Manufacturing And Design Defects | Manufacturing Defect Examples

Major manufacturing processes and its defects

The major materials used for engineering activities are grouped into four classes, namely,

1. Metals and Alloys,

2. Ceramics,

3. Polymers and

4. Composites.

Each of these materials has a distinct property profile.

Pure metals find limited application, while metals and alloys (ferrous and Non ferrous) are the most widely used engineering materials. Materials are subjected to many manufacturing processes to produce not only the desired shape but also to ensure the design – stipulated physical and mechanical properties and dimensional tolerances. Further, components are provided with necessary surface protection from corrosion and erosion. However, all manufacturing operations and service environments induce various types of defects in engineering components, which need to be detected and evaluated.

1. Casting:

Sand casting,

Die casting,

Permanent mold casting,

Investment Casting and

Continuous casting

Defects Encountered during Manufacturing and Service

Inclusions,

Segregations,

Gas pockets,

Internal shrinkage,

Surface crack,

Pipes,

Gas porosity,

Hot tears,

Cold shuts, and

Cavities

2. Welding:

Gas welding,

Resistance welding,

Arc welding,

Friction welding,

Brazing,

Soldering and

Diffusion bonding

Defects Encountered during Manufacturing and Service

Lack of fusion,

Incomplete penetration,

Cracks,

Slag inclusion,

Gas porosity,

Crack in parent metal,

Root undercutting

3. Forming:

Forging,

Rolling,

Wire drawing,

Deep drawing,

Bending,

Extrusion

Defects Encountered during Manufacturing and Service

Inclusion,

Segregation,

Pipes,

Seams,

Laps,

Bursts,

Cracks,

Tears,

Lamination,

Flakes,

Rolled-in scale,

Roll mark,

Die-mark,

Thermal crack

4. Machining:

Cutting,

Drilling,

Turning and

Milling

Defects Encountered during Manufacturing and Service

Cracks,

Nicks,

Scratches and ridges,

Tears and laps,

Hardness alteration,

Residual stress distribution,

Deformed debris,

Grain size change,

Inter-granular corrosion,

Embrittlement cracks

5. Powder metallurgy:

Compressing of metal powder into solid mass by application of pressure and heat

Defects Encountered during Manufacturing and Service

Porosity,

Cracks,

Inclusion,

Variation in density distribution

6. Heat treatment:

Specific to alloys to impart desired microstructure, hardness, strength and stiffness

Defects Encountered during Manufacturing and Service

Cracks,

Segregation,

Grain size changes

7. Surface protection:

Surface protection of components is provided by organic, inorganic and metallic coating:

(i) Organic coating: Paints and lubricants

(ii) Inorganic coating: Phosphating and chromating

(iii) Metallic coating: Electroplating, coating by diffusion e.g. galvanizing, aluminizing, metalizing by a spray of partially melted material

Defects Encountered during Manufacturing and Service

Dents,

Scratches,

Change in thickness of coating,

Insufficient protection of surface, and Erosion of protective