Mold Repair Solutions
When your mold encounters issues, what should you do? Below are some carefully compiled repair solutions for molds that I hope can help you in your daily life!
1. Precautions before using punches:
① Clean the punches with a clean cloth.
② Check for scratches or dents on the surface. If present, remove them with an oil stone.
③ Apply oil for rust prevention in a timely manner.
④ When installing punches, be careful not to tilt them in any way. Use soft tools like nylon hammers to gently align them. Only tighten the bolts after the punch is properly positioned.
2. Installation and adjustment of the die:
The installation and adjustment of the die must be done with special care. Large and medium-sized dies, in particular, are not only expensive but also difficult to move due to their weight. Personal safety should always be the top priority. For dies with limit devices, a wooden block should be placed between the upper and lower dies. After cleaning the workbench of the press, place the test mold in the appropriate position on the table in the closed position.
Set the stroke of the press slide, as determined by the process documents and die design requirements, to the bottom dead center and a position 10-15mm higher than the mold closing height before placing the mold on the table. Adjust the slide linkage and move the mold to ensure that the handle aligns with the handle hole and reaches the appropriate mold installation height. Generally, for blanking dies, the lower die should be fixed first (not tightened), and then the upper die should be fixed (tightened). The T-bolts of the pressure plate should be tightened with an appropriate torque wrench (for the lower die) to ensure consistent and ideal pre-clamping force for the same bolts. This can effectively prevent the occurrence of problems such as misalignment of the upper and lower dies, changes in clearance, and edge chipping caused by excessive or insufficient pre-clamping force due to physical strength, gender, or manual tightening errors.
Before testing the mold, lubricate it thoroughly and prepare normal production materials. Start the mold in an idle stroke for 3-5 times to confirm that the mold is operating normally before conducting a trial run. Adjust and control the depth of the male mold entering the female mold, check and verify the performance and flexibility of the mold guiding, feeding, stripping, side pressure, and rebound mechanisms and devices. Then make appropriate adjustments to achieve the optimal technical state. For large, medium, and small molds, conduct initial inspections by testing 3, 5, and 10 pieces respectively. After passing the inspection, conduct a recheck by testing 10, 15, and 30 pieces. Only when the line marking inspection, punching surface and burr inspection, and all dimensional and positional accuracy meet the requirements of the drawings can the mold be put into production.
3. Deburring in Stamping
① Adjust the mold clearance if it is too large or uneven.
② Improper mold material and heat treatment may result in a concave die with a taper or dull edges. Proper material selection and the use of hard alloy for the working parts of the mold, as well as appropriate heat treatment, are necessary.
③ If there is stamping wear, grind the punches or inserts.
④ Adjust the depth of the male mold entering the female mold if it is too deep.
⑤ Check the precision of the guiding structure and ensure proper operation. Inspect the guide pillars and bushes inside the mold and the guiding accuracy of the press. Follow standardized press operation procedures.
4. Jumping Scrap
Large mold clearance, short punch length, material properties (hardness, brittleness), high stamping speed, excessive viscosity of stamping oil, or excessive oil droplets can cause adhesion. Stamping vibrations can lead to scattered debris, vacuum adsorption, and insufficient demagnetization of the core, all of which can result in scrap sticking to the mold surface.
① Check the sharpness of the edges. Larger rounded edges are more likely to cause scrap bouncing. For thin materials like stainless steel, slanted edges can be used.
② For regular scrap shapes, increase the complexity of the scrap or add polyurethane rods on the punch to prevent jumping scrap. Add scratches on the side of the die edge.
③ Check if the mold clearance is reasonable. Improper mold clearance can lead to scrap bouncing. Reduce the clearance by 10% for small-diameter holes and increase it for diameters larger than 50.00 millimeters.
④ Increase the depth of entry into the mold. Each station of the mold has specific requirements for the depth of entry. A smaller entry depth can cause scrap bouncing.
⑤ Check if the surface of the processed material is oily.
⑥ Adjust the stamping speed and concentration of stamping oil.
⑦ Use vacuum suction.
⑧ Demagnetize the punches, inserts, and materials.
5. Compression and Scratching
① Oil and scrap on the strip or mold can cause compression. Wipe off the oil and use an automatic air gun to remove the scrap.
② If the mold surface is not smooth, improve the surface finish of the mold.
③ The surface hardness of the part may be insufficient. Consider chrome plating, carburizing, boronizing, or other surface treatments.
④ The material may become unstable due to strain. Reduce lubrication, increase pressure, and adjust spring force.
⑤ During operation, if the product scrapes against the mold positioning or other areas, modify or lower the mold positioning and educate the operators to handle the workpiece with care.
6. Surface Scratches after Workpiece Bending
① The surface of the raw material is not smooth. Clean and level the raw material.
② There is scrap between the forming blocks. Remove the scrap between the blocks. Regarding mold issues, some repair solutions for molds.
③ The forming blocks are not smooth. Electroplate and polish the forming blocks to improve the surface smoothness of the male and female molds.
④ The bending radius (R) of the male mold is too small. Increase the bending radius of the male mold.
⑤ The bending clearance of the mold is too small. Adjust the bending clearance between the upper and lower molds.
⑥ Add roller pins to the female mold block for forming.
7. Missing Punches
The occurrence of missing punches is usually caused by factors such as undetected punch breakage, missing installation of punches after mold repair, or sinking of punches. After mold repair, a first-piece confirmation should be conducted, comparing it with the sample to check for any omissions. If the punches sink, improve the hardness of the upper die pad.
8. Abnormal Part Ejection
① The ejection plate is too tight or tilted in relation to the male mold, the heights of the equal-height screws are inconsistent, or other ejection devices are improperly installed. Adjust the ejection components. Use a combination of bushings and internal hexagon screws for the ejection screws.
② The mold clearance is too small, requiring a large ejection force for the punches to disengage from the material. This can cause the punches to get stuck in the material. Increase the clearance of the lower mold.
③ The female mold has a taper. Adjust the female mold.
④ The material ejection holes in the female mold and the material leakage holes in the lower mold seat are not aligned. Adjust the leakage holes.
⑤ Check the condition of the processed material. If the material is dirty and adheres to the mold, it can cause the punches to get stuck and prevent processing. If the material is warped or deformed, it can clamp the punches after punching. Flatten the warped or deformed material before processing.
⑥ Sharpen the punches and the edges of the lower mold in a timely manner. Mold with sharp edges can produce clean cut surfaces. Dull edges require additional stamping force, resulting in rough workpiece surfaces and increased resistance, causing the punches to get stuck in the material.
⑦ Consider using punches with slanted edges.
⑧ Minimize wear, improve lubrication conditions for the sheet and punches.
⑨ Replace the spring if it lacks elasticity or shows fatigue wear.
⑩ The clearance between the guide pillars and guide bushes is too large. Repair or replace the guide pillars and guide bushes.
◎ Accumulated parallelism errors. Re-grind and assemble.
◎ The holes on the stripper block are not perpendicular, causing the small male mold to be misaligned. Repair or replace the stripper block.
◎ The male mold or guide pillars are not installed vertically. Reassemble to ensure perpendicularity.
9. Uneven Bending Edge and Unstable Dimensions
① Increase the pressure line or pre-bending process.
② Insufficient material pressure force, increase the pressure force.
③ Asymmetric wear of the rounded corners of the male and female molds or uneven bending forces. Adjust the clearance between the male and female molds to make it even and polish the rounded corners.
④ The height dimension should not be smaller than the minimum limit dimension.
10. Thinning of Material due to Surface Compression during Bending
① The radius of the female mold is too small. Increase the radius of the female mold.
② The clearance between the male and female molds is too small. Adjust the clearance between the male and female molds.
11. Uneven Bottom of Concave Parts
① The material itself is not flat. Level the material.
② Insufficient contact area between the top plate and the material or insufficient top pressure. Adjust the top material device and increase the top pressure.
③ No top material device in the concave mold. Add a top material device or make corrections.
④ Add a forming process.
12. Deformation of Stainless Steel Flanging
Apply high-quality forming lubricant to the material before flanging. This helps the material separate better from the mold and move smoothly on the surface of the lower mold during forming. Some repair solutions for mold issues. This gives the material a better chance to distribute the stress generated during bending and stretching, preventing deformation on the edge of the flanging hole and wear at the bottom of the flanging hole.
13. Material Distortion
Cutting a large number of holes in the material can result in poor flatness of the material, which may be caused by accumulated stamping stress. When cutting a hole, the surrounding material is pulled downward, increasing the tensile stress on the upper surface of the sheet and the downward motion causes an increase in compressive stress on the lower surface of the sheet. For a small number of holes, the effect may not be significant, but as the number of holes increases, the tensile and compressive stresses also increase exponentially, causing material deformation.
One method to eliminate this deformation is to cut every other hole and then return to cut the remaining holes. This creates the same stress on the sheet but disrupts the accumulation of tensile/compressive stress caused by continuous cutting in the same direction. This also allows the first batch of holes to share the deformation effects of the second batch of holes.
14. Severe Mold Wear
① Timely replace worn mold guide components and punches.
② Check if the mold clearance is unreasonable (too small) and increase the clearance of the lower mold.
③ Minimize wear, improve lubrication conditions, lubricate the sheet and punches. The amount of oil and the number of oil injections depend on the processing material. For materials such as cold-rolled steel and corrosion-resistant steel without rust deposits, oil should be injected into the mold at the guide bushing, oil injection port, and lower mold. Use light machine oil for lubrication. For materials with rust deposits, during processing, rust particles can be sucked between the punch and the guide bushing, causing dirt and preventing the punch from sliding freely in the guide bushing. In this case, oiling will make it easier for rust deposits to adhere. Therefore, when punching such materials, the opposite approach is taken: wipe off the oil and disassemble once a month, use gasoline (diesel) to remove dirt from the punch and lower mold, and clean them before reassembly. This ensures good lubrication performance of the mold.
④ Improper grinding methods can cause annealing of the mold and exacerbate wear. Soft abrasive grinding wheels should be used, with small cutting depths, sufficient coolant, and regular cleaning of the grinding wheel.
15. Preventing Stamping Noise
The punch press is the most critical and essential equipment in the sheet metal processing industry. During operation, the punch press generates mechanical transmission noise, stamping noise, and aerodynamic noise. The noise level can reach up to 125dB(A), greatly exceeding the noise level requirements of 85dB(A) and below specified by national standards. This causes severe harm and pollution to operators and the surrounding environment (such as offices, residential areas, conference rooms, etc.). Effectively addressing this noise has become an urgent problem, especially with the implementation of China's first "Noise Law" and the increasing scale of environmental protection industrialization, which has further accelerated the urgency of noise control.
To reduce noise starting from the noise sources of the punch press and mold structure, the following points should be considered:
① Pay attention to mold maintenance and cleanliness, and keep the cutting edges sharp.
② The shape, quantity, material, and length of the mold cutting edges, as well as the contact area between the mold cutting edges and the parts, should not be too large. Use inclined step-cutting for the punches to achieve different cutting depths at different positions, ensuring a true cutting process instead of synchronous shearing. Some repair solutions for mold issues. Mold design.
③ The mold cutting edges must be perpendicular to the mounting surface, and the clearance between the male and female molds should be reasonable. When it is difficult to eject the material, increase the clearance of the lower mold and the ejection force. Use soft-surfaced ejection plates, and other methods.
④ The mating accuracy between the various working templates and the machining of some exhaust grooves.
⑤ Change the stop plate to small block components, use inserts for the ejection plate and lower mold plate, and reduce the impact area.
⑥ Change the ejection mechanism to a T-shaped ejector rod, with the spring installed in the upper mold seat and the equal-height sleeve used with the ejector rod, ensuring that the ejection plate still has a certain amount of free movement in the open mold state.
⑦ Maintain good lubrication and ensure smooth operation without interference in the mold.
⑧ Use aluminum plates as cushioning buffers on the surfaces of the upper and lower mold seats.
⑨ After proper mold adjustment, install soundproof covers or sponge panels on the punch press for sound insulation treatment.
⑩ Improve the precision of the punch press and reduce structural noise. Install cushioning and vibration-reducing oil cylinders on the workbench, use helical gears for enhanced lubrication and install gear covers, and install mufflers in the pneumatic system.
1: Maintenance of Molds
1. After prolonged use, the cutting edges of the molds must be sharpened, and the sharpened surfaces must be demagnetized to eliminate magnetic properties. Otherwise, material blockage may occur. Companies using molds should keep detailed records and statistics of their usage, maintenance (lubrication, cleaning, rust prevention), and damage. This information can help identify damaged components, assess the degree of wear, and provide data for problem detection and resolution. It also includes the molding process parameters for the mold and the materials used for the products, which can shorten the mold trial time and improve production efficiency. During normal operation of the injection molding machine and mold, various mold performance tests should be conducted, and the dimensions of the final molded plastic parts should be measured. This information can determine the current condition of the mold and identify the damage to the cavity, core, cooling system, and parting surfaces. Based on the information provided by the plastic parts, the damaged state of the mold and the necessary repair measures can be determined.
2: Elastic components such as springs are prone to damage during use, often resulting in fracture and deformation. The solution is to replace them. During the replacement process, attention must be paid to the specifications and models of the springs. The specifications and models of the springs are determined by color, outer diameter, and length. Replacement is only possible when all three parameters are the same. Imported springs are of better quality.
3: During the use of molds, punches are prone to breakage, bending, and gnawing, while bushings are generally subject to gnawing. Damaged punches and bushings are generally replaced with parts of the same specifications. The parameters of the punches mainly include the dimensions of the working part, the dimensions of the installation part, and the length.
4: Fasteners should be checked for looseness or damage. If any issues are found, replacement with fasteners of the same specifications is necessary.
5: Pressure components such as pressure plates and rubber pads, as well as unloading components such as ejector plates and pneumatic ejectors, should be inspected during maintenance. Check the relationship between various parts and whether there is any damage. Repair the damaged parts. For pneumatic ejectors, check for air leakage and take appropriate measures based on the specific situation. If the air tube is damaged, it should be replaced. Key components of the mold should be closely monitored and tested. The function of ejection and guide components is to ensure the opening and closing movement of the mold and the ejection of plastic parts. If any part is stuck due to damage, it will cause production stoppage. Therefore, it is necessary to regularly lubricate the ejector pins and guide posts (using the most suitable lubricant) and periodically check for deformation and surface damage. If any issues are found, timely replacement is required. After completing a production cycle, the working surfaces, movements, and guide components of the mold should be coated with professional rust preventive oil. Special attention should be given to protecting the gear, rack, bearing areas, and the spring strength of spring-loaded molds to ensure they are always in optimal working condition. Over time, cooling channels may accumulate scale, rust, sludge, and algae, leading to a reduction in the cross-sectional area and narrowing of the cooling passages. This significantly reduces the heat exchange rate between the cooling fluid and the mold, increasing production costs. Therefore, cleaning of the channels should be given due attention. For hot runner molds, maintenance of the heating and control systems is crucial to prevent production failures and is therefore particularly important.
