This stage focuses on precision manufacturing to create individual components with high accuracy and tight tolerances, using:

• Computer numerical control (CNC) machinery (mills, lathes, etc.) to precisely remove material
• Focused laser beam to cut materials with high precision and speed
• Forming processes like bending, stamping and deep drawing to shape materials without removing substance

To illustrate, the above methods might be used to machine a complex engine part from a solid block of metal, while a thin sheet metal enclosure might be laser-cut and then bent to a desired shape.

This stage involves expert joining of individual components to create larger assemblies or subsystems. Methods include:

• Common arc welding to melt and fuse materials
• Resistance welding using heat and pressure to join materials
• Laser welding for high-precision work
• Friction stir welding, a solid state process that creates a very strong bond
• Brazing and soldering
• Adhesive bonding
• Mechanical fastening using bolts, screws, rivets, etc.

With joining work completed, multiple components are assembled into functional subsystems or complete products. This step requires precise alignment, fit and tolerances, as illustrated by the assembly of an auto engine or an aircraft.

This stage calls for the application of appropriate finishes for protection, durability, aesthetic qualities and other purposes. Common treatments include:

• Painting and powder coating for corrosion protection and food appearance
• Electroplating or electroless plating for corrosion and wear resistance and enhanced conductivity
• Anodizing to create a protective oxide layer on aluminum
• Heat treatment (e.g., case hardening or nitriding) to increase surface hardness
• Blasting (sandblasting or shot peening) to clean or strengthen surfaces

During this stage, engineers and technicians perform comprehensive testing and verification to ensure that all components and assemblies meet design specifications and quality standards. Methods include the following:

• Dimensional inspection, which uses calipers, micrometers and coordinate measuring machines (CMM) to verify dimensions. For example, a CMM could be used to check the dimensions of a machined part.
• Non-destructive testing (NDT) which employs techniques such as ultrasonic testing, radiography and magnetic particle inspection to detect internal defects without damaging the part. For instance, ultrasonic testing could be used to check a welded joint for cracks.
• Functional testing to verify the performance of components or assemblies under simulated operating conditions
• Material testing that verifies the mechanical and chemical properties of materials

This stage is the final assembly and integration of mechanical, electrical and control components into complete systems. This stage requires careful planning, coordination and precision to ensure that all elements work together as intended. Integration of electrical and control systems could include wiring, control panel installation, and loading of software.