Abrasive flow machining, chemo-mechanical polishing, magnetic abrasive finishing, magneto
rheological finishing, magneto rheological abrasive flow finishing their working principles, equipments,
effect of process parameters, applications, advantages and limitations.
2. INTRODUCTION
• The metal is removed from the work piece
through controlled etching or chemical attack
of the work piece material in contact with a
chemical solution
3. ELECTRO- CHEMICAL MACHINING
In this method , the metal is removed by
ion displacement of the work piece material in
contact with a chemical solution
7. CLEANING
• Trichloroethylene vapour
Or
• Solution of mild alkaline at 85 – 90 degree
Celcius
The above solutions are used to remove oil and dust
from the work piece
10. Dipping in Chemical solution
• Caustic soda - Aluminium
• Hydrochloric acid and nitric acid – steel
• Iron chloride – stainless steel
The metal is removed by the chemical conversion
of metal into metallic salt
Dipping time will varies from amount of material to
removed from work piece
11. Stirring & Heating
For obtain uniform depth of metal
removal, temperature control and stirring of
chemical reagent is important
12. washing
• To prevent further reaction after require
shape obtained, the metal is cleaned properly
18. Photo resists
Maskants
• For close tolerance and
dimensional accuracy
needed places
• Paint spray type work is
done for preparing
master copy
• The master drawing is
photographed and it
reduced to the size of
the working material
19. Photo resists
Maskants
• Then the material is
placed over the work
piece.
• And it exposed to UV
light to harden
• Then its dipped in
organic solution for
maskanting.
• Finally it dipped in
chemical solution for
machining
21. CLASSIFICATION OF CHEMICAL MACHINING
PROCESSES
CONTOUR MACHINING
• Material is etched entirely on the workpiece
• Used for cutting parts from thin sheet metals or foil
sheets
• Material is etched selectively on the workpiece
• Used for removing metal from thicker workpiece
22. ADVANTAGES OF CHM
• Burr-free components are produced.
• Most difficult to machine materials can be
processed.
• High surface finish is obtained.
• Stress free components are produced.
• Hard and brittle materials can be machined.
• Complex contours can be easily machined.
• Any metal can be machined.
• There is no need of skilled labour.
• Both faces of workpiece can be machined
simultaneously.
23. DISADVANTAGES OF CHM
• Since the process is slow, metal removal rate is
low.
• Manufacturing cost is high.
• Large floor area is needed.
• It is not possible to produce sharp corners.
• Workpiece thickness can be machined, is limited.
24. APPLICATIONS OF CHM
• Chemical machining process is applied in great
number of usages where the depth of removal is
critical to a few microns and the tolerances are
close.
• The major application of chemical machining is in
the manufacture of burr free components.
26. PRINCIPLE
Faraday’s Law of Electrolysis
FIRST LAW
Amount of metal deposited directly
proportional to quantity of electricity
SECOND
LAW
Amount of Change in metal is directly
proportional to its electrochemical
equivalent of the material
27. Basic electroplating concept
• Things to be coated to Negative terminal (Cathode)
• Electrode is connected to positive Terminal
(Anode)
28. ECM – REVERSE OF
ELECTROPLATING
Our objective is - Metal should be removed
from the work piece
So work piece to positive terminal (Anode)
Tool is connected to Negative Terminal (Cathode)
When current is passed , the work piece loses metal
and the dissolved metal is carried out by circulating
an electrolyte between them
29. .
TOOL
- Titanium , stainless steel,
brass and copper
ELECTROLYTE
-Sodium Nitrate
SERVO MOTOR
- To Control Tool Feed
Rate
Tool and Work piece
Gap 0.05 – 0.5mm
30. ELECTROCHEMICAL MACHINING (ECM)
• Reverse of electroplating
• Work material must be a conductor
• Material removal by anodic dissolution
• Electrical energy + chemical energy
Voltage 5-30 volts
Tool Velocity 30 – 60 m/s
Current 20 -300A/cm2
36. FACTORS AFFECT THE CURRENT FLOW
• Gas evolution (H2) at the electrode surface may reduce
the current flow.
• Polarizes ionic layers may build up at electrode, causing
large voltage drop neat the surfaces.
• When electrolyte is heated more, it results in boiling.
It automatically reduces the electrolytic action.
38. ELECTROLYTE
• It carries the current between tool and the
workpiece.
• It cools the cutting zone which becomes hot
due to the flow of high current.
• It removes products of machining from the
cutting zone.
46. PRINCIPLE
Machining operation by the combined action of
Electro-chemical effect and conventional
grinding operation
90 % - Metal removed by chemical Action
10 % -Metal removed by Grinding Action
49. Grinding Wheel – made up of fine Diamond
wheel
Grinding wheel speed
900 – 1800 m/min
50. Process Parameters
• Current density
– 100 to 200 A/cm², DC voltage= 3 to 30V
• Electrolyte
– 0.150 to 0.300 kg/litre of water, Temp= 15°C to 30°C
• Feed rate
– Maximum depth of cut for grinding wheel = 2.5mm
• Grinding wheel speed
– 900 – 1800 m/min
56. Work Piece + Ve Terminal (Anode)
Tool -Ve Terminal (Cathode)
Gap = 0.075 to 0.125 mm
Electrolyte Supply = 112 lit/min, Pressure=1.05 N/mm²
Voltage = 25 V
Tolerance = 0.012 to 0.005 mm
57. MRR is 10 times faster than conventional internal
Grinding
Less tool Wear
Less Pressure is required between Honing tool and
work piece
Burr Free and Stress free Components are produced
60. Process
• Designed to remove burrs or to round sharp
corners on metal workpieces by anodic
dissolution method.
• The hole in the work part has a sharp burr of
the type that is produced in a conventional
through-hole drilling operation.
61. • The electrode tool is designed better to focus
the metal removal action on the burr.
• Surface portions of the machining tool not
being used for machining are insulated.
• The electrolyte material flows through the
hole to carry away the burr particles.