15 Every Metal Stamping Mold Maintenance Methods Should Know About

Mold installation and adjustment

Installation and adjustment of punching molds must be made with special care. Because punching molds, especially large and medium-sized ones, are costly and difficult to move in minute amounts with great weight, personal safety should always be given top priority. For molds without the limit device, a wooden board should be added between the upper and lower molds. After the punching table is cleaned, the mold to be tested in the closed state is placed on the table in the right position.

Adjust the slider linkage and move the mold to ensure that the mold handle is aligned with the mold handle hole and reaches the proper height before moving the mold on the table to the lower dead center and a position 10-15mm greater than the mold closing height. Generally, the lower mold is fixed first (not tightened), and then the upper mold is fixed (tightened), and the T-bolts of the platen should be tightened with a suitable torque wrench (lower mold) to ensure a consistent and ideal preload clamping force for the same screw. This can effectively prevent the pre-tightening force from being too large or too small or the pre-tightening force of the same thread from being unequal due to physical strength, gender, and handedness errors, which may cause the upper and lower molds to be shifted, the gap to be changed, and the edge to be peeled during the stamping process.

Before the mold test, fully lubricate the mold and prepare the material for normal production. Start the mold 3 to 5 times in empty stroke to confirm the mold is operating normally before test punching. Adjust and control the depth of the convex mold into the concave mold, check and verify the performance and operational flexibility of the mold guiding, feeding, pushing, and unloading, side pressure, and spring pressure mechanisms and devices, and then make appropriate adjustments to achieve the best technical condition. After passing the test punching, we will test punch 10, 15, and 30 pieces for re-inspection. After scribing inspection, punching surface, and burr inspection, all dimensions and shape accuracy are by the drawing requirements before delivery to production.

Attention should be paid to the punch before use

①Clean the punch with a clean rag.

②Check if there are scratches and dents on the surface. If there are, remove them with an oil stone.

③Take oil to prevent rust in time.

④Be is careful not to have any tilt when installing the punch, and use a soft material tool like a nylon hammer to knock it gently into place.


Jumping scrap

Large mold clearance, short convex mold, the influence of material (hardness, brittleness), too high stamping speed, adhesion caused by too sticky stamping oil or too fast oil drops, scraps dispersed by stamping vibration, vacuum adsorption and low demagnetization of mold core can cause scraps to be brought to the mold surface.

①The sharpness of the edge. The larger the rounded angle of the edge, the easier it is to cause the rebound of the scrap, for the material is thin stainless steel, etc. can be used oblique edge.

②For the more regular scrap, you can increase the complexity of the scrap or add a polyurethane top bar on the punch to prevent jumping scrap and increase the scoring on the side of the concave mold edge.

③The clearance of the mold is reasonable. Unreasonable mold clearance, easy to cause scrap bounce, for small diameter hole clearance is reduced by 10%, diameter greater than 50.00 mm, the gap is enlarged.

④Increase the depth of mold entry. For each station mold stamping, the requirement of mold entry is certain, small mold entry, easy to cause scrap rebound.

⑤Whether there is oil on the surface of the material being processed.

⑥Adjust the stamping speed and stamping oil concentration.

⑦Adopt vacuum adsorption.

⑧ Demagnetize the punch, insert, and material.

Stamping burr

①mold clearance is too large or uneven; readjust the mold clearance.

②Improper mold material and heat treatment, produce concave mold chamfering cone or edge not sharp, should be reasonable material selection, mold working part material with carbide, reasonable heat treatment method. mold Daren Weixin:Xujudaren

③Stamping wear, grinding punch, or inserts.

④The convex mold is too deep into the concave mold; adjust the depth of the convex mold into the concave mold.

 ⑤ guide structure is not precise or improper operation, overhaul the guide pillar guide bush and punch guiding accuracy in the mold, and standardize the operation of the punching machine.

Crushing and scratching

①The material belt or mold has oil and waste chips, resulting in a pressure injury. It is necessary to wipe the oil and install an automatic air gun to remove the waste chips.

②The surface is not smooth, and the surface finish of the mold should be improved.

③The surface hardness of the parts is not enough; the surface needs to be treated with chrome plating, carburizing, boron penetration, etc.

④Material strain and destabilization, reduce lubrication, increase compressive stress, adjust spring force.

⑤ operation of the product scraped to the mold positioning or other places caused by scratching, need to modify or reduce the mold positioning, educate the operator to work gently hold and place.

Workpiece bending after the outer surface abrasion

① raw material surface is not smooth, clean, school plain material.

② Forming into the block with waste, clear the waste chips between the block.

③ molding block is not smooth; the molding block plating, and polishing, improve the convex and concave mold finish.

④The bending radius R of the convex mold is too small; increase the bending radius of the convex mold

⑤ Mold bending gap is too small; adjust the upper and lower mold bending gap.

⑥The concave mold forming block is equipped with roller forming.

Leakage of punching hole

In case of leakage of punching holes, there are general factors such as punch breakage not found, leakage of punching after mold repair, and sinking of punch, etc. After mold repair, confirm the first piece and compare it with the sample to check whether there is any leakage.

Abnormal stripping

①The stripping plate is too tight with the convex mold; the stripping plate is tilted; the height of the contour screw is not uniform or other improper stripping parts; the stripping parts should be repaired, and the stripping screw should adopt the combination of the casing and hexagonal screw.

②mold clearance is small; the punch needs a large release force when detaching from the material, resulting in the punch being bitten by the material; the lower mold clearance needs to be increased.

③The concave mold has an inverted cone, so the concave mold should be trimmed.

④The concave mold drop hole is not aligned with the lower mold holder leakage hole; fix the leakage hole.

⑤ Check the condition of the processed material. The material is dirty and attached to the mold, so the punch can not be processed because the material is bitten. The warped and deformed material will clamp the punch after punch. If the warped and deformed material is found, it needs to be made flat and then processed.

The edge of the punch and lower mold should be sharpened in time. A sharp edge of the mold can process a beautiful cutting surface, and a blunt edge requires extra punching pressure. The roughness of the workpiece section produces great resistance, causing the punch to be bitten by the material.

⑦ Appropriate use of beveled edge punch.

⑧Minimize wear and improve lubrication conditions to lubricate the plate and punch.

⑨Insufficient spring or rubber elasticity or fatigue loss, replace the spring in time.

⑩The clearance between the guide pillar and guide bush is too large, rework or replace the guide pillar and guide bush.

◎ Parallelism error accumulation, resharpen the assembly.

The hole on the push-piece block is not perpendicular, so the small convex mold is offset, repaired, or replaced the push-piece block.

The mold or guide pillar installation is not vertical; reassemble it to ensure verticality.

Bending edge is not straight, and the size is not stable

①Increase the pressure line or pre-bending process
②Insufficient material pressing force, increased pressing force
③ convex and concave mold corners wear asymmetric or bending uneven force; adjust the gap between the convex and concave mold to make it uniform; polishing convex and concave mold corner
④ height size can not be less than the minimum limit size

Bending surface extrusion material thinning

① concave mold angle is too small, increase the radius of the concave mold angle

②The gap between the convex and concave mold is too small; correct the gap between the convex and concave mold

The bottom of the concave part is not flat

①The material itself is not flat; need to level the material

②The contact area between the top plate and material is small, or the full material force is not enough; we need to adjust the top material device and increase the maximum material force.

③No ejector device in the concave mold; should increase the ejector device or correction

④Add shaping process

Stainless steel flanging deformation

In the manufacture of flanging before applying high-quality forming lubricant to the material, which can make the material better separated from the mold, forming smoothly in the lower mold surface movement. This gives the material a better opportunity to distribute the stresses generated by bending and stretching, preventing deformation on the edge of the formed flanged hole and wear on the bottom of the flanged hole.

Material distortion

Punching a large number of holes in the material results in the poor flatness of the material, probably due to the accumulation of punching stresses. When punching a hole, the material around the hole is stretched downward, which increases the tensile stress on the sheet’s upper surface. The downward punching motion also causes an increase in compressive stress on the lower surface of the sheet. For a small number of holes, the result is not obvious. Still, as the number of holes punched increases, the tensile and compressive stresses increase exponentially until the material is deformed.

One way to eliminate this deformation is to punch every other hole and then return to punch the remaining holes. This produces the same stresses in the sheet but dissipates the tensile/compressive stresses that accumulate as a result of punching one after the other in the same direction. This also allows the first batch of holes to share the partial deformation effect of the second batch of holes.

Severe mold wear

①Replace worn mold guide components and punches in time.

②Check whether the mold clearance is unreasonable (small) and increases the lower mold clearance.

③Try to reduce the wear, improve the lubrication condition and lubricate the plate and punch. The amount of oil and the number of oiling depends on the conditions of the processed material. For materials without rust and scale, such as cold-rolled steel plate and corrosion-resistant steel plate, oil the mold with oiling points for the guide bush, oiling port, lower mold, etc. Use light machine oil for the oil. For materials with rust scale, the rust micro-powder will be sucked between the punch and guide bush during processing to produce dirt, making the punch unable to slide freely in the guide bush. In this case, if oil, it will make the rust scale easier to stain, so when punching this material, instead, wipe the oil clean, decompose it once a month, use steam (molds) oil to remove the dirt from the punch and lower mold, and wipe it clean again before reassembling. This will ensure that the mold has good lubrication performance.

④Improper sharpening methods cause annealing of the mold and aggravate wear. Soft abrasive grinding wheels should be used, a small amount of knife eating, sufficient coolant, and frequent cleaning of the grinding wheels.

Prevent stamping noise

The punching machine is the most critical and necessary equipment for the sheet metal processing industry. The maximum value of this noise can reach 125dB(A), which greatly exceeds the national standard of 85dB(A) and the following noise index requirements, thus causing extremely serious harm and pollution to the operating workers and the surrounding environment (such as offices, residential areas, conference rooms, etc.). Effective management of noise has become an urgent problem. Especially the implementation of China’s first “Noise Law,” the increasing scale of environmental protection industrialization has accelerated the urgency of this noise management.

From the punching machine noise source and mold structure, to reduce noise has to pay attention to the following points.

① Pay attention to mold maintenance, clean, and keep the edge sharp.

②The shape of the mold edge, the number, material and punching line length, the mold edge, and parts contact surface are not too large; the punch to do oblique blade step punching so that the mold in different positions cut into the depth of different, the whole process to achieve a real cut off, rather than synchronous squeeze off.

③The mold edge must be perpendicular to the installation surface, and the gap between the convex and concave mold edges should be reasonable. When unloading is difficult, the lower mold gap can be increased, the unloading force can be increased, and the unloading plate with a soft surface can be used.

④The precision of the fit between each working template, processing some exhaust slots.

⑤Stopping plate is changed to a small piece of spelling, and the discharging plate and lower template are changed to insert type to reduce the slamming area.

⑥Spring top source of the stripper plate is changed to a T-type top bar; the spring is installed in the upper mold seat, contour sleeve, and top bar are used to ensure that the stripper plate still has a certain amount of free movement when the mold is open.

⑦ Keep good lubrication, no interference in the mold, smooth.

⑧The surface of the upper and lower mold holder is padded with an aluminum plate to make a buffer for punching force.

⑨After the mold is adjusted, add a sound insulation cover or sponge plate on the punching machine for soundproof treatment.

⑩Improve the precision of the punching machine and reduce the structure noise. Install buffer vibration and noise reduction cylinders on the working table, gears with helical teeth to enhance lubrication and gear covers, and mufflers in the pneumatic system.


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