How to Choose Press Brake Machine (CNC and NC)

NC hydraulic press brake and CNC press brake machine equipment nature of the field and process are different. Because some manufacturers are used as manufacturers, they are used as a comprehensive consideration when purchasing bending machines. It is best to consider what to buy for the final use of the machine, the deflection variables that can occur in the machine, the curved radius of the parts, etc. So as a decision maker, you have the responsibility to understand the performance, processing range, processing function, and processing accuracy of the equipment in detail. This responsibility is not small. Once you choose improperly, your production cost will rise, and the bending machine cannot be expected to recover costs. Therefore, there are several factors that must be weighed during decision-making.

Workpiece

The first important thing worth considering is the parts you want to produce. The main point is to buy a machine with the shortest and smallest tonnage of the workbench and the smallest tonnage to purchase a processing task.

Consider the material brand and maximum processing thickness and length. If most of the products produced are low-carbon steels with a thickness of 3mm and a maximum length of 2500mm, the free bending power does not necessarily need more than 80 tons. However, if you are engaged in a large number of bottom-up mold forming, you should consider a machine tool of about 150 tons. If the material to bend in production is the thickest of 6mm and the low-carbon steel within a length of 2500mm is free to bend, then the bending machine is required for 100 tons. If you bend some bending (correction bend) with the bottom concave mold, then a curved machine with a larger tonnage.

If most of the bending workpieces are 1250mm or shorter, consider that the tonnage of the bending machine is almost halved, which greatly reduces the purchase cost. Therefore, the length of the processing parts is very important for determining the specifications of the new model.

Scratch

When the bending machine is bent in the bending process, especially the bending-length workpiece, the longer the swinging workpiece will definitely occur. At the same load, the deflection of the 2500mm model workbench and the slider is 4 times that of the 1250mm model. That is to say, shorter machines need fewer pads to adjust, and they can produce qualified parts, reduce the adjustment of the pads and shorten the preparation time. However, the current CNC press brake machine has increased the hydraulic deflection compensation function in production design, reducing the adjustment of the device by the production operator, and improving the precision and production efficiency of bending.

The hydraulic deflection compensation function is controlled by the CNC system. The hydraulic oil enters the compensation oil cylinder through the magnetic service valve and pushes the workbench to the top. At the same time, deflection compensation is increased as the bending force increases, and it plays the role of deflection compensation. The material of processing materials is also a key factor. Compared with low-carbon steel, the load required for stainless steel usually increases by about 50%, while most materials are reduced by about 50%. Relevant standard bending pressure parameters can get relevant data from the bending machine manufacturer. This table shows the bending force required for the length per 1000mm under different thicknesses and different materials.

Part Curved Radius

During the bending product, the bending angle radius of the workpiece is also a factor to consider. When freely bending, the curved radius is 0.156 times the size of the V -slot opening. During the free bending process, the size of the V groove’s opening should be 8 times the thickness of the metal material. For example, when using a 12mm V groove opening size bending 1.5mm low-carbon steel, the curved radius of the parts is about R = 1.9mm. If the curved radius is close to the thickness of the material or less than the thickness of the plate, it is necessary to form a concave molding. However, the pressure required for sharing with the bottom concave mold is about 4 times larger than the free bend.

When the free bend is bending, pay attention to the gap between the upper and lower molds at the bottom of the stroke, and enough to compensate for the rebound and keep the material over 90 ° excessive bending. Generally, the rebound angle generated by the free bending mold on the new bending machine is ≤2 °, and the bending radius is equal to 0.156 times that of the lower mode opening distance. Therefore, it is generally free up and down mold bending processing. The angle of the mold is generally 86 ~ 90 °. At the bottom of the itinerary, there should be a gap between the thickness of the material. The formation angle is improved. Because the tons of bending with the bottom concave mold (about 4 times the free bending) reduce the stress of the rebound within the bending radius.

The printed bending is the same as the bending of the bottom concave mold, but the front end of the upper mold is processed into a needed radius required, and the upper and lower mold gaps at the bottom end of the stroke are less than the thickness of the material. Due to enough pressure (about 10 times the free bending), the upper end of the upper-end contact material is basically avoided, and the rebound is basically avoided. In order to choose the lowest tonnage specifications, it is best to plan for a curved radius greater than the thickness of the material, and use the free-bending method as much as possible. When the curved radius is large, it often does not affect the quality of the items and their future use.

Accuracy

Bending accuracy requirements are a factor that needs to be considered carefully. It is this factor that determines that you need to consider a CNC bending machine or an ordinary NC bending machine. If the curved accuracy is required to be ± 0.5 ° and cannot be changed, you must focus on the CNC bending machine.

The repeat accuracy of the cubes of the CNC press brake machine can generally guarantee that such accuracy and good molds must be used at an accurate angle of ± 0.01mm. The repeat accuracy of the NC bending machine is ± 0.5mm, and the deviation of ± 2 ~ 3 ° is generally generated under the conditions of the appropriate mold. In addition, the CNC bending machine is equipped with a fast-loading Model CNC system and a molding fixture. When you need to bend many small batch parts, this is an unquestionable reason for consideration.

Press Brake Tooling

The bending tooling also directly affects the accuracy of the bend. Therefore, it is necessary to check the wear of the mold for the mold. The method is to measure the length between the front end of the upper mold to the shoulder and the length between the lower mold shoulder. For conventional molds, the deviation per 10mm should be about ± 0.01mm, and the total length deviation should not be greater than ± 0.15mm. As for the fine grinding mold, the accuracy per 100mm should be ± 0.005mm, and the total accuracy must not be greater than ± 0.05mm. It is best to use the fine grinding mold for the CNC press brake machine, and the regular scale is used for the NC press brake.

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