Unit 4 ADVANCED NANO FINISHING PROCESSES
- 1. UNIT -4 CHEMICAL AND ELECTRO-CHEMICAL ENERGY BASED PROCESSES
- 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
- 4. Examples 1. Electro-chemical machining (ECM) 2. Electro-chemical Grinding (ECG) 3. Electro-chemical Honing (ECH) 4. Electro-chemical Deburring (ECD)
- 6. Processes in CM Cleaning Drying Maskant coating Dipping in chemical solution Stirring & Heating – For Uniform Depth washing
- 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
- 8. Drying After cleaning the work piece is dried in air
- 9. Maskant Coating Selective Machining The selective portions (un-machining areas) covered by resistant material, called maskants
- 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
- 14. MASKANTS
- 15. • Scribed and Peeled Maskants • Photo resists Maskants METHODS OF MASKANTS
- 16. Scribed and Peeled Maskants For ordinary work piece a paint like material sprayed or dipped or brushed over the metal
- 17. Maskant .
- 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
- 20. . .
- 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
- 31. Analysis of Metal Removal • Electrolysis Process
- 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.
- 37. ECM tool material properties
- 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.
- 39. ELECTROLYTE USED
- 40. ADVANTAGES OF ECM PROCESSES
- 41. ADVANTAGES OF ECM PROCESSES
- 42. DISADVANTAGES OF ECM PROCESSES
- 44. DEFFERENCE BETWEEN EDM AND ECM
- 45. ELECTRO-CHEMICAL GRINDING (ECG) OR ELECTROLYTIC GRINDING .
- 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
- 47. Electro-chemical Grinding Work Piece +Ve Terminal Grinding Wheel - Ve Terminal D.C.Voltage 3 – 30 V
- 48. Gap 0.025mm ELECTROLYTE Sodium Nitrate Sodium Chloride Potassium Nitrate + Water
- 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
- 55. ELECTRO-CHEMICAL HONING for Internal grinding Combined action of electro-Chemical attack and Honing stone effect
- 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.