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Large summary of stamping problem solutions


Produce stamping waste

the reason
Inferior quality of raw materials;
Improper installation and use of the die;
The operator does not correctly feed the strip along the positioning or does not ensure that the strip is fed according to a certain gap; due to long-term use, the die has a gap change or wear of the working parts and the guiding parts;
The dies are relatively loose due to the impact vibration time, and the mounting positions of the dies are relatively changed. The operator's negligence does not operate according to the operating procedures.
Countermeasures
Raw materials must conform to the specified technical conditions;
Strict compliance with all aspects specified in the process specification;
The working equipment such as presses and dies used shall be guaranteed to work under normal working conditions;
A strict inspection system is established in the production process. The first part of the stamping parts must be inspected comprehensively. Only after the inspection is passed can the production be put into production, and the inspections should be strengthened. When accidents occur, they should be dealt with in time;
In the stamping process, the inside of the mold cavity should be cleaned, and the workpieces that have been arranged in the work place should be placed neatly.

Blanking burr
the reason
The punching gap is too large, too small or uneven;
The cutting edge of the working part of the die becomes dull;
The punch and the die are changed in the center line due to long-term vibration shock, and the axes do not coincide, resulting in a single-sided burr.
Countermeasures
Ensure the machining accuracy and assembly quality of the convex and concave molds, ensure the verticality of the punch and the side pressure and the entire die must have sufficient rigidity;
When installing the punch, the correct clearance of the male and female molds must be ensured and the convex and concave molds should be firmly fixed on the mold fixing plate, and the end faces of the upper and lower molds should be parallel to the work surface of the press;
The rigidity of the press is required to be good, the elastic deformation is small, the accuracy of the track and the parallelism of the pad and the slider are required to be high;
The press is required to have sufficient punching force.

Warping deformation of the blank
the reason
The gap force and the reaction force do not generate a moment on a line (the clearance between the convex and concave molds is too large and the concave edge of the concave mold has a reverse taper, or the contact area between the ejector and the workpiece is too small to cause warping deformation).
Countermeasures
The punching clearance should be chosen reasonably;
In the mold structure, the pressure plate (or the carrier plate) should be increased in surface contact with the pressure plate and have a certain pressure;
Check the die edge if it is found to have a reverse taper, the die edge must be trimmed properly;
If the shape of the blanking part is complicated and the shearing force is not uniform, the pressing force is increased, and the stripping material is pressed before punching or punched with a high-precision press;
The sheet should be leveled before blanking. If the warpage is still not eliminated, the punched workpiece can be leveled again through the leveling die;
The material in the mold cavity is periodically removed, the surface of the thin plate material is lubricated, and a gas passage hole is provided on the mold structure.

Unsatisfactory size and shape
the reason
The rebound of the material caused the product to fail;
The positioner is subject to wear and deformation, and the strip is not positioned properly, and a new positioner must be replaced;
In the unguided bending die, when the press is adjusted on the press, the position of the bottom dead center of the press slider is improperly adjusted, and the shape and size of the bent piece are also unqualified;
If the die pressing device of the mold fails or does not work at all, the pressing force must be readjusted or the pressure spring must be replaced to make it work normally.
Countermeasures
Selecting a stamping material with a stable mechanical modulus and a small yield point and a relatively stable mechanical property;
Increase the correction process and use corrective bending instead of free bending;
Before bending, the material is annealed, and the cold work hardening material is softened before being bent and formed;
If the shape deformation occurs during the stamping process and it is difficult to eliminate; the slope of the punch and the die should be replaced or trimmed, and the gap between the punch and the die should be equal to the minimum material thickness;
Increasing the contact area between the die and the workpiece, and reducing the contact area between the punch and the workpiece;

Bending offset
the reason
When the blank slides along the surface of the die during bending, it will be subjected to frictional resistance. If the frictional resistance between the two sides of the blank is large, the blank will be offset to the side with greater frictional resistance.
Countermeasures
Asymmetrically shaped curved members are formed by symmetrical bending (single-sided curved parts are cut by two pieces of symmetrical bending and then cut);
Adding an elastic pressing device to the bending mold so as to be able to press the blank during bending to prevent movement;
The inner hole and shape positioning form are used to make the positioning accurate.

Surface scratches on parts
Causes and countermeasures
When a soft material such as copper or aluminum alloy is subjected to continuous bending, metal particles or dross are easily attached to the surface of the working portion, causing large scratches on the workpiece to cause scratches;
When the bending direction is parallel to the rolling direction of the material, cracks are generated on the surface of the workpiece, which deteriorates the surface quality of the workpiece. When bending at more than two locations, the bending direction should be as close as possible to the rolling direction;
The corner radius of the die is too small, and there are impact marks on the bent portion. Polishing the die and increasing the radius of the die corner can avoid scratching of the bent piece;
The gap between the convex and concave molds should not be too small, and the gap is too small to cause thinning and scratching. Always check the change of the gap of the mold during the stamping process;
When the depth of the punch into the die is too large, the surface of the part will be scratched. Therefore, in the case of ensuring that it is not affected by the rebound, the depth of the punch into the die should be appropriately reduced;

Thinned part
Countermeasures
The bending radius is too small relative to the thickness of the plate (r/t>3 right angle bending) generally increases the bending radius;
Multi-angle bending makes the bending part thinner, and in order to reduce the thinning, the single-angle multi-step bending method is adopted as much as possible;
When a sharp-angled punch is used, the punch enters the die too deeply to significantly reduce the thickness of the bent portion.
Stretch wrinkle
the reason
The crimping force at the flange portion is too small to resist excessive tangential compressive stress; it causes tangential deformation, and thus wrinkles are formed after losing stability. Thinner materials are also easier to form wrinkles.
Countermeasures
Increase the blanking force of the binder ring and increase the thickness of the material appropriately.

Hole position changes
the reason
The position of the hole is not the same size (bending is thinned);
The holes are not concentric (the bending height is not enough, the blank slips, rebounds, and the undulations appear on the curved plane);
The portion where the bending line and the center line of the two holes are not parallel and the bending height is less than the minimum bending height exhibits an outward opening shape after bending;
The hole near the bending line is prone to deformation.
Countermeasures
Measures for different reasons for the hole:
Make sure the right and left bending height is correct;
Correct the worn positioning pin and positioning plate;
Reducing the rebound to ensure the parallelism and flatness of the two curved faces;
Change the routing, first bend and correct and punch.

Rugged edges
the reason
The blank is not centered with the convex and concave mold or the material thickness is not uniform, and the radius of the concave corner of the concave mold and the gap between the concave and convex mold are not uniform (the radius of the concave corner of the concave mold is too large, and the crimping ring is separated from the crimping ring in the final stage of drawing, so that the rounded corner has not been crossed yet The material crimping ring is pressed less than wrinkled and then pulled into the die to form a rim wrinkle.
Countermeasures
The die is repositioned, and the die radius and the die gap are corrected to make the size uniform and then put into production (reducing the radius of the die radius or using the curved bead ring device to eliminate wrinkles).

Waist wrinkling
the reason
At the beginning of the drawing, most of the material is in a suspended state, and the blanking force is too small, the radius of the die corner is too large or too much lubricant is used. The radial tensile stress is made small so that the material loses stability and wrinkles under the action of tangential compressive stress.
Countermeasures
Increase the blank holder force or use a calendering rib structure to reduce the radius of the die corner or slightly increase the thickness of the material.

The wall is cracked
the reason
The tensile stress of the material subjected to deep drawing is too large;
The radius of the die fillet is too small;
Poor lubrication;
The plasticity of raw materials is poor.
Countermeasures
Reduce the blank holder force;
Increase the radius of the concave die;
Proper use of lubricants;

Use a better material or increase the annealing process.



Deshengrui Machinery is a professional CNC manufacturing and Sheet metal fabrication company, including CNC machining services, CNC turning service, CNC milling services, CNC drilling services, laser cutting services, stamping services, Die casting service, iron casting service and Steel Forging service.


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