Different Metal Stamping Dies Design Points You Should Know

Stamping is applying pressure to various sheets or blanks of different sizes, using a die and stamping equipment (press, also known as punch press) to deform or separate them and obtain parts of a certain shape or size and performance. The general production is done with vertical presses, thus determining that the main movement of the stamping process is up and down, in addition to the various movements between the die and the sheet and the structural parts in the die.

Mechanical motion can be divided into three basic forms of motion: sliding, rotating and rolling, all of which exist in the stamping process. Still, the characteristics of each form of motion are different and have different effects on stamping.

Since there are such diverse motions in the stamping process, should strictly control all kinds of motions in the stamping die design to meet the requirements of the die design; at the same time, all kinds of mechanical motions should be flexibly used in the design according to the specific situation to meet the requirements of the products.

The main motion of the stamping process is up and down motion. Still, the design of inclined wedge structure, rotary pin structure, roller structure and rotary cut structure in the mould can transform the main motion into horizontal motion, rotation in the mould and rolling in the mould accordingly. These special structures in the mould design are more complicated, and the cost is also higher, but to achieve the shape and size requirements of the product, it is an effective solution.

Stamping mold

Stamping dies


The basic motion of the blanking process is that the unloading plate first makes contact with the sheet and presses it firmly, the convex die descends to make contact with the sheet and continues to descend into the concave die, the convex and concave dies and the sheet produce relative motion leading to the separation of the sheet. The convex and concave die separate, and the unloading plate pushes the workpiece or scrap off the convex die to complete the blanking motion. To ensure the quality of punching, it is necessary to control the movement of the unloading plate, which must be in contact with the plate material before the convex die, and the pressing force must be sufficient. Otherwise, the quality of the cutting surface of the punched part is poor, the dimensional accuracy is low, the flatness is bad, and even the die life is reduced. Designing the drop punching die according to the usual method, it is often difficult to separate the workpiece from the scrap side after punching. On the premise of not affecting the quality of the workpiece, it is possible to add some protruding restriction blocks on the unloading plate of the convex and concave die so that after the movement of drop punching is completed, the unloading plate of the concave die will push the workpiece out of the concave die first. Then the unloading plate of the convex and concave die will push the scrap down from the convex and concave die so that it will b separate the workpiece and the scrap naturally.

For some large stamping parts with local projection, the unloading plate can be used to unload the scrap from the die. To ensure that the material is deformed to achieve the purpose of pressing when the die is in contact with the sheet and then continuing the punching movement, the die can be reduced by one step and reduced cost. Some punching dies have many punching holes and require a large punching pressure, which is unfavourable to punching production, even without a punching machine of sufficient tonnage. One simple method is to use 2 to 4 batches of different lengths and let the punching motion be carried out in time when punching, which can effectively reduce the punching force.

For those punches with holes on the bending surface that require high positional accuracy (e.g. concentricity of two holes on the opposite side bending, etc.), it isn’t easy to achieve the hole position requirement if the hole is punched first and then bent. It is necessary to design a bevelled wedge structure to punch the hole after bending and can achieve the purpose by using the punching motion in the horizontal direction. Those who need to do the trimming process when the flanging and drawing height requirements are strict can use a similar structure design.

Stamping dies

Bending die

The basic movement of the bending process is that the unloading plate first contacts with the sheet and presses it to death, the convex die descends to contact with the sheet and continues to descend into the concave die, the convex and concave dies and the sheet produce relative movement, resulting in deformation and bending of the sheet. The convex and concave die separate, and the top bar (or slider) on the bending concave die pushes out the bending edge to complete the bending movement. Unloading the plate and the movement of the top bar is very critical. To ensure the quality of bending or production efficiency, one must first control the movement of the unloading plate so that it is in contact with the plate material before the convex die, and the pressure must be sufficient. Otherwise, the bent part size accuracy is poor, with bad flatness; secondly, ensure that the top bar force is sufficient to enable it to push out the bent part smoothly, otherwise the bent part deformation and low production efficiency. For high precision requirements of the bending parts, we should pay special attention to one point, preferably in the bending movement, to have a movement dead point. That is, all relevant structural parts can touch dead.

Some workpiece bending shape is more peculiar, or bending can not be in the normal way from the concave mould off, then, often need to use the diagonal wedge structure or turn the pin structure, for example, the use of diagonal wedge structure, can be completed less than 90 degrees or back hook type bending, the use of turn the pin structure can realize the simple round parts once formed.

It is worth mentioning that for some housing parts, such as computer floppy drive housing, because of its long bending edge, the elbow and the sliding between the plate material, in the bending, it is easy to rub out the hair chips, the material galvanized layer off, frequent polishing bending punch effect is also not ideal. The usual practice is to bend the punch titanium plating, improve its finish and wear resistance, or in the bending punch R angle embedded roller, the elbow and the plate material bending, sliding into rolling due to rolling. The friction is much smaller than sliding, so it is difficult to rub the workpiece.

Deep drawing die

The basic movement of the deep drawing process is that the unloading plate first contacts with the plate material and presses firmly, the convex die descends to contact with the plate material and continues to descend into the concave die, the convex and concave dies and the plate material produce relative movement, resulting in the volume of the plate material forming. The convex and concave die separate, and the concave die slider pushes the workpiece out to complete the deep drawing movement.

The movement of the unloading plate and slider is very critical; to ensure the quality of the deep-drawing parts, the movement of the unloading plate must be controlled so that it can contact with the plate material before the convex die, and the pressing force should be enough. Otherwise, the deep-drawing parts are easy to wrinkle or even crack; secondly, the pressure of the concave die slider is enough to ensure the flatness of the bottom surface of the deep-drawing parts.

Deep drawing compound die design is reasonable and can well control structural parts’ movement process to achieve the multi-process combination purpose. For example, the typical design of compound dies for deep-drawing edge punching with drop material.

In addition, some decorations and daily necessities need to have rolled edge (or rolled edge) process. The mould design also uses the roller structure, so the rolling friction in the rolling edge process is very small, and it is not easy to rub the work. The surface of the workpiece is not easily scratched.

For those deep-drawing structural parts that need to be rotated in the motor, the height of the cut edge, the jumping degree and other requirements are quite high, so it is necessary to design a special rotary cutting structure in the mould using the rotary (cutting) movement to trim the edge, which can not only ensure the high dimensional accuracy of the cut edge but even the burr of the cut edge and the punching pattern are also quite beautiful. It is worth mentioning that this rotary cutting structure has been very easy to make after the actual design improvement and has been used in the continuous deep drawing die.

deep drawing die

Continuous Die

Continuous dies often include stamping processes such as punching, bending and drawing at the same time, so the mechanical movement in the stamping process also includes the basic movement patterns of these three processes, and the control of movement in continuous dies should be divided into each basic process for control separately.

Usually, the continuous die requires to speed up the stamping speed continues to improve production efficiency. In the continuous die design, some stamping parts with more complex and special shapes, whose stamping motion is more time-consuming, can be decomposed into a more efficient stamping motion.

Continuous Die