07-01-2012, 11:28 AM
Introduction
Chemical machining
Electro chemical machining
Electrical discharge machining
Wire EDM
Laser beam machining
Electron-beam machining and plasma-arc cutting
Water-jet machining
Abrasive-jet machining
Nanofabrication
Micro machining
Economics of advanced machining process
Situations where processes are not satisfactory, economical or even possible
High hardness and the strength of the material
Work-piece too flexible
Complex shape
Surface finish and dimensional tolerances
Undesirable Temperature rise and dimensional tolerances
Examples of parts made by advanced Machining Processes
Fig : Examples of parts made by advanced machining processes. These parts are made by advanced machining processes and would be difficult or uneconomical to manufacture by conventional processes. (a) Cutting sheet metal with a laser beam.(b) Microscopic gear with a diameter on the order of 100µm, made by a special etching process.
Chemical machining
Chemical attacks metals and etch them by removing small amounts of material from the surface using reagents or etchants
Chemical milling:
Shallow cavities produced on plates, sheets, forgings, and extrusions
Procedure for chemical milling Steps :
1 – Residual stresses should relieved in order to prevent warping
2 – Surfaces to be thoroughly degreased and cleaned
3 - Masking material(tapes,paints,elastomers & plastics ) is applied
4 – masking is peeled off by scribe and peel technique
5 – The exposed surfaces are etched with etchants
6 – After machining the parts to be thoroughly washed to prevent further reactions with residue etchant
7 – rest of the masking material is removed and the part is cleaned and inspected
8 – additional finishing operations are performed on chemically milled parts
9 – this sequence is repeated to produce stepped cavities and various contours
Process capabilities:
Chemical milling used in the aerospace industry
Tank capacities for reagents are as large as 3.7m x15m
Process also used for micro electronic devices
Surface damage may result due to preferential etching and intergranular attack
Chemical blanking:
Chemical blanking is similar to chemical milling
Material is removed by chemical dissolution rather than by shearing
Burr free etching of printed-circuit boards, decorative panels, thin sheet metal stampings as well as production of small and complex shapes
Chemical Machining
Fig : (a) Schematic illustration of the chemical machining process. Note that no forces or machine tools are involved in this process. (b) Stages in producing a profiled cavity by machining; not the undercut.
Photochemical blanking :
Modification of chemical milling
Material removed from flat thin sheet by photographic techniques
Steps for photochemical blanking
Design is prepared at a magnification of 100x
Photographic negative is reduced to the size of finished part
Sheet blank is coated with photosensitive material (Emulsion)
Negative placed over coated blank and exposed to ultra violet light which hardens the exposed area
Blank is developed which dissolves the exposed areas
Blank is then immersed into a bath of reagent or sprayed with the reagent which etches away the exposed areas
The masking material is removed and the part is washed thoroughly to remove all chemical residues
Design considerations
Designs involving sharp corners,deep & narrow cavities, severe tapers or porous work piece should be avoided
Undercuts may be developed because etchant attacks both in horizontal and vertical direction
To improve production rate the bulk of the work piece should be shaped by other machining process priorly
Dimensional variations can occur ,this can be minimized by proper selection of artwork media by controlling the environment
Many product designs are now made with computer aided design
Chemical machining
Electro chemical machining
Electrical discharge machining
Wire EDM
Laser beam machining
Electron-beam machining and plasma-arc cutting
Water-jet machining
Abrasive-jet machining
Nanofabrication
Micro machining
Economics of advanced machining process
Situations where processes are not satisfactory, economical or even possible
High hardness and the strength of the material
Work-piece too flexible
Complex shape
Surface finish and dimensional tolerances
Undesirable Temperature rise and dimensional tolerances
Examples of parts made by advanced Machining Processes
Fig : Examples of parts made by advanced machining processes. These parts are made by advanced machining processes and would be difficult or uneconomical to manufacture by conventional processes. (a) Cutting sheet metal with a laser beam.(b) Microscopic gear with a diameter on the order of 100µm, made by a special etching process.
Chemical machining
Chemical attacks metals and etch them by removing small amounts of material from the surface using reagents or etchants
Chemical milling:
Shallow cavities produced on plates, sheets, forgings, and extrusions
Procedure for chemical milling Steps :
1 – Residual stresses should relieved in order to prevent warping
2 – Surfaces to be thoroughly degreased and cleaned
3 - Masking material(tapes,paints,elastomers & plastics ) is applied
4 – masking is peeled off by scribe and peel technique
5 – The exposed surfaces are etched with etchants
6 – After machining the parts to be thoroughly washed to prevent further reactions with residue etchant
7 – rest of the masking material is removed and the part is cleaned and inspected
8 – additional finishing operations are performed on chemically milled parts
9 – this sequence is repeated to produce stepped cavities and various contours
Process capabilities:
Chemical milling used in the aerospace industry
Tank capacities for reagents are as large as 3.7m x15m
Process also used for micro electronic devices
Surface damage may result due to preferential etching and intergranular attack
Chemical blanking:
Chemical blanking is similar to chemical milling
Material is removed by chemical dissolution rather than by shearing
Burr free etching of printed-circuit boards, decorative panels, thin sheet metal stampings as well as production of small and complex shapes
Chemical Machining
Fig : (a) Schematic illustration of the chemical machining process. Note that no forces or machine tools are involved in this process. (b) Stages in producing a profiled cavity by machining; not the undercut.
Photochemical blanking :
Modification of chemical milling
Material removed from flat thin sheet by photographic techniques
Steps for photochemical blanking
Design is prepared at a magnification of 100x
Photographic negative is reduced to the size of finished part
Sheet blank is coated with photosensitive material (Emulsion)
Negative placed over coated blank and exposed to ultra violet light which hardens the exposed area
Blank is developed which dissolves the exposed areas
Blank is then immersed into a bath of reagent or sprayed with the reagent which etches away the exposed areas
The masking material is removed and the part is washed thoroughly to remove all chemical residues
Design considerations
Designs involving sharp corners,deep & narrow cavities, severe tapers or porous work piece should be avoided
Undercuts may be developed because etchant attacks both in horizontal and vertical direction
To improve production rate the bulk of the work piece should be shaped by other machining process priorly
Dimensional variations can occur ,this can be minimized by proper selection of artwork media by controlling the environment
Many product designs are now made with computer aided design
