1.Pay attention before using the punch
①Clean the punch
②Check the punch surface if there is any scratches and dents
③Put oil in time to prevent rust
④When installing the punch, be careful not to tilt it at any angle and ensure the correct position.
2.Tooling assembly and tryout
Particular care must be taken when installing and adjusting the die. Because stamping dies are not only expensive, especially large and medium-sized dies, but also heavy and difficult to move, the safety of workers should always be given top priority. For stamping die with infinite positioning devices, a backing board should be added between the upper and lower dies. After the punch workbench is cleaned, place the closed mold to be tested in a suitable position on the table.
The press slider stroke is selected according to the process and die design requirements. Before the mold is moved to the table, adjust it to the bottom dead center and 10 to 15mm greater than the mold closing height. Adjust the slider connecting rod and move the mold to ensure that the mold handle is aligned. Correct the mold handle hole and reach the appropriate mold mounting height. Generally, the punching die first fixes the lower die (not tightened) and then fixes the upper die (tightened). The T-bolts of the pressure plate should be tightened (lower die) with a suitable torque wrench to ensure that the same bolts have consistent and ideal pre-clamping. force. It can effectively prevent the pre-tightening force from being too large or too small due to physical strength, gender, and hand-feel errors in manual tightening of threads, and the pre-tightening force for the same thread is not equal, which may cause misalignment of the upper and lower dies, changes in gaps, and peeling edges during the stamping process. Port failure occurs.
Before the stamping die tryout, the tooling should be fully lubricated and materials used for normal production should be prepared. Start working 3 to 5 times during the idle stroke to confirm that the mold is operating normally before testing. Adjust and control the depth of the punch into the die, check and verify the performance and operational flexibility of the mechanisms and devices such as die guide, feeding, push-off, lateral pressure and spring, and then make appropriate adjustments to achieve the best technical condition. For large, medium and small dies, 3-10 pieces will be tested for initial inspection after production is discontinued. After passing the test, 10-30 pieces will be tested for re-inspection. After the scribing inspection, punching surface and burr inspection, all dimensions and shape accuracy are in line with the drawing requirements, it can be delivered for production.
3.Stamping has burrs problem
①The die gap is too large or uneven, readjust the gap.
②Improper tooling material and heat treatment will cause the lower mold to have an inverted taper or the cutting edge will not be sharp; therefore, materials should be selected reasonably, the working part of the mold should be made of carbide, and the heat treatment method should be reasonable.
③Stamping die wear, such as punch or insert wear
④The upper mold enters the lower mold too deep, adjust the depth
⑤The guide structure is not precise or the operation is improper. It is necessary to check the accuracy of the guide posts and bushings in the die and the pressing machine guide and standardize the pressing operation.
4. Scrap material jumps out
The stamping die gap is large, the punch die is short, the influence of the material (hardness, brittleness), the speed is too fast, the stamping oil is too sticky or the oil droplets are too fast, the stamping vibration causes the material chips to disperse, vacuum adsorption and mold core Insufficient demagnetization can cause waste chips to be brought to the mold surface.
①Is the mold clearance reasonable? Unreasonable mold clearance can easily cause scrap rebound. For small-diameter holes, the clearance is reduced by 10%. If the diameter is greater than 50.0 mm, the clearance is enlarged.
②Is there any oil stain on the surface of the material?
③Adjust stamping speed and stamping oil concentration
④Demagnetize punches, inserts and materials
5.Crushed, scratched
①If there is oil or waste on the strip or mold, it is necessary to wipe the oil and install an automatic air gun to remove the waste.
②The surface of the tooling is not smooth and the surface finish of the tooling should be improved.
③The surface hardness of the parts is not enough, and the surface needs to be treated with chromium plating, carburizing, boronizing, etc.
④Material destabilizes due to strain, reduces lubrication, increases compressive stress, adjusts spring force
⑤Processing of molds for jumping scrap
⑥During the production process, if the product hits the tooling locator or other places and causes scratches, the tooling locator needs to be modified or lowered, and the staff should be trained to handle it with care when working.
6.Scratch on the outer surface of the workpiece after bending
①Strip surface is not smooth, need to clean, calibrate the strip
②There is waste material in the molding block. Clean the waste between the blocks.
③The molding block is not smooth. Electroplating and polishing the molding block will improve the smoothness of the lower and upper die
④The punch bending radius R is too small, increase the punch bending radius
⑤The bending gap of the mold is too small. Adjust the bending clearance of the upper and lower molds.
7.Missing punching hole
Missing punching holes are generally caused by factors such as undiscovered punch breakage, missing punch installation after mold repair, punch sinking, etc. After tooling repair, the first piece must be confirmed and compared with the sample to check whether there are any missing. For sinking punches, the hardness of the upper die backing plate should be improved
8. Abnormal material stripping
①If the stripper plate and the punch of stamping die are too tight, the stripper plate is tilted, the height of the equal screws is not uniform, or other stripper parts are improperly installed, the stripper parts should be trimmed. The stripper screws should be a combination of sleeves and hexagon socket screws.
②The gap of stamping die is too small, and the punch requires a large demolding force when it is separated from the material, causing the punch to be bitten by the material, and the lower mold gap needs to be increased.
③The die has an inverted taper, trim the die
④The blanking hole of the die and the leaking hole of the lower mold base are not aligned. Repair the leaking hole.
⑤Check the condition of raw materials. If the dirt of the raw material adheres to the mold, the punch will be bitten by the material and cannot be processed. After punching the material with warped deformation, the punch will be clamped. If the material with warped deformation is found, it needs to be smoothed before processing.
⑥The blunt edges of punches and lower dies must be sharpened in time. A mold with a sharp edge can produce beautiful cut surfaces. A blunt edge requires additional punching force, and the workpiece has a rough cross-section, which creates great resistance and causes the punch to be bitten by the material.
⑦Proper use of inclined edge punches
⑧Minimize wear, improve lubrication conditions, lubricate plates and punches
⑨The spring or rubber has insufficient elasticity or fatigue loss. Change the spring in time.
⑩The gap between the guide post and the guide bushing is too large. Repair or replace the guide post and guide bushing.
⑪Accumulation of parallelism errors, re-grinding and assembly
⑫The punch or guide post is not installed vertically. Reassemble to ensure verticality.
9.The bending edge is not straight and the size is unstable
①Add crimping or pre-bending process
②The material pressing force is not enough, increasing the pressing force
③The rounded corners of the upper and lower dies are asymmetrically worn or the bending force is uneven. Adjust the gap between the upper and lower dies to make it uniform and polish the rounded corners of the upper and lower dies.
④The height dimension cannot be less than the minimum limit dimension
10. Extruded material becomes thinner on curved surfaces
①.Gaps are too small and fillets are too small
11.The bottom of the concave part is uneven
①The raw material itself is uneven and needs to be leveled
②The contact area between the top plate and the raw material is small or the ejection force is not enough. The ejection device needs to be adjusted to increase the ejection force.
③There is no ejection device in the lower die. The ejection device should be added or corrected.
④Increase forming station
12.Stainless steel flanging deformation
Using a high-quality forming lubricant before flanging the raw material will allow the product to better separate from the mold and move smoothly on the lower mold surface during forming. This gives the material a better chance to distribute the stress generated when it is bent and stretched, preventing deformation on the edge of the formed flange hole and wear at the bottom of the flange hole.
13.Material distortion
Punching a large number of holes into the tape, resulting in poor flatness of the tape, may be due to 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 downward punching movement also causes the compressive stress on the lower surface of the plate to increase. For a small number of punches, the results are not obvious, but as the number of punches increases, the tensile and compressive stresses also increase exponentially until the material is deformed.
One way to eliminate this distortion is to punch every other hole and then go back and punch the remaining holes. This creates the same stresses in the sheet, but breaks up the tensile/compressive stress buildup caused by consecutive punching cuts one after the other in the same direction. This also allows the first batch of holes to share the partial deformation effect of the second batch of holes.
14.Tooling wear
①Timely replace worn guide components and punches for stamping die
②Check whether the mold gap is unreasonable (too small) and increase the lower mold gap
③Minimize wear, improve lubrication conditions and lubricate the plate and punch. The amount of oil and the number of oil injections depend on the conditions of the processed materials. For rust-free materials such as cold-rolled steel plates and corrosion-resistant steel plates, the mold must be filled with oil. The oil filling points are the guide bushing, oil filling port, lower mold, etc. Use light engine oil. When processing rusty materials, the rust micropowder will be sucked into the space between the punch and the guide bushing, causing dirt to prevent the punch from sliding freely in the guide bushing. In this case, if oil is applied, it will be easier for rust to stick to the material. Therefore, when punching this kind of material, you should wipe the oil clean instead, disassemble it once a month, use gasoline (diesel) oil to remove the dirt on the punch and lower die, and wipe them clean before reassembly. This ensures that the mold has good lubrication properties
④Improper sharpening method will cause annealing of the mold and aggravate wear. You should use a soft abrasive grinding wheel, use a small cutting amount, sufficient coolant and clean the grinding wheel frequently.
