U.S. patent application number 10/816171 was filed with the patent office on 2005-09-22 for unknown.
This patent application is currently assigned to Toyota Motorsport GmbH. Invention is credited to Hesse, Peter, Paul, Tillmann, Weiss, Richard.
Application Number | 20050207931 10/816171 |
Document ID | / |
Family ID | 34986489 |
Filed Date | 2005-09-22 |
United States Patent
Application |
20050207931 |
Kind Code |
A1 |
Hesse, Peter ; et
al. |
September 22, 2005 |
unknown
Abstract
The invention describes powders for use in the production of
spatial structures, i.e. molded bodies, using layer build-up
methods, as well as methods for their efficient production. The
powders have the special feature that they have good flow behavior,
for one thing, and at the same time, have such a composition that
the molded body that can be produced with the powder, using rapid
prototyping, has significantly improved mechanical and/or thermal
properties. According to a particularly advantageous embodiment,
the powder has a first component that is present in the form of
essentially spherical powder particles, which is formed by a matrix
material, and at least one further component in the form of
stiffening and/or reinforcing fibers, which are preferably embedded
in the matrix material.
Inventors: |
Hesse, Peter; (Koeln,
DE) ; Paul, Tillmann; (Koeln, DE) ; Weiss,
Richard; (Koeln, DE) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
Toyota Motorsport GmbH
Koeln
DE
|
Family ID: |
34986489 |
Appl. No.: |
10/816171 |
Filed: |
April 2, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10816171 |
Apr 2, 2004 |
|
|
|
PCT/EP04/02965 |
Mar 22, 2004 |
|
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Current U.S.
Class: |
419/10 |
Current CPC
Class: |
B22F 9/026 20130101;
B22F 2998/00 20130101; B33Y 70/00 20141201; B22F 1/0096 20130101;
B29C 64/153 20170801; C22C 47/14 20130101; B29K 2071/00 20130101;
B33Y 80/00 20141201; B22F 1/0048 20130101; B22F 2999/00 20130101;
Y02P 10/25 20151101; B33Y 40/00 20141201; C22C 1/1042 20130101;
Y10T 428/2982 20150115; B29K 2105/12 20130101; B22F 2998/00
20130101; B22F 10/10 20210101; B22F 2999/00 20130101; B22F 1/0096
20130101; B22F 1/004 20130101; B22F 9/026 20130101; B22F 2998/00
20130101; B22F 10/20 20210101; B22F 2998/00 20130101; B22F 10/10
20210101 |
Class at
Publication: |
419/010 |
International
Class: |
B22F 003/10 |
Claims
1-30. (canceled)
31. A powder comprising essentially spherical particles of an
aromatic polyether ketone plastic.
32. The powder of claim 31, wherein the aromatic polyether ketone
plastic is a polyaryl ether ketone plastic comprising polymerized
units of oxy-1,4-phenylene-oxy-1,4-phenylene-carbonyl-1,4-phenylene
of formula (I) 3
33. The powder of claim 31, wherein the particles are
spherical.
34. The power according to claim 1, further comprising one or more
of a stiffening fiber or a reinforcing fiber, and a matrix material
in the form of essentially spherical powder particles.
35. The powder according to claim 34, wherein the total amount of
the stiffening fibers and reinforcing fibers is up to 25% by
volume.
36. The powder according to claim 34, wherein the total amount of
the stiffening fibers and reinforcing fibers is up to 15% by
volume.
37. The powder of claim 34, wherein the total amount of the
stiffening fibers and reinforcing fibers is up to 10% by
volume.
38. The powder according to claim 34, wherein the fibers are
embedded in the aromatic polyether ketone plastic.
39. The powder according to claim 34, wherein the fibers are
essentially completely surrounded by the aromatic polyether ketone
plastic.
40. The powder according to claim 34, wherein the reinforcing
fibers and stiffening fibers are completely surrounded by the
aromatic polyether ketone plastic.
41. The powder according to claim 38, wherein the reinforcing
fibers and stiffening fibers are present in a volume proportion of
greater than 15%.
42. The powder according to claim 38, wherein the stiffening fibers
and reinforcing fibers are present in a volume proportion of
greater than 25%.
43. The powder according to claim 34, wherein the matrix material
comprises a thermoplastic material.
44. The powder according to claim 43, wherein the matrix material
comprises a crosslinked polyamide.
45. The powder according to claim 44, wherein the crosslinked
polyamide is at least one selected from the group consisting of
PA11 and PA12.
46. The powder according to claim 43, wherein at least one of the
stiffening fibers or reinforcing fibers comprises at least one of
carbon or glass fibers.
47. The powder according to claim 31, wherein the spherical
particles have an average grain sized d.sub.50 of from 20 to 150
.mu.m.
48. The powder according to claim 31, wherein the spherical powder
particles have an average grain size d.sub.50 of from 40 to 70
.mu.m.
49. The powder according to claim 34, wherein the matrix material
comprises a metallic material.
50. The powder according to claim 51, wherein the fibers are
selected from the group consisting of ceramic fibers and boron
fibers.
51. The powder according to claim 49, wherein the spherical powder
particles have an average grain size d.sub.50 in the range of 10 to
100 .mu.m.
52. The powder according to claim 49, wherein the spherical powder
particles have an average grain size d.sub.50 of from 10 to 80
.mu.m.
53. The powder according to claim 34, wherein the average length
L50 of the fibers is no greater than the average grain size
d.sub.50 of the spherical powder particles.
54. A powder comprising a first component in the form of
essentially spherical powder particles and at least one of a
stiffening fiber or a reinforcing fiber, wherein the first
component comprises a matrix material.
55. The powder according to claim 54, wherein the total amount of
the stiffening fibers and reinforcing fibers is up to 25% by
volume.
56. The powder according to claim 54, wherein the total amount of
the stiffening fibers and reinforcing fibers is up to 15% by
volume.
57. The powder of claim 54, wherein the total amount of the
stiffening fibers and reinforcing fibers is up to 10% by
volume.
58. The powder according to claim 54, wherein the fibers are
embedded in the aromatic polyether ketone plastic.
59. The powder according to claim 54, wherein the fibers are
essentially completely surrounded by the aromatic polyether ketone
plastic.
60. The powder according to claim 54, wherein the reinforcing
fibers and stiffening fibers are completely surrounded by the
aromatic polyether ketone plastic.
61. The powder according to claim 58, wherein the reinforcing
fibers and stiffening fibers are present in a volume proportion of
greater than 15%.
62. The powder according to claim 58, wherein the stiffening fibers
and reinforcing fibers are present in a volume proportion of
greater than 25%.
63. The powder according to claim 54, wherein the matrix material
comprises a thermoplastic material.
64. The powder according to claim 63, wherein the thermoplastic
material comprises a crosslinked polyamide.
65. The powder according to claim 64, wherein the crosslinked
polyamide is at least one selected from the group consisting of
PA11 and PA12.
66. The powder according to claim 63, wherein at least one of the
stiffening fibers or reinforcing fibers comprises at least one of
carbon or glass fibers.
67. The powder according to claim 54, wherein the spherical
particles have an average grain sized d.sub.50 of from 20 to 150
.mu.m.
68. The powder according to claim 54, wherein the spherical powder
particles have an average grain size d.sub.50 of from 40 to 70
.mu.m.
69. The powder according to claim 54, wherein the matrix material
comprises a metallic material.
70. The powder according to claim 69, wherein the fibers are
selected from the group consisting of ceramic fibers and boron
fibers
71. The powder according to claim 69, wherein the spherical powder
particles have an average grain size d.sub.50 in the range of 10 to
100 .mu.m.
72. The powder according to claim 69, wherein the spherical powder
particles have an average grain size d.sub.50 of from 10 to 80
.mu.m.
73. A method for the production of a powder comprising essentially
spherical particles of an aromatic polyether ketone plastic,
comprising: mixing a matrix micropowder into a liquid phase to form
a suspension wherein the particle size of the matrix micropowder is
less than the particle size of the powder; spraying the suspension
through a nozzle to form droplets comprising the matrix
micropowder; and vaporizing or evaporating a liquid component from
the droplets to form the powder in the form of essentially
spherical agglomerates.
74. The method according to claim 73, wherein the liquid phase is
further mixed with at least one of a reinforcing fiber or a
stiffening fiber having a length less than the particle size of the
powder.
75. The method according to claim 73, wherein the matrix
micropowder has an average grain size d.sub.50 between 3 and 10
.mu.m.
76. The method according to claim 73, wherein the matrix
micropowder has an average grain size d.sub.50 of 5 .mu.m.
77. The method of claim 74, wherein the fibers have an average
length L50 of 20 to 150 .mu.m.
78. The method according to claim 74, wherein the fibers have an
average length L50 of 40 to 70 .mu.m.
79. The method according to claim 74, wherein the matrix
micropowder has an average grain size d.sub.50 between 3 and 10
.mu.m and the fibers have an average length L50 of 10 to 100
.mu.m.
80. The method according to claim 74, wherein the matrix
micropowder has an average grain size d.sub.50 of 5 .mu.m and the
fibers have an average length L50 of 10 to 80 .mu.m.
81. The method according to claim 73, wherein the droplets have an
average diameter d.sub.50 of 10 to 70 .mu.m.
82. The method according to claim 73, wherein the vaporizing or
evaporating is carried out while the droplets are moving through a
heating segment.
83. A method for the production of a powder comprising a first
component in the form of essentially spherical powder particle and
at least one of a stiffening fiber or a reinforcing fiber, wherein
the first component comprises a matrix material, and the fibers are
embedded in the powder particles, comprising: mixing a matrix
micropowder with a liquid phase to form a suspension wherein the
particle size of the matrix micropowder is less than the particle
size of the powder; spraying the suspension through a nozzle to
form droplets comprising the matrix micropowder; and vaporizing or
evaporating a liquid component from the droplets to form the powder
in the form of essentially spherical agglomerates.
84. The method according to claim 83, wherein the liquid phase is
further mixed with at least one of a reinforcing fiber or a
stiffening fiber having a length less than the particle size of the
powder.
85. The method according to claim 83, wherein the matrix
micropowder has an average grain size d.sub.50 between 3 and 10
.mu.m.
86. The method according to claim 83, wherein the matrix
micropowder has an average grain size d.sub.50 of 5 .mu.m.
87. The method of claim 83, wherein the fibers have an average
length L50 of 20 to 150 .mu.m.
88. The method according to claim 83, wherein the fibers have an
average length L50 of 40 to 70 .mu.m.
89. The method according to claim 84, wherein the matrix
micropowder has an average grain size d.sub.50 between 3 and 10
.mu.m and the fibers have an average length L50 of 10 to 100
.mu.m.
90. The method according to claim 84, wherein the matrix
micropowder has an average grain size d.sub.50 of 5 .mu.m and the
fibers have an average length L.sub.50 of 10 to 80 .mu.m.
91. The method according to claim 83, wherein the droplets have an
average diameter d.sub.50 of 10 to 70 .mu.m.
92. The method according to claim 83, wherein the vaporizing or
evaporating is carried out while the droplets are moving through a
heating segment.
93. A method for the production of a powder comprising essentially
spherical particles of an aromatic polyether ketone plastic,
comprising: cooling a coarse granulate comprising a plastic matrix
material to form brittle, coarse granulates; grinding the brittle,
coarse granulates; and separating the ground granulate into a
fraction spectrum.
94. The method according to claim 93, wherein the coarse granulate
is a fiber-reinforced plastic matrix material.
95. The method according to claim 93, wherein the grinding is
carried out with a pinned disk mill.
96. The method according to claim 93, wherein the grinding is
carried out with cooling.
97. The method according to claim 93, wherein the separating is
carried out with an air separator.
98. The method according to claim 93, further comprising: smoothing
the ground granulate.
99. The method according to claim 98, wherein the smoothing is
carried out by embedding or accumulating at least one of
microparticles or nanoparticles.
100. A method for producing a powder comprising a first component
in the form of essentially spherical powder particles and at least
one of a stiffening fiber or a reinforcing fiber, wherein the first
component comprises a matrix material, comprising: cooling a coarse
granulate comprising a plastic matrix material to form brittle,
coarse granulates; grinding the brittle, coarse granulates; and
separating the ground granulate into a fraction spectrum.
101. The method according to claim 100, wherein the coarse
granulate is a fiber-reinforced plastic matrix material.
102. The method according to claim 100, wherein the grinding is
carried out with a pinned disk mill.
103. The method according to claim 100, wherein the grinding is
carried out with cooling.
104. The method according to claim 100, wherein the separating is
carried out with an air separator.
105. The method according to claim 100, further comprising:
smoothing the ground granulate.
106. The method according to claim 105, wherein the smoothing is
carried out by embedding or accumulating at least one of
microparticles or nanoparticles.
107. A method for producing a powder comprising essentially
spherical particles of an aromatic polyether ketone plastic,
comprising: melting a matrix material; blowing the melted matrix
material through a nozzle to form droplets; and passing the
droplets through a cooling segment.
108. The method according to claim 107, further comprising:
stirring at least one of stiffening fibers or reinforcing fibers
into the melted matrix material before blowing the melted matrix
material.
109. The method according to claim 107, wherein the droplets are
formed in a hot gas jet.
110. The method according to claim 107, further comprising:
separating the cooled droplets into a fraction spectrum.
111. A method for producing a powder comprising a first component
in the form of essentially spherical powder particles and at least
one of a stiffening fiber or a reinforcing fiber, wherein the first
component comprises a matrix material, comprising: melting a matrix
material; blowing the melted matrix material through a nozzle to
form droplets; and passing the droplets through a cooling
segment.
112. The method according to claim 111, further comprising:
stirring at least of stiffening or reinforcing fibers into the
melted matrix material before blowing the melted matrix
material.
113. The method according to claim 111, wherein the droplets are
formed in a hot gas jet.
114. The method according to claim 111, further comprising:
separating the cooled droplets into a fraction spectrum.
115. A method for producing a spatial structure, comprising:
melting the powder according to claim 31.
116. The method according to claim 115, wherein melting includes
powder-based generative rapid prototyping, selective laser
sintering or laser melting.
117. A method for producing a spatial structure, comprising:
melting the powder according to claim 34.
118. The method according to claim 117, wherein melting includes
powder-based generative rapid prototyping, selective laser
sintering or laser melting.
119. A molded body obtained by powder-based generative rapid
prototyping of the powder according to claim 31.
120. The molded body of claim 119, wherein the powder-based
generative rapid prototyping is selective laser sintering or laser
melting.
121. A molded body obtained by powder-based generative rapid
prototyping of the powder according to claim 34.
122. The molded body of claim 121, wherein the powder-based
generative rapid prototyping is selective laser sintering or laser
melting.
123. The molded body according to claim 119, comprising one or more
interior reinforcements.
124. The molded body according to claim 119, comprising a
three-dimensional framework reinforcement.
125. The molded body according to claim 121, comprising one or more
interior reinforcements.
126. The molded body according to claim 121, comprising a
three-dimensional framework reinforcement.
127. A molded body obtained by powder-based generative rapid
prototyping of the powder according to claim 54.
128. The molded body of claim 127, wherein the powder-based
generative rapid prototyping is selective laser sintering or laser
melting.
129. The molded body according to claim 128, comprising one or more
interior reinforcements.
Description
BACKGROUND OF THE INVENTION
[0001] Field of the Invention
[0002] The invention relates, in general, to the production of
spatial, particularly spatially complex structures, i.e. molded
bodies, by means of layer build-up methods, as they are also known
under the term "powder-based generative rapid prototyping" or
"solid free form fabrication" (SFF) methods. Such powder-based
generative rapid prototyping methods are known, for example, under
the designations 3 D laser sintering, 3 D laser melting, or 3 D
printing.
[0003] The invention particularly relates to a powder for use in
such a method, as well as to methods for the efficient production
of such a powder.
[0004] Methods for the production of molded bodies having a complex
structure, which are generally computer-controlled, additive,
automatic methods, work with bulk of powdered materials, which are
heated in layers, at certain points or in certain regions, to such
an extent that a melting or sintering process occurs. For heating,
a laser beam, preferably a program-controlled laser beam or, when
using metallic powder materials, a high-energy electron beam is
used.
[0005] In the meantime, various powders have been developed for
this technology, whereby reference can be made, in this regard,
particularly to the documents DE 101 22 492 A1, EP 0 968 080 B1, WO
03/106146 A1, or DE 197 47 309 A1, for the sector of plastic
powders, or to WO 02/11928, for the sector of metallic powders.
[0006] In order to be able to conduct the shaping process without
problems, at a high process stability, powder particles that are
characterized by particularly good "flow behavior" during
application of the powder layer are required, and this is assured
in that the powder particles are configured to be as spherical as
possible, with the smoothest possible surface.
[0007] Until now, polyamide, particularly a highly cross-linked
polyamide, such as PA 11 or PA 12, has particularly proven itself
as a material for the method described initially.
[0008] However, with this powder material, the spectrum of use of
the molded bodies produced with it is limited. Therefore, various
attempts have already been made to modify the powders, in order to
improve the mechanical properties of the molded body. One approach
was seen in mixing the thermoplastic powder with glass beads or
aluminum flakes.
[0009] It is true that a good flow capacity is maintained with the
glass beads, but the improvements in mechanical properties that can
be achieved are limited. It is true that stiffening of the material
is possible (increase in the modulus of elasticity), but it was not
possible to significantly increase the tensile strength, and the
improvements that could be achieved were obtained at the expense of
the material becoming brittle. This problem is even more marked
when using aluminum flakes.
[0010] The invention is therefore based on the task of improving
the method for the production of molded bodies by means of
selective sintering or melting of powdered materials, in such a
manner that while maintaining the fundamental design of the
machine, molded bodies having significantly improved mechanical
properties can be produced.
[0011] This task is accomplished by means of a new powder according
to claims 1 and 2, as well as by means of a method for the
production of such powders, according to claims 14, 15, 20, and/or
25.
[0012] According to a first aspect of the invention (claim 1), the
essentially spherical powder particles are formed by an aromatic
polyether ketone plastic, particularly a polyaryl ether ketone
(PEEK) plastic, having the repetition unit
oxy-1,4-phenylene-oxy-1,4-phenylene-c- arbonyl-1,4-phenylene
according to the following formula: 1
[0013] This linear, aromatic polymer, which is marketed by the
Victrex company under the name "PEEK," is generally
semi-crystalline and is characterized by physical properties that
are far superior to the materials used in SLS methods until now, in
every regard. Not only the mechanical properties, such as tensile
strength and modulus of elasticity, are many times better than in
the case of conventional PA powders. In addition, the thermal
stability of this material is so good that the components produced
from this material according to the SLS method can even be used
where until now, even fiber-reinforced plastics were not up to the
job.
[0014] The inventors have recognized that this material can be
processed to form powder particles that are smooth and spherical,
to the greatest possible extent, using a suitable method,
particularly by means of the methods of claims 14, 20, and/or 25,
which particles thereby guarantee a sufficiently good flow capacity
of the powder, so that the individual layers can be applied with
the greatest possible precision.
[0015] According to a second aspect of the invention, a powder is
made available, having a first component present in the form of
essentially spherical powder particles that is formed by a matrix
material, and having at least a further component in the form of
stiffening and/or reinforcing fibers. In this connection, the
matrix material can be a plastic or a metal. Studies have shown
that if the volume proportion of the fibers, depending on the fiber
length distribution, remains limited, for example to a maximum of
25%, preferably to up to 15%, particularly preferably up to 10%,
the flow capacity of the powder can be controlled well. The
experimental results show that using PA12 as the matrix material,
triple the stiffness and a 50% increase in tensile strength can be
achieved with as little as 10 vol.-% fiber proportion (carbon
fibers).
[0016] To further improve the mechanical properties, the fiber
proportion should be increased. According to the invention, the
powder with the highest volume proportion of fiber is produced
using the production methods according to claims 14, 15, 20, and/or
25, whereby it is possible to embed the fibers into the matrix
material, preferably in such a manner that they are essentially
completely surrounded by the matrix material. In this manner, the
handling of the powder remains essentially uninfluenced by the
volume proportion of the fiber material. Using PA12 as the matrix
material and using a volume proportion of the carbon fibers of 30%,
an increase in tensile strength of 300% and an increased in the
modulus of elasticity by a factor of 9 can be achieved, depending
on.
[0017] If a thermoplastic plastic is used as the matrix material,
significant improvements in the mechanical properties as compared
with the non-reinforced material can be achieved even if flakes are
used instead of fibers, as long as their dimensions permit
preferably complete embedding into the powder particles. This
aspect is explicitly included in the object of the invention.
[0018] If the matrix material is formed by a plastic material, the
fibers are preferably selected from the group of carbon and/or
glass fibers.
[0019] Fundamentally, the powder can be produced in all the grades
that have been processed until now, whereby the powder particles
can have an average diameter d50 in the range of 20 to 150,
preferably from 40 to 70 .mu.m. The spread of the grain size
distribution should be as narrow as possible, so that the flow
capacity is not impaired too greatly.
[0020] The matrix material can, of course, also be formed by a
metallic material. This does not fundamentally change anything with
regard to the production methods of the powder particles having
embedded fibers, according to claims 15, 20, and/or 25.
[0021] A metallic matrix material is preferably combined with
fibers from the group of ceramic fibers and boron fibers.
[0022] In this case, it is advantageous if the average grain size
d50 of the spherical powder particles lies between 10 and 100,
preferably between 10 and 80 .mu.m. The value of d50 refers to that
dimension of the grain size that is exceeded by 50% of the powder
particles, and 50% of the powder particles lie below it.
[0023] The fiber length distribution is selected in such a manner
that as low a percentage of the fibers as possible projects out of
the surface of the particles that are formed during melt-spraying
or spray-drying. This can be achieved, for example, in that the
average length L50 of the fibers corresponds to maximally the value
of the average grain size d50 of the spherical powder
particles.
[0024] A first advantageous method for the production of a powder,
particularly according to one of claims 1 to 13, is the object of
claim 14. Using this method, it is possible to produce essentially
spherical powder particles, as a function of the process
parameters, which can be changed; it is true that these particles
are composed of a plurality of smaller particles, but they have a
sufficiently spherical and smooth surface so that they can be used
in rapid prototyping methods, without problems.
[0025] This method can be carried out, equally advantageously, in
the presence of a second phase in the form of a stiffening or
reinforcing fiber. All liquids that permit a uniform distribution
of the micropowder particles and, optionally, of the reinforcing
phase, can be used as the liquid phase of the suspension. Another
relevant aspect in the selection of the liquid is the property that
it vaporizes or evaporates quickly and without leaving a
residue.
[0026] Preferably, in this method, if the matrix material has been
selected from the group of thermoplastics, micropowder having an
average grain size d50 between 3 and 10 .mu.m, preferably 5 .mu.m
and, optionally, fibers, preferably having an average length L50 of
20 to 150 .mu.m, preferably 40 to 70 .mu.m, are used. The value L50
designates the length that is exceeded by 50% of the fibers, and
50% of the fibers lie below this value.
[0027] Claim 17 indicates advantageous dimensions of the particles
for metal as the matrix material.
[0028] An alternative method for the production of the powder
according to the invention is the object of claim 20. It is mainly
of interest for thermoplastic materials, but can fundamentally be
used also for metallic materials. In this connection, the step of
cooling is absolutely necessary for thermoplastic materials, so
that the material is made brittle to such an extent that it can be
ground. Advantageously, the cooling takes place by means of liquid
nitrogen. Other advantageous embodiments of this method are the
object of claims 22 to 24.
[0029] A third alternative of the production method is so-called
melt-spraying according to claim 25, which can also be used for
metallic and thermoplastic materials. Important process parameters
for adjusting the desired grain size distribution are: temperature
of the melt; viscosity and surface tension of the melt; die
diameter; speed, volume flow, pressure, and temperature of the gas
stream.
[0030] Preferably, atomization of the melt takes place in a hot gas
jet.
[0031] Using the powder according to the invention, which can be
produced using a method according to the invention, it is possible
to clearly expand the area of application of components or molded
parts that have been generated by means of layer build-up methods
(powder-based generative rapid prototyping), such as according to
SLS (selective laser sintering) or laser melting technology. Using
the invention, it is therefore possible, for the first time, to use
such a layer build-up method, in practical manner, for the
production of hollow molded bodies having interior reinforcements,
preferably three-dimensional framework-like reinforcements. This is
because until now, the mechanical properties of the material were
so low that even with reinforcing structures, it was not possible
to use the material in areas that were under thermal and/or
mechanical stress.
[0032] In the following, the invention will be explained in greater
detail, using exemplary embodiments:
[0033] The drawing shows:
[0034] FIG. 1 a fundamental diagram to show the functional
principle of the layer build-up method;
[0035] FIG. 2 the detail II in FIG. 1;
[0036] FIG. 3 a schematic representation of a method for the
production of the powder according to a first embodiment;
[0037] FIG. 4 a schematic view of a powder according to a further
embodiment of the invention;
[0038] FIG. 5 a schematic view of a powder according to a further
variant of the invention;
[0039] FIG. 6 a schematic representation of a method for the
production of the powder according to FIG. 5, corresponding to one
embodiment;
[0040] FIG. 7 a schematic representation of another method for the
production of the powder according to FIG. 5;
[0041] FIG. 8 a schematic view of a cut-out of a component that can
be produced using the powder according to the invention; and
[0042] FIG. 8A the detail VIII in FIG. 8.
[0043] FIG. 1 schematically shows how a component is produced by
means of layer build-up methods. It can be seen that successive
powder layers 12-1, 12-2, . . . 12-n having a thickness S are being
applied to a platform 10 that can be lowered into a construction
space, step by step. After a layer has been applied, the particles
18 (see FIG. 2) are selectively melted in targeted areas,
completely or in part, by an energy beam from an energy source 16,
whereby the regions 14 indicated with cross-hatching in the figure
are formed, which thereby become an integral part of the component
being produced. The platform is subsequently lowered by the layer
thickness S, whereupon a new powder layer having the layer
thickness S is applied. The energy beam passes over a predetermined
area once again, whereby the corresponding regions are melted and
melded, i.e. joined with the regions in the previous layer that
were melted. In this manner, a multi-layer powder block having an
embedded molded body of a complex structure is gradually formed.
The molded body is removed from the powder block and generally the
residual powder that adheres to it or is sintered to it is cleaned
away manually.
[0044] The layer thickness is selected to be between 20 and 300
.mu.m, depending on the area of application, whereby the majority
of the powder particles 18 have a grain size D of approximately
{fraction (1/3)} of the layer thickness S, as can be seen in FIG.
2.
[0045] Conventionally, the powder is formed by a thermoplastic, for
example PA 11 or PA 12, whereby the mechanical strength of the
molded bodies remains limited, due to the low modulus of elasticity
in the range of 1.4 GPa, and the low tensile strength in the range
of 40 to 50 MPa.
[0046] The invention gives different approaches for the production
of molded bodies having significantly improved mechanical
properties, which will be explained in greater detail in the
following:
EMBODIMENT 1
[0047] The powder has a first matrix component that is present in
the form of essentially spherical powder particles (18), which is
formed by an aromatic polyether ketone plastic, particularly a
polyaryl ether ketone (PEEK) plastic, having the repetition unit
oxy-1,4-phenylene-oxy-1,4-phen- ylene-carbonyl-1,4-phenylene of the
general formula 2
[0048] Such a material can be purchased, for example, under the
trade name "PEEK," from the company Victrex Plc. The material
properties lie at a tensile strength of more than 90 MPa and a
modulus of elasticity in the range of more than 3.5 GPa (according
to ISO 527). In addition, this material is characterized by an
extremely good temperature stability, so that the molded parts
built from it can be used even in areas that are subject to great
thermal stress.
[0049] The production of powder particles from this material
preferably takes place according to one of the following
methods:
[0050] 1. Spray-drying,
[0051] 2. Grinding; and
[0052] 3. Melt-spraying.
[0053] Spray-Drying:
[0054] For this purpose, as can be seen in FIG. 3, a suspension is
first produced, having a matrix micropowder 22 stirred into a
liquid phase, such as ethanol or an ethanol/water mixture 20. The
particles of the matrix micropowder 20 have dimensions that lie
significantly below the particle size DP of the powder particle 30
to be produced. In this connection, uniform mixing of the phases in
the vessel must be assured.
[0055] The suspension is sprayed through a nozzle, not shown in
detail, whereby droplets 32 containing matrix micropowder are
formed. The liquid phase 26, specifically the surface tension of
this phase, guarantees an essentially spherical shape of the
droplets.
[0056] Subsequently, for example in a subsequent heating segment,
the liquid component 26 of the droplets 32 is vaporized and/or
evaporated, leaving essentially spherical agglomerates 30 behind.
These agglomerates 30 form the powder particles to be used in the
subsequent layer build-up method. Accordingly, the process
parameters of the method are selected in such a manner that the
particles are produced in the desired grain size distribution.
[0057] Grinding:
[0058] An alternative method consists in that the material, which
can be purchased, for example, as a coarse granulate having a grain
size of approximately 3 mm, is ground to produce a suitable
micropowder.
[0059] In this process, the coarse granulate is first cooled to a
temperature that lies below the temperature at which the material
becomes brittle. Cooling takes place, for example, by means of
liquid nitrogen. In this state, the coarse granulate can be ground
in a pinned disk mill, for example. The ground powder is finally
separated, preferably in an air separator, to obtain a
predetermined fraction spectrum.
[0060] The method step of grinding can take place with additional
cooling.
[0061] In order for the ground powder to get a sufficiently smooth
and preferably spherical surface, it is advantageous to subject the
ground material to smoothing treatment, for example by embedding or
accumulation of microparticles and/or nanoparticles, such as
Aerosil.
[0062] Melt-Spraying:
[0063] A third method variant of the production of micropowder made
of aromatic polyether ketone, particularly a polyaryl ether ketone,
consists in that a melt-spraying method is used.
[0064] In this process, the material is melted in a crucible that
has a connection to a spray nozzle with which the material is
atomized.
[0065] In this process, small droplets leave the nozzle. Because of
the surface tension of the material, these droplets assume an
essentially spherical shape. If the droplets are subsequently moved
through a cooling segment, they solidify in this spherical shape,
so that powder is present in the grade desired for the layer
build-up method.
[0066] Preferably, hot gas is used for the atomization. The hot gas
that is used for spraying, i.e. for atomization of the melted
material, is produced by means of a so-called pebble heater.
[0067] As a rule, a separating step follows the method step of
spraying, in order to obtain powder particles in accordance with a
predetermined fraction spectrum.
EMBODIMENT 2
[0068] As shown schematically in FIG. 4, powder having a first
component present in the form of essentially spherical powder
particles 118, which is formed by a matrix material, and at least
one further component in the form of stiffening and/or reinforcing
fibers 140. The matrix component can be formed by a metal or by a
thermoplastic plastic.
[0069] The following experimental example was carried out:
[0070] PA12 powder having a grain size distribution with d50 at
about 50 .mu.m was mixed with 10 vol.-% carbon fibers of two
different types, having an average fiber length L50 of about 70
.mu.m and a fiber thickness of 7 .mu.m. It was possible to process
the powder obtained in this way on commercially available rapid
prototyping machines, to produce defect-free molded bodies.
[0071] It was possible to significantly improve the mechanical
properties of the sample body produced on the basis of this
powder/fiber mixture, according to the layer build-up method, as
compared with a component that did not contain any fibers.
Specifically, it was possible to increase the modulus of elasticity
to more than 3.8 GPa and the tensile strength to approximately 70
MPa.
[0072] These experimental results were compared with results
obtained with components that were obtained by means of
injection-molding of PA12 mixed with fibers, whereby the fibers
that were added to the injection-molding mass were present in the
same volume concentration and the same size distribution. The
measured results show that the mechanical properties of the
components obtained according to the layer build-up method are not
inferior, in any regard, to those of the injection-molded parts. In
fact, it was actually possible to increase the modulus of
elasticity in the case of the sintered body.
[0073] Although the proportion of fibers in the micropowder can be
varied, depending on the average grain size and its distribution,
it generally cannot be raised above 25% without causing problems.
In order to nevertheless be able to achieve improved material
properties, the third embodiment of the invention is offered.
EMBODIMENT 3
[0074] According to the third embodiment, which is illustrated
schematically in FIG. 3, a powder is created that contains
significantly higher proportions of fiber, namely above 30 vol.-%,
but nevertheless has such a composition that it can be used in a
layer build-up method, because of its good flow capacity.
[0075] The particular feature is that the fibers 240 are embedded
in essentially spherical powder molded bodies 218, which form the
matrix material of the component to be produced, preferably in such
a manner that they are essentially completely surrounded by the
matrix material, as shown in FIG. 5.
[0076] For the production of such a powder, the methods described
above, i.e. spray-drying, grinding, and melt-spraying, can be used
with slight modifications:
[0077] Spray-Drying:
[0078] This method is shown schematically in FIG. 6. It differs
from the method described above, on the basis of FIG. 3, only in
that not only matrix micropowder 322 but also stiffening or
reinforcing fibers 340 are stirred into the liquid phase, such as
an ethanol or an ethanol/water mixture 320. The particles of the
matrix micropowder 20 have dimensions that lie significantly below
the particle size DP of the powder particle 30 to be produced. The
fiber lengths are also selected in such a manner that their average
length is not greater than the average grain size of the powder
particles to be achieved. In this connection, again, uniform mixing
of the phases in the vessel must be assured.
[0079] When spraying the suspension through a nozzle, not shown in
detail, droplets 332 that contain matrix micropowder and fiber(s)
form. The liquid phase 326, specifically the surface tension of
this phase, guarantees an essentially spherical shape of the
droplets.
[0080] If, subsequently, the volatile component 326 of the droplets
332 is vaporized and/or evaporated, again, essentially spherical
agglomerates 330 remain behind. These agglomerates 330 form the
powder particles to be used in the subsequent layer build-up
method. Accordingly, the process parameters are selected in such a
manner that the particles are produced in the desired grain size
distribution.
[0081] Good results can be achieved with the spray-drying if
micropowders having an average grain size d50 between 3 and 10
.mu.m, preferably 6 .mu.m, are used.
[0082] If fibers are stirred in, they should preferably be used at
an average length L50 from 20 to 150 .mu.m, preferably 40 to 70
.mu.m.
[0083] In the case of a metallic matrix material, the lengths of
the fibers should generally be selected to be shorter. An
advantageous range for the average fiber length L50 lies between 10
and 100 .mu.m, preferably between 10 and 80 .mu.m.
[0084] It is advantageous to adjust the process parameters in such
a manner that essentially spherical microdroplets having an average
diameter D50 of 10 to 70 .mu.m are formed.
[0085] The vaporization and/or evaporation step is advantageously
carried out while the droplets are being moved through a heating
segment.
[0086] Grinding:
[0087] An alternative method, which is shown schematically in FIG.
7, consists in that a material containing fibers, for example
carbon fibers 440, which material is present, for example, as a
coarse granulate 450 having a grain size or edge length of about 3
mm, is ground to produce a suitable micropowder.
[0088] In this process, the coarse granulate 450 is again cooled to
a temperature that lies below the temperature at which the material
becomes brittle. Cooling takes place, for example, by means of
liquid nitrogen. In this state, the coarse granulate can be ground,
for example; in a pinned disk mill, indicated as 460. The ground
powder is finally separated in a separator 480, preferably in an
air separator, in accordance with a predetermined fraction spectrum
that is to be achieved. The powder particles to be used are
indicated as 430.
[0089] In this connection, the method step of grinding can again
take place with additional cooling. Also, an optional smoothing
process, by means of embedding or accumulation of microparticles
and/or nanoparticles, such as Aerosil, can follow.
[0090] Melt-Spraying:
[0091] The third method embodiment described above, namely
so-called melt-spraying, can also be used for the production of
powder according to FIG. 5.
[0092] In contrast to the method described above, the fiber
component is stirred into the melted melt of the matrix
material.
[0093] The embodiments described above allow the processing of both
thermoplastic plastic materials and metallic materials.
[0094] Different materials can also be mixed.
[0095] If the matrix material is formed by a thermoplastic plastic
material, the fibers are selected from the group of carbon and/or
glass fibers.
[0096] The average grain size of the spherical powder particles is
fundamentally not supposed to be restricted. Good results with
commercially available machines can certainly be achieved if the
average grain size d50 of the spherical powder particles lies in
the range of 20 to 150, preferably 40 to 70 .mu.m. The flow
capacity of such a powder can be further increased by
homogenization of the size distribution.
[0097] If the matrix material is formed by a metallic material, the
fibers are preferably selected from the group of ceramic fibers and
boron fibers. In the case of such a powder, the average grain size
d50 of the spherical powder particles generally lies at a low
value, for example in the range of 10 and 100, preferably 10 to 80
.mu.m.
[0098] From the description, it becomes evident that using the
powder according to the invention, by using layer build-up methods
(powder-based generative rapid prototyping method), such as
according to SLS (selective laser sintering) or laser melting
technology, it is possible to produce spatial structures, i.e.
molded bodies, whose mechanical and/or thermal properties were
previously unthinkable.
[0099] Thus, the modulus of elasticity of PEEK, if it is reinforced
with 10, 20, or 30 vol.-% carbon fibers, which are introduced into
the powder particles or mixed with them, according to one of the
methods described, can be increased to 7, 13.5, and 22.2 GPa,
respectively, while it was possible to raise the tensile strength
to 136, 177, and 226 MPa, respectively.
[0100] If PA12 is used as the matrix material, an improvement of
the mechanical properties occurs as follows, with a fiber
proportion of 10, 20, and 30 vol.-%: modulus of elasticity 3.4,
6.6, and 13.9 GPa, respectively; tensile strength 66, 105, and 128
MPa, respectively.
[0101] In this way, it is possible, for the first time, as
indicated schematically in FIGS. 8, 8A, to use the layer build-up
method for the production of hollow molded bodies 570, having a
complex shape, for example multiple curvatures, with interior
reinforcements, preferably three-dimensional framework-like
reinforcements 572, in practical manner, making it possible to
produce components that are not only extremely light, but also can
withstand great thermal and mechanical stress.
[0102] Of course, deviations from the embodiments described above
are possible, without leaving the basic idea of the invention.
Thus, subsequent treatment steps of the individual powder
production methods can also be used for different methods. The
smoothing process to be carried out by means of microbodies can, of
course, also be used for the two methods described as
alternatives.
[0103] The invention therefore creates new powders for use in the
production of spatial structures, i.e. molded bodies, using layer
build-up methods, as well as methods for their efficient
production. The powders have the special feature that they have
good flow behavior, for one thing and, at the same time, have such
a composition that the molded body that can be produced with the
powder, using rapid prototyping, has significantly improved
mechanical and/or thermal properties. According to a particularly
advantageous embodiment, the powder has a first component that is
present in the form of essentially spherical powder particles,
which is formed by a matrix material, and at least one further
component in the form of stiffening and/or reinforcing fibers,
which are preferably embedded in the matrix material.
* * * * *