What Should Be Know When Purchasing Pressbrake
When purchasing a press brake, improper selection can drive up production costs and make it difficult for the press brake to pay for itself. Therefore, it is important to choose the right product. The press brake produced by China AHYW Yawei Machine Factory is mainly used for production, and the quality is excellent with after-sales assurance. There are several factors to consider when purchasing a press brake:
01, Sheet Metal Bending Workpiece.
The first important factor to consider is the parts you are going to produce. The goal is to buy a machine with the shortest working table and the lowest tonnage that can complete the processing task. Carefully consider the material grade and the maximum processing thickness and length. If most of the work is 16-gauge low-carbon steel with a maximum length of 10 feet (3.048 meters), the free bending force should not be greater than 50 tons. However, if you do a lot of bottoming die forming, you should consider a 160-ton machine. Assuming the thickest material is 1/4 inch, 10 feet free bending requires 200 tons, while bottoming die bending (correction bending) requires at least 600 tons. If most of the parts are 5 feet or shorter, the tonnage is almost halved, thus greatly reducing the purchase cost. The length of the part is very important in determining the specification of the new machine.
02, Profile's Bending Deflection Value
Under the same bending load, the deflection of the worktable and slide of the 10-feet machine is four times that of the 5 ft machine. That is to say, shorter machines need less gasket adjustment to produce qualified parts. The reduction of shim adjustment shortens the preparation time.
Material grade is also a key factor. Compared with low carbon steel, the load required by stainless steel is generally increased by about 50%, while that of most brands of soft aluminum is reduced by about 50%. You can obtain the tonnage table of the machine from the bending machine manufacturer at any time, which shows the estimated tonnage required per foot of length under different thicknesses and materials.
03,Metal profile's bending radius
When free bending is adopted, the bending radius is 0.156 times of the opening distance of the female die. In the process of free bending, the opening distance of the female die should be 8 times the thickness of the metal material. For example, when the opening distance of 1/2 inch (0.0127 m) is used to form 16 gauge mild steel, the bending radius of the part is about 0.078 inch. If the bending radius is almost as small as the material thickness,
It must be formed by a concave die with a bottom. However, the pressure required for forming a bottomed die is about 4 times greater than that for free bending.
If the bending radius is less than the material thickness, the punch with the front fillet radius less than the material thickness must be used, and the stamping bending method must be used. In this way, it requires 10 times the pressure of free bending.
In terms of free bending, the punch and die shall be processed at 85 ° or less (small points are better). When using this set of dies, pay attention to the gap between the punch and the die at the bottom of the stroke and the excessive bending that is sufficient to compensate for the rebound and keep the material at about 90 °.
Generally, the springback angle produced 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 female die.
For bending of concave die with bottom, the die angle is generally 86~90 °. At the bottom of the stroke, there should be a gap between the male and female dies that is slightly larger than the material thickness. The forming angle is improved because the bending tonnage of the bottomed die is large (about 4 times of the free bending), which reduces the stress that usually causes springback within the bending radius.
The stamping bending is the same as the bending of the concave die with a bottom, except that the front end of the punch is processed to the required bending radius, and the gap between the concave and convex die at the bottom of the stroke is less than the material thickness. Since sufficient pressure (about 10 times of free bending) is applied to force the front end of the punch to contact the material, springback is basically avoided.
In order to select the lowest tonnage specification, it is better to plan for the bending radius greater than the material thickness, and use the free bending method as far as possible. When the bending radius is large, it often does not affect the quality of the finished part and its future use.
04, Sheet Profile's Bending Precision
The bending accuracy requirement is a factor that needs to be carefully considered. It is precisely this factor that determines whether to consider a CNC bending machine or a manual bending machine. If the bending accuracy is required to be ± 1 ° and cannot be changed, it is necessary to focus on the CNC machine.
The repetition accuracy of the slide block of the CNC bending machine is ± 0.0004 inch. Such accuracy and good mold must be used for the accurate forming angle. The repetition accuracy of the slide block of the manual bending machine is ± 0.002 inch, and the deviation of ± 2~3 ° will generally occur under the condition of using the appropriate mold. In addition, CNC bending machine is ready for rapid die assembly. When it is necessary to bend many small batches of parts, this is an unquestionable reason to consider.
05, CNC Press Brake Tooling System
Even if there are press brake tools full of shelves, do not think these bending tooling are suitable for newly purchased pressbrakes. The wear of each die must be checked by measuring the length from the front end of the punch to the shoulder and the length between the shoulder of the female die.
For conventional pressbrake tools, the deviation per foot should be about ± 0.001 inch, and the total length deviation should not be more than ± 0.005 inch. For precision grinding molds, the accuracy per foot should be ± 0.0004 inches, and the total accuracy should not be greater than ± 0.002 inches. It is better to use the precision grinding mold for CNC Pressbrake bending machine, and the conventional tools for NC Pressbrake bending machine.
06, Flange For Sheet Metal Bending Profiles
Assume that along a 5 × The 10-foot 10-gauge low-carbon steel plate is bent for 90 °. The bending machine must apply an additional 7.5 tons of pressure to lift the steel plate, and the operator must be prepared for the 280-pound straight edge drop. Manufacturing this part may require several strong workers or even a crane. Bending machine operators often need to bend long-sided parts, but they are not aware of how hard their work is.
