics, the stamping part accounts for about 60% in the automobile industry, 85% in the electronics industry, and 90% in daily hardware products.
2. Metal stamping dies types
2.1 Classify according to the process features
The first is punching die. It is a mold that separates the material along a closed or open outline. Such as blanking die, punching die, cutting die, slitting die, trimming die, etc. The second is the bending mold. It causes the sheet blank or other blanks to produce bending deformation along a straight line (bending line). So it can obtain a certain angle and shape of the workpiece.
And the third type is deep drawing mold. It makes the blank of the sheet metal material into an open hollow part. Or the deep drawing die makes the hollow part further change the shape and size. The last one is forming die. It directly copies the blank or semi-finished workpiece according to the shape of the convex and concave molds. However, the material itself only produces local plastic deformation. Such as bulging die, necking die, flaring die, undulating forming die, flanging die, shaping die, etc.
2.2 Classify according to the degree of process combination
The first is a single process mold. It is a mold that only completes one stamping process in one press stroke. The second is a compound mold, which has only one station. In one stroke of the stamping press, two or more processes are completed at the same time on the same station. The third type is progressive dies (also called continuous dies). In the feeding direction of the sheet metal blank, there are two or more stations. Besides, it completes two or more stamping manufacturing processes at different stations of progressive dies in one press stroke.
The last one is the transfer die, which combines the features of single process molds and progressive dies. It uses the robot transfer system to realize the rapid transfer of products in the mold. Thus, the transfer die can improve the efficiency of high volume production and reduce its cost. Also, adopting the forming process with this kind of mold saves materials cost and ensures a stable high quality.
The structure and complexity of various stamping dies are different, and the press die components are diverse. However, they are always divided into upper and lower die sets. The upper die set is generally fixed on the slider of the stamping press by a die handle. And it moves up and down along the rail of the press with the slider. In addition, the lower die set is fixed on the worktable of the stamping press. The classification and functions of the stamping die components are as follows.
3. Stamping die components
3.1 Stamping die parts for working
Working parts directly contact the stamping material. They apply pressure to it to complete the stamping process. Press die parts for working include a punch, a die, and a punch and die. As the name implies, the last one has the function of punch and die in the compound mold at the same time. They are also called forming parts, which are the most important parts of the die.
3.2 Press die parts for positioning
It is to determine the correct position of the material or process parts in the presses die. So the stamping part can obtain qualified quality requirements. The positioning parts of the feeding guide include guide pins, guide plates, and side pressure plates. The feeding fixed distance parts include the initial stopper pin, the stopper pin, the guide pin, and the side edge. Besides, press die components belonging to block materials or process parts include positioning pins and positioning plates.
3.3 Pressing and unloading parts
This kind of press die parts plays the role of pressing materials. It ensures that the waste or stamping part stuck on the punches and dies hole are removed or pushed. So the stamping operations can continue smoothly.
The function of the holding plate is to prevent the blank from moving and bouncing. And the function of the stripper plate is to facilitate discharging and cleaning up waste. Unlike others, that used in progressive dies has two types: fixed and elastic stripper plate. Usually, the unloading device refers to the removal of stamping metal parts or waste from the punch. The pushing and ejecting device means to unload the finished part or waste from the die. Generally, the ones installed in the upper molds are called push pieces; the ones installed in the lower die sets are called top pieces.
3.4 Guiding press die components
Their primary function is to ensure the accuracy of the mutual position between punches and dies. And they make sure that all parts of the mold maintain a good state of motion. They mainly consist of guide post, guide sleeve, guide plate, and so on.
3.5 Stamping die parts for supporting
They connect and fix the parts mentioned above on a specific position, or attaches a die with a press. They are basic parts of presses die, mainly including the upper die seat, lower die seat, fixed plate, backing plate, die handle, etc.
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3.6 Fastening parts
They are mainly used to fasten and connect various stamping die parts, such as various bolts, screws, round pins, etc. The guide parts and supporting parts mentioned above are called a mold base after assembly. It is the skeleton of the entire mold, and all press die components are fixed on it. And it bears all the loads in the stamping process. The upper mold base connects with the press slide block through a mold handle, and the lower one is fixed on the work table of the press with a screw pressing plate. Besides, between the upper and lower die sets, the guide device maintains its precise position. Then guide the movement of the punch to ensure a uniform gap during the forming process. The mold base and its components are standard, and there are certain technical conditions for it.
The mold base consists of a guide column and a guide plate. The most widely used one is the guide post and guide sleeve as the guide device. According to the different feeding methods, this standard mold base includes a rear guide pillar, a middle guide pillar, a diagonal guide pillar and a four guide pillar. When die designers start working, they can select it correctly according to the design requirements of punches and dies. The mold base’s size can be chosen directly from the standard by the perimeter size of the die.