The first important thing to consider is the parts you want to produce, the point is to buy a machine to complete the task and the shortest table, the smallest number of machines. Grade and maximum processing thickness and length. If most of the work is a thickness of 16 gauge, the maximum length of 10 feet of low carbon steel, then the free bending force is not greater than 50 tons. However, if you are engaged in a large number of bottom die forming, perhaps should consider a 150 tonnage of the machine. Well, assume that the thickest material is 1/4 inch, 10 feet free bend requires 165 tons, and the bottom of the mold bending (correction bending) at least 600 tons. If most of the workpieces are 5 feet or less, the tonnage is almost halved, thus greatly reducing the purchase cost. The length of the part is important to determine the specifications of the new machine.
Tensile Under the same load, the 10-foot machine bench and the slider's flexion are 4 times the 5-foot machine. This means that shorter machines require less gasket adjustment to produce qualified parts. Reducing the gasket adjustment also shortens the preparation time. Material grades are also a key factor. Compared with low-carbon steel, the required load of stainless steel is usually increased by about 50%, while most brands of soft aluminum reduced by about 50%. You can get the tonnage table of the machine at any time from the bending machine manufacturer, which shows the estimated tonnage per foot length at different thicknesses and different materials. When the bending radius of the part is free to bend, the bending radius is 0.156 times of the opening distance of the die. In the free bending process, the die opening should be 8 times the thickness of the metal material. For example, when using a 1/2 inch opening to form a 16 gauge low carbon steel, the part has a bending radius of about 0.078 inches. Bending radius is almost as small as the thickness of the material, to be a bottom concave mold forming. However, the pressure required for the bottom die is about four times greater than the free bend. If the bending radius is less than the thickness of the material, use a punch with a front end radius smaller than the thickness of the material and turn to the embossing method. In this way, it takes 10 times the pressure of free bending.
In the case of free bending, the punch and die are machined at 85 ° or less (85 °). With this set of molds, pay attention to the punch and die at the bottom of the gap in the stroke, and enough to compensate for the rebound and make the material to maintain about 90 ° excessive bending.
In general, the free bending mode produces a rebound angle of less than 2 ° on the new bending machine, and the bending radius is equal to 0.156 times the opening distance of the die.
For the bottom concave mold bending, mold angle is generally 86 ~ 90 °. At the bottom of the stroke, there should be a gap between the male and female molds slightly larger than the thickness of the material. The forming angle is improved because the tonnage of the bottom die is larger (about four times the free bend), reducing the stress normally caused by the rebound radius.
The embossed bend is the same as that of the bottom die, except that the front end of the punch is machined to the desired bending radius and the punch and die clearance at the bottom of the stroke is less than the material thickness. As a result of the application of sufficient pressure (about 10 times the free bending) forced the punch front contact material, basically avoid the rebound.
In order to select the lowest tonnage specification, it is best to plan for a bend radius greater than the thickness of the material and to use the free bend method as much as possible. When the bending radius is large, it often does not affect the quality of the parts and its future use. Accuracy The bending accuracy requirement is a factor that requires careful consideration, and 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 can not be changed, you must focus on the CNC machine.
CNC bending machine slider repeat accuracy is ± 0.0004 inches, forming a precise angle to be used with such precision and good mold. Manual bending machine slider repeat accuracy of ± 0.002 inches, and in the use of appropriate mold conditions generally produce ± 2 ~ 3 ° deviation. In addition, the NC Bending Machine is ready for quick loading, which is an unquestionable reason when you need to bend many small parts. Molds Even if you have full molds, do not think these molds are suitable for newly purchased machines. It is necessary to check the wear of each mold by measuring the length between the front end of the punch and the shoulder and the length between the die shoulder.
For conventional molds, the deviation per foot should be around ± 0.001 inches and the total length deviation is not greater than ± 0.005 inches. As for the grinding mold, the accuracy of each foot should be ± 0.0004 inches, the total accuracy of not more than ± 0.002 inches is best to fine grinding mold for CNC bending machines, conventional mold for manual bending machine. The side of the bend is assumed to be bent 90 ° along a 5 x 10 foot 10 low carbon steel plate, and the bending machine is about to add an additional 7.5 tons of pressure to the top of the steel plate, and the operator must drop for the 280 pound Be prepared. The manufacture of the part may require several strong workers and even a crane. Bending machine operators often need to bend long side parts, but do not know how hard they work. There is now a feeder device suitable for the work of this workshop, this device can be based on the needs of new and old machines to be improved. With this device, forming a long side part requires only one person to operate.
