Lecture 1 introduction to ntm process

transcript

• Need for NTM processes

• Classification of NTM processes

• Process capability and the operating parameters for NTM processes

• Overview of Manufacturing sector • Comparison with the conventional processes

Overview

Dimensional Range

Precision or miniaturization?

Very popular and wide applications Sometimes only feasible solutions

Need of NTM

Un-conventional Non-traditional Un-traditional= =

Machining

Manufacturing

Un-conventional ?

Need of NTM Limitations of Conventional processes

• Machining invariably uses K.E., i.e., forces and motions.

– Forces are accompanied by friction, heat, vibration,deflection etc. These lead to tool wear, inaccuracy(precise and miniature features not possible), poorsurface finish, surface integrity (surface cracks,residual stresses, hot spots), low MRR.

– Motions limit the shape and size of the realizablefeatures.Eg.: Square holes, small but deep holes required inturbine blades, simple features in deep areas were therotating tool cannot reach.

NTM use simpler motions with special tools.

Need of NTM HSHTR (turbine blades, aerospace alloys, refractory metals)Un-usual and complex part geometriesAvoiding surface damage

Shape Complexity

Metals and Non-metals machining

Avoid Surface Damage

Precision and Miniaturization

Miniaturization Productivity

• Non circular blind holes• Normal size but deep

hole drilling• Micro drilling• Three dimensional

contour in a die• Elliptical piston machining

& finishing

• Inaccessible/ critical area de-burring

• Super finishing of inner lateral surface of a shell

• Finishing of fragile components

• Holes along a curved axis• Micro & Nano

components of special materials

AND MANY MORE

Need of NTM

A group of processes that remove excessmaterial by various techniques involvingmechanical, thermal, electrical, or chemicalenergy (or combinations of these energies)but do not use a cutting tool and its physicalcontact with the work piece in theconventional sense

NTM DEFINED

Absence of tool-workpiece contact or relative motion, makes the process a nontraditional

Machining Accuracies•Nanomachining processes include atom, molecule, or ion beam machining, and atom or molecule deposition.

•These techniques can achieve 1-nm tolerances that can be measured using a scanning electron microscope (SEM), a transmission electron microscope, an ion analyzer, or electron diffraction equipment

Classification of Conventional Processes

Classification of NTM processes

• Mechanical - erosion of work material by a high velocity stream of abrasives or/& fluid is the typical form of mechanical action

• Electrical - electrochemical energy to remove material (reverse of electroplating)

• Thermal – thermal energy usually applied to small portion of work surface, causing that portion to be removed by fusion and/or vaporization

• Chemical – chemical etchants selectively remove material from portions of workpiece, while other portions areprotected by a mask

NTM Processes

Single Action Hybrid

Classification of NTM processes

Single Action Mechanical and Chemical and electrochemical Processes

Single Action Thermal Processes

Hybrid Processes

Mechanism of processesEnergy type Mechanism of

material removal Energy source Processes

Mechanical Plastic shearMechanical motion of tool /job

Conventionalmachining

Mechanical /Fluid motion AJM, USMElectrochemical Ion displacement Electric current ECMMechanical and electro-chemical

Plastic shear and iondisplacement

Electric current andmechanical motion ECG

Chemical Corrosive reaction Corrosive agent CHM

Thermal Fusion and vaporization

Electric spark EDMHigh speed electrons EBMPowerful radiation LBMIonized substance IBM, PAM

Hybrid NTM processes

Characteristics of NTM processes Process Characteristics Operating

parametersForm of Energy

CHM • Sharpening of hardmaterial• Used as honing process• Higher MRR thangrinding

Chemical propertiesof the reagent

Etching

EDM • Shaping and cuttingcomplex parts made ofhard materials• White layer• Expensive tooling andequipment

V = 50-380, A = 0.1-500,MRR ~ 300mm^3/min0.03 and above

Series of sparks

USM • Brittle fracture• Abrasive embedding

V=220, A= 12 ampAC, Gap = 0.25

Small amplitudeand high frequency

WEDM • Simple or complexcontour cutting• Expensive equipment

Varies with materialand thickness

Series of sparks

LBM • Cutting and holemaking on thin material• HAZ• No need of vacuum• Expensive equipment• Low efficiency

V= 4500, air medium

0.5-7.5 m/min

PHOTONS

EBM • Small hole and slotmaking• Need vacuum• Expensive equipment• HAZ

V = 1,50,0001-2 mm^3/min

KE of electrons

AJM • Suitable for all material• Tapered surface

generated• Effect of standoff

distance

V = 110, I = 1.5 A,Gap = 0.76

Abrasive propelledat in high speed air

IBM • Costly process• Less efficiency

• Very slow

High velocity ions (more energy)

PAM • HAZ• Rough surface• Heavy work

V= 100, I=500 DCGap= about 150

PLASMA

ECM • Less tool wear• Oxide layer

V =10, I=10,000 AElectrical and

Chemical

Shape applicationsFeature Suitable processes

Holes • For holes not less than 0.130 mm; EBM, EDM, LBM• Large and deep holes; EDM and ECM (well above 20 L/D)• For improving the geometry of holes, conventional processes likereaming and boring can be combined with the processes

Throughcavities

• USM, ECM, and EDM• Trepanning tool• Generally EDM and USM and suitable for precision small cavitieswhile ECM is best for large cavities

Pocketing • Same as a through holes but have a flat at the bottom• Trepanning tool usage is not possible• ECM, CHM, and EDM are the principle processes• CHM is suitable for large surface area

Arrayed structures

• Arrayed microholes- beam processes• Arrayed protrusions- EDM, ECM, CHM

Taper ECM is good as less tool wear occurs

Material applications

Material applicationsProcess applicability

USM AJM ECM CHM EDM EBM LBM PAM

Metals and Alloys

Aluminum C B B A B B B A

Steel B B A A A B B A

Super alloys C A A B A B B A

Titanium B B B B A B B B

Refractories A A B C A A C C

Non-Metals

Ceramic A A D C D A A D

Plastic B B D C D B B C

Glass A A D B D B B D

A Good

B Fair

C Poor

D Inapplicable

Process variants Basic process Variant process

USM • Ultrasonically Assisted Machining (UAM)• Rotary ultrasonically Assisted Machining (RUM)

AJM • Abrasive Flow Machining (AFM)• Orbital Grinding (OG)• Abrasive Water Jet Machining (AWJM)

ECM • Electro-Chemical Grinding (ECG)• Electro-Chemical Discharge Grinding (ECDG)• Electro-Chemical Deburring (ECD)• Electro-Chemical Honing (ECH)• Shaped Tube Electrolytic Machining (STEM)

EDM • Wire Electrical Discharge Machining (WEDM)• Wire Electrical Discharge Grinding (WEDG)

CHM • Chemical Milling (CHM)• Chemical Engraving (CHE)• Chemical Blanking (CHB)• Photo-Chemical Machining (PCM)

Limitations of conventional processes• Machining processes that involve chip formation have

a number of limitations– Large amounts of energy– Unwanted distortion– Residual stresses– Burrs – Delicate or complex geometries may be difficult or

impossible

• Hybrid processes• Automation• Micro-fabrications• Proper decision support by use of modern tools (FEA,

AHP etc.).

Advances in NTM processes

– Complex geometries are possible– Extreme surface finish– Tight tolerances– Delicate components– Easy adaptability for automation– Little or no burring or residual stresses– Brittle materials with high hardness can be

machined– Microelectronic or integrated circuits are possible

to mass produce– Manufacturing otherwise impossible shapes– Production of functionally gradient materials

Advantages of NTM

• Creating, improving unit operations• Scaling up/down manufacturing capabilities• Novel manufacturing concepts• Understanding, responding to health, safety,

environmental issues• Process monitoring and control• “Application – Process- Material” system development• Metrology• Characterizations

Research issues in NTM

Typical Parts Machined

Nonmetallic and tiny parts by WJM Metallic and very large

Ceramic Parts Bullet proof glass Rack and Pinion

EDM and WEDM

Various work samples machined by USM

1- The first picture on the left is a plastic sample that has inner grooves that are machined using USM.

2- The Second picture (in the middle is a plastic sample that has complex details on the surface

3- The third picture is a coin with the grooving done by USM

EDMing of insulating ceramics

EDMing of curved hole

Powder mixed EDM

Lecture 1 introduction to ntm process

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