Cnc Type Hydraulic Press For Sheet Metal Bending , Metal Plate Bending Machine

If the wrong choice is made when choosing a bending machine, the production cost will rise, and the bending machine cannot be expected to recover the cost. Therefore, several factors need to be weighed in decision-making.
Artifact
The first important thing to consider is the part you want to produce. The main point is to buy a machine that can complete the processing task with the shortest worktable and the smallest tonnage.
Carefully consider the material grade and maximum machining thickness and length. If most of the work is a low gauge steel with a thickness of 16 gauge and a maximum length of 10 feet (3.048 meters), the free bending force need not be greater than 50 tons. However, if you are engaged in a large number of bottom die forming, you may want to consider a 160-ton machine.
Assuming that the thickest material is 1/4 inch, a free bending of 10 feet requires 200 tons, and a bottomed die bending (corrected bending) requires at least 600 tons. If most parts are 5 feet or shorter, the tonnage is almost halved, which greatly reduces the purchase cost. Part length is important to determine the specifications of a new machine.
Deflection
Under the same load, the distortion of the 10-foot machine table and slider is 4 times that of the 5-foot machine. This means that shorter machines require fewer shim adjustments to produce qualified parts. Reducing shim adjustments reduces turnaround time.
Material grade is also a key factor. Compared with low carbon steel, the load required for stainless steel is usually increased by about 50%, while most grades of soft aluminum are reduced by about 50%. You can always get the machine's tonnage table from the bending machine manufacturer. This table shows the estimated tonnage per foot length for different thicknesses and materials.
Bending radius
When using free bending, the bending radius is 0.156 times the opening distance of the die. In the free bending process, the die opening distance should be 8 times the thickness of the metal material. For example, when using a 1 / 2-inch (0.0127-meter) opening to form a 16 gauge mild steel, the bending radius of the part is about 0.078 inches. If the bending radius is almost as small as the thickness of the material, a bottomed die must be formed. However, the pressure required for forming a bottomed die is about four times greater than that of free bending.
If the bending radius is less than the thickness of the material, a punch with a radius at the front end that is smaller than the thickness of the material must be used, and resort to the embossing bending method. This requires 10 times the pressure of free bending.
As far as free bending is concerned, the male and female dies are processed at 85 ° or less (smaller is better). When using this set of molds, pay attention to the gap between the male and female molds at the bottom of the stroke, and excessive bending that is sufficient to compensate for springback and keep the material around 90 °.
Generally, the springback angle of the free bending die on the new bending machine is ≤ 2 °, and the bending radius is equal to 0.156 times the opening distance of the die. For the bending of the bottomed mold, the 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 male and female dies. The forming angle is improved because the tonnage of the bottomed die is larger (about 4 times of free bending), which reduces the stress that usually causes springback in the range of the bending radius.
The embossed bending is the same as the bottomed die bending, except that the front end of the punch is processed to the required bending radius, and the gap between the punch and the bottom of the stroke is smaller than the material thickness. Due to the application of sufficient pressure (about 10 times of free bending) to force the front end of the punch to contact the material, rebound is basically avoided.
In order to choose the lowest tonnage specification, it is best to plan for a bending radius larger than the thickness of the material, and use the free bending method as much as possible. When the bending radius is large, it often does not affect the quality of the piece and its future use.
Curvature
The bending accuracy requirement is a factor that needs to be carefully considered. It is this factor that determines whether a CNC bending machine or a manual bending machine needs to be considered. If the bending accuracy is required to be ± 1 ° and cannot be changed, we must focus on the CNC machine.
The repeatability of the slider of the CNC bending machine is ± 0.0004 inches. The precise angle of forming must adopt such accuracy and a good mold. The repeatability of the slider of the manually controlled bending machine is ± 0.002 inches, and the deviation of ± 2 ~ 3 ° is generally generated under the condition of using a suitable mold. In addition, CNC press brakes are ready for rapid mold set-up, which is an unquestionable reason to consider when many small batches need to be bent.
Mould
Even if there are molds full of shelves, don't think that these molds are suitable for new machines. The wear of each mold 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 die.
For conventional molds, the deviation per foot should be around ± 0.001 inches, and the total length deviation should not be greater than ± 0.005 inches. As for precision grinding molds, the accuracy per foot should be ± 0.0004 inches, and the total accuracy must not be greater than ± 0.002 inches. It is best to use precision grinding molds for CNC bending machines, and conventional molds for manual bending machines.
Bend side length
Assuming a 90 ° bend along a 5 × 10-foot 10-gauge low carbon steel plate, the bending machine must apply an additional 7.5 tons of pressure to lift the steel plate, and the operator must be prepared for a straight edge of 280 pounds to fall . Manufacturing the part may require several powerful workers or even a crane. Bender operators often need to bend long-edge parts without realizing how strenuous their work is