cnc machine tools w1

7/28/2019 CNC Machine Tools W1

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CNC Machine Tools


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Introduction to CNC machines.

CNC System elements.

Properties of CNC machines.

Types of CNC machines.

Presentation Contents


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Introduction to CNC Machines

What is CNC ?

Numerical control (NC) is a method of automatically operating amanufacturing machine based on a code letters, numbers and specialcharacters.

The numerical data required to produce a part is provided to a machinein the form of program, called part program or CNC (computernumerical control)

The program is translated into the appropriate electrical signals for inputto motors that run the machine.

A CNC machine is an numerical control machine with the added featureof an on board computer. The computer is referred to as the machinecontrol unit (MCU)


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CNC System Elements

A typical CNC system consists of six elements

1. Part program

2. Program input device

3. Machine control unit

4. Drive system

5. Machine tool

6. Feedback system


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CNC System Elements

Programming Methods

Automatically Programmed Tools (APT)

A text based system in which a programmer defines a series of lines, arcs,and points which define the overall part geometry locations.

These features are then used to generate a cutter location (CL) file.


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CNC System Elements

Programming Methods

Computer Aided Machining (CAM) systems Computer AidedDesign (CAD) Systems

CAD/CAM systems allow for rapid development and modifying of

designs and documentation.

The 3D geometric model produced becomes a common element forengineering analysis (FEA), machining process planning (including CNCpart programming, documentation (including engineering drawings),quality control, and other features.


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Types of CNC machines

Based on Power Supply:Electric or Hydraulic or Pneumatic

Based on Motion Type:Point to Point or Continuous path

Based on Control Loops:Open loop or Closed loop

Based on Positioning System:Incremental or Absolute


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Drives of CNC machine tool

Hydraulic actuator

- High power machine tool

Stepper motor

- Small machines due to limited power and torque

DC motor

Excellent speed regulation, high torque, most widely used


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Motion type of CNC Machine tools

Point-to-point control systems

Causes the tool to move to a point on the partand execute an operation at that point only.

The tool is not in continuous contact with thepart while it is moving.

Examples: Drilling, reaming, punching, boringand tapping

Continuous-Path tool movements

Causes the tool to maintain continuous contactwith the part as the tool cuts a contour shape.

These operations include milling along any linesand angles, milling arcs and lathe turning


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Loop Systems for Controlling Tool Movement

Open loop Control System

Closed loop Control System


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Introduction to Manufacturing

Manufacturing in Modern Context

The making of products from raw materials using various processes,

equipment, operations and manpower according to a detailed plan.

During processing, the raw material undergoes changes to allow it to become a

part of a product(s).

Once processed, it should have worth in the market or a value.

Therefore, it encompasses:

The design of the product.

The selection of raw materials.

The sequence of processes through which the product will be

manufactured.


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Manufacturing can be defined in two ways:

1) Technology - manufacturing is the application of physical and chemicalprocesses to alter the geometry, properties, and/or appearance of a given

starting material to make parts or products.

Manufacturing also includes the assembly of multiple parts to make products

The processes to accomplish manufacturing involve a combination of

machinery, tools, power, and manual labor.

2) Economic - manufacturing is the transformation of materials into items ofgreater value by means one or more processing involve. Therefore,

manufacturing is added value to the material.

Added value By changing the materials shape or properties or by combining

it with other materials that have been similarly altered.


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Two models to define manufacturing:

1) As a technical process

Manufacturing

Process

Raw materials

Product

Profit

M

achinery

Tooling

Power

Labor


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Types of Industries

1) Primary industry Those that cultivate and exploit natural resources.

2) Secondary industry Take the outputs of the primary industries andconvert them into consumer and capital goods.

3) Tertiary industry Constitute with service sector of the economy

Agriculture

Forestry

Fishing

Livestock

Quarries

Mining Petroleum

Aerospace

Automotive

Beverages

Building materials

Chemicals

Computers

Consumer appliances

Electronics

Equipment

Food processing

Banking

Communications

Education

Entertainment

Financial services

Health and medical Government

Hotel

InsurancePRIMA

RYINDUSTRY

SECONDA

RYINDUSTRY

TERTIA

RYINDUSTRY


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Type of Manufacturing Operations

1) Project 1 to 10 units

2) Job Shop 10 to 100 units.

3) Batch 100 to 10,000 units.

4) Mass Above 10,000 units.

Production Quantity: Number of unit produced annually of a particular product

type.Product variety: Different product designs or types that are produced in the plant

[Low production]

[Medium production]

[High production]

Low

Medium

High

Productvariety

Product quantity


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MANUFACTURING

PURCHASING

MACHINERY &TOOLING

PROCESS PLANNING

MATERIALS

PRODUCT DESIGN

PRODUCTION CONTROL

SUPPORT SERVICES

SHIPPING

CUSTOMERSERVICE

MARKETING

SALES


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Classification of Materials

General Classification

Metals and alloys. Polymers. Ceramics Materials. Composites.


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1. Metals

Metals are usually lustrous, ductile, malleable, and good conductors ofelectricity

They are divided into 2 categories:

FERROUS: the group which contains mainly iron (Fe). Iron isthe most important metal in industrialized countries

NON-FERROUS: other metallic materials containing no iron likecopper (Cu) or aluminium (Al)


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2. Polymers

Crude oil supplies the majority of the raw material for the production offpolymers, also called plastics.

Polymers can be divided into 3 categories:

Thermoplastics: usually soft and easy to be recycled Thermosetting plastics: usually stiff and not easy to be recycled Elastomers: flexible (rubbers)


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3. Ceramics

The word ceramic is derived from the Greek word keramikos. The termcovers inorganic non-metallic materials whose formation is due to theaction of heat

Clays, bricks, cements, glass are the most important ones


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4. Composites

Bonding 2 or more materials together changes their properties andcharacteristics

Bonded materials are called Composites

Aluminium Honeycombcomposite panel, lightand strong

Kevlar is used inbullet-resistant vests.Its a tough and lightmaterial

Modern tennisracquets are made ofcarbonfibrecomposite


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Manufacturing Processes

Three categories of Processing operations

1. Shaping operations - Alter the geometry of the starting work material

2. Property enhancing operations Improve physical properties of the

material without changing its shape

3. Surface processing operations Clean, treat, coat, or deposit materialonto the exterior surface of the work


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Solidification Processes

Starting material is heated sufficiently to transform it into aliquid or highly plastic state

Examples: casting for metals, molding for plastics


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Deformation Processes

Starting workpart is shaped by application of forces that exceedthe yield strength of the material

Examples: (a) forging, (b) extrusion


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Material Removal Processes Excess material removed from the starting workpiece so what

remains is the desired geometry

Examples: machining such as turning, drilling, and milling; also

grinding and nontraditional processes

Turning Drilling Milling


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Assembly Operations

Two or more separate parts are joined to form a new entity

Types of assembly operations:

1. Joining processes create a permanent joint.

Examples: welding, brazing, soldering, and adhesive bonding

2. Mechanical assembly fastening by mechanical methods

Examples: use of screws, bolts, nuts, other threaded fasteners;press fitting, expansion fits


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