How to Choose A Right Power Press

How to choose the right power press

When choosing a power press, you must clearly understand the purpose of its use. Fully understanding the processing methods, working methods, functions of punching machines, technical trends, etc. However, the processing method and the function of the press are very complicated and difficult to understand. The wrong choice of press machine will lead to a reduction in the efficiency of the press and may result in waste of equipment investment and other results.

There are three main tips of punching capacity:

 1. Pressure capacity: refers to the position of the slider at the bottom dead center in mm, which can produce a ton of pressure. This pressure is also called "nominal pressure" or "capacity" for short, and the unit is expressed in tons.

 2. Torque capability: refers to the position where the pressure capability is generated. That is the distance above the bottom dead center, which is also called the "capability generation point", and the unit is expressed in mm.

 3. Working capacity: refers to the maximum effective capacity that can be produced during one-stroke processing, and the unit is expressed in kg-m.

How to choose the right press

1. Correctly determine the processing method and operation method:

(1) Correctly determine the processing method and engineering

There are various methods for stamping, sometimes in combination with cutting. When selecting a punch, you should first check whether the desired processing method is appropriate for the target product and the appropriate number of processing projects. If the processing method is decided, the type of punch that should be selected is roughly determined.

(2) Degree of production

If a batch exceeds 3000~5000, it is more advantageous to use automatic feeding. When there are many projects and there is a large amount of production, it is necessary to consider the use of continuous processing and transfer processing, and also to review the automatic machinery such as high-speed automatic punching machines and transfer punching machines. The choice of general-purpose punching machine or automatic punching machine is mainly determined by the amount of production, but basically the necessary amount should be considered, and the appropriate inventory should be maintained frequently, and not only for the present but also for the future production market. Situation, technical trends, etc.

(3) The relationship between the shape, quality and size of the material

The shape and quality of the material should be determined in relation to the processing method, utilization rate, and material utilization rate. The shape of the material depends on any one of the coiled materials, fixed-length material or semi-processed product, and its size, and its operation method is also very different.

(4) How to supply materials, take out products, and dispose of waste

The above operations are collectively referred to as material handling (MATERIAL HANDLING). In the production plant in the all-round operation, material handling accounts for a large proportion. Therefore, material processing is not just a partial digestion of production, but must be considered from the rationalization of the factory as a whole. According to the material handling considerations, the functions required in the stamping machinery are very different.

(5) How to use the die buffer (DIE CUSHION)

During the extension process, additional die buffers should be considered in the single-action punch. Due to the high performance of the die buffer, it is possible to perform difficult drawing operations without using a double-action punch. The auxiliary device to improve the performance of the die buffer requires a locking device.

2. Select the punching capacity suitable for processing

(1) Calculate the processing pressure and processing pressure stroke curve

The maximum pressure required during processing and the pressure change during the processing stroke should be calculated. For multi-engineering processing, the pressure stroke curve of each project should be obtained, and the combined pressure stroke curve should be obtained by overlapping. Determine the maximum pressure and pressure stroke curve of the process to determine the pressure capacity that should be selected.

As for the decision of working ability, the frequency of processing should be decided first (processing several times per minute). The horsepower of the punching machine equipped with the automatic feeding device is preferably a motor with an increase of one horsepower. It is best not to choose the capacity of the punch just for the capacity of the press, but to select a punch with a commonly used capacity of 7580% of the nominal capacity.

(2) Eccentric load, degree of concentrated load

Of course, when one punch press is used with more than two dies or when a continuous die is used, there is of course an eccentric load, but most of the punching processes also have an eccentric load. Because the design of stamping capacity is usually based on the center load, it must be noted that the pressure capacity will decrease when there is an eccentric load. Therefore, for the operation of eccentric load, the punching capacity with sufficient margin should be selected. Most cold forging processes are extremely concentrated loads. For concentrated load operations, try to select a punch with a small die space.

(3) Calculate the reduction of the effective capacity of the die buffer

When the die buffer is installed, the drawing capacity of the punch is equal to the ability to deduct the buffer. Generally, the capacity of the buffer is 1/6 of the nominal capacity of the punch press. This value seems to be very small at first sight, but it is definitely not a low value but an appropriate value in the vicinity of the midpoint of the punch if it is compared with the effective drawing capacity available for drawing processing.

Although the high buffering capacity of 1/3 of the punching capacity is taken due to processing needs, in the case of a standard punching machine, the effective extension capacity near the midpoint of the stroke will be significantly reduced (in extreme cases, the ability to push the buffer will be lost), So pay more attention.

Therefore, for such a high buffering capacity, the torque capacity of the press should also be selected to be higher. If the buffering capacity is raised too high, it will become an uneconomical structure due to the mismatch of torque capacity, so when it is necessary, it is better to consider using a double-acting punch.

3. Defining the dimensional accuracy of processed products

The necessary accuracy of the processed product is determined by the use of the product and its connection with the next project. In the actual stamping process, the thickness of the material, the volume of the blank block (during extrusion processing), the material (related to the deformation resistance) and the degree of lubrication, etc., and the wear of the mold as the production progresses There are many reasons for poor machining accuracy.

If high processing precision is particularly required, a high-rigidity punch or a punch with a large capacity (with sufficient pressure capacity for its processing) should be selected. However, even if a large-capacity punch is used for the C-type punching machine, it is not effective, and it is necessary to choose a punch with high rigidity.

4. Fully understand the function of the punch

(1) Fully investigate the specifications of the punch catalog

The catalog specifications indicate the main capabilities and sizes of the punch presses and are the basis for selecting the punch presses. The expression of punching capacity usually only indicates the pressure capacity, and the torque capacity and working capacity should be combined for review. The punching machine for blanking should shorten the stroke and increase the SPM of this part. Such as the height of the die, the width of the working surface, the T-groove of the working surface of the die, the buffer pin hole, etc. must be determined in connection with the die used.

It should be noted that the excessive requirements on the specifications of the punch press due to the limitations of the plant have a negative impact on the function of the punch press. Therefore, if there is no problem in the specifications, you should choose a standard-size press, and a press with stable functions and good results.

(2) Selection of attachments for punch

Appropriate use of accessory devices can increase productivity, so various accessory devices should also be fully reviewed.

In order to increase production, the best method is to use an automatic feeding device for continuous processing. If the work such as the supply of materials and the removal of products is too complicated and continuous processing is difficult, a timer (TIMER) can be used for continuous operation within a limited time to improve production efficiency.

The use of conveyor or unloader (UNLOADER) device is also beneficial to improve productivity. For example, when changing the mold frequently, the quick mold exchange (Q.D.C) device and the die fixture are also beneficial. Can consider slow running device, material replacement, product stacking device, etc. The stamping shall be equipped with stepless speed change device with roller feeding. And should take into account the future need to prepare the device buffer and feeder (FEEDER) or rotary cam (ROTARYCAM). However, if too many complicated attachments are equipped, the failure rate will be increased, and the maintenance trouble will be increased. Therefore, the punch attachments must be properly selected.

(3) The flexibility of relevant functions should be reviewed

In order to maintain a good utilization rate, the function of the punching machine must meet the market trend of fierce model replacement. That is, we should review the functions that can be adapted to both mass production and small production, as well as the functions that can be followed in the future model replacement. For example, in order to facilitate synchronization, the driving power of the automatic feeding device is usually taken from the crank shaft of the punch. In this way, it will become a punch with an automatic feeding device and enhance the specificity of a certain operation.

If a separate drive feeder is used, because of its independent power, it can be easily moved, can be freely combined with any punch, and can respond to changes in operations.

(4) Choose a punch that is easy to maintain and has high reliability

Due to the large production volume and the usually need for several engineering operations, stamping products have a great impact on the overall production if they are shut down due to the failure of the punch press. Therefore, you should choose a punch that is easy to maintain, inspect, and has high reliability (especially the stability and durability of the clutch, brake, and electrical operation relationship).

(5) Security

Stamping operations are operations with a high risk of disasters, so full consideration should be given to safety countermeasures. When selecting a punching machine, one with a safety equipment function should also be selected. There will be no accidents when there is an erroneous operation, and the operation can be performed safely. Therefore, the operation of the punching machine should have various interlock devices, shearing type and hydraulic overload safety devices, two-handed operation, light type, mechanical type and other safety devices for operation.

(6) Noise and vibration

The noise and vibration of stamping factories are restricted by laws and regulations due to pollution problems. The operating environment is an important issue in the future. Therefore, it is necessary to incorporate noise and vibration countermeasures into the stamping equipment in the future.