Metalworking Manufacturing Processes
Item 14: Manufacturing Operations
Introduction
Manufacturing operations are classified into:
- Hand Tools (filing, sawing)
- Machine Tools (shearing, sawing, drilling, turning, milling, and grinding)
- Factor-cost manufacturing (material loss, energy costs)
Filing
Filing is a manual mechanical operation that shapes metal by removing material. Parts include the ear, body, and tip. Files are classified by shape, size, and type (single or double cut).
Phases:
- Grinding: Uses a coarse file to remove a large amount of material.
- Polishing: Uses a fine file to remove small amounts of material. Consider workpiece holding, file grip, and workspace.
Sawing
Sawing is a manual operation that cuts material partially or wholly to achieve specific shapes and dimensions.
Elements:
- Saw Blade: A flexible steel tape or film with triangular teeth. Characteristics include size, tooth arrangement, and cutting angle.
- Saw Frame/Arquet: Supports the saw blade.
For correct sawing: Choose the right blade, secure the workpiece, maintain correct posture, start with a small notch, and apply moderate pressure.
General Machine Tools
Machine tools perform various metal part machining operations. Classification by power rating:
- Fixed Machines: Powerful, fed by external power (electrical, pneumatic, or hydraulic).
- Portable Machines: Less powerful, used for small jobs, may have internal power sources.
Classification by material removal: Machines that produce large amounts of chips and filings.
Manufacturing performance factors: Cutting speed, feed rate, and depth of cut.
Shearing
Shearing mechanically separates material in a straight line. Shears used include:
- Manual shears (for thin sheets)
- Mechanical shears (for thicker plates)
Shearing Process
Cutting results from two blades working against each other in three phases:
- First Phase: Plastic deformation at the tool-material contact zone.
- Second Phase: Tool penetration and material separation between the blades.
- Third Phase: Material fracture and separation.
Machine Sawing
Machine sawing mechanically cuts material to a specific shape. Types include circular, band, and reciprocating saws. Parameters include tooth size, arrangement, and cutting angle.
Elements:
- Stand: Supports other elements.
- Arquet: Supports the saw blade.
- Motor Mechanism: Provides reciprocating motion.
Reciprocating Saw Kinematic Chain
Movements:
- Reciprocating saw blade movement (via electric motor, pulley, belt, and intermediate shaft).
- Forward movement (via rotating screw shaft).
Sawing Process
Choose the correct blade, mount it, select the cutting speed, firmly clamp the workpiece, adjust the feed rate, turn on the machine, and position the blade.
Drilling
Drilling creates holes with chips using rotating cutting tools (bits). Bits are made of hardened and sharpened steel.
Drill Parts:
- Shank: Connects to the machine.
- Body: The active cutting part.
- Point: The conical cutting end.
Consider drill size, hardness, and sharpness.
Drilling machines (drill presses) typically include:
- Bench: Main support.
- Table: Supports the workpiece.
- Head: Houses the mechanisms.
- Chuck: Holds the drill bit.
Drilling Process
Clamp the workpiece, center-punch the hole location, select the correct drill bit, mount it in the chuck, select the rotation speed, begin drilling, remove the drill slowly, and finish the hole (reaming).
Safety Rules
User Protection: Correct work methods, appropriate clothing, safety equipment, obstacle removal, and machine shutdown when handling workpieces.
Machine Protection: Proper maintenance, guarding of moving parts, safety devices in place, electrical grounding, and regular machine inspections.