NON TRADITIONAL MANUFACTURING PROCESSES

NEED:1. HIGH STRENGTH MATERIALS

Development of high strength materials like high strength temperature resistant alloys (HSTR) and Ti led to the development of nontraditional manufacturing processes to machine these materials.

2. ACCURACY AND TOLERANCE:They are mainly affected by the high temperature and residual stress encountered. High temperature developed due to physical contact between the tool and the workpiece in traditional processes led to high heat as a result there may be a non-uniform contraction or expansion in the part size. The residual stress developed may be compressive or tensile. If it is compressive it is advantageous as it will provide a better surface finish whereas if it is tensile in nature it should be reduced. Thus w.r.t NTMP reduced residual stress may be an advantage or a limitation.

3. REDUCED TOOL COST: Tool cost reduces depending on the material

4. PRODUCTIVITY: Production time = (loading + machining + unloading) time. In NTMP tool setup is done only once and tool regrinding is totally eliminated hence time consumed is less and so more productivity.

5. CHIP FORATION:60% of material is wasted as chip in traditional process whereas less chip formation is there in NTMP.

6. COMPLICATED JOBS: Electrode materials like Cu, graphite used in NTMP are produced by traditional manufacturing process which can be used for complicated jobs. Hence the number of processes and tools are reduced.7. HOLDING DIFFICULTY: Due to reduced physical contact less forces are encountered so only less difficulty in encountered in holding8. MAINTANANCE:

No mechanical interaction between the components hence the wear and tear is eliminated

9. COST:Capital cost is high but w.r.t the number of components produced the cost involved is justified.

10. COMPACT AND AUTOMATIONNumber of mechanical parts is reduced and so it is compact. Also automation is achieved with CNC.

Classification:

1. Based on machining process1) Mechanical

Abrasive jet machining (AJM)Abrasive flow machining (AFM)Ultrasonic machining(USM)Water jet machining(WJM)

2) Chemical 3) Electrochemical

Electrochemical grinding(ECG)Electrochemical discharge grinding(ECDG)Electrochemical honing (ECH)

4) ElectrothermalElectro discharge machining (EDM)Laser beam machining (LBM)Electron beam machining (EBM)Plasma arc machining (PAM)Ion beam machining (IBM)

2. Based on forming process (HERF methods)1) electrohydraulic forming2) explosive forming3) magnetic pulse

CLASSIFICATION BASED ON ENERGY SOURCE, TRANSFER MEDIA, MECHANISM OF MATERIAL REMOVAL

Group Process Energy source Transfer media

Mechanism

Mechanical USM Electricity Abrasive slurry

Erosion, abrasion

WJM Hydraulic Water ErosionAJM Hydraulic Abrasive

slurryErosion, abrasion

Chemical CHM Chemical reaction Chemicals Reaction

Electro chemical

ECM Electrical and chemical reaction

Electrolyte Ion displacement

ECG Electrical ,chemical reaction + mechanical

Electrolyte Ion displacement + abrasion

Thermal EDM Electricity Dielectric fluid

Erosion

LBM Electricity Light beam Radiation and vaporization

EBM Electricity Electrons VaporizationIBM Electricity Ionized gas IonizationPAM Electricity Ionized gas Ionization

Factors governing the choice of NTMP

1. Type of material: material must be efficient and conductivity of material determines the MRR.

2. Accuracy3. surface finish4. Cost effectiveness:coupled with accuracy and surface finish.5. No of Components: determined by cost effectiveness6. Frequency of design changes: depending on design the manufacturing process

changes and hence machine cost increases7. Job complication: less number of variables controls the surface finish of the job.8. Productivity9. Noise level10. Cleanliness

Ultrasonic machining process(USM)Invented in 1950 by Henry Balsmouth and fully developed in 1975. suitable for brittle materials. It is a safest process.. here erosion mechanism is used.

Principle: High frequency electrical signals are applied to the transducer which converts it into vibrations which is transferred to the tool holder which amplifies it and the tool attached to the tool holder transfer the mechanical motion to the abrasive particles in the abrasive slurry which results in impact force on the workpiece and the workpiece material gets detached. Vibrations are created above 20 khz.

Set up:1. power source:40 to 2400 W2. transducer:

1) magnetostrictive transducer:*Conversion efficiency is less (20-30 %)*Electrical energy is converted into magnetic and then into another form of energy*can be used above 900 W*Materials: Nickel, Alfer

2) Piezoelectric:*Conversion efficiency is more (96%)*electrical energy converted into another form

*used with higher power machines but only upto 900 W*materials: quartz, lead zirconate titanate

3. tool holder*for holding tool and amplifying the vibrations*amplification can be done by varying the cross section of input and output*outer dimension is constant and inner dimension is varied else the cross section is variedTypes:1)Non amplifying tool holder 2)Amplifying tool holder – exponential type, tapered type, stepped typeDesign of tool holder: *Frequency is high which is a cyclic load and so may result in fatigue which necessitates the roper design of tool holder*Materials: Titanium, monel, stainless steel

(best acoustic properties)Ti- best material but high cost also fabrication and machining is difficultMonel-next best material , best acoustic property than Ti, easily brazed, less costStainless steel-for low power machines and poor elastic properties

*tool holder shouldn’t be permanently fastened to other components because ultrasonic welding may occur between fastened components.so tool holder is fastened with tool or amplifier using loose screws and copper wash to get cushioning and damping effect and avoid ultrasonic welding.4. tool: replica of tool is produced in the workpiece. So high surface finish of tool

equivalent to that of workpiece is necessary. Materilas : Ductile- Stainless steel, mild steel and brass

5. tool feed arrangement:Types:1)Mechanical 2)Pneumatic

Other arrangements:1) Counter weight with rope and pulley2) Counter weight with lever and fulcrum3) Electric solenoid control4) Spring control5) Hydraulic/pneumatic control6) Control with stalled motor

6. abrasive slurry* Abrassives are used with fluid medium* Abrasives: boron carbide, silicon carbide, borosilicon carbide, alumina, lass dust, diamond dust* Fluid medium: water/kerosene* fluid medium – 30-40% upto 60% but theoretically 50 %* pumping system with nozzle arrangement is employed with some electrical arrangement. Mixing chamber may be used in bigger machines for uniform mixing of abrasives and fluid.

* number of abrasives in the tool determines the MRR

abrasive fluid should be of high wetting nature, non toxic, non corrosive (water used only if corrosion resistant ) , act as coolant, should be thermally conductive.

Process Parameters:1. Power: Achieved by combination of tool and tool holder at its natural frequency. Maximum power is limited by natural frequency.2. Amplitude: As per Miller and Rosenberg’s statement the MRR increases with amplitude as the force applied increases with amplitude 3. Frequency: As frequency increases force applied on the particles increases hence MRR increases4. Grain size: If gap between tool and workpiece s minimum the grainsize is more and MRR is more but surface finish is less5. Particle velocity: Particle velocity and hence MRR increases with increase in amplitude and frequency.6. Fluid medium viscosity:

As viscosity decreases the flow of abrasive particle between tool and workpiece is poor and the new particles entering the region is less and so MRR increases

7. Abrasive slurry concentration:Theoretically 50% but generally 30-40 upto 60% is used.

8. Static load or feed force:It is the Force given by tool on workpiece. It Supports the action on the particle. Force applied on the particle cannot increase beyond a point. Governed by hydraulic/pneumatic/handGiven to counteract the force of abrasive particles i.e. all the forces are applied to workpiece and thus increasing the efficiency.As static load increases the gap between tool and workpiece decreases and so crushing occurs and MRR decreases.static load maintains the MRR obtained from other parameters. When increased beyond appoint only it reduces the MRR.

9. tool work hardness ratio10. surface area of tool