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Purchase instructions of hydraulic bending machine and NC bending machine
Several problems to be considered in selecting bending machine.
The properties of hydraulic bending machine and CNC bending machine equipment in their processing fields and processes are different, because some manufacturers use them as a comprehensive consideration when purchasing bending machines. First, carefully consider what to buy from the use of the machine, the possible deflection of the known machine, the bending radius of parts, etc. Therefore, as a decision-maker, you have the responsibility to understand the performance, processing range, processing function, processing accuracy and so on of the equipment in detail. This responsibility is not trivial. Once you choose improperly, your production cost will rise, and the cost recovery of the bending machine can not be expected. Therefore, several factors need to be weighed in decision-making.
The first important thing worth considering is the parts you want to produce. The key point is to buy a machine with short worktable and small tonnage that can complete the processing task. Carefully consider the material grade and large machining thickness and length. If most of the products produced are mild steel with a thickness of less than 3mm and a large length of 2500mm, the free bending force does not have to be greater than 80t. However, if you are engaged in a large number of bottomed die forming, you may consider a machine tool of about 150 tons. If the material to be bent in production is 6mm thick and 2500mm long, when the low carbon steel is bent freely, it should be considered that a bending machine of 100t is required. If some bends are formed by bending with the bottom die (correcting the bending), then a larger tonnage bending machine is needed. If most of the bent workpieces are 1250mm or shorter, the tonnage of the bending machine is almost halved, so as to greatly reduce the purchase cost. Therefore, the length of processed parts is very important to determine the specifications and models of new models.
Bending machine in the bending process, especially when bending long size workpieces, there will be deflection. The longer the workpieces, the greater the deflection. Under the same load, the deflection of worktable and sliding block of 2500mm model is 4 times that of 1250mm model. This means that shorter machines require less gasket adjustment to produce qualified parts. Reducing gasket adjustment shortens the preparation time. However, the current CNC hydraulic bending machine has increased the hydraulic deflection compensation function in the production design, which reduces the adjustment of the equipment by the production operator, and improves the bending accuracy and production efficiency at the same time. The hydraulic deflection compensation function is controlled by the numerical control system. The hydraulic oil enters the compensation cylinder through the magnetic servo valve to push the workbench upward. At the same time, the deflection compensation force increases with the increase of bending force, which 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 is usually increased by about 50%, while the load required for most soft aluminum sides is reduced by about 50%. The relevant standard bending pressure parameters can be obtained from the bending machine manufacturer. This table shows the bending force required for every 1000mm length under different thickness and different materials.
Bending radius of parts:
In the process of bending products, the bending angle radius of the workpiece is also a factor to be considered. When free bending is adopted, the bending radius is 0.156 times of the opening size of V-groove. During free bending, the opening size of V-groove shall be 8 times the thickness of metal material. For example, when bending 1.5mm mild steel with 12mm V-groove opening size, the bending radius of the part is about R = 1.9mm. If the bending radius is close to or less than the thickness of the material, it must be formed with a bottom die. However, the pressure required for forming with the bottom die is about 4 times greater than that of free bending. During free bending, pay attention to the gap between the upper die and the lower die at the bottom of the stroke and the excessive bending sufficient to compensate for the rebound and keep the material at about 90 °. Generally, the springback angle generated by the free bending die on the new bending machine is ≤ 2 °, and the bending radius is equal to 0.156 times of the opening distance of the lower die. Therefore, it is generally free to bend the upper and lower dies, and the die angle is generally 86 ~ 90 °. At the bottom of the stroke, there should be a gap slightly greater than the material thickness between the upper and lower molds. The forming angle is improved because the tonnage of bending with the bottom die is large (about 4 times that of free bending), which reduces the stress that usually causes springback within the bending radius. Embossing bending is the same as bending with the bottom die, except that the front end of the upper die is processed into the required bending radius, and the gap between the upper and lower dies at the bottom of the stroke is less than the material thickness. Due to the application of sufficient pressure (about 10 times of free bending) to force the front end of the upper die to contact the material, the rebound is basically avoided. In order to select the low tonnage specification, it is better to plan for the bending radius greater than the material thickness, and adopt the free bending method as much as possible. When the bending radius is large, it often does not affect the quality of the finished part and its future use.
The requirement of bending accuracy is a factor that needs careful consideration. It is this factor that determines whether you need to consider a NC bending machine or an ordinary NC bending machine. If the bending accuracy is required to be within ± 0.5 ° and cannot change, you must focus on the NC bending machine. The repeat accuracy of the slide block of the NC bending machine can generally be guaranteed to be ± 0.01mm. Such accuracy and good die must be adopted for the accurate forming angle. The repetition accuracy of the slide block of NC bending machine is ± 0.5mm, and generally there will be a deviation of ± 2 ~ 3 ° under the condition of using appropriate die. In addition, CNC bending machines are equipped with rapid tooling CNC system and tooling fixture, which is an indisputable consideration when you need to bend many small batch parts.
The bending die also directly affects the bending accuracy. Therefore, the wear degree of the die should be checked by measuring the length from the front end of the upper die to the shoulder and the length between the shoulder of the lower die. For conventional molds, the deviation per 10mm shall be about ± 0.01mm, and the total length deviation shall not be greater than ± 0.15mm. As for the precision grinding die, the accuracy per 100mm shall be ± 0.005mm, and the total accuracy shall not be greater than ± 0.05mm. The fine grinding die is used for NC bending machine, and the conventional die is used for NC bending machine.
Conclusion: as a user or manufacturer of equipment, Jiangsu Liwei machine tool company provides you with an economical and practical bending machine. Of course, many factors should be considered. At the same time, we should proceed according to our actual situation. The above points are only a brief overview of some one-sided problems.