Purpose and Scope
The purpose of this document is to provide guidelines for assessing surface damage on machined parts. This instruction defines types of surface damage and establishes acceptance criteria for visual inspection of parts. Aluminum parts differ from parts made of other alloys in that casual contact between them or between them and other items will result in dings and bangs that are unacceptable to our customers. All parts regardless of alloy shall be protected in a manner that prevents any contact of a detrimental nature.
Responsibility
- It is the responsibility of the Quality Assurance Department to apply this standard at the time of material receipt whether from a supplier or from the PMD factory.
- Manufacturing Engineering is responsible to annotate the production planning document (traveler) with the reference to this standard and the addition of cautionary notes as required.
Requirements
- Customer drawing requirements take precedence over the acceptance criteria described in this document.
- Parts and assemblies shall be visually inspected per this specification and the applicable documents as specified on the engineering drawing, the Traveler or Purchase Order. Table 1 shows the definition of flaws that may be seen on the exterior of the part.
- Visual inspection shall be performed without magnification and shall be under “cool white” fluorescent illumination. Illumination shall be of a sufficient intensity as to adequately illuminate the area to be evaluated. Additional illumination may be used as required to adequately evaluate a surface (e.g. flashlight or spotlight). When a closer evaluation is required, a magnification of 4X may be used.
- Quality Assurance personnel evaluating the visual quality of products are required to have their vision tested periodically to ensure that their vision meets the minimum requirement for visual perception.
- The stylus (probe) referenced in Table 1 for use in assessing the acceptability of surface defects shall have a .025 inch spherical end and be fabricated of a material that will not damage the surface or contaminate the part.
- If a batch of parts shows a trend of defects, QA shall be notified to investigate why a trend is developing and to institute corrective action as needed.
Surface Flaws
- Surface flaws as described in Table 1 may affect appearance or function. any surface flaw that affects function must be evaluated by the customer.
- No surface flaws shall be accepted on surfaces specified to have a 63 microfinish or better or where the dimensional tolerance is +/- .0005 or tighter.
- Visual imperfections which will be completely removed by subsequent machining or processing operations shall be disregarded.
- Cracks, chips, burrs, sharp edges, pits, porosity, corrosion, forging material, burn marks, and missing operations (e.g. missing holes) are not acceptable.
- The transition of fillets and sharp edges shall be smoothly blended or rounded.
Rework
Rework shall be accomplished in accord with applicable standards (e.g.Mil-A-8625) shall be within the limit of size or shall be per customer instructions. Any rework is bound to meet the end item requirements as specified by the customer contract.
Table 1
| Surface Flaw | Definition | Applicable Parts | Condition | Notes |
| Burnish Marks | A local smoothing of a metal surface, often to a high luster resulting from rubbing | All Parts and details. | Acceptable | |
| Burr | A rough ridge or edge left at the intersection of two surfaces. | All Parts and details. | Rejectable | |
| Color Variation | Color is not exactly the same between parts | All Parts and details. | Acceptable | |
| Corrosion | A deterioration of the metal resulting in a change of color and leaving a rough surface that may show pits (small cavities) | All Parts and details. | Rejectable | |
| Crack | Line of fracture without complete separation, to the unaided eye; may also occur along edge or corner | All Parts and details. | Rejectable | |
| Dent | Imperfection of the surface caused by a blunt object in such a manner that the surface suffers no material loss but shows an indentation | All Parts and details. | Rejectable | |
| Discoloration | A localized or generalized change in the color of the part | All Parts and details. | submit for review | Provided the areas affected blend into the surrounding color without a sharp line of demarcation. |
| Fingerprints | Stains left by unprotected hands. | All Parts and details. | Re-work | Clean and re-submit |
| Foreign Material | A solid or liquid material or substance not integral to a part. Such material or substance may or may not be adherent to part surfaces or passages. Material chips shall be considered as foreign material. | All Parts and details. | Rejectable | |
| Nick | An indent having raised sharp edges, corners or bottom | All Parts and details. | Acceptable | Provided it cannot be felt by the probe. Any raised material must be removed |
| Pitting | Voids that extend into the surface. A cavity in the metal of a surface | All Parts and details. | Rejectable | |
| Scratch | Mark made with a sharp or rough object | All Parts and details. | Acceptable | Provided it cannot be felt by the probe. Rework of any finish damage is required |
| Step | An abrupt change in a surface profile or a mismatch between two or more surfaces | All Parts and details. | Acceptable | Unless otherwise specified |
| Tear | Separation of the material on sheet metal parts or pulled material resulting from machining | All Parts and details. | Rejectable | |
| Machine Tool Mark (includes chatter marks.) | A mark in the direction of the machining lay left by the machining tool. Marks can be straight, circular or spiral. | All Parts and details. | Acceptable | Provided it cannot be felt by the probe or meets customer requirements. |
| Undercut | A groove or recess cut into a surface near a shoulder or other projection | All Parts and details. | Acceptable | Provided it blends smoothly with the adjacent surfaces. |
| Blister | A localized lifting of coating, plating or paint from the base material, appearing as a bulge that may break when probed usually caused by excessive heat, unclean surfaces, or chemical action | All Parts and details. | Rejectable | |
| Bulge, Bump | A hill-like elevation swelling, or protuberance departing from the adjacent surface | All Parts and details. | Submit for Review | May be acceptable subject to the limit of size |
| Chip | Loose metal or material fragments usually found trapped in cast passages, bottom of blind holes, hole intersections etc. | All Parts and details. | Re-work | Must be removed where present |
| Crater | A hollow with circular contour and raised edge, resembling a mouth of a volcano | All Parts and details. | Rejectable | |
| Crazing | A network of fine cracks caused by local contraction usually chemical in origin, occurring in plating, spray coatings, and abuse to ground surfaces | All Parts and details. | Rejectable | |
| Feather Edge | A particular type of burr tapered to a thin edge, found at the intersection of machined surfaces before the edge is broken or improperly broken | All Parts and details. | Rejectable | |
| Flash | A burr expelled in the gap between mold parts or die parts when forming | Forged and Casted Parts | Rejectable | |
| Gouge | Smooth sided trough-like depression caused by the tearing away of the surface by another sharp object | All Parts and details. | Rejectable | |
| Inclusions | A visible particle of foreign material retained in the metal during solidification which has been revealed during processing | All Parts and details. | Rejectable | |
| Lap | A tongue-like detachment of minor thickness often appearing as a seem often caused by folding over material and forcing it to the surface | Forged and Rolled Parts | Rejectable; on all machine surfaces | Depending on NDT requirements, may be rejectable on forged surfaces, in which case re-work is required |
| Porosity | A group of closely spaced small holes or voids of variable depth and shape | Forged and Casted Parts | Rejectable | Unless acceptable per blueprint |
| Scale | A flake-like detachment of minor thickness | All Parts | rejectable on finished machine surfaces | On other surfaces to be evaluated |
| Stain | Surface discoloration due to liquids drying on the part | All Parts | Acceptable | Subject to applicable specifications |
| Tiger Striping | Discoloration of base metal brought on by Anodizing Process | Boeing Parts made of 7000 series aluminum |
Evaluate Per BAC 5019 11.1 |
Extruded material is more prone to manifest this condition. may be present on Cold finished materials also. |
| Discolored areas associated with variations in the microstructure. | Discoloration of forged surfaces after Anodizing process | Boeing Forgings made of 7000 series Aluminum in the T-7XXX Temper. |
Acceptable Per BAC 5019 11.1 |
|
| Scallops | Machining marks left on surfaces after being contoured by a spherical end mill. | Parker Hannifin parts | Acceptable per individual drawing requirements |
| Scallops | Gouges | Nicks | Dents | Scratches | Burrs |
 |
 |
 |
 |
 |
 |
Revision History
| Revision Date | Reviewed By | Comment |
| 9/19/15 | SS | Initial Release |
| 9/28/15 | SS | Added, Scallops, Tiger Striping, Discoloration Due To Microstructure |
| 5/2/2017 | SM | Changed to SP 8.5.4 from SP 7.5.4 |