1. Information 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 area. 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 a slight curling of the tape and a tear at a large angle, resulting in the cross section being more or less perpendicular to the surface of the material.
An 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 very few burrs. From this point of view, extending the life of the mold by increasing the gap is at the expense of the quality of the finished hole.
2. the choice 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 quality of the punching is better, the wear of the die is more serious, greatly reducing 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.
3.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:
- 1. The type and thickness of the material;
- 2. Whether to choose a reasonable die clearance;
- 3. The structure of the mold;
- 4. Whether the material has good lubrication when stamping;
- 5. Whether the mold has undergone special surface treatment;
- 6. Such as titanium plating, carbon titanium nitride;
- 7. The neutrality of the upper and lower turrets;
- 8. Reasonable use of adjusting gaskets;
- 9. Whether the oblique edge mold is properly used;
- 10. Whether the mold base of the machine tool has been worn out;
4. the problems that should be paid attention to when punching special size holes
- (1) Please use a special punch for punching the smallest hole diameter from φ0.8 to φ1.6.
- (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.Example 1. According to the processing conditions in the following table, although the processing aperture corresponds to the mold of the A station, please use the mold of the B station.
- (3) The ratio of the minimum width to the length of the punch cutting edge should generally not be less than 1:10.Example 3. For rectangular punch, when the length of the cutting edge is 80mm, the width of the cutting edge is ≥8mm.
- (4) The relationship between the minimum size of the punch cutting edge and the plate thickness. It is recommended that the minimum size of the cutting edge of the punch is twice the thickness of the plate.
5.the sharpening of the mold
1. The importance of mold sharpening
Regular sharpening of the mold 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.
2. The specific characteristics of the mold that need to be sharpened
For the sharpening of molds, there is no strict number of blows to determine whether sharpening is necessary. 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 during the stamping of the same die, it means that the punch is blunt and needs to be sharpened.
Note: If the edge of the cutting edge is rounded or the rear of the cutting edge is rough, sharpening should also be considered.
3. The method of sharpening
There are many ways to sharpen the mold, which can be achieved with 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: Periodically sharpen the mold, 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.
4. Sharpening rules
The following factors should be considered when mold sharpening:
- (1) In the case of R0.1-0.25mm size, the fillet of the cutting edge depends on the sharpness of the cutting edge.
- (2) The surface of the grinding wheel should be cleaned up.
- (3) It is recommended to use a loose, coarse-grained, soft grinding wheel. Such as WA46KV
- (4) The grinding amount (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, the mold becomes soft, and the life of the mold is greatly reduced.
- (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 oilstone 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.
6. 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.
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 with oilstone.
- (3) Oiling inside and out.
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 die sleeve on the large-station die 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.
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 die guide sleeve straight into the tower hole, being careful not to have any tilt. Pay attention to the WeChat official account mold master, the upper mold guide sleeve should slide into the turret hole by its own weight.
- (4) If the upper mold 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: Don’t apply force to the outer diameter of the upper die guide sleeve, only apply force to the top of the punch. Do not knock 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.
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 force is required. The rough section of the workpiece produces a great resistance, causing the punch to be bitten by the material.
2. The gap of the mold. If the gap of the die is not properly selected relative to the thickness of the plate, 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 a reasonable clearance.
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.
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.
5. Excessive use of springs. Will make the spring fatigue. Please always pay attention to 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 dirt-free 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 sleeve, the oil injection port, the contact surface between the cutter body and the guide sleeve, and the lower mold. Use light engine oil for oil.
For materials with rust and dirt, the rust powder will be sucked between the punch and the guide sleeve during processing, and dirt will be generated, which prevents the punch from sliding freely in the guide sleeve. In this case, if oil is applied, the rust will be easier Therefore, when flushing this material, the oil should be wiped clean instead, decomposed once a month, use gasoline (diesel) oil to remove the dirt on the punch and the lower mold, and then wipe it clean before reassembling. This will ensure that the mold has good lubricating properties.
9. Problems and solutions that often occur during the use of molds
Problem 1: The sheet comes out of the jaws
Problem five, difficult unloading problem two, serious mold wear
10. Precautions for using special molding tools
- 1. Different types of machine slides have different strokes, so pay attention to the adjustment of the closed height of the forming mold.
- 2. It must be ensured that the molding is adequate, so careful adjustment is required. 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.
- 3. For stretch forming, please use light spring components to prevent the sheet from tearing or difficult to unload due to uneven deformation.
- 4. Install a spherical support mold around the forming mold to prevent the sheet from tilting.
- 5. The forming position should be as far away as possible from the clamp.
- 6. The forming process is best implemented at the end of the processing program.
- 7. Be sure to ensure good lubrication of the board.
- 8. Pay attention to the problem 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. Because the forming tool requires a long discharge time, a low speed must be used during the forming process, and it is best to have a delay.
11. Precautions for using rectangular cutting knife
- 1. The step distance should be as large as possible, which should be greater than 80% of the entire tool length.
- 2. It is best to realize jumping nibbling through programming.
- 3. It is recommended to use oblique edge molds.
12. How to punch holes without exceeding the nominal force of the machine
It is necessary to punch round holes with a diameter greater than 114.3mm 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 may be done by most molds in the molds you already have.
13. A simple way to punch a big round hole
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 (A) plan. Use this mold to punch out the round 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)
14. Finally, it takes shape downwards
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. The downward forming may also fall into the lower mold, pay attention to the WeChat official account mold master, and then be pulled out of the turret. However, if the downward forming is the only process option, then it should be used as the last processing step for the plate.
15. Prevent material distortion
If you need to punch a large number of holes in the plate and the plate cannot be kept flat, the cause may be the accumulation of stamping stress. When a hole is punched, 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 the compressive stress on the lower surface of the plate 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 caused by continuous punching one after another in the same direction. This also allows the first batch of holes to share the partial deformation effect of the second batch of holes.
16. If your stainless steel flanging is deformed
Apply a high-quality forming lubricant to the material before manufacturing the flange, which can make the material better separate 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 deformation on the edge of the formed flanging hole and abrasion at the bottom of the flanging hole.
17. Several suggestions for overcoming the difficulty of unloading
- 1. Use a punch with fine core rubber particles.
- 2. Increase the clearance of the die.
- 3. Check the fatigue degree of the spring.
- 4. Use heavy-duty molds.
- 5. Appropriate use of oblique edge molds.
- 6. Lubricate the board.
- 7. Large-station molds need to install polyurethane discharge heads.
18. The main reason for the rebound of scrap
- 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.
- 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.
- 3. Whether the gap of the mold is reasonable. Unreasonable mold gap can easily cause scrap to rebound.
- 4. Whether there is oil stain on the surface of the processed plate.
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