How to avoid creases during the bending process of CNC bending machine?

Stainless steel is particularly prone to scratches during the bending process. In the process of using the anti-indentation protective film of the CNC bending machine, the production of scratches is effectively avoided. When using the anti-indentation protective film of the bending machine, pay attention to the cleanliness of the environment. Avoid iron filings attached to the surface, which can greatly increase the service life of the bending film.

How to avoid creases in the bending process? How do customers choose a CNC bending machine?

CNC bending machine

Once the selection of the bending machine is improper, the production cost will rise, and the bending machine cannot be expected to recover the cost. Therefore, there are several factors that must be weighed in the decision-making process. Workpiece, the first important thing to consider is the part you want to produce. The point is to buy a machine that can complete the processing task with a short workbench and a small tonnage. Carefully consider the material grade and the large processing thickness and length. If most of the work is low carbon steel with a thickness of 16 and a large length of 10 feet (3.048 meters), then the free bending force does not need to be greater than 50 tons.

However, if you are engaged in a large number of bottomed die forming, perhaps you should consider a 160-ton machine tool. Assuming that the thicker material is 1/4 inch, a 10-foot free bending requires 200 tons, and a bottomed die bending (correction bending) requires at least 600 tons. If most parts are 5 feet or shorter, the tonnage is almost halved, which greatly reduces the cost of purchase. The length of the part is very important for determining the specifications of the new machine. Deflection, under the same load, the deflection of the worktable and sliding block of a 10-foot machine is 4 times that of a 5-foot machine. This means that shorter machines require fewer shim adjustments to produce qualified parts. Reduced shim adjustment and shortened preparation time. Material grade is also a key factor. Compared with low-carbon steel, the load required by stainless steel is usually increased by about 50%, while most grades of soft aluminum are reduced by about 50%.

The tonnage table of the machine can be obtained from the bending machine manufacturer at any time. The table shows the estimated tonnage required per foot length under different thicknesses and different materials. The bending radius, when free bending is used, the bending radius is 0.156 times the opening distance of the die. During the free bending process, the opening distance of the die should be 8 times the thickness of the metal material. For example, when using 1/2 inch (0.0127 m) opening distance to form 16 mild steel, the bending radius of the part is about 0.078 inches. If the bending radius is almost as small as the material thickness, a bottomed die must be formed.

However, the pressure required for bottomed die forming is about 4 times greater than that of free bending. If the bending radius is less than the thickness of the material, a punch with a front-end fillet radius smaller than the thickness of the material must be used, and the imprint bending method must be used. In this way, 10 times the pressure of free bending is required. As far as free bending is concerned, punch and die are processed at 85 or less (smaller is better). When using this set of molds, pay attention to the gap between the male mold and the female mold at the bottom of the stroke, and the excessive bending that is sufficient to compensate for the springback and keep the material around 90%. Generally, the springback angle of the free bending die on the new bending machine is less than or equal to 2, and the bending radius is equal to 0.156 times the opening distance of the die. For the bending of bottomed concave molds, the mold angle is generally 86 ~ 90.

At the bottom of the stroke, there should be a gap slightly larger than the thickness of the material between the male and female molds. The forming angle is improved because the bottomed die has a larger bending tonnage (about 4 times that of free bending), which reduces the stress that usually causes springback in the bending radius. The imprint bending is the same as the bending of the bottomed die, except that the front end of the punch is processed to the required bending radius, and the gap between the punch and the die at the bottom of the stroke is smaller than the material thickness. Since enough pressure (approximately 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 choose a very low tonnage specification, it is good 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 finished part and its future use. Curvature and bending accuracy requirements are 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 1 and cannot be changed, the CNC machine must be focused. The repeatability of the slider of the CNC bending machine is 0.0004 inches, and the precise angle of forming must use such precision and a good mold.

The repeatability of the slide block of the manual bending machine is 0.002 inches, and the deviation of 2~3 will generally occur under the condition of using a suitable mold. In addition, the CNC bending machine is ready for rapid mold assembly. When many small batches of parts need to be bent, this is an indisputable reason for consideration. Molds, even if there are shelves full of molds, do not think that these molds are suitable for the newly purchased machine. 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 female mold.

For conventional molds, the deviation per foot should be about 0.001 inches, and the total length deviation should not be greater than 0.005 inches. As for the precision grinding mold, the precision per foot should be 0.0004 inches, and the total precision should not be greater than 0.002 inches. It is good to use fine grinding molds for CNC bending machines, and conventional molds for manual bending machines. The side length of the bent part is assumed to be bent 90 along a 5×10-foot 10 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 drop the 280-pound straight edge. Get ready. Manufacturing this part may require several strong workers or even a crane. Operators of bending machines often need to bend long-side parts without realizing how hard their work is.