U.S. patent application number 10/978124 was filed with the patent office on 2006-05-04 for method and apparatus for plating extrusion dies.
Invention is credited to James F. Avery, James J. Bernas, Mark L. Humphrey.
Application Number | 20060091016 10/978124 |
Document ID | / |
Family ID | 36260548 |
Filed Date | 2006-05-04 |
United States Patent
Application |
20060091016 |
Kind Code |
A1 |
Avery; James F. ; et
al. |
May 4, 2006 |
Method and apparatus for plating extrusion dies
Abstract
Method and apparatus are set forth for providing a substantially
uniform coating on inner wall portions of a die having slots or
openings formed in the face of the die. The die is supported by a
fixture for up and down movement while it is immersed in a bath of
a desired plating solution. A tube or cylinder positioned on an
upper surface portion of the die repeatedly collects a column of
plating material in a cylinder from the bath on downward movements
of the die, so as to provide fresh or replenishment plating
solution to the die. The column of plating solution in the cylinder
functions as a hydrostatic head and forces the confined solution
into the interior of the die on upward movements, thus promoting
coating uniformity along inner walls of the die. The die may be
rotated 180 degrees so that each face of the die may be subjected
to the hydrostatic force flow of the plating solution, also
resulting in a more uniform coating.
Inventors: |
Avery; James F.;
(Horseheads, NY) ; Bernas; James J.; (Horseheads,
NY) ; Humphrey; Mark L.; (Corning, NY) |
Correspondence
Address: |
CORNING INCORPORATED
SP-TI-3-1
CORNING
NY
14831
US
|
Family ID: |
36260548 |
Appl. No.: |
10/978124 |
Filed: |
October 29, 2004 |
Current U.S.
Class: |
205/101 ;
204/237 |
Current CPC
Class: |
C23C 18/1617 20130101;
C23C 18/1616 20130101; C23C 18/1669 20130101; C23C 18/163
20130101 |
Class at
Publication: |
205/101 ;
204/237 |
International
Class: |
C25D 21/18 20060101
C25D021/18; C25B 15/00 20060101 C25B015/00 |
Claims
1. A method of plating interior wall portions of a die which
comprises, immersing a die within a bath of plating solution,
moving said die upwardly and downwardly within said bath,
repeatedly confining a replenished supply of said plating solution
above said die during downward movement of said die within said
bath, and flowing said confined supply of replenished plating
solution solely into interior portions of said die during upward
movement of the die to produce a substantially uniform plating
coating on the interior wall portions of said die.
2. A method as defined in claim 1 including the step confining a
column of the replenished plating solution above the die and within
the confines of peripheral portions of the die.
3. A method as defined in claim 1 including the step of creating a
hydrostatic head of said plating solution within the confined
supply of plating solution and forcing said solution into interior
portions of the die.
4. A method as defined in claim 1 including the step of
periodically rotating the die 180 degrees while still being
retained within the bath.
5. A method as defined in claim 1 including the step of
periodically flowing the confined supply of replenished plating
solution into interior portions of the die from opposite faces of
the die.
6. A method of nickel plating interior wall portions of a die
having slots for extruding ceramic honeycomb structures which
comprises, immersing an extrusion die to be coated in a bath of
electroless nickel plating solution, moving said die upwardly and
downwardly within the bath solution, forming a separate confined
column of plating solution above the die from the bath, and
creating a hydrostatic head within said separate confined column of
plating solution; whereby the hydrostatic head forces the confined
column of plating solution into the slots of said die to provide a
substantially uniform nickel coating on the interior wall portions
of said slots.
7. A method as defined in claim 6 including the step rotating the
die 180 degrees while retaining the die within the plating
solution.
8. A method as defined in claim 7 including the step of flowing the
confined supply of plating solution under hydrostatic pressure into
the die from opposite faces of the die to provide more uniform
coating thickness along the slot length.
9. A fixture for plating interior wall portions of a die member
which comprises, means for supporting said die member in a plating
bath solution, means for moving said die member upwardly and
downwardly within said plating bath and, means for confining a
column of said plating solution above said die and for directing
the flow of said confined solution solely into interior portions of
said die member to provide a substantially uniform coating of
plating material along said interior wall portions.
10. A fixture for plating interior wall portions of a die member as
defined in claim 9, wherein said confining means includes means for
replenishing plating solution to an upper surface of said die
member.
11. A fixture for plating interior wall portions of a die member as
defined in claim 9, including pivotal means for rotating said die
member from one fixed position to another fixed position while said
die is in said plating bath.
12. A fixture for plating interior wall portions of a die member as
defined in claim 9, wherein said means for supporting said die
includes a pair of clamping rings which encircle a peripheral
portion of said die member.
13. A fixture for plating interior wall portions of a die member as
defined in claim 12, wherein said confining means includes a
tubular member removably secured to said support means.
14. A fixture for plating interior wall portions of a die member as
defined in claim 9 wherein said confining means includes a
cylindrical member removably secured to at least one of said
clamping rings.
15. A fixture for plating interior wall portions of a die member as
defined in claim 9 including trunnion means pivotally mounting said
die support means and wherein said pivotal means includes a lever
secured to said die supporting means for rotating said support
means and said die about said trunnion means.
16. A fixture for plating interior wall portions of a die member as
defined in claim 9 including locking pin means for locking said die
in a desired rotated position.
17. A fixture for plating interior wall portions of a die member as
defined in claim 13 wherein said clamping rings have recessed
t-slots and said cylindrical member has a pair of pins for
engagement with said slots for securing said cylindrical member on
said clamping ring.
Description
BACKGROUND OF THE INVENTION
[0001] Extrusion dies have been found to be useful in forming
cellular or honeycomb ceramic substrates for use in catalytic
converters utilized in the exhaust system of internal combustion
engines. In order for such converters to function efficiently, it
is necessary that the cells provide a substantially large surface
area for catalytic material to react with the exhaust gases, and
that the cell walls have a substantially thin cross-section
dimension so as to provide a substantially large open frontal area
and thereby reduce back pressure within the exhaust system.
[0002] In order to provide increased surface area within the
honeycomb structure so as to enhance catalytic activity, the number
of cells has been increased and the wall thickness between the
cells has been reduced from about 8 mils to 4 mils or less.
Accordingly it became necessary to reduce the slot size of the
extrusion die from about 0.008'' to 0.0035'' to form such thin
walled cellular structures. To protect the extrusion die from the
abrasiveness of the extruding ceramic material, it is necessary to
provide a hard protective coating on the walls of the die. The
coating must be as uniform as possible for the die to function
correctly. The reduced slot size of the dies for thin walled
structures, made it difficult to provide a uniform coating on the
die walls using the known electroless nickel plating process
techniques.
[0003] In order for the electroless nickel plating process to
produce a uniform coating throughout a die, it is necessary that
all surfaces of the die receive a constant replenishment of the
plating solution with adequate concentration of the solution
constituents. As the plating deposit builds up on the die walls,
some of the constituents are consumed and therefore the constant
replenishment of the solution to all surfaces of the die is needed
to ensure that a uniform deposit thickness is obtained. However,
with reduced slot sizes the restrictive nature of the small slots
in the dies prevented adequate replenishment of plating solution
with known devices, resulting in significant non-uniformity of the
coating.
[0004] Others have experienced non-uniform plating problems, but
for different reasons. In U.S. Pat. No. 4,938,840, coating
variations were a problem due to variations in accessibility of the
plating solution, whereas in U.S. Pat. No. 6,291,025, the problems
in plating thickness were due to the interactions of the plating
solution components. U.S. Pat. No. 4,842,886 has a problem with
controlling the thickness of the plated layer due to unpredictable
surface characteristics, and U.S. Pat. No. 4,406,250 is concerned
with the deposition rate variation due to the reaction by-products
formed in the plating solution.
[0005] The present invention has overcome the problem of plating
the walls of extrusion dies for forming thin-walled honeycomb
structures with a substantially uniform coating, particularly where
the slot size may have a width of less than 8 mils, by implementing
an improved fixture and plating solution flow techniques.
SUMMARY OF THE INVENTION
[0006] In its simplest form, the present invention is directed to
an improved fixture for supporting a die to be plated in a plating
solution, and a novel procedure for enhancing the flow of the
plating solution through the die to provide a substantially uniform
coating on the walls of the die. The fixture is designed for
vertical movement within a plating bath and includes a tube or
cylinder above the die for replenishing plating solution and for
maintaining a column of such plating solution over the die during
the plating process, so as to produce uniform deposit thickness,
such as from an electroless nickel plating solution. The cylinder
complements a peripheral portion of the die and thus the solution
within the cylinder, when under a hydrostatic head, is directed
solely downwardly through the die and not permitted to flow
outwardly around the die. A further feature of the fixture is that
the tube may be removed and the die flipped or rotated 180 degrees
while within the bath, so that either the pin side or the feed hole
side of the die may be facing upward, again to provide better
uniformity of the deposited coating.
[0007] It thus has been an object of the present invention to
provide an improved fixture for facilitating the production of a
uniform coating on wall portions of the passageways in dies for
forming thin walled honeycomb structures.
[0008] A further object of the invention had been to provide an
improved method for flowing plating solutions through a die so as
to facilitate a uniform coating of the plating material on inner
wall portions of the die.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a fixture for holding a die as used in the prior
art.
[0010] FIG. 2 is a schematic view showing the operation of the
prior art fixture of FIG. 1.
[0011] FIG. 3 is a micrograph of the coating on a die obtained by
utilizing the fixture of FIG. 1, and the operation of FIG. 2.
[0012] FIG. 4 is a perspective view of the improved fixture of the
present invention.
[0013] FIG. 5 is a schematic view of the fixture of FIG. 4 moving
downward in a bath of plating solution.
[0014] FIG. 6 is a schematic view of the fixture of FIG. 4 moving
upwardly in a bath of plating solution.
[0015] FIG. 7 is a perspective view of fixture of the present
invention, showing the removability of the cylinder portion.
[0016] FIG. 8 is a micrograph of the coating on a die produced by
utilizing the improved fixture of FIG. 4 and the procedures shown
in FIGS. 5 and 6.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0017] To better appreciate the present invention it is helpful to
look at what preceded it. Referring now to FIGS. 1 and 2, a prior
art fixture 10 is shown having a lower ring portion 12 for holding
a die 14. A pair of side braces or support members 16 are attached
at their lower ends to the ring 12, and at their upper ends to a
cross bar 18. The cross bar is connected to suitable means (not
shown) for moving the fixture 10 and die 14 up and down in a
plating bath 20, as shown by arrows a and b. The bath 20 is
preferably an electroless nickel plating solution. As the die 14,
which is secured in one position by the fixture 10, is moved
upwardly and downwardly by the fixture in the bath, a portion of
the plating solution 20 flows through the die as shown by arrows c
and d, but due to the resistance of the small slot openings in the
die, a substantial amount of the flow is over the surface of the
die 14 as shown of arrows e and f, rather than through the die as
desired. On the up stroke a, flow through the die 14 is shown by
arrows c, whereas flow across the die is shown by arrows e, and on
the down stroke b, flow through the die is shown by arrows d,
whereas flow across the die is shown by arrows f.
[0018] FIG. 3 is a micrograph of a section of die 14 showing one
side 22 of an extrusion slot after being coated with an electroless
nickel plating layer 23 using the prior art method and apparatus
shown in FIG. 2. The exit end 24 of the extrusion slot 22 is formed
by pin 26 and is shown at the top of the figure, and entrance end
28 of the slot is at the bottom of the figure. The surface of slot
22 may be provided with a recess 29 to enhance flow of the
extrusion material through the die 14. As a result of the impedance
to flow created by the small openings in the die 14, very little
plating occurred on the surface adjacent the bottom portion or
entrance end 28 of slot surface 22, whereas a substantial amount is
deposited on the surface near the top or exit opening 24 of the
slots. Disregarding the recess 29, FIG. 3 shows a coating thickness
variation of 51 microns along the extent of die slot 22 between the
slot entrance 28 and the exit end 24.
[0019] Referring now to FIG. 4, an improved fixture 30 of the
present invention is shown including a yoke 32 having trunnions 33
for pivotally mounting a die clamping mechanism 34. The clamping
mechanism includes a pair of clamping rings 36 and 38 which
encircle a peripheral portion of the die 40 for securing the die
therebetween, such as with nuts and bolts 42. Means including yoke
32 and connecting ring 31 move the fixture 30, and accordingly die
40 upwardly and downwardly within a plating bath 56. A lever 44 is
secured to the die clamping mechanism 34 and pivotally mounted on
the yoke 32 for pivoting or rotating the die 40 180 degrees about
trunnions 33, while the die is held by the clamping mechanism 34.
The lever 44 has a pair of openings 46 equally spaced from
trunnions 33 to receive a locking pin 48 mounted on yoke 32, so as
to lock the clamping mechanism 34 in either of the desired 180
degree positions.
[0020] A confinement tube or cylinder 50 is removably mounted on
the clamping rings 36, 38 by means of pins 52 on the tube 50 which
engage t-slots 54 formed in an inner surface of the rings 36 and
38, as shown in FIG. 7. The tube 50 is preferably made of a polymer
material, such as cpvc, so as to resist being plated by a plating
solution. The tube 50 functions to maintain a confined column of
plating solution over the die during the plating process. During
the up and down movement of the of the die within the plating
solution, the tube fills with fresh plating solution, thus enabling
an adequate replenishment of the plating solution in the die so as
to produce a uniform thickness deposit on the walls of die
slots.
[0021] As shown in FIG. 5, when the yoke 32 moves the fixture 30
downwardly within a bath 56 of an electroless nickel plating
solution, as shown by arrows v, two things happen, fresh plating
solution 56 flows into the tube 50 as shown by arrows w, and
plating solution is forced upwardly into the bottom of the die 40
as shown by arrows x. On the upward stroke of the fixture as shown
by arrows y, in FIG. 6, all of the plating solution within the tube
50 flows downwardly through the die 40 as shown by arrows z, with
none flowing around the die as happened with the prior art fixture.
The solution confinement tube 50 produces a column of plating
solution with a gravitational weight creating a hydrostatic head of
refreshed plating solution over the die 40, which forces a flow of
plating solution through the die, while the die remains within the
plating bath 56.
[0022] By thus enabling adequate solution replenishment throughout
the plating process, the uniformity of thickness of the deposit of
plating solution along internal passageways of the die between the
slot entrance and the exit end of the slots is greatly improved
over that obtained with the prior art fixture as shown by die 14 in
FIG. 3. FIG. 8 is a micrograph of a portion of a die 40 plated with
an electroless nickel plating solution utilizing the improved
fixture 30 of the present invention, showing a difference of only 4
microns between the thinnest and thickest portions of coating 23
along the extent of the extrusion slot 58. When compared with the
difference in coating thickness of 51 microns obtained on die 14
using the prior art fixture, the improved uniformity of only 4
microns obtained on die 40 with the present invention, represents
an improvement over the prior art of 92%.
[0023] The confinement tube 50 is removable from the die clamping
mechanism 34 by means of the pins 52 on the tube which engage
t-shaped slots 54 formed in clamping rings 36, 38, as can be seen
in FIG. 7. The tube is removed from the clamping mechanism by
simply rotating it so that the two opposing pins 52 on the tube
clear the t-slots 54 formed in the clamping rings 36, 38. The
ability to remove the tube 50, while the keeping the die 40
submerged in the plating bath 56 is important to the invention,
since it provides access to the die 40 for inspection during the
plating process, and also enables the die 40 to be flipped over or
rotated 180 degrees periodically during the plating process, such
that the either the pin side 60 or the feed hole side 62 of the die
40 may be facing upward.
[0024] When it is desired to rotate the die 40 from one fixed
position to another, the confinement tube 50 is removed from the
clamping mechanism 34 by rotating the tube pins 52 to clear the
slots 54 in clamping rings 36,38, and the tube is lifted out of the
fixture 32. The locking pin 48 is then removed from an opening 46
in pivoting lever 44, and the die held by clamping mechanism 34 is
rotated 180 degrees, while the die remains in the plating bath 56,
by means of lever 44. The locking pin 48 is then reinserted in an
opposite opening 46 in pivot lever 44. The solution confinement
tube 50 is then reinstalled on the fixture 30 by positioning the
tube pins 52 into their respective t-slots 54 and rotating the tube
to lock it within the slots.
[0025] Periodically rotating the die 40 in the manner described,
further improves the plating thickness uniformity since the
direction of flow of the plating solution through the die is
alternated. Further, by rotating the die, provides an opportunity
for any trapped gas that has built up from the plating process to
escape from underneath the die, which aids in solution
replenishment throughout the die's internal passageways.
[0026] From the foregoing, it can be seen that the improved fixture
of the present invention and the procedure for operating the
fixture provides for improved uniformity of plating thickness, by
not only continually replenishing plating solution to the die, but
also by directing and forcing the solution through the die and
periodically rotating the die to present an opposite surface of the
die to the plating solution.
[0027] Although the now preferred embodiments of our invention have
been disclosed, it will be apparent to those skilled in the art
that various changes and modifications may be made thereto without
departing from the spirit and scope thereof as defined in the
appended claims.
* * * * *