Design and production techniques for stamping dies

Jiuzhi Plastics Network Xiaobian finishing the stamping die design and production skills, welcome the industry to come to the reference.
I. Information from the situation of waste
The waste is essentially the reverse of the shaped hole. That is, the same part with the opposite position. By checking the waste, you can determine if the upper and lower mold gaps are correct. If the gap is too large, the scrap will have a rough, undulating fracture surface and a narrow band of light. The larger the gap, the larger the angle between the fracture surface and the bright belt region. If the gap is too small, the scrap will exhibit a small angle of fracture and a wide strip of light.
An excessively large gap forms a hole with a large bead and edge tear, giving the profile a slightly thin edge. A gap that is too small forms a slight curling and a large angle tear, resulting in a profile that is more or less perpendicular to the surface of the material.
An ideal waste should have a reasonable collapse angle and a uniform bright band. This keeps the punching force to a minimum and creates a neat round hole with minimal burrs. From this point of view, extending the die life by increasing the gap is in exchange for sacrificing the quality of the finished hole.
Second, the choice of mold gap
The gap of the mold is related to the type and thickness of the material being stamped. Unreasonable gaps can cause the following problems:
(1) If the gap is too large, the burr of the stamped workpiece is relatively large, and the stamping quality is poor. If the gap is small, although the quality of the punching is good, the wear of the mold is serious, the service life of the mold is greatly reduced, and the break of the punch is easily caused.
(2) If the gap is too large or too small, it is easy to cause adhesion on the punch material, thereby causing the material to be taken during the stamping. Too small a gap easily forms a vacuum between the bottom surface of the punch and the sheet material, and scraping occurs.
(3) Reasonable clearance can prolong the life of the mold, good discharge effect, reduce burr and flanging, keep the plate clean, the hole diameter will not scratch the plate, reduce the number of sharpening, keep the plate straight, and accurately punch the hole.
Third, how to improve the service life of the mold
For the user, 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. Type and thickness of the material;
2. Whether to choose a reasonable die clearance;
3. The structural form of the mold;
4. Whether there is good lubrication when the material is stamped;
5. Whether the mold has undergone special surface treatment;
6, such as titanium plating, titanium carbonitride;
7. Neutrality of the upper and lower turrets;
8. Adjust the reasonable use of the gasket;
9. Is it appropriate to use a beveled edge die;
10. Whether the machine tool holder has worn out;
Fourth, the problem of stamping special size holes should be noted
(1) For the punching of the range of the minimum aperture punching φ0.8——φ1.6, use a special punch.
(2) When punching thick plates, use a larger one than the machining hole. Note: At this time, if the mold of the normal size is used, the punch thread will be damaged.
(3) The cutting edge portion, the ratio of the minimum width to the length should generally not be less than 1:10.
(4) The relationship between the minimum size of the punch edge portion and the thickness of the plate. It is recommended that the minimum size of the punch edge portion be twice the thickness of the plate.
Fifth, the sharpening of the mold
1. The importance of mold sharpening
Regular sharpening of the mold is a guarantee of consistency in punching quality. Regular sharpening of the mold not only improves the life of the mold but also increases the service life of the machine. It is necessary to master the correct timing of sharpening.
2, the specific characteristics of the mold needs sharpening
For the sharpening of the mold, there is no strict number of hits to determine if sharpening is required. It depends mainly on the sharpness of the cutting edge. It is mainly determined by the following three factors:
(1) Check the rounded corners of the cutting edge. If the radius of the fillet reaches R0.1 mm (the maximum R value must not exceed 0.25 mm), sharpening is required.
(2) Check the punching quality, is there a large burr?
(3) Determine whether the sharpening is required by the noise of the machine press. If the noise of the same pair of die is abnormal during stamping, the punch is already blunt and needs sharpening.
Note: The edge of the edge is rounded or the back of the cutting edge is rough, and sharpening is also considered.
3, the method of sharpening
There are many ways to sharpen the mold, either with a special sharpening machine or on a flat grinding machine. The frequency of punching and lowering of the lower die is generally 4:1. Please adjust the height of the mold after sharpening.
(1) Hazard of incorrect sharpening method: Incorrect sharpening will aggravate the rapid destruction of the cutting edge of the mold, resulting in a significant reduction in the number of hits per sharpening.
(2) Benefits of the correct sharpening method: Regularly sharpening the mold, the quality and precision 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
Consider the following factors when sharpening the mold:
(1) The edge of the edge is to be seen in the case of R0.1-0.25 mm.
(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 amount of grinding (the amount of knife) should not exceed 0.013 mm. The excessive amount of grinding will cause the surface of the mold to overheat, which is equivalent to annealing, 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 amount of sharpening of the mold is certain. If this value is reached, the punch will be scrapped. If you continue to use it, it will easily cause damage to the mold and the machine, which is not worth the loss.
(8) After the sharpening, the edge part should be treated with oil stone to remove the excessively sharp ridgeline.
(9) After the sharpening, clean, demagnetize, and oil.
Note: The amount of mold sharpening depends mainly on the thickness of the sheet being stamped.
Six, the punch should pay attention before use
1, storage
(1) Wipe the inside and outside of the upper mold cover with a clean rag.
(2) Be careful not to scratch or dent when storing.
(3) Oiling and rust prevention.
2, preparation before use
(1) Thoroughly clean the upper mold sleeve before use.
(2) Check the surface for scratches and dents. If so, remove with oil stone.
(3) Oiling inside and outside.
3. Precautions when installing the punch on the upper die set
(1) Clean the punch and apply oil to its long handle.
(2) Insert the punch into the bottom of the upper die sleeve on the large-station mold, and do not use force. Can not use nylon hammer. When installing, the punch cannot be fixed by tightening the bolt on the upper die sleeve. The bolt can only be tightened after the punch is correctly positioned. The content of Zhengquan Technology WeChat is really good, it is worthy of attention!
4, the installation of the upper mold into the turret
If you want to extend the life of the mold, the gap between the outer diameter of the upper sleeve and the turret hole should be as small as possible. So please be careful to perform the following procedures.
(1) Clean the keyway and inner diameter of the turret hole and oil.
(2) Adjust the keyway of the upper mold 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 inclination. The upper die guide sleeve should slide into the turret hole by its own weight.
(4) If the upper die sleeve is tilted to one side, it can be tapped repeatedly with a soft material tool such as a nylon hammer until the upper die bushing slides into the correct position by its own weight.
Note: Do not use the outer diameter of the upper guide bushing. Only apply force on the top of the punch. Do not hit the top of the mold sleeve to avoid damage to the turret hole and shorten the service life of individual stations.
Seven, mold maintenance
If the punch is bitten by the material and cannot be taken out, please check it as listed below.
1. Re-sharpening of the punch and the lower die. The sharp-edged die can produce a beautiful cut surface, and the cutting edge is blunt, which requires additional punching force, and the workpiece has a rough section, which generates a great resistance, causing the punch to be bitten by the material.
2, the gap of the mold. If the gap of the mold is not properly selected relative to the thickness of the mold, the punch requires a large release force when it is detached from the material. If the punch is bitten by the material for this reason, replace the lower die with a reasonable clearance. The content of Zhengquan Technology WeChat is really good, it is worthy of attention!!
3. The state of the processed material. When the material is dirty or has dirt, dirt adheres to the mold, so that the punch is bitten by the material and cannot be processed.
4. A deformed material. The warped material will clamp the punch after the hole is punched, causing the punch to be bitten. If there is warped material, please flatten it and then process it.
5. Excessive use of springs. Will make the spring fatigue. Always check the performance of the springs.
Eight, oil injection
The amount of oil and the number of times of oiling depend on the conditions of the material being processed. For cold-rolled steel sheets and corrosion-resistant steel sheets, etc., the mold should be oiled. The oil injection points are the guide sleeve, the oil injection port, the contact surface of the cutter body and the guide sleeve, and the lower mold. Light oil for oil.
There is rust and scaly material. When processing, the rust powder will be sucked between the punch and the guide bush to produce dirt, so that the punch can not slide freely in the guide sleeve. In this case, if the oil is applied, the rust will be easier. Dip on, so when rushing this material, the opposite is to wipe off the oil, decompose it once a month, use the steam (wood) oil to remove the dirt from the punch and the lower mold, and wipe it off before reassembling. This will ensure that the mold has good lubrication properties.
Nine, problems and solutions often encountered in the use of molds
Problem 1. The plate is pulled out from the jaws.
Reason: The mold unloading is not complete
1. Using a tapered punch
2. Apply lubricant to the board
3. Using heavy duty mold
Problem 2, the mold wear is serious
Reason: Unreasonable mold gap (small)
Solution: increase the mold gap
Cause: The upper and lower mold bases are misaligned
1. Work station adjustment, centering the upper and lower molds
2. Turret level adjustment
Reason: The worn-out mold guide assembly and the turret inserts were not replaced in time.
Solution: Replace
Cause: The punch is overheated
1. Add lubricating fluid to the sheet.
2. Ensure lubrication between the punch and the lower die
3. Use multiple sets of molds of the same size in the same program.
Cause: Improper sharpening method causes annealing of the mold, resulting in increased wear
1, using soft abrasive wheel
2, often clean the grinding wheel
3, the amount of small knife
4, a sufficient amount of coolant
Reason: small step size
1, increase the step size
2, using bridge type
Question 3, punch material and punch adhesion
Reason: Unreasonable mold gap (small)
Solution: increase the mold gap
Reason: punch edge passivation
Solution: timely sharpening
Cause: poor lubrication
Solution: Improve lubrication conditions
Question 4, scrap rebound
Reason: Die problem
1, using the anti-ball material under the mold
2, for small diameter hole clearance reduced by 10%
3, the diameter is greater than 50.00 mm, the gap is enlarged
4, the edge of the die edge increases scratches
Reason: punch aspect
1, increase the depth of the mold
2, installation and discharge polyurethane primer rod
3, the use of oblique edge
Problem 5, difficulty in unloading
Reason: Unreasonable mold gap (small)
Solution: increase the mold gap
Reason: punch wear
Solution: timely sharpening
Reason: spring fatigue
Solution: replace the spring
Reason: punch adhesion
Solution: remove the adhesion
Question 6, punching noise
Reason: difficulty in discharging
1, increase the die clearance, good lubrication
2, increase the discharge force
3. Unloading plate with soft surface
Reason: There is a problem with the support of the sheet on the workbench and in the turret.
1, using a spherical support mold
2, reduce the working size
3, increase the working thickness
4, sheet thickness
5, using oblique edge punch
X. Precautions for using special molding tools
1. The strokes of different types of machine sliders are different, so pay attention to the adjustment of the closing height of the forming mold.
2, must ensure sufficient molding, so need to be carefully adjusted, each adjustment is best not to exceed 0.15 mm, if the adjustment is too large, it is easy to cause damage to the machine and mold damage.
3. For stretch forming, please use a light spring assembly to prevent tearing of the sheet material or difficulty in unloading due to uneven deformation. The content of Zhengquan Technology WeChat is really good, it is worthy of attention!!
4. Install a spherical support mold around the molding die to prevent the sheet from tilting.
5. The molding position should be as far as possible from the clamp.
6, molding processing is best to achieve at the end of the processing program.
7, must ensure that the board is well lubricated.
8. Pay attention to the problem of giving up the special molding tools when ordering. If the distance between the two moldings is relatively close, please communicate with the salesperson of the company.
9, because the forming tool requires a long discharge time, so the molding process must use low speed, it is best to have a delay.
XI, the use of rectangular cutting knife precautions
1. The step size is as large as possible, which is greater than 80% of the entire tool length.
2, it is best to achieve jump jump by programming.
3. It is recommended to use the oblique edge die.
Twelve, how to punch without exceeding the nominal force of the machine
A circular hole larger than 114.3 mm in diameter is required in the production process. Such large holes can exceed the machine's nominal force limit, especially for high shear strength materials. This problem can be solved by punching out large holes by multiple punching. Using a small-sized mold to cut along a large circumference can reduce the punching force by half or more, and most of the molds you can have in the mold you already have.
Thirteen, a simple method of punching a large round hole
This convex lens mold can be made to the radius you need. If the aperture exceeds the nominal force of the press, we recommend using the (A) scheme. Use this mold to punch out the rounded perimeter. If the aperture can be punched into the punch's nominal force range, then a radial mold and a convex lens mold can punch the required hole in four times without rotating the mold (B)
Fourteen, finally formed downward
When forming a forming tool, the downward forming operation should be avoided as this would take up too much vertical space and result in additional flat or curved sheeting operations. Forming down may also sink into the lower die and then be pulled out of the turret. However, if down forming is the only process choice, it should be used as the final step in the sheet.
Fifteen, prevent material distortion
If you need to punch a large number of holes in the sheet and the sheet can not be 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 plate. The undershooting motion also causes the compressive stress on the lower surface of the plate to increase. For a small number of holes, the results are not obvious, but as the number of punches increases, the tensile and compressive stresses multiply until the sheet is deformed. The content of Zhengquan Technology WeChat is really good, it is worthy of attention!!
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 sheet, the tensile stress/compressive stress buildup is caused by the punching of one continuous one in the same direction. This also allows the first batch of holes to share the deformation effects of the second batch of holes.
Sixteen, if your stainless steel flange deformation
The application of a high quality forming lubricant to the material prior to the manufacture of the burring allows the material to be better separated from the mold and smoothly moved over the surface of the lower mold during forming. This gives the material a better chance of distributing the stresses that are created when bent and stretched, preventing deformations that occur on the edges of the formed flanged edges and wear on the bottom of the flanged holes.
Seventeen, several suggestions to overcome the difficulty of unloading
1. Use a punch with fine core rubber.
2. Increase the gap between the lower molds.
3. Check the fatigue of the spring.
4. Use heavy-duty molds.
5. Appropriate use of oblique edge die.
6. Lubricate the board.
7. The large-station mold needs to be equipped with a polyurethane discharge head.
Eighteen, the main reason for the rebound of waste
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 stamping each station mold, the requirement of the modulus of the mold is certain, and the modulus of the mold is small, which is easy to cause the scrap to rebound.
3. Is the clearance of the mold reasonable? Unreasonable mold gaps can easily cause scrap to rebound.
4. Whether there is oil on the surface of the processed sheet.

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