Stamping Die Data Summary
Information is seen from the waste situation
The waste is essentially the reverse image of the formed hole. That is the same part of the opposite position. By checking the waste, you can judge whether the gap between the upper and lower molds is correct. If the gap is too large, the waste will have rough, undulating fracture surfaces and a narrow bright band area.
The larger the gap, the larger the angle between the fracture surface and the bright zone. If the gap is too small, the waste will show a small angle fracture surface and a wide bright zone area.
Excessive gaps form holes with larger curled edges and torn edges, making the profile slightly protruding from a thin edge. A gap that is too small results in slight curling of the tape and a large angle tear, resulting in a cross-section more or less perpendicular to the material surface.
Ideal waste material should have a reasonable collapse angle and a uniform bright band. This keeps the punching force to a minimum and forms a neat round hole with few burrs. From this point of view, extending the life of the die by increasing the gap is at the expense of the quality of the finished hole.
Selection of mold gap
The gap of the mold is related to the type and thickness of the stamped material. Unreasonable clearance can cause the following problems:
(1) If the gap is too large, the burrs of the stamped workpiece will be relatively large and the stamping quality will be poor. If the gap is too small, although the punching quality is better, the wear of the die is more serious, which greatly reduces the service life of the die, and it is easy to cause the punch to break.
(2) If the gap is too large or too small, it is easy to cause adhesion on the punch material, resulting in stripping during punching. If the gap is too small, it is easy to form a vacuum between the bottom surface of the punch and the sheet material and cause the scrap to rebound.
(3) Reasonable clearance can prolong the life of the mold, the discharge effect is good, the burr and flanging are reduced, the plate is kept clean, the hole diameter is the same, and the plate is not scratched, the number of sharpening is reduced, the plate is kept straight, and the punching positioning is accurate.
How to improve the service life of the mold?
For users, increasing the service life of the mold can greatly reduce the cost of stamping. The factors that affect the service life of the mold are as follows:
3.1. The type and thickness of the material;
3.2. Whether to choose a reasonable die clearance;
3.3. The structure of the mold;
3.4. Whether the material has good lubrication when stamping;
3.5. Whether the mold has undergone special surface treatment;
3.6, such as titanium plating, carbon titanium nitride;
3.7. The neutrality of the upper and lower turrets;
3.8. Reasonable use of adjusting gaskets;
3.9. Whether the oblique edge mold is properly used;
3.10. Whether the mold base of the machine tool has worn out;
Matters needing attention in punching special size holes
(1) Minimum aperture
For punching in the range of φ0.8-φ1.6, please use a special punch.
(2) When punching thick plates, please use a mold that is one size larger than the processing hole diameter.
Note: At this time, if the usual size mold is used, the thread of the punch will be damaged.
(3) The ratio of the minimum width to the length of the punch cutting edge should generally not be less than 1:10.
For example, when the length of the cutting edge is 80mm for the rectangular punch, the width of the cutting edge is ≥8mm.
(4) The relationship between the minimum size of the punch blade and the plate thickness. It is recommended that the minimum size of the punch cutting edge is twice the thickness of the plate.
Sharpening of the mold
5.1. The importance of mold sharpening
Regular sharpening of the die is the guarantee of the consistency of punching quality. Regular sharpening of the mold can not only increase the service life of the mold but also the service life of the machine. The correct timing of sharpening must be grasped.
5.2, the specific characteristics of the mold that needs to be sharpened
For the sharpening of molds, there is no strict number of blows to determine whether sharpening is required. Mainly depends on the sharpness of the cutting edge. Mainly determined by the following three factors:
(1) Check the fillet of the cutting edge, if the fillet radius reaches R0.1 mm (the maximum R-value must not exceed 0.25 mm), sharpening is required.
(2) Check the punching quality, whether there are large burrs?
(3) Judge whether sharpening is required by the noise of machine punching. If the noise is abnormal when the same mold is punched, it means that the punch is blunt and needs sharpening.
Note: If the edge of the cutting edge is rounded or the rear of the cutting edge is rough, sharpening should also be considered.
5.3, the method of sharpening
There are many ways to sharpen the mold, which can be realized by a special sharpening machine or on a surface grinder. The sharpening frequency of punch and lower die is generally 4:1. Please adjust the height of the die after sharpening.
(1) The harm of incorrect sharpening method: Incorrect sharpening will aggravate the rapid destruction of the edge of the mold, resulting in a greatly reduced number of blows per sharpening.
(2) The benefits of the correct sharpening method: sharpen the mold regularly, and the quality and accuracy of the punching can be kept stable. The cutting edge of the mold is damaged more slowly and has a longer life.
5.4. Sharpening rules
The following factors should be considered when mold sharpening:
(1) The rounded corner of the cutting edge depends on the sharpness of the cutting edge in the case of R0.1-0.25 mm.
(2) Clean the surface of the grinding wheel.
(3) It is recommended to use a loose, coarse-grained, soft grinding wheel. Such as WA46KV
(4) The amount of grinding (cutting amount) each time should not exceed 0.013 mm. Excessive grinding will cause the mold surface to overheat, which is equivalent to annealing treatment and the mold becomes soft, which greatly reduces the life of the mold.
(5) Sufficient coolant must be added during sharpening.
(6) When grinding, ensure that the punch and the lower die are fixed and stable, and use special fixtures.
(7) The sharpening amount of the mold is fixed, if it reaches this value, the punch will be scrapped. If you continue to use it, it is easy to cause damage to the mold and the machine, and the gain is not worth the loss.
(8) After sharpening, the edges should be treated with a whetstone to remove excessively sharp edges.
(9) After sharpening, clean, demagnetize, and apply oil.
Note: The amount of sharpening of the mold mainly depends on the thickness of the sheet being punched.
Pay attention to the punch before use
(1) Wipe the inside and outside of the upper mold cover with a clean cloth.
(2) Be careful not to have scratches or dents on the surface during storage.
(3) Oiling to prevent rust.
6.2 Preparation before use
(1) Thoroughly clean the upper mold sleeve before use.
(2) Check whether there are scratches or dents on the surface. If so, remove it with an oilstone.
(3) Oiling inside and out.
6.3. Matters needing attention when installing the punch on the upper die sleeve
(1) Clean the punch and oil its long handle.
(2) Insert the punch into the bottom of the upper mold sleeve on the large-station mold, without force. Nylon hammers cannot be used. During installation, the punch cannot be fixed by tightening the bolt on the upper die sleeve, and the bolt can be tightened only after the punch is correctly positioned.
6.4. Install the upper mold assembly into the turret
If you want to extend the service life of the mold, the gap between the outer diameter of the upper mold sleeve and the turret hole should be as small as possible. So please perform the following procedures carefully.
(1) Clean the keyway and inner diameter of the turret hole and apply oil.
(2) Adjust the keyway of the upper die guide sleeve to match the key of the turret hole.
(3) Insert the upper mold sleeve straight into the tower hole, being careful not to have any tilt. The upper die guide sleeve should slide into the turret hole by its own weight.
(4) If the upper die sleeve is inclined to one side, use a soft material tool such as a nylon hammer to tap it lightly. Repeat percussion until the upper die guide sleeve slides into the correct position by its own weight.
Note: Do not use force on the outer diameter of the upper die guide sleeve, but only on the top of the punch. Do not hit the top of the upper die sleeve to avoid damage to the turret hole and shorten the service life of individual stations.
If the punch is bitten by the material and cannot be taken out, please check according to the following items.
7.1. Re-sharpening of punch and die.
A mold with a sharp edge can produce a beautiful cut surface. If the edge is blunt, additional punching pressure is required. Moreover, the section of the workpiece is rough, which produces great resistance, causing the punch to be bitten by the material.
7.2. The gap of the mold.
If the gap of the mold is not properly selected relative to the plate thickness, the punch needs a large demolding force when it is separated from the material. If the punch is bitten by the material for this reason, please replace the lower die with reasonable clearance.
7.3. The state of the processed material.
When the material is dirty or dirty, the dirt adheres to the mold, making the punch bite by the material and unable to process.
7.4. Deformed materials.
The warped material will clamp the punch after punching the hole, causing the punch to be bitten. For warped materials, please flatten them before processing them.
7.5. Excessive use of springs.
Will make the spring fatigue. Please always check the performance of the spring.
The amount of oil and the number of oil injections depend on the conditions of the processing material. For non-rust and non-scaling materials such as cold-rolled steel plates and corrosion-resistant steel plates, the mold should be filled with oil. The oil injection points are the guide bushing, the oil injection port, the contact surface between the cutter body and the guide bushing, and the lower mold. Use light engine oil for the oil.
For materials with rust and dirt, the rust powder will be sucked between the punch pin and the guide sleeve during processing, which will cause dirt to prevent the punch from sliding freely in the guide bushing. In this case, oiling will make the rust easier.
Therefore, when flushing this material, the oil should be wiped off instead, decomposed once a month, using gasoline (diesel) oil to remove the dirt on the punch and lower mold, and then wipe it off before reassembly. This will ensure that the mold has good lubricating properties.
Precautions for using special molding tools
9.1. Different types of machine slides have different strokes, so pay attention to the adjustment of the closed height of the forming mold.
9.2. It is necessary to ensure that the molding is adequate, so it needs to be adjusted carefully. The adjustment amount should not exceed 0.15 mm each time. If the adjustment amount is too large, it is easy to cause damage to the machine and the mold.
9.3. For stretch forming, please choose a light spring assembly to prevent the sheet from tearing or difficult to unload due to uneven deformation.
9.4. Install a spherical support mold around the forming mold to prevent the sheet from tilting.
9.5. The forming position should be as far away from the clamp as possible.
9.6. Forming processing is best implemented at the end of the processing program.
9.7. Be sure to ensure good lubrication of the board.
9.8. Pay attention to the issue of the transfer of special molding tools when ordering. If the distance between the two moldings is relatively close, please be sure to communicate with the salesperson of our company.
9.9. Because the molding tool requires a long discharge time, a low speed must be used during the molding process, and a delay is best.
Precautions for using a rectangular cutting knife
10.1 The step distance should be as large as possible, which should be greater than 80% of the entire tool length.
10.2 It is better to realize the jumping nibbling by programming.
10.3. It is recommended to use oblique edge molds.
How to punch holes without exceeding the nominal force of the machine
It is necessary to punch round holes larger than 114.3mm in diameter during the production process. Such a large hole will exceed the upper limit of the machine’s nominal force, especially for high shear strength materials.
This problem can be solved by punching large-size holes through multiple punching methods. Using a small size mold to cut along a large circumference can reduce the punching force by half or more, which can be done by most molds in the molds you already have.
A simple way to punch large round holes
This convex lens mold can be made into the radius size you need. If the hole diameter exceeds the nominal force of the punch, we recommend the use of an (A) plan. Use this mold to punch out the circular perimeter.
If the hole diameter can be punched within the nominal force range of the punch, then a radial mold and a convex lens mold can punch the required holes in four times without rotating the mold (B).
Finally formed downward
When choosing a forming die, you should avoid downward forming operations, as this will take up too much vertical space and cause additional flattening or bending of the sheet. Downward forming may also fall into the lower mold and then be pulled out of the turret.
However, if downward forming is the only process option, it should be used as the final processing step for the sheet.
Prevent material distortion
If you need to punch a large number of holes in the sheet and the sheet cannot be kept flat, the cause may be the accumulation of stamping stress. When punching a hole, the material around the hole is stretched downward, which increases the tensile stress on the upper surface of the sheet.
The undershooting movement also causes compressive stress on the lower surface of the sheet to increase. For punching a small number of holes, the result is not obvious, but as the number of punching holes increases, the tensile and compressive stresses also increase exponentially until the sheet is deformed.
One way to eliminate this deformation is to punch every other hole, and then return to punch the remaining holes.
Although this produces the same stress on the plate, it disintegrates the accumulation of tensile stress/compressive stress due to continuous punching one after another in the same direction. This also makes the first batch of holes share the deformation effect of the second batch of holes.
If the stainless steel flanging is deformed
Apply a high-quality forming lubricant to the material before the flanging, which can better separate the material from the mold and move smoothly on the surface of the lower mold during forming.
This gives the material a better opportunity to distribute the stress generated when it is bent and stretched and prevents the deformation on the edge of the formed flanging hole and the wear of the bottom of the flanging hole.
Several suggestions to overcome the difficulty of unloading
16.1 Use punches with fine-core rubber particles.
16.2 Increase the clearance of the die.
16.3. Check the fatigue of the spring.
16.4. Use heavy-duty molds.
16.5. Appropriate use of oblique edge molds.
16.6. Lubricate the board.
16.7. Large-station molds need to install polyurethane discharge heads.
The main reason for the rebound of scrap
17.1 The sharpness of the cutting edge.
The larger the rounded corner of the cutting edge, the easier it is to cause the scrap to rebound.
17.2 The modulus of the mold.
When each station die is stamped, the requirement of the modulus is certain, and the modulus is small, which is easy to cause the scrap to rebound.
17.3. Is the mold clearance reasonable? An unreasonable mold gap can easily cause a scrap rebound.
17.4. Whether there is an oil stain on the surface of the processed plate.
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