Stamped Part Defect Evaluation Guidelines

Inspection methods for stamping parts

Touch inspection

Use clean gauze to wipe the surface of the outer covering. The inspector must wear touch gloves along the longitudinal direction of the stamping parts and touch the surface of the stamping parts. This inspection method depends on the experience of the inspector. If necessary, oil stone can be used to polish the suspected area and verify, but this method is not a proven method of rapid inspection.

Oil stone polishing

First, use clean gauze to wipe the surface of the outer covering, and then polish with oil stone (20×20×100mm or larger). There are rounded places and difficult-to-reach places with relatively small oil stone polishing (for example, 8×100mm semi-circular oil stone).

The choice of oil stone size depends on the surface condition (e.g., roughness, galvanization, etc.). It is recommended to use a fine-grained oil stone. The direction of oil stone polishing is basically along the longitudinal direction. It fits well to the surface of the pressed parts, and some special places can be supplemented with horizontal polishing.

Sanding of flexible gauze

Wipe the surface of the outer covering parts with clean gauze. Use flexible gauze to sand along the longitudinal direction closer to the surface of the stamping parts to the whole surface. Any pockmarks and indentations will be easily found.

Oiling inspection

Wipe the surface of the outer covering part clean with a clean gauze cloth. Then use a clean brush to apply oil evenly along the same direction to the whole outer surface of the stamping. Put the oiled stamped parts under a strong light to inspect, and it is recommended to put the stamped parts vertically on the body position. This method can easily find tiny pockmarks, deflated ponds, and grooves on the stamped parts.

Visual inspection

Visual inspection is mainly used to determine the appearance abnormality and macroscopic defects of the stamped parts.

Checker inspection

Put the stamping parts into the inspection tool and test the stamping parts according to the operational requirements of the inspection tool manual.

Criteria for evaluating the defects of stamping parts

Cracking

Inspection method: Visual evaluation guidelines.

Class A defects: Cracking users can notice that without training, such defective stamped parts are unacceptable to users, and the stamped parts must be frozen immediately after discovery.

Class B defects: visible and identifiable minor cracks; such defects are unacceptable in zones Ⅰ and Ⅱ of the stamped parts; other zones are allowed to be reworked by welding, but customers do not easily detect the reworked parts must meet the reworking standards of the stamped parts.

Class C defects: Defects that are ambiguous and determined after careful inspection, stamping parts with such defects are allowed to be reworked in Zone Ⅱ, Zone Ⅲ, and Zone Ⅳ, but the reworked parts are not easily detected by customers and must meet the reworking standards for stamping parts.

Drawing, coarse grain, dark injury

Inspection method: visual inspection Evaluation criteria.

Class A defects: strains, coarse grains, and dark injuries that untrained users can notice; such defects are unacceptable to users, and the stamped parts must be frozen immediately after discovery.

Class B defects: visible and identifiable minor strains, coarse grains, and dark defects; such defective stampings are acceptable in Zone IV.

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

Deflated pond

Inspection methods: visual inspection, oil stone polishing, touching, and oiling. Evaluation guidelines.

Class A defect: It is a defect that cannot be received by users and can be noticed without training. Such deflated ponds must be frozen on the stamped parts immediately after discovery, and Class A deflated ponds with stamped parts are not allowed to exist in any area.

Class B defect: It is a defect that makes people feel unpleasant. It is a definable deflated pond that can be touched and seen on the external surface of the stamped part, and the such deflated pond is not allowed to exist on the external surface of zones I and II of the stamped part.

Class C defect: It is a defect that needs to be corrected. Most of these deflated ponds are in an ambiguous situation and can be seen only after oil stone polishing. Such deflated ponds are acceptable for stamped parts.

Waves

Inspection methods: visual inspection, oil stone polishing, touching, and oiling. Evaluation guidelines.

Class A defects: Such waves can be noticed by users without training in the Ⅰ and Ⅱ areas of the stamped parts and are not acceptable to users, and the stamped parts must be frozen immediately after discovery.

Class B defects: Such waves are a kind of defects that make people feel unpleasant and are identifiable waves that can be touched and seen in the Ⅰ and Ⅱ areas of the stamped parts and are required to be reworked.

Class C defect: It is a defect that needs to be corrected. Most such waves are in an ambiguous situation and are only visible after oil stone polishing. The stamping parts with such waves are acceptable.

Unevenness and shortage of flanged and cut edges

Inspection method: Visual inspection, touch Evaluation criteria.

Class A defects: For the inner and outer coverings, any unevenness and shortage of flanged and cut edges affect the quality of biting edges, and unevenness and shortage of welded lap edges, thus affecting the quality of welding, are unacceptable, and the stamping must be frozen immediately after discovery.

Class B defects: visible, identifiable unevenness and shortage of flanged and cut edges that do not affect the quality of biting edge, welding lap, and welding. (Focus on mw1950pub) Such defective stampings are acceptable in Zone II internal III and IV.

C defects: minor flanging, uneven cut edge, and shortage of the biting edge and lap edge welding quality have no impact; such defects of the stamping parts can be accepted.

Burr: (cut edge, punching hole)

Inspection method: visual inspection Evaluation criteria.

Class A defects: Punching holes that seriously affect the welding lap fit and the positioning assembly of the stamping parts. These coarse burrs easily lead to personal injury. The stamping parts with this defect are not allowed to exist and must be reworked.

Class B defect: A medium burr that slightly affects the degree of welding lap fit and the punching hole of the positioning assembly of the stamped parts. This defective stamping is not allowed to exist in Zone I and II.

Class C defects: Smaller burrs, which are allowed to exist in the stamping parts without affecting the quality of the whole vehicle.

Drawing and scratching

Inspection method: Visual inspection Evaluation criteria.

Class A defects: Pulling and scratches that seriously affect the surface quality and potentially lead to pulling and cracking of the stamped parts. Such defects are not allowed to exist in the stamped parts.

Class B defects: visible and identifiable hair pulling and scratching. Such defects are allowed to exist in Zone Ⅳ of the stamping parts.

Class C defects: minor strains and scratches that may lead to stamping. Such defects are allowed to exist in the Ⅲ and Ⅳ zones of the stamping.

Rebound

Inspection method: inspection on the inspection tool Evaluation criteria.

Class A defects: lead to a serious rebound of dimensional matching and welding deformation between stamping parts. Such defects are not allowed to exist in stamping parts.

Class B defects: the rebound with a large size difference impacts the size matching and welding deformation between the stamping parts. Such defects are allowed to exist in the Ⅲ and Ⅳ zones of the stamping parts.

Class C defects: Smaller dimensional deviation, slight impact on dimensional matching, and welding deformation between stamping parts; such defects are allowed to exist in Ⅰ, Ⅱ, Ⅲ, and Ⅳ zones of stamping parts.

Leakage of punching holes

Inspection method: Visual inspection and counting mark with a water-soluble marker.

Evaluation criterion: Any hole leakage punching on the stamped parts will affect the positioning and assembly, which is unacceptable.

Wrinkling

Inspection method: Visual inspection Evaluation criteria.

Class A defect: serious wrinkling, which leads to material overlap. This defect is not allowed to exist in the stamping.

Class B defects: visible and palpable wrinkles. Such defects are acceptable in Zone Ⅳ.

Class C defects: minor, less obvious wrinkles, such defects in the Ⅱ, Ⅲ, Ⅳ stamping parts are acceptable.

Pockmark group, pockmark, indentation

Inspection methods: visual inspection, oil stone polishing, touching, and oiling. Evaluation criteria.

Class A defects: pockmarks are concentrated, and over 2/3 of the area is distributed with pockmarks. Such defects must be frozen on the stamping parts immediately after they are found in Ⅰ and Ⅱ zones.

Class B defects: pockmarks can be seen and felt. Such defects are not allowed to appear in areas Ⅰ and Ⅱ.

Class C defects: individually distributed pockmarks are visible after grinding, and the distance between pockmarks is required to be 300mm or greater in Zone I. Such defects are acceptable for stamping parts.

Sanding defects, sanding marks

Inspection method: visual inspection, oil stone grinding Evaluation criteria.

Class A defects: polished through, clearly visible on the outer surface, and immediately visible to all customers. Such stamping marks must be found immediately after freezing the stamping parts.

Class B defects can be seen, felt, and proved after sanding in disputed areas. Such defects are acceptable in Zone III and IV.

Class C defects: can be seen after polishing with oil stone; such defects are acceptable for stamping parts.

Material defects

Inspection method: Visual inspection Evaluation criteria.

Class A defects: material strength does not meet the requirements, traces left by the rolled steel plate, overlap, orange peel, stripes, loose galvanized surface, galvanized layer flaking. Such stamping marks must be frozen on the stamped parts immediately after they are found.

Class B defects: Rolled steel plate left, obvious traces, overlap, orange peel, stripes, galvanized surface sparse, galvanized layer peeling material defects. Such defects are acceptable in Zone Ⅳ.

C defects: rolled steel plate left by the die diamond traces, overlap, orange peel, stripes, galvanized surface laxity, galvanized layer peeling material defects such defects Ⅲ, Ⅳ are acceptable.

Oil pattern

Inspection method: visual inspection, oil stone polishing

Evaluation criteria: Ⅰ, Ⅱ area by the oil stone polishing does not allow the existence of obvious marks.

Bump, depression

Inspection method: visual, touch, oil stone polishing Evaluation criteria.

Class A defect: It is a defect that cannot be received by users and can be noticed without training. Class A bumps and dents must be frozen on the stamped parts immediately after they are found.

Class B defect: It is a defect that makes people feel unpleasant, and it is a definable bump or dent that can be felt and seen on the external surface of the stamped part. Such defects are acceptable in Zone IV.

Class C defect: It is a defect that needs to be corrected. Most of these bumps and depressions are ambiguous and can be seen only after oil stone polishing. Such defects Ⅱ, Ⅲ, Ⅳ area can be accepted.

Corrosion

Inspection method: Visual inspection

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

Stamping mark

Inspection method: visual evaluation guidelines.

Class A defect: It is a stamping mark that cannot be received by the user and can be noticed by the user without training. Such stamping marks must be frozen on the stamped parts immediately after they are found.

Class B defect: It is an unpleasant and identifiable stamping mark that is palpable and visible on the external surface of the stamped part. Such defects are not allowed to exist in zones I and II and are acceptable in zones III and IV if they do not affect the quality of the whole vehicle.

Class C defects: stamping marks that need to be polished with oil stones to be identified. This kind of defective stamping is acceptable because it does not affect the quality of the whole car.