Today, I will teach you how to choose the bending machine according to the characteristics of the six bending machines

1、 Workpieces: the first important thing to consider is the parts you want to produce. The key point is to buy a machine that can complete the processing task and has the shortest worktable and the smallest tonnage. Carefully consider material grade and maximum machining thickness and length. If most of the work is mild steel with a thickness of 16 gauge and a maximum length of 10 feet, the free bending force does not have to be greater than 50 tons. However, if you are engaged in a large number of bottomed die forming, maybe you should consider a 160 ton machine tool.

Well, suppose the thickest material is 1 / 4 inch, 200 tons for 10 foot free bending and 600 tons for bottom die bending (corrected bending). If most of the work pieces are 5 feet or shorter, the tonnage will be almost halved, thus greatly reducing the purchase cost. The length of parts is very important to determine the specifications of a new machine.

2、 Deflection: under the same load, the deflection of the table and slide of the 10 foot machine is four times that of the 5 foot machine. That is to say, shorter machines require less gasket adjustment to produce qualified parts. Reduce the gasket adjustment and shorten the 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 that of most brands of soft aluminum is reduced by about 50%. You can get the tonnage table of the machine from the bending machine manufacturer at any time. The table shows the tonnage estimation required for each foot length under different thickness and materials.

3、 Bending radius of parts: when using free bending, the bending radius is 0.156 times of the die opening distance. In the process of free bending, the opening distance of die should be 8 times of the thickness of metal material. For example, when forming 16gauge mild steel with 1 / 2 inch opening distance, the bending radius of the part is about 0.078 inch. If the bending radius is almost as small as the material thickness, the bottom die forming must be carried out. However, the forming pressure of the die with bottom is about 4 times higher than that of free bending.

If the bending radius is less than the material thickness, the punch with the front fillet radius less than the material thickness should be used, and the embossing bending method should be used. In this way, 10 times the free bending pressure is required. As far as free bending is concerned, punch and die should be machined at 85 ° or less (small point is better). When using this group of dies, attention should be paid to the gap between the punch and the die at the end of the stroke, and the excessive bending which is enough to compensate the springback and keep the material about 90 degrees. Generally, the springback angle of the free bending die on the new bending machine is less than 2 ° and the bending radius is equal to 0.156 times of the opening distance of the die. For the bottom die bending, the die angle is generally 86 ~ 90 degrees. At the bottom of the stroke, there should be a gap between the male and female dies which is slightly larger than the material thickness. The forming angle is improved because the bending tonnage of the die with bottom is larger (about 4 times of that of free bending), which reduces the springback stress within the bending radius.

The stamping bending is the same as the bending of the die with bottom, 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 less than the material thickness. Because enough pressure (about 10 times of free bending) is applied to force the front end of the punch to contact the material, the 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, the quality of the finished part and its future use are often not affected.

4、 Degree: the requirement of 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 a manual bending machine. If the bending accuracy requires ± 1 ° and cannot be changed, you must focus on CNC machine.

The repeat precision of CNC bending machine slider is ± 0.0004 inch. The precision and good die must be used for forming accurate angle. The repeat accuracy of the slider of the manual bending machine is ± 0.002 inch, and the deviation of ± 2 ~ 3 ° is usually produced when the suitable die is used. In addition, CNC bending machine is ready for rapid die assembly, which is an unquestionable reason when you need to bend many small batches of parts.

5、 Molds: even if you have a full shelf of molds, don't think these molds are suitable for new machines. Each die must be checked for wear 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 dies, the deviation per foot should be about ± 0.001 inch, and the total length deviation should not be more than ± 0.005 inch. As for the precision grinding die, the precision per foot should be ± 0.0004 inch, and the total precision should not be greater than ± 0.002 inch. It is better to use fine grinding die for CNC bending machine and conventional die for manual bending machine.

6、 Side length of bending part: assuming that the bending angle is 90 ° 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 the 280 pound straight edge falling. It may take several strong men to make the part