The invention relates to a selective fused deposition
modelling machine using electro chemical discharge for selective
metallic deposition of metals on a surface. The invention can
also be used for micro welding of metallic components and
selective metallic layered deposition for creating any 3-D
objects for generative manufacturing through fused deosition
modelling (FDM).
The invention can further be applied in futuristic rapid
proto typing of metallic objects like wave guides and also in
reparing damaged surface of micro metallic objects.
PRIOR ART
For a selective depositions of metal built up, the speed
of deposition is required to be enhanced without the undesirable
effects like inhomogeneous coat, tree-formation etc, for which
slow rate of deposition is practised with low current density
operations.
Many experiments have failed, but NASA has patented a
technique like High Speed Selective Jet Electrodeposition (HSSJE)
in US in 1974 (US Patent No. 3,£J.Q, 329) , Two groups, Bocking W
and Davec C J et al studied this phenomenon. In which metal
ions from the anode dissolve in the electrolyte. This grows,
at a rate proportional to the current passed. This process causes
a depletion of metal ions in the electrolyte in the vicinity
of cathode as the rate of deposition is faster than their rate
of replacement by migration due to electric field. Or in the
other words, the close proximity between anode and cathode
(work) enhances the deposition rate in contrast to plating.
No use of any electrical discharge is made and no high temperature
melting is provided in the process.
In the above mentioned patent and publications, 'Prototyping
of Printed Circuit Boards Using Selective Jet Electrode
Deposition', Mr W Bocking mentions that in his process, a free
standing, non-submerged jet of electrolyte flowing at a high
velocity impinges on to the surface. A current is passed from
an anode, which is placed upstream from the nozzle. Away from
the impingement region an extremely thin wall jet layer of
electrolyte forms. The electrical resistance of the wall jet
is high in comparison to the impingement region so no deposition
can occur there. As a result, deposition can occur mainly in
the impingement region and immediate surrounding area. By moving
the nozzle in relation to the substrate while depostion is
occurring, it is possible to selectively write tracks and
patterns at relatively faster rates without the need for masking
the substrate.
There are disadvantages associated with the present system
of deposition of metal on a substrate is that the substrate
is submerged in the electrolyte.
Another disadvantage associated with the present system
of deposition of metal on a substrate is that though the jet
is not submerged, an anode is placed separately and the bonding
strength of the deposited layer is weak for any fruitful work.
Yet another disadvantage with the present system of
deposition of metal on a substrate is that the simple metallic
depositions are" based on Faradic laws ) where the low current
density and the higher gap between the electrode and the object
restricted the rate, selective deposition without the mask is
impossible besides other disadvantages like accuracy thickness
etc.
Further disadvantages associated with the present system
of deposition of NASA's patent on achieving the selective
deposition without a mask was achieved through a jet-flow and
an electrode placed ahead of it, to allow the current flow.
Though relatively faster rate of deposition is achieved, the
bonding strength of the deposit and accuracy may not be
achievable.
SUMMARY OF THE INVENTION
Therefore the main object of the present invention of fused
deposition through electrochemical discharge is that the
electrode is placed within the jet stream and does not require
a standing electrolyte above the substrate besides the jet which
is not submerged.
Another object of the present invention is that the spark
produced within the electrolyte column along with the ion
impingement fuses the metallic deposits onto the substrate and
lay ex s improving the bonding strength of the deposits.
Yet another object of the present invention of fused
deposition through electrochemical discharges is that the
selective two directional layering is achieved through autdmatic
program motion control to the worktable.
According to the present invention there is provided a selective fused deposition
modelling machine using electro chemical discharge comprising a machine bed
with a column on which an arm is movabiy mounted to move vertically along the
column, and can be clamped at any height of the column, said arm at the other
end is provided with a nozzle in a too! head, characterized in that an electrode
wire fed from a wire spool is placed as an anode within the jet flow of said
nozzle, voltage and current setting being optimized for creating continuous
discreet sparks, a wire feeder mounted on the top of said tool head for
controlling the electrode wire feeding; and said machine bed being provided with
a KY table having deposit in the impingement region and said nozzle is
connected to a water tank and electrolyte tank, said electrolyte flow is passed
through the nozzle to maintain a wall jet.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The nature of the invention, its objective and further advantages residing in, the
same will be apparent from the following description made with reference to the
non limiting examplary embodiments of the invention represented in the
accompanying drawings:
Figure 1 shows a scheme of selective jet electrodischarge
deposition for contour layering.
Figure 2 photo showing a two directional layer deposition
of copper with FDM using electrochemical discharge in the present
invention,
Figure 3 photo shows the multiple layers of micro welded
cross-section,
Figure 4 drawing of the FDM-ECD mechanical set up,
Figure 5 photo showing the FDM-ECD system for selective
metal deposition (compressor unit is not shown).
DETAIL DESCRIPTION
Figures 1 and 4 shows the machine and its principle of
operation.
The machine comprise a machine bed (14) and a vertical column
(2) attached at one end of the base (14). The column carries
a arm (15) which can be adjusted up or down the vertical column
2 and can be clamped at any height (20).
The arm 15) carry the nozzle (5) with a tool head (3) at
the bottom. Arrangement is made in the nozzle (5) for a wire
electrode (6) which is in the form of a wire working as an anode
and is fed with an electrode wire feeder (4) for feeding the
wire from a wire spool (7) provided on the radial arm (15).
A X-Y table (1) is placed at one end of the machine bed (14)
or placement of substrate for deposit (10) of the metal at
the impingement region (11) of the tool head (3).
A water tank (8) and an electrolyte tank (9)are fitted on
the arm and is connected to the nozzle assembly. The electrolyte
flow (12) is made through the nozzle (5) and water is used to
flush the nozzle (5) when the nozzle (5) gets clogged.
The electrolyte flow (12) forms a wall jet (13) over the deposit
(10). A spark (18) is produced at the end of the wire-electrode
(6).
The operation of the machine is controlled by an interfacing'
computer (16) and is connected to a power supply (17).
The novelty in the process proposed is in the electrode
(6) itself which is placed within the jet-flow i,e. the nozzle
(5), maximum deposition rate is achievable without any
disadvantages of the previous technique, the voltage and current
setting if optimised to create continuous discrete sparks (18)
(but not arcs) would stabilise the fusion of the metals just
after it is deposited. This improves the selective deposition
rate are observed to be more than Faradic deposition (earlier
process), improves fusion of particles to improve the bonding
strength of the deposit and possible to increase speed and layer
thickness through multiple layer deposition, improving the
versatility of the process. The confirmation of the finding
is as evident from Figures 2 and 3. Figure 2 shows the
rectangular selective deposition through a number of layers
of copper deposits on a substrate (electrically conductive with
XY-motion of the worktable. Figure 3 shows the confirmative
fused deposition through layers.
The working of the system is further described in which
the system consists of Mechanical Unit, Electrolyte Flow Unit,
Electrode Feeding Unit and the Electrical Unit.
The mechanical unit consists of machine bed (14) and
column (2); work holding and traverse unit (19) and the tool-
holding unit '.(^SJ. The traverse unit table (1) in X and Y
direction is achieved through precision slides driven by micro
stepping motors with program generated in an IBM PC (16). The
tool holder (3) holds the nozzle (5) for electrolyte flow (13)
and guides the electrode (6).
The electrolyte flow unit consists of air pressurizing
unit, control valves, electrolyte tank (9), the water tank (3)
for purging facility of the nozzle (5).
The electrode feed device (4) provides electrode (6) of
thin wire feed mechanism (4) whose feed velocity can be servo
controlled. The nozzle (5) and tip of the tool head (3) is
presently manually controlled but it is to be automatically
controlled for the Z-axis in case of 3-dimentional objects.
However,multiple layers is laid at the moment without any
difficulty for creating thick deposits (10).
The electrical circuit is to supply the regulated DC voltage
and current necessary for the operation with short-circuit
protection. The nature of spark (18) is optimised to produce
a stable fusion (welding) of deposits and layers.
A view of the system is shown in Figure 5.
This machine has tremendous potentials for research and
industrial uses like:
1. Selective metallic deposition of metals on surface.
2. Micro welding of metallic components.
3. Selective metallic layered deposition for creating any
3-D objects for generative manufacturing through Fused
Deposition Modelling (FDM).
4. Futuristic Rapid Prototyping of Metallic objects like wave-
guides .
5. Repairing damaged surface of micro metallic objects.
The invention described hereinabove is in relation to
the nonlimiting embodiments as defined by the accompanying
claims.
1. A selective fused deposition modelling machine using electro chemical
discharge comprising a machine bed (14) with a column (2) on which an
arm (15) is movably mounted to move vertically along the coiumn (2)
and can be clamped at any height (20) of the column (2), said arm (15)
at the other end is provided with a nozzle (5) in a tool head (3),
characterized in that an electrode wire (6) fed from a wire spool (7) is
placed as an anode within the jet flow of said nozzle (5), voltage and
current setting being optimized for creating continuous discreet sparks
(18), a wire feeder (4) mounted on the top of said tool head (3) for
controlling the electrode wire feeding and said machine bed (14) being
provided with a XY table (1) having deposit (10) in the impingement
region (11) and said nozzle (5) is connected to a water tank (8) and
electrolyte tank (9), said electrolyte flow (12) is passed through the
nozzle (5) to maintain a wall jet (13).
2. The selective fused deposition modelling machine using electrochemical
discharge as claimed in claim 1 wherein the traverse unit comprising the
XY table (1) is provided with precision slides driven by micro-stepping
motors and is controlled by the interfacing computer (16) connected to
the machine.
3. The selective fused deposition modelling machine using electrochemical
discharge as claimed in claim 1 wherein the too! head is hollow and
accommodates trie nozzie (5) for electjoiyte flow (12) and to guide the
wire electrode (6).
4. The selective fused deposition modelling machine using
electrochemical discharge as claimed in claim 1 wherein the
electrode wire feeder (4) provides a wire-electrode (6) of thin
wire whose velocity is servo controlled by said interface
computer ("6).
5. The selective fused deposition modelling machine using
electrochemical discharge as claimed in claims * and 3 wherein
the tool head (3) distance from the impingement region (11 )
is controlled manually and also can be by the interface computer
(16) for the Z-axis in case of 3-dimensional objects.
6. A selective fused deposition modelling machine using
electrochemcial discharge as herein described and illustrated.

A selective fused deposition modelling machine using electro chemical discharge
comprises a machine bed (14) with a column (2) on which an arm (15) is
movably mounted to move vertically along the column (2) and can be clamped at
any height (20) of the column (2). The arm (5) at the other end is provided with
a nozzle (5) in a tool head (3). An electrode wire (5) fed from a wire spool (7) is
placed as an anode within the jet flow of the nozzle (5). Voltage and current
setting is optimized for creating continuous discreet sparks (18). A wire feeder
(4) mounted on the top of said tool head (3) for controlling the electrode wire
feeding and the machine bed (14) is provided with a XY table (1) having deposit
(10) in the impingement region (11). The nozzle (5) is connected to a water
tank (8) and an electrolyte tank (9). The electrolyte flow (2) is passed through
the nozzle (5) to maintain a wall jet (13).