NC TECHNOLOGY

NUMERICAL CONTROLNumerical control (NC) refers to the automation of machine tools that are operated by abstractly programmed commands encoded on a storage medium

The first NC machines were built in the 1940s and '50s.

These early servomechanisms were rapidly augmented with analog and digital computers, creating the modern computer numerical controlled (CNC) machine tools that have revolutionized the design process.

ANLOG OR DIGITAL NPUT

CNC MACHINE

FOR TURNING

OPERATIONS

CNC TURNING CENTRE

SIEMENS CNC PANEL

`

• PROGRAM OF INTRUCTIONS

• MACHINE CONTROL UNIT

• MACHINE TOOL OR OTHER CONTROLLED PROCESS.

BASIC COMPONENTS OF NC SYSTEM

• It is the detailed step-by step set of directions which tells the machine tool what to do.

• It is coded in numerical or symbolic form on some type of input medium that can be interpreted by the controller unit.

• The most common input medium today is 1-inch wide. Input method can be manual or by means of direct link with a computer , called direct numerical control or DNC.

PROGRAM OF INTRUSTIONS

• .

PUNCHED TAPE

SPROCKET HOLES

PROGRAM OF INTRUCTIONS

• It is part of the NC system which performs useful work.

• It includes the cutting tools, work fixtures, and other auxiliary equipment needed in the machining operation..

MACHINE TOOL

THE NC PROCEDURE• PROCESS PLANNING

• PART PROGRAMMING

• TAPE PREPARETION & VERIFICATION

• PRODUCTION

PROCESS PLANNING

This step is referred to as process planning and it is concerned with preparation of route sheet.

The route sheet is a listing of the sequence of operations which must be performed on the work part.

PART PROGRAMMING

Part programmer plans the process for the portions of the job to be accomplished by NC.

• They are responsible for planning the sequence of machining steps to be performed by NC and to document these in a special form.

TAPE PREPATION AND VERIFICATION

A punched a tape is prepared from the part programmer’s NC process plan.

After the tape has been prepared, a method is usually provided for checking the accuracy of the tape

The “Acid Test” of the tape involves trying it in and out on the machine tool to make the part. A foam or a plastic material is sometimes used off this tryout.

PRODUCTIONThe final step in the NC procedure is to use NC tape in

production.

This involves ordering the raw work parts, specifying and preparing the tooling and any specific fixturing that any be required and setting up the NC machine tool for the job.

When the part is completed the operator removes it from the machine and loads the next.

NC CO-ORDINATE SYSTEM

• The purpose of cordinate system is to provide a means of locating the tool in relation to the workpiece.

• Depending on the NC machine, the part programmer may have several differnet options avalable for specfying this loaction.

x

-x

-y

yz

-zMachine

table

NC MOTION CONTROL SYSTEM

• point-to-point

• Straight – cut

• CONTOURING NC

Point to Point

tool

workpiece

workpiece

Cnc drill

STRAIGHT CUT

tool

workpiece

CONTOURING

CONTOUR MADE BY A

CNC MACHINE ON

FOAM

APPLICATIONS OF NUMERICAL CONTROL

• MOST WIDELY USED IN METAL CUTTING INDUSTRIES

• MILLING DRILLING,BORING,TURNING ,GRINDING AND SAWINGAND RELATED PROCESS.

APPLICATIONS OF NUMERICAL CONTROL

• In addition to metal machining, numerical control has been applied to a variety of other operations..

• Press working machine tools,Cloth cutting,Automatic riveting,Wire-wrap machines,Welding machines,

• Inspection machines,Automatic drafting.

ADVANTAGES

• Reduced non-productive time. • Reduced fixturing. • Reduced manufacturing lead time. • Greater manufacturing flexibility. • Improved quality control.

DISADVANTAGES

• Higher investment cost. • Higher maintenance cost. • Finding and/or training NC personal