1. Analysis of the causes of scrap metal stamping parts, from five angles: man, machine, material, method and environment.

A. The quality of raw materials for stamping is poor, such as uneven thickness and hardness, and inaccurate size of shearing or slitting;

B. Improper installation, adjustment and use of the stamping die, such as failure to attach the limit column, and the die is not completely closed during stamping production.

C. The punching operator fails to feed the punched strip correctly along the positioning or fails to ensure that the strip is fed at a certain gap;

D. Due to long-term use, the gap of the stamping die changes or its working parts and guiding parts are worn;

E. The fastening parts of the stamping die are loosened due to the long time of impact vibration, so that the installation positions of the stamping die are relatively changed;

F. The stamping operator neglects to operate according to the operating rules.

G. The quality management system is not perfect, or the quality inspector fails to conduct inspection on time, and the sampling inspection finds out the bad anomalies in time.

F. The precision of the punch machine is insufficient after years of disrepair, and the parallelism of the upper and lower tables decreases or the punching force decreases.

2. The main measures that stamping factories need to take to prevent metal stamping waste

A. Stamping raw materials must conform to the specified technical conditions (strictly check the specifications and brands of raw materials, and carry out laboratory tests on workpieces with high dimensional accuracy and surface quality when conditions permit. )

B. All links specified in the stamping process specification shall be strictly observed;

C. The press, stamping die and other tooling equipment used shall be guaranteed to work in normal working conditions;

D. Establish a strict inspection system in the production process. The first stamping parts must be fully inspected. Only after passing the inspection can they be put into production. At the same time, strengthen the inspection, and deal with accidents in time.

E. Adhere to the civilized production system, for example, the stamping workpiece and blank must be transported with appropriate station equipment, otherwise the surface of the workpiece will be crushed and scratched, which will affect the surface quality of stamping parts;

F. During the stamping process, the cleanliness of the die cavity should be ensured, and the orderly processed workpieces should be arranged in the workplace.

3. Causes of burr in blanking parts

A. The die blanking gap is too large, too small or uneven;

B, the cutting edge of the working part of the stamping die becomes dull;

C due to long-term vibration impact, the center lines of the male die and the female die change, and the axes do not coincide, resulting in single-sided burr.

Countermeasures of stamping factory

A. Ensure the machining accuracy and assembly quality of the punch, ensure the verticality of the punch and bear the lateral pressure, and ensure that the whole stamping die has sufficient rigidity;

B. When installing the punch, it is necessary to ensure the correct clearance of the punch and the punch are firmly installed on the die fixing plate, and the end faces of the upper and lower dies should be parallel to the workbench of the press.

C. It is required that the rigidity of the press is good, the elastic deformation is small, the accuracy of the track and the parallelism between the pad and the slider are high;

D it is required that the press should have sufficient blanking force.

Allowable burr height of shearing section of blanking parts

Blanking sheet thickness > 0.3 > 0.3-0.5 > 0.5-1.0 > 1.0-1.5 > 1.5-2.0.

The burr height of the new test die is ≤0.015 ≤0.02 ≤0.03 ≤0.04 ≤0.05.

The allowable burr height in production is ≤0.05 ≤0.08 ≤0.10 ≤0.13 ≤0.15.

4. Causes of warping deformation of blanking parts

There is a gap between the acting force and the reaction force, which does not produce a moment on a line. (Warping deformation occurs when the gap between male and female dies is too large and the cutting edge of female die has reverse taper, or when the contact area between ejector and workpiece is too small)

Measures:

A. the blanking gap should be selected reasonably;

B) In the mold structure, it is necessary to increase the plane contact between the pressing plate (or the holding plate) and the pressing plate with a certain pressure;

C. Check the cutting edge of the die. If there is reverse taper, the cutting edge of the die must be trimmed properly.

D. If the blanking force is increased due to uneven shearing force when the shape of the blanking part is complex and there are many internal holes, the strip material is pressed before blanking, or the high-precision guide post is used for alignment, or the high-precision press is used for blanking.

E. The plate should be leveled before blanking. If the warping deformation cannot be eliminated, the blanked workpiece can be leveled again through the leveling die.

F, regularly removing the stolen goods in the die cavity, lubricating the surface of the thin plate material, and arranging oil and gas holes on the die structure.

5. During blanking, the precision of the outer edge and inner hole of the blanking part decreases and the size changes.

Reason:

A. The positioning pin, retaining pin, etc. are changed or worn too much;

B. The operator's negligence causes the left, right, back and forth deviation when feeding;

C. The dimensional accuracy of the strip is low, and it is difficult to send it to the designated place because it is too narrow and too wide. When the strip moves back and forth in the guide plate, the inner hole of the punched workpiece deviates greatly from the front and back position of the shape.

6. Reasons for unqualified size and shape when stamping parts are bent.

A. the product is unqualified due to the rebound of materials.

Measures to reduce springback:

◆ Choose stamping materials with large elastic modulus and small yield point and stable mechanical properties;

◆. Add correction procedure, and use corrected bending instead of free bending;

◆. Before bending, the material should be annealed to soften the cold-working hardened material in advance and then bend to form;

◆. If the shape deformation occurs in the stamping process, it is difficult to eliminate it; Then the inclination of the punch and the die should be changed or trimmed, and the gap between the punch and the die should be equal to the minimum material thickness.

◆. Increase the contact area between the female die and the workpiece, and decrease the contact area between the male die and the workpiece.

◆. Use the method of "overcorrection" to reduce the impact of rebound.

B the locator is worn and deformed, which makes the strip positioning inaccurate, so a new locator must be replaced.

C. In the unguided bending die, when adjusting on the press, improper adjustment of the bottom dead center position of the press slider will also cause the shape and size of the bending part to be unqualified.

D the die pressing device fails or doesn't play a pressing role at all, so it is necessary to readjust the pressing force or replace the pressure spring to make it work normally.

Seven. Cracks occur in the bending part of the bending part (the internal stress in the bending deformation area exceeds the strength limit of the material).

A. Eliminate burrs on the outside of the bending zone, which will cause stress concentration in this zone.

◆ Reduce the bending deformation.

◆ Remove burrs in this area.

◆ The burr side is placed on the inner side of the bending area.

B when bending the workpiece, it is best to make the bending direction perpendicular to the fiber direction (rolling direction) of the material.

C. The bending radius should not be too small, and the radius of fillet should be increased as much as possible when the quality permits.

D the surface of the bent blank should be smooth and free from obvious bulges and scars.

E. Intermediate annealing process is adopted during bending to eliminate internal stress, and the softened bending rarely produces cracks.

F. When bending, the large metal stamping bending parts must be coated with lubricant to reduce the friction during bending.

VIII. Deviation of bending parts during bending

When the blank slides along the surface of the die in the bending process, it will be subjected to friction resistance. If the friction resistance between the two sides of the blank is quite different, the blank will deviate to the side with greater friction resistance.

Measures:

◆ Bending stamping parts with asymmetrical shapes are formed by symmetrical bending (one-sided bending parts are bent symmetrically in two pieces and then cut).

◆ An elastic material pressing device is added to the bending die, so that the blank can be pressed to prevent movement during bending.

◆ Adopt inner hole and shape positioning form to make its positioning accurate.

9. Causes and solutions of surface scratch of bending parts

A. When copper, aluminum alloy and other soft materials are pressed and bent continuously, metal particles or dross are easy to attach to the surface of the working part, which causes large scratches on the parts. At this time, the shape and lubricating oil of the working part should be carefully analyzed and studied so that it is best to avoid particles and dross and even scratches on the blanks.

B. When the bending direction is parallel to the rolling direction of the material, cracks will occur on the surface of the workpiece, which will reduce the surface quality of the stamping parts. When bending in more than two places, it is necessary to ensure that the bending direction has a certain angle with the rolling direction as much as possible.

C. When the burr surface is used as the outer surface for bending, the parts are prone to cracks and scratches; Therefore, the burr surface should be used as the inner surface of bending.