Common inspection methods and defect evaluation of stamping parts

1. Touch inspection

Wipe the surface of the outer covering with clean gauze. The inspector wears touch gloves along the stamped part longitudinally against the surface of the stamped part, and this method of inspection depends on the inspector's experience. If necessary, the detected suspicious area can be sanded with a stone and verified, but this method is an effective and rapid inspection method.

2. Oil stone grinding

2.1. First wipe the surface of the outer covering with clean gauze, then polish it with an oil stone (20×20×100mm or larger), and polish it with a relatively small oil stone (for example: 8×100mm semicircular oil stone) in places with arcs and places that are difficult to reach.

2.2. The choice of oil stone particle size depends on the surface condition (such as roughness, galvanizing, etc.). It is recommended to use fine-grained stones. The direction of stone grinding is basically carried out along the longitudinal direction, and it fits the surface of the stamping parts well, and some special places can also supplement the horizontal grinding.

3. Grinding of flexible gauze

Wipe the surface of the outer covering with clean gauze. Grinding longitudinally to the entire surface with a flexible sand mesh against the surface of the stamping part, any pittings and indentations will be easily detected.

4. Oiling inspection

Wipe the surface of the outer covering with clean gauze. A clean brush is then used to evenly apply the oil to the entire outer surface of the stamped part in the same direction. Put the oiled stamping parts under strong light for inspection, and it is recommended to put the stamping parts vertically on the body position. With this method, it is easy to find tiny pitting, deflated ponds, and ripples on the stamping parts.

5. Visual inspection

Visual inspection is mainly used to find cosmetic anomalies and macroscopic defects in stamped parts.

6. Inspection tool detection

Put the stamping parts into the gauge, and test the stamping parts according to the operation requirements of the gauge manual.

2. Criteria for evaluating defects in stamping parts

1. Cracking

Test Method: Visual Evaluation Criteria:

Class A defects: cracks that can be noticed by untrained users, stamped parts that are unacceptable to the user, and must be frozen immediately after discovery.

Class B defects: visible and identifiable microcracks, such defects stamping parts are not acceptable in areas I and II., and repair welding rework is allowed in other areas, but the repair parts are not easy to detect by customers and must meet the repair standards of stamping parts.

Class C defects: Defects that are ambiguous and determined after careful inspection, and the custom stamping parts with such defects are repaired and repaired in Zone II, III and IV, but the repair parts are not easy for customers to notice and must meet the repair standards of stamping parts.

2. Strains, coarse grains, and dark wounds

Test Method: Visual Evaluation Criteria:

Class A defects: strains, coarse grains, dark wounds that can be noticed by untrained users, stamped parts with such defects are unacceptable to the user, and must be frozen immediately after discovery.

Class B defects: visible and identifiable minor strains, coarse grains, dark scratches, stamped parts of which are acceptable in Zone IV.

Class C defects: minor strains, coarse grains, dark wounds, stamping parts with such defects are acceptable in zones III and IV.

3. Deflated pond

Inspection Method: Visual, Stone Grinding, Touching, Oiling Evaluation Criteria:

Class A defects: are defects that cannot be accepted by the user, and can be noticed by untrained users, and the stamping parts must be frozen immediately after the discovery of such deflated ponds, and the stamping parts of Class A deflated ponds are not allowed to exist in any area.

Class B defect: It is an unpleasant defect, it is a definite deflated pond that can be touched and seen on the outer surface of the stamping part, and such a deflated pond is not allowed on the outer surface of the stamping part I and II.

Class C defects: are defects that need to be corrected, and most of these deflated ponds are in an ambiguous situation, which can only be seen after the oil stone has been polished. Precision Stamping parts of such deflated ponds are acceptable.

4. Waves

Inspection Method: Visual, Stone Grinding, Touching, Oiling Evaluation Criteria:

Class A defects: This type of wave can be noticed by an untrained user in the stamping parts I and II areas, but the user cannot receive them, and the stamping parts must be frozen immediately after discovery.

Class B defects: This type of wave is an unpleasant defect, which can be felt and seen in the stamping parts I and II. and can be identified as waves, which need to be repaired.

Class C defects: are defects that need to be corrected, and most of these waves are in an ambiguous situation and can only be seen after the stone has been sanded. Stamping parts of such waves are acceptable.

5. Uneven and shortage of flanging and cutting edges

Test Method: Visual, Touch Evaluation Criteria:

Class A defects: for the unevenness and shortage of any flanging and trimming of the inner and outer covers, which affects the quality of the undercut and the unevenness and shortage of the welding lap, thus affecting the welding quality, it is unacceptable to freeze the stamping parts immediately after being found.

Category B defects: visible and identifiable unevenness and shortages of flanging and trimming that have no effect on undercut, welding lap and welding quality. (Concerned mw1950pub) stamping parts with such defects are acceptable in Zone II. III. and IV.

Class C defects: Slight flanging, unevenness and shortage of trimming have no effect on the quality of undercut and lap welding, and stamping parts with such defects are acceptable.

6. Burr: (trimming, punching).

Test Method: Visual Evaluation Criteria:

Class A defects: Punching holes that seriously affect the degree of welding lap fit and stamping parts positioning and assembly, and coarse burrs that are easy to cause personal injury, the stamping parts with this defect are not allowed to exist and must be repaired.

Category B defects: Medium burrs that have a slight impact on the degree of fit of the welded lap and the punching hole for the positioning and assembly of the stamping part. Stamping parts with this defect are not allowed to exist in areas I and II.

Category C defects: small burrs, which are allowed to exist in stamped parts without affecting the quality of the whole vehicle.

7. Hair pulling and scratching

Test Method: Visual Evaluation Criteria:

Class A defects: Brushing and scratching that seriously affect the surface quality and can potentially lead to cracking of the stamped parts, and the presence of such defects is not allowed.

Category B defects: Visible and identifiable brushing and scratching, stamped parts with such defects are allowed to exist in zone IV.

Category C defects: Minor defects may cause scratching and scratching of stamped parts, and stamped parts with such defects are allowed to exist in zones III and IV.

8. Rebound

Inspection method: put on the inspection fixture to inspect the evaluation criteria:

Class A defects: Springback that leads to dimensional matching and welding deformation between stamped parts, and such defects are not allowed to exist in stamped parts.

Class B defects: Springback with large dimensional out-of-tolerance, which has an impact on the dimensional matching and welding deformation between stamping parts, and such defective stamping parts are allowed to exist in III. and IV zones.

Class C defects: Springback with small dimensional out-of-tolerance and slight impact on the dimensional matching and welding deformation between stamped parts, and the presence of I., II., III., IV. zones is allowed for stamping parts with such defects.

9. Leakage punching

Test method: visual inspection and counting mark with a water-soluble marker.

Evaluation criteria: Missing punch from any hole in the stamping part will affect the positioning and assembly of the stamping part and is unacceptable.

10. Wrinkling

Test Method: Visual Evaluation Criteria:

Class A defects: Severe wrinkles that result in overlapping materials, and stamped parts with this defect are not allowed.

Class B defects: visible, palpable wrinkles that are acceptable in Zone IV.

Class C defects: Minor, less noticeable wrinkles, stamped parts with such defects are acceptable in zones II., III., IV.

11. Pockmarks, pittings, indentations

Inspection Method: Visual, Stone Grinding, Touching, Oiling Evaluation Criteria:

Class A defects: pitting is concentrated, more than 2/3 of the entire area is distributed with pitting, such defects must be frozen immediately after being found in areas I and II.

Class B defects: pittings can be seen and touched. Such defects are not allowed in areas I and II.

Class C defects: Individually distributed pitting spots can be seen after grinding, and the distance between the pitting spots is required to be 300mm or more in the I area. Stamping parts with such defects are acceptable.

12. Polishing defects and polishing marks

Test Method: Visual, Stone Grinding Evaluation Criteria:

Category A defects: worn out, clearly visible on the exterior surface, immediately visible to all customers. As soon as such stamps are discovered, the stamped parts must be frozen

Category B defects: can be seen, touched, and can be proved after polishing in disputed areas, and such defects are acceptable in areas III and IV.

Class C defects: After grinding with oil stones, it can be seen that stamping parts with such defects are acceptable.

13. Material defects

Test Method: Visual Evaluation Criteria:

Class A defects: the strength of the material does not meet the requirements, the traces, overlaps, orange peels, stripes, loose galvanized surface, and peeling of the galvanized layer left by the rolled steel plate. As soon as such stamps are discovered, the stamped parts must be frozen.

Category B defects: material defects left by rolled steel plates, obvious marks, overlaps, orange peels, streaks, loose galvanized surfaces, and peeling galvanized layers, such defects are acceptable in Zone IV.

Class C defects: material defects left by rolled steel plates, such as marks, overlapping, orange peel, streaks, loose galvanized surface, and peeling galvanized layers.

14. Oil pattern

Inspection method: visual, oil stone grinding

Evaluation criteria: No obvious marks are allowed in areas I and II after polishing with oil stones.

15. Bumps and depressions

Inspection Method: Visual, Touch, Stone Grinding Evaluation Criteria:

Class A defects: are defects that cannot be accepted by the user, and can be noticed by untrained users, and the stamping metal components must be frozen immediately after the discovery of Class A bumps and depressions.

Class B defect: It is an unpleasant defect, which is a definite bump and depression that can be felt and seen on the outer surface of the stamping part. Such defects are acceptable in Zone IV.

Class C defects: are defects that need to be corrected, and most of these bumps and depressions are in ambiguous conditions, and can only be seen after the oil stone is polished. Such defects II., III., IV. are acceptable.

16. Rust

Inspection Method: Visual

Evaluation criteria: Stamping parts are not allowed to have any degree of corrosion.

17. Stamping and stamping

Test Method: Visual Evaluation Criteria:

Class A defects: stamps that cannot be received by the user and can be noticed by untrained users, and must be frozen immediately after being discovered.

Category B defect: It is an unpleasant stamping mark that can be felt and seen on the outer surface of the stamping part. Such defects are not allowed to exist in the I. and II areas, and are acceptable in the case that the III. and IV areas do not affect the quality of the vehicle.

Class C defects: stamping stamps that can only be determined by polishing with a stone. Stamping parts with such defects are acceptable without affecting the quality of the whole vehicle.