If the choice of bending machine is improper, the production cost will rise, and the bending machine can not expect to recover the cost. Therefore, when making a decision, there are several factors that must be weighed.

workpiece

The first thing to consider is the parts you want to make. The focus is to buy a machine that can complete the processing task, has the shortest worktable and the smallest tonnage.

Carefully consider material grade and maximum machining thickness and length. If most of the work pieces are made of mild steel, the thickness is No. 16, and the maximum length is 10 feet (3.048 meters), the free bending force does not need to be greater than 50 tons. But if you are engaged in a large number of bottom mold forming, you should probably consider 160 tons of machine tools.

Assuming the thickest material is 1 / 4 inch, 200 tons is required for 10 foot free bending, and at least 600 tons is required for bottom die bending (correction bending). If most of the work pieces are 5 feet or shorter, the tonnage will be almost halved, thus greatly reducing the procurement cost. The length of the part is very important to determine the specification of the new machine.

deviation

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. In other words, shorter machines require less gasket adjustment to produce qualified parts. Reducing gasket adjustment shortens preparation time.

Material grade is also a key factor. Compared with mild steel, the load required for stainless steel is usually increased by about 50%, while the load required for most grades of soft aluminum is reduced by about 50%. You can always get the tonnage table of the bending machine from the manufacturer, which shows the estimated tonnage per foot of length under different thickness and material.

Bending radius

When free bending is used, the bending radius is 0.156 times of the opening distance. In the free bending process, the opening distance of the die should be 8 times of the thickness of the metal material. For example, when forming 16 mild steel with an opening distance of 1 / 2 inch (0.0127 m), 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 mold must be formed. However, the pressure required to form a die with a bottom is about four times that required 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 shall be used, and the stamping bending method shall be adopted. In this way, 10 times the free bending pressure is required.

For free bending, the punch and die are machined to 85 ° or less (the smaller the better). When using this set of die, attention should be paid to the clearance between the punch at the bottom of the stroke and the die, as well as the excessive bending sufficient to compensate the springback and keep the material at about 90 degrees.

The springback angle of the free bending die on the new bending machine is generally ≤ 2 ° and the bending radius is equal to 0.156 times of the opening distance of the die.

The die angle is generally 86 ° to 90 ° when the bottom die is bent. At the bottom of the stroke, there should be a gap between the punch and the die slightly larger than the material thickness. The forming angle is improved, because the tonnage of the bottom bending die is larger (about 4 times that of the free bending), which reduces the springback stress in the bending radius.

The indentation bending is the same as that of the bottom die, except that the front end of the punch is processed to the required bending radius, and the gap between the punch and the bottom die at the bottom of the stroke is less than the material thickness. Since enough pressure (about 10 times of free bending) is applied to force the front end of the punch to contact the material, rebound is basically avoided.

In order to select the minimum tonnage specification, it is better to plan the bending radius greater than the material thickness, and try to use the free bending method. When the bending radius is large, it often does not affect the quality of finished parts and future use.

Arc

The requirement of bending accuracy is a factor to be considered carefully. It is this factor that determines whether CNC bending machine or manual bending machine should be considered. If the bending accuracy requires 1 and can not be changed, it must focus on CNC machine tools.