Points for attention in the selection and purchase of bending machine
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Points for attention in the selection and purchase of bending machine

Views: 131     Author: Site Editor     Publish Time: 2020-06-05      Origin: Site

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Points-for-attention


Bending machine in its processing field and the nature of the process is different, so as a manufacturer in the purchase of bending machine for a comprehensive consideration.

It is best to think carefully about what to buy in terms of the end use of the machine, the known possible torsion of the machine, the bending radius of the part, etc. Of course, as the decision maker you have the responsibility to understand the performance of the equipment, the scope of processing, processing function, processing accuracy and so on. This responsibility is no small matter, once the wrong choice, your production costs will rise, bending machine can not expect to recoup the cost. Accordingly, a few factors must be tried when choose and buy according to quantity!

The workpiece

The first important thing to consider is the parts you want to produce. The point is to buy a machine that can complete the processing task with the shortest worktable and the smallest ton. Carefully consider the material grade and the maximum machining thickness and length. If most products are made of mild steel with a thickness of less than 3mm and a maximum length of 2500mm, the free bending force need not be greater than 80 tons. However, if engaged in a large number of bottom die forming, perhaps should consider a 150 - ton machine tool. If the thickest material to be bent in production is 6mm and the length is 2500mm, when the low carbon steel is bent freely, it is necessary to consider the need for a bending machine of more than 100 tons.

If some bending is done by bending the bottom die (correcting the bending), then a larger tonnage bending machine is required.

If most of the bending workpiece is 1250mm or less, then consider the bending machine tonnage is almost halved, thus greatly reducing the acquisition cost. Therefore, the length of the processed parts is very important to determine the specifications of the new models.

Scratching

Bending machine in bending processing, especially bending the length of the size of the workpiece, will occur bending the longer the bending deformation will be larger. Under the same load, the torsion of the workbench and slider of the 2500mm model is 4 times that of the 1250mm model. This means that shorter machines require fewer gasket adjustments to produce qualified parts, which reduces gasket adjustments and lead time. But now the CNC hydraulic bending machine in the production design have increased the hydraulic deflection compensation function, reduce the production operator to adjust the equipment, and improve the bending accuracy and production efficiency. The hydraulic deflection compensation function is controlled by the numerical control system. The hydraulic oil enters the compensation cylinder through the magnetic levyvalve and carries on the top of the working table. At the same time, the deflection compensation force increases with the increase of the bending force, which plays the role of deflection compensation. The texture of the processed material is also a key factor. Compared with mild steel, stainless steel usually requires a load increase of about 50%, while most materials are soft aluminum side with a reduction of about 50%. The relevant standard bending pressure parameters can be obtained from the bending machine manufacturer. The table shows the bending force required for each 1000mm of different thickness and 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 the opening size of the v-slot. In the free bending process, the size of the v-slot opening should be 8 times the thickness of the metal material. For example, when bending 1.5mm mild steel with a 12mm v-slot opening size, the bending radius of the part is about R = 1.9mm. If the bending radius is close to the thickness of the material or less than the thickness of the plate, the bottom die shall be formed. However, forming with a bottom die requires about four times more pressure than free bending.

In the case of free bending, note the gap between the upper and lower die at the bottom of the stroke and the excessive bending of the material at about 90° which is sufficient to compensate for springback. In general, the rebound Angle of the free bending die generated by the new bending machine is less than 2°, and the bending radius is equal to 0.156 times of the opening distance of the lower die. Therefore, generally free up and down mold bending processing, mold Angle is generally 86~90°. At the bottom of the stroke, there should be a gap slightly larger than the material thickness between the upper and lower die. The forming Angle is improved because the tonnage of bending with the bottom die is larger (about 4 times that of free bending), reducing the stress in the bending radius that usually causes springback.

Embossing bending is the same as bending with the bottom die, but the front end of the top die is processed into the desired bending radius, and the bottom of the top die gap is less than the material thickness. By applying enough pressure (about 10 times as much as free bending) to force the upper die front to contact the material, springback is largely avoided. In order to select the lowest ton size, it is best to plan for a bending radius greater than the material thickness and to use the free bending method whenever possible. When the bending radius is large, the quality of the parts and their future use are usually not affected.

Accuracy

Bending accuracy is a factor that needs careful consideration. It is this factor that determines whether you need to consider a CNC bending machine or an ordinary NC bending machine. If the bending accuracy is within 0.5° and cannot be changed, you must focus on the CNC bending machine. CNC bending machine sliding block repetition accuracy is generally guaranteed in ±0.01mm, forming the precise Angle must be used such precision and good mold. The repeat precision of the sliding block of NC bending machine is ±0.5mm, and it will generally produce ±2 ~ 3° under the condition of using a suitable mold. The deviation.

In addition, the CNC bending machine is equipped with a rapid modular control system and clamping devices, when you need to bend a lot of small batch parts, this is an indisputable reason to consider.

The mold

The bending die also directly affects the bending accuracy, so it is necessary to check the wear condition of the die by measuring the length between the front end of the upper die and the shoulder of the lower die.

For conventional moulds, the deviation should be about 0.01mm per 10mm, and the total length deviation should not be more than ±0.15mm. As for the precision grinding mould, the precision should be ±0.005mm per 100mm, and the total precision should not be greater than ±0.05mm. It is better to use the fine grinding mould for NC bending machine and the conventional mould for NC bending machine.

Conclusion:

As the user of the equipment or the manufacturer in the purchase of bending machine, the most important is to purchase an economical and practical bending machine, of course, this is to consider a lot of factors. At the same time according to their own actual situation, the above points are just a brief overview of some one-sided problems.

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