Intro to NC Machining

Intro to NC MachiningIntro to NC Machining

A Cuyler , Baehr Production!

What is this NC Machining All What is this NC Machining All about?about?What is it?

How can it be set up?Let’s take a look.

NC

CNC

DNC

NC-Numerical Control

A Programmed path is loaded into a machine then executed by a series of codes the machine

can understand.

CNC- Computer Numerically controlled

A Dedicated Computer acts as the controller for each tool.

Computer

MachineTool

Computer

MachineTool

Computer

MachineTool

DNC- Distributed Numerically controlled

One central Computer controls all other Machine Tools on the factory floor.

CentralComputer

Machine Tool

MachineTool

Machine Tool

Machine Tool

Which type of NC system do Which type of NC system do we use in class?we use in class?

Goals of NC MachiningGoals of NC Machining

1. Increase Production

2. Improve the Quality and Accuracy of parts

3. Stabilize Manufacturing Costs

4. Manufacture and assemble complex parts quickly

Single items produced by craftspeopleSingle items produced by craftspeople

Eli Whitney (Cotton Gin) - Interchangeable PartsEli Whitney (Cotton Gin) - Interchangeable Parts

Engineer designed parts for production (tolerances)Engineer designed parts for production (tolerances)

WW II - development of servo motors (electrically WW II - development of servo motors (electrically aimed guns) aimed guns) Military products created the need to Military products created the need to produce precision quickly and accurately.produce precision quickly and accurately.

Servo motors applied to machine tools as a result.Servo motors applied to machine tools as a result.

Timeline of NC MachiningTimeline of NC Machining

1945- University of Pennsylvania- ENIAC to assist with Engineering calculations.

1945- Parsons corporation awarded USAF contract

1952- Parsons corporation subcontracted with MIT to develop first NC machine.

1960’s- NC machines become affordable and common in industry to produce parts.

Timeline ContinuedTimeline Continued

1970’s- Programs stored on Punch tapes and Cards. Programmable controllers replace relays.

1980’s- Computer assisted Part Programming- computer is used for translating data and performing necessary calculations, creates punch tape.

1990’s- CNC And DNC become widely used in industry. Punch cards become obsolete.

Currently 85 percent of machine tools produced are run by CNC.

Timeline ContinuedTimeline Continued

Punch Tape

ENIACENIAC

First NC Machine at MITFirst NC Machine at MIT

TodayToday

Advantages Of CNCAdvantages Of CNC

Increased productivity after programming is Increased productivity after programming is completedcompleted

Reliability - reduces human errorReliability - reduces human error

Often eliminates need for special jigs and Often eliminates need for special jigs and fixturesfixtures

Makes possible the machining of complex Makes possible the machining of complex shapes requiring simultaneous 3 axis motionshapes requiring simultaneous 3 axis motion

AdvantagesAdvantages

Single part and production runs can be Single part and production runs can be programmed and machined with minimum programmed and machined with minimum effort and cost.effort and cost.

Programs can readily be altered and re-runPrograms can readily be altered and re-run

Reduced inspection costs (more reliable)Reduced inspection costs (more reliable)

Once programming, setup and verified the Once programming, setup and verified the equipment can be operated by a less skilled equipment can be operated by a less skilled operator.operator.

DisadvantagesDisadvantages

Initial cost of CNC machine toolsInitial cost of CNC machine tools

Servicing of equipmentServicing of equipment

Larger machines require more spaceLarger machines require more space

Personnel must be trained in the Personnel must be trained in the programming and operation of this programming and operation of this equipment.equipment.

All videos Copywrite CNC WorkshopAddison Wesley Longman 1999

DefinitionsDefinitions

FMSFMSFixed Manufacturing SystemsFixed Manufacturing Systems- -

An automated process that can not be An automated process that can not be reprogrammed. The system is most likely reprogrammed. The system is most likely replaced.replaced.

Flexible Manufacturing SystemFlexible Manufacturing System--

An automated system that can be An automated system that can be reprogrammed reprogrammed and broken apart to complete and broken apart to complete other tasks. This other tasks. This type of system is initially type of system is initially expensive but pays off expensive but pays off in the long run.in the long run.

DefinitionsDefinitions

NC - A method of accurately controlling the NC - A method of accurately controlling the operation of a machine tool by a series of operation of a machine tool by a series of coded instructions, consisting of numbers, coded instructions, consisting of numbers, letters of the alphabet, and symbols that letters of the alphabet, and symbols that the machine control unit can understand.the machine control unit can understand.

MCU - Machine Control Unit - decodes NC MCU - Machine Control Unit - decodes NC codes to drive and monitor servo motor codes to drive and monitor servo motor movements.movements.

DefinitionsDefinitions

CAM Package: CAM Package: (Computer Aided (Computer Aided Manufacturing) A software solution Manufacturing) A software solution capable of generating NC code from capable of generating NC code from assigned tool paths applied to part assigned tool paths applied to part geometry.geometry.

Control SystemsControl SystemsOpen loop systemOpen loop system - servo motor driven by - servo motor driven by pulses without feed back encoders.pulses without feed back encoders.Closed loop systemClosed loop system - servo motor is driven by - servo motor is driven by electrical pulses. An encoder provides electrical pulses. An encoder provides feedback to verify machine movements.feedback to verify machine movements.

Punched Paper TapePunched Paper Tape