1. Burr: Die blanking clearance is too large, too small or unevenly even, concave and convex die kerf is not sharp enough, poor punching state may produce burr.
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2. Uneven warpage of parts.
a. In the process of punching and cutting, the tensile and bending force of the product is large and easy to produce warpage. Improvements can be made by pressing the die and press plate tightly and keeping a sharp edge when punching.
All can receive good results.
b. When the shape of the part is complex, the shear force around the part is not uniform, so the force from the surrounding to the center, so that the warpage of the part. The solution is to increase the press force.
c. When oil and air are pressed between die and part, part and part, the part will be warped, especially for thin material and soft material. The warpage can be eliminated by uniform oiling and
Set up exhaust holes to eliminate the warpage phenomenon.
3. Wrinkling.
a. The stretching depth of the stamped parts is too deep, which causes the sheet material to flow too fast in the process of material walking and forms wrinkles.
b. The R angle of the concave die is too large during the stretching process of the stamping parts, which causes the convex die to be unable to press the material during the stretching process, resulting in the formation of wrinkles due to the fast flow of the plate material.
c. The press bar of the stamping part is not reasonable, and the press bar is too small and incorrectly positioned, which cannot effectively stop the sheet material from flowing too fast and forming wrinkles.
d. The unreasonable design of die positioning causes the pressed parts to be unable to hold down the material during stretching or the pressed material edge is too small, which causes wrinkling as the material cannot be held down during stretching.
The solution for wrinkling is to adopt reasonable pressing device and reasonable stretching bar. 4.
4. Error in dimensional accuracy.
a. The dimensional accuracy of the cutting edge in the mold manufacturing is not up to the standard, which causes the size of the parts to exceed the standard.
b. In the stamping production, the part is rebounded, causing the positioning surface of the next process and the part not to be fully compatible, and the deformation occurs during the stamping process, which affects the dimensional accuracy.
c. Poor positioning of the parts, unreasonable design, and movement of the parts during stamping. There are also defects in the design of the parts, which cause inaccurate positioning and affect the dimensional accuracy.
d. The multi-process parts are not adjusted properly in the previous process or the rounded corners are worn out, resulting in uneven deformation and dimensional changes after punching. For the above points causing dimensional accuracy problems
reasons, we should take necessary control measures, such as reasonable shape and tolerance level of stamping parts, improving the precision of die manufacturing, designing rebound compensation mechanism and other methods.
5. Crush injury.
a. Material surface has debris. Check whether there is debris on the material surface when stamping, and if there is debris, clean it up with air gun and rags.
b. Foreign matter on the surface of the mold. Use tools to clean up the foreign matter on the surface of the mold, and choose the appropriate lower die clearance according to the thickness of the plate.
c.The mold with material is magnetic. Change the processing order and punch the workpiece from outside to inside processing, row by row. Cut the edge first (cut the edge) and then punch the mesh hole, special forming stamping with deformation.
It is possible that the pressure is too high and the spring in the die needs to be replaced.
d. The stamping oil does not meet the requirements. Replace the existing stamping oil and choose a special stamping oil containing sulphurized extreme pressure additives. 6.
6. Scratch: The main reason for scratching the parts is sharp scars on the die or metal dust falling into the die. Preventive measures are to polish the marks on the die and clean up the metal dust.
7. bottom cracks: the main reason for cracks on the bottom of the part is poor material plasticity or the mold crimp ring is pressed too tight. Preventive measures are to replace the material with good plasticity or to loosen the crimper.
8. sidewall wrinkling: the main cause of the part sidewall wrinkling is the upper and lower mold installation material thickness is not enough (if relatively small, the thickness is allowed to become thinner) or eccentric. Resulting in a larger gap on one side and
The gap on the other side is smaller. The preventive measure is to replace the material and readjust the mold immediately.
&#;I just don't understand why we can't put this die in the press and make satisfactory parts without spending hours adjusting it. We paid good money for this die! They must have done something wrong when they designed or built it; otherwise we would be able to set it up and run it without making adjustments.&#;
Sound familiar? If you work in a sheet metal stamping operation or in a die building shop, you probably hear this frequently. Yes, die design is critical, but it&#;s only one element essential for manufacturing quality stamped parts. Variables such as the material&#;s mechanical properties, press speed and accuracy, lubricant type and application method, tool temperature, drawing ratio, punch and blank shape, holding pressure, and number of stations all play a part. Discovering how all process variables interact can help you find the root cause of typical stamping failures.
When the material coming into the die isn&#;t flat, the pressure pads holding it down and securing it may not have enough force to hold it flat during cutting and forming operations. This often results in excessive cutting burrs, bending in improper locations, and nonconforming geometries.
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When part flatness is lost, stampers often focus on the die. Tool- and diemakers shim stations and grind stations to try to &#;reflatten&#; the problem area. But dies can only slightly improve the flatness of the incoming sheet. They can be designed and engineered to retain sheet flatness, but it&#;s nearly impossible for the die to make a flat part out of incoming material&#;especially if the material has a very high tensile strength or is very thin.
In most of these cases, the problem is not the die, but the coil feeding and straightening equipment. The flatness and straightness of the incoming coil is a product of the straightener and leveler. Because the coil is wound tighter on the inside diameter than on the outside diameter, adjustments often need to be made to the coil feeder and straightener to compensate for coil set.
Too much wrinkling can cause splitting in a stamping operation. For example, if the metal is allowed to wrinkle in the blank holder or draw pad area, it will be forced to unwrinkle before flowing into the draw die cavity. This will likely result in restricted metal flow, which in turn causes excessive stretching, thinning, and necking. Similarly, if the metal is allowed to wrinkle before flowing over a draw bead, the resulting restrictive force can cause excessive thinning or splitting. The diemaker must prevent wrinkling to stop the splitting by increasing blank holder force, adjusting the standoffs or equalizers, or changing the blank shape and/or size.
Conversely, splitting can result in wrinkling. If the metal is being overstretched and splits, sheet tension will decrease, allowing the sheet to wrinkle. It&#;s much like poking a finger into a piece of plastic wrap: Once your finger pushes the wrap, it wrinkles. To eliminate splitting, the diemaker can try decreasing holding forces, changing or adding lubricant, polishing the tool, or making changes in the blank shape or geometry.
If the pitch or progression on a progressive die is not set up correctly or the pilot release is not properly calibrated, the die will not be able to locate and register the parts correctly in their respective stations. This will result in holes being pierced out of location and other features formed out of location.
An inexperienced diemaker may attempt to move the holes physically or make changes in the cutting or forming die geometry when the real problem lies with the timing of the feed release. For the die to register the strip properly within the tool, the feed release must let go of the material.
These are only a few examples of the interactivity that happens within a stamping process. Literally thousands of variables affect the stamping process, and a solution to a problem might involve a combination of several working together.
To find the root cause of stamping failure, you need to understand these variables and how they interact and take a systematic, data-based approach to the problem. Defect prevention is much better than defect correction.
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