U.S. patent application number 13/763172 was filed with the patent office on 2013-10-24 for safety protection method and apparatus for additive manufacturing device.
This patent application is currently assigned to ARCAM AB. The applicant listed for this patent is ARCAM AB. Invention is credited to Lars Loewgren.
Application Number | 20130278920 13/763172 |
Document ID | / |
Family ID | 49290324 |
Filed Date | 2013-10-24 |
United States Patent
Application |
20130278920 |
Kind Code |
A1 |
Loewgren; Lars |
October 24, 2013 |
SAFETY PROTECTION METHOD AND APPARATUS FOR ADDITIVE MANUFACTURING
DEVICE
Abstract
A method for providing safety protection in an additive
manufacturing apparatus for forming a three-dimensional article
through successive fusion of parts of a powder bed in an enclosable
chamber, which parts corresponds to successive cross sections of
the three-dimensional article is provided. The method comprising
the steps of providing a position detecting device connected to a
control unit to detect whether a foreign matter is within the
enclosable chamber. The method may also include, upon detecting
that the foreign matter is within the enclosable chamber, either
(1) switching off, via the control unit, at least one device
associated with the additive manufacturing apparatus; or (2)
providing power to a powder suction device. Associated safety
protection devices are also provided.
Inventors: |
Loewgren; Lars;
(Haellingsjoe, SE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ARCAM AB |
Moelndal |
|
SE |
|
|
Assignee: |
ARCAM AB
Moelndal
SE
|
Family ID: |
49290324 |
Appl. No.: |
13/763172 |
Filed: |
February 8, 2013 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
PCT/EP2012/057470 |
Apr 24, 2012 |
|
|
|
13763172 |
|
|
|
|
Current U.S.
Class: |
356/51 ;
356/614 |
Current CPC
Class: |
B22F 2003/1056 20130101;
Y02P 10/25 20151101; B22F 3/1055 20130101; G01B 11/14 20130101;
Y02P 10/295 20151101; Y02P 10/20 20151101; Y02P 10/24 20151101;
B22F 2003/1059 20130101; B33Y 40/00 20141201 |
Class at
Publication: |
356/51 ;
356/614 |
International
Class: |
G01B 11/14 20060101
G01B011/14 |
Claims
1. A method for providing safety protection during formation of a
three-dimensional article through successive fusion of parts of a
powder bed in an enclosable chamber, which parts corresponds to
successive cross sections of the three-dimensional article, said
method comprising the steps of: providing a position detecting
device connected to a control unit of an additive manufacturing
apparatus configured for forming said three-dimensional article,
said position detecting device being configured to detect a
position location of a foreign matter within said enclosable
chamber; and upon detecting said position location of said foreign
matter is within said enclosable chamber, switching off, via said
control unit, at least one device associated with said additive
manufacturing apparatus.
2. The method according to claim 1, further comprising the step of,
upon detecting that said foreign matter is within said enclosable
chamber, providing power to a powder suction device.
3. The method according to claim 1, wherein said position detecting
device is an electromagnetic radiation curtain provided at an
opening of said enclosable chamber, said electromagnetic curtain
comprising at least one electromagnetic radiation source and at
least one electromagnetic radiation sensor, each of the at least
one electromagnetic radiation sensors being configured to receive
an emission from a corresponding one of said at least one
electromagnetic radiation sensors so as to define said
electromagnetic curtain.
4. The method according to claim 1, wherein said position detecting
device is at least one of a measurement arm and a robot arm capable
of registering the position in space.
5. The method according to claim 4, wherein: said method further
comprises the step of providing a hose from said powder suction
device to said robot arm; and said step of switching off said at
least one device associated with said additive manufacturing
apparatus occurs when said hose enters said enclosable chamber.
6. The method according to claim 1, wherein said enclosable chamber
is a vacuum chamber.
7. The method according to claim 1, wherein said foreign matter is
a nozzle of said powder suction device.
8. The method according to claim 2, further comprising the step of,
upon providing power to said powder suction device, switching on
said powder suction device by pressing a mechanical switch.
9. The method according to claim 1, wherein said electromagnetic
radiation source is at least one of a laser source, an infra-red
source, and a visible light source.
10. The method according to claim 1, wherein said device associated
with said additive manufacturing apparatus is at least one of an
electron beam, a laser beam, a powder distributor, a vacuum pump, a
gas supply, and a work table.
11. The method according to claim 1, wherein said powder suction
device is an external unit in relation to the enclosable
chamber.
12. A method for providing safety protection during formation of in
a three-dimensional article through successive fusion of parts of a
powder bed in an enclosable chamber, which parts corresponds to
successive cross sections of the three-dimensional article, said
method comprising the steps of: providing a position detecting
device connected to a control unit of an additive manufacturing
apparatus configured for forming said three-dimensional article,
said position detecting device being configured to detect a
position location of a foreign matter is within said enclosable
chamber; and upon detecting said position location of said foreign
matter is within said enclosable chamber, providing power to a
powder suction device.
13. The method according to claim 12, further comprising the step
of, upon detecting that said foreign matter is within said
enclosable chamber, switching off, via said control unit, at least
one device associated with said additive manufacturing
apparatus.
14. A safety protection device for forming a three-dimensional
article through successive fusion of parts of a powder bed in an
enclosable chamber, which parts corresponds to successive cross
sections of the three-dimensional article, said safety device
comprising: a position detecting device connected to a control unit
of an additive manufacturing apparatus configured for forming said
three-dimensional article, said position detecting device being
configured to detect a position location of a foreign matter within
said enclosable chamber; and a switch for switching off at least
one device associated with said additive manufacturing apparatus,
said switch being controlled by said control unit and being
activated when said position detecting device detects said position
location of said foreign matter within said enclosable chamber.
15. The safety protection device according to claim 14, wherein
said control unit is configured to provide power to a powder
suction device only when said position detecting device detects
that said foreign matter is within said enclosable chamber.
16. The safety protection device according to claim 14, wherein
said position detecting device is an electromagnetic radiation
curtain provided at an opening of said enclosable chamber, said
electromagnetic curtain comprising at least one electromagnetic
radiation source and at least one electromagnetic radiation
sensor.
17. The safety protection device according to claim 16, wherein:
each of said at least one electromagnetic radiation sensors are
positioned adjacent and spaced apart relative to one another along
substantially an entirety of a first side of said opening; each of
said at least one electromagnetic radiation sensors are positioned
adjacent and spaced apart relative to one another along
substantially an entirety of a second side of said opening, said
second side being opposite said first side relative to said
opening; and each of said at least one electromagnetic radiation
sensors are configured, based at least in part upon their relative
positioning, to receive an emission from a corresponding one of
each of said at least one electromagnetic radiation sources, said
transmission and receipt of said emission defining said
electromagnetic radiation curtain across at opening.
18. The safety protection device according to claim 14, wherein
said enclosable chamber is a vacuum chamber.
19. The safety protection device according to claim 14, wherein:
said position detecting device is at least one of a measurement arm
and a robot arm, at least a portion of said measuring arm and robot
arm being configured to register the position thereof in space; and
said foreign matter is a nozzle of said powder suction device
operatively fixed relative to said robot arm.
20. The safety protection device according to claim 14, wherein
said electromagnetic radiation source is at least one of a laser
source, an infra-red source, and a visible light source.
21. The safety protection device according to claim 14, wherein
said device associated with said additive manufacturing apparatus
is at least one of an electron beam, a laser beam, a powder
distributor, a vacuum pump, a gas supply, and a work table.
22. A safety protection device for forming a three-dimensional
article through successive fusion of parts of a powder bed in an
enclosable chamber, which parts corresponds to successive cross
sections of the three-dimensional article, said safety device
comprising: a control unit of an additive manufacturing apparatus
configured for forming said three-dimensional article, said
position detecting device being configured to detect a position
location of a foreign matter is within said enclosable chamber; and
a powder suction device configured such that said control unit only
provides power to said powder suction device when said position
detecting device detects said position location of said foreign
matter within said enclosable chamber.
23. The safety protection device according to claim 22, further
comprising a switch for switching off at least one device
associated with said additive manufacturing apparatus, said switch
being controlled by said control unit and being activated when said
position detecting device detects that said foreign matter is
within said enclosable chamber.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of and claims priority to
and the benefit of International Application No. PCT/EP2012/057470,
filed Apr. 24, 2012, the contents of which are hereby incorporated
by reference in its entirety.
BACKGROUND
[0002] 1. Field of the Invention
[0003] Various embodiments of the present invention relate to a
method and apparatus for providing safety protection in an additive
manufacturing device.
[0004] 1. Description of Related Art
[0005] Freeform fabrication or additive manufacturing is a method
for forming three-dimensional articles through successive fusion of
chosen parts of powder layers applied to a worktable.
[0006] An additive manufacturing apparatus may comprise a work
table on which said three-dimensional article is to be formed, a
powder dispenser, arranged to lay down a thin layer of powder on
the work table for the formation of a powder bed, an energy beam
for delivering energy to the powder whereby fusion of the powder
takes place, elements for control of the energy given off by the
energy beam over said powder bed for the formation of a cross
section of said three-dimensional article through fusion of parts
of said powder bed, and a controlling computer, in which
information is stored concerning consecutive cross sections of the
three-dimensional article. A three-dimensional article is formed
through consecutive fusions of consecutively formed cross sections
of powder layers, successively laid down by the powder
dispenser.
[0007] An additive manufacturing apparatus comprises inter alia a
beam source, a powder distributor and other mechanically moving
parts which, if not securely switched off, may be harmful to an
operator or service personnel. One way of making sure that the
machine is safe to work with is to manually switch off the power
supply to the additive manufacturing device. A problem with a
completely dead device is that even the non-harmful devices are not
working which may be annoying and/or problematic in some
situations. Another problem is that the power switch may be
forgotten to be switched off.
[0008] Additive manufacturing may also require a safe powder
handling and a safe recirculation of unused powder material,
meaning that only certain types of powder suction devices are
allowed to be used which do not expose the powder of any kind of
igniting means. Safe powder handling may also incorporate the
insurance that the recirculated powder is clean from any foreign
impurities which may destroy the performance of the manufactured
three dimensional article, which in turn may cause a safety problem
where the final article end up. Recirculated powder may be
non-solidified or non-fused powder material from a previous process
which is reused in a latter process. Said recirculated powder may
be blended with virgin powder.
BRIEF SUMMARY
[0009] Having this background, an object of the invention is to
provide methods and apparatuses for safety protection in an
additive manufacturing apparatus which will reduce or eliminate the
safety issues mentioned above.
[0010] According to various embodiments, a method is provided for
providing safety protection in an additive manufacturing apparatus
for forming a three-dimensional article through successive fusion
of parts of a powder bed in an enclosable chamber, which parts
corresponds to successive cross sections of the three-dimensional
article. The method comprises the steps of providing a position
detecting device connected to a control unit, said position
detecting device being configured to detect whether a foreign
matter is within said enclosable chamber; and upon detecting that
said foreign matter is within said enclosable chamber, switching
off, via said control unit, at least one device associated with
said additive manufacturing apparatus.
[0011] At least one advantage of at least these embodiments is that
harmful devices such as the beam source and powder distributor may
be automatically switched off when trying to enter the enclosable
chamber with for instance any foreign matter or foreign item such
as any part of the body or a tool.
[0012] Foreign matter or foreign item means anything that is
inserted from outside of the enclosable chamber to the inside of
the enclosable chamber.
[0013] Position detecting device means a device which is capable of
detecting if said foreign matter is inside or outside said
enclosable chamber.
[0014] The at least one device belonging to said additive
manufacturing device which is switched off may be a mechanical
movable part, a power source, a light emitting source, a laser
source, en electron beam source, i.e., any device belonging to the
additive manufacturing device which could harmful to a human being
if in operation.
[0015] According to various embodiments, another method is provided
for providing safety protection in an additive manufacturing
apparatus for forming a three-dimensional article through
successive fusion of parts of a powder bed in an enclosable
chamber, which parts corresponds to successive cross sections of
the three-dimensional article. The method comprises the steps of
providing a position detecting device connected to a control unit,
said position detecting device being configured to detect whether a
foreign matter is within said enclosable chamber; and upon
detecting that said foreign matter is within said enclosable
chamber, providing power to a powder suction device.
[0016] At least one advantage of this embodiment is that it reduces
the risk that a certified powder suction device is used for
cleaning other areas than the enclosable chamber from reusable
powder.
[0017] This implies that in the event of powder spill on for
instance the floor, said powder spill may not be collected by the
same powder suction device as the one which is intended for
collecting powder inside the enclosable chamber. This means that
clean powder may only be collected from one place by a first
suction device for further use. Dirty powder from other areas than
the enclosable chamber, which is not to be mixed with the clean
powder, is to be collected by other means for instance a second
powder suction device.
[0018] The inventive methods, in this regard, not only
automatically make sure that the enclosable chamber area may be
safe to work in but also reduce the risk of mixing clean and dirty
powder.
[0019] In one example embodiment of the present invention said
position detecting device is an electromagnetic radiation curtain
provided at an opening of said enclosable chamber. The
electromagnetic curtain may comprise at least one electromagnetic
radiation source and at least one electromagnetic radiation
sensor.
[0020] Said electromagnetic radiation source may be a laser source,
infra-red source or a visible light source. The advantage with an
electromagnetic curtain as a position detecting device is that it
is a cheap, well known and reliable solution. The number of
electromagnetic sources and detectors may be chosen arbitrarily. A
benefit with a larger number is that the dimension or even the
structure of the item may be recognized.
[0021] In another example embodiment of the present invention said
position detecting device may be a measurement arm or a robot arm
capable of registering the position in space.
[0022] Said robot arm or measurement arm may work in cooperation
with said electromagnetic radiation curtain or without assistance
from said electromagnetic radiation curtain.
[0023] In yet another example embodiment said method further
comprising the step of providing a hose from said powder suction
device to said robot arm.
[0024] An advantage with said embodiment is that the probability of
personal injuries and mixing of powder is even further reduced
since the powder handling may be performed without assistance of a
human being.
[0025] In still another example embodiment of the present invention
said enclosable chamber is a vacuum chamber. By enclosing the
powder bed in a vacuum chamber an electron beam may be used as a
source for fusing parts in the powder bed.
[0026] In yet another example embodiment of the present invention
said item is a nozzle of said powder suction device. This means
that as soon as the nozzle enters the enclosable chamber one or
more of the devices belonging to the additive manufacturing
apparatus are switched off while the powder suction device is
provided with power.
[0027] In still another example embodiment of the present invention
said method further comprising the step of switching on said powder
suction device by pressing an on switch. This means that the powder
suction device has actively to be turned on and this can only be
done as a foreign item such as the nozzle of said powder suction
device enters the enclosable chamber.
[0028] In still another example embodiment of the present invention
said electromagnetic radiation source is a laser source, infra-red
source or a visible light source. This means that any
electromagnetic radiation source and a corresponding sensor
sensitive to said electromagnetic radiation may be used as a
position detecting sensor. The number of radiation sources and
corresponding sensors may be chosen arbitrary from one to as many
as will fit in the available space.
[0029] In still another example embodiment of the present invention
said device is at least one of electron beam, laser beam, powder
distributor, vacuum pump, gas supply, work table. Disconnecting one
or more of the above mentioned devices will greatly improve the
service and operation of the additive manufacturing apparatus.
[0030] In still another example embodiment of the present invention
said powder suction device is an external unit in relation to the
enclosable chamber. This means that any suitable powder suction
device may be used. The power to said powder suction device may be
dependent on the presence of any foreign item in the enclosable
chamber.
[0031] Another object of the present invention is to provide safety
protection devices in an additive manufacturing apparatus which
will reduce or eliminate the safety issues mentioned above.
[0032] According to various embodiments, a safety protection device
in an additive manufacturing apparatus for forming a
three-dimensional article through successive fusion of parts of a
powder bed in an enclosable chamber, which parts corresponds to
successive cross sections of the three-dimensional article is
provided. The safety protection device comprises: a position
detecting device connected to a control unit, said position
detecting device being configured to detect whether a foreign
matter is within said enclosable chamber; and a switch for
switching off at least one device associated with said additive
manufacturing apparatus, said switch being controlled by said
control unit and being activated when said position detecting
device detects that said foreign matter is within said enclosable
chamber.
[0033] In another example embodiment said safety device still
further comprises a powder suction device that is controlled by a
control unit such that the powder suction device only received
power when said position detecting device detects that said foreign
matter is within said enclosable chamber.
[0034] In another example embodiment said position detecting device
is an electromagnetic radiation curtain provided at an opening of
said enclosable chamber, said electromagnetic curtain comprising at
least one electromagnetic radiation source and at least one
electromagnetic radiation sensor.
[0035] In still another example embodiment said enclosable chamber
is a vacuum chamber.
[0036] In yet another example embodiment said position detecting
device may be a measurement arm or a robot arm capable of
registering the position in space, wherein said foreign matter is a
nozzle of said powder suction device provided to said robot
arm.
[0037] In still another example embodiment said electromagnetic
radiation source is a laser source, infra-red source or a visible
light source.
[0038] In still another example embodiment said device is at least
one of electron beam, laser beam, powder distributor, vacuum pump,
gas supply, work table.
[0039] According to various embodiments, another safety protection
device in an additive manufacturing apparatus for forming a
three-dimensional article through successive fusion of parts of a
powder bed in an enclosable chamber, which parts corresponds to
successive cross sections of the three-dimensional article is
provided. The safety protection device comprises: a position
detecting device connected to a control unit, said position
detecting device being configured to detect whether a foreign
matter is within said enclosable chamber; and a powder suction
device configured such that said control unit only provides power
to said powder suction device when said position detecting device
detects that said foreign matter is within said enclosable
chamber.
[0040] In certain embodiments, wherein said position detecting
device is an electromagnetic radiation curtain provided at an
opening of said enclosable chamber, said electromagnetic curtain
comprising at least one electromagnetic radiation source and at
least one electromagnetic radiation sensor. In at least one such
embodiment, each of said at least one electromagnetic radiation
sensors are positioned adjacent and spaced apart relative to one
another along substantially an entirety of a first side of said
opening; each of said at least one electromagnetic radiation
sensors are positioned adjacent and spaced apart relative to one
another along substantially an entirety of a second side of said
opening, said second side being opposite said first side relative
to said opening; and each of said at least one electromagnetic
radiation sensors are configured, based at least in part upon their
relative positioning, to receive an emission from a corresponding
one of each of said at least one electromagnetic radiation sources,
said transmission and receipt of said emission defining said
electromagnetic radiation curtain across at opening.
[0041] More or less the same advantages of the example embodiment
of the method will apply to the above example embodiments of the
device.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)
[0042] The invention will be further described in the following, in
a non-limiting way with reference to the accompanying drawings.
Same characters of reference are employed to indicate corresponding
similar parts throughout the several figures of the drawings:
[0043] FIG. 1 depicts a first example embodiment of a device
according to the present invention;
[0044] FIG. 2 shows, in a schematic view, an example embodiment of
a device for producing a three dimensional product, in which device
the inventive method and device can be applied;
[0045] FIG. 3 depicts a second example embodiment of a device
according to the present invention;
[0046] FIG. 4 depicts a third example embodiment of a device
according to the present invention; and
[0047] FIG. 5 depicts an example embodiment of a flow chart of an
inventive method according to the present invention.
DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS
[0048] Various embodiments will now be described more fully
hereinafter with reference to the accompanying drawings, in which
some, but not all embodiments of the inventions are shown. Indeed,
the various embodiments of the present invention may be embodied in
many different forms and should not be construed as limited to the
embodiments set forth herein; rather, these embodiments are
provided so that this disclosure will satisfy applicable legal
requirements.
[0049] To facilitate the understanding of this invention, a number
of terms are defined below. Terms defined herein have meanings as
commonly understood by a person of ordinary skill in the areas
relevant to the present invention. Terms such as "a", "an" and
"the" are not intended to refer to only a singular entity, but
include the general class of which a specific example may be used
for illustration. The terminology herein is used to describe
specific embodiments of the invention, but their usage does not
delimit the invention, except as outlined in the claims.
[0050] The term "three-dimensional structures" and the like as used
herein refer generally to intended or actually fabricated
three-dimensional configurations (e.g. of structural material or
materials) that are intended to be used for a particular purpose.
Such structures, etc. may, for example, be designed with the aid of
a three-dimensional CAD system.
[0051] The term "electron beam" as used herein in various
embodiments refers to any charged particle beam. The sources of
charged particle beam can include an electron gun, a linear
accelerator and so on.
[0052] FIG. 2 depicts an embodiment of a freeform fabrication or
additive manufacturing apparatus 21 in which the inventive method
and device according to the present invention may be
implemented.
[0053] Said apparatus 21 comprising an electron beam gun 6;
deflection coils 7; two powder hoppers 4, 14; a build platform 2; a
build tank 10; a powder distributor 28; a powder bed 5; and a
vacuum chamber 20.
[0054] The vacuum chamber 20 is capable of maintaining a vacuum
environment by means of a vacuum system, which system may comprise
a turbomolecular pump, a scroll pump, an ion pump and one or more
valves which are well known to a skilled person in the art and
therefore need no further explanation in this context. The vacuum
system is controlled by a control unit 8.
[0055] The electron beam gun 6 is generating an electron beam which
is used for melting or fusing together powder material provided on
the build platform 2. At least a portion of the electron beam gun 6
may be provided in the vacuum chamber 20. The control unit 8 may be
used for controlling and managing the electron beam emitted from
the electron beam gun 6. At least one focusing coil (not shown), at
least one deflection coil 7, an optional coil for astigmatic
correction (not shown) and an electron beam power supply (not
shown) may be electrically connected to said control unit 8. In an
example embodiment of the invention said electron beam gun 6
generates a focusable electron beam with an accelerating voltage of
about 15-60 kV and with a beam power in the range of 3-10 Kw. The
pressure in the vacuum chamber may be 10.sup.-3 mbar or lower when
building the three-dimensional article by fusing the powder layer
by layer with the energy beam.
[0056] The powder hoppers 4, 14 comprise the powder material to be
provided on the build platform 2 in the build tank 10. The powder
material may for instance be pure metals or metal alloys such as
titanium, titanium alloys, aluminum, aluminum alloys, stainless
steel, Co--Cr alloys, nickel based superalloys etc.
[0057] The powder distributor 28 is arranged to lay down a thin
layer of the powder material on the build platform 2. During a work
cycle the build platform 2 will be lowered successively in relation
to a fixed point in the vacuum chamber. In order to make this
movement possible, the build platform 2 is in one embodiment of the
invention arranged movably in vertical direction, i.e., in the
direction indicated by arrow P. This means that the build platform
2 starts in an initial position, in which a first powder material
layer of necessary thickness has been laid down. Means for lowering
the build platform 2 may for instance be through a servo engine
equipped with a gear, adjusting screws etc.
[0058] An electron beam may be directed over said build platform 2
causing said first powder layer to fuse in selected locations to
form a first cross section of said three-dimensional article. The
beam is directed over said build platform 2 from instructions given
by the control unit 8. In the control unit 8 instructions for how
to control the electron beam for each layer of the
three-dimensional article is stored.
[0059] After a first layer is finished, i.e., the fusion of powder
material for making a first layer of the three-dimensional article,
a second powder layer is provided on said build platform 2. The
second powder layer is preferably distributed according to the same
manner as the previous layer. However, there might be alternative
methods in the same additive manufacturing machine for distributing
powder onto the work table. For instance, a first layer may be
provided by means of a first powder distributor 28, a second layer
may be provided by another powder distributor. The design of the
powder distributor is automatically changed according to
instructions from the control unit 8. A powder distributor 28 in
the form of a single rake system, i.e., where one rake is catching
powder fallen down from both a left powder hopper 4 and a right
powder hopper 14, the rake as such can change design.
[0060] After having distributed the second powder layer on the
build platform, the energy beam is directed over said work table
causing said second powder layer to fuse in selected locations to
form a second cross section of said three-dimensional article.
Fused portions in the second layer may be bonded to fused portions
of said first layer. The fused portions in the first and second
layer may be melted together by melting not only the powder in the
uppermost layer but also remelting at least a fraction of a
thickness of a layer directly below said uppermost layer.
[0061] In the case where an electron beam is used, it is necessary
to consider the charge distribution that is created in the powder
as the electrons hit the powder bed 5. The invention is, at least
partly, based on the realization that the charge distribution
density depends on the following parameters: beam current, electron
velocity (which is given by the accelerating voltage), beam
scanning velocity, powder material and electrical conductivity of
the powder, i.e. mainly the electrical conductivity between the
powder grains. The latter is in turn a function of several
parameters, such as temperature, degree of sintering and powder
grain size/size distribution.
[0062] Thus, for a given powder, i.e. a powder of a certain
material with a certain grain size distribution, and a given
accelerating voltage, it is possible, by varying the beam current
(and thus the beam power) and the beam scanning velocity, to affect
the charge distribution.
[0063] FIG. 1 illustrates schematically an additive manufacturing
device 21 with the inventive safety protection device.
[0064] Three-dimensional articles may be manufactured inside the
enclosable chamber 20 through successive fusion of parts of a
powder bed, which parts corresponds to successive cross sections of
the three-dimensional article as described above in connection with
FIG. 2. The enclosable chamber 20 comprises a door 30. When the
door is closed vacuum may be provided inside said enclosable
chamber. The vacuum may be accomplished through one or several
vacuum pumps (not illustrated) connected to said enclosable
chamber.
[0065] Said safety device comprising a position detecting device
connected to a control unit 65 to detect if a foreign item is
within said enclosable chamber. In FIG. 1 said position detecting
device is in the form of electromagnetic emitting devices 50, 52,
54, 56, 68, 60 and electromagnetic sensors 70, 72, 74, 76, 78 80.
The sensors 70, 72, 74, 76, 78 80 are connected to the control unit
65. The control unit registers if each and every sensor is
receiving or not receiving the electromagnetic radiation emitted
from the emitting devices 50, 52, 54, 56, 68, 60.
[0066] Said safety device further comprising a switch (not
illustrated) for switching off at least one device belonging to
said additive manufacturing apparatus 21 controlled by said control
unit 65 when said position detecting device 50, 52, 54, 56, 68, 60,
70, 72, 74, 76, 78 80 is detecting said foreign item to be within
said enclosable chamber. A foreign item may be detected if one or
more of the sensors 70, 72, 74, 76, 78 80 does not receive the
electromagnetic radiation emitted by the emitting devices 50, 52,
54, 56, 68, 60 because the foreign item is breaking the
electromagnetic connection between the emitting device 50, 52, 54,
56, 68, 60 and said sensor 70, 72, 74, 76, 78 80. The foreign item
may for instance be any part of the body or a tool. The tool may
for instance be a nozzle 40 of a powder suction device 35.
[0067] The number of emitting devices in FIG. 3 is exemplified to
be 6, however, any number of emitting devices and corresponding
number of sensors may be used. Of course, using only one sensor in
a wide opening would increase the risk of missing any item that is
inside the enclosable chamber. If using a larger number of sensors
and emitters, which are close to each other, said sensors and
emitters may be used to estimate the size and form of the foreign
item breaking the electromagnetic connection between the emitting
device 50, 52, 54, 56, 68, 60 and said sensor 70, 72, 74, 76, 78
80.
[0068] When at least one electromagnetic connection is broken
between the emitting device 50, 52, 54, 56, 68, 60 and said sensor
70, 72, 74, 76, 78 80, the control unit 65 receives a signal that
said sensor(s) are missing the signal from the emitter(s). The
control unit 65 then disconnect at least one device belonging to
the additive manufacturing apparatus 21, for instance an electron
gun 6, a powder distributor system or any other mechanically moving
part attached inside or outside the enclosable chamber 20. Said
control unit also switches on the power to a powder suction device
35 when said at least one electromagnetic connection is broken
between the emitting device 50, 52, 54, 56, 68, 60 and said sensor
70, 72, 74, 76, 78 80.
[0069] It requires a foreign matter detected to be inside the
enclosable chamber 20 in order to provide power to the powder
suction device and the means for managing this is the control unit
65. The powder suction device is useless as long as there is no
foreign matter inside the enclosable chamber. Said foreign matter
may for instance be the nozzle 40 provided on a hose 37 connected
to said powder suction device 35. Said foreign matter may also be a
tool, any part of a human body or any other part which is moved
from the outside of the enclosable chamber to the inside of the
enclosable chamber.
[0070] The actual on-switching of said powder suction device may be
performed by an on-switch 39 provided on the powder suction device
35 as such or in the vicinity of the nozzle 40. This means that it
may require require two events for switching on the powder suction
device, firstly there may have to be a foreign matter inside the
enclosable chamber 20 and secondly the on switch 39 may have to be
activated (switched on).
[0071] FIG. 4 illustrates another example embodiment of a position
detecting device. Here the position detecting device may be a robot
arm or a measurement arm 90 (see also FIG. 3) having a first
rotational axis 34 and a second rotational axis 32. Between the
first rotational axis 34 and the second rotational axis it s
provided a first arm 38. A second arm 39 is provided at said second
rotational axis with its first end. A second and of said second arm
may be provided with a gripping device 33. To said gripping device
33 may said powder suction hose 37 or powder suction nozzle 40 be
attached. The measurement arm may be manufactured by Baces3D.
[0072] In one embodiment the distance between the powder suction
device 35 and the additive manufacturing apparatus 21 is fixed. A
first angle of the first arm 38 relative to a predetermined
position and a second angle of the second arm 39 relative said
first arm 38 then determined the position of the grip device 33
(see also FIG. 3). Assuming that the grip device is gripping the
powder suction device at a predetermined position one can then
determine the position of the nozzle from said first and second
angles. There will be a given set of first and second angles for
which said nozzle 40 can be said to be within the enclosable
chamber 20, given that the grip device 33 is gripping the hose 37
at a predetermined position, from which predetermined position the
distance to the nozzle 40 is known. Once said grip device 33 of
said robot arm or measurement arm 90 or any tool attached to the
grip device is within said enclosable chamber 20 the control unit
65 switches off at least one device 6 belonging to the additive
manufacturing apparatus. Said control unit 65 also switches on the
power to the powder suction device 35 when said grip device 33 of
said robot arm or measurement arm 90 or any tool (such as the
nozzle 40 of the powder suction device 35) attached to the grip
device is within said enclosable chamber 20.
[0073] FIG. 3 is a combination of the embodiment in FIG. 1 and FIG.
4. In FIG. 3 a robot arm or measurement arm 90 and an
electromagnetic emitters and sensors are used as position detecting
devices. The determination of the position of the grip device 33 or
any tool attached to said grip device may be determined in the same
way as disclosed in relation to FIG. 4. The functionality of the
electromagnetic emitting and sensing devices are equal to what is
disclosed in relation to FIG. 1. In FIG. 3 the power to any
predetermined number of devices 6 belonging to the additive
manufacturing apparatus 21 may be switched off when at least one of
the electromagnetic sensors 70, 72, 74, 76, 78, 80 is not receiving
the electromagnetic radiation from the corresponding emitters 50,
52, 54, 56, 58, 60. However, for providing power to the powder
suction device 35 it requires not only that at least one of the
sensors is not receiving the electromagnetic radiation from its
corresponding emitter. It also requires that the grip device or a
predefined part of the robot or measurement arm is determined to be
within the enclosable chamber given by the position of the
measurement or robot arm. This embodiment has the advantage that
the powder suction device cannot be manipulated to start in a
"wrong" area to thereby give the possibility to collect dirty
powder from for example the floor. In FIG. 3, the grip device or
any tool attached to the grip device, such as the hose from the
powder suction device, has to be identified to be within the
enclosable chamber in order to provide power to the powder suction
device. The actual on-switching of the powder suction device can be
automatically, i.e., as soon as the nozzle is determined to be
within the enclosable chamber. Another alternative to switch on the
powder suction device is to press an on switch. However, the on
switch will not be active unless the nozzle is determined to be
within the enclosable chamber.
[0074] FIG. 5 depicts schematically an example embodiment of a flow
chart of an inventive method for providing safety protection in an
additive manufacturing apparatus according to the present
invention.
[0075] In a first step 502 a position detecting device is provided
which is connected to a control unit to detect if a foreign item is
within said enclosable chamber. The position detecting device may
be a robot arm or a measurement arm and/or at least one
electromagnetic sensor and corresponding electromagnetic emitting
device as disclosed above.
[0076] Then it is determined if a foreign item is within the
enclosable chamber 20. The question to be answered in box 504 is,
is any foreign item within the enclosable chamber? If the answer is
NO, the same question is asked again within a predetermined time
frame. The time frame may be in the range of microseconds. If the
answer is YES it is a foreign item is within the enclosable chamber
20, the method is moved to the second step 506. In the second step
506 at least one device of the additive manufacturing apparatus is
switched off. When said step is completed the method moves on to
the third step 508. In the third step 508 providing the powder
suction device is provided with power.
[0077] In an alternative embodiment of said method said at least
one device belonging to the additive manufacturing apparatus is
switched off if at least one of the sensors 70, 71, 74, 76, 78, 80
is not receiving the electromagnetic radiation emitted from a
corresponding emitter 50, 52, 54, 56, 68, 60. The power to the
powder suction device is provided when the grip device or any
predefined part of the measurement arm or the robot arm or a tool
attached to said grip arm is determined to be within said
enclosable chamber 20.
[0078] In still an alternative embodiment of said method said at
least one device belonging to the additive manufacturing apparatus
is switched off when for instance the grip device of the robot arm
or measurement arm or a tool attached to said grip arm is
determined to be within said enclosable chamber 20. The power to
the powder suction device is provided when the grip device of the
robot arm or measurement arm or a tool attached to said grip arm is
determined to be within said enclosable chamber 20.
[0079] The invention is not limited to the above-described
embodiments and many modifications are possible within the scope of
the following claims. Such modifications may, for example, involve
using a different source of energy beam than the exemplified
electron beam such as laser beam. Other materials than metallic
powder may be used, such as powder of polymers or powder of
ceramics. Indeed, a person of ordinary skill in the art would be
able to use the information contained in the preceding text to
modify various embodiments of the invention in ways that are not
literally described, but are nevertheless encompassed by the
attached claims, for they accomplish substantially the same
functions to reach substantially the same results. Therefore, it is
to be understood that the invention is not limited to the specific
embodiments disclosed and that modifications and other embodiments
are intended to be included within the scope of the appended
claims. Although specific terms are employed herein, they are used
in a generic and descriptive sense only and not for purposes of
limitation.
* * * * *