Patent Grant
7008206
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.
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.
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:
To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common in the figures.
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
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
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
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
Referring back to
In
Referring to
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
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
Referring now to
In
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
Referring now to
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 H2O to about 1.00 In H2O 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 H2O, 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 H2O. 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 apparatus shut down, if desired.
It is also desirable to determine when the filter 106 needs replacement. Preferably some detection system can either shut down the SDM apparatus or signal to the operator to replace the filter when the filter needs replacement. The detection system can signal any combination of a warning light, audible signal, or apparatus shut down, if desired. Generally, the filter 106 needs to be replaced when the activated charcoal within the filter becomes saturated with airborne contaminants, and particularly when it becomes saturated with organic components such as vaporized build material. If a filter 106 is saturated with contaminants, the effectiveness of the ventilation and cooling system 134 will decrease and may no longer capture additional contaminants. In these circumstances the additional contaminants could be exhausted into the office environment, which is to be avoided.
The condition of a saturated filter can be detected with vacuum pressure sensor 154, which is connected to the venturi duct 130 at the restriction chamber 144 on one end, and to the dispensing device 24 at the other. The pressure sensor 154 is primarily used to maintain a vacuum on the material in the dispensing device 24 by providing a signal that is used by vacuum pressure regulator 156 which maintains the vacuum.
This vacuum (about 5.5 In H2O ) is needed because the preferred print head was not designed to dispense material vertically downward as it is configured in the SDM apparatuses 10 in
When the ventilation and cooling system is functioning properly the pressure in the restriction chamber 144 will always be lower than the pressure in the dispensing device 24. When the filter 106 becomes saturated with contaminants and needs to be replaced, the restriction in the filter causes the flow rate of the second flow of air 131 to decrease, which raises the pressure at the restriction chamber and reduces the pressure difference measured by the pressure sensor 154. Once the pressure sensor determines a pressure difference that is less than a minimum allowable pressure difference between the restriction chamber 144 and dispensing device 24, the sensor can either shut down the SDM apparatus or provide some feedback or warning signal. The warning signal may be a light or audible signal, if desired, which notifies the operator that the filter needs to be replaced. The minimum allowable pressure difference is sensitive to a multiplicity of variables and conditions, and it is best determined from empirical data taken from testing conducted on the final configuration of the ventilation and cooling system. For example, with a completed ventilation and cooling system, a pressure difference can be measured with a new filter, and another measurement made with a completely saturated filter and from the two measurements the point at which the pressure difference indicates that the filter needs to be replaced can be determined.
It is to be appreciated that the pressure sensor 154, as configured in
The ventilation and cooling system 134 shown in
Now referring to
In
Referring now to
Referring now to
Now referring to
All patents and other publications cited herein are incorporated by reference in their entirety. What has been described are preferred embodiments in which modifications and changes may be made without departing from the spirit and scope of the accompanying claims.
| Number | Name | Date | Kind |
|---|---|---|---|
| 4634368 | Diaz | Jan 1987 | A |
| 4934920 | Yamauchi et al. | Jun 1990 | A |
| 5136515 | Helinski | Aug 1992 | A |
| 5204055 | Sachs et al. | Apr 1993 | A |
| 5216616 | Masters | Jun 1993 | A |
| 5312297 | Dieckert et al. | May 1994 | A |
| 5340433 | Crump | Aug 1994 | A |
| 5534309 | Liu | Jul 1996 | A |
| 5555176 | Menhennett et al. | Sep 1996 | A |
| 5704955 | Giles | Jan 1998 | A |
| 5717572 | Smith et al. | Feb 1998 | A |
| 5855836 | Leyden et al. | Jan 1999 | A |
| 5866058 | Batchelder et al. | Feb 1999 | A |
| 5904889 | Serbin et al. | May 1999 | A |
| 6133355 | Leyden et al. | Oct 2000 | A |
| 6198628 | Smith | Mar 2001 | B1 |
| 6259962 | Gothait | Jul 2001 | B1 |
| 20020016386 | Napadensky | Feb 2002 | A1 |
| Number | Date | Country |
|---|---|---|
| 9711837 | Apr 1997 | WO |
| 0011092 | Mar 2000 | WO |
| 0126023 | Apr 2001 | WO |
| 0168375 | Sep 2001 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 20030235635 A1 | Dec 2003 | US |
