Hardware mold maintenance experience
1. Maintenance essentials of molds The maintenance of continuous molds must be careful, patient, and step by step, and not blindly engaged. When repairing the mold due to failure, it is necessary to attach a material belt to facilitate the inquiry of the problem. Open the mold, take care of the belt, check the condition of the mold, confirm the cause of the failure, find out the problem, then clean the mold and dismantle it. When demoulding, the force should be uniform, aiming at the stripper spring between the fixed plate and stripper plate.
1. Key points of mold maintenance:
The maintenance of continuous die must be careful, patient, step by step, and not blindly engaged. When repairing the mold due to failure, it is necessary to attach a material belt to facilitate the inquiry of the problem. Open the mold, take care of the belt, check the condition of the mold, confirm the cause of the failure, find out the problem, then clean the mold and dismantle it. The stress should be even when the formwork is removed. For the die structure where the stripper spring is between the fixed plate and the stripper plate, and the stripper spring directly leans against the inner guide post, the stripper plate should be removed to ensure unbalanced ejection, and the inclination of the stripper plate may lead to the fracture of the punch in the die.
1. Maintenance of punch and die:
Pay attention to the original state of the die when disassembling the convex and concave die, so as to recycle it when assembling the die later. If there is a washer or displacement element, the thickness of the washer should be engraved on the part and recorded. When replacing the punch, the stripper block and the female die should be inserted as smoothly as possible, and the gap between the stripper block and the female die should be inserted as evenly as possible when replacing the female die. In view of the fact that the punch becomes shorter after grinding and the padding needs to reach the required length, it should be checked whether the effective length of the punch is enough. To replace the broken punch, it is necessary to find out the reason, and at the same time, check whether the corresponding female die has broken edges and needs grinding. When assembling the punch, check whether there is enough clearance between the punch and the fixed block or the fixed plate, and if there is a pressing block, check whether there is residual movement. The assembled female die should be placed horizontally, and then placed on the surface of the female die with a flat iron block and knocked in place with a copper rod. Do not use force obliquely, and the bottom of the female die should be chamfered. After installation, check whether the mold surface is flush with the mold surface. After the punch, die and die core are assembled, check the guard band, whether all parts are installed incorrectly or backwards, whether the die and die pad are installed backwards, whether the blanking hole is blocked, whether the newly replaced parts need to be stolen, whether enough materials are needed, and whether the parts that need to be locked are locked. Pay attention to the locking confirmation of the demoulding screw. When locking, cross lock with balanced force from inside to outside. Don't lock one screw first and then the other screw, so as not to cause the stripper to tilt, which will lead to the fracture of the punch or reduce the accuracy of the die.
2. Maintenance of stripper:
Balance with two screwdrivers, and then balance the take-out force with both hands, and you can take off the stripper plate. When it is difficult to disassemble, check whether the inside of the mold is clean, whether the locking screws are completely disassembled, and whether the mold is damaged due to material jamming. Find out the reason and deal with it accordingly. Never dispose of it blindly. When assembling the stripper plate, first clean the punch and stripper plate, add lubricating oil to the guide post and the introduction of the punch, put them in smoothly, press them in place with both hands, and repeat several times. If it is too tight, find out the reason (whether the guide post and guide sleeve are guided normally, whether each part is damaged, whether the new punch can pass through the stripper smoothly and whether the position is correct), and then do the corresponding treatment after finding out the reason. If there is a press block on the fixing plate, check whether the demoulding on the demoulding back plate is sufficient. The material contact surface between stripper plate and female die is depressed due to long-term stamping (the material clamping gap between stripper plate and female die is generally less than the material thickness of 0.03-0.05mm). Serious indentation will affect the pressing accuracy of materials, resulting in abnormal and unstable product size, so it is necessary to repair or re-grind the stripper block and stripper plate. Check the accuracy of contour sleeves. If it is not the same height, the stripper will tilt, and its precise guidance and stable spring pressing function will be destroyed, so it must be maintained.
3. Inspection of guide parts:
What is the fit clearance between the guide post and the guide sleeve, whether there are traces of burn or wear, and whether the oil supply state of the mold guide is normal, all should be checked. The wear and tear of guide parts and the destruction of precision reduce the precision of the mold, and all parts of the mold will have problems, so proper maintenance and regular replacement are needed. Check the accuracy of the material guide. If the guide tip (positive nail) is worn, it will lose the correct belt alignment accuracy and function and must be replaced. Check the condition of springs (demoulding springs and ejection springs, etc.). ) See if it is broken, or if it is not broken after long-term use, it has lost its original strength because of fatigue, so it must be maintained and replaced regularly, otherwise it will cause mold damage or unsmooth production.
4. Adjustment of mold clearance:
The locating hole of the die core is worn due to the frequent repeated combination of the die core, which leads to a large gap (looseness after assembly) or uneven gap (positioning deviation) after assembly, which will cause the cross-section shape to deteriorate after stamping, and the punch is easy to break, resulting in burrs and so on. Appropriate clearance adjustment can be made by checking the cross section after stamping. When the gap is small, there are few sections, and when the gap is large, there are many sections and large burrs. A reasonable clearance is obtained by moving the components. After adjustment, it is necessary to make corresponding records, or mark the edge of the mold for subsequent maintenance. In daily production, we should pay attention to the collection and preservation of raw material belts under the condition that the molds are in good condition. If the subsequent production is not smooth or the molds have variation, it can be used as a reference for mold maintenance. In addition, whether the auxiliary system such as ejector pin is worn, whether the material can be ejected, and whether the guide pin (nail) and bushing are worn should be checked and maintained.
2. Causes and countermeasures of common mold failures
In the stamping production of progressive die, it is necessary to analyze the bad stamping phenomenon and take effective countermeasures to solve the problem fundamentally, so as to reduce the production cost and realize smooth production. The following are the causes and countermeasures of common bad stamping phenomena in production, for the reference of mold maintenance personnel.
1. Flash of stamping parts.
(1) Reason: A. Wear of knife edge; B, the effect is not obvious after the gap is too large; C, knife edge collapse angle; D, the gap is unreasonable up and down offset or loose; E, the mold is staggered up and down.
(2) Countermeasures: A, training the knife edge; B, controlling the machining accuracy of the convex-concave die or modifying the design gap; C, training the knife edge; D, adjusting the blanking gap to confirm the wear of the template cavity or the machining accuracy of the molded part; E, replace the guide rail or reassemble the mold.
2. Jumping chip crush injury
(1) reason: a, the gap is too big; B, improper feeding; C, stamping oil droplets too fast, oil sticky; D, the mold does not demagnetize; E, the punch is worn, and debris is pressed on the punch; F, the punch is too short, and the length of the insert die is insufficient; G, the material is hard and the stamping shape is simple; Emergency measures.
(2) Countermeasures: A, control the machining accuracy of punch and die or modify the design gap; B, when it is delivered to a proper position, trim the material belt in time and clean the mold; C, controlling the oil quantity of the punched oil drop or changing the oil type to reduce the viscosity; D, demagnetization must be carried out after the training (pay more attention to strike while the iron is hot); E, researching the punch blade; F, adjust that length of the edge of the male die entering the female die; G. change materials and modify design. The edge of the punch is inserted into the end face to eject or trim the slope or arc (pay attention to the direction). Reduce the joint area between the end face of the punch blade and the chip; H, reduce the sharpness of the die cutting edge, reduce the grinding amount of the die cutting edge, increase the roughness (coating) of the surface of the straight edge of the die, and use a vacuum cleaner to absorb waste. Reduce the impact speed and chip bounce.
3. Debris blockage
(1) Reason: A. The leakage hole is too small; B, leakage hole is too large, debris rolling; C, blade wear, burr is bigger; D, stamping oil droplets too fast, oil sticky; E, the surface of the straight edge of the female die is rough, and powder is sintered and attached to the edge; F, the material is soft; Emergency measures.
(2) Countermeasures: A, modify the leakage hole; B. modify the leakage hole; C, trimming the knife edge; D, control the amount of oil dripping and change the types of oil; E, surface treatment, polishing, pay attention to reduce the surface roughness during processing; Change the material, f, modify the blanking gap; G, repair the end face of the punch blade into an inclined plane or an arc (pay attention to the direction), and use a vacuum cleaner to aerate the blanking hole of the backing plate.
4. The change of blanking offset size
(1) Reason: A. The edge of the convex-concave die is worn, resulting in burrs (the outer shape is too large and the inner hole is too small); B, improper design size and clearance, poor machining accuracy; C, that punch and the die insert at the punch position are offset, and the gap is uneven; D, guide pin wear, pin diameter is insufficient; E, guide rail wear; F, feeder feeding distance, pressure, relax improper adjustment; G, improper adjustment of clamping height; H, the material pressure of the stripping insert is horizontally worn, and there is no material pressure (strong pressure) function (small punching caused by pulling and turning); First, the discharging insert is pressed too deeply and the punching hole is too big; J, mechanical properties variation of stamping materials (unstable strength elongation); K, punching, punching force on the material traction, resulting in dimensional changes.
(2) Countermeasures: A, training the knife edge; B, modify the design and control the machining accuracy; C, adjusting the position accuracy and punching the gap; D, replacing the guide pin; E, replace the guide post and guide sleeve; F. readjust the feeder; G, readjusting the clamping height; H, grinding or replacing the demoulding insert, increasing the pressing function and adjusting the pressing material; Reduce the depth of strong pressure; J, refuelling, and controlling feed quality; K, the punch blade end face slope or arc repair (pay attention to the direction), to improve the stress situation during stamping. When allowed, the guide function is added to the unloading insert at the unloading position.
Step 5: filler
(1) Reason: A. The feeding distance, material pressing and relaxation of the feeder are not properly adjusted; B, feed distance changes in production; C, feeder failure; D, the material is arc-shaped, with out-of-tolerance width and large burr; E, abnormal die stamping, resulting in sickle bending; F, the hole diameter of the guide material is insufficient, and the upper die pulls the material; G, stripping up and down at the bending or tearing cutting position; H, guide plate discharging function is set improperly, with material belt; Me, the material is thin and the middle is upturned; J, improper mold erection, the verticality deviation of the feeder is large.
(2) Countermeasures: A, readjust; B, readjust; C. adjustment and maintenance; D, changing raw materials and controlling feed quality; E, eliminating the sickle bend of the material belt; F, research and develop the punch and die for punching the positive hole; G, adjust the strength of the demoulding spring, etc. H, modify the guide material to prevent the belt material; 1, adding upper and lower pressing materials between a feeder and a die, and adding an upper and lower extrusion safety switch; J, reset the mold.
This material is bent with a sickle.
(1) Reason: A. Stamping burr (especially on the carrier); B, raw edges of materials, and no trimming of the mold; C, improper drilling depth (too deep or too shallow); D, the stamping parts are crushed, and there are wastes in the mold; E, local pressure material is too deep or pressure to local damage; F, mold design.
(2) Countermeasures: A, study the cutting edge; B, replacing materials and adding an edge trimming device on the die; C, readjusting the depth of the punching machine; D, cleaning the mold to solve the problem of chip jumping and breaking; E, check and adjust the height and size of each stripper plate and die insert, and study the damaged position; F, adopt the whole bending mechanism to adjust.
7. Punch fracture and edge collapse
(1) Reason: A. Chip jumping, chip blocking, die sticking, etc. B, improper feeding, cutting half material; C, insufficient punching power; D, the big punch and the small punch are too close, and the material is pulled when punching, which leads to the fracture of the small punch; E, punch and die local too sharp; F, the blanking gap is too small; G. There is no stamping oil or the used stamping oil is highly volatile; H, uneven offset of blanking gap, interference between punch and die; I. The precision of the demoulding insert is poor or worn, and the precision guiding function is lost; J, mold guide is not allowed, wear; K. Improper material selection and hardness of convex and concave dies; I, guide (pin) wear; M, gasket added improperly.
(2) Countermeasures: A. Solve the problems of chip jumping, chip blocking and die sticking. B, pay attention to feeding, trim the material belt in time, and clean the mold in time; C, modify the design, increase the overall strength of the punch, shorten the size of the straight edge of the female die, pay attention to the slope or arc of the edge end face of the punch, and the small part will be cut back; D, the length of the small punch is shortened by more than one material thickness relative to the large punch; E, modify the design; F. Control the machining accuracy of punch and die or modify the design clearance, and appropriately increase the stamping clearance of fine parts; G, adjusting the oil quantity of the stamping oil drop or replacing the oil type; H, check the accuracy of each molded part, and adjust or replace it to control the machining accuracy; I. training or replacement; J, replace the guide post and guide sleeve, and pay attention to daily maintenance; K, change the materials used and use appropriate hardness; I. replace the guide; M, correction, the number of gaskets should be as small as possible, and steel pads should be used. The gaskets under the female die should be placed under the block.
8. Dimensional change of bending deformation
(1) Reason: A. The guide pin is worn and the pin diameter is insufficient; B, bending guide part accuracy is poor, wear; C, bending punch wear (pressure loss); D, insufficient molds; E, the material slips, the bending punch and die have no guiding function, and no preloading is applied during bending; F, poor mold structure and design size; G, stamping parts burr lead to poor bending; H, more gaskets are added to the punch and die at the bend, resulting in unstable dimensions; I, material thickness size change; Mechanical shape and energy change of materials.
(1) Countermeasures: A. Replace the guide pin; B, re-grinding or replacement; C. regrinding or replacement; D, check and correct; E, modify the design, increase the guidance and preloading function; F, modify the design size, decompose bending, increase bending shaping, etc. G, researching the cutting edge of the blanking position; H, when adjusting, use the integral steel pad; First, change raw materials and control feed quality; J, change raw materials and control feed quality.
9. Stamping height (when multiple parts are in one mold)
(2) Reason: A, burr of stamping parts; B, the stamping parts are crushed, and there is waste in the mold; C, punch, die (bending position) pressure loss or damage; D, turning materials when punching and shearing; E. Wear and pressure loss of relevant compression parts; F, related tearing and cutting positions are inconsistent in tearing and cutting dimensions, and the blade is worn; G. The pre-cutting depth of relevant fragile parts is inconsistent, and the convex and concave dies are worn or cracked; H, the convex and concave dies of the relevant protruding parts have broken edges or are seriously worn; First, mold design defects.
(2) Countermeasures: A, study the cutting edge of blanking position; B, cleaning the mold to solve the floating problem of the chip; C. Re-study or replace new parts; D, learn the punching knife edge, and adjust or increase the pressing function; E, inspection, maintenance or replacement; F, maintenance or replacement, to ensure that the tearing and cutting conditions are consistent; G, check the state of the pre-cutting punch and die, and carry out maintenance or replacement; H, check the state of the punch and die, and implement maintenance or replacement; Modify the design, increase the height adjustment or increase the molding station.
10. Improper maintenance
(1) Reason: A. The mold has no foolproof function, and the assembly mold is negligent, resulting in wrong direction and dislocation (referring to different stations); B. Inserts that deviate from the gap are not restored.
(2) Countermeasures: A, modify the mold to increase the fool-proof function; B, mark the mold, etc. , and after assembling the mold, make necessary inspection and confirmation of the protective belt, and make a written record for inquiry.
In stamping production, the daily maintenance of the die is very important, that is, daily attention is paid to checking whether the punch and die are in normal state, such as refueling the supply guide rail of stamping oil. Many unexpected accidents can be avoided by checking the mold before it is put on the machine, checking the blade and confirming the locking of each part. You must think twice before you repair the mold, make records carefully and accumulate experience.