PROCESS INCLUDING CONVERTING RESISTIVE POWDER TO FUSED HEATER
ELEMENT USING LASER METAL DEPOSITION APPARATUS
TECHNICAL FIELD
An aspect of the present invention generally relates to (but is not limited to) a process,
including (but not limited to): converting a resistive powder to a fused heater element by
using a laser metal deposition apparatus.
BACKGROUND
The first man-made plastic was invented in Britain in 1851 by Alexander PARKES. He
publicly demonstrated it at the 1862 International Exhibition in London, calling the material
Parkesine. Derived from cellulose, Parkesine could be heated, molded, and retain its shape
when cooled. It was, however, expensive to produce, prone to cracking, and highly
flammable. In 1868, American inventor John Wesley HYATT developed a plastic material
he named Celluloid, improving on PARKES' invention so that it could be processed into
finished form. HYATT patented the first injection molding machine in 1872. It worked like a
large hypodermic needle, using a plunger to inject plastic through a heated cylinder into a
mold. The industry expanded rapidly in the 1940s because World War I I created a huge
demand for inexpensive, mass-produced products. In 1946, American inventor James
Watson HENDRY built the first screw injection machine. This machine also allowed material
to be mixed before injection, so that colored or recycled plastic could be added to virgin
material and mixed thoroughly before being injected. In the 1970s, HENDRY went on to
develop the first gas-assisted injection molding process.
Injection molding machines consist of a material hopper, an injection ram or screw-type
plunger, and a heating unit. They are also known as presses, they hold the molds in which
the components are shaped. Presses are rated by tonnage, which expresses the amount of
clamping force that the machine can exert. This force keeps the mold closed during the
injection process. Tonnage can vary from less than five tons to 6000 tons, with the higher
figures used in comparatively few manufacturing operations. The total clamp force needed
is determined by the projected area of the part being molded. This projected area is
multiplied by a clamp force of from two to eight tons for each square inch of the projected
areas. As a rule of thumb, four or five tons per square inch can be used for most products.
If the plastic material is very stiff, it will require more injection pressure to fill the mold, thus
more clamp tonnage to hold the mold closed. The required force can also be determined by
the material used and the size of the part, larger parts require higher clamping force. With
Injection Molding, granular plastic is fed by gravity from a hopper into a heated barrel. As
the granules are slowly moved forward by a screw-type plunger, the plastic is forced into a
heated chamber, where it is melted. As the plunger advances, the melted plastic is forced
through a nozzle that rests against the mold, allowing it to enter the mold cavity through a
gate and runner system. The mold remains cold so the plastic solidifies almost as soon as
the mold is filled. Mold assembly or die are terms used to describe the tooling used to
produce plastic parts in molding. The mold assembly is used in mass production where
thousands of parts are produced. Molds are typically constructed from hardened steel, etc.
Hot-runner systems are used in molding systems, along with mold assemblies, for the
manufacture of plastic articles. Usually, hot-runners systems and mold assemblies are
treated as tools that may be sold and supplied separately from molding systems.
US Patent Number 48971 50 discloses direct write techniques wherein, for example, an
electron beam "writes" a pattern in photoresist on an integrated circuit or other semiconductive
element. Some of these prior direct write techniques have also included the use
of laser beams. Such laser assisted deposition techniques involve the deposition of metal
from an organometallic gas or polysilicon from silane (SiH4).
US Patent Number 7001467 discloses a device and method for depositing a material of
interest on a receiving substrate includes a first laser and a second laser, a receiving
substrate, and a target substrate. The target substrate comprises a laser transparent
support having a back surface and a front surface. The front surface has a coating that
comprises the source material, which is a material that can be transformed into the material
of interest. The first laser can be positioned in relation to the target substrate so that a laser
beam is directed through the back surface of the target substrate and through the lasertransparent
support to strike the coating at a defined location with sufficient energy to
remove and lift the source material from the surface of the support. The receiving substrate
can be positioned in a spaced relation to the target substrate so that the source material is
deposited at a defined location on the receiving substrate. The second laser is then
positioned to strike the deposited source material to transform the source material into the
material of interest.
A conducting silver line was fabricated by using a UV laser beam to first transfer the coating
from a target substrate to a receiving substrate and then post-processing the transferred
material with a second IR laser beam. The target substrate consisted of a UV grade fused
silica disk on which one side was coated with a layer of the material to be transferred. This
layer consisted of Ag powder (particle size of a few microns) and a metalloorganic
precursor which decomposes into a conducting specie(s) at low temperatures (less than
200° C). The receiving substrate was a microwave-quality circuit board which has various
gold electrode pads that are a few microns thick. A spacer of 25-micron thickness was used
to separate the target and receiving substrates.
Silver was first transferred with a focused UV (l=248 nm or l=355) laser beam through the
target substrate at a focal fluence of 225 mJ/cm2. The spot size at the focus was 40 m h in
diameter. A line of "dots" was fabricated between two gold contact pads by translating both
the target and receiving substrates together to expose a fresh area of the target substrate
for each laser shot while the laser beam remained stationary. The distance between the
laser spots was approx. one spot diameter. A pass consisted of approximately 25 dots and
a total of 10 passes (superimposed on one another) was made. The target substrate was
moved between each pass. After the transfers, the resistance between the gold pads as
measured with an ohmmeter was infinite (>20-30 Megaohms).
US Patent Number 7014885 discloses device and method that is useful for creating a
deposit of electrically conducting material by depositing a precursor material or a mixture of
a precursor material and an inorganic powder that is transformed into an electrical
conductor. For creating deposits of metals, such as for conductor lines, any precursors
commonly used in chemical vapor deposition (CVD) and laser-induced chemical vapor
deposition (LCVD) may be used. Examples include, but are not limited to, metal alkoxides,
metal diketonates and metal carboxalates.
US Patent Number 5 132248 discloses a process for deposition of material on a substrate,
for example, the deposition of metals or dielectrics on a semiconductor laser, the material is
deposited by providing a colloidal suspension of the material and directly writing the
suspension on the substrate surface by ink jet printing techniques. This procedure
minimizes the handling requirements of the substrate during the deposition process and
also minimizes the exchange of energy between the material to be deposited and the
substrate at the interface. The deposited material is then resolved into a desired pattern,
preferably by subjecting the deposit to a laser annealing step. The laser annealing step
provides high resolution of the resultant pattern while minimizing the overall thermal load of
the substrate and permitting precise control of interface chemistry and inter-diffusion
between the substrate and the deposit.
SUMMARY
The inventors have researched a problem associated with known molding systems that
inadvertently manufacture bad-quality molded articles or parts. After much study, the
inventors believe they have arrived at an understanding of the problem and its solution,
which are stated below, and the inventors believe this understanding is not known to the
public.
Current heater construction typically involves packaging of a nichrome wire element (nickelchromium
resistance wire) in various forms. More advanced methods may use screen
printed techniques requiring high firing temperatures and/or customized screens for each
configuration. Other known methods may rely on thermal spray application of a layer and
selectively removing portions of the layer to produce the desired heating element. For
example, additional known methods may relay on thermal spray techniques in which a
specialized mask is used to create the desired heater configuration and pattern. Still other
known methods may utilize inkjet style print heads with the resistive medium suspended in
a solvent or other liquid to directly write a patterned heater onto a substrate.
According to one aspect, there is provided a process (200), comprising: a transfer operation
(204), including transferring a resistive powder (106) to an electrically insulated element
(102); and a converting operating (206), including converting at least some of the resistive
powder (106) to a fused heater element (108) by using a laser metal deposition apparatus
(110), the fused heater element (108) being fused to the electrically insulated element
(102).
Other aspects and features of the non-limiting embodiments will now become apparent to
those skilled in the art upon review of the following detailed description of the non-limiting
embodiments with the accompanying drawings.
DETAILED DESCRIPTION OF THE DRAWINGS
The non-limiting embodiments will be more fully appreciated by reference to the following
detailed description of the non-limiting embodiments when taken in conjunction with the
accompanying drawings, in which:
FIG. 1 depicts a schematic representation of a laser metal deposition apparatus (110);
FIG. 2 depicts another schematic representation of the laser metal deposition apparatus
(110) of FIG. 1; and
FIG. 3 depicts a schematic representation of a process (200) for using the laser metal
deposition apparatus (110) of FIG. 1 or FIG. 2.
The drawings are not necessarily to scale and may be illustrated by phantom lines,
diagrammatic representations and fragmentary views. In certain instances, details not
necessary for an understanding of the embodiments (and/or details that render other details
difficult to perceive) may have been omitted.
DETAILED DESCRIPTION OF THE NON-LIMITING EMBODIMENT(S)
FIG. 1 depicts the schematic representation of the laser metal deposition apparatus (110).
Mold-tool systems, hot-runner systems and molding systems may include, at least in part,
components that are known to persons skilled in the art, and these known components will
not be described here; these known components may be described, at least in part, in the
following reference books (by way of example): (i) "Injection Molding Handbook ' authored
by OSSWALD/TURNG/G RAMAN N (ISBN: 3-446-21 669-2), (ii) "Injection Molding
Handbook authored by ROSATO AND ROSATO (ISBN: 0-41 2-99381 -3), (iii) "Injection
Molding Systems" 3 Edition authored by JOHANNABER (ISBN 3-446-1 7733-7) and/or (iv)
"Runner and Gating Design Handbook authored by BEAUMONT (ISBN 1-446-22672-9). It
will be appreciated that for the purposes of this document, the phrase "includes (but is not
limited to)" is equivalent to the word "comprising". The word "comprising" is a transitional
phrase or word that links the preamble of a patent claim to the specific elements set forth in
the claim which define what the invention itself actually is. The transitional phrase acts as a
limitation on the claim, indicating whether a similar device, method, or composition infringes
the patent if the accused device (etc) contains more or fewer elements than the claim in the
patent. The word "comprising" is to be treated as an open transition, which is the broadest
form of transition, as it does not limit the preamble to whatever elements are identified in
the claim.
An electrically insulated element (102) is placed on a substrate (104). A resistive powder
(106) is placed on the electrically insulated element (102). At least some of the resistive
powder (106) is converted to a fused heater element (108) by using a laser metal
deposition apparatus (110). The fused heater element (108) becomes fused to the
electrically insulated element (102). The electrically insulated element (102) may include a
layer of insulation material. The substrate (104) may include, for example, a layer of
substrate material.
Examples of the electrically insulated element (102) may include: aluminum nitride,
aluminum oxide, magnesium oxide, zirconia, mica, diamond, etc. Example of the substrate
(104) may include: carbon steel, tool steel, stainless steel, copper and copper based alloys,
aluminum, titanium, aluminum nitride, aluminum oxide, silicon carbide, or other metallic or
ceramic materials. Example of the resistive powder (106) may include: nickel-chromium
(also known as ni-chrome), conductive ceramics, tungsten, etc.
According to a first variation, the placing of the resistive powder (106) on the electrically
insulated element (102) includes (but is not limited to): using a feeder nozzle (1 12) to spray
the resistive powder (106) on the electrically insulated element (102).
FIG. 2 depicts another schematic representation of the laser metal deposition apparatus
(110) of FIG. 1. According to a second variation, the placing of the resistive powder (106)
on the electrically insulated element (102) includes (but is not limited to): depositing the
resistive powder (106) as a layer on the electrically insulated element (102).
FIG. 3 depicts a schematic representation of the process (200) for using the laser metal
deposition apparatus (110) of FIG. 1 or FIG. 2. The process (200) includes (but is not
limited to): (i) a fixing operation (202); (ii) a transfer operation (204); and (iii) a converting
operating (206). The fixing operation (202) includes (but is not limited to): fixing the
electrically insulated element (102) on a substrate (104). The transfer operation (204)
includes (but is not limited to): transferring a resistive powder (106) to the electrically
insulated element (102). The converting operating (206) includes (but is not limited to):
converting at least some of the resistive powder (106) to a fused heater element (108) by
using a laser metal deposition apparatus (110). The fused heater element (108) then
becomes fused to the electrically insulated element (102).
It will be appreciated that the laser metal deposition apparatus (110) may be used to create
or to form a customized heater profile (wattage and watt distribution) in a single write step.
By directly writing the heater element, that is, using the converting operating (206), the cost
may be reduced and the number of steps required to produce the fused heater element
(108) are also reduced. In addition, the ability to articulate a laser head of the laser metal
deposition apparatus (110) may allow a build up of the fused heater element (108) on a
contoured surface, and/or a complex-shaped surface.
The laser metal deposition apparatus (110) uses a laser energy source to fuse the resistive
powder (106) on the electrically insulated element (102), such as a ceramic including
magnesium oxide or aluminum oxide, as well as diamond based materials. Several method
may be used to position the resistive powder (106) on the over the electrically insulated
element (102). The resistive powder (106) may be: (i) fed into a laser beam using a
compressed gas (as depicted in FIG.1), or (ii) may be spread over a surface to a prescribed
thickness and selectively fused to the substrate (104) using the laser beam path to
determine the element configuration (as depicted in FIG. 2). Additional passes of a laser
beam may be used to make thicker layers as desired for increased flexibility in controlling
the thermal and electrical characteristics of the fused heater element (108). A laser head
may move (or be steered via mirrors), the substrate (104) may be moved, or even both may
be moved to achieve a desired geometry and configuration for the fused heater element
(108).
An aspect (or example) of the present invention provide a process for producing a profiled
heating element in a single step on a substrate (104) using a laser metal deposition (LMD),
in which a powder is fed into a laser beam focused on the surface of a substrate (104). The
powder is fused to the substrate (104) by the localized laser energy in only the regions in
which the laser beam is focused. By applying a trace of the correct material to directly form
the heater element trace, a customized heater may be built upon the substrate (104) (such
as a ceramic material, an insulated substrate, etc.) in one direct writing step with no
requirements for either masking or selective removal of the deposited material. This
arrangement allows for the creating of a customized heater element with lower cost and
less steps than would otherwise be the case using known methods.
It is understood that the scope of the present invention is limited to the scope provided by
the independent claims, and it is also understood that the scope of the present invention is
not limited to: (i) the dependent claims, (ii) the detailed description of the non-limiting
embodiments, (iii) the summary, (iv) the abstract, and/or (v) description provided outside of
this document (that is, outside of the instant application as filed, as prosecuted, and/or as
granted). It is understood, for the purposes of this document, the phrase "includes (but is
not limited to)" is equivalent to the word "comprising". The word "comprising" is a transitional
phrase or word that links the preamble of a patent claim to the specific elements set forth in
the claim which define what the invention itself actually is. The transitional phrase acts as a
limitation on the claim, indicating whether a similar device, method, or composition infringes
the patent if the accused device (etc) contains more or fewer elements than the claim in the
patent. The word "comprising" is to be treated as an open transition, which is the broadest
form of transition, as it does not limit the preamble to whatever elements are identified in
the claim. It is noted that the foregoing has outlined the non-limiting embodiments. Thus,
although the description is made for particular non-limiting embodiments, the scope of the
present invention is suitable and applicable to other arrangements and applications.
Modifications to the non-limiting embodiments can be effected without departing from the
scope of the independent claims. It is understood that the non-limiting embodiments are
merely illustrative.

WHAT IS CLAIMED IS:
1. A process (200), comprising:
a transfer operation (204), including transferring a resistive powder (106) to an
electrically insulated element (102); and
a converting operating (206), including converting at least some of the
resistive powder (106) to a fused heater element (108) by using a laser metal
deposition apparatus (110), the fused heater element (108) being fused to the
electrically insulated element (102).
2. The process (200) of claim 1, further comprising:
a fixing operation (202), including fixing the electrically insulated element
(102) on a substrate (104).
3. The process (200) of claim 1, wherein:
the transfer operation (204) further includes:
using a feeder nozzle (112) to spray the resistive powder (106) on the
electrically insulated element (102).
4. The process (200) of claim 1, wherein:
the transfer operation (204) further includes:
depositing the resistive powder (106) as a layer on the electrically
insulated element (102).