You Want to Know the Structural Characteristics of Cold Press Molds?

After years of practice in designing cold stamping molds, I deeply appreciate that whether the structure of the designed cold stamping mold is reasonable and usable is crucial to the production of qualified workpieces and the success of new products developed. A set of molds with a simple structure consists of only a few dozen parts. However, we must not underestimate it. At the beginning of the design, what kind of mold structure is chosen? Is it a front-mounted mold structure (i.e., the concave mold is mounted on the lower mold base)? Or is it an inverted (reverse) mold structure (i.e., a convex mold mounted on the lower die base)? Should I choose a single-process mold structure? Or should we choose a compound mold structure? This is a very worthy in-depth discussion of the topic in front of each of our mold workers, which is a great article to do.

Table of Contents

when to choose the positive mold structure

Structural characteristics of front-loading molds

The structure of a front-loading die is characterized by the fact that the concave die is mounted on the lower die base. Therefore, the workpiece or scrap can be easily dropped into the scrap hole on the punching table, whether for workpiece drop, punching, or other processes. Therefore, the flow of the workpiece or scrap does not have to be considered when designing the main die. This results in a very simple and practical tool structure.

The advantages of the positive assembly mold structure

 (1) Because of the simple mold structure, the mold manufacturing cycle can be shortened, which is conducive to the development and development of new products. (2) It is more convenient to use and maintain. (3) It is easier to install and adjust the clearance of the convex and concave molds (compared to the reverse mold). (4) Low mold manufacturing cost, which is conducive to improving the economic efficiency of enterprises. (5) Since the crimping force is always present throughout the stretching process, it is suitable for stretching non-rotating body parts.

Disadvantages of the positive mold structure

 (1) Due to the accumulation of workpieces or scrap in the concave mold hole, the group rising force in the concave mold hole is increased. Therefore the concave must increase the wall thickness to improve its strength. (2) Due to the accumulation of workpieces or scrap in the concave die hole, the concave die edge must then be machined with a drop slope. In some cases, the reverse hole of the die edge (discharge hole) has to be machined. This extends the cycle time of the mold and increases the cost of machining the mold.

Principle for the selection of the structure of the positive mold

In summary, we can see that the design principle we should follow when designing a punching die is to give preference to a positive die structure. Only when the technical requirements of the workpiece can be met under the front-loading die structure can other forms of die structure be considered.

aluminum alloys stamping products

When to choose the inverted (reverse) mold structure

Structural characteristics of inverted molds

The structure of a reverse mold is characterized by the die being mounted on the lower die base, so we have to use a pop-up unloading device to unload the workpiece or scrap from the die. The concave die is mounted on the die base, so there is the problem of discharging the workpiece or scrap from the concave hole.

Advantages of the inverted die structure

(1) Due to the use of a pop-up unloading device, the punched workpiece is flat and has good surface quality. (2) Since the workpiece or scrap is punched down from the hole of the die by using the beating rod, the workpiece or scrap does not accumulate in the hole of the die, which can reduce the rising force of the workpiece or scrap on the hole. Thus, the wall thickness of the die can be reduced, making the shape size of the die smaller and saving mold material. (3) As the workpiece or scrap does not accumulate in the die hole, the wear of the die edge by the workpiece or scrap can be reduced, and the number of times sharpening of the die can be reduced, thus improving the service life of the die. (4) As the workpiece or scrap does not accumulate in the die, there is no need to machine the reverse hole of the die (discharge hole). This shortens the mold-making cycle and reduces mold processing costs. (5) Since the crimping force only acts before the flat blank is fully drawn into the concave die, it is suitable for stretching rotating bodies.

Disadvantages of flip-mold structure

(1) The mold structure is more complex (compared to the front-mounted mold). (2) It is difficult to install and adjust the clearance between the convex and concave molds (as opposed to the front-loading molds). (3) Trouble in removing workpieces or scrap (it is better to use compressed air to blow them away).

Principles for the selection of flip-mold structures

In summary, only when the surface of the workpiece is flat, the profile is complex, asymmetrical, or the blank is thin, and when the rotating body is stretched, the flip die structure is chosen.

Electrical stretching precision stamping

When to choose single process mold structure

The so-called single-process die structure means that only one process can be completed within one stroke of the punch.

Advantages of single process die structure

(1) simply die structure, short manufacturing cycle, low processing cost; (2) good die versatility, not limited by the size of the stamping parts, i.e., suitable for the production of small and medium-sized stamping; also suitable for the production of some large shape size, thicker stamping parts.

Disadvantages of the single-process die structure

(1) low precision of the parts; (2) low production efficiency.

Principles for the selection of single-process tooling structures

In summary, it can be seen that, for some precision, requirements are not high, the production batch is not a large workpiece, and the use of a single process mold or more appropriate. Especially now, our country is implementing a socialist market economy. The development and research of new products are of vital importance to every enterprise. And for some new products that need to be produced by stamping, a requirement is put forward: a short development cycle, fast development, and low manufacturing cost are required. The products developed in this way can occupy the market quickly. In this regard, single-process molds can meet this requirement, making it more practical.

When to choose the composite mold structure

The so-called compound die structure is to complete more than two stamping processes within one stroke of the punching machine. During the completion of these processes, the punched material does not need to be fed and moved.

Advantages of the composite mold structure

 (1) High accuracy of the parts made. As it is within one stroke of the press, several stamping processes are completed. As a result, there is no cumulative positioning error. The relative position of the punched parts’ shape and the parts’ dimensional consistency are very good, and the parts are straight. It is suitable for punching thin materials and brittle or soft materials. (2) High production efficiency. (3) Compact mold structure and small area.

Disadvantages of compound die structure

(1) The thickness of the convex and concave die biscuit cannot be too thin (shape and inner shape, inner shape and inner shape) so as not to affect the strength. (2) Convex and concave die sharpening are sometimes not convenient. This is especially the case when the die is being punched and shaped simultaneously.

Principles for the selection of compound mold structures

From the above, it can be seen that only when the precision of the part is high, the production batch is large, and the surface is flat; then, the compound mold structure chosen.

Conclusion

We can see the above analysis and comparison of several mold structures. Mold structure is like anything in the world; there are two sides. That is, there is a good side and a disadvantage. There is no such thing as perfection. Therefore, when choosing the mold structure, we should weigh the advantages and disadvantages according to the various forms and consider them comprehensively. Never according to the rules and regulations, the box is rigid. It should be fully according to the production scale of each production enterprise, stamping equipment status, and the current situation of the mold processing capacity, flexible master. In short, as long as each mold worker exchanges experience with each other, takes advantage of each other’s strengths and weaknesses, and dares to innovate, explore, and practice, there will be many mold structures that are novel, simple, easy to use, and maintain, and safe to operate.

 

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