Frequently asked questions and solutions for hardware molds ""

Common problems and solutions for hardware molds "Recommended"

Various problems are often encountered during mold debugging and maintenance. These problems will seriously affect the delivery time of the product and the mold. life cycle. Below, I will share with you the common problems and solutions of hardware molds. I hope it will be helpful to everyone!

Skip scrap

The mold gap is large, the punch is short, and the material is Influence (hardness, brittleness), too high stamping speed, adhesion caused by excessive viscosity of stamping oil or oil droplets too fast, divergence of scraps caused by stamping vibration, vacuum adsorption and insufficient degaussing of the mold core, etc. can all cause scraps to be brought to the mold. On the 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 skipping of scraps and increase scratches on the cutting edge side of the die.

③. Is the mold clearance 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 will be 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 any oil stain on the surface of the material being processed.

⑥. Adjust the stamping speed and stamping oil concentration.

⑦. Use vacuum adsorption.

⑧. Demagnetize punches, inserts and materials.

Crushes and scratches

① If there is oil or debris on the material belt or mold, causing crushing, the oil must be wiped off and an automatic air gun should be installed to remove the debris.

②. The surface of the mold 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. Repair the mold that has scrapped materials.

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.

The outer surface of the workpiece is scratched after bending

① The surface of the raw material is not smooth, clean and level the raw material.

②. There is waste material in the molding blocks. Clean the waste between the blocks.

③. 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 clearance of the upper and lower dies.

⑥. The concave mold forming block is equipped with rollers for forming.

Attention should be paid 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 are any, use a whetstone to remove them.

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.

Installation and adjustment of the die

The installation and adjustment of the die must be particularly careful. 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 punches with infinite positioning devices, a backing board should be added between the upper and lower dies. After the punch table is cleaned, place the clamped 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 in manual tightening of threads, and the pre-tightening force for the same thread is not equal, resulting in misalignment of the upper and lower dies, changes in gaps, and edge peeling during the stamping process. Port failure occurs.

Before the mold trial, fully lubricate the mold and prepare materials for normal production. 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. Test punch 3, 5, and 10 pieces of large, medium, and small dies respectively for initial inspection after production is discontinued. After passing the test, 10, 15, and 30 pieces will be tried for re-inspection.

Only after scribing inspection, punching surface and burr inspection, all dimensions and shape accuracy are in compliance with the drawing requirements, can it be delivered for production.

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, the concave mold will have an inverted taper or the cutting edge will not be sharp. Materials should be selected reasonably. Carbide should be used for the working part of the mold, and the heat treatment method should be reasonable.

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.

Missing punching

Missing punching is usually caused by factors such as the punch being broken but not found, missing punch after repairing the mold, sinking of the punch and other factors. After repairing the mold, It is necessary to confirm the first piece, compare it with the sample, and check whether there are any omissions. If the punch head sinks, the hardness of the upper mold backing plate should be improved.

Abnormal stripping

①. The stripping plate and the punch are too tight, the stripping plate is tilted, the height of the equal screws is not uniform, or other stripping parts are improperly installed. To trim the stripping parts, the stripping screws are a combination of sleeves and hexagon socket screws.

②. The die 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 die 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 material with warped deformation, the punch will be clamped. If the material with warped deformation is found, it needs to be smoothed before processing.

⑥. The passivated edges of punches and lower dies 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 error accumulates, 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.

The bent edge is not straight and the size is unstable

①. Increase the 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 asymmetrically worn 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.

Severe wear of the mold

① Timely replace the worn mold guide components and punches.

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. For rusty materials, the rust powder will be sucked into the space between the punch and the guide bushing during processing, causing dirt so that the punch cannot slide freely in the guide bushing. In this case, if oil is applied , will make it easier for rust to stick to it. Therefore, when punching this kind of material, wipe the oil clean instead, disassemble it once a month, use gasoline (diesel) oil to remove the dirt on the punch and the lower die, and reassemble it before reassembly. Wipe it clean. 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.

Prevent stamping noise

Punch is the most critical and 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 very 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, you 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 made with a beveled edge and step punching so that the mold can cut in at different positions. The depth is different, and the entire process achieves real cutting, rather than simultaneous extrusion.

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, the lower die clearance can be increased, the unloading force can be increased, and a soft-surface unloading plate can be used and other methods.

④. The matching accuracy between each work template and processing of 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 source of ejection of the stripper plate is changed to 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 degree of elasticity when the mold is open. Amount of free movement.

⑦. Keep the lubrication well and the mold free of interference and smooth.

⑧. The upper and lower mold base surfaces 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 the accuracy of punching machines 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.

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.

The bottom of the concave part is uneven

①. The material itself is uneven and the material needs to be leveled.

②. The contact area between the top plate and the material is small or the ejection force is not enough. The ejection device needs to be adjusted to increase the ejection force.

③. There is no ejection device in the die, and the ejection device should be added or corrected.

④.Add shaping process.

Stainless steel flange deformation

Applying high-quality forming lubricant to the material before making the flange can make the material better separated from the mold and flow smoothly during forming. The mold surface moves. 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.

Material distortion

A large number of holes are punched into the material, resulting in poor flatness of the material. 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, and the downward punching movement also causes the compressive stress on the lower surface of the plate. 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.

One way to eliminate this deformation is to punch every other hole, and then go back and punch the remaining holes. Although this produces the same stress on the sheet, it breaks up the tensile/compressive stress accumulation caused by consecutive punching cuts 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.

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