Title: Ventilation and cooling in selective deposition modeling
Abstract: A ventilation and cooling system for a selective deposition modeling apparatus dispensing a curable material. The ventilation and cooling system captures airborne contaminants in the apparatus making the apparatus suitable for use in an office environment. A pressure drop is established within the apparatus to assure that all air that enters the apparatus passes through a filter which captures the airborne contaminants before the air is expelled from the apparatus. Sensors are provided to assure that the ventilation and cooling system is function properly, and if not, the apparatus is either shut down or a signal is provided to the operator indicating that the system is not functioning properly.
Patent Number: 7,008,206 Issued on 03/07/2006 to Fong, et al.
| Inventors:
|
Fong; Jon Jody (Calabasas, CA);
Soliz; Raymond M. (Chatsworth, CA);
Reynolds; Gary Lee (Santa Clarita, CA)
|
| Assignee:
|
3D Systems, Inc. (Valencia, CA)
|
| Appl. No.:
|
180380 |
| Filed:
|
June 24, 2002 |
| Current U.S. Class: |
425/73; 425/174 |
| Current Intern'l Class: |
B29C 67/00 (20060101) |
| Field of Search: |
96/252
454/252,62
425/174,174.4,73
|
References Cited [Referenced By]
U.S. Patent Documents
| 4634368 | Jan., 1987 | Diaz.
| |
| 4934920 | Jun., 1990 | Yamauchi et al.
| |
| 5136515 | Aug., 1992 | Helinski.
| |
| 5204055 | Apr., 1993 | Sachs et al.
| |
| 5216616 | Jun., 1993 | Masters.
| |
| 5312297 | May., 1994 | Dieckert et al.
| |
| 5340433 | Aug., 1994 | Crump.
| |
| 5534309 | Jul., 1996 | Liu.
| |
| 5555176 | Sep., 1996 | Menhennett et al.
| |
| 5704955 | Jan., 1998 | Giles.
| |
| 5717572 | Feb., 1998 | Smith et al.
| |
| 5855836 | Jan., 1999 | Leyden et al.
| |
| 5866058 | Feb., 1999 | Batchelder et al.
| |
| 5904889 | May., 1999 | Serbin et al.
| |
| 6133355 | Oct., 2000 | Leyden et al.
| |
| 6198628 | Mar., 2001 | Smith.
| |
| 6259962 | Jul., 2001 | Gothait.
| |
| 2002/0016386 | Feb., 2002 | Napadensky.
| |
| Foreign Patent Documents |
| 97/11837 | Apr., 1997 | WO.
| |
| 00/11092 | Mar., 2000 | WO.
| |
| 01/26023 | Apr., 2001 | WO.
| |
| 01/68375 | Sep., 2001 | WO.
| |
Other References
U.S. Appl. No. 09/970,956, filed Oct. 3, 2001 by Varnon et al.
U.S. Appl. No. 09/971,247, filed Oct. 3, 2001 by Schmidt et al.
U.S. Appl. No. 09/971,337, filed Oct. 3, 2001 by Schmidt.
U.S. Appl. No. 10/001,727, filed Dec. 5, 2001 by Fong.
U.S. Appl. No. 10/140,426, filed May 7, 2002 by Sherwood.
U.S. Appl. No. 10/157,575, filed May 28, 2002 by Fong.
|
Primary Examiner: Smith; Duane
Assistant Examiner: Luk; Emmanuel S.
Attorney, Agent or Firm: Curry; James E., D'Alessandro; Ralph
Claims
What is claimed is:
1. A ventilation and cooling system for capturing airborne contaminants in a
selective deposition modeling apparatus dispensing a curable and flowable build
material layer by layer to form a three-dimensional object, the ventilation and
cooling system comprising:
a containment chamber surrounding the selective deposition modeling apparatus,
the containment chamber having a dispensing device for layerwise selective dispensing
of the build material, a heat generating exposure system to cure the build material
in each layer and at least one air inlet duct and at least one air exit duct, the
containment chamber further having unsealed gaps;
at least one air-moving device in communication with the air inlet of the containment
chamber creating a first flow of air entering the apparatus;
at least one air-moving device in communication with the air exit duct creating
a second flow of air exiting the apparatus;
a third flow of air that is drawn into the apparatus through the unsealed gaps
at a flow rate which, when added to the flow rate of the first flow of air, substantially
equals the flow rate of the second flow of a when a steady state condition is established
between the first flow of air, the second flow of air, and the third flow of air;
a filter in communication with the air exit duct for receiving the second flow
of air to capture airborne contaminants from the second flow of air, the airborne
contaminants comprising vapors of the curable build material; and
wherein the second flow of air has a flow rate that is greater than the flow
rate of the first flow of air.
2. The ventilation and cooling system of claim 1 wherein the pressure inside
the containment chamber is less than atmospheric pressure when the steady state
condition is established.
3. The ventilation and cooling system of claim 2 wherein the pressure inside
the containment chamber when the steady state condition is established is between
about 0.05 In H
2O to about 1.0 In H
2O less than atmospheric pressure.
4. The ventilation and cooling system of claim 2 further comprising:
a pressure sensor in communication with the selective deposition modeling apparatus,
the pressure sensor configured to determine the pressure difference between the
pressure inside the containment chamber and atmospheric pressure when the steady
state condition is established, wherein to pressure sensor shuts down the selective
deposition modeling apparatus when the pressure difference determined indicates
the ventilation and cooling system is not functioning properly.
5. The ventilation and cooling system of claim 4 wherein the ventilation and
cooling system is not functioning properly when the pressure difference determined
by the pressure sensor is about 0.05 In H
2O less than atmospheric pressure.
6. The ventilation and cooling system of claim 2 further comprising:
a pressure sensor in communication with the selective deposition modeling apparatus,
the pressure sensor configured to determine the pressure difference between the
pressure inside the containment chamber and atmospheric pressure when the steady
state condition is established, wherein the pressure sensor signals the selective
deposition modeling apparatus that the ventilation and cooling system is not functioning
properly when the pressure difference determined indicates the ventilation and
cooling system is not functioning properly.
7. The ventilation and cooling system of claim 6 wherein the ventilation and
cooling system is not functioning properly when the pressure difference determined
by the pressure sensor is about 0.05 In H
2O less than atmospheric pressure.
8. The ventilation and cooling system of claim 2 further comprising:
a pressure sensor in communication with the selective deposition modeling apparatus,
the pressure sensor configured to determine the pressure difference between the
second flow of air and atmospheric pressure when the steady state condition is
established, the pressure difference being measured prior to the second flow of
air being received by the filter, wherein the pressure sensor shuts down the selective
deposition apparatus when the pressure difference determined by the pressure sensor
is greater than a minimum allowable pressure difference indicating the filter needs
to be replaced.
9. The ventilation and cooling system of claim 2 further comprising:
a pressure sensor in communication with the selective deposition modeling apparatus,
the pressure sensor configured to determine the pressure difference between the
second flow of air and atmospheric pressure when the steady state condition is
established, the pressure difference being measured prior to the second flow of
air being received by the filter, wherein the pressure sensor signals the selective
deposition modeling apparatus that the filter needs to be replaced when the pressure
difference determined by the pressure sensor is greater than a minimum allowable
pressure difference indicating the filter needs to be replaced.
10. The ventilation and cooling system of claim 1 wherein the filter is an activated
charcoal filter.
11. The ventilation and cooling system of claim 1 having five air inlet ducts,
each air inlet duct in communication with an air-moving device, wherein the first
flow of air entering the apparatus comprises the air entering all five inlet ducts.
12. A selective deposition modeling apparatus for forming a three-dimensional
object from a flowable and curable material in a build environment, the apparatus
receiving data corresponding to layers of the three-dimensional object, the apparatus comprising:
a support means affixed to the apparatus for supporting the three-dimensional
object in the build environment;
a dispensing means affixed to the apparatus and in communication with the support
means for selectively dispensing the curable material in the build environment
according to the computer data to form the layers of the three-dimensional object;
a flash exposure means affixed to the apparatus for curing the dispensed material,
the flash exposure means in communication with the support means;
a ventilation and cooling system for capturing airborne contaminants in the apparatus,
the ventilation and cooling system comprising:
a) a containment chamber surrounding the selective deposition modeling apparatus,
the containment chamber having at least one air inlet duct and one air exit duct
and unsealed gaps;
b) at least one air-moving device in communication with the air inlet of the
containment chamber creating a first flow of air entering the apparatus;
c) at least one air-moving device in communication with the air exit duct creating
a second flow of air exiting the apparatus;
d) a flash cooling system in communication with the flash exposure means for
providing steady state cooling of the flash exposure means, the flash cooling system
comprising an air duct receiving at least a portion of the first flow of air for
cooling the flash exposure means and delivering the portion of the first flow of
air to the second flow of air;
e) a third flow of air drawn into the apparatus through the unsealed gaps in
the containment chamber at a flow rate which, when added to the flow rate of the
first flow of air, substantially equals the flow rate of the second flow of air
when a steady state condition is established between the first flow of air, the
second flow of air, and the third flow of air;
f) a filter in communication with the air exit duct for receiving the second
flow of air to capture airborne contaminants from the second flow of air, the airborne
contaminants comprising vapors of the curable build material; and
wherein the second flow of air has a flow rate that is greater than the flow
rate of the first flow of air.
13. The apparatus of claim 12 wherein the pressure inside the containment chamber
is less than atmospheric pressure when the steady state condition is established.
14. The apparatus of claim 13 wherein the pressure inside the containment chamber
when the steady state condition is established is between about 0.05 In H
2O
to about 1.0 In H
2O less than atmospheric pressure.
15. The apparatus of claim 13 further comprising;
a pressure sensor in communication with the selective deposition modeling apparatus,
the pressure sensor configured to determine the pressure difference between the
pressure inside the containment chamber and atmospheric pressure when the steady
state condition is established, wherein the pressure sensor shuts down the selective
deposition modeling apparatus when the pressure difference determined indicates
the ventilation and cooling system is not functioning properly.
16. The apparatus of claim 15 wherein the ventilation and cooling system is not
functioning properly when the pressure difference determined by the pressure sensor
is about 0.05 In H
2O less than atmospheric pressure.
17. The apparatus of claim 13 farther comprising:
a pressure sensor in communication with the selective deposition modeling apparatus,
the pressure sensor configured to determine the pressure difference between the
pressure inside the containment chamber and atmospheric pressure when the steady
state condition is established, wherein the pressure sensor signals the selective
deposition modeling apparatus that the ventilation and cooling system is not functioning
properly when the pressure difference determined indicates the ventilation and
cooling system is not functioning properly.
18. The apparatus of claim 17 wherein the ventilation and cooling system is not
functioning properly when the pressure difference determined by the pressure sensor
is about 0.05 In H
2O less than atmospheric pressure.
19. The apparatus of claim 13 further comprising:
a pressure sensor in communication with the selective deposition modeling apparatus,
the pressure sensor configured to determine the pressure difference between the
second flow of air and atmospheric pressure when the steady state condition is
established, the pressure difference being measured prior to the second flow of
air being received by the filter, wherein the pressure sensor shuts down the selective
deposition apparatus when the pressure difference determined by the pressure sensor
is greater than a minimum allowable pressure difference indicating the filter needs
to be replaced.
20. The apparatus of claim 13 further comprising:
a pressure sensor in communication with the selective deposition modeling apparatus,
the pressure sensor configured to determine the pressure difference between the
second flow of air and atmospheric pressure when the steady state condition is
established, the pressure difference being measured prior to the second flow of
air being received by the filter, wherein the pressure sensor signals the selective
deposition modeling apparatus that the filter needs to be replaced when the pressure
difference determined by the pressure sensor is greater than a minimum allowable
pressure difference indicating the filter needs to be replaced.
21. The apparatus of claim 12 wherein the filter is an activated charcoal filter.
22. The apparatus of claim 12 having five air inlet ducts, each air inlet duct
in communication with an air-moving device, wherein the first flow of air entering
the apparatus comprises the air entering all five inlet ducts.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates in general to solid deposition modeling, and in particular
to a method and apparatus for providing ventilation and cooling to make solid deposition
modeling with curable materials viable in an office environment.
2. Description of the Prior Art
Recently, several new technologies have been developed for the rapid creation
of models, prototypes, and parts for limited run manufacturing. These new technologies
are generally called Solid Freeform Fabrication techniques, and are herein referred
to as "SFF." Some SFF techniques include stereolithography, selective deposition
modeling, laminated object manufacturing, selective phase area deposition, multi-phase
jet solidification, ballistic particle manufacturing, fused deposition modeling,
particle deposition, laser sintering, and the like. Generally in SFF techniques,
complex parts are produced from a modeling material in an additive fashion as opposed
to conventional fabrication techniques, which are generally subtractive in nature.
In most SFF techniques, structures are formed in a layer by layer manner by solidifying
or curing successive layers of a build material. For example, in stereolithography
a tightly focused beam of energy, typically in the ultraviolet radiation band,
is scanned across a layer of a liquid photopolymer resin to selectively cure the
resin to form a structure. In Selective Deposition Modeling, herein referred to
as "SDM," a build material is typically jetted or dropped in discrete droplets,
or extruded through a nozzle, in order to solidify on contact with a build platform
or previous layer of solidified material in order to build up a three-dimensional
object in a layerwise fashion. Other synonymous names for SDM which are used in
this industry are solid object imaging, solid object modeling, fused deposition
modeling, selective phase area deposition, multi-phase jet modeling, three-dimensional
printing, thermal stereolithography, selective phase area deposition, ballistic
particle manufacturing, fused deposition modeling, and the like. Ballistic particle
manufacturing is disclosed in, for example, U.S. Pat. No. 5,216,616 to Masters.
Fused deposition modeling is disclosed in, for example, U.S. Pat. No. 5,340,433
to Crump. Three-dimensional printing is disclosed in, for example, U.S. Pat. No.
5,204,055 to Sachs et al. Often a thermoplastic material to having a low-melting
point is used as the solid modeling material in SDM; which is delivered through
a jetting system such as an extruder or print head. One type of SDM process which
extrudes a thermoplastic material is described in, for example, U.S. Pat. No. 5,866,058
to Batchelder et al. One type of SDM process utilizing ink jet print heads is described
in, for example, U.S. Pat. No. 5,555,176 to Menhennett et al.
Recently, there has developed an interest in utilizing curable materials
in SDM. One of the first suggestions of using a radiation curable build material
in SDM is found in U.S. Pat. No. 5,136,515 to Helinski, wherein it is proposed
to selectively dispense a UV curable build material in an SDM system. Some of the
first UV curable material formulations proposed for use in SDM systems are found
in Appendix A of International Patent Publication No. WO 97/11837, where three
reactive material compositions are provided. More recent teachings of using curable
materials in various selective deposition modeling systems are provided in U.S.
Pat. No. 6,259,962 to Gothait; U.S. Pat. Nos. 6,133,355 and 5,855,836 to Leyden
et al; U.S. Pat. App. Pub. No. U.S. 2002/0016386 A1; and International Publication
Numbers WO 01/26023, WO 00/11092, and WO 01/68375.
These curable materials generally contain photoinitiators and photopolymers
which, when exposed to ultraviolet radiation (UV), begin to cross-link and solidify.
As this occurs, a significant amount of exothermic heat is produced, which must
be removed from the system as objects are built. In addition, care must be taken
in working with these materials as prolonged dermal contact can lead to sensitization,
and their vapors can provide undesirable odors. Thus, it is important to minimize
human contact with these materials when in liquid form, and to prevent these materials
from becoming airborne in an office environment when in vapor form.
For SDM systems that selectively dispense curable materials, a radiation curing
step is needed to initiate the curing process. However, radiation curing exposure
systems themselves generate significant amounts of heat, whether they are flash
systems or continuous flood systems. The high levels of heat generated by these
lamps pose significant problems in SDM. For instance, the heat generated by these
lamps can thermally initiate curing of the material in the SDM dispensing device
or material delivery system rendering the apparatus inoperable. Being able to remove
this heat in an SDM apparatus is crucial to acceptable operation of the system.
One of the advantages of first generation SDM machines that worked with thermoplastic
waxes to build objects was that the machines could be used in an office environment.
This is because the waxes are essentially benign in nature, requiring no need to
prevent human contact. Further, power consumption and heat generation is not much
more when dispensing these materials from SDM compared to other office equipment
such as photocopier. However, making an SDM apparatus utilizing curable materials
for use in an office environment is no trivial task. Power consumption must be
kept at a minimum so as to meet conventional power requirements found in an office,
such as 20 A/115V service. Heat generation must be kept low enough so that standard
office air conditioning systems can maintain a comfortable office environment,
and the cooling system of the SDM apparatus must be sufficient to remove the generated
heat from the system. Also the ventilation system must be able to trap vapors within
the apparatus and prevent their potentially odorous release into the office environment.
Thus, there is a need to develop an inexpensive ventilation and cooling system
for use in an SDM apparatus capable of removing large amounts of localized heat
while also preventing vapors from being released into the environment. These and
other difficulties of the prior art have been overcome according to the present invention.
BRIEF SUMMARY OF THE INVENTION
The present invention provides its benefits across a broad spectrum. While the
description which follows hereinafter is meant to be representative of a number
of such applications, it is not exhaustive. As will be understood, the basic methods
and apparatus taught herein can be readily adapted to many uses. It is intended
that this specification and the claims appended hereto be accorded a breadth in
keeping with the scope and spirit of the invention being disclosed despite what
might appear to be limiting language imposed by the requirements of referring to
the specific examples disclosed.
It is one aspect of the present invention to provide a ventilation and cooling
system for an SDM apparatus that captures airborne contaminants within the apparatus.
It is another aspect of the present invention to provide a ventilation and cooling
system for an SDM apparatus that establishes a pressure difference or drop within
the apparatus that is less than atmospheric pressure.
It is a feature of the present invention that all air that passes through an
SDM
apparatus utilizing the present invention ventilation and cooling system passes
though a filter that captures substantially all airborne contaminants.
It is another feature of the present invention that a pressure sensor can shut
down the SDM apparatus or signal the operator when the ventilation and cooling
system is not functioning properly.
It is yet another feature of the present invention that a pressure sensor can
shut down the SDM apparatus or signal the operator when the filter of the ventilation
and cooling system needs replacement.
It is an advantage of the present invention that an SDM apparatus utilizing curable
build materials can be operated in an office environment.
These and other aspects, features, and advantages are achieved/attained in
the method and apparatus of the present invention. The present invention ventilation
and cooling method comprises providing a containment chamber surrounding a selective
deposition modeling apparatus having at least one air inlet duct and at least one
air exit duct; establishing a first flow of air entering the apparatus through
the air inlet duct; establishing a second flow of air exiting the apparatus through
the air exit duct; and passing the second flow of air through a filter prior to
the second flow of air exiting the apparatus. The filter captures airborne contaminants
from the second flow of air containing vapors of the curable build material. The
second flow of air has a flow rate that is greater than the flow rate of the first
flow of air which establishes a third flow of air that is drawn into the apparatus
through unsealed gaps in the containment chamber. A steady state condition is established
wherein the flow rate of the third flow of air, when added to the flow rate of
the first flow of air, substantially equals the flow rate of the second flow of
air. When the steady state condition is established, the pressure inside the containment
chamber is less than atmospheric pressure. This assures that all air entering the
SDM apparatus passes through the filter prior to being expelled from the apparatus.
The present invention ventilation and cooling system for a selective deposition
modeling apparatus comprises a containment chamber surrounding the apparatus having
at least one air inlet duct and at least one air exit duct, at least one air-moving
device in communication with the air inlet duct creating a first flow of air entering
the apparatus, at least one air-moving device in communication with the air exit
duct creating a second flow of air exiting the apparatus, and a filter in communication
with the air exit duct for receiving the second flow of air to capture airborne
contaminants from the second flow of air. The second flow of air has a flow rate
greater than the flow rate of the first flow of air, which establishes a third
flow of air entering the apparatus through unsealed gaps in the containment chamber.
The pressure inside the containment chamber is less than atmospheric pressure,
and a pressure sensor can be provided to monitor this pressure difference to either
shut off the apparatus or signal the operator that the ventilation and cooling
system is not functioning properly.
A present invention selective deposition modeling apparatus comprises a support
means affixed to the apparatus for supporting three-dimensional objects in the
build environment, a dispensing means affixed to the apparatus and in communication
with the support means for dispensing a curable material in the build environment
according to computer data to form the layers of the three-dimensional object,
a flash exposure means affixed to the apparatus for curing the dispensed material,
a flash cooling system in communication with the flash exposure means for providing
steady state cooling of the flash exposure means, and a ventilation and cooling
system for capturing airborne contaminants in the apparatus. The ventilation and
cooling system comprises a containment chamber surrounding the selective deposition
modeling apparatus having at least one air inlet duct and one air exit duct, at
least one air-moving device in communication with the air inlet of the containment
chamber creating a first flow of air entering the apparatus, at least one air-moving
device in communication with the air exit duct creating a second flow of air exiting
the apparatus, and a filter in communication with the air exit duct for receiving
the second flow of air to capture airborne contaminants from the second flow of
air. Because of the ventilation and cooling system, the SDM apparatus is suitable
for operation in an office environment.
BRIEF DESCRIPTION OF THE DRAWINGS
The aspects, features, and advantages of the present invention will become apparent
upon consideration of the following detailed disclosure of the invention, especially
when it is taken in conjunction with the accompanying drawings wherein:
FIG. 1 is a diagrammatic side view of a solid deposition modeling apparatus
incorporating the present invention flash cure system.
FIG. 2 is a diagrammatic side view of a preferred solid deposition modeling
apparatus incorporating the present invention flash curing system.
FIG. 3 is an electrical schematic of the present invention flash curing system.
FIG. 4 is a cross-sectional view of reflector housing assembly for the present
invention flash system.
FIG. 5 is a cross-sectional view of another reflector housing assembly for the
present invention flash system.
FIG. 6 is a diagrammatic side view of the solid deposition modeling apparatus
of FIG. 3 shown in conjunction with the reflector housing assembly of FIG. 4.
FIG. 7 is an isometric view of the apparatus of FIG. 2 for practicing the present invention.
To facilitate understanding, identical reference numerals have been used, where
possible, to designate identical elements that are common in the figures.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
While the ventilation and cooling techniques of the present invention are applicable
to all SFF techniques, the invention will be described with respect to an SDM apparatus
utilizing an ink jet print head dispensing an ultraviolet radiation curable phase
change material. However, it is to be appreciated that the ventilation and cooling
techniques of the present invention can be adapted for use with any SFF apparatus
generating airborne contaminants in order to make the apparatus acceptable for
use in an office environment.
As used herein, the term "a flowable state" of a build material is a state wherein
the material is unable to resist shear stresses that are induced by a dispensing
device, such as those induced by an ink jet print head when dispensing the material,
causing the material to move or flow. Preferably, the flowable state of the build
material is a liquid state, however, the flowable state of the build material may
also exhibit thixotropic-like properties. The term "solidified" and "solidifiable"
as used herein refer to the phase change characteristics of a material where the
material transitions from the flowable state to a non-flowable state. A "non-flowable
state" of a build material is a state wherein the material is sufficiently self-supportive
under its own weight so as to hold its own shape. A build material existing in
a solid state, a gel state, or paste state, are examples of a non-flowable state
of a build material for the purposes herein. In addition, the term "cured" or "curable"
refers to any polymerization reaction. Preferably, the polymerization reaction
is triggered by controlled exposure to actinic radiation or thermal heat. Most
preferably, the polymerization reaction involves the cross-linking of monomers
and oligomers initiated by exposure to actinic radiation in the ultraviolet wavelength
band. Further, the term "cured state" refers to a material, or portion of a material,
in which the polymerization reaction has substantially completed. It is to be appreciated
that as a general matter the material can easily transition between the flowable
and non-flowable state prior to being cured; however, once cured, the material
cannot transition back to a flowable state and be dispensed by the apparatus. In
addition, the term "airborne contaminants" includes any particulate matter that
may be suspended in air and also any airborne vapors of both the curable phase
change build material and phase change support material. Furthermore, the term
"air-moving device" refers to any device that can establish a flow of air, such
as an axial fan, a centrifugal fan, a mixed flow fan, a cross flow fan, and combinations
thereof. For the purposes herein, a positive displacement pump may also be used
as an air-moving device, if desired
The SDM apparatus incorporating the present invention ventilation and cooling
system dispenses a curable phase change material from a Z850 piezoelectric ink
jet print head available from Xerox Corporation of Wilsonville, Oreg., although
other dispensing devices could be used, if desired. The material dispensed from
the Z850 print head desirably has a viscosity of between about 13 to about 14 centipoise
at a dispensing temperature of about 80° C. The dispensing methodology of
this system is described in greater detail in U.S. patent application Ser. No.
09/971,337, assigned to the assignee of the present invention.
A number of radiation curable phase change formulations were developed to be
dispensed
by the Z850 print head to form three-dimensional objects. An exemplary build material
formulation comprises 6.5% by weight Urethane Acrylate (CN980), 6.0% by weight
Epoxy Acrylate (E3200), 18.7% by weight Urethane Acrylate (CN2901), 41.05% by weight
Triethylene glycol dimethacrylate (SR205), 12.0% by weight Polypropylene Glycol
Monomethacrylate (SR604), 10.0% by weight Urethane Wax (ADS038), 2.0% by weight
Urethane Wax (ADS043), and 3.75% by weight Photo-initiator (I-184). The components
CN 980, CN2901, SR 205, SR604, and SR 493D are available from Sartomer Company,
Inc. of Exton, Pa. The components ADS038 and ADS043 are available from American
Dye Source, Inc. of Quebec, Canada. The component E3200 is available from UCB Chemical,
Inc. of Atlanta, Ga., and the component I-184 is available from Ciba Specialty
Chemicals, Inc. of New York, N.Y.
An exemplary non-curable phase change support material formulation comprises
70%
by weight octadecanol available from Ruger Chemical Co., Inc., of Irvington, N.J,
and 30% by weight of a tackifier sold under the designation of KE 100 available
from Arakawa Chemical (USA) Inc., of Chicago, Ill. Further details pertaining to
the build and support materials are found in U.S. patent application Ser. No. 09/971,247,
assigned to the assignee of the present invention.
Referring particularly to FIG. 1 there is illustrated generally by the
numeral
10 an to SDM apparatus incorporating a flash exposure system illustrated
generally by numeral
36. In this SDM apparatus, the flash exposure system
36 generates significant amounts of localized heat that is removed by the
flash cooling system and the ventilation and cooling system of the present invention
(not shown in FIG. 1). The SDM apparatus
10 is shown building a three-dimensional
object
44 on a support structure
46 in a build environment shown
generally by the numeral
12. The object
44 and support structure
46 are built in a layer by layer manner on a build platform
14 that
can be precisely positioned vertically by any conventional actuation means
16.
Directly above and parallel to the platform
14 is a rail system
18
on which a material dispensing trolley
20 resides carrying a dispensing
device
24. Preferably, the dispensing device
24 is the Z850 piezoelectric
ink jet print head that dispenses the build material and the support material.
However, other ink jet print head types could be used, such as an acoustic or electrostatic
type, if desired. Alternatively a thermal spray nozzle could be used instead of
an ink jet print head, if desired.
The trolley carrying the dispensing device
24 is fed the curable phase
change build material
22 from a remote reservoir
49. The remote reservoir
is provided with heaters
25 to bring and maintain the curable phase change
build material in a flowable state. Likewise, the trolley carrying the dispensing
device
24 is also fed the non-curable phase change support material
48
from remote reservoir
50 in the flowable state. In order to dispense the
materials, a heating means is provided to initially heat the materials to the flowable
state, and to maintain the materials in the flowable state along its path to the
print head. The heating means comprises heaters
25 on both reservoirs
49
and
50, and additional heaters (not shown) on the umbilicals
52 connecting
the reservoirs to the dispensing device
24. Located on the dispensing device
24 is a plurality of discharge orifices
27 for dispensing both the
build material and support material, although just one is shown in FIG. 1.
The dispensing device
24 is reciprocally driven on the rail system
18
along a horizontal path by a conventional drive means
26 such as an electric
motor. Generally, the trolley carrying the dispensing device
24 takes multiple
passes to dispense one complete layer of the materials from the discharge orifices
27. In FIG. 1, a portion of a layer
28 of dispensed build material
is shown as the trolley has just started its pass from left to right. Dispensed
droplets
30 are shown in mid-flight, and the distance between the discharge
orifice and the layer
28 of build material is greatly exaggerated for ease
of illustration. The layer
28 may be all build material, all support material,
or a combination of build and support material, as needed, in order to form and
support the three-dimensional object.
The initial layer thickness established during dispensing is greater than the
final layer thickness, and a planarizer
32 is drawn across the layer to
smooth the layer and normalize the layer to establish the final layer thickness.
The planarizer
32 is used to normalize the layers as needed in order to
eliminate the accumulated effects of drop volume variation, thermal distortion,
and the like, which occur during the build process. The planarizer
32 may
be mounted to the material dispensing trolley
20 if desired, or mounted
separately on the rail system
18, as shown.
A waste collection system (not shown in FIG. 1) is used to collect the excess
material
generated during planarizing. The waste collection system may comprise an umbilical
that delivers the material to a waste tank or waste cartridge, if desired. A preferred
waste system for curable phase change materials is disclosed in U.S. patent application
Ser. No. 09/970,956 assigned to the assignee of the present invention. The system
is discussed further in conjunction with FIG. 2.
Referring back to FIG. 1, an external computer
34 generates or is
provided with a solid modeling CAD data file containing three-dimensional coordinate
data of an object to be formed. Typically the computer
34 converts the data
of the object into surface representation data, most commonly into the STL file
format and also establishes support region data for the object. When a user desires
to build an object, a print command is executed at the external computer in which
the STL file is processed, through print client software, and sent to the computer
controller
40 of the SDM apparatus
10 as a print job. The processed
data transmitted to the computer controller
40 can be sent by any conventional
data transferable medium desired, such as by magnetic disk tape, microelectronic
memory, network connection, or the like. The is computer controller processes the
data and executes the signals that operate the apparatus to form the object. The
data transmission route and controls of the various components of the SDM apparatus
are represented as dashed lines at
42.
In FIG. 1, the flash exposure system
36 is mounted on rail system
18.
The flash exposure system
36 is reciprocally driven along rail system
18
to scan the radiation source over a just dispensed layer of material. The flash
exposure system
36 includes flash lamp
38, which is used to provide
a planar (flood) exposure of UV radiation to each layer as needed. The flash exposure
system
36 is discussed in greater detail in conjunction with FIG. 3.
Referring to FIG. 2 there is illustrated generally by the numeral
10
another SDM apparatus suited for incorporating the present invention ventilation
and cooling system (not shown). The apparatus
10 in FIG. 2 has the same
the flash exposure system
36 as the SDM apparatus
10 of FIG. 1. This
apparatus
10 is shown including schematically a material feed and waste
system illustrated generally by numeral
54. In contrast to the SDM apparatus
shown in FIG. 1, the build platform
14 in this apparatus is reciprocally
driven by the conventional drive means
26 instead of the dispensing trolley
20. The dispensing trolley
20 is precisely moved by actuation means
16 vertically to control the thickness of the layers of the object. Preferably,
the actuation means
16 comprises precision lead screw linear actuators driven
by servomotors. The ends of the linear actuators
16 reside on opposite ends
of the build environment
12 and in a transverse direction to the direction
of reciprocation of the build platform. However, for ease of illustration in FIG.
2 they are shown in a two-dimensionally flat manner giving the appearance that
the linear actuators are aligned in the direction of reciprocation of the build
platform
14. Although they may be aligned with the direction of reciprocation,
it is preferred they be situated in a transverse direction so as to optimize the
use of space within the apparatus.
In the build environment generally illustrated by numeral
12, there is
shown by numeral
44 a three-dimensional object being formed with integrally
formed supports
46. The curable phase change build material identified by
numeral
22 is dispensed by the apparatus
10 to form the three-dimensional
object
44, and the non-curable phase change material identified by numeral
48 is dispensed to form the support
46. Containers identified generally
by numerals
56A and
56B, respectively, hold a discrete amount of
these two materials
22 and
48. Umbilicals
58A and
58B,
respectively, deliver the material to the dispensing device
24. The materials
22 and
48 are heated to a flowable state, and heaters (not shown)
are provided on the umbilicals
58A and
58B to maintain the materials
in the flowable state as they are delivered to the dispensing device
24.
When the dispensing device
24 needs additional material
22 or
48,
extrusion bars
60A and
60B are respectively engaged to extrude the
material from the containers
56A and
56B, through the umbilicals
58A and
58B, and to the dispensing device
24.
The dispensing trolley
20 shown in FIG. 2 carries the heated planarizer
32 in contrast to the embodiment in FIG. 1. The planarizer
32 removes
the excess flowable material as the planarizer rotates, which brings the material
up to the skive
62 which is in contact with the planarizer
32. The
skive
62 separates the material from the surface of the planarizer
32
and directs the flowable material into a waste reservoir, identified generally
by numeral
64 located on the trolley
20. A heater
66 and thermistor
68 on the waste reservoir
64 operate to maintain the temperature
of the waste reservoir at a sufficient point so that the waste material in the
reservoir remains in the flowable state.
The waste reservoir is connected to a heated waste umbilical
70 for delivery
of the waste material to the waste receptacles
72A and
72B. For each
waste receptacle
72A and
72B, there is associated a solenoid valve
74A and
74B, for regulating the delivery of waste material
76
to the waste receptacles. A detailed discussion of the feed and waste system is
disclosed in U.S. patent application Ser. No. 09/970,956 assigned to the assignee
of the present invention.
In FIG. 2 an additional flash exposure system is generally shown by numeral
79
comprising a lamp
80. The flash exposure system
79 is provided separately
to expose the waste material in the waste receptacles to radiation in order to
cure the waste material in the waste receptacles. The flash exposure system
36
is shown comprising lamp
38 and chamber
122. It is to be appreciated
that these flash exposure systems,
36 and
79, generate heat, which
is removed by the ventilation and cooling system of the present invention.
Referring now to FIG. 3, an electrical schematic of the flash exposure
system
36 is shown that incorporates a flash cooling system generally identified
by numeral
112. Discussed in conjunction with FIG. 4, the flash cooling
system
112 is connected to the ventilation and cooling system of the present
invention. Referring back to FIG. 3, the flash exposure system
36 utilizes
a xenon flash lamp
38 which emits a large amount of spectral energy (radiation)
in short duration pulses. A DC power supply
92 provides direct current voltage
to both the pulse forming network
94 and the trigger
96. The power
supply
92 is provided with AC power and converts this to DC power for use
by the flash exposure system
36. The power supply
92 was produced
by Kaiser Systems, Inc., of Beverly, Mass. The pulse forming network
94
was produced by PerkinElmer Optoelectronics of Salem, Mass. Flashing of the xenon
lamp is initiated by the trigger
96, which creates a voltage gradient (Volts/inch)
in the xenon gas in the lamp that causes ionization. The trigger
96 is a
series induction trigger produced by PerkinElmer Optoelectronics under the designation
TR-204 series injection transformer. The xenon flash lamp
38 comprises a
thermally matched hollow quartz glass tube
102 and sealed electrode ends
104, which encapsulate the xenon gas in the lamp. Tungsten electrodes
100
reside in the glass tube
102 and are approximately 10 inches apart. The
lamp
38 is contained in chamber
122, which is configured to reduce
electro-magnetic irradiation and allow a cooling stream of air
146 to flow
across the lamp
38. The xenon flash lamp was produced by PerkinElmer Optoelectronics
for 3D Systems, Inc. as part number FXQG-1700-10. A detailed discussion of the
flash exposure system
36 is disclosed in U.S. patent application Ser. No.
10/140,426 entitled "Flash Curing in Selective Deposition Modeling."
In FIG. 3, the flash cooling system
112 for the flash exposure system
36
is provided air by the present invention ventilation and cooling system. Only a
few components of the ventilation and cooling system are shown in FIG. 3. Part
of the ventilation and cooling system comprises a air-moving device
114
having an air inlet
116 for receiving air and an air outlet
118 for
supplying the air to air duct
120. Air-moving device
114 provides
a first flow of air
108 that enters the SDM apparatus through air inlet
duct
150. The air-moving device
114 delivers the first flow of air
108 from outside the apparatus to air duct
120 and to other systems
in the apparatus if desired, as identified generally by numeral
148. The
air duct
120 is in communication with chamber
122, which makes outside
air available for cooling the lamp
38. It is preferred that the flash cooling
system
112 utilizes outside air to cool the lamp
38 instead of the
air inside the apparatus
10. This is because build material vapors may be
present in the air inside the apparatus, which if allowed to enter the chamber
122, would be cured in the chamber and eventually render the flash curing
system
36 inoperative. However, an activated charcoal filter could be used
as the filter to remove the vapors from the inside air prior to using the air to
cool the lamp
38, if desired, such as a filter utilizing the AQF® activated
media liners available from AQF Technologies, LLC, of Charlotte, N.C. Filters utilizing
the AQF® activated media liners are available from Filtration Group, Inc.,
of Jollet, Ill.
In the flash cooling system
112, the desired flow rate of air for cooling
the lamp
38 is established by the provision of a low-pressure zone at a
low-pressure port
126 that is connected to the chamber
122 via air
duct
124. It is the low-pressure zone, which draws air
146 at a desired
flow rate across the lamp
38 and through the chamber
122 to provide
steady state cooling of the lamp
38. The low-pressure zone is established
by providing at least one air-moving device
128 that creates a second flow
of air
131 that travels through a venturi duct
130 and out of the
apparatus. The air-moving device
128 and venturi duct
130 are also
part of the ventilation and cooling system of the present invention (shown generally
by numeral
134 in FIG. 4). Referring back to FIG. 3, the venturi duct
130
has an inlet end
140, an exit end
142, and a restriction chamber
or throat
144 wherein the low-pressure zone is established. For the SDM
apparatus
10 of FIG. 2, the desired ventilation air flow rate of the second
flow of air
131 is between about 80 CFM to about 300 CFM, and more preferably
between about 135 CFM to about 250 CFM. Further, the desired pressure drop at port
126 (compared to atmospheric pressure) is between about 1 to about 2.5 inches
of water (In H
2O). The flash cooling system
112 is discussed
in greater detail, including how to select an appropriate fan and venturi configuration,
in U.S. patent application Ser. No. 10/157,575, filed May 28, 2002 by Fong.
Referring now to FIG. 4, a first embodiment of the present invention ventilation
and cooling system is schematically shown and identified generally by numeral
134.
The ventilation and cooling system
134 is inside the selective deposition
modeling apparatus of which only the dispensing trolley
20 and build platform
14 are shown for ease of illustration. The selective deposition modeling
apparatus and ventilation and cooling system
134 is surrounded by containment
chamber
136. The ventilation and cooling system
134 is adapted to
ventilate and cool the SDM apparatuses discussed in conjunction with FIGS. 1 and
2. In FIG. 4, the flash cooling system
112 is shown as it is connected to
the ventilation and cooling system
134. Air-moving device
114 draws
the first flow of air
108 into air inlet
116 and to air duct
120.
Air duct
120 provides this air to chamber
122 for cooling the lamp
38 and to fans
78 on the dispensing trolley
20. Fans
78
and their associated air ducts
90 establish substantially uniform sheets
of air flow away from the dispensing device
24. These uniform sheets of
air flow, generally shown by numeral
98, remove heat from the layers of
three-dimensional objects as they are formed by the SDM apparatus. A detailed discussion
on establishing the uniform sheets of air flow are provided in U.S. patent application
Ser. No. 10/001,727 assigned to the assignee of the present invention.
The air duct
120 also provides air to the flash exposure system
79
through air passage
132 which is vented inside the apparatus within the
containment chamber
136. In addition, the uniform sheets of air flow
98
are also vented inside the apparatus. These three air flows absorb heat by convection
during the build process which, in addition to the heat generated from other heat
generating components, such as the power supply
92, computer controller
40, and drive means
26, raise the air temperature inside the apparatus.
This heated air rises, as indicated by numerals
138, and is drawn into the
venturi duct
130 and is combined with air flow
146 to establish the
second flow of air
131. The second flow of air
131 is expelled through
the exit end
142 of the venturi duct
130 by the air moving devices
128 and out of the containment chamber
136 through air exit duct
152, thereby expelling the heat generated by the apparatus.
The second flow of air
131 passes through filter
106 before exiting
the apparatus. Importantly, the filter
106 captures airborne contaminants
and prevents the contaminants from exiting the containment chamber and into the
local environment. Preferably the filter
106 is an activated charcoal filter
capable of capturing airborne contaminants at flow rates of between about 80 CFM
to about 300 CFM with a minimal pressure drop across the filter. The aforementioned
activated charcoal filters available from Filtration Group, Inc., of Jollet, Ill.
are preferred for this application.
Importantly, the ventilation and cooling system
134 is configured
so that the second flow of air
131 that exits the apparatus through the
containment chamber
136, exits at a flow rate that is greater than the flow
rate at which the first flow of air
108 enters the apparatus through containment
chamber
136. The containment chamber
136, which is comprised of removable
outer panels and hinged doors of the apparatus, is not air-tight. Since the second
flow of air
131 exiting the apparatus is greater than the first flow of
air
108 entering the apparatus through air inlet
116, the pressure
inside the containment chamber is below atmospheric pressure. This pressure difference
or drop assures that a third flow of air is established that enters the apparatus
by passing through all the unsealed gaps of the containment chamber
136,
as identified generally by numeral
110. A steady state condition is achieved
when the flow rate of the first flow of air
108, when combined with the
flow rate of the third flow of air
110 substantially equals the flow rate
of the second flow of air
131. This steady state condition establishes a
pressure drop in the apparatus that assures that all the air that passes into the
SDM apparatus will pass through filter
106, wherein substantially all airborne
contaminants are captured, making the SDM apparatus safe for use in an office environment.
When the steady state condition between the first, second, and third air flows
is established, typically within about 30 seconds after starting the ventilation
and cooling system, the pressure drop in the apparatus stabilizes and can be measured
with a vacuum pressure sensor. A pressure sensor (not shown) can be configured
to determine the pressure difference or drop in the apparatus, and when the pressure
difference falls below a desired value the sensor can signal the operator of the
SDM apparatus
10 that the ventilation and cooling system is not functioning
properly, or can shut down the apparatus, if desired. Generally the ventilation
and cooling system may not be functioning properly when the filter is blocked or
clogged, when there is a fan failure, when there is a power failure, and when there
is blockage to the air inlet or air exit ducts. Any one of these conditions will
reduce or eliminate the pressure drop inside the containment chamber. In the embodiments
herein, the pressure inside the so containment chamber when the steady state condition
is established should be between about 0.05 In H
2O to about 1.00 In
H
2O less than atmospheric pressure when the ventilation and cooling
system is functioning properly. Generally, if the pressure difference is less than
about 0.05 In H
2O, the ventilation and cooling system is not functioning
properly, in which case airborne contaminants may undesirably escape from the containment
chamber and into the local environment. This can be prevented by providing a pressure
sensor that determines this pressure difference and shuts down the SDM apparatus
when the determined pressure difference falls below about 0.05 In H
2O.
There are a wide variety of ways to configure a pressure sensor to determine this
pressure difference, of which one is discussed herein. Alternatively, the pressure
sensor may signal the apparatus, by activating a warning light and/or audible signal
from a speaker, to alert the operator that the ventilation and cooling system is
not functioning properly. In addition the pressure sensor can signal any combination
of a warning light, audible signal, or app
