Common Inspection Methods And Defect Evaluation Criteria For Stamping Parts

1、 Inspection methods for stamping parts
1. Touch inspection
Wipe the surface of the outer cover with clean gauze. The inspector needs to wear touch gloves to touch the surface of the stamped part longitudinally, and this inspection method depends on the inspector's experience. If necessary, oil stones can be used to polish and verify the suspicious areas that have been detected, but this method is an effective and fast inspection method.
2. Oil stone polishing
2.1. First, wipe the surface of the outer cover with clean gauze, and then polish it with an oilstone (20 × twenty × 100mm or larger), use relatively small oilstones to polish areas with circular arcs and difficult to reach areas (e.g. 8 × 100mm semi circular oilstone)
The selection of oil stone particle size depends on the surface condition (such as roughness, galvanizing, etc.). It is recommended to use fine-grained oilstones. The direction of oil stone polishing is basically carried out along the longitudinal direction, and it fits well with the surface of the stamped parts. In some special areas, horizontal polishing can also be supplemented.
3. Polishing of Flexible Yarn Mesh
Wipe the surface of the outer cover with clean gauze. Grind the surface of the stamped part longitudinally with a flexible sand mesh to the entire surface, and any pitting or indentation will be easily detected.
4. Oil coating inspection
Wipe the surface of the outer cover with clean gauze. Use a clean brush to evenly apply oil in the same direction to the entire outer surface of the stamped part. Place the oiled stamped parts under strong light for inspection. It is recommended to place the stamped parts vertically on the vehicle body. By using this method, it is easy to detect small pits, pits, and ripples on the stamped parts.
5. Visual inspection
Visual inspection is mainly used to detect appearance abnormalities and macroscopic defects of stamped parts
6. Inspection with inspection tools
Place the stamped parts into the inspection tool and inspect them according to the operating requirements of the inspection tool manual.
2、 Evaluation criteria for defects in stamping parts
1. Cracking
Inspection method: Visual evaluation criteria:
Class A defect: Cracking that can be noticed by untrained users, and stamping parts with such defects are unacceptable to users. Once discovered, stamping parts must be immediately frozen.
Class B defects: visible and identifiable small cracks, which are unacceptable in areas I and II of stamped parts. Repair welding and repair are allowed in other areas, but the repaired parts are difficult for customers to detect and must meet the repair standards of stamped parts.
Class C defect: a defect that is ambiguous and determined after careful inspection. Stamped parts with this type of defect are repaired by welding within Zone II, Zone III, and Zone IV, but the repaired parts are difficult for customers to detect and must meet the repair standards for stamped parts.
2. Strain, coarse grain size, and dark damage
Inspection method: Visual evaluation criteria:
Class A defects: Strains, coarse grains, and hidden damages that can be noticed by untrained users. Stamped parts with such defects are unacceptable to users and must be frozen immediately upon discovery.
Class B defects: visible and identifiable minor strains, coarse grains, and dark damages. Stamped parts with such defects are acceptable in Zone IV.
Class C defects: slight tensile damage, coarse grain size, and dark damage. Stamped parts with such defects are acceptable in zones III and IV.
3. Withered pond
Inspection method: visual inspection, oilstone polishing, touching, and oiling Evaluation criteria:
Class A defect: It is a defect that cannot be accepted by users and can be noticed by untrained users. Once such a sink is discovered, the stamping parts must be immediately frozen. Class A sink stamping parts are not allowed to exist in any area.
Class B defect: It is an unpleasant defect that can be identified and visible on the outer surface of the stamped part. Such defects are not allowed to exist on the outer surface of zones I and II of the stamped part.
Class C defect: It is a defect that needs to be corrected, and the vast majority of these pits are in ambiguous situations that can only be seen after polishing with oil stones. Stamped parts of this type of sink are acceptable.
4. Waves
Inspection method: visual inspection, oilstone polishing, touching, and oiling Evaluation criteria:
Class A defect: This type of wave can be noticed by untrained users in areas I and II of stamping parts, and cannot be accepted by users. Once discovered, the stamping parts must be immediately frozen.
Class B defect: This type of wave is an unpleasant defect that can be felt and seen in the stamping parts in areas I and II, and is a identifiable wave that needs to be repaired.
Class C defect: It is a defect that needs to be corrected, and most of these waves are in ambiguous situations that can only be seen after polishing with oil stones. Stamped parts with such waves are acceptable.
5. Uneven and insufficient flanging and trimming
Inspection method: Visual and touch evaluation criteria:
Class A defect: Any unevenness or shortage of flanging or cutting edges on the inner and outer covering parts, which affects the quality of the undercut and the welding overlap unevenness or shortage, and thus affects the welding quality, is unacceptable. Once discovered, the stamped parts must be immediately frozen.
Class B defects: visible and determinable unevenness and shortage of flanges and cuts that do not affect the undercut, welding overlap, and welding quality. Stamped parts with such defects are acceptable within Zone II, III and IV.
Class C defects: Minor unevenness and shortage of flanging and cutting edges do not affect the quality of undercut and overlap welding, and stamping parts with such defects are acceptable.
6. Burr: (trimming, punching)
Inspection method: Visual evaluation criteria:
Class A defects: Punches that seriously affect the degree of welding overlap and the positioning and assembly of stamped parts, as well as coarse burrs that can easily cause personal injury, are not allowed to exist in stamped parts and must be repaired.
Class B defect: Moderate burrs that have a slight impact on the degree of welding overlap and the punching of stamping parts for positioning and assembly. Stamped parts with this defect are not allowed to exist in zones I and II.
Class C defect: Small burrs are allowed to exist in stamped parts without affecting the overall quality of the vehicle.
7. Bruising and scratches
Inspection method: Visual evaluation criteria:
Class A defects: serious impact on surface quality, potential burrs and scratches that can cause tensile cracks in stamped parts, and stamped parts with such defects are not allowed to exist.
Class B defects: visible and identifiable burrs and scratches, and stamping parts with such defects are allowed to exist in Zone IV.
Class C defects: Minor defects may cause burrs and scratches on the stamped parts, and stamped parts with such defects are allowed to exist in zones III and IV.
8. Rebound
Inspection method: placed on the inspection tool, inspection evaluation criteria:
Class A defect: Causes severe rebound in size matching and welding deformation between stamped parts, and such defects are not allowed in stamped parts.
Class B defect: Springback with significant size deviation that affects the size matching and welding deformation between stamped parts. This type of defect is allowed to exist in zones III and IV of stamped parts.
Class C defect: rebound with small size deviation and slight impact on size matching and welding deformation between stamped parts. This type of defect is allowed to exist in zones I, II, III, and IV of stamped parts.
9. Leakage punching hole
Inspection method: Visual inspection and counting with a water-soluble marker pen
Evaluation criteria: Any hole leakage on the stamped part will affect the positioning and assembly of the stamped part, which is unacceptable.
10. Wrinkling
Inspection method: Visual evaluation criteria:
Class A defect: Severe wrinkling resulting in material overlap, and stamping parts with this defect are not allowed to exist.
Class B defect: visible and palpable wrinkling, which is acceptable in Zone IV.
Class C defects: slight and less obvious wrinkling, and stamping parts with such defects are acceptable in areas II, III, and IV.
11. Pitting, Pitting, Indentation
Inspection method: visual inspection, oilstone polishing, touching, and oiling Evaluation criteria:
Class A defect: The pits are concentrated and distributed over 2/3 of the entire area. Once such defects are found in zones I and II, the stamped parts must be immediately frozen.
Class B defect: visible and palpable pits. Such defects are not allowed to appear in zones I and II.
Class C defect: After polishing, separate distribution of pits can be seen, and in Zone I, the distance between pits is required to be 300mm or greater. Stamped parts with such defects are acceptable.
12. Grinding defects, polishing marks
Inspection method: Visual inspection, oil stone polishing evaluation criteria:
Class A defect: Polished through, clearly visible on the outer surface, immediately visible to all customers. Once such stamping is discovered, the stamped parts must be immediately frozen
B-type defects: visible, palpable, and can be proven after polishing in disputed areas. These defects are acceptable in areas III and IV. Class C defect: After polishing with an oilstone, it can be seen that stamping parts with such defects are acceptable.
13. Material defects
Inspection method: Visual evaluation criteria:
Class A defects: Material strength does not meet the requirements, marks, overlaps, orange peel, stripes left by the rolled steel plate, loose galvanized surface, and peeling of the galvanized layer. Once such stamping is discovered, the stamped parts must be immediately frozen.
Class B defects: Material defects left by rolled steel plates, such as obvious marks, overlaps, orange peel, stripes, loose galvanized surface, and peeling of galvanized layer, are acceptable in Zone IV.
Class C defects: Material defects such as marks, overlap, orange peel, stripes, loose galvanized surface, and peeling of galvanized layer left by the rolled steel plate are acceptable in areas III and IV.
14. Oil pattern
Inspection method: visual inspection, oil stone polishing
Evaluation criteria: No obvious marks are allowed in areas I and II after being polished with oil stones.
15. Bumps, depressions
Inspection method: Visual inspection, touch, and oil stone polishing Evaluation criteria:
Class A defect: It is a defect that cannot be accepted by users, and can be noticed by untrained users. Once Class A protrusions or depressions are found, the stamped parts must be immediately frozen.
B-type defect: It is an unpleasant defect that can be identified as bumps or depressions that can be touched or seen on the outer surface of the stamped part. This type of defect is acceptable in Zone IV.
Class C defect: It is a defect that needs to be corrected. Most of these protrusions and depressions are ambiguous and can only be seen after polishing with oil stones. Such defects in areas II, III, and IV are acceptable.
16. Rust
Inspection method: visual inspection
Evaluation criteria: Stamped parts are not allowed to have any degree of corrosion.
17. Stamping printing
Inspection method: Visual evaluation criteria:
Class A defects: Stamping marks that cannot be accepted by users and can be noticed by untrained users. Once such stamping marks are discovered, the stamped parts must be immediately frozen.
B-type defect: It is an unpleasant and identifiable stamping mark that can be touched and seen on the outer surface of the stamped part. Such defects are not allowed to exist in zones I and II, and can be accepted in zones III and IV without affecting the overall quality of the vehicle.
Class C defect: a stamping mark that requires polishing with an oilstone to determine. Stamped parts with such defects are acceptable without affecting the overall quality of the vehicle.