Ch 25.

Chemical Machining Processes

1. Chemical Milling 2. Chemical blanking 3. Chemical engraving 4. Photochemical machining

Identify 2 significant disadvantages of electrochemical machining

1. Cost of electrical power 2.Cost of disposal of electrolytic sludge

How to apply Maskant

1. Cut and peel 2. Photographic resist 3. Screen resist

Advantages of ECG

1. Deplating responsible 95% of metal removal. 2. Because machining is mostlry by electrochemica laction, grinding wheel lasts much longer.

6 Types of Thermal Energy Processes

1. Electric discharge machining 2. Electric discharge wire cutting 3. Electron beam machining 4. Laser beam machining 5. Plasma arc machining 6. Conventional thermal cutting processes.

Two main processes Electric Discharge Processes

1. Electric discharge machining 2. Wire electric discharge machining

3 Types of Electrochemical Machining

1. Electrochemical Machining (ECM) 2. Electrochemical Deburring (ECD) 3. Electrochemical Grinding (ECG)

4 classification of nontrad processes

1. Mechanical 2. Electrical 3. Thermal 4. Chemical

Importance of Nontraditional Processes

1. Need to maching newly developed metals and non-metals. 2. Need for unusual and/or complex part geometries

Advantages of Water Jet Cutting (WJC)

1. No crushing or burning of work surface 2. Minimum material loss 3. No environmental pollution 4. Ease of automation

4 types of Mechanical Processes

1. Ultrasonic 2. Water jet cutting 3. Abrasive water jet cutting 4. Abrasive jet machining

Steps in Chemical Machining

1. cleaning - ensure uniform etching 2. masking - a maskant (resist, chemically resistant to etchant) is applied to portions of work surface not to be etched. 3. etching - part is immersed in etchant. 4. demasking - maskant removed

Applications of USM

1. hard,brittle work materials 2. certain metals(steel, titanium) 3. Non-round holes

Applications of ECG

1. sharpening of cemented carbide tools 3. Grinding of surgical needles, other thin wall tubes, and fragile parts

Applications of Nontraditional Processes

1. small holes 2. holes with large depth to diameter ratios 3. holes are not round 4. Narrow slots in slabs and plates 5. Micromachining 6. shallow pockets 7. contoured shapes for mold and die applications

Ultrasonic Machining

Abrasives contained in a slurry are driven at high velocity against work. Shape of tool is formed in part

Electrochemical Deburring (ECD)

Adaptation of ECM to remove burrs or sharop corners on holes in metal parts produced by conventional through-hole drilling.

Applications of Abrasive Jet Machining

Applications: deburring, trimming, deflashing, cleaning, and polishing. Work materials: thin flat stock of hard, brittle materials.

Applications of Water Jet Cutting (WJC)

Automated by CNC. Used to cut narrow slits in flat stock . Not suitable for brittle materials.

What are the 3 methods of performing the masking step in chemical machining

Cut and peel, screen resist, photographic resist.

LBM Applications

Drilling small diameter holes. Generally used on thin stock.Work materials: metals with high hardness and strength, soft metals, ceramics, glass.

Electrochemical Machining Processes

Electrical energy is used in combination with chemicals reactions to remove materal.

Application of EBM are limited to metallic work materials. (True,False)

False. Can be used on any material.

(T, F) In ultrasonic machining, material removal rate decreases with inc frequency and amp vibration

False. Removal rate increases with increasing frequency and amplitude of vibration.

Abrasive Jet Machining (AJM)

High velocity stream of gas containing small abrasive particles.

Wire EDM Applications

Ideal for stamping die compons

Chemical Milling

Is chemical machining that does what traditional machining does

ECM Operation

Material is deplated form anode workpiece and transported to a cathode tool in an electrolyte bath.

Electric Discharge Processes (EDM)

Metal removal by a series of discrete electrical discharges (sparks) causing localized temperatures high enough to melt or vaporize the metal.

Maskant materials

Neoprene, PVC, polethylene, an other polymers.

EDM Operiations

One of the most widely used non trad processes. Shape of finished work produced by shape of electrode

Notes on Abrasive Jet Machining (AJM)

Performed manually. Finished process rather than cutting process.

Nontraditional Machining

Remove excess material by various techniques involving mechanical, thermal, electrical, or chemical energy

Equation for Rate of material removal rate for EDM machining

Rmr = 664 * I* T^-1.23 Rmr = metal removal rate. I = disharge current. T = melting temp.

Electrochemical Grinding (ECG)

Special form of ECM in which grinding wheel with conductive bond material augments anodic dissolution of metal part surface

Wire EDM

Special form of EDM uses small diameter wire as electrode to cut a narrow kerf in work.

EDM Applications

Tooling for many mechanical processes: molds, extruction dies, wire drawing dies.

Etchant

Typ acid. Depends on what materials, depth and rate of material removal, and surface finish requirements.

Water Jet Cutting (WJC)

Uses high pressure, high velocity stream of water directed at work surface for cutting

Electron Beam Machining

Uses high velo stream of electrons focused on workpiece surface to remove material by melting and vaporization.

Laser Beam Machining (LBM)

Uses the light energy from a laser to remove material by vaporization and ablation.

Equations in ECM

V = C * i * t V = volume of metal removed, C = specifica removal rate of work material, i = current, and t = time.

Thermal Energy Processes - Overview

Very high local temps. Material is removed by fusion or vaporization.

Abrasive Water Jet Cutting (AWJC)

When WJC is used on metals, abrasive particles are added to the stream.

Operation of Wire EDM

Work is fed slowly part wire along desired cutting path, like a bandsaw operation

Work Materials in EDM

Work materials must be electrically conducting. Hardness and strength of work material are not factors in EDM.

Application of EBM

Works on any material. Ideal for drilling small holes and slots. Good for holes with very high depth to diameter ratio.

Cut and peel masknt method

applied over entire part.

Chemical Blanking

chemical machining process that penetrates through the thickness of a piece of sheet metal in order to produce a blank or slug; material is removed by dissolution instead of shearing; it can produce more complex and smaller shapes than sheet metal shearing. Very thin

The metal removal rate in EDM machining depends on which 2 variables

discharge current and melting temperatre.

undercut in CHM

etching occurs downward and sideways under the maskant.

Screen Resist Method

maskant applied by silk screening methods. painted through a silk or stainless steel mesh containing stencil onto surface

Photographic Resist Method

masking materials contain photosensitive chemicals. Maskant is applied to work surface and exposed to light through negative images.

Chemical Machining (CHM)

material removal through contact with a strong chemical etchant

Photochemical Machining

uses photoresist masking method.