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

An Introduction To 3D Drafting & Solid Modelling | AutoCAD 3D Modelling Tools

AutoCAD 3D Modelling:

Before study the 3D modelling, it would be desirable to study the 3D co-ordinate systems.

3D Co-ordinate systems

1. Absolute 3D co-ordinate system:

XY plane is assumed to be parallel to the computer screen. +Z axis is perpendicular to the computer screen projecting towards the user.

A point with co-ordinate 3, 3, 5. Where 3 units along +x axis, 3 units up along +y axis and finally 5 units towards the user (along +z axis).

01- Absolute 3D coordinate system

2. Relative cylindrical co-ordinate system:

A point at 4<30, 5 is marked using relative cylindrical co-ordinate system. 4 units from the last reference point along +x axis, 30 degrees from the x-axis measured

in the anticlockwise directionin the xy plane and 5 units along the +z axis.

01 - Relative cylindrical coordinate system

3. Relative spherical co-ordinate system:

A point at 5<30<40 is marked using relative spherical co-ordinate system. 5 units from the last reference point along +x axis, 30 degrees from the x-axis measured in the anticlockwise direction in xy plane and 40 degrees up from xy plane.

01 - Relative spherical coordinate system

Types of 3D modelling:

3D modelling is of three types. They are

1. Wire frame modelling

2. Surface modelling

3. Solid modelling

Wire frame modelling:

Wire frame model is a 3D representation of objects by using mostly lines, arcs and circles. It is skeletal and does not have surfaces. Only edge details are shown by a wire frame model.

Surface modelling:

In surface modelling, the 3D object is made up of opaque surfaces (3D faces). The inner portion of the object is hollow. The details available behind the surfaces are hidden.

Solid modelling:

In solid modelling, a solid 3D object is produced. It is like a solid object made of a material like wood. The solid thus produced can be cut into pieces. Mass properties of solid models can be determined.

Some of the 3D autocad commands are listed below:

1. Box: box is used to draw three dimensional solid box. The command is BOX. It can be selected from solids toolbar or draw menu – solids

2. Cylinder: cylinder is used to draw three dimensional solid cylinder. The command is CYLINDER. It can be selected from solids toolbar or draw menu – solids

3. Elliptical: The command is CYLINDER. It can be selected from solids toolbar or draw menu – solids

4. Cone: Cone is used to draw a three dimensional cone. The command is CONE. It can be selected from solids toolbar or draw menu – solids

5. Sphere: Sphere is used to draw a three dimensional solid sphere. The command is SPHERE. It can be selected from solids toolbar or draw menu-solids

6. VPoint: VPOINT is used to specify the viewing direction for a three dimensional visualization of the drawing. The command is VPOINT. It can be selected from view menu – 3D view point (Tripod / Vector). Vpoint locates the observer in a specified position to look at the drawing back at the origin 0,0,0.

7. 3D FACE: 3D Face is used to draw a three dimensional face. The command is 3D face or 3F. it can be selected from surfaces toolbar or Draw menu – Surface. 3D face is used to draw a three or four sided surface anywhere in 3D space. Each corner point can be assigned different Z – coordinate values.

8. Elevation: ELEV is used to draw elevation and set extrusion thickness properties of new objects.