1. Pay attention before using the punch
①. Clean the punch with a clean rag.
②. Check whether there are scratches or dents on the surface. If there is, use a whetstone to remove it.
③. Apply oil in time to prevent rust.
④ When installing the punch, be careful not to tilt it at any angle. Use a soft material tool such as a nylon hammer to knock it straight. The bolt can only be tightened after the punch is correctly positioned.
2. Installation and debugging of die
Particular care must be taken when installing and adjusting the die. Because stamping dies, especially large and medium-sized stamping dies, are not only expensive to manufacture, but also heavy and difficult to move in small quantities, personal safety should always be given top priority. For a punch with an infinite positioning device, a backing board should be added between the upper and lower dies. After the punch table 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 documents and die design requirements. Before the mold is moved onto the table, adjust it to the bottom dead center and a position 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 when tightening threads manually, and the pre-tightening force for the same thread is not equal, which will cause the upper and lower dies to shift, change the gap, and peel off the edge during the stamping process. Port failure occurs.
Before the mold trial, the mold should be fully lubricated and materials used for normal production should be prepared. Start the punch 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 elastic pressure, and then make appropriate adjustments to achieve the best technical state. For large, medium and small dies, 3, 5, and 10 pieces will be tested for initial inspection after production is discontinued. After passing the test, 10, 15, and 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.
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3. Stamping burrs
①. If the mold gap is too large or uneven, readjust the mold gap.
② If the mold material and heat treatment are improper, resulting in an inverted cone of the concave mold or the cutting edge is not sharp, the material should be selected reasonably, the working part of the mold should be made of carbide, and the heat treatment method should be reasonable. Mold expert WeChat: mujudaren
③. Stamping wear, grinding punch or insert.
④. The punch enters the concave mold too deeply. Adjust the depth of the punch entering the concave mold.
⑤. The guide structure is not precise or the operation is improper. Check the guide posts and bushings in the mold and the accuracy of the punch guide, and standardize the punch operation.
4. Jump on scraps
The mold gap is large, the punch is short, the influence of the material (hardness, brittleness), the stamping speed is too high, 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.
①. The sharpness of the cutting edge. The larger the radius of the cutting edge, the easier it is to cause the scrap to rebound. For stainless steel with relatively thin materials, a beveled cutting edge can be used.
② For relatively regular scraps, the complexity of the scraps can be increased or a polyurethane ejector pin can be added to the punch to prevent scraps from skipping and scratches can be added to the cutting edge of the die.
③. Whether the mold clearance is reasonable. Unreasonable mold gaps can easily cause scrap rebound. For small diameter holes, the gap is reduced by 10%. If the diameter is greater than 50.0 mm, the gap is enlarged.
④. Increase the depth of mold insertion. When stamping the mold at each station, the requirements for the input modulus are certain. If the input modulus is small, it is easy to cause the scrap to rebound.
⑤. Check whether there is oil stain on the surface of the material to be processed.
⑥. Adjust the stamping speed and stamping oil concentration.
⑦. Use vacuum adsorption.
⑧. Demagnetize punches, inserts and materials.
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5. Crushing and scratching
①. If there is oil or debris on the material belt or mold, causing crushing injuries, the oil must be wiped off and an automatic air gun should be installed to remove the debris.
②. The mold surface is not smooth and the surface finish of the mold should be improved.
③. The surface hardness of the parts is not enough, and the surface needs to be treated with chromium plating, carburizing, boronizing, etc.
④. The material becomes unstable due to strain, reducing lubrication, increasing compressive stress, and adjusting spring force.
⑤. Carry out inspection on the mold that has been discarded. Mold expert WeChat: mujudaren
⑥. If the product scratches the mold positioning or other places during operation, the mold positioning needs to be modified or lowered, and workers should be educated to handle it with care when working.
6. Scratches on the outer surface of the workpiece after bending
①. The surface of the raw material is not smooth. Clean and calibrate the raw material.
②. There is waste material in the molding blocks. Clean the waste between the blocks. .
③. If the molding block is not smooth, electroplating and polishing the molding block will improve the smoothness of the convex and concave molds.
④. The bending radius R of the punch is too small. Increase the bending radius of the punch.
⑤. The bending gap of the mold is too small. Adjust the bending matching gap of the upper and lower molds.
⑥. The concave mold forming block is equipped with rollers for forming.
7. Missing punching
Missing punching is generally caused by factors such as the punch being broken but not being discovered, the punch missing after mold repair, the punch sinking, etc. After mold repair, the first piece must be confirmed and compared with the sample to check whether there are any omissions and hedging. If the head sinks, the hardness of the upper mold pad should be improved.
8. Abnormal stripping
① If the stripper plate and the punch 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. form.
②. The mold gap is too small, and the punch requires a large demoulding 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.
③. If the die has an inverted taper, trim the die.
④. The blanking hole of the concave mold and the leaking hole of the lower mold base are not aligned. Repair the leaking hole.
⑤. Check the status of the processed materials. The dirt on the material adheres to the mold, causing the punch to be bitten by the material and unable to be processed. After punching the warped material, the punch will be clamped. If the warped material is found, it needs to be smoothed before processing.
⑥. The passivated edges of the punch and lower die must be sharpened in time. A mold with a sharp edge can produce a beautiful cut surface. If the edge is blunt, additional punching force is required, and the rough cross-section of the workpiece creates great resistance, causing the punch to be bitten by the material.
⑦. Appropriately use inclined edge punches.
⑧. Minimize wear, improve lubrication conditions, and lubricate the plate and punch.
⑨. If the spring or rubber has insufficient elasticity or fatigue loss, replace the spring in time.
⑩. The gap between the guide post and the guide bushing is too large. Repair or replace the guide post and guide bushing.
◎. Parallelism errors accumulate, re-grind and assemble.
◎. The hole on the push piece block is not vertical, causing the small punch to deviate. Repair or replace the push piece block.
◎. If the punch or guide post is not installed vertically, reassemble it to ensure verticality.
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9. The bent edge is not straight and the size is unstable
①.Add crimping or pre-bending process
②. The material pressing force is not enough, increase the pressing force
③. If the rounded corners of the convex and concave molds are worn asymmetrically or the bending force is uneven, adjust the gap between the convex and concave molds to make them uniform and polish the rounded corners of the convex and concave molds.
④The height dimension cannot be less than the minimum limit dimension
10. The extruded material on the curved surface becomes thinner
①. The die fillet is too small, increase the die fillet radius.
②. The gap between the convex and concave molds is too small. Correct the gap between the convex and concave molds.
11. The bottom of the concave part is uneven
①. The material itself is uneven and needs to be leveled.
②. The contact area between the top plate and the material is small or the ejection force is insufficient. The ejection device needs to be adjusted to increase the ejection force.
③. There is no ejection device in the die. The ejection device should be added or corrected.
④.Additional shaping process
12. Stainless steel flanging deformation
Applying a high-quality forming lubricant to the material before making the flange will allow the material 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 in the material, resulting in poor material flatness, may be caused by 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 punching a small number of holes, the results are not obvious, but as the number of punched holes increases, the tensile stress and compressive stress also increase exponentially until the material is deformed. Mold expert WeChat: mujudaren
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.
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14. The mold is severely worn
①. Replace worn mold guide components and punches promptly.
② Check whether the mold gap is unreasonable (too small) and increase the lower mold gap.
③. Minimize 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 material being processed. 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 the lower mold, and wipe them clean before reassembly. This ensures that the mold has good lubrication properties.
④. Improper sharpening method will cause annealing of the mold and aggravate wear. You should use a soft abrasive grinding wheel, use a small cutting amount, use a sufficient amount of coolant and clean the grinding wheel frequently.
15. Prevent stamping noise
The punch press is the most critical necessary equipment in the sheet metal processing industry. When the punch press is working, it will produce mechanical transmission noise, stamping noise and aerodynamic noise. The highest value of the noise can reach 125dB(A), which greatly exceeds the noise index requirements of 85dB(A) and below stipulated in the national standard. Therefore, it is harmful to the operating workers. and the surrounding environment (such as offices, residential areas, conference rooms, etc.) causing extremely serious damage and pollution. Effectively controlling this noise has become an urgent problem to be solved. In particular, the implementation of my country's first "Noise Law" and the increasing scale of environmental protection industrialization have accelerated the urgency of noise control.
Starting from the noise source of the punch press and the mold structure, we must pay attention to the following points to reduce the noise:
① Pay attention to mold maintenance and cleaning, and keep the cutting edge sharp.
②. The shape, quantity, material and punching line length of the mold cutting edge. The contact surface between the mold cutting edge and the part should not be too large. The punch should be used for beveled edge step punching so that the mold can cut into different depths at different positions. The whole process can achieve true instead of synchronously extruding.
③. The mold cutting edge must be perpendicular to the mounting surface, and the clearance between the convex and concave mold cutting edges must be reasonable. When unloading is difficult, you can increase the lower die clearance, increase the unloading force, and use methods such as soft-surface unloading plates.
④. Check the matching accuracy between each work template and process some exhaust grooves.
⑤. The stop plate is changed to small pieces, and the stripper plate and lower template are changed to insert type to reduce the attack area.
⑥. The spring ejection source of the stripper plate is changed to a T-shaped ejector pin. The spring is installed on the upper mold base. The contour sleeve is used with the ejector rod to ensure that the stripper plate still has a certain amount of free movement when the mold is open.
⑦. Keep the lubrication well and the mold free of interference and smooth.
⑧. The surfaces of the upper and lower mold bases are padded with aluminum plates for impact buffering.
⑨. After the mold is debugged, install a sound insulation cover or sponge board on the punch machine for sound insulation treatment.
⑩. Improve punch accuracy and reduce structural noise. A buffer, vibration and noise reduction oil cylinder is installed on the workbench. The gears use helical teeth to enhance lubrication and a gear cover is installed. A muffler is installed in the pneumatic system.
