Numerical control punch a few valuable use tips

Views: 4     Author: DURMAPRESS     Publish Time: 2021-12-16      Origin: DURMAPRESS


Numerical control punch a few valuable use tips

CNC punch operation is a technical type of work, generally before the post will accept professional operation training, but after training workers can only operate CNC punch, really want to play Numerical control punch, you need to have a lot of experience, need to continue to find and summarize in the long-term work. Here is a brief introduction to a few:

First, CNC punch needs to ensure the appropriate mold clearance

The die clearance is the sum of the clearance on both sides when the punch enters the lower die. It is related to plate thickness, material and stamping process,

Choose the appropriate mold clearance, can ensure good punching quality, reduce burr and collapse, keep the sheet smooth, effectively prevent material, prolong the life of the mold.


By checking the stamping waste, you can determine whether the mold clearance is appropriate. If the clearance is too large, the scrap will have rough undulating fracture surfaces and smaller bright surfaces. The larger the gap is, the larger the Angle between the fracture surface and the bright surface will be. When punching, crimping and fracture will be formed, and even a thin edge protrusion will appear. On the contrary, if the clearance is too small, the waste will appear small Angle fracture surface and large bright surface.

When grooving, stepping, shearing and other local stamping, the lateral force will make the punch deflect and cause unilateral clearance is too small, and sometimes the edge offset is too large to scratch the lower die, causing rapid wear of the upper and lower die.

When the die is pressed with the optimum clearance, the fracture surface and the bright surface of the scrap are at the same Angle and coincide with each other, so that the punching force is minimal and the burr of the punch is minimal.


Two, timely grinding can effectively prolong the service life of the mold

If the workpiece appears too large burr or abnormal noise when stamping, it may be the die passivation. Check the punch and the lower die, when its edge wear produces a radius of about 0.10mm arc, it is necessary to grind.

Practice shows that regular grinding of small grinding rather than waiting for the necessary grinding, not only can maintain good workpiece quality, reduce the blanking force, but also can prolong the life of the die more than one time.

In addition to knowing when the mold is grinding, it is especially important to master the correct grinding method. The mould grinding rules are as follows: 1) Sintered alumina grinding wheel, hardness D~J, grinding grain size 46~60, it is best to choose the grinding wheel suitable for high-speed steel grinding. 2) When grinding, the punch is held vertically in the V-groove or fixture of the magnetic chuck of the flat surface grinder. The grinding amount is 0.03~0.05mm each time, and the grinding is repeated until the punch is sharp. The maximum grinding amount is generally 0.1~0.3mm.

3) When the grinding force is large or the mold is close to the grinding wheel, adding coolant can prevent the mold from overheating and cracking or annealing. High-quality multi-purpose coolant should be selected according to the manufacturer's requirements.

4) Grinding wheel downward feed 0.03-0.08mm, lateral feed 0.13-0.25mm, lateral feed rate 2.5-3.8m /min. 5) After grinding, polish the edge with a stone to remove burrs and grind out a rounded corner with a radius of 0.03~0.05mm, which can prevent the edge from cracking.

6) The punch is demagnetized and sprayed with lubricating oil to prevent rust.


Three, eliminate and reduce the method of adhesive

Due to the pressure and heat of CNC punch press, the fine particles of sheet metal will be bonded to the punch surface, resulting in poor punching quality. The removal of adhesive material can be polished with a fine whetstone in the same direction as the punch movement, so that further adhesive generation will be avoided after polishing. Do not use coarse gauze and other grinding, so as to avoid the punch surface more rough, more likely to appear sticky. Proper die clearance, good stamping process, and necessary sheet lubrication will reduce the production of adhesive material. To prevent overheating, lubrication is generally used, which will reduce friction. In case of failure of lubrication or waste rebound, the following methods can be adopted:

Alternating the use of multiple punches of the same size in turn allows for a longer cooling time before reuse. The overheated mould is stopped for use. Through programming control mold change, interrupt its long time repetitive work, or reduce its stamping frequency.

Four, the measures to prevent sheet deformation when punching very porous

If a sheet is punched very porous, it will not remain flat due to the accumulation of punching stresses. Every time the hole is punched, the material around the hole will deform downward, resulting in tensile stress on the upper surface of the sheet, and compressive stress on the lower surface. For a small number of punching holes, the effect is not obvious, but as the number of punching holes increases, tensile and compressive stresses accumulate somewhere until the material deforms.

One way to eliminate such deformation is to blanch every other hole and then return to blanch the remaining holes. Although this will also produce stress, but it alleviates the stress accumulation in the same direction when the order of stamping, will also make the stress of the two groups of holes offset each other, so as to prevent the deformation of the sheet.


Five, as far as possible to avoid cutting narrow strip

When the CNC punch die is used for punching width is less than the thickness of the sheet, because of the lateral force and the punch bending deformation, the gap on one side is too small or wear aggravated, serious will scratch the next die, so that the upper and lower die at the same time damage.

It is recommended not to step blanking the narrow sheet material whose width is less than 2.5 times the sheet thickness. When too narrow a strip is cut, the sheet tends to bend into the opening of the lower die rather than being completely cut off, or even wedge into the side of the die. If the above situation cannot be avoided, it is recommended to use a fully guided die with a return plate supporting the punch.

The above is a few CNC punch experience sharing, will be helpful to the novice.

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