1. What are the key points in the maintenance of continuous molds?
The maintenance of continuous molds must be careful, patient, and orderly, and blind work should be avoided. When repairing molds due to failures, it should be accompanied by a material belt for problem inquiry. Open the mold, refer to the material belt, check the mold condition, confirm the cause of the failure, find the problem, then clean the mold, and then disassemble the mold. The force during disassembly should be balanced. For the mold structure where the material removal spring is between the fixing plate and the material removal plate and the material removal spring directly pushes on the inner guide column, the disassembly of the material removal plate should ensure that the material removal plate pops out in balance. The tilt of the material removal plate may cause the breakage of the convex mold in the mold.
(1) Maintenance of convex and concave molds
When disassembling the convex and concave molds, you should pay attention to the original condition of the mold, in order to facilitate the recovery during subsequent assembly. If there is padding or displacement, the thickness of the gasket should be engraved on the part and recorded. When replacing the convex mold, you should try to insert whether the material removal block concave mold is smooth, and try to insert whether the gap between the concave mold is even. When replacing the concave mold, you should also try to insert whether the gap between the punch is even. For the convex mold that needs to be padded after repairing and grinding, it should be checked whether the effective length of the convex mold is enough. When replacing the broken convex mold, you should find out the reason, and check whether the corresponding concave mold has chipped edges and whether it needs to grind the edge. When assembling the convex mold, check whether there is enough gap between the convex mold and the fixing block or fixing plate. If there is a pressure block, check whether there is enough movement margin. The concave mold should be placed horizontally, and then use a flat iron block to place it on the concave mold surface and use a copper rod to lightly tap it into place. It must not be forcibly knocked in at an angle. The bottom of the concave mold should be chamfered. After installation, check whether the surface of the concave mold is flat with the mold surface. After the convex mold, concave mold, and mold core are assembled, necessary checks should be made against the material belt, whether each part is installed incorrectly or reversed, check whether the concave mold and the concave mold pad block are installed reversely, whether the material drop hole is blocked, whether the newly replaced parts need to steal material, whether the sufficient material is stolen, and whether the mold needs to be tightened. Pay attention to the confirmation of the tightening of the material removal plate screws. When tightening, it should go from inside to outside, balance the force and cross tighten, and it should not first tighten a screw and then tighten another screw, so as not to cause the material removal plate to tilt and cause the convex mold to break or the mold accuracy to decrease.
(2) Maintenance of the material removal plate
The disassembly of the material removal plate can first use two screwdrivers to balance the pry, and then use both hands to balance the force to remove. In case of difficulty in disassembly, check whether the mold is cleaned, whether the locking screws are all disassembled, whether the mold damage caused by the card material should be checked, find out the reason and then deal with it accordingly, and blind disposal should not be done. When assembling the material removal plate, first clean the convex mold and the material removal plate, add lubricating oil at the guide column and the convex mold guide in, put it in smoothly, then press it in with both hands, and repeat several times. If it is too tight, find out the reason (whether the guidance of the guide column and the guide sleeve is normal, whether there are any damages in each part, whether the new convex mold can smoothly pass the position of the material removal plate is correct), find out the reason and then deal with it accordingly. The fixed plate with a pressure block should check whether there is enough material stolen on the back plate of the material removal. The material contact surface between the material removal plate and the concave mold, long-term stamping produces indentation (the material gap between the material removal plate and the concave mold is generally the material thickness minus 0.03-0.05mm, when the indentation is serious, it will affect the pressing accuracy of the material, causing the product size to be abnormal and unstable, etc., it is necessary to repair or re-grind the material removal insert block and the material removal plate. The high sleeve should be checked for accuracy, it will cause the material removal plate to tilt when it is not equal high, its precision guiding and smooth pressing function will be damaged, and it must be maintained.
(3) Guiding part inspection
Check the fit clearance of the guide column and guide sleeve, whether there are burn marks or wear marks, and whether the oil supply status of the mold guide is normal. The wear and tear and precision damage of the guide parts reduce the accuracy of the mold, and problems will occur in various parts of the mold. Therefore, appropriate maintenance and regular replacement must be carried out. Check the accuracy of the guide parts. If the guide pin is worn and has lost the required precision and function of the material belt guide, it must be replaced. Check the condition of the spring (material removal spring and top material spring, etc.) to see if it is broken or has been used for a long time but has not broken, but has lost its original strength. Regular maintenance and replacement must be carried out, otherwise it will cause damage to the mold or production is not smooth.
(4) Adjustment of mold clearance
The positioning hole of the mold core wears due to frequent and multiple combinations of the mold core, resulting in a larger gap after assembly (loose after assembly) or uneven gap (positioning deviation), which will cause the shape of the section after punching to deteriorate, and the convex mold is easy to break, burrs, etc., can be checked through the condition of the section after punching, and appropriate gap adjustment. When the gap is small, there are fewer sections, and when the gap is large, there are more sections and larger burrs. Obtain a reasonable gap by shifting, and after adjustment, make appropriate records, or make marks on the edge of the concave mold, etc., for subsequent maintenance work. Daily production should pay attention to collecting and saving the material belt when the original mold is in better condition. If the subsequent production is not smooth or the mold produces variation, it can be used as a reference for mold repair. In addition, auxiliary systems such as whether the top material pin is worn, whether it can top the material, whether the guide pin and liner are worn, should be checked and maintained.
2. What are the main reasons for mold explosion?
Due to different stamping processes and working conditions, the reasons for mold explosion are multifaceted. The following are comprehensive analyses of the causes of mold explosion from the aspects of mold design, manufacture, and use, and corresponding improvement measures are proposed.
(1) The mold material is not good and it is easy to break in subsequent processing
Different material molds often have different lives. Therefore, two basic requirements are put forward for the material of the punch workpiece: ① The material performance should have high hardness (58~64HRC) and high strength, and have high wear resistance and sufficient toughness, small heat treatment deformation, and certain hot hardness; ② Good process performance. The manufacturing process of the punch workpiece is generally complicated. Therefore, it must have adaptability to various processing technologies, such as forgeability, machinability, hardenability, hardenability, quenching crack sensitivity, and grinding processability. Usually, according to the material characteristics of the stamping parts, production batch, precision requirements, etc., select excellent mold materials, while considering its processability and economy.
(2) Heat treatment: deformation caused by improper quenching and tempering process
Practice has proved that the quality of mold heat processing has a great impact on the performance and service life of the mold. From the analysis and statistics of the reasons for mold failure, it can be known that the "accident" of mold failure caused by improper heat treatment accounts for more than 40%. The quenching deformation and cracking of the mold workpiece, and the early fracture during use, are all related to the heat processing technology of the mold.
1) Forging process:
This is an important link in the manufacturing process of the mold workpiece. For high-alloy tool steel molds, technical requirements are usually put forward for the carbide distribution and other metallographic organizations of the material. In addition, the forging temperature range should be strictly controlled, the correct heating specification should be formulated, the correct forging force method should be adopted, and slow cooling or timely annealing after forging should be adopted.
2) Preliminary heat treatment:
Depending on the material and requirements of the mold workpiece, different preliminary heat treatment processes such as annealing, normalizing or tempering should be used to improve the structure, eliminate the organizational defects of the forging blank, and improve the processability. High-carbon alloy mold steel can eliminate network secondary carburized body or chain carbides, spheroidize and refine carbides, and promote the uniformity of carbide distribution through appropriate preliminary heat treatment. This is beneficial to ensure the quality of quenching and tempering, and improve the life of the mold.
3) Quenching and tempering:
This is a key link in mold heat treatment. If overheating occurs during quenching heating, it will not only cause greater brittleness of the workpiece, but also easily cause deformation and cracking during cooling, seriously affecting the life of the mold. Special attention should be paid to preventing oxidation and decarburization during the quenching heating of the punch. Strict control of heat treatment process specifications should be implemented, and vacuum heat treatment can be used where conditions permit. After quenching, tempering should be carried out in time, and different tempering processes should be adopted according to technical requirements.
4) Stress relief annealing:
After rough machining, the mold workpiece should be subjected to stress relief annealing treatment. The purpose is to eliminate the internal stress caused by rough machining, so as not to cause excessive deformation and cracking during quenching. For molds with high precision requirements, after grinding or electrical processing, they still need to undergo stress relief annealing treatment, which is beneficial to stabilize the mold accuracy and improve the service life.
(3) The flatness of the mold grinding is not enough, causing bending deformation
The quality of the surface of the mold workpiece is closely related to the wear resistance, fracture resistance, and anti-adhesion ability of the mold, and directly affects the life of the mold. Especially the surface roughness value has a great impact on the life of the mold. If the surface roughness value is too large, stress concentration will occur during work, and cracks are easy to occur between the peaks and valleys, affecting the durability of the punch, and also affecting the corrosion resistance of the workpiece surface, directly affecting the life and accuracy of the punch.
For this reason, the following points should be noted:
1) During the processing of the mold workpiece, it is necessary to prevent the phenomenon of grinding burn on the surface of the part, and strictly control the grinding process conditions and process methods (such as grinding wheel hardness, grain size, coolant, feed amount and other parameters);
2) During the processing, it should be prevented that macro defects such as tool marks, interlayers, cracks, and impact scars remain on the surface of the mold workpiece. The existence of these defects will cause stress concentration, become the source of fracture, and cause early failure of the mold;
3) Use grinding, lapping and polishing and other precision and fine processing to obtain a smaller surface roughness value and improve the life of the mold.
(4) Design process: The mold strength is not enough, the knife edge spacing is too close, the mold structure is unreasonable, the number of template blocks is not enough without the gasket foot, the mold guide is inaccurate, and the gap is unreasonable.
1) Layout and overlapping.
Unreasonable reciprocating feeding layout methods and too small overlap values often cause rapid wear of the mold or gnawing of the punch and die. Therefore, while considering improving the utilization rate of materials, it is necessary to choose the layout method and overlap value reasonably according to the processing batch of the parts, quality requirements, and the fit clearance of the mold, in order to improve the life of the mold.
2) The accuracy of the mold guiding mechanism.
Accurate and reliable guidance has a great impact on reducing the wear of mold workpieces and avoiding gnawing of punches and dies, especially for gapless and small-gap punching dies, compound dies, and multi-station progressive dies. To improve the life of the mold, it is necessary to correctly choose the guide form and determine the accuracy of the guide mechanism according to the nature of the process and the accuracy requirements of the parts. Generally, the accuracy of the guiding mechanism should be higher than the fit clearance of the punch and die.
3) Geometric parameters of the mold (punch and die) cutting edge.
The shape, fit clearance, and fillet radius of the punch and die not only have a great impact on the forming of stamped parts, but also have a great impact on the wear and life of the mold. For example, the fit clearance of the mold directly affects the quality of the punching parts and the life of the mold. For those with higher precision requirements, a smaller clearance value should be chosen; otherwise, the clearance can be appropriately increased to improve the life of the mold.
(5) Wire cutting process:
Artificial dragging wire cutting, improper treatment of wire cutting gap, not chamfering, and the impact of the hardened layer of wire cutting.
The cutting edge of the punch die is mostly processed by wire cutting. Due to the thermal effect and electrolysis of wire cutting, a certain thickness of hardened layer is produced on the surface of the mold, causing the surface hardness to decrease, micro-cracks appear, etc., causing the punch die processed by wire cutting to wear early, directly affecting the maintenance of the punching gap of the mold and the cutting edge is easy to chipping, shortening the life of the mold. Therefore, in wire cutting processing, a reasonable electrode standard should be selected to minimize the depth of the hardened layer.
6) Selection of punching machine equipment: punching machine tonnage, insufficient punching force, too deep under the mold adjustment.
The precision and rigidity of stamping equipment (such as presses) have a very important impact on the life of the punch die. The higher the precision and the better the rigidity of the stamping equipment, the longer the life of the punch die. For example: complex silicon steel sheet punch die material is Cr12MoV, used on ordinary open presses, the average regrinding life is 1-30,000 times, while on the new precision press, the regrinding life of the punch die can reach 60-120,000 times. Especially for small gap or gapless punch dies, hard alloy punch dies and precision punch dies must choose high-precision, high-rigidity presses, otherwise, it will reduce the life of the mold, and in serious cases, it will damage the chess tool.
(7) Stamping Process:
Deviation in material thickness tolerance, material property fluctuations, poor surface quality (such as rust stains), or unclean surfaces (such as oil stains) of stamped parts can result in increased wear and tear on the working components of the mold and lead to adverse consequences such as blade breakage.
1) Whenever possible, use materials with good stamping processability to reduce stamping deformation forces.
2) Before stamping, carefully inspect the material's grade, thickness, surface quality, etc., and clean the material by wiping it. If necessary, remove surface oxides and rust stains.
3) Depending on the stamping process and material type, consider implementing softening treatments and surface treatments, as well as selecting suitable lubricants and lubrication processes.
(8) Correct Usage and Proper Maintenance in Production Operations:
1) Difficulty in material removal: Lack of demagnetization treatment and lack of material discharge; occurrence of material jamming due to broken needles or springs during production.
2) Difficulty in material feeding: No leakage during mold assembly or occurrence of rolling or blocking of material discharge; occurrence of material jamming due to foot pad blockage.
3) Production awareness: Improper positioning in stacked sheet stamping, failure to use air blow guns, and continuing production with cracked templates.
To protect normal production, improve the quality of stamped parts, reduce costs, and extend the life of the stamping die, it is necessary to use and maintain the mold correctly. Strictly adhere to the "three inspections" system for the mold (pre-use inspection, in-use inspection, and post-use inspection), and perform mold maintenance and repair work. This includes correctly installing and debugging the mold, strictly controlling the depth of the male die entering the female die, controlling the lower stop point of the mold in processes such as correction, cold extrusion, and shaping, timely grinding of blade edges, and ensuring the cleanliness and proper lubrication of the mold.
In summary, the application of advanced manufacturing technology and comprehensive quality management throughout the entire process of mold design, manufacturing, use, and maintenance is an effective guarantee for improving mold life. It is also important to focus on developing specialized production, strengthening mold standardization work, including not only part standardization but also standardization of design parameters, assembly forms, and processing methods, to continuously improve mold design and manufacturing capabilities, which will contribute to extending mold life.
3. What are the causes of burrs in mold stamping parts, and what countermeasures should be taken?
The causes of burrs in mold stamping parts and the corresponding improvement measures are as follows:
1) Blade wear or edge chipping, low hardness after quenching, requiring blade repair.
2) If the gap is too large and the effect is not obvious after blade repair, further control the machining accuracy of the male and female dies or modify the design clearance.
3) If the gap is not reasonable and there is vertical or horizontal misalignment, further adjust the punching clearance, confirm mold hole wear or workpiece processing accuracy issues.
4) Misalignment of the mold, requiring replacement of guide components or remolding.
4. What are the causes of chip jumping and compression damage in mold stamping parts, and what countermeasures should be taken?
The causes of chip jumping and compression damage in mold stamping parts and the corresponding countermeasures are as follows:
1) When the gap is too large, control the machining accuracy of the male and female dies or modify the design clearance.
2) If improper feeding is the cause, trim the strip when it reaches the appropriate position and clean the mold in a timely manner.
3) If the stamping oil drips too quickly and becomes sticky, control the amount of stamping oil or replace it with a lower viscosity oil.
4) If the mold is not demagnetized, it must be demagnetized after repair (especially for iron stamping materials).
5) If the male die is worn and the chips adhere to it, the male die blade needs to be repaired.
6) If the male die is too short and does not enter the female die sufficiently, adjust the length of the male die entering the female die.
7) If the material is relatively hard and the cutting shape is simple, a chamfer or curved surface can be added to the end face of the male die to reduce the contact area between the male die and the chips.
Emergency measures include reducing the sharpness of the female die edge, reducing the amount of repair on the female die edge, increasing the roughness (coating) of the straight edge surface of the female die, using a vacuum cleaner to remove waste material, reducing the stamping speed, and slowing down chip jumping.
5. What are the causes of chip blockage in mold stamping parts, and what countermeasures should be taken?
The causes of chip blockage in stamping parts and the corresponding countermeasures are as follows:
1) If the material discharge hole is too small, increase the clearance of the material discharge hole.
2) If the material discharge hole is too large and the chips roll over, modify the material discharge hole accordingly.
3) If the blade is worn and the burr is large, the blade needs to be repaired.
4) If the stamping oil drips too quickly and becomes sticky, control the oil drip amount and consider changing the type of oil.
5) If the straight edge surface of the female die is rough and powder chips adhere to it, surface treatment, polishing to reduce surface roughness, or changing the material can be considered.
6) If the material is relatively soft, modify the punching clearance.
The emergency measures are as follows:
Add a slope or arc to the end face of the male die blade (pay attention to the direction), use a vacuum cleaner, and blow air at the material discharge hole on the cushion plate.
6. What are the reasons for dimensional variation in material deviation during mold stamping, and what countermeasures should be taken?
The main causes of dimensional variation in material deviation during stamping and the corresponding countermeasures are as follows:
1) Blade wear on the male and female dies, resulting in burrs (oversized outer shape, undersized inner hole), requiring blade repair.
2) Improper design clearance, modify the design and control the machining accuracy.
3) Misalignment of the male die, female die insert block, etc., and uneven gaps, adjust their positional accuracy and punching clearance.
4) Worn guide pins, insufficient pin diameter, replace the guide pins.
5) Worn guide components, replace the guide pillars and bushings.
6) Improper adjustment of the feeding distance and material relaxation of the feeder, readjust the feeder.
7) Improper adjustment of the mold's closed height, readjust the closed height.
8) Wear on the material discharge block, lack of pressure (strong pressure) function or material traction causing flipping during punching, grind or replace the material discharge block, increase the strong pressure function, and adjust the material pressure.
9) Excessive pressure from the material discharge block, resulting in oversized punching, adjust the mold to reduce the depth of strong pressure.
10) Variations in mechanical properties of the stamping material (unstable strength and elongation), replace the material and control the quality of the feed.
11) Dimensional variation caused by cutting force on the material traction during stamping. Add a slope or arc to the end face of the male die blade to improve the force condition during cutting or add a guiding function at the material discharge position on the material discharge block.
7. What are the causes of material jamming during mold stamping, and what countermeasures should be taken?
The main causes of material jamming during stamping and the corresponding countermeasures are as follows:
1) Improper adjustment of feeding distance and material relaxation of the feeder, requiring readjustment.
2) Variations in feeding distance during production, requiring adjustment of the feeder's feeding distance.
3) Malfunction of the feeder, requiring adjustment and maintenance.
4) Material with an arc shape and excessive width, causing large burrs, requiring material replacement and control of feed quality.
5) Abnormal stamping causing blade bending, eliminating blade bending.
6) Insufficient diameter of the material guide hole, causing material pulling by the upper die, requiring repair of the guide hole.
7) Poor material discharge during bending or shearing, adjusting the strength of the material discharge spring, etc.
8) Improper setting of the material discharge function on the material guide plate, modifying the material guide plate to prevent material carryover.
9) Thin material causing warping during feeding, requiring the addition of upper and lower material pressure between the feeder and the mold, and the addition of upper and lower material extrusion safety switches.
10) Improper mold installation, significant deviation from the verticality of the feeder, requiring reinstallation of the mold.
8. What are the causes of blade bending in the material strip during mold stamping, and what countermeasures should be taken?
The main causes of blade bending in the material strip during mold stamping and the corresponding countermeasures are as follows:
1) Caused by stamping burrs (especially on the carrier), requiring repair of the material cutting edge.
2) When there are burrs on the material and no edge cutting on the mold, material replacement is required, and a cutting device should be added to the mold.
3) Improper depth of the punch press (too deep or too shallow), readjust the depth of the punch press.
4) Compression damage to the stamped part, presence of chips in the mold, requiring mold cleaning to address chip jumping and compression damage issues.
5) Excessive pressure in a specific area or local damage due to excessive pressure. Check and adjust the heights of various discharge and insert blocks of the female die, repair the damaged area.
6) Unreasonable mold design structure, can be adjusted using a bending mechanism.
9. What are the causes of blade breakage and edge chipping in the male die during mold stamping, and what countermeasures should be taken?
The main causes of blade breakage and edge chipping in the male die during mold stamping and the corresponding countermeasures are as follows:
1) Chip jumping causing material blockage and die jamming.
2) Improper feeding, half-cut material, pay attention to feeding, trim the material strip in a timely manner, and clean the mold promptly.
3) Insufficient strength of the male die, modify the design, increase the overall strength of the male die, reduce the dimensions of the straight edge section of the female die, pay attention to adding a slope or arc to the end face of the male die blade, and perform fine cutting after the main cutting.
4) The distance between the large and small male dies is too close, causing material traction during cutting and resulting in the breakage of the small male die. The length of the small male die can be shortened by more than one material thickness relative to the large male die.
5) Excessive sharp angles on the male and female dies, modify the design.
6) Small punching clearance, control the machining accuracy of the male and female dies or modify the design clearance, appropriately increase the punching clearance for fine cutting.
7) No stamping oil or the use of volatile stamping oil, adjust the oil drip amount or replace the oil type.
8) Uneven offset of the cutting clearance, interference between the male and female dies, check the accuracy of each forming part and adjust or replace them, control the machining accuracy.
9) Poor accuracy or wear of the material discharge block, losing the precision guiding function, require repair or replacement.
10) Wear of the guide components (pins), replace the guide components.
11) Improper installation of gaskets, requiring correction. Use as few gaskets as possible and use steel gaskets. The gasket under the female die should be placed below the cushion block.
10. What are the reasons for deformation or dimensional variation in products during continuous mold bending, and what countermeasures should be taken?
The reasons for deformation or dimensional variation in products during continuous mold bending and the corresponding countermeasures are as follows:
1) Worn guide pins, insufficient pin diameter, replace the guide pins.
2) Poor accuracy and wear in the bending guide area, regrind or replace.
3) Wear (compression damage) on the bending male and female dies, regrind or replace.
4) Insufficient clearance in the mold, check and correct.
5) Material slippage, lack of guiding function in the bending male and female dies, no preloading during bending. Modify the design, add guiding function and preloading capability.
6) Poor mold structure and design dimensions, modify the design dimensions, decompose the bending process, add bending and forming measures, etc.
7) Burrs on the stamped part causing poor bending, require repair of the material cutting edge.
8) Excessive use of gaskets in the bending area of the male and female dies, causing dimensional instability, adjust by using integral steel gaskets.
9) Variation in material thickness or mechanical properties, requiring material replacement and control of feed quality.
11. What are the reasons for uneven surface height in products during continuous mold production of multiple parts, and what countermeasures should be taken?
The main causes of uneven surface height in products and the corresponding countermeasures are as follows:
1) Burrs on the stamped part, require repair of the material cutting edge.
2) Compression damage to the stamped part, presence of chips in the mold, clean the mold to solve the issue of floating chips.
3) Wear or damage to the male and female dies (bending area), regrind or replace with new ones.
4) Material flipping during cutting, repair the cutting edge, adjust or add strong pressure function.
5) Wear and compression damage in the relevant material pressure area, check and perform maintenance or replacement.
6) Inconsistent tearing dimensions in the relevant tearing area, cutting edge wear, repair or replacement to ensure consistent tearing conditions.
7) Inconsistent pre-cutting depth in the relevant fragile area, wear or blade breakage in the male and female dies, check the condition of the pre-cutting male and female dies, perform maintenance or replacement.
8) Severe blade breakage or wear in the relevant embossing area, check the condition of the embossing male and female dies, perform maintenance or replacement.
9) Defects in mold design, modify the design, add height adjustment or additional forming stations.
12. What are the causes of improper maintenance in mold stamping, and what countermeasures should be taken?
The causes of improper maintenance in mold stamping and the corresponding countermeasures are as follows:
1) Lack of anti-misoperation function in the mold, negligence during mold assembly leading to misalignment in the wrong direction (referring to different workstations), modify the mold, add anti-misoperation function.
2) The inserted parts that have already been offset beyond the clearance are not restored to their original state. Use methods such as marking on the mold and compare it with the material strip after mold assembly for necessary inspection and confirmation, and make written records for future reference.
In stamping production, daily maintenance of the mold is crucial. This includes regular checks to ensure that the stamping machine and mold are in normal condition, such as oil supply for guiding parts and inspections before mounting the mold, checking the blade, confirming the tightness of various parts, etc. By doing so, many unexpected accidents can be avoided. When making mold repairs, it is essential to think before taking action and diligently keep records to accumulate experience.
13. What are the main reasons for mold repair in stamping?
There are many reasons for mold repair in production, mainly in the following aspects:
1) Natural wear of mold components, including wear of positioning and guiding parts, loosening of the mold handle, loosening of the male die on the fixed plate, increased clearance between the male and female dies, and dulling of the cutting edge.
2) Improper manufacturing process, mainly due to poor mold material, insufficient hardness after quenching, tapering of the male and female dies, inadequate precision and rigidity of the guiding parts, and eccentricity of the center axis after the installation of the male and female dies.
3) Improper stamping operation: the bottom surface of the mold is not parallel to the working table of the press, the working center of the press does not coincide with the working center of the mold, the male die enters the female die with excessive depth, and mold damage caused by press malfunctions or careless operation by the stamping operator.
14. What are the principles and steps for the maintenance of cutting dies?
The basic principles of mold maintenance are as follows:
1) The replaced parts must meet the technical requirements of the drawings.
2) The fitting accuracy, dimensional accuracy, and integrity of each part of the mold must be comprehensively checked.
3) After maintenance, the mold needs to be tested, adjusted, and accepted.
4) The maintenance time of the mold should meet the requirements of production.
The steps for mold maintenance are as follows:
1) Clean the mold before maintenance, remove oil stains and debris.
2) Check the dimensional accuracy and clearance fit of the reference positioning dimensions and various parts of the mold, record defects in a timely manner, and formulate repair plans.
3) Determine the parts that need to be disassembled, take them out, and repair them according to the repair plan.
4) Reassemble, adjust, and perform trial runs. If the original quality and precision cannot be restored, further adjustments and repairs are required.
15. What are the main aspects of temporary mold repair?
Temporary mold repair refers to the adjustment of the mold on the machine or the repair of only the damaged components without the need for disassembly. It mainly includes the following aspects:
1) Replacement using spare parts.
2) Grinding the worn cutting edges of the male and female dies using oil stones.
3) Replacing springs and tightening loose screws.
4) Tightening or welding loose male dies.
5) Adjusting the mold clearance and positioning devices.
6) Replacing the top material device.
16. What are the commonly used repair methods for cutting dies?
The commonly used repair methods for cutting dies are as follows:
1) Grinding the dull cutting edges of the male and female dies. One method is to use oil stones with kerosene or pneumatic grinding wheels. Another method is to use a surface grinder.
2) Repairing the increased clearance of the male and female dies. First, use a gauge block of appropriate size to check the clearance between the male and female dies. If the clearance is not significant, simply grind the cutting edge flat and then use an oil stone for finishing. If the clearance is too large, heat the dies with oxy-acetylene flame until they turn red, perform localized forging. For punch and die sets, tap the area around the female die cutting edge to ensure the size of the male die, and tap the male die for blanking dies to ensure the size of the female die. Once the dimensional uniformity is achieved, stop tapping but continue heating for a few minutes to eliminate internal stress. After cooling, use a press filing method to readjust the clearance and perform flame surface quenching.
3) Grinding the uneven clearance of the male and female dies. In addition to natural wear, there are two other situations:
a) Loose cylindrical pins lose their positioning ability, causing the male and female dies to be eccentric and resulting in uneven clearance. The cutting edges of the male and female dies should be aligned, then tightened with screws, and the original pin holes should be reamed by 0.1~0.2mm to create non-standard cylindrical pins.
b) Worn guiding devices reduce accuracy and fail to provide proper guidance, causing relative displacement of the male and female dies. The surface of the guide pillar should be chrome-plated, and the grinding method should be used to match the guide bush until the original clearance and accuracy level are restored.
4) Replacement of small punch and blanking male dies.
