U.S. patent application number 11/368946 was filed with the patent office on 2007-01-04 for apparatus for fabricating fiber reinforced plastic parts.
Invention is credited to Ernest C. Schroeder.
Application Number | 20070003650 11/368946 |
Document ID | / |
Family ID | 23038143 |
Filed Date | 2007-01-04 |
United States Patent
Application |
20070003650 |
Kind Code |
A1 |
Schroeder; Ernest C. |
January 4, 2007 |
Apparatus for fabricating fiber reinforced plastic parts
Abstract
The invention relates to an apparatus and method for fabricating
FRP parts. More specifically, the invention relates to a method for
forming FRP parts without the use of forms or molds. According to a
preferred embodiment of the present invention, the method for
fabricating an FRP part comprises the steps of: programming a
readable definition of a part into a machine, wherein the machine
moves an extrusion head mounted to the machine in a controlled
pattern; and wherein the machine regulates the speed of extrusion
from the extrusion head; feeding a fiber reinforcement to the
extrusion head of the machine; impregnating the fiber reinforcement
with a radiation-initiated resin; extruding the impregnated fiber
reinforcement from an orifice in the extrusion head; and exposing
the extruded fiber reinforcement to curing radiation.
Inventors: |
Schroeder; Ernest C.;
(Trappe, MD) |
Correspondence
Address: |
KELLEY DRYE & WARREN LLP
3050 K STREET, NW
SUITE 400
WASHINGTON
DC
20007
US
|
Family ID: |
23038143 |
Appl. No.: |
11/368946 |
Filed: |
September 11, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10084998 |
Mar 1, 2002 |
7029621 |
|
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11368946 |
Sep 11, 2006 |
|
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60272039 |
Mar 1, 2001 |
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Current U.S.
Class: |
425/71 |
Current CPC
Class: |
B29C 35/10 20130101;
B29C 48/05 20190201; B33Y 10/00 20141201; B29C 70/50 20130101; B29C
48/156 20190201 |
Class at
Publication: |
425/071 |
International
Class: |
B28B 5/00 20060101
B28B005/00 |
Claims
1. An apparatus for fabricating a fiber reinforced plastic part,
comprising: an extrusion head, wherein said extrusion head further
comprises an orifice; means for moving said extrusion head in a
controlled pattern; means for regulating the speed of extrusion
from said extrusion head; a resin impregnator; a supply of fiber
reinforcement, wherein said fiber reinforcement passes through said
impregnator and through said orifice of said extrusion head; a
supply of radiation-initiated resin for impregnating said fiber
reinforcement; means for feeding said fiber reinforcement to said
impregnator; means for impregnating said fiber reinforcement with
said resin; a radiation source; and a readable definition of said
part.
2. The apparatus according to claim 1, wherein said means for
moving said head in a controlled pattern comprises a computer
numerically controlled machine.
3. The apparatus according to claim 1, wherein said means for
moving said head in a controlled pattern comprises a mechanically
guided machine.
4. The apparatus according to claim 1, wherein said means for
regulating the speed of extrusion from said extrusion head
comprises a computer numerically controlled machine.
5. The apparatus according to claim 1, wherein said means for
regulating the speed of extrusion from said extrusion head
comprises a mechanically guided machine.
6. The apparatus according to claim 1, wherein said fiber
reinforcement comprises a yarn.
7. The apparatus according to claim 1, wherein said fiber
reinforcement comprises a ribbon.
8. The apparatus according to claim 1, wherein said fiber
reinforcement comprises a tube.
9. The apparatus according to claim 1, wherein said resin cures and
hardens with exposure to ultraviolet light.
10. The apparatus according to claim 1, wherein said radiation
source comprises ultraviolet light in a wavelength range between
about 380 and 400 nanometers.
11. The apparatus according to claim 9, wherein said radiation
source further comprises about 400 to 1000 watts of ultraviolet
light.
12. The apparatus according to claim 1, further comprising a lens
and mirror for directing said radiation source to said extruding
fibers reinforcement.
13. The apparatus according to claim 1, wherein said means for
feeding said fibers reinforcement to said extrusion head comprises
one or more of a supply roller, a tensioner, and a roller pair.
14. The apparatus according to claim 1, wherein said means for
impregnating said fiber reinforcement with said resin comprises a
resin supply line and a pump.
15. The apparatus according to claim 1, wherein said readable
definition of said part comprises a mechanical definition of said
part.
16. The apparatus according to claim 1, wherein said readable
definition of said part comprises a computer-generated definition
of said part.
17. The apparatus according to claim 1, further comprising means
for spraying said fabricated part with surfacing materials.
18. The apparatus according to claim 17, further comprising means
for cutting or abrading said sprayed part back to the final
dimensions of said readable definition of said part.
19. An apparatus for fabricating a fiber reinforced plastic part,
comprising: an extrusion head, wherein said extrusion head further
comprises an orifice; a computer numerically controlled machine to
which said extrusion head is mounted; a resin impregnator; a supply
of fiber reinforcement, wherein said fiber reinforcement passes
through said impregnator and through said orifice of said extrusion
head; a supply of resin for impregnating said fiber reinforcement;
means for feeding said fiber reinforcement to said extrusion head;
means for impregnating said fiber reinforcement with said resin; a
radiation source; and a readable definition of said part.
20. An apparatus for fabricating a fiber reinforced plastic part,
comprising: an extrusion head, wherein said extrusion head further
comprises an orifice; a mechanically guided machine to which said
extrusion head is mounted; a resin impregnator; a supply of fiber
reinforcement, wherein said fiber reinforcement passes through said
impregnator and through said orifice of said extrusion head; a
supply of resin for impregnating said fiber reinforcement; means
for feeding said fiber reinforcement to said extrusion head; means
for impregnating said fiber reinforcement with said resin; a
radiation source; and a readable definition of said part.
21. A method for fabricating an fiber reinforced plastic part,
comprising the steps of: programming a readable definition of a
part into a machine, wherein the machine moves an extrusion head
mounted to the machine in a controlled pattern; and wherein the
machine regulates the speed of extrusion from the extrusion head;
feeding the fiber reinforcement to the extrusion head of the
machine; impregnating the fiber reinforcement with a
radiation-initiated resin; extruding the impregnated fiber
reinforcement from an orifice in the extrusion head; and exposing
the extruded fiber reinforcement to curing radiation.
22. The method according to claim 21, wherein the step of extruding
the fiber reinforcement comprises extruding the impregnated fiber
reinforcement at a speed consistent to the speed of travel of the
extrusion head.
23. The method according to claim 21, wherein the step of extruding
the fiber reinforcement further comprises moving the extrusion head
with the machine along a path that defines the surface of the
part.
24. The method according to claim 21, wherein the step of extruding
the fiber reinforcement further comprises extruding a plurality of
points of attachment to a base or support structure at intervals
during the extrusion.
25. The method according to claim 21, wherein the step of exposing
the extruded fiber reinforcement to curing radiation further
comprises coordinating the rate of cure with the rate of travel of
the extrusion head and the rate of extrusion of the fiber
reinforcement, thereby maintaining the fiber reinforcement in
position at the point of extrusion.
26. The method according to claim 21, wherein the step of extruding
the fiber reinforcement further comprises the step of rotating the
extrusion head, which is mounted to an arm of the machine, and
free-forming the shape of extruding fiber reinforcement onto a
take-away belt.
27. The method according to claim 21, further comprising the steps
of: spraying the laminated part with surfacing materials; and
cutting or abrading the sprayed part back to the final dimensions
of the original definition of the part.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present invention relates to, and is entitled to the
benefit of the earlier filing date and priority of, U.S.
Provisional Application No. 60/272,039, filed on Mar. 1, 2001.
FIELD OF THE INVENTION
[0002] The invention relates to an apparatus and method for
fabricating fiber reinforced plastic parts. More specifically, the
invention relates to an apparatus and method for forming fiber
reinforced plastic ("FRP") parts without the need for forms or
molds.
BACKGROUND OF THE INVENTION
[0003] The use of fiber (primarily glass fiber) reinforced plastic
("FRP") parts is widespread in many industries, including
manufacturing, marine, aerospace, transportation, or any industry
demanding molded, durable high strength, parts. FRP is a standard
and understood name for fiberglass parts in the field of art and
includes reinforcement materials other than fiberglass. Typically
these parts must be made using expensive forms or molds. What is
needed in the industry is an apparatus and method for the
fabrication of FRP parts without the use of forms or molds.
[0004] There are previously known methods relating to the
construction and operation of computer controlled machine tools
("computer numerically controlled machines" or "CNC machines") for
metal working, painting, welding, woodworking and assembly. There
are previously known radiation-initiated resins used in making
prototype parts within a liquid bath ("rapid prototyping"). There
is also related art referring to the application of resin (some
radiation-initiated) impregnated yarns (tow) or ribbons of
reinforcements to rotating mandrels of given shapes to form parts
on those mandrels ("filament winding"). In addition, there are
applications where radiation-initiated resin impregnated
reinforcements are deposited on two- and three-dimensional mold
surfaces by CNC machines. This pultrusion process pulls an FRP
shape out of a die, and radiation-initiated resins are used to
allow for the bending of the shape as it emerges from the die.
Applicant is unaware of any work preceding that of the present
invention that describes an apparatus and method enabling the use
of a CNC machine to make FRP parts, without the use of forms or
molds in practically any size or shape, according to a preferred
embodiment of the present invention.
[0005] The apparatus and method according to a preferred embodiment
of the present invention represents a more economical process to
create these FRP parts. The following example provides some idea of
the value of the apparatus and method.
[0006] A boat hull requires the following steps to proceed from
drawing to finished product using processors according to the prior
art: 1) build forms to make a `plug` or mock up of the hull; 2)
fair up and smooth the plug to final dimension and finish (a CNC
machine is typically used for this step); 3) laminate a female mold
over the plug; and 4) laminate a complete hull in the mold.
[0007] Using current technology, the probable cost for a 45 foot
hull could easily exceed $500,000.00 and require 6 months to
complete depending upon the degree of accuracy and finish
desired.
[0008] The same hull created by the apparatus and method according
to a preferred embodiment of the present invention would require
the following steps: 1) operate the novel extrusion system of the
present invention for a period long enough to make the desired
shape; 2) smooth the surface; and 3) build up thickness on the
inside of the hull.
[0009] It is probable that this work could cost less than
$30,000.00 and require no more than 1 month to complete for a 45
foot boat hull, and the finished product could be reasonably
expected to be as, or more, geometrically exact than the product of
the prior art process. Additionally, the novel process according to
an embodiment of the present invention would provide more
consistently accurate results because of the elimination of steps
between the CNC machine work and the finished part.
[0010] There is no process known to exist that can create a large
FRP shape in space that is dimensionally accurate, and possesses
structural integrity. All of the materials used to make this FRP
laminate become a contributing functional part of the finished
structure and are compatible with materials used in secondary
operations to increase strength through build-up of thickness on
the inside of the structure or for attaching components.
OBJECTS OF THE INVENTION
[0011] It is an object of a preferred embodiment of the present
invention to provide a fast, cost-effective apparatus and method
for fabricating FRP parts directly from computer drawing data
without the need for costly molds or other intermediate forming
tools.
[0012] It is another of a preferred embodiment of the present
invention to provide a method for fabricating FRP parts that avoids
the costs of traditional molds, such as mold maintenance, mold
storage, and security.
[0013] It is another object of a preferred embodiment of the
present invention to provide an apparatus and method for developing
a FRP laminated shape that is self-supporting and inherently strong
without part-specific tooling.
[0014] It is another object of a preferred embodiment of the
present invention to provide an apparatus and method for
fabricating FRP laminated composite structures directly from
digital data.
[0015] Additional objects and advantages of the invention are set
forth, in part, in the description which follows and, in part, will
be apparent to one of ordinary skill in the art from the
description and/or from the practice of the invention.
SUMMARY OF THE INVENTION
[0016] In response to the foregoing challenge, applicants have
developed an apparatus for fabricating a fiber reinforced plastic
part (FRP), comprising: an extrusion head, wherein the extrusion
head further comprises an orifice through which resin impregnated
fiber reinforcement can be delivered in a speed regulated manner;
means for moving the head in a controlled pattern; means for
regulating the speed of extrusion from the extrusion head; a resin
impregnator; a supply of fiber reinforcement, wherein the fiber
reinforcement passes through the impregnator and through the
extrusion head; a supply of radiation-initiated resin for
impregnating the fiber reinforcement; means for feeding the fiber
reinforcement through the impregnation and through the extrusion
head; means for impregnating the fiber reinforcement with the
resin; a resin-curing radiation source; and a readable definition
of the part.
[0017] The resin impregnator may be part of the extrusion head or
located upstream of the fusion head on the path of the fiber
reinforcement. The means for moving the head in a controlled
pattern may comprise a computer numerically controlled machine, a
mechanically guided machine, or any other suitable device capable
of moving the head in a controlled pattern. The means for
regulating the speed of extrusion from the extrusion head may
comprise a computer numerically controlled machine, a mechanically
guided machine, or any other suitable device capable of regulating
the speed of extrusion from the extrusion head.
[0018] The fiber reinforcement may comprise a yarn (tow), ribbon,
tube, or any other suitable shape. The radiation-initiated resin
may cure (harden) with exposure to a resin-curing radiation source.
The radiation source may comprise any radiation at any wavelength
or energy level effective in curing the resin. The radiation source
may further comprise ultraviolet light in a wavelength range
between about 380 and 400 nanometers and at about 400 to 1000 watts
of ultraviolet light. The apparatus may further comprise means for
directing the radiation to the un-cured fiber reinforcement as it
exits the orifice of the extrusion head. The means for directing
the radiation may further comprise a lens and mirror for directing
the radiation source to the extruding fiber reinforcement.
[0019] The means for feeding the fiber reinforcement to the
extrusion head may comprise one or more of a supply roller, a
tensioner, and/or a roller pair located within the extrusion head,
or alternatively upstream along the reinforcement supply path. The
means for impregnating the fiber reinforcement with the resin may
comprise a resin supply line leading to the impregnator and a pump,
or any other suitable means for impregnating the fiber
reinforcement. The readable definition of the part may comprise a
mechanical definition of the part, or alternatively a
computer-generated definition of the part.
[0020] The apparatus may further comprise means for spraying the
fabricated part with surfacing materials. The apparatus may further
comprise means for cutting or abrading the part back to the final
dimensions of the original readable definition of the part.
[0021] According to an alternative embodiment of the present
invention, the apparatus for fabricating a fiber reinforced plastic
part comprises: an extrusion head, wherein said extrusion head
further comprises an orifice; a computer numerically controlled
machine to which said extrusion head is mounted; a resin
impregnator; a supply of fiber reinforcement, wherein said fiber
reinforcement passes through said impregnator and through said
extrusion head; a supply of radiation-initiated resin for
impregnating said fiber reinforcement; means for feeding said fiber
reinforcement to said extrusion head; means for impregnating the
fiber reinforcement with the resin; a resin-curing radiation
source; and a readable definition of said part.
[0022] Another alternative embodiment of the apparatus for
fabricating a fiber reinforced plastic part comprises: an extrusion
head, wherein the extrusion head further comprises an orifice; a
mechanically guided machine to which the extrusion head is mounted;
a resin impregnator; a supply of fiber reinforcement, wherein the
fiber reinforcement passes through the impregnator and through the
orifice of the extrusion head; a supply of radiation-initiated
resin for impregnating the fiber reinforcement; means for feeding
the fiber reinforcement to the extrusion head; means for feeding
the resin to the impregnator; a resin-curing radiation source; and
a readable definition of the part.
[0023] Applicants have also developed an innovative, economical
method to extrude a shape of fiber reinforcement, which is
impregnated with a radiation-initiated resin, and to cause the
radiation-initiated resin impregnated fiber reinforcement to cure
nearly instantly in place by means of exposure to radiated energy,
which may be a focused beam of light or any other suitable curing
radiation. According to a preferred embodiment, the method for
fabricating a fiber reinforced plastic part comprises the steps of.
programming a readable definition of a part into a machine, wherein
the machine moves an extrusion head mounted to the machine in a
controlled pattern; and wherein the machine regulates the speed of
extrusion from the extrusion head; feeding a fiber reinforcement to
the extrusion head of the machine; impregnating the fiber
reinforcement with the resin; extruding the impregnated fiber
reinforcement from an orifice in the extrusion head; exposing the
extruded fiber reinforcement to curing radiation; and, if
necessary, repeating the passes of the extrusion head to develop a
fiber reinforced plastic part.
[0024] The step of extruding the fiber reinforcement may comprise
extruding the impregnated fiber reinforcement at a speed consistent
to the speed of travel of the extrusion head. The step of extruding
the fiber reinforcement may further comprise moving the extrusion
head with the machine along a path that defines the surface of the
part. The step of extruding the fiber reinforcement may further
comprise extruding a plurality of points of attachment to a base or
support structure at intervals during the extrusion.
[0025] The step of exposing the extruded fiber reinforcement to
curing radiation may further comprise coordinating the rate of cure
with the rate of travel of the extrusion head and the rate of
extrusion of the fiber reinforcement, thereby maintaining the fiber
reinforcement in position at the point of extrusion. The step of
extruding the fiber reinforcement may further comprise the step of
rotating the extrusion head, which is mounted to an arm of the
machine, and free-forming the shape of extruding fiber
reinforcement onto a take-away belt.
[0026] The method may further comprise the steps of: spraying the
laminated part with surfacing materials; and cutting or abrading
the sprayed part back to the final dimensions of the original
definition of the part.
[0027] It is to be understood that both the foregoing general
description and the following detailed description are exemplary
and explanatory only, and are not restrictive of the invention as
claimed. The accompanying drawings, which are incorporated herein
by reference, and which constitute a part of this specification,
illustrate certain embodiments of the invention and together with
the detailed description serve to explain the principles of the
present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] In order to assist the understanding of this invention,
reference will now be made to the appended drawings, in which like
reference numerals refer to like elements. The drawings are
exemplary only, and should not be construed as limiting the
invention.
[0029] FIG. 1a is a schematic view of an extrusion head of the
apparatus for fabricating fiber reinforced plastic parts according
to a preferred embodiment of the present invention;
[0030] FIG. 1b is a schematic view of an extrusion head of the
apparatus for fabricating fiber reinforced plastic parts according
to an alternative embodiment of the present invention;
[0031] FIGS. 2a-2d are illustrations of various extruded cross
sections of an FRP structure combined by successive passes of the
means for moving the head in a controlled pattern and the means for
regulating the speed of extrusion from the extrusion head according
to preferred embodiments of the present invention;
[0032] FIG. 3 is a flowchart depicting the method according to a
preferred embodiment of the present invention for fabricating FRP
parts;
[0033] FIG. 4 is a flowchart depicting a process according to the
prior art; and
[0034] FIG. 5 is a flowchart according to an alternative embodiment
of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Apparatus of the Present Invention
[0035] Reference will now be made in detail to a preferred
embodiment of the present invention. The apparatus for fabricating
fiber reinforced plastic parts comprises: an extrusion head,
wherein the extrusion head further comprises an orifice; means for
moving the head in a controlled pattern; means for regulating the
speed of extrusion from the extrusion head; a resin impregnator; a
supply of fiber reinforcement, wherein the fiber reinforcement
passes through the impregnator and through the extrusion head; a
supply of resin for impregnating the fiber reinforcement; means for
feeding the fiber reinforcement to the extrusion head; means for
impregnating the fiber reinforcement with the resin; a resin-curing
radiation source; and a readable definition of the part.
[0036] A preferred embodiment of the apparatus 10 is shown in FIG.
1a. According to the preferred embodiment, an extrusion head 100
has an orifice 110 located therein through which resin impregnated
fiber reinforcement can be delivered in a speed regulated manner.
The apparatus 10 preferably includes means for moving the head in a
controlled pattern and means for regulating the speed of extrusion
from the extrusion head. The means for moving the head in a
controlled pattern and the means for regulating the speed of
extrusion preferably comprise a CNC machine. The CNC machine
preferably is of a size and with sufficient number of axis of
movement to form the part. The extrusion head may be mounted to the
CNC machine. Although the preferred embodiment discusses a CNC
machine, any other suitable machine or mechanism may be used.
[0037] According to the preferred embodiment, the rate at which the
extruding fiber reinforcement issues from the head 100 matches the
rate at which the head 100 moves through space. If the head 100
moves faster than the rate of extrusion, the extruded reinforcement
may be stretched out of position and the final structure may be
distorted. If the head 100 moves slower, the extruded reinforcement
may be bunched, causing distortion.
[0038] The apparatus 100 preferably further includes a resin
impregnator 120. A supply of fiber reinforcement 200 preferably is
further included, wherein the fiber reinforcement 200 passes
through the impregnator 120 and through the orifice 110 of the
extrusion head 100. The fiber reinforcement 200 may comprise
various shapes, such as, but not limited to, a yarn, ribbon, or
tube. Several possible cross sections in combination of the fiber
reinforcement are depicted in FIGS. 2a-2d. The resin impregnator
120 may comprise a chamber within the extrusion head 100.
Alternatively, the resin impregnator 120 may be located upstream on
the supply path of the fiber reinforcement 200.
[0039] The apparatus preferably includes a supply of resin for
impregnating the fiber reinforcement 200. The resin used to
impregnate the reinforcement 200 may be a commercially available
polymer to which has been added a radiation-initiator causing the
resin to cure with exposure to curing radiation, such as but not
limited to ultraviolet ("UV") light.
[0040] According to the preferred embodiment, the apparatus 10
further comprises, means for feeding the fiber reinforcement to the
extrusion head and means for impregnating the fiber reinforcement
with a resin. The fiber reinforcement 200 preferably is fed through
the resin impregnator 120 and out through the orifice 110 of the
extrusion head 100. As shown in FIG. 1a, the means for feeding the
fiber reinforcement to the extrusion head 300 may comprise one or
more of a supply roller 310 and/or a tensioner 320. These
components may be located anywhere between the extrusion head 100
and the source of the fiber reinforcement. The means for feeding
the fiber reinforcement to the extrusion head 300 may further
include a roller pair 330, which may be located within the
extrusion head 100. The roller pair may seal the resin impregnator
while controlling the rate of feed of the fiber reinforcement as
the pressure within impregnator 120 forces the fiber reinforcement
out through the orifice 110. The fiber reinforcement 200 may be fed
by the supply roller 310 through the tensioner 320 and into the
head 100 where it may be fed between the roller pair 330, through
the resin impregnator 120, and to the orifice 110 of the extrusion
head 100. Alternatively, as shown in FIG. 1b, a roller group may be
located within the impregnator and the tensioner may be located
anywhere between the impregnator and the orifice of the extrusion
head. The means for impregnating the fiber reinforcement with the
resin may comprise a resin supply line, such as for example a
supply tube, which leads from the resin supply source to the
impregnator 120 of the extrusion head 100, and a pump or any other
suitable means to supply resin to impregnator 120.
[0041] It will be apparent to persons of ordinary skill in the art
that various modifications and variations could be made to the
means for feeding the fiber reinforcement through the machine. It
may comprise any suitable mechanism for advancing the fiber
reinforcement through the required components. Thus it is intended
that the present invention cover all the variations and
modifications of various machines that could be employed, provided
they come within the scope of the present invention as claimed in
the appended claims and their equivalents.
[0042] The radiation source 400 preferably is of sufficient
intensity and wave-length to cause the extruded material to cure
upon emergence from the extrusion head 100. The radiation may
comprise UV light in a wavelength range of from about 380 to 400
nm. It may further comprise an intense source of about 400 to 1000
watts of UV light at such wavelengths. The radiation may shine from
a source directly onto the emerging fiber reinforcement.
Alternatively, the apparatus 10 may further comprise means for
directing the radiation to the un-cured fiber reinforcement 200 as
it exits the orifice 110 of the extrusion head 100. The means for
directing the radiation may include a lens 410 and/or a mirror 420,
as depicted in FIG. 1a, which concentrate and direct the radiation
to the extruding fiber reinforcement for curing the reinforcement
200. The means for directing the radiation may comprise other
devices, such as, but not limited to, magnets, wave-guides, or any
other suitable device capable of concentrating and directing the
radiation.
[0043] In a preferred embodiment, a readable definition of the part
to be fabricated is programmed into the CNC machine, to and is used
by the machine to direct the extrusion of the impregnated fiber
reinforcement. The readable definition of the part may comprise a a
computer-generated definition of the part, or alternatively a
mechanical definition of the part. Software and technology needed
for programming the design into the machine is well within the
ability of one of ordinary skill in the art. It is standard
practice to use commercially available CAD (Computer Assisted
Design) and CAM (Computer Assisted Manufacturing) software.
[0044] In an alternative embodiment of the present invention,
commonly available software and materials may also be included so
that the same machine that controls the extrusion head may be used
to spray the structure with surfacing materials by means of
mounting a standard spray gun to the CNC machine and controlling
its path while applying a given thickness of commercially available
surfacing putty or paint to the FRP part. After the surfacing
material has been applied and allowed to cure, the spray gun may be
replaced by a router or sanding head and the surfacing material may
be removed in a controlled manner to a depth to yield a smooth
accurate surface representing the original surface as defined in
the readable definition of the part, such as computer data.
[0045] Any CNC machine designed for cutting will have the necessary
rigidity to accomplish this cutting work efficiently. If, however,
the CNC machine will only be applying the impregnated fiber
reinforcement, then the CNC machine can be of less rigid
construction because the application of the impregnated fiber
reinforcement does not result in back pressure against the CNC
machine. Lightly built CNC machines currently available for other
processes that do not result in back pressure would include welding
and spray painting robots, for example. More rigidly built CNC
machines currently available for other processes that do result in
back pressure would include metal cutting milling machines and
woodworking CNC routers. It is conceivable that a hand-held device
could be developed that would allow the fabrication of
non-dimensionally critical structures if the speed of travel of the
head could be determined and linked to control the rate of
extrusion. This development would allow for physical structures to
be "drawn" in three-dimensional space.
[0046] It will be apparent to persons of ordinary skill in the art
that various modifications and variations could be made to the
apparatus of the present invention without departing from the scope
or spirit of the invention. For example, the means for moving the
head in a controlled pattern and the means for regulating the speed
of extrusion of the fiber reinforcement that are employed in the
present invention could be modified. Rather than a CNC machine,
each may comprise a numerically controlled machine, a direct
numerically controlled machine, a mechanically guided machine, or
any other suitable device that is capable of performing such
functions. In an application for repetitive small parts the head
may be moved by a mechanism that follows a template, thereby
eliminating the need for a CNC machine. In addition, the curing
radiation could be any radiation type, known or unknown, for
example, but not limited to, light such as used with
photo-initiator resins. Thus it is intended that the present
invention cover all the variations and modifications of various
machines that could be employed, provided they come within the
scope of the present invention as claimed in the appended claims
and their equivalents.
Method of the Present Invention
[0047] Reference will now be made in detail to the method of a
preferred embodiment of the present invention. According to a
preferred embodiment, as depicted in FIG. 3, the method for
fabricating a fiber reinforced plastic part comprises the steps of:
programming a definition of a part into a machine, wherein the
machine moves an extrusion head mounted to the machine in a
controlled pattern and wherein the machine regulates the speed of
extrusion from the extrusion head; feeding fiber reinforcement to
an extrusion head of the machine; impregnating the fiber
reinforcement with a radiation-initiated resin; extruding the fiber
reinforcement from an orifice in the extrusion head; exposing the
extruded fiber reinforcement to curing radiation; and, if
necessary, repeating the passes of the extrusion head to develop a
fiber reinforced plastic part.
[0048] A machine readable design of the FRP part to be fabricated
preferably is developed and programmed into the machine, as shown
in step 100. One of ordinary skill in the art would be familiar
with suitable software and technology for use in the machine,
preferably a CNC machine. In step 200, fiber reinforcement
preferably is delivered to the extrusion head of the machine by the
means for feeding the reinforcement to the extrusion head. The
fiber reinforcement preferably is fed through a resin impregnator
and out through the orifice in the extrusion head. The fiber
reinforcement may be fed by one or more of a supply roller, through
one or more of a tensioner, and into the extrusion head, where it
may be fed by one or more of a roller pair within the head into the
resin impregnator.
[0049] In step 300, the fiber reinforcement is impregnated by a
radiation-initiated resin. The resin preferably is fed through a
resin supply to the resin impregnator where it impregnates the
fiber reinforcement as it is fed through the impregnator. In a
preferred embodiment depicted in FIG. 1a, a strand, ribbon, tube,
rod, or any other suitable shape of fiber reinforcement is fed into
the impregnator in the extrusion head by means of a roller pair.
Within the impregnator, the fiber reinforcement preferably is
impregnated by the resin, which is delivered to the impregnator by
a pump, or any other suitable means of delivery.
[0050] As shown in step 400, the impregnated fiber reinforcement
preferably is extruded through the orifice of the extrusion head.
It may be forced from the head by the resin pressure and the force
of the roller pair. In a preferred embodiment, the machine moves
the extrusion head in a defined path in space, which causes the
extruded reinforcement to form the final shape, as called for by
the readable definition of the part. The extrusion head preferably
is moved along a path that defines the surface of the part to be
formed. Software and technology for this kind of control is common
and accessible from the industry and would be known by one of
ordinary skill in the art. The extrusion head preferably extrudes
impregnated fiber reinforcement at a speed consistent to the speed
of travel of the machine that carries it.
[0051] The rate of travel of the head and the rate of extrusion of
the fiber reinforcement preferably are coordinated with the rate of
cure of the resin, step 500, so that the material remains in
position at the point of extrusion, supported only by its own
rigidity and by the previously extruded material adjacent to it
(the fiber reinforcement laid down in the previous pass). It is
preferable that no loads are placed on existing extruded structure
as distortion could result.
[0052] In an alternative embodiment, the part being formed may have
a plurality of points of attachment to a pre-existing base plate or
support structure, as required, which may be extruded at intervals
during the process.
[0053] In another alternative embodiment, the step of extruding the
fiber reinforcement may include a rotating extrusion head, which is
mounted to an arm of a CNC machine, and free-forming the shape of
extruding fiber reinforcement onto a take-away belt.
[0054] In step 500, curing radiation, preferably UV light, hardens
successive passes of the extruded material in space as it is
extruded. The resulting material preferably forms a shell or
structure in the desired shape and of the desired thickness. The
surface finish of the completed part will be as smooth as the size
of the extruded ribbon or strand used to make it will allow. For
example, a part made from 1/8 inch diameter material may have a
rougher surface than a part made from 1/16 inch diameter material.
The "macro" dimensions of a part made by this method, however, will
be as accurate as the precision built into the controlling machine
and readable definition of the part. All of the materials used to
fabricate the FRP part preferably are compatible with materials
used in secondary operations to increase strength through build-up
of thickness on the inside of the structure or for attaching
components.
[0055] The ability to extrude a variety of shapes, as depicted in
FIGS. 2a-2d, allows large simple shapes, such as boat hulls, to be
made with flat ribbons to save time, whereas intricate shapes may
require small rods with diameters of a fraction of an inch, as in
FIG. 2a, to achieve the necessary level of detail. It is also
possible to extrude cruciform or channel shapes, as shown in FIG.
2c, in which the projecting rib adds stiffness to the structure.
Alternatively, a multi-level structure that is bonded by supporting
members may be made to create very high strength-to-weight ratios,
as depicted in FIG. 2d. Applications of preferred embodiments of
the present invention include: prototype fabrication of any large
FRP structure (such as boat hulls, airplane parts, automotive
components, tanks, and ducting); scenery and full-size sets for
film, display and entertainment applications; and onsite
fabrication of structures, including housing structures, by means
of purpose built application equipment, such as, for example a
truck mounted CNC machine arm.
[0056] It may be found practicable and efficient to build a "wire
frame"-type structure with rapid cure materials using the method of
the present invention, and then apply traditional chemical cure
layers to build up thickness and strength. Typical tolerances for
large CNC machine cut foam shapes are +/-0.060'' for aerospace
applications and +/-0.250'' for marine applications. CNC machine
produced parts are about this accurate over the full size of the
part. To get this accuracy by hand is possible, but not probable or
cost effective. In most applications, the tolerances required on
large FRP structures can be much less stringent. Tolerance may
become critical in applications where two large parts have to fit
together. For example two halves of a large aircraft fuel tank. If
the producing CNC machine is not large enough to make the whole
part in one piece, or if transportation restrictions demand a
multi-section structure, then a high degree of accuracy becomes
critical.
[0057] In addition, it may be cost effective to fabricate any size
of finished production FRP parts in quantity without tooling in
many different applications, especially where surface finish is not
critical and/or shape changes need to be accommodated on short
notice. The present invention avoids the costs of traditional
molds, such as mold maintenance, mold storage, and security. For
example, if molds are destroyed, the only recourse is to start from
scratch and replace them. With this method, the readable
definitions of the parts can be duplicated and securely stored. It
also enables users to make parts at more than one location that are
exactly the same dimensions.
[0058] It will be apparent to those skilled in the art that various
modifications and variations can be made in the construction,
configuration, and/or operation of the present invention without
departing from the scope or spirit of the invention. For example,
in the embodiments mentioned above, various changes may be made to
the resin, curing method, or machine parts without departing from
the scope and spirit of the invention. Further, it may be
appropriate to make additional modifications or changes to the
resin delivery method without departing from the scope of the
invention. Thus, it is intended that the present invention cover
the modifications and variations of the invention provided they
come within the scope of the appended claims and their
equivalent
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