Machine Tools: Types, Components, and Machining Processes

Machine Tools: Function and Basic Components

Machine tools substitute manual action with a series of mechanical movements, reducing and simplifying human effort.

Basic Machine Tool Components

1. Motor: Converts electrical energy into rotary motion, imparting it to the working axis/axes through transmission systems.
2. Bed: The machine's base, supporting and assembling various components. Typically made of cast iron, it usually has guidelines for the movement of kinematic parts.
3. Kinematic Chain: Includes elements providing transmission and advancement of the workpiece or tool movement.
4. Headstock: Incorporates the work axis/axes and a gearbox to regulate speeds and movements of the tool or workpiece.
5. Spindle: Holds the tools or machined parts, using appropriate fasteners and accessories specific to each task and machine or tables.
6. Carriages: Enable tool or workpiece displacement. Mounted on the bed or overlapping, they can be manually or automatically controlled.
7. Control and Automation Systems: Allow automatic machine operation, activated by pneumatic, hydraulic, or electric systems.
8. Cutting Fluid Circuit: Facilitates machining conditions through fluid conduits.

Modern Machine Tool Systems

Current systems often integrate Computer-Aided Manufacturing (CAM) to design and machine workpieces. Machines can be classified by:

• Material shaping: For cold or hot plastic shaping.
• High-pressure shaping: For hot shaping with significant pressure.
• Material removal: Using a cutting tool.

Main Types of Machine Tools

Those used for plastic deformation and material removal are most common. Material removal machines, with rectilinear or circular motion, are classic and widely used. All are based on the same principles, but the material cutting method varies per machine type.

Workpiece Machining Process

1. Raw material path
2. Cutting excess material
3. Grinding and honing to specified dimensions
4. Surface treatment and finishing of faces

Basic Machining Movements

During machining, the tool, workpiece, or both have a working movement enabling material cutting.

Cutting Movement

Produces material removal. It can be circular or rectilinear, involving either the tool or the workpiece.

Cutting Speed

Expressed in meters/minute. Calculated as: v = (π * D * N) / 1000, where:

• v = cutting speed (m/min)
• D = diameter of tool or workpiece (mm)
• N = revolutions per minute (RPM)

Feed Movement

Uniform translation of the tool or workpiece during machining, usually rectilinear.

Feed Rate

The distance the tool travels relative to the workpiece (or vice versa) in a revolution or pass. Calculated as: a = f * N, where:

• a = feed rate (mm/min)
• f = feed per revolution or pass (mm/rev or mm/pass)
• N = revolutions per minute (RPM)

Depth of Cut

Allows gradual material removal in each pass, generally rectilinear, involving either the tool or workpiece.

Milling Machine Components

A milling machine is a key machine tool with specific parts:

• Stand or Body: A vertical cast iron body resting on a base containing coolant.
• Spindle: Holds the cutting tool, adjustable horizontally or vertically depending on the workpiece.
• Table Assembly: Cast iron carriages allowing workpiece movement in three directions (longitudinal, transverse, vertical).
• Knee: Moves vertically on the column, guiding the saddle and table.
• Saddle: Moves transversely on the knee's guides.
• Worktable: Moves longitudinally, with a flat top and T-slots for clamping.

What is Lapping?

Lapping is a finishing process that removes small amounts of material from previously machined surfaces using a circular cutting tool called a lapping plate to correct defects and improve surface finish.