# CNC bending machine how to choose, what is the knowledge?

CNC bending machine selection knowledge:

1, artifacts,The first important thing to consider is the parts you want to produce. The main point is to buy a machine that can complete the processing task with the shortest working table and the smallest tonnage.Carefully consider the material grade and maximum machining thickness and length.If the majority of the work is on low-carbon steel with a thickness of 16gauge and a maximum length of 10 feet, the free bending force need not be greater than 50 tons.However, if you do a lot of bottom die forming, you might want to consider a 150 ton machine tool.Ok, suppose the thickest material is 1/4 inch, 10 feet free bending requires 165 tons, and bottom die bending (corrected bending) requires at least 600 tons.If most of the workpieces are 5 feet or less, the tonnage is roughly halved, greatly reducing the cost of acquisition.The length of the parts is important in sizing up the new machine.

2, scratchingUnder the same load, the 10-foot worktable and slider are four times as flexible as the 5-foot machine.This means that shorter machines can produce qualified parts with fewer gasket adjustments.Reduced gasket adjustment reduces lead time.Material grade is also a key factor.Compared with mild steel, stainless steel usually requires a load increase of about 50%, and most grades of soft aluminum reduced by about 50%.You can always get a tonnage table from the bending machine manufacturer showing the estimated tonnage required per foot of length for different thicknesses and materials.

3. Bending radius of partsWhen using free bending, the bending radius is 0.156 times of the die opening distance.In free bending, die opening distance should be 8 times the thickness of the metal material.For example, using 1/2 inch gap gauge for 16gauge low-carbon steel, the bending radius of the part is about 0.078 inches.If the bending radius is almost small enough to the thickness of the material, the bottom die forming should be carried out.However, bottom die forming requires about four times more pressure than free bending.If the bending radius is less than the thickness of the material, the front rounded corner radius is less than the material thickness of the punch, and for bending method.Thus, 10 times the free bending pressure is required.In terms of free bending, convex die and concave die according to the 85 ° or less than 85 ° processing (smaller).Using this set of mold, punch and die in the gap at the bottom of the stroke, and compensate the springback and keep material around 90 ° of flexion.Usually, free bending die on a new bending machine of springback Angle 2 ° or less, bending radius equal to the die opening distance of 0.156 times.For a bottom bending die, die Angle generally is 86 ~ 90 °.At the bottom of the stroke, there should be a gap between the convex and concave dies slightly larger than the thickness of the material.The forming Angle is improved because of the large tonnage of the bottom die bending (about 4 times of the free bending), which reduces the stress that usually causes the springback within the bending radius.Embossing bending and bottom die bending is the same, but the punch front end processing into the required bending radius, and the punch at the bottom of the stroke gap is less than the thickness of the material.By applying enough pressure (about 10 times the free bending) to force the front end of the punch into contact with the material, the springback is essentially avoided.In order to select the lowest tonnage specification, it is best to plan for a bending radius greater than the material thickness and to use the free bending method as far as possible.When the bending radius is large, the quality of the component and its future use are often unaffected.

4, precision,Bending precision requirements are a serious consideration, which determines whether you need to consider a CNC bending machine or a manual bending machine.If bending accuracy + / - 1 ° and cannot be changed, you must focus on CNC machine.CNC bending machine slider repeat accuracy of 0.0004 inches, forming accurate Angle must be used in such precision and good mold.Manual bending machine slider repeat accuracy is + / - 0.002 inches, and under the condition of using appropriate mould generally produce deviation of plus or minus 2 ~ 3 °.In addition, CNC bending machines are well prepared for rapid assembly, which is an unquestionable consideration when you need to bend many small batches of parts.

5, mouldEven if you have a shelf full of molds, do not assume that these molds are suitable for newly purchased machines.Wear of each die must be checked by measuring the length from the front end of the punch to the shoulder and from the shoulder of the die.For conventional moulds, the deviation per foot shall be approximately 0.001 in. And the total length deviation shall not be greater than 0.005 in.For precision molds, the accuracy per foot shall be 0.0004 inches and the total accuracy shall not be greater than 0.002 inches.It is better to use fine grinding mould for CNC bending machine, and conventional mould for manual bending machine.6. Side length of bending partsAssumptions along a 5 x 10 feet 10 - the gauge of low carbon steel plate bending 90 °, bending machine must be about 7.5 tons of pressure extra steel roof rise, while the operator must be geared up for the 280 - pound straight down.It may take several strong workers or even a crane to make the part.Bending machine operators often need to bend long side parts without realizing how hard their work is.There is now a stock holding device suitable for the shop where such work is to be done, which can be adapted to the needs of old and new machines.With this device, forming long - side parts can only be operated by one person.

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