How To Choose The Right Press Brake?

Different press brakes vary in the areas they work in and their process nature, so it is important to make a thorough consideration when purchasing a bending machine.

Press-Brake

When buying a press brake machine, you can start by considering the end use of the machine, possible deflection, bending radius of the part and other factors. As the decision maker, it is your responsibility to understand in detail the performance of the machine, the processing range, the processing functions, the processing accuracy, etc.

This responsibility is actually very important. If you do not choose properly, your production costs will climb and the bending machine may not pay for itself as expected. Therefore, here are a few aspects that must be weighed in the purchase!

Parts

The first consideration is the part you are going to produce. You need to buy a machine that can perform the task with the shortest table and the lowest tonnage. Thus, you need to carefully consider the material, thickness and length of the plate to be processed. If most of the products to be produced are mild steel within 3mm thick and up to 2500mm long, then the free bending force is only 63 tons.

However, if you are doing a lot of bottom die forming, you should probably consider a machine with a capacity of about 150 tons. If the material to be bent is mild steel with a maximum thickness of 6mm and a length of 2500mm, then a press brake of 100 tons or more is required.

If you want to perform correction bending, then you need a larger tonnage bending machine. If most of the bent parts are 1250mm or shorter, then consider a press with half the tonnage, thus greatly reducing the purchase cost. Therefore, the length of the processed part product is quite important to determine the specifications of the new model.

Deflection

In bending process, especially when bending long size workpiece, the longer the workpiece, the greater the deflection. Under the same load, a 2500mm model table and slide will deflect four times as much as a 1250mm model. This means that a shorter machine requires less shim adjustment to produce a qualified part, and less shim adjustment reduces lead time.

However, CNC hydraulic press brakes are now designed for production with hydraulic deflection compensation, reducing the need for production operators to adjust the equipment while improving bending accuracy and productivity. The hydraulic deflection compensation function is controlled by the CNC system, and the hydraulic oil enters the compensation cylinder through the magnetic servo valve, thus pushing the table upward.

At the same time, the deflection compensation force increases as the bending force increases, providing deflection compensation. The material of the processing material is also a key factor. Compared to mild steel, stainless steel usually requires about 50% more load, while most materials are about 50% less on the soft aluminum side. Relevant criteria for bending pressure parameters can be obtained from the press brake manufacturer.

Bending radius of parts

During bending, the bending corner radius of the workpiece is also a factor to be considered. When using free bending, the bending radius is 0.156 times the size of the V-slot opening. In free bending, the V-groove opening should be 8 times the thickness of the metal material. For example, when bending 1.5mm mild steel with a 12mm V-groove opening, the bending radius of the part is approximately R=1.9mm.

If the bending radius is close to the material thickness or less than the thickness of the plate, the bottom die must be used for forming. However, the pressure required for forming with the bottom die is about four times greater than that for free bending. In free bending, pay attention to the gap between the upper die and the lower die at the bottom of the stroke, as well as to the overbending of the material at about 90° to compensate for springback.

In general, the free bending die on the new bending machine produces a rebound angle ≤ 2 °, and the bending radius is equal to 0.156 times the opening distance of the lower die. Therefore, in the general free upper and lower die bending process, the die angle is generally 86 ~ 90 °.

At the bottom of the stroke, there should be a gap between the upper and lower dies slightly larger than the material thickness. The forming angle is improved because the tons of bending with the bottom die are larger (about 4 times as much as free bending), reducing the stresses that usually cause springback within the bending radius.

Impression bending is the same as with bottom concave die bending, except that the front end of the upper die is machined to the desired bend radius and the gap between the upper and lower dies at the bottom of the stroke is less than the material thickness. Springback is basically avoided by applying sufficient pressure (about 10 times the free bend) to force the front end of the upper die into contact with the material.

In order to choose the lowest tonnage specification, it is best to plan for a bending radius greater than the material thickness and to use the free bending method as much as possible. A larger bending radius often does not affect the quality of the finished part and its future use.

Accuracy

Bending accuracy is a factor that needs to be carefully considered, and it is this factor that determines whether you need to consider a CNC press brake or a regular NC press brake. If the bending accuracy requirement is within ±0.5° and cannot be changed, you will need to focus on a CNC press brake.

NC press brakes have a repeatability of ±0.5mm and generally produce a deviation of ±2 to 3° with the right tooling. In addition, NC press brakes are equipped with quick-loading CNC systems and mould-loading fixtures, which is an indisputable reason to consider when you need to bend numerous small batch parts.

Tooling

Bending tooling also directly affects the accuracy of bending, so it is important to check the wear condition of the tooling by measuring the length from the front end of the upper die to the shoulder of the table and the length between the shoulders of the lower die.

For regular dies, every 10mm deviation should be about ±0.01mm, and the total length deviation should not be greater than ±0.15mm. As for fine grinding dies, every 100mm accuracy should be ±0.005mm, and the total accuracy should not be greater than ±0.05mm. It is better to use fine grinding dies for NC press brake machines and regular dies for NC press brake machines.

In conclusion

As a machine user or manufacturer, when purchasing a press brake, the main purpose is to procure an economical and practical one, which certainly is to take into account many factors, but also based on your actual situation to make the final decision.

We use cookies to enable all functionalities for best performance during your visit and to improve our services by giving us some insight into how the website is being used. Continued use of our website without having changed your browser settings confirms your acceptance of these cookies. For details please see our Privacy Policy .