U.S. patent application number 14/903928 was filed with the patent office on 2016-05-26 for brush plating repair method for plated polymers.
This patent application is currently assigned to United Technologies Corporation. The applicant listed for this patent is UNITED TECHNOLOGIES CORPORATION. Invention is credited to Gary M. Lomasney, Joseh Parkos, Wendell V. Twelves, Charles R. Watson.
Application Number | 20160145747 14/903928 |
Document ID | / |
Family ID | 52280554 |
Filed Date | 2016-05-26 |
United States Patent
Application |
20160145747 |
Kind Code |
A1 |
Watson; Charles R. ; et
al. |
May 26, 2016 |
BRUSH PLATING REPAIR METHOD FOR PLATED POLYMERS
Abstract
Methods for repairing plated metallic layers on plated polymeric
parts are disclosed. First, a polymer is formed into an article of
a desired shape or geometry. The outer surface of the article is
prepared to receive a catalyst and then the outer surface is
activated with the catalyst. A first metallic layer is then plated
onto the outer surface to form a structure. Optional additional
metallic layers may be applied. Then, a defect in a damaged metal
layer is repaired by brush plating or brush electroplating.
Inventors: |
Watson; Charles R.;
(Windsor, CT) ; Twelves; Wendell V.; (Glastonbury,
CT) ; Lomasney; Gary M.; (Glastonbury, CT) ;
Parkos; Joseh; (East Haddam, CT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
UNITED TECHNOLOGIES CORPORATION |
Farmington |
CT |
US |
|
|
Assignee: |
United Technologies
Corporation
Hartford
CT
|
Family ID: |
52280554 |
Appl. No.: |
14/903928 |
Filed: |
July 9, 2014 |
PCT Filed: |
July 9, 2014 |
PCT NO: |
PCT/US2014/045972 |
371 Date: |
January 8, 2016 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
61844030 |
Jul 9, 2013 |
|
|
|
Current U.S.
Class: |
205/93 |
Current CPC
Class: |
B32B 2262/101 20130101;
C25D 1/003 20130101; G06K 19/07749 20130101; B29K 2079/08 20130101;
C25D 9/02 20130101; C23C 18/166 20130101; C25D 3/02 20130101; C23C
18/30 20130101; B29L 2031/082 20130101; C23C 18/32 20130101; B32B
27/281 20130101; C23C 18/1641 20130101; C23C 18/1653 20130101; B29C
64/106 20170801; B32B 2255/10 20130101; C25D 5/56 20130101; C23C
28/021 20130101; G01D 5/12 20130101; G01N 3/08 20130101; B32B
2262/106 20130101; B32B 2603/00 20130101; B32B 2250/02 20130101;
B33Y 80/00 20141201; G01N 2203/0298 20130101; B33Y 10/00 20141201;
G01N 2203/026 20130101; B29C 64/153 20170801; B32B 2255/205
20130101; G01N 2203/0268 20130101; B29C 37/0025 20130101; C25D 1/02
20130101; B29K 2105/251 20130101; B29C 70/54 20130101; C25D 17/12
20130101; B29K 2105/0058 20130101; C25D 1/20 20130101; B29L
2009/008 20130101; C23C 18/1657 20130101; G01B 7/16 20130101; C23C
28/023 20130101; C25D 5/06 20130101; B32B 27/08 20130101; B29K
2307/04 20130101; B29K 2105/12 20130101; C25D 7/00 20130101; B29K
2309/08 20130101; B29C 70/42 20130101; B33Y 70/00 20141201; B29K
2105/253 20130101; C25D 7/04 20130101; B29C 64/124 20170801; C23C
18/22 20130101; C25D 5/54 20130101 |
International
Class: |
C23C 28/02 20060101
C23C028/02; C23C 18/16 20060101 C23C018/16; C25D 5/06 20060101
C25D005/06 |
Claims
1. A method for repairing a plated polymer part having a damaged
metal layer, the method comprising: plating a damaged metal layer
until a new metal layer of desired thickness has been deposited
onto the damaged metal layer.
2. The method of claim 1 wherein the plating is selected from the
group consisting of brush plating and brush electroplating.
3. A method for repairing a metal part having a damaged metal
layer, the method comprising: forming a polymer into a desired
shape having an outer surface; preparing the outer surface to
receive a catalyst; activating the outer surface with the catalyst;
plating a first metal layer onto the outer surface and the catalyst
to form a first metal layer to form a structure; plating a second
metal layer onto the structure; and repairing a defect in a metal
layer until a new metal layer of desired thickness has been
deposited onto the damaged metal layer.
4. The method of claim 3 wherein the repairing a defect is selected
from the group consisting of brush plating and brush
electroplating.
5. The method of claim 3 further including depositing a third metal
onto the structure.
6. The method of claim 3 further including alloying the first and
second layers.
7. The method of claim 5 further including alloying the first,
second and third layers.
8. The method of claim 6 wherein the alloying is a process selected
from the group consisting of transient liquid phase (TLP) bonding,
brazing, diffusion bonding, heat treating, and combinations
thereof.
9. The method of claim 7 wherein the alloying is a process selected
from the group consisting of transient liquid phase (TLP) bonding,
brazing, diffusion bonding, heat treating, and combinations
thereof.
10. The method of claim 3 wherein the preparing of the outer
surface to receive the catalyst includes a process selected from
the group consisting of etching, abrading, reactive ion etching,
ionic activation, and deposition of a conductive material.
11. The method of claim 3 wherein the catalyst is selected from the
group consisting of palladium, platinum, gold, and combinations
thereof.
12. The method of claim 3 wherein the first metal is selected from
the group consisting of nickel, copper, gold, silver, graphite and
combinations thereof.
13. The method of claim 3 wherein the second metal is selected from
the group consisting of nickel, copper, gold, silver, graphite and
combinations thereof.
14. The method of claim 3 wherein the forming of the polymer into
the desired shape is performed with a process selected from the
group consisting of additive manufacturing (AM), injection molding,
compression molding, blow molding, extrusion molding,
thermoforming, transfer molding, reaction injection molding, and
combinations thereof.
15. A method for repairing a hollow metal part having a damaged
metal layer, the method comprising: forming a polymer into a
desired shape having an outer surface; preparing the outer surface
to receive an atomic layer of palladium; activating the outer
surface with an atomic layer of palladium; electroless plating
nickel onto the outer surface and the palladium to form a first
metal layer having a thickness ranging from about 0.1 to about 10
microns to form a structure; electrolytically plating copper onto
the structure; plating a third metal onto the structure; removing
the polymeric material; and repairing a defect in a metal layer
until a new metal layer of desired thickness has been deposited
onto the damaged metal layer.
16. The method of claim 15 wherein the repairing a defect is
selected from the group consisting of brush plating and brush
electroplating.
17. The method of claim 15 further including alloying the
structure.
18. The method of claim 15 wherein the polymer is removed by a
process selected from the group consisting of melting, etching,
application of a strong base, application of a stripping agent and
combinations thereof.
19. The method of claim 15 wherein the preparing of the outer
surface to receive the palladium includes a process selected from
the group consisting of etching, abrading, ionic activation,
deposition of a conductive material and combinations thereof.
20. The method of claim 15 further including applying a fourth
metal layer onto the third metal layer using a process selected
from the group consisting of electrolytic plating, electroless
plating, electroforming, thermal spray coating, plasma vapor
deposition, chemical vapor deposition, cold spraying, and
combinations thereof.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority under 35 U.S.C.
.sctn.119(e) to U.S. Provisional Patent Application Ser. No.
61/844,030 filed on Jul. 9, 2013.
FIELD OF THE DISCLOSURE
[0002] This disclosure relates to methods for repairing plated
metallic layers on plated polymeric articles. More specifically,
this disclosure relates to methods which include fabricating a
plastic article having a desired geometry, then plating the outer
surface of the plastic article with one or more metallic layers
using electroless plating, electrolytic plating, or electroforming
methods, and then repairing any defects in a damaged metal layer by
brush plating or brush electroplating.
BACKGROUND
[0003] Metallic parts tend to be heavy due to the high densities of
most metals. Typically, there are areas of a metallic part that are
lightly loaded or not loaded (little or no stress) as well as
highly loaded (or stressed) areas. An ideal metallic part would
contain a sufficient amount of metal in high-stress areas to
transmit the necessary loads and perform the function of the part.
Such an ideal part would also contain less or no metal in areas
with little or no stress, thereby reducing the weight of the
metallic part to an idealized minimum. In some cases, removing
metal from a metallic part can lead to weight savings. However,
removing metal from a metallic part by conventional means, such as
machining, laser drilling, etc., can be both difficult and costly.
Further, removing material from a metallic part can lead to reduced
material properties of the part, which may be unacceptable for its
intended application. Therefore, there is a need for improved
and/or lower-cost methods of producing metal parts that are
lightweight but strong enough in high-stress areas to perform the
function(s) of the part.
[0004] There is an ongoing effort to replace metal components in a
gas turbine engine with lighter components made from alternative
materials, even if the components experience significant loads or
are subjected to environmental concerns (e.g., high or low
temperatures, erosion, foreign-object damage) during use. For
example, in the aerospace industry, manufacturers of gas turbine
engines are considering the use of alternative materials for fan
blades, compressor blades, and possibly turbine blades. Suitable
non-metal alternative materials include, but are not limited to,
reinforced polymers, polymer matrix composites, ceramics, and
ceramic matrix composites.
[0005] Blow molding processes begin with melting the molding
material and forming it into a parison or preform. The parison is a
tube-like piece of plastic with a hole in one end through which
compressed air can pass through. The parison is clamped into a mold
and air is pumped into the parison. The air pressure pushes the
molding material outwards to match the interior surface of the
mold. Once the molding material has cooled and hardened, the mold
opens and the part is ejected. In contrast, injection molding
includes injecting molding material for the part into a heated
barrel, mixing and forcing the molding material into a mold cavity
where the molding material cools and hardens to the configuration
of the cavity. Compression molding is a method of molding in which
the preheated molding material is placed in an open-mold cavity.
The mold is closed and pressure is applied to force the material
into contact with all mold areas while heat and pressure are
maintained until the molding material has cured.
[0006] For many molding processes, hard tooling is used to form the
mold or die. While hard tooling can provide high dimensional
repeatability, hard tooling is very heavy and cumbersome and can
present a safety hazard when moved or handled. Further, fabricating
hard tooling is time consuming and costly. As a result, hard
tooling is normally too expensive and time consuming for short
production runs and/or for the fabrication of test parts. Thus, the
ability to quickly fabricate tooling to support short production
runs and/or test runs of composite materials is desired.
[0007] Blow molding and injection molding cannot be used if the
plastic to be molded is in the form of a composite with a plurality
of layers or plies, i.e., a composite layup structure. Composites
are materials made from two or more constituent materials with
different physical or chemical properties that, when combined,
produce a material with characteristics different from the
individual components. The individual components remain separate
and distinct within the finished structure. Typically, composite
layup structures can be molded or shaped using compression molding,
resin transfer molding (RTM), or vacuum assisted resin transfer
molding (VARTM), all of which utilize hard tooling that typically
include details machined into one or more blocks of metal that form
the mold.
[0008] Composites can also include reinforcing fibers or matrices.
The fibers or matrices may be formed from ceramics, metals,
polymers, concrete, and various other inorganic and organic
materials. Organic matrix composites (OMCs) may include polyimides
and/or bismaleimides (BMIs) because they can be used at higher
temperatures than other commonly used organic reinforcing
materials, such as epoxies. Such high-temperature OMCs may be
processed by autoclave molding, compression molding, or
resin-transfer molding. These processes all require lengthy cure
and post-cure cycles as well as hard tooling that is difficult and
costly to make. Thus, improved methods for molding OMCs are also
desired.
[0009] Electrolytic and electroless plating are inexpensive methods
of forming a metallic layer on a surface of a molded plastic
article. To ensure adhesion of the plated layer to the molded
plastic article, the surface of the plastic article may need to be
prepared by etching, abrading, or ionic activation. The most common
types of metals used for plating molded plastic include copper,
silver, and nickel, although other metals may be used.
[0010] Electrolytic plating is the deposition of a metal on a
conductive material using an electric current. A molded plastic
article must first be made conductive to be electrolytically
plated. This can be done through a multi-step process that
typically involves the application of a catalyst, electroless
plating of Ni, and electrolytic plating of Cu. The article to be
electrolytically plated is then immersed in a solution of metal
salts connected to a cathodic current source, and an anodic
conductor is immersed in the bath to complete the electrical
circuit. Electric current flows from the cathode to the anode, and
the electron flow reduces the dissolved metal ions to pure metal on
the cathodic surface. Soluble anodes are made from the metal that
is being plated and dissolve during the electroplating process,
thereby replenishing the bath.
[0011] A closely related process is brush electroplating, in which
localized areas or entire items are plated using a brush saturated
with plating solution. The brush may be a stainless steel body
wrapped with a cloth material that both holds the plating solution
and prevents direct contact with the item being plated. The brush
may be connected to the positive side of a low-voltage
direct-current power source, and the item to be plated connected to
the negative side. The operator dips the brush in plating solution
then applies it to the item to be plated, moving the brush
continually to get an even distribution of the plating material.
Brush electroplating has several advantages over tank plating,
including portability, ability to plate items that for some reason
cannot be tank plated (e.g., plating portions of very large
decorative support columns in a building restoration), low or no
masking requirements, and comparatively low plating solution volume
requirements. Disadvantages compared to tank plating can include
greater operator involvement (tank plating can frequently be done
with minimal attention), and inability to achieve a plate as thick
as can be achieved using tank plating.
[0012] Measuring strain on rotating components has historically
been problematic and involves sending data out to stationary data
acquisition systems via split-ring electrical coupling or radio
frequency (RF) transmission devices. Strain gages, the associated
wiring, and/or the mass and volume of a radio transmitter can
interfere with the operation of a component, especially if
balancing is critical, if the space envelope surrounding the
component is tight, or if airflow over a surface of the component
is involved. Measuring strain on rotating components is important
to accurately assess component failure, whether it is made from a
traditional alloy or from an aforementioned alternative
material.
[0013] Plated polymeric mechanical test specimens are needed to
accurately characterize the stress and strain imposed on a plated
polymeric structure. Test specimens that are completely
encapsulated in metal plating are not preferred because such an
encapsulated specimen does not simulate a semi-infinite medium,
which best approximates plated polymer walls in actual parts. It is
more helpful to cut test specimens out of larger plated panels to
provide exposed edges (a sandwich structure) approximating a
semi-infinite medium. Preliminary testing of plated polymers
demonstrates that tensile testing of thick-plated polymers cannot
be reliably accomplished by gripping standard test specimen
geometries, such as the test specimens specified by ASTM D638.
Gripping a standard, plated test specimen results in either (1) too
much slippage to accurately or reliably calculate ultimate load,
displacement, and strain values, or (2) the test specimen being
crushed in the grip region, resulting in stress concentrations,
significant strain outside of the gage area, and premature
failure.
[0014] Therefore, there is a need for improved methods and
apparatuses for measuring strain imposed on parts, including
rotating components, that may be made from alternative materials
such as polymers, reinforced polymers, polymer matrix composites,
ceramics, and ceramic matrix composites.
SUMMARY OF THE DISCLOSURE
[0015] In accordance with one aspect of the present disclosure, a
method for repairing a plated polymer having a damaged metal layer
is disclosed. The method may include plating a damaged metal layer
until a new metal layer of desired thickness has been deposited
onto the damages metal layer.
[0016] In a refinement, the plating may be selected from the group
consisting of brush plating and brush electroplating.
[0017] In accordance with another aspect of the present disclosure,
a method for repairing a metal part having a damaged metal layer is
disclosed. The method may comprise the steps of forming a polymer
in a desired shape having an outer surface, and preparing the outer
surface to receive a catalyst. The method may further comprise
activating the outer surface with catalyst and plating a first
metal onto the outer surface and the catalyst to form a first layer
to form a structure. The method may further comprise plating a
second metal layer onto the structure and then repairing a defect
in a metal layer until a new metal layer of desired thickness has
been deposited onto the damaged meta layer.
[0018] In a refinement, the repairing a defect may be selected from
the group consisting of brush plating and brush electroplating.
[0019] In another refinement, the method may further include
depositing a third metal onto the structure.
[0020] In another refinement, the method may further include
alloying the first and second layers.
[0021] In another refinement, the method may further include
alloying the first, second and third layers.
[0022] In another refinement, the alloying of the first and second
layers process is chosen from the group consisting of transient
liquid phase (TLP) bonding, brazing, diffusion bonding, heat
treating and combinations thereof.
[0023] In another refinement, the alloying of the first, second and
third layers process is chosen from the group consisting of
transient liquid phase (TLP) bonding, brazing, diffusion bonding,
heat treating and combinations thereof.
[0024] In another refinement, the preparing of the outer surface to
receive the catalyst includes a process selected from the group
consisting of etching, abrading, reactive ion etching, ionic
activation and deposition of a conductive material.
[0025] In another refinement, the catalyst is selected from the
group consisting of palladium, platinum, gold and combinations
thereof.
[0026] In another refinement, the first metal is selected from the
group consisting of nickel, copper, silver, graphite and
combinations thereof.
[0027] In another refinement, the second metal is selected from the
group consisting of nickel, copper, silver, graphite and
combinations thereof.
[0028] In another refinement, the forming of the polymer into the
desired shape may be performed with a process selected from the
group consisting of additive manufacturing (AM), injection molding,
compression molding, blow molding, extrusion molding,
thermoforming, transfer molding, reaction injection molding and
combinations thereof.
[0029] In accordance with another aspect of the present disclosure,
a method for repairing a hollow metal part having a damaged metal
layer is disclosed. The method may comprise the steps of forming a
polymer in a desired shape having an outer surface, and preparing
the outer surface to receive an atomic layer of palladium. The
method may further comprise activating the outer surface with an
atomic layer of palladium followed by electroless plating nickel
onto the outer surface and the palladium to form a first layer
having a thickness ranging from about 0.1 to about 10 microns to
form a structure. Subsequently, copper may be electrolytically
plated onto the structure and another metal may then be plated onto
the structure. The method may further comprise removing the
polymeric material followed by repairing a defect in a metal layer
until a new metal layer of desired thickness has been deposited
onto the damaged metal layer.
[0030] In a refinement, the repairing a defect is selected from the
group consisting of brush plating and brush electroplating.
[0031] In another refinement, the structure may be alloyed.
[0032] In another refinement, the polymer my be removed by a
process selected from the group consisting of melting, etching,
application of a strong base, application of a stripping agent and
combinations thereof.
[0033] In another refinement, the preparing of the outer surface to
receive the palladium includes a process selected from the group
consisting of etching, abrading, ionic activation, deposition of a
conductive material and combinations thereof.
[0034] In another refinement, a fourth metal layer may be applied
onto the third metal layer using a process selected from the group
consisting of electrolytic plating, electroless plating,
electroforming, thermal spray coating, plasma vapor deposition,
chemical vapor deposition, cold spraying, and combinations
thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
[0035] FIG. 1A is a flow diagram illustrating the disclosed methods
of forming lightweight metal parts.
[0036] FIG. 1B illustrates, schematically, various means for
joining two molded polymeric components together prior to
plating.
[0037] FIG. 2 is a perspective view of a rotating fan assembly that
is coupled to a strain measurement system in accordance with this
disclosure, wherein the strain measurement system is shown
schematically.
[0038] FIG. 3 is a side sectional view of a fan assembly coupled to
a disclosed strain measurement system, which is shown
schematically.
[0039] FIG. 4 is a plan view of a test specimen made in accordance
with ASTM D638, Type IV, but with holes extending through both grip
portions.
[0040] FIG. 5 is a plan view of one layer of a composite layup
structure having the shape of the test specimen shown in FIG. 4,
but with reinforcing fibers, and particularly illustrating the
arrangement of the reinforcing fibers so they extend around one of
the holes in the grip portion and so that the fibers are not cut
when the hole is made. The left side of FIG. 5 illustrates the
cutting of longitudinally arranged fibers when the hole is
made.
[0041] FIG. 6 is another plan view of at least one layer of a
composite layup structure, wherein the layer includes reinforcing
fibers and the reinforcing fibers are arranged to extend around the
holes disposed in the grip portions so that the fibers are not cut
once holes are made.
[0042] FIG. 7 is another plan view of at least one layer of a
composite layup structure, wherein the layer includes reinforcing
fibers that are arranged to avoid the areas where the holes are
subsequently made, thereby avoiding cutting of the reinforcing
fibers that extend through the gauge region.
[0043] FIG. 8 is another plan view of at least one layer of a
composite layup structure, when the layer includes reinforcing
fibers that are disposed transversely to the longitudinal direction
of the layer.
[0044] FIG. 9 is another plan view of at least one layer of a
composite layup structure, wherein the layer includes reinforcing
fibers that extend around both holes in the grip portions of the
layer and proceed towards a corner of the respective grip portion
at an angle of about 45.degree. with respect to a longitudinal axis
that proceeds through the gauge region.
[0045] FIG. 10 is another plan view of at least one layer of a
composite layup structure that is similar to FIG. 9 but with an
opposite configuration and therefore portions of the fibers
extending through the grip portions and past the holes would be
disposed transversely to the corresponding fiber portions shown in
FIG. 9.
[0046] FIG. 11 is another plan view of at least one layer of a
composite layup structure, wherein the layer includes reinforcing
fibers disposed at about a 45.degree. angle with respect to a
longitudinal axis passing through the gauge region.
[0047] FIG. 12 is another plan view of at least one layer of a
composite layup structure, wherein the layer includes reinforcing
fibers disposed at about a 45.degree. angle with respect to a
longitudinal axis passing through the gauge region, but
transversely with respect to the fibers illustrated in FIG. 11.
[0048] FIG. 13 is another plan view of at least one layer of a
composite layup structure, when the layer includes reinforcing
fibers that extend longitudinally through the layer.
[0049] While the exemplary rotating component shown in the drawings
is a fan blade assembly, it will be apparent to those skilled in
the art that the disclosed strain measurement system and methods of
measuring strain imparted to a rotating component may be utilized
in connection with compressor blades, turbine blades, propeller
blades, wheels, or other components that may be fabricated from
non-traditional, non-metal, or alternative materials that are
subject to strain when the component is rotated.
DETAILED DESCRIPTION
Lightweight Parts and Components Produced from Plating Molded
Polymeric Substrates
[0050] FIG. 1A illustrates various disclosed methods for forming
lightweight parts and components in accordance with this
disclosure. In part 11, a polymer is selected for forming a desired
shape or geometry from which the part will be created. Typically,
the polymer will be acrylonitrile butadiene styrene (ABS),
polytetrafluoroethylene (PTFE), or an ABS/polycarbonate blend.
These polymers are mentioned here because they are compatible with
most etching solutions. However, other polymers that are compatible
with the selected etching solution or other evacuation method may
be utilized, as will be apparent to those skilled in the art. In
part 12, the polymer is formed or molded into the desired shape or
geometry for the metal structure.
[0051] The forming of the polymer may be carried out in any of a
variety of ways, such as additive manufacturing, injection molding,
compression molding, blow molding, extrusion molding, thermal
forming, transfer molding, reaction injection molding, and, if
applicable, combinations thereof, or other suitable forming process
as will be apparent to those skilled in the art. In part 13, if
necessary, the outer surface of the formed polymer may be prepared
for receiving a catalyst for the subsequent plating process(es).
The outer surface may be prepared in a variety of ways, such as
etching, abrading, reactive ion etching, ionic activation,
deposition of a conductive material such as graphite, silver paint,
gold sputter, etc. and, to the extent applicable, combinations
thereof.
[0052] The metals used for plating may include nickel, cobalt,
iron, copper, gold, silver, palladium, rhodium, chromium, zinc,
tin, cadmium, and alloys of the foregoing elements comprising at
least 50 wt. % of the alloy, although other metals can be used. The
plating process can be extended to a range of non-metal substrates,
including, but not limited to, polymer, reinforced polymer, polymer
matrix composite, ceramic, ceramic matrix composite, etc.
[0053] In part 14, the outer surface of the formed polymer may be
activated by applying a catalyst. Typically, the catalyst is
palladium although platinum and gold are other possibilities. The
catalyst may be applied to a thickness on the atomic scale. Prior
to the application or activation with the catalyst, the formed
polymer may be rinsed or neutralized, especially if an etching
process is carried out. Subsequent to the activation with a
catalyst, an accelerator may be optionally applied. In part 15, a
first layer of metal is deposited onto the outer surface of the
formed polymer using an electroless plating method. Typically, the
metal used to form the first layer via electroless plating is
nickel, although copper, gold, and silver are other possibilities.
After the first layer is formed on the outer surface of the formed
polymer to form a metal structure, if the desired thickness for the
metal structure has not been reached or additional material
properties are desired, a second layer of metal may optionally be
deposited on the first layer by electrolytic plating in part 16. If
the second layer is not to be succeeded by a third layer, the
second layer may be formed from a metal that is the desired
material for the finished part.
[0054] Electrolytic plating is the deposition of a metal on a
conductive material using an electric current. A component made
from a non-metal material must first be made conductive to be
electrolytically plated. This can be done through electroless
plating or by the use of conductive additives such as carbon. The
article to be electrolytically plated is immersed in a solution of
metal salts connected to a cathodic current source, and an anodic
conductor is immersed in the bath to complete the electrical
circuit. Electric current flows from the cathode to the anode, and
the electron flow reduces the dissolved metal ions to pure metal on
the cathodic surface. Soluble anodes are made from the metal that
is being plated, thereby replenishing the bath.
[0055] The polymer may be evacuated after the first or second
layers are deposited, but it may be preferable to apply successive
layer(s) of metal to the structure wherein the successive layer(s)
may be formed from a metal that is the desired material for the
finished part. The application of the optional successive layer(s)
of desired material may be carried out in a variety of ways
including, but not limited to electroplating, electroless plating,
electroforming, thermal spray coating, plasma vapor deposition,
chemical vapor deposition, cold spraying, and other techniques that
will be apparent to those skilled in the art. The successive
layer(s) of desired metal may be applied in part 17 as shown in
FIG. 1A. In part 18, at least one hole may be formed through the
structure for purposes of evacuating the polymer in part 19, unless
such a hole is an integral feature of the structure. The hole may
be formed after formation of the first layer, optional second
layer, optional successive layer, or at any time after the
structure is sufficiently strong. The hole may be patched at part
20 prior to a final heat treatment or prior to the application of
additional metallic layers in part 21. A final heat treatment can
be carried out at part 22 or the layer(s) may be alloyed via a
bonding treatment, such as transient liquid phase (TLP) bonding,
brazing, diffusion bonding, or other alloying means known to those
skilled in the art.
[0056] The final metallic part may be hollow or may be filled with
a reinforcing filler material or the polymeric article may be of a
structure that has material properties to render it suitable for
remaining within the final metallic part in a partially etched or
removed state. Suitable materials for such reinforcing filler
material are a metallic or polymeric foam, although other suitable
filler materials will be apparent to those skilled in the art.
[0057] Anti-Counterfeiting Tags
[0058] Counterfeiting has a long and ignoble history, ranging from
art and literature to manufactured goods, particularly replacement
parts. Further, counterfeiting in the aerospace, automotive, or
other transportation industries, for example, may have serious
consequences as the use of an inferior counterfeit replacement part
may create a safety hazard. Thus, there is a need to effectively
reduce the introduction of counterfeit parts into supply chains in
general and a more urgent need to reduce the presence of
counterfeit parts in supply chains of industries where the use of
counterfeit parts creates safety concerns.
[0059] An anti-counterfeiting tag may be added to a plated
polymeric article and therefore the final part. In such an
embodiment, the anti-counterfeiting tag should be detectable
through the plated structure by an appropriate sensor. Such
anti-counterfeiting tags may include a material of a different
density than the polymer(s) used to fabricate the article, a
low-level radioisotope, an RFID tag that is detectable through the
plated metal structure, a particular chemical that can be sensed in
the molded plastic article and through the plated metal structure,
or another identifier useful for anti-counterfeiting purposes as
will be apparent to those skilled in the art.
[0060] If the article is molded, the anti-counterfeiting tag may be
co-molded with the article or a protrusion can be included in the
mold tool to provide a recess for housing the anti-counterfeiting
tag. Alternatively, a slot can be machined in the polymeric article
using any manufacturing process to allow for the
anti-counterfeiting tag. A polymeric plug may be bonded over the
exposed surfaces of the anti-counterfeiting tag to provide a
completely polymeric surface for post plating. In another
embodiment, the article may be a polymeric composite layup
structure with a plurality of plies or layers and the
anti-counterfeiting tag may be disposed between adjacent plies or
layers of the layup structure.
[0061] Composite Molded Polymeric Articles
[0062] As noted above, the shaped polymeric article may be for use
as a mold and can be formed using one of the molding processes
described above and which can be plated with at least one metallic
layer to form an inexpensive metal tooling that can be economically
used to support short production runs and/or the fabrication of
test parts or components. The shaped polymeric article may also be
base for a gauge, other instrument or prototype hardware that can
be fabricated by coating the shaped polymeric article with one or
more metallic layers.
[0063] When the plated polymer component is used for tooling, it
may be advantageous to form the article with a composite layup
structure formed from one or more of the following: polyetherimide
(PEI); polyimide; polyether ether ketone (PEEK); polyether ketone
ketone (PEKK); polysulfone; nylon; polyphenylsulfide; polyester;
and any of the foregoing with fiber reinforcement e.g., carbon
fiber, glass-fiber, etc. The composite layup structure may be
compression molded into a desired shape to from a composite
article. One or more metallic layers may be deposited onto the
composite article to form a structure. If the structure is to be
used as tooling for a short term production or for the production
of test parts, the metallic layer(s) may applied by electroless
plating, electroplating, or electroforming with a thickness ranging
from about 2.54 to about 1270 microns (about 100 to about 5e+004
microinches), more typically from about 101.6 to about 1016 microns
(about 4000 to about 4e+004 microinches). This thickness range may
provide sufficient resistance to wear and impact, and/or provide
the ability to meet tight tolerance requirements and/or provide a
surface finish that will be transferred to the molded part.
[0064] The plated metallic layer(s) that forms the tooling
structure may include one or more layers. Plating may be performed
in multiple steps by masking certain areas of the molded article to
yield different thicknesses or no plating in certain areas. A
customized plating thickness profile can also be achieved by
tailored racking (including shields, thieves, conformal anodes,
etc.). Tailored racking allows for an optimization of properties
for the mold tooling with respect to heat resistance, structural
support, surface characteristics, etc. without adding undue weight
to the tooling to completely accommodate each of these properties
individually. Plating thicknesses may be tailored to the structural
requirements of the mold tooling.
[0065] Some mounting features (e.g., flanges or bosses) may be
bonded to the molded article using a suitable adhesive after
molding but before plating to simplify the mold tooling. Further,
the polymer or composite article can be fabricated in multiple
segments that are joined by any conventional process (e.g., by
welding, adhesive, mitered joint with or without adhesive, etc.)
before plating. Furthermore, molded composite articles may be
produced and plated separately and subsequently bonded by transient
liquid phase (TLP) bonding. In addition, features such as bosses or
inserts may be added (using an adhesive, riveting, etc.) to the
plated structure or tooling after the plating has been carried out.
When the molded article is to be used as a substrate formed by
injection molding and to be plated for use in a tooling, the
article may have a thickness ranging from about 1.27 to about 6.35
mm (about 0.05 to about 0.25 inch), with localized areas ranging up
to 12.7 mm (0.5 inch). In contrast, compression molding can be used
to form a molded article with a wall thicknesses ranging from about
1.27 to about 51 mm (about 0.05 to about 2.008 inch).
[0066] For some parts with complex geometries and/or that are
large, multiple-piece mold toolings are required because the molded
part cannot be reliably released from a single mold. Thus, to
fabricate tooling for such a part with complex geometry and/or that
is large, the part may be divided into a plurality of segments,
which may be coupled. Possible weak points caused by the joining of
two segments together may be overcome by joining the two segments
using one or more joints in combination an adhesive that remains
within the joint so that the adhesive is not exposed to or
"visible" to a subsequent plating process. The types of joints that
may be suitable for coupling two such polymer segments together
include mitered joints, angled joints, angled-mitered joints,
welded joints with covers, mitered joints with low angle
boundaries, mitered joints with accommodation channels for
accommodating extra adhesive, welded joints with a cover, slot-type
attachments with our without an additional fastener, and others as
will be apparent to those skilled in the art. Then, the two
segments are plated together using one of the plating methods
described above. By plating one or more layers over the joint and
over the outer surfaces of two segments, possible structural weak
points created by the coupling of the two segments are avoided.
Suitable adhesives include epoxy-based adhesives in liquid, paste,
or film form, with long-term service temperatures of up to
121.degree. C. (249.8 degree Fahrenheit), and bismaleimide-based
adhesives with service temperatures of up to 177.degree. C. (350.6
degree Fahrenheit) (in paste or film form). In addition,
cyanoacrylates and polyurethanes could be used in certain
situations, depending upon the strength and rigidity
requirements.
[0067] The plating material and thickness may be selected such that
a structural analysis would indicate that the plating layer will
take the majority of the loads that the part experiences.
Furthermore, geometric features are optionally added into the
design to mitigate any weakness caused by the joining to two
segments together prior to the plating.
[0068] Temporary or short-run tooling may be made using the
disclosed methods, particularly if the molded article is fabricated
from a composite layup structure that is sufficiently stiff, but
which can be compression molded. The compression molded composite
article serves as a substrate that may be plated to form a
tooling.
[0069] Plating of Joined Polymeric Articles
[0070] Conventional processes for fabricating polymeric parts
(e.g., injection or compression molding) have limitations with
respect to geometric complexity and part size. In particular, large
parts (by volume or weight) may exceed the capabilities of
available injection molding machines or compression presses.
Complex geometry or features within a part may also make it
difficult to form and successfully release the part from the mold
tooling. Complex geometries or features may also require very
intricate multi-piece mold designs.
[0071] Therefore, an ability to fabricate separate part details and
join them into an assembly may offer cost benefits in these
situations. By plating a polymeric part with a suitable plating
material to a suitable thickness, the structural weak points that
are caused by bonding may be overcome.
[0072] An exemplary substrate may be a molded structure formed of
at least one material selected from the group consisting of:
polyetherimide (PEI); polyimide; polyether ether ketone (PEEK);
polysulfone; Nylon; polyphenylsulfide; polyester; and any of the
foregoing with fiber reinforcements e.g., carbon fibers or
glass-fibers. Suitable adhesives for joining the molded substrates
include epoxy-based adhesives in liquid, paste or film form, with
long-term service temperatures for aerospace applications of up to
250.degree. F. (121.degree. C.), and bismaleimide (BMI) based
adhesives in paste or film forms with service temperatures of up to
350.degree. F. (177.degree. C.). Also, cyanoacrylates and
polyurethanes could be used in selected cases depending on strength
and rigidity requirements.
[0073] Plating on adhesives can be difficult and causes deviations
in plating properties. FIG. 1B schematically illustrates a variety
of methods or joints that can be used to join polymeric substrate
segments together so that bond line effects are minimized and only
the polymeric material is visible to the plating process. The
methods or joints include, but are not limited to a mitered joint
31, an angled joint 32, an angled mitered joint 33, a welded joint
34 with covers 35 that may be press-fit into place or secured with
adhesive or weld beads 36, a mitered joint 37 with low angle
boundaries, a mitered joint 38 with accommodation channels 39 for
extra adhesive, a slot attachment-type joint 41, a welded T-joint
42 with a cover 43, a mitered joint 44 attached with a fastener 45,
and others as will be apparent to those skilled in the art.
Further, two component halves may be joined to create one or more
tortuous passages. Also, components with ducts of different cross
sections may be economically molded and joined together. Any
combination of these and similar methods can be used to create
plated polymeric parts with geometries and/or sizes that are
outside the limits or economic feasibility of conventional molding
processes.
[0074] The plating material and thickness may be selected such that
a structural analysis indicates that the plating layer will take
the majority of the loads that the part experiences. Furthermore,
geometric features are optionally added into the design to mitigate
the bond line property knockdowns.
[0075] Thus, plated polymeric parts can be produced on a larger
scale than the capacity limits of injection or compression-molding
processes currently allow. Part geometries for plated polymeric
parts can be more complicated than the injection or
compression-molding processes can allow. Part cost can be reduced
when complex parts that are difficult to mold are molded in
multiple, simpler segments. The plating material and thickness are
selected to accommodate weaknesses induced by bond lines and
bonding methods.
[0076] Polyimide and Bismaleimide Resins
[0077] High temperature organic matrix composites (OMCs) such as
polyimides and bismaleimides (BMIs) are typically formed into a
desired shape by autoclave molding, compression molding or
resin-transfer molding. These molding processes all require lengthy
cure and post-cure cycles as well as costly mold toolings, which
have long lead times. These molding methods are also limited in
terms of the geometrical complexity of the desired shape of the
molded article.
[0078] Additive manufacturing (AM) or three-dimensional (3D)
printing is a process of making a three-dimensional solid object of
virtually any shape from a digital model. AM is achieved using an
additive process, wherein successive layers of material are laid
down in different shapes. AM is considered distinct from
traditional machining techniques, which mostly rely on the removal
of material by methods such as cutting or drilling, i.e.,
subtractive processes. A materials printer usually performs AM
processes using digital technology. Since the start of the
twenty-first century there has been a large growth in the sales of
these machines, and while the price has dropped substantially, AM
remains very costly. Despite its high cost, AM is used in many
fields, including aerospace.
[0079] In the disclosed methods, imidized polyimide resin and/or
bismaleimide resin (BMI) may be used to form desired shapes by
additive manufacturing (AM). The resins may be solids at room
temperature and may be ground and sieved to the appropriate size
for powder bed processing (SLS) or the solid resin can be melted
for liquid bed processing (SLA). The resulting AM article can then
be plated to provide additional strength, thermal capability,
erosion resistance, etc., and combinations thereof. The plating
layer may include one or more layers. The metallic layer may be
applied by electroless plating, electroplating, or electroforming.
One especially useful application is for wear parts such as
bushings, liners, and washers, which have extensive applications in
gas turbine engines and in other manufacturing industries.
[0080] Strain Measurement on Non-Metal Components with Plated
Targets
[0081] FIG. 2 illustrates a fan blade assembly 110 that is coupled
to a strain measurement system 111. The fan blade assembly 10
includes a plurality of fan blades 112 that are coupled to a rotor
or disk 113. To save weight, the fan blades 112 may be fabricated
from non-metallic materials, such as polymers, reinforced polymers,
polymer matrix composites, ceramics, ceramic matrix composites,
etc.
[0082] However, because failure of a fan blade 112 of a fan blade
assembly 110 of a gas turbine engine presents a safety hazard,
measuring the strain imposed on the fan blades 112 during rotation
of the fan blade assembly 110 may be desirable. FIG. 2 therefore
illustrates schematically a strain measurement system 111 that
includes a first encoder 114 (or other suitable type of sensor), a
second encoder 115 (or other suitable type of sensor), a controller
116, which may be integrated with the first and second encoders 114
and 115, respectively, a first electromagnetic target 117 disposed
on the fan blade 112 and a second electromagnetic target 118, also
disposed on the fan blade 112 and spaced apart from the first
electromagnetic target 117 by a distance shown as D. The first and
second electromagnetic targets may be plated onto the fan blade
112.
[0083] When the fan blade 112 is stationary, or is otherwise not
under significant strain or stress, the first and second
electromagnetic targets 117, 118 are spaced apart by an initial
distance D.sub.1. As the fan blade assembly 110 is rotated, the
centrifugal forces experienced by the fan blade 112 may impart
strain to the fan blade 112 thereby changing the distance between
the first and second electromagnetic targets 117 and 118,
respectively from the initial distance D.sub.1 to an actual
distance D.sub.2. The first and second encoders 114 and 115,
respectively, are designed to monitor the actual positions of the
first and second electromagnetic targets 117 and 118, respectively.
Those actual positions may be transmitted to the controller 116,
which may be a separate component or which may be integral with the
first and second encoders 114 and 115, respectively. The controller
116 may have a memory 119 that may be programmed with at least one
program for determining the actual distance D.sub.2 based upon the
signals received from the first and second encoders 114 and 115,
respectively. The memory 119 of the controller 116 may also be
programmed with an algorithm for calculating strain imparted to the
fan blade 112 during rotating thereof based on the differences
between the actual distance D.sub.2 and the initial distance
D.sub.1. Information relating to the strain imparted to the fan
blade 112 may then be transmitted to the operator or pilot of the
aircraft or the main control module of the aircraft.
[0084] FIG. 3 illustrates the fan blade assembly 110 as disposed
within a nacelle 121. FIG. 2 also partially illustrates the rotor
113 coupled to a nose cone 122. It will be noted that the encoders
114 and 115 may be different types of sensors and/or may
incorporate Hall-effect sensors as well. If the encoders/sensors
114 and 115 incorporate Hall-effect sensors, the encoders/sensors
114 and 115 may also measure the rotational velocity of the fan
blade 112.
[0085] Strain Measurement on Thick, Plated Polymer and/or Composite
Components
[0086] Preliminary testing of plated polymers has demonstrated that
tensile testing of thick-plated polymers cannot be reliably
accomplished by using conventional gripping techniques on grip
portions of standard test specimen geometries. This conventional
method produces either (1) far too much slippage to accurately or
reliably calculate ultimate load, displacement, and strain values,
or (2) crushes the test specimen in the grip area, resulting in
stress concentrations, significant strain outside of the gage area,
and premature failure.
[0087] Using a 30% carbon-fiber-reinforced amorphous thermoplastic
(polyetherimi de, commonly known as ULTEM.RTM.) with 0.008 in (0.2
mm (0.007874 inch)) nominal Ni plating, the amount of slippage
could be neglected for a Type IV specimen tested in accordance with
the ASTM D638 protocol. In contrast, using a Type IV specimen and
testing under ASTM D638 and with a 0.015 in (0.38 mm (0.01496
inch)) nominal Ni plating, the amount of slippage was severe enough
that absolute displacement (and therefore strain) values could not
be accurately obtained. As a solution to this problem, a pin-loaded
tensile specimen in accordance with ASTM D638, Type IV may be used,
preferably with two spaced-apart holes drilled therein to allow for
pin loading of the specimen. For example, referring to FIG. 4, the
overall length of the specimen 200 may be about 12.7 cm (5 inches)
and the centers of the holes 201 may be spaced apart by about 9.616
cm (3.786 inches). The holes may have about a 0.653 cm (0.2571
inch) diameter and may be centered longitudinally in the wider end
portions or the grip regions 202 of the Type IV specimen 200. The
grip regions 202 may have a width of about 1.91 cm (0.752 inch).
The arcs 203 connecting the grip regions 202 to the narrow middle
gauge region 204 may have a radius of about 2.54 cm (1 inch). The
length of the middle gauge region 204 may be about 3.175 cm (1.25
inches).
[0088] The hole 201 sizes may be optimized using certain
parameters. For example, plating thickness, width of the gage
region, hole diameter, and width between the hole edge and the
specimen side edges, and end edge may be used to define a working
space for test geometry.
[0089] Bushings 205 may be inserted in the holes 201 to carry the
load more evenly. Alternatively, the holes 201 can be machined in
the polymer before plating to provide plating in the loading holes
201. These holes 201 can incorporate fillets to prevent a buildup
of plating (nodulation), or the buildup of plating that would
otherwise occur should be machined off to prevent stress
concentrations. Alternative hole shapes such as square, slot, and
diamond can also be incorporated in flat specimen geometries. An
alternative method is to machine the test specimen 200 before
plating and mask the edges of the gage region 204 before plating,
thereby providing for the exposed edges along the gage region 204
and completely encapsulating the grip regions 202. This method
accommodates testing the specimen 200 for some thicker platings by
gripping as the encapsulated grip regions 202, which provide
increased resistance to crushing.
[0090] A range of alternate (non-flat) geometries can be used for
the grip regions 202 to obtain accurate load-displacement data for
plated polymeric structures using a flat gage region 204 with
exposed edges (two-dimensional stress state). One such geometry for
the grip regions 202 is conical, wherein the flat grip regions 202
of the test specimen 200 may be reconfigured into conically-shaped
grip regions (not shown) on each end of the narrow middle gauge
region of the test specimen 200, thereby accommodating loading by
conical grips. In an I-beam configuration, a flat tensile specimen
like that shown at 200 in FIG. 4 is provided, but with transverse
members at or near the end of specimen instead of the conventional
grip portions 202 shown in FIG. 4. The transverse members may be
used to load the specimen using a clevis, hooks, loops, ledges,
etc. This method can also accommodate flat sections or rods as the
protruding components of the I-beam. In a flared configuration, a
flat tensile specimen with flared edges at the ends thereof may
provide for gripping using platens set at angles, thereby providing
a hybrid between standard tensile grips and conical grips. If any
sections of the test specimen geometries are prone to develop
porosity during a molding process (e.g., injection molding), they
can be hollowed out before forming. Further, reinforcing ribs can
be added to hollow sections, as necessary, to prevent failure in
grip areas.
[0091] Suitable test specimens may also be fabricated from
composite layup structures having a plurality of layers or plies,
at least some of which include reinforcing fibers. Turning to FIGS.
5-13, various layers 220, 230, 240, 250, 260, 270, 280, 290, 300 of
possible composite layup structures are shown. FIG. 5 illustrates a
problem created when holes 201 are drilled or punched through grip
regions 202 through which reinforcing fibers 211 pass.
Specifically, on the left side of FIG. 5, the creation of the hole
201 results in a number of the fibers 211 being cut or broken,
resulting in a high amount of shear transfer required to transfer
the load around the hole 201. Referring to the hole 201 shown at
the left in FIG. 5, it is extremely likely that a tensile specimen
fabricated from the layer 220 would fail near the hole 201 shown at
the left in FIG. 5. As a solution to this problem, the fibers 211
are rearranged on the right side of the layer 220 shown in FIG. 5.
Specifically, the fibers 211 are arranged so they wrap or extend
around the hole 201 shown at the right in FIG. 5 (see also FIGS. 6,
9-10). The fibers 211 that extend around the hole 201 shown at the
right in FIG. 5 are able to take the bearing load when accommodated
by symmetric fibers, as shown in FIG. 6. The layer 230 shown in
FIG. 6 would complement a layer such as that shown at 220 in FIG. 5
because the fibers 211 wrap around the holes 201 in opposite
directions and therefore the layers 220, 230 could be used as
alternating layers in a composite layup structure.
[0092] Similarly, the layers 240, 250 of FIGS. 7-8 respectively
could complement each other if used as alternating plies in a
composite layup structure as the layer 240 includes fibers 211 that
extend longitudinally through the layer 240 and around the holes
201 in a Y arrangement. To complement the arrangement shown in the
layer 240 of FIG. 7, fibers 211 that extend transversely to a
longitudinal axis of the layer 250 are shown in FIG. 8. Thus, the
fibers 211 of FIG. 8 extend substantially transversely to the
fibers 211 of FIG. 7 and therefore the layers 240 and 250, when
used as alternating layers in a composite layup structure, are able
to complement each other and provide resistance to tearing at the
bearing hole. Similarly, such a complementary, transverse
relationship may be created by using the layers 260, 270 of FIGS.
9-10 in an alternating fashion. Another example of suitable
alternating plies or layers is illustrated by the layers 280 and
290 of FIGS. 11-12 (.+-.45.degree.) as well as the layers 250 and
300 of FIGS. 8 and 13 (0.90.degree.).
[0093] Thus, composite materials may be used as a substrate that is
plated to form a lightweight but strong metallic part, such as a
case, duct, housing, enclosure, panel, etc. Other metallic parts
that can be fabricated from a shaped composite article or substrate
that is plated with one or more metallic layers will be apparent to
those skilled in the art.
[0094] Brush Plating for Repair of Plated Polymer Parts
[0095] The interfacial strength between the plating and polymer
materials in a plated polymeric structure is the weak point and can
be structurally limiting. When plating does not adhere to the
polymeric substrate, due to activation problems, contamination,
etc., or if the plating gets nicked, dented or scratched, it can be
cost effective to repair the plated polymer component rather than
scrapping it. To repair a plated polymer part or component, brush
plating or brush electroplating may be employed.
[0096] In brush plating, localized areas or entire parts may be
plated using a brush saturated with plating solution. The brush is
typically a stainless steel or graphite body wrapped with a cloth
material that both holds the plating solution and prevents direct
contact with the part being plated. The brush connects to the
positive side of a low voltage direct-current power source, and the
item to be plated connected to the negative side. Solution is
pumped through a plating wand to maintain a fresh supply of
solution. The operator dips the brush in the plating solution and
then applies the brush to the part, moving the brush continually to
get an even distribution of the plating solution over the part.
Brush electroplating has several advantages over tank plating,
including portability and ability to plate parts that for some
reason cannot be tank plated, such as very large parts. Brush
electroplating involves little or no masking requirements and uses
comparatively little plating solution. Disadvantages compared to
tank plating can include greater operator involvement (tank plating
can frequently be done with minimal attention), and the inability
to achieve as great a plate thickness.
[0097] The mechanics of brush plating are relatively
straightforward. A 110-volt AC power pack converts the voltage into
DC current. A ground cable carrying a negative charge is connected
to the article being plated, which renders the article as the
cathode. A second cable is carrying a positive charge is connected
to the brush or plating tool, which makes it the anode. The brush
is wrapped in an absorbent material, which holds the plating
solution between the anode (the brush) and the cathode (the article
being plated). Electrical current travels from the brush, through
the plating solution to the work area on the article being plated.
Plating occurs only when and where the brush contacts the article.
Little to no heat is generated throughout the plating process,
therefore no internal stress or heat distortions are imparted to
the article. The metallic layer is dense, hard, corrosion resistant
and metallurgically sound.
[0098] A closely related process is brush electroplating. In brush
electroplating, an article is also plated using a brush saturated
with a plating solution. The brush is typically made of stainless
steel and wrapped with a cloth material that holds the plating
solution. The cloth as prevents direct contact between the
stainless steel brush and the item being plated. The brush is
connected to the positive side of a low voltage DC power source,
and the article to be plated is connected to the negative side of
the DC power source. After the brush is dipped in the plating
solution, the brush is moved continually over the surface of the
article to achieve an even distribution of the plating material to
form a metallic layer. The brush as the anode, typically does not
contribute any plating material.
[0099] Repairing damaged areas of plated polymer components and
restoring full membrane strength of the plating using an economical
brush plating process can mean cost savings, extended service life
and improved physical appearance of the part.
[0100] Use of Brush Plating in the Balancing of Polymer Components
and Plated Polymer Components
[0101] Rotating components, such as tires, spinners and fan
platforms, typically must be balanced. The balancing of a rotating
component is often achieved by attaching a metal weight or bonding
one or more weights to an interior of the component. Currently, one
balance method is to use metal powder filled resins as balance
"putty" and this putty may be bonded to the component. Disclosed
herein are brush plating and brush electroplating techniques, which
can be used to balance rotating components.
[0102] In brush plating, localized areas or entire parts may be
plated using a brush saturated with plating solution. The brush is
typically a stainless steel or graphite body wrapped with a cloth
material that both holds the plating solution and prevents direct
contact with the part being plated. The brush connects to the
positive side of a low voltage direct-current power source, and the
item to be plated connected to the negative side. Solution is
pumped through a plating wand to maintain a fresh supply of
solution. The operator dips the brush in the plating solution and
then applies the brush to the part, moving the brush continually to
get an even distribution of the plating solution over the part.
Brush electroplating has several advantages over tank plating,
including portability and ability to plate parts that for some
reason cannot be tank plated, such as very large parts. Brush
electroplating involves little or no masking requirements and uses
comparatively little plating solution. Disadvantages compared to
tank plating can include greater operator involvement (tank plating
can frequently be done with minimal attention), and the inability
to achieve as great a plate thickness.
[0103] The mechanics of brush plating are relatively
straightforward. A 110-volt AC power pack converts the voltage into
DC current. A ground cable carrying a negative charge is connected
to the article being plated, which renders the article as the
cathode. A second cable is carrying a positive charge is connected
to the brush or plating tool, which makes it the anode. The brush
is wrapped in an absorbent material, which holds the plating
solution between the anode (the brush) and the cathode (the article
being plated). Electrical current travels from the brush, through
the plating solution to the work area on the article being plated.
Plating occurs only when and where the brush contacts the article.
Little to no heat is generated throughout the plating process,
therefore no internal stress or heat distortions are imparted to
the article. The metallic layer is dense, hard, corrosion resistant
and metallurgically sound.
[0104] A closely related process is brush electroplating. In brush
electroplating, an article is also plated using a brush saturated
with a plating solution. The brush is typically made of stainless
steel and wrapped with a cloth material that holds the plating
solution. The cloth as prevents direct contact between the
stainless steel brush and the item being plated. The brush is
connected to the positive side of a low voltage DC power source,
and the article to be plated is connected to the negative side of
the DC power source. After the brush is dipped in the plating
solution, the brush is moved continually over the surface of the
article to achieve an even distribution of the plating material to
form a metallic layer. The brush as the anode, typically does not
contribute any plating material.
[0105] Thus, brush plating and/or brush electroplating may be used
to selectively plate a component, while it is rotating, or in-situ.
Brush plating and brush electroplating are performed much faster
than conventional plating (about 10 mils per hour) and provides a
higher-strength bond than an adhesive. The exact thickness of the
plating required may depend on the density of the weight, and the
proper density the weight and the mass of the weight required to
balance the component can be determined prior to the brush
plating.
[0106] An alternate method may be to fix a balance weight (metal,
polymer, or any other material) in place on the rotatable
component, and use in-situ brushed plating to permanently entrap
the weight onto the component. The plating layer(s) may extend
beyond the weight, entrapping the weight against the rotating
component, while providing superior bonding of the weight to the
component as the plating layer is bonded to both the weight and the
substrate.
INDUSTRIAL APPLICABILITY
[0107] Various means for forming lightweight metal parts or hollow
metal parts are disclosed. A polymer suitable for being plated is
selected and formed into an article of a desired shape by
injection-molding, blow-molding, compression-molding or additive
manufacturing. The outer surface of the formed article may be
prepared for receiving a catalyst via etching, abrading, reactive
ion etching, deposition of a conductive material, etc. Depending
upon the process utilized to prepare the polymeric substrate, the
outer surface may need to be rinsed or subjected to a neutralizing
solution. Then, the outer surface may be activated with a catalyst
such as palladium. Optionally, an accelerator may be applied before
an electroless plating of a first layer of metal onto the outer
surface of the formed polymers is carried out to form a metallic
structure. The first layer of metal is typically electroless
nickel. Then, if electroless nickel is not the desired material for
the finished product or if the desired thickness has not been
reached, an optional second layer of metal may be electrolytically
plated onto the structure wherein the second layer of metal may
typically be copper. If the desired thickness has not been reached
or a different metal is desired for the final structure, one or
more optional metallic layers may be applied to the structure. The
additional metallic layer(s) may be applied via electroplating,
electroless plating, electroforming, thermal spray coating, plasma
vapor deposition, chemical vapor deposition, cold spraying, or, to
the extent applicable, combinations thereof.
[0108] The polymer may be evacuated from the formed structure using
an opening integral to the structure or through a hole formed in
the structure. The polymer may be evacuated by etching, melting,
applications of strong base and/or stripping agents or another
suitable process as will be apparent to those skilled in the art.
The hole(s) may then be plugged and additional metallic layers may
be deposited onto the structure. A heat treatment may be carried
out which may alloy or produce certain desired metallurgical
reactions (these reactions include, but are not limited to the
formation of inter-metal phases, solution treating, and
precipitation hardening) in the layer(s). This heat treatment may
be carried out in the form of transient liquid phase bonding,
brazing, diffusion bonding, or other processes that will be
apparent to those skilled in the art.
* * * * *