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,
01 - slag inclusions - casting defects


Segregations,
Gas pockets,
01 - blow holes - porosity - casting defects


Internal shrinkage,
Surface crack,
01- surface cracks - casting defects


Pipes,
Gas porosity,
01- pipes - gas porosity - casting defects


Hot tears,
01- hot tears - casting defects


Cold shuts, and
01- cold shut - casting defects


Cavities
01- cavities - casting defects


2. Welding:


Gas welding,
Resistance welding,
Arc welding,
Friction welding,
Brazing,
Soldering and
Diffusion bonding



Defects Encountered during Manufacturing and Service


Lack of fusion,
01 - lack of fusion - welding defects


Incomplete penetration,
Cracks,
01- cracks - welding defects


Slag inclusion,
Gas porosity,
01 -  weld porosity


Crack in parent metal,
Root undercutting
01 - root undercuts - welding defects


3. Forming:


Forging,
Rolling,
Wire drawing,
Deep drawing,
Bending,
Extrusion



Defects Encountered during Manufacturing and Service
Inclusion,
01- rolling defects


Segregation,
Pipes,
Seams,
01- rolling defects -1


Laps,
Bursts,
01 - internal bursts - forming defects


Cracks,
Tears,
01 - surface tear - forming defects


Lamination,
01 - Lamination - forming defects


Flakes,
Rolled-in scale,
Roll mark,
Die-mark,
Thermal crack


4. Machining:
Cutting,
Drilling,
Turning and
Milling



Defects Encountered during Manufacturing and Service


Cracks,
01- surface cracks - machining defects


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
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