Transcript Document 491281

Slovak University of Technology
Faculty of Material Science and Technology in Trnava
Machine Tools And
Devices For Special
Technologies
Chemical machining
Chemical machining
Local melting of material by suitable diluent.
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Machining of metal materials,
Removing speed of material independence on
hardness and on toughness,
Surfaces with complicated shape with high
accuracy and quality,
Here is no originated heat and mechanical
influence area,
Large areas – more economical than milling
Chemical machining
1 – base material,
2 – mask,
3 – holes carved out of
mask,
In the place of holes the
material is melted by
influence of diluents.
Material machinability
Four groups of materials by chemical machinability:
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Copper, bronze – easy they are melted, good
machinability by chemical machining,
nickel, zinc, aluminium
manganese, molybdenum,
chrome, gold, wolfram – they are hard melted,
bad machinability by chemical machining
Diluents for chemical machining
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Ferrous metals – different acids,
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copper, alloys of copper, heavy metals –
chloride of ferrum FeCl3,
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Aluminium, alloys of aluminium, light metals –
caustic soda NaOH
Workpiece preparation for
chemical machining
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Grease removal and surface cleaning –
removing the allochemicals from surface and
oxidic coats too (Al alloys – AL2O3 coat), dipping
into 5% medium NaOH and next into 30%
medium of acid of nitride,
steeping – increasing of mask adhesion, dipping
into medium H2SO4 and next duochrom of
patassic,
masking – coating resisted on influence of
diluent (resin, enamel) thickness till 2 mm.
Workpiece preparation for
chemical machining
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Mask drying – mask coating is drying 6 till
8 hours, it can be accelerated in the furnace
(small workpieces),
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Engraving of mask – into drying mask are
created holes (hand engraving, engraving
by laser ...),
Time needed for machining
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It is independence on the size of the machined
surface,
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It is depend on depth of machining only,
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Speed of outline 0,01 till 0,5 mm/min.,
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mask resisted to outlining approximately 8 hours.
Mask undercutting
Speed of outline in homogenne material is the
same in all directions. Rate of undercutting is
approximately the same as depth of outlining.
Mask undercutting
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Is not possible to make shape rims,
In immersion into etching pool is needed to
assure that origin gas is not to mass in the place
of undercut (scaling of mask, non-constant speed
of undercutting....), side long immersion,
mixturing,
Mixturing of etching pool:
 Washing
off etching impurities,
 Asked concentration of etchant in the place of etching,
 Outflow of gas bubbles.
Spraying of etching solution
Kinds of chemical machining
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Chemical clipping,
chemical milling (deeping),
Chemical engraving
chemical sharping,
Chemical polishing,
Machining by active substance,
Photochemical machining,
termic removing of burrs.
Chemical clipping
Thin plates,
 Completely component is sinking,
 Small, shape difficult components
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Example:
 Plotters of shavers
Chemical milling
Accuracy shaping of difficult big shape surfaces.
Speed of removing is moving round 0,025 mm/min.
Originated undercutting, is necessary to speculate
with undercutting in the mask production.
Dimensions accuracy is given by thickness of
removing layer. Roughness is between Ra=0,75
to Ra=3,8.
Chemical milling
Using of chemical milling:
 aerial and cosmic industry – local releasing
of casts and forgings of light and high
strength alloys,
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Small metal components of high strength
material when is not economical to produce
dies.
Chemical engraving, grinding,
polishing
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engraving – dimension of picturing is small for
using of mechanical engraving – matrixs of post
marks,
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grinding – very accurated shapes (accuracy
under 1mm), low roughness (Ra 0,01),
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polishing – still softer than grinding, using in
small and shape difficult components that by
mechanical kind is not possible to polish.
Machining by active substance
Machining shape difficult surfaces.
Semi-solid substance of cellulose (electro gel)
impregnated by acid is attach to the workpiece
surface. In the place of contact the workpiece is
melted.
Is possible to achieve step by step removing until
depth 10 mm. Dimension accuracy is from 0,02 to
0,07 mm.
For acceleration of process is possible to connected
electric voltage until 10V.
Machining by active substance
Photochemical machining
Mask is created by photographic kind.
Using in production:
 Masks of TV set and screening,
 Code disks,
 Optical divider,
 gasket,
 Ornamental object,
 Semiconductor components.
Photochemical machining
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Patern of production – laser beam creating
the sign in the photographical film. This picture
(master) is frequently applied to photo tool.
(patern).
Preparation of surface – surface must be
cleaned, grease removing, eventually to pickle,
Coating of photoresist – it is polymer sensitive
to ultraviolet emission is necessary to dry him.
Processing of photoresist – through the
pattern is photoresist emissed by light of
suitable wave length (UV) and is created mask
(positive, negative).
Photochemical machining
Advantage of photochemical machining:
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Low costs of tools,
Low costs of modification,
Simply transmission to series production,
Properties of the base material are not damages,
No originated burrs.
Thermic removing of burrs
Burrs are removed by influence of thermic
wave (by explosion).
Thermic wave has temperature more than
3000°C and lasted particular s.
Burrs are melted or evaporated but workpiece
is not in time to absorbing a lot of heat.
Burrs are verily removed from inaccessible
places.
Thermic burrs removing