Three-dimensional printer and method for fabricating a three-dimensional object

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DESCRIPTION

Three-dimensional printer and procedure for the manufacture of a three-dimensional object

Background

Rapid prototyping describes various techniques for making a three-dimensional prototype of an object from a computer model of the object. One technique is three-dimensional printing in which a special printer is used to manufacture the prototype from a plurality of two-dimensional layers. In particular, a digital representation of a 3-D object is stored in a computer memory. Computer software slices the representation of the object into a plurality of discrete 2-D layers. A 3-D printer then manufactures a layer of material for each layer sliced ​​by the software. Together, the various manufactured form the desired prototype.

An apparatus for building a three-dimensional part from powder typically includes a powder supply and a building surface. The powder is transferred from the powder supply to the building surface in incremental layers. In a three-dimensional printing process, layers of a powder material are deposited in a confined area. A binder solution is selectively deposited on each layer to produce areas of bonded powder: a typical apparatus for depositing the binder is an ink jet printhead. The non-agglutinated powder is then removed to obtain a three-dimensional part.

Document WO-A-95/34468 discloses an apparatus for manufacturing a three-dimensional object and a method for manufacturing a three-dimensional object exhibiting the distinctive features of the preamble of claims 1 and 10, respectively. The apparatus and method of the present invention are characterized by the distinctive features of the claiming parties to those claims. Optional distinctive features are developed in the dependent claims.

Summary

Using dust as a building material offers potential problems. Because dust can easily be airborne, it can adversely affect machinery, the end product, or users' people. Dust can be transported through the air during the various stages of the printing process: from loading the machine to cleaning. Also, build-up of excess dust, whether airborne or not, can lead to maintenance problems within the printer. Previous 3-D printers have had dust control problems.

The three-dimensional printer may include apparatus that may comprise a feed reservoir, a vacuum system, a build chamber, and an overflow cavity. The feed reservoir stores a supply of construction material to form the object. The building chamber receives the incremental layers of building material from the feed tank. The overflow cavity receives an excess amount of the building material transferred from the feed tank but not received by the building chamber.

The vacuum system can have its inlet communicated with the feed tank. The vacuum system can then be used to transfer construction material into the vacuum tank from various sources. More specifically, the vacuum system can be used to suck the building material into the supply tank through a conduit attached to the inlet of the vacuum system.

For example, the vacuum system can be configured to fill the feed tank from a building material container. This may also include a device for injecting air into the building material container. The vacuum system can also be configured to remove loose powder from the build chamber after the object has been manufactured and to transfer the loose powder to the hopper. The vacuum system can also be configured to empty the overflow cavity and transfer the building material to the feed tank. The vacuum system can also be configured to clean the dust deposited on or near the feed tank or the build chamber and return the cleaned powder to the feed tank. Any of the referenced examples can be automated or done by hand by the user.

The apparatus may also include a system for removing relatively large particles of powder and returning the powder to the feed tank. This system can induce a cyclonic action on a stream of dust and air flow. The flow stream can pass through a separator screen before entering the feed tank.

The apparatus also includes a filter disposed within the vacuum system and a cleaning mechanism for cleaning the filter. In the case of a plurality of filters, a cleaning mechanism can then be used to clean the filters. In particular, a reverse air flow can be supplied sequentially through each of the filters. In that case, the cleaning mechanism could include valves to close the vacuum source on

ES 2 387 299 T3 an outlet of a single filter to then divert the air at approximately atmospheric pressure into the same outlet, reversing the direction of flow and venting the accumulated particles. Other filters in the system can be used to maintain airflow and vacuum within the vacuum chamber while one or more of the filters are being cleaned by reverse airflow.

Not only is dust dissipation difficult to control, it can be difficult to transfer dust from the dust supply to the construction area. First, the powder becomes compacted in the powder supply and tends to agglutinate within structures, such as bridges. Second, it can be difficult to deposit the powder in a smooth layer, which can lead to part defects. Finally, too much dust can be transferred, causing waste and contributing to accumulation of excess dust and airborne dust.

The three-dimensional printer may include a chamber for storing the building material below the plane of the building surface and a conveyor, the conveyor may be coupled to the chamber and then used to move the building material. Also, the conveyor can stir construction material within the chamber in order to prevent the formation of construction material bridges or stagnant areas.

More specifically, the conveyor may include a plurality of slats attached to a length of a conveyor chain, each slat being sized to carry a quantity of construction material. The slats can be shaped to be rigid without increasing the volume of construction material that can be supplied by each slat. In particular, the slats can be shaped so that the moment created when they are drawn through the building volume tends to wrap the conveyor chain on a toothed pinion or on a pulley. Also, the slats may be shaped so that the moment created when the powder transport portion of the slat is pulled through the powder is eliminated by the moment created when the stiffener is pulled through the powder. The conveyor system can be configured to deposit the building material in front of a spreader roll or doctor blade, such as by aligning and orienting the die slats.

A measurement system can be used to regulate the amount of building material deposited. The conveyor system can be an endless screw within a tube or tubes. The worm can then be rotated to lift powder from the bottom of the hopper to the metering system.

The measurement system may comprise a cylinder within a tight fitting tube. In this embodiment, the cylinder can have a cavity to contain a specific volume of construction material and the tube can have an inlet slot and an outlet slot. The cylinder can then be rotated inside the tube so that the building material enters the cavity and is transported to the exit slot. More specifically, a clearance between the cylinder and the tube is dimensioned to restrict the flow of unwanted powder between the inlet slot and the outlet slot. Also, a fluctuating blade may be a rotating counter with the measuring cylinder so that the fluctuating blade scrapes the building material away from the cavity to prevent the building material from sticking therein.

Various mechanisms can be used to break the bridges and keep the building material flowing into the measurement system. For example, a paddle wheel can be configured to agitate the building material above the measuring system. In another example, a vibrating member can be used to agitate the building material and can be attached to the chamber.

The three-dimensional printer may include a chamber for storing the building material above the plane of the building surface and a measurement system. The metering system can be used to regulate the amount of construction material supplied by the feed tank.

In particular, the measurement may comprise a cylinder installed within a tight fitting tube. In this embodiment, the cylinder can have a cavity to contain a specific volume of construction material and the tube can have an entry slit and an exit slit. The cylinder can then be rotated within the tube so that the building material enters the cavity and is conveyed to the exit slot. More specifically, a clearance between the cylinder and the tube is dimensioned to restrict the flow of unwanted powder between the inlet slot and the outlet slot.

Various mechanisms can be used to break the bridges and keep the building material flowing into the measurement system. In another example, a vibrating member can be used to agitate the building material and can be attached to the chamber.

The camera and measurement system may be mounted on a gantry capable of moving through a building chamber. The powder can be measured over the build chamber to form a smooth layer. Specifically, the powder can be measured by a roller or a doctor blade to create the smooth layer.

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Once the three-dimensional part has been made through printing, it is surrounded by loose powder. That loose dust must be removed to expose the imposed pattern. Here again a technique is needed to mitigate the spread of loose dust. Because most of the powder can be loose, instead of joining it to form the part there is an economic incentive to recycle the loose powder.

The three-dimensional printer may include apparatus for removing loose powder from the surface of a three-dimensional printed object. A specific apparatus may include an enclosure to contain the object, a blower to create an airflow, at least one filter to remove dust from the airflow, a duct system to channel the airflow into the enclosure, and a tool for blowing compressed air on the object.

More specifically, the ducts can direct at least a portion of the blower exhaust down through the enclosure opening to prevent dust from being blown out of the booth. Also, the ducts may direct at least a portion of the blower exhaust down through the enclosure to eliminate stagnant air pockets and generate generalized airflow from the top to the bottom of the enclosure. The airflow can be divided between the air curtain and the generalized downward flow by diverting the airflow through a duct in which there is very little pressure drop.

Likewise, the enclosure can be a constitutive part of the 3-D printer and the removal of loose dust occurs within the enclosure that houses the 3-D printer. The apparatus can also include a back-pulse cleaner to remove filter dust and a chamber to receive the removed dust. The dust removed from the filter can be automatically recycled by an integral vacuum system.

Inkjet type print heads are used to supply binder to powder layers. Another problem with working with powder is that the powder tends to collect on the print heads. If dust is allowed to accumulate for a considerable period of time, it can clog the jet jets. Therefore, it is necessary to keep the print heads clean. Also, it is necessary to detect defective jets or print heads and compensate for the failure.

The three-dimensional printer may include a structural frame, a construction chamber supported by the frame and suitable to be filled with a construction material, a gantry mounted for movement through the construction chamber, a print head mounted on the gantry a print head cleaning element for cleaning the print head and a cleaning system for cleaning the print head cleaning element.

In particular, the cleaning system may include a supply of a cleaning fluid and a mechanism for immersing the print head cleaning element into the cleaning fluid. To enhance cleaning, the cleaning fluid can be agitated by ultrasonic vibration or by circulating the cleaning fluid with a pump. Also, air can be injected into the cleaning fluid to increase agitation.

Structurally, the print head cleaning element can be mounted on a removable strap. The cleaning system may also include a mechanism for drying the print head cleaning element across a fixed surface. The fixed surface can be moistened with the cleaning fluid. The fixed surface can be immersed in the cleaning fluid.

The three-dimensional printer may include a structural frame, a construction chamber supported by the frame and suitable to be filled with a construction material, a gantry mounted for movement through the construction chamber, a print head mounted on the gantry and a print head failure detector to detect if the print head is operating properly.

Various mechanisms can be used in the print head failure detector. For example the print head failure detector can be an optical drip detector. In another example, the printhead flaw detector may include a membrane onto which the drops are fired by the printhead, so that the drops can be detected by a microphone that detects the impact of the drops on the membrane. . As yet another example, the print head failure detector may include a piezoelectric element. Also, in any case, the print head failure detector can detect the firing of individual print head jets or a group of jets that are being fired simultaneously.

When the print head is a series of more than one print head, the drive mode of the printer can be altered in response to a detected failure of a print head. Specifically, the printing process can be modified so that more than one pass is made over each area of ​​the object being printed. This can make it possible for each area of ​​the object to be printed by more than one area of ​​the series of print heads.

When the print head is a series of 4 or more print heads, in which at least one print head is fed with a binder containing a colorant for each of the primaries, the drive mode of the printer can be altered in response to detected printhead failure. Of

ES 2 387 299 T3 specific mode, printing can be changed from a color mode to a multi-pass monochrome mode.

When the print head is a series of more than one print head, the drive mode of the printer can be altered in response to a detected failure of a print head on one end of the series. Specifically, the print pattern is modified so that the width of the print head series is redefined.

After the part is removed from the powder mass, it can be post-processed. One stage of the post-processing phase is infiltration. Infiltration involves the application of a resin to a porous part. Resins are typically adhesives that must be contained.

The three-dimensional printer may include apparatus for infiltration of a liquid into a three-dimensional printer part. The infiltration apparatus may include an enclosure to contain the part, a filtering system to remove infiltrating aerosols, and a sprayer to spray the infiltrant onto the part.

In particular, the enclosure can be disposable. A filter element can also be incorporated into the disposable enclosure.

The filter system may include a system for creating air flow through a filter element. The system for creating an air flow can be a booth and the envelope can be a disposable liner that prevents the booth from being coated with the infiltrant.

The sprayer can include a peristaltic pump, a disposable tube, and a disposable spray nozzle. The spray nozzle may be a siphon nozzle that creates an aerosol spray of the infiltrant. The peristaltic pump can be a double head pump and the infiltrant can be a two component material. The two components can be mixed in a mixing chamber before introducing the spray nozzle. Components can also be pumped through separate tubes at the same rate by the pump. The two-component material, in particular, can have a fixed mixing ratio and the inside diameters of the separate tubes can be fixed in the same ratio so that the mixing ratio is maintained.

It should be understood that the elements of the embodiments discussed above can be combined in various ways and are not exclusive to the embodiments described.

Brief description of the drawings

The exposed and other objectives, distinctive characteristics and advantages of the Three-Dimensional Printer will become apparent from the more specific subsequent description of specific embodiments of the invention, in accordance with what is illustrated in the accompanying drawings, in which the same reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, instead emphasis is placed on illustrating the principles of the invention.

Figure 1 is a schematic relationship of a particular apparatus for rapid prototyping formation.

Figure 2 is a perspective view of the 3D printer assembly.

Figure 3 is a perspective view of a concrete powder feeder.

Figure 4 is a perspective view of a powder charging subsystem.

Figure 5 is a schematic view of the 3-D printer assembly of Figure 2 with various parts removed to reveal the overflow chamber.

Figure 6 is a schematic view of another embodiment of the overflow chamber of Figure 5.

Figure 7 is a schematic view of a loose piece separator.

Figure 8 is a schematic view of a filter system for the vacuum system of Figure 3.

Figure 9 is a schematic view of a powder supply mechanism.

Figure 10 is a more detailed view of slat 123 at drop point 128.

Figure 11 is a perspective view of an embodiment of a simple slat.

Figure 12 is a perspective view of a particular embodiment of a reinforced slat.

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Figure 13 is a schematic view of a conveyor system of Figure 9 supplying powdered building material to a separate metering system.

Figures 14A-14B are schematic views of the measurement system of Figure 13.

Figure 15 is a schematic view of an embodiment in which the feed reservoir 102 is entirely above the plane of the building surface 202 and is integrated within a printer unit 200.

Figures 16A-16B are schematic views of a particular cleaning station 300.

Figure 17 is a schematic view of another specific embodiment of a cleaning station.

Figure 18 is a schematic view of a drip detector for monitoring the status of a printhead.

Figure 19 is a schematic view of a specific spray booth.

Figure 20 is a schematic cutaway view of the de-spraying booth of Figure 9.

Figure 21 is a schematic view of a particular diverter of Figure 20.

Figure 22 is a schematic view of a spray booth incorporated within the printer unit 200 of Figure 15.

Figure 23 is a schematic view of a liner for the spray booth of Figure 19.

Figure 24 is a schematic view of a system for applying a resin infiltrant by spraying.

Figure 25 is a schematic view of a system for spraying a two-component filter.

Figure 26 is a front cross-sectional view of a sealed piston.

Figure 27 is a schematic cross-section of a dust gutter.

Figure 28 is a schematic cross-sectional view of a magnetic vane configuration.

Figure 29 is a schematic view of a gravity feed binder supply.

Detailed description

Figure 1 is a schematic of a specific rapid prototyping apparatus. As illustrated, there is a digital module 1, a computer 10, a three-dimensional (3-D) printer assembly 30, a finished 3-D physical model printed (green), a post-processing system 50, and a completed 3-D physical model.

Digital model 1 is a data representation of an object that is to be printed in 3-D, that is, a digital object that is to be converted into a tangible physical entity. Appropriate digital models can be created using Computer Aided Design (CAD) software applications or 3 - D scanning systems, both available from many different vendors. Digital models are stored in standard industrial formats, which can be transmitted electronically and interpreted by application programs run on standard computer equipment.

Computer 10 can be a personal computer, such as a desktop computer or a laptop. The computer can be a stand-alone computer or a part of a network.

Computer 10 executes a custom software application program 15, which reads digital model files, accepts user input of parameters and references, performs a series of detailed calculations, and transmits to printer assembly 30 at 3 - D the information required to manufacture the desired physical model. In particular, the application program 15 allows the user to arrange one or more digital models within a virtual model that represents the effective manufacturing space within the printer 30 into 3-D. The application program 15 divides the set of models Digital in a plurality of two-dimensional (2D) layers, each with a predetermined thickness, which are transmitted to electronic control circuitry 32 housed within 3D printer 30.

The 3-D printer 30 uses a set of ink jet type print heads 35 to deposit a binder liquid 37 on successive layers of a powdered building material 39, as disclosed in US Patent 5,902,441 to Bredt. et al. where the binder liquid 37 combines with the pulverized building material 39, the powder reacts and hardens. By controlling the displacement of the binder droplets from these print heads, the solid 2-D cross-sectional structure can be physically reproduced. The 3-D printer manufactures a physical layer for each striped layer supplied

ES 2 387 299 T3 by application program 15. When the complete set of 2D cross-sections has been processed, a 3-D physical model has been formed. The model at this stage is designated "green" to indicate a finished printing state, prior to post-processing. Further details of the binding of a powder to form an object are disclosed in US Patent No. 5,340,656 to Sachs et al. and 5,387,380 to Cima et al.

The post-processing system 50 can be used to obtain the completed physical models 5 by improving the appearance and physical properties of the green physical models 3. The post-processing system 50 may optionally include a transport subsystem 52 to handle and transport the printed patterns, a drying subsystem 54 to completely dry the physical patterns, a dusting subsystem 56 to completely remove the pulverized building material. residual from the printed models, and an infiltration subsystem 58 to coat and infiltrate the printed models with various substances.

Figure 2 is a perspective view of the 3-D printer assembly of Figure 1. Its subassemblies constitute a powder feeder 100 and a printer unit 200. The powder feeder 100 and printer 200 can be easily decoupled from each other. to another for transportation, service and cleaning. Likewise, the user has the option of maintaining several interchangeable powder feeders 100 for use in a single printer unit 200, each feeder obtaining a different powder construction material to facilitate the convenient exchange of one material with another.

The description that follows describes a distinctive feature of the 3-D printer assembly 30. The headings are intended to serve as a guide to the reader and should not be construed as limiting the claimed invention.

Powder feeder

Figure 3 is a perspective view of a concrete powder feeder. The powder feeder 100 includes a vacuum subsystem 110 with an associated vacuum inlet 112, a feed reservoir 102, which stores a supply of the pulverized building material 39 (Figure 1), and a metering system 170 which supplies a construction material sprayed to the printer unit 200 in measured amounts. Subsequent paragraphs describe in detail the design and operation of the powder feeder 100 and its subassemblies.

Vacuum system

Charging powder can be a complicated and unpleasant process that can cause some of the powder to be blown out and allow the powder to settle on the printer, the user, and the surrounding environment. Similar problems exist with recycling powder that has not been printed. There are two types of recyclable dust: 1) dust that was deposited in the build chamber but was not used to make a part; and 2) the leftover powder used for the spreading process to ensure that a complete layer has been deposited; this excess powder ultimately falls into the overflow chamber. Both types of powder present the same recycling difficulties.

Figure 4 is a perspective view of a powder charging subsystem. The subsystem charges the feed tank 102 with the powdered building material 39. As in Figure 3, a vacuum system 110 is attached to the feed tank 102 (other embodiments could include a separate vacuum system). The vacuum system 110 constitutes the upper part of the powder feeder 100. The feed tank 102 is filled by drawing the pulverized building material from a transport container 9 into the feed tank through a flexible vacuum tube 111 coupled to the vacuum inlet 112. This allows the user to fill the tank without coming into contact with dust.

Likewise, air can be injected into the container 9 (which could be the container in which the powder is transported from its place of manufacture) through a flexible tube 101 of compressed air. The compressed air helps to empty the powder from the container making the powder flow more easily. This technique can be automated so that the feed tank 102 maintains a tank with a sufficient amount of construction material.

A vacuum system that incorporates an outlet that discharges into the 3 - D printer's feed reservoir solves many problems. By making the process cleaner, user satisfaction is increased and the machine becomes more reliable because less airborne dust is generated that can contaminate machine components (eg bearing and electronics). By making the process more comfortable (less time required and less interaction by the user), user satisfaction and productivity are increased.

Once a physical pattern has been formed by the 3-D printing process, it is necessary to separate the pattern from the unprinted powder (described below). Likewise, it is convenient to reuse the unprinted powder. To achieve these goals, the vacuum system 110 can be used to remove most of the dust from the printed pattern 3 (Figure 1).

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Likewise, when the user has removed the Model 3 from the printer, the user can use the vacuum system 110 to transport into the feeding tank 102 the rest of the powder in the feeding chamber and any amount of powder that has been deposited (by accident or on purpose) anywhere in the printer. In particular, in the process of printing a physical model, the 3-D printer 200 spreads successive layers of pulverized building material in the manner disclosed in US Patent No. 5,902,441 to Bredt et al., Depositing an amount per term. average about 20% of the total amount spread within an overflow chamber. Another specific use of the vacuum system 110 is to return the pulverized building material deposited in the overflow chamber into the feed chamber 102.

Figure 5 is a schematic figure of the 3-D printer assembly of Figure 2 from which various pieces have been removed to expose the overflow chamber 230. In the specific embodiment shown in Figure 5, the Overflow chamber 230 is connected via line 113 and valve 114 to vacuum inlet 112. When the vacuum system 110 is activated, the powdered building material from the overflow chamber 230 is activated into the conduit 113 and, from there, into the supply tank 102. An opening 115 is provided at valve 114 to allow a vacuum hose to be attached to perform the filling and cleaning functions described above. To use a flexible vacuum tube connected to port 115, valve 114 is adjusted to block the connection through line 113 to overflow chamber 230 and open the port 115 connection.

Figure 6 is a schematic view of another overflow chamber arrangement of Figure 5. As shown, overflow chamber 230 has an overflow chamber outlet 235 permanently attached at its lower end. To empty the overflow chamber 230, the user attaches a flexible vacuum tube at one end of the overflow chamber outlet 235 and at the other end to the vacuum chamber 112 of the vacuum system 110 (Figure 3). The vacuum system 110 is then activated, and the pulverized building material is transported from the overflow chamber 230 to the feed tank 102.

If the inlet 112 of the vacuum system 110 is directly connected to the feed tank 102, foreign matter can enter the feed tank. If the foreign matter is similar in size to the pulverized building material (e.g. powder), the foreign matter may not have any detectable effect in the 3-D printer or 3-D printing process. If large particles or pieces enter the feed tank, however, these pieces can damage the mechanism or, if they pass through the feed tank and are deposited in the build chamber, they can damage the physical model that is being printed.

Figure 7 is a schematic view of a loose piece separator. As shown the chunk separator 120 is located between the vacuum system inlet 112 and the feed reservoir 102. The separator 120 causes air, pulverized building material and any foreign material to enter the inlet 112 to follow a generally circular air flow path 122 around the interior of the device. The pulverized building material and air pass up through the separator screen 125 leaving the separator 120, and entering the feed tank 102. Any material entrained in the air flow 122 that is too large to pass through the screen 125 continues to circulate around the interior of the device. This recirculating action tends to break up and wear away any foreign matter allowing some of this matter to ultimately pass through screen 125. A front plate 127 of separator 120 can be removed to provide a removal access hole for accumulated waste.

Figure 8 is a schematic view of a filter system for the vacuum system of Figure 3. As shown, the vacuum system 110 includes two filters 118-A, 118-B located within the feed tank 102 to prevent fine particles (such as pulverized building material) that are picked up by the vacuum system 110 from being expelled into the room. The person skilled in the art will realize that the filters will be coated with pulverized construction material and that this coating will emit the air flow through the filter reducing the pressure differential generated at the vacuum inlet 112. The filter system is used for cleaning. The filters.

A 119-A, 119-B valve system closes the vacuum source to a single filter outlet and diverts air at or near atmospheric pressure into the same outlet, reversing the flow direction and venting the dust. accumulated, which then falls into the feed tank 102. The other filter in the system maintains air flow and vacuum within the feed tank 102 to induce this air flow. This purge cycle is periodically repeated through each filter element. In this way the filters can be cleaned without user intervention and without requiring the user to stop using the vacuum system while the filters are automatically cleaned.

Powder feed

The main function of the powder feeder 100 is to supply powdered building material to the 3-D printer unit 200 in metered quantities as required by the printing process.

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Figure 9 is a schematic view of a powder supply mechanism. The supply tank 102 has in particular a volumetric capacity of approximately 0.24 cm³ or enough powdered building material to print 1.75 of the largest possible physical patterns within the printer unit 200. The powder supply mechanism 120 includes a conveyor 122 incorporating slats 123 attached to two lengths of the conveyor chain. The conveyor is driven by an electric motor and travels in a recirculating manner in the direction indicated by the arrows. The slats 123 pass through the pulverized building material 39 in the feed tank 102, and each slat 123 conducts part of the pulverized building material 39 to a point above the plane of the building surface 202. As slats 123 pass over a drive sprocket 125 they are inverted at a dropping point 128, and the sprayed building material is poured onto building surface 202 in position to be spread over the surface of the physical pattern that is being printed. Figure 10 is a more detailed view of slat 123 at drop point 128. The system shown in Figure 9 has the added advantage that the slats are continuously moving along the periphery of the hopper 102. In doing so, the movement of the slats 123 agitates the volume of powder and prevents bridging. or stagnant dust areas. It is desirable to avoid stagnant areas because dust in these areas cannot be removed from the hopper by the conveyor system 122. Said stagnant areas represent discarded dust because said dust cannot be used during normal operation of the feed conveyor.

For a bin with a large amount of powder, the force applied to slats 123 that are pulled through the bin by conveyor 122 can be very large. The geometry of the slats can be altered to stiffen them sufficiently to enable it to travel through the pulverized building material without being permanently deformed.

Figure 11 is a perspective view of a single slat arrangement. The slat 123 includes a foot 124 and is connected to the two conveyor chains 122-A, 122-B. This batten provides an optimal volume of sprayed building material but may be too weak to support the loads applied to it. The foot can be reinforced to obtain greater rigidity.

Figure 12 is a perspective view of a specific arrangement of a reinforced slat. The batten 123 itself includes an additional stiffening member 126 that adds strength to the member, without increasing the amount of sprayed building material it supplies. The powder is driven onto the surface 123-S of the strip 123. This configuration presents an additional window in the sense that the moment created by the resistance of the dust wraps the chain 122-A, 122-B on its pulleys or sprockets. A moment in the opposite direction tends to cause the chain to bind and not slide around the pulley or sprocket.

Dust measurement

Figure 13 is a schematic view of a conveyor system of Figure 9 supplying the pulverized building material to a separate metering system. The metering system 130 regulates the flow of sprayed building material into the 3-D printer.

Figures 14A-14B are schematic views of the metering system of Figure 13. Referring to Figure 14A, a cylindrical metering roll 133 is enclosed by a tight fitting tube 134. The metering roller 133 has four auxiliary grooves on its surface, which constitute the metering cavities 135-A, 135-B, 135-C and 135-D. Tube 134 has an inlet slot 136 and an outlet slot 137. As the metering roll 133 rotates within the tube 134, the pulverized building material enters a metering cavity 135-A through the entry slit 136. As the metering roll 133 continues to rotate, the pulverized building material it is captured between the metering roll 133 and the tube 134 and is driven rotating to the exit slot 137, where it is discharged onto the building surface 202 (Figure 13).

The clearance between the measuring roller 133 and the tube 134 is approximately 0.038 cm, which has been determined to be wide enough to allow the measuring roller 133 to rotate freely but small enough to prevent unwanted radial flow. of powder between inlet slit 136 and outlet slit 137. Measurement cavities 135 each contain approximately 49 cm³ of pulverized building material, which is equal to the material required for the smallest desirable increase in layer thickness. This enables a quantity of pulverized building material to be supplied consistent with any desired layer thickness by causing the metering roll 133 to rotate until the associated number of metering cavities 135 have picked up and supplied pulverized building material.

Also, a paddle wheel agitator 138 is shown, which stirs the sprayed building material above the metering roll 133 to break the bridges and keep the sprayed building material flowing into the metering cavity 135.

An oscillating blade 139 rotates in the opposite direction of the metering roller 133. When a metering cavity 135 containing pulverized building material enters the exit slot 137, the oscillating blade 139

ES 2 387 299 T3 sweeps the powdered building material out of the metering cavity 135. This technique prevents variation in the amount of the sprayed building material supplied, even when the materials are sticky or have a tendency to form bridges.

Figure 15 is a schematic view of an arrangement in which the feed reservoir 102 is entirely above the plane of the building surface 102 and integrated within a printer unit 200 '. The powder is metered according to the hopper 202 on the plane of the building surface 202 and spread over a building box 220 via the gantry 210. The powder is then printed by a print head or a set 205 of print heads. In this embodiment, the metering system could be located at the bottom of the feed tank and powered by the force of gravity. In other arrangements, the metering system could be located at the bottom of the feed bin and the bin would include a paddle wheel or vibrating mechanisms to ensure the entry of the powder flow into the metering system if the powder is of a type prone to caking or caving.

Although the powder can be supplied on one side of the build chamber and then spread through the build chamber by a roller, the feed reservoir can be connected on the gantry 210, which is capable of moving through the build chamber. The powder could be measured against the feed tank and deposited directly onto the build chamber 220 as the gantry moved through it. In such an embodiment, a roller or doctor blade could be used to smooth and level the surface after the feed tank has passed over it.

Print head

Cleaning the print heads

The 3-D printer unit 200 uses a set of inkjet print heads to selectively distribute a binder material over successive layers of powdered building material, selectively hardening the building material and forming typical patterns in 3-D. This technique is disclosed in detail in, for example, US Patent No. 5,902,441 to Bredt et al. One aspect of a successful ink jet recording device is a technique for keeping the face of the print head clean. Keeping print heads clean in a 3-D printing environment is particularly demanding due to the high concentration of airborne sprayed building material in the immediate vicinity of the face of the print heads. For most ink jet printers, the face of the print heads is routinely cleaned with a cleaning element in the form of a rubber broom.

Figures 16A-16B are schematic views of a particular cleaning station 300. As shown a cleaning element 305 is positioned to clean the face of a print head 205 as the print head travels over the cleaner 305 in the direction to the left indicated by the arrow. As the print head 205 passes over the cleaning element 305, the contaminating material is transferred from the face of the print head 205 to the cleaning element 305. This procedure works satisfactorily as long as the contaminating material is not allowed to accumulate on the surface. the cleaning element.

As shown, the cleaning element 305 is mounted on a belt 302. The belt 302 runs on pulleys 304-A, 304-B, which can be rotated by a motor 306. The cleaning element 305 is fixed in position to clean the face of the print head 205. As shown in Figure 16-B, the motor 306 has been activated, causing the cleaning element 305 to be dragged onto the cleaning surface 308 of a cleaning block 309 in the direction indicated by the arrow, transferring any accumulated contamination to the wiper block 309. The wiper block 309 is periodically replaced to maintain a clean cleaning surface.

Figure 17 is a schematic view of another specific arrangement of a cleaning station. In this cleaning station 300 ', a cleaning element 305 can be retracted to clean inside the recessed cleaning station 300', which is filled to a level 308 'with a cleaning fluid 309'. When the cleaning element 305 'is retracted, it is completely immersed in the cleaning fluid 309'. An agitator 307 can agitate the fluid 309 'by various means, such as ultrasonic vibration, rapid circulation of the cleaning fluid; or injection of air bubbles.

Print Head Failure Detection

The lifespan of a print head varies depending on usage and other variables that may not be controlled. Sometimes the print heads are partially damaged, so that some jets do not fire while others continue to fire normally. Other times, an entire print head fails, all of its jets malfunctioning. Because there is great variation in the way print heads fail and in the overall life of a print head, and because the failure of a print head can cause the 3-D printer to fail. to fabricate the desired physical model, it is helpful

ES 2 387 299 T3 to be able to detect the state of the print head and to be able to determine whether some, or most or all of its jets are firing.

Figure 18 is a schematic view of a drip detector for monitoring the status of a print head. After the print head 205 is moved to its position above the drip detector 400, each assortment of the print head 205 is independently fired a sufficient number of times for the detector to positively detect whether the assortment is firing. usually. In an alternative embodiment, a group of jets is firing simultaneously, and the detector determines how many jets within each group it is firing normally without determining which specific jets are malfunctioning. This procedure is faster because several jets can be tested at the same time.

A particular drip detector 400 can be operated by optical means. For example, an emitter can emit a frequency of light at which the binder is opaque (infrared, for example). The light beam is interrupted when a drop shot by the print head passes through the beam. Failure to detect the interruption indicates a malfunctioning dispenser. If the detection beam is narrow enough, misdirected jets can also be detected.

Another particular drip detector 400 works by detecting drip impacts on a membrane attached to a microphone or piezoelectric detector.

Print Head Failure Compensation Strategies

The power to detect if each of the print heads is working properly makes it possible to design different operating modes of the 3-D printer. In the simplest mode of operation, the print job is interrupted as soon as possible. as correct operation is detected. The user can count on a short period of time to replace the defective print head or else the job is stopped. Alternatively, the print job can be stopped in any case. This would save time and reduce the amount of powder consumed. Without a drip detector, if the print head fails partially, or if a print head of a multi-print head printer fails partially or completely, a large amount of dust could be printed even though the resulting part would not be useful. . By stopping the print job when a defect is detected, the user saves the expense of binder and powder that would be wasted if the defect were not detected.

In another mode of operation, if it is determined that some assortments are not working but others are still working (as, for example, if one print head in a set of multiple print heads fails), the printing process is modified so that more than one pass is made over each area of ​​the part. By advancing the x-axis, 1 / n of the normal distance of each pass of the print heads on the Y-axis, each area will be printed by n different jets. The volume of the binder printed in each pass would be reduced to 1 / n the normal amount. N can be selected so that weak areas of the part (which are printed by n-1 operating jets) are still strong enough to provide a satisfactory part.

In yet another mode of operation, if a print head at one end or the other of a set of multiple print heads fails, the width of the set is redefined (such as having n - 1 print heads where n - 1 is the normal complement print heads) and the print job may be completed.

A 3-D color printer having 4 or more print heads in which at least one print head is binder fed with a colorant of the primary colors (cyan, purplish and yellow) is possible another way of printing. functioning. In particular, if the detector determines that one of the print heads has failed, the job is completed in a monochrome mode (or, to improve speed, a mode that uses all colors except the color of the faulty print head) using the overlay print mode mentioned above. In this way, the user can get a useful part but not a colored part or, alternatively, a part that has color but is not colored for the design.

Post-processing

Pulverization

Once a physical model has been printed and most of the non-printed, pulverized building material has been removed, for example by using the vacuum system 110 shown in Figure 3, it is convenient now to remove the rest of the building material. sprayed not printed. Due to adhesion between the sprayed non-printed building material and the physical non-printed pattern, it is generally not possible to remove all the sprayed non-printed building material solely by the vacuum system 110. The rest of the sprayed building material can be removed. with a brush, but this can be cumbersome or impossible with certain settings and can damage a delicate physical model. A specific procedure for removing excess pulverized building material from a physical model is to remove it by air blowing

ES 2 387 299 T3 compressed. However, this creates a number of problems by creating an airborne cloud of pulverized building material.

Figure 19 is a schematic view of a spray booth. An air flow is created within the dusting booth 500 to contain and direct the cloud of sprayed building material created by a jet of compressed air directed toward a physical model. An opening 503 provides access to the interior of the spray booth 500. The physical pattern to be sprayed remains on a surface 504 located within the opening 503. A window 505 can be closed to help contain airborne sprayed building material, and can be opened to allow a large physical model to be placed within the spray booth 500. A cover 506 covers a blower 510 to attenuate the noise generated by the operation of the equipment.

Figure 20 is a schematic cutaway view of the de-spraying booth of Figure 18. Air is circulated through the de-spraying booth 500 by blower 510, which is powered by an electric motor 515. As indicated by the arrows, the air exits from the blower 510 into a deflector 530, where the flow is divided into two separate streams, a primary flow 517 from an air curtain carried by a duct 518 of the air curtain. air, and a secondary dust clearance flow 519. Both flows are recombined in the vicinity of the physical model 3 supported on a rotating table 520, dragging the pulverized construction material. The flow then passes through openings in support surfaces 522 and through filters 524. The filtered air exits filters 524 into a clean air chamber 526 and, from there, enters the chamber. 510 blower opening to complete your circuit.

As the air carrying the pulverized construction material passes through the filters 524, the pulverized construction material collects on the surfaces of the filters 524, ultimately restricting air flow and reducing the efficiency of the system. To maintain the filters 524 in an unobstructed state, a pulse of air is periodically introduced into the filters 524 from the clean air chamber 526. This causes the airflow through filters 524 to reverse momentarily, forcing accumulated pulverized building material to separate from the surfaces of filters 524 and fall into a drawer 528. Dust collection drawer 528 may be withdrawn to be emptied.

One objective is to prevent airborne pulverized building material from escaping from the opening 503 of the de-spraying booth 500 (Figure 19), thereby contaminating the surrounding environment. In particular, when a high velocity jet of compressed air is directed onto the physical pattern 3, a substantial portion of the compressed air reflected by the physical pattern can be directed out of the spray booth 500 towards the user. To prevent the escape of this airborne, pulverized building material, the primary flow 517 from the air curtain (Figure 20) is directed vertically down the face of the window 505 (Figure 19), effectively capturing and deflecting toward out the directed current.

If all the exhaust from the blower were channeled to flow along the face of the booth 500, a very effective air curtain would be created. In that case, however, most of the air in the booth would become stagnant and an air zone would form that would slowly rotate inside the spray booth 500. When the pulverized building material is blown out of the physical model 3, the slowly rotating air would quickly become opaque due to the dust particles suspended in it. This cloud of opaque dust would take time to dissipate, reducing user productivity. The secondary dust clearance flow 519, shown in Figure 20, addresses this problem by creating a general downward flow through the booth so that no amount of dust is stagnant and any dust clouds that are produced are will dissipate quickly.

The optimal balance between the primary flow 517 of the air curtain and the secondary flow of air clearance 519 varies somewhat with the characteristics of the pulverized building material being removed and with the configuration of the physical pattern that is being de-pulverized. For this reason, the deflector 530 is adjustable.

Figure 21 is a schematic view of a particular deflector of Figure 20. Using a user-operated lever 532, a mechanical linkage 533 causes a deflection vane 534 to rotate up and down as indicated by the arrows. of a pivot point 535. As the edge 536 of the deflection vane 534 moves downward, the primary flow 517 of the air curtain down the duct 518 of the air curtain collects a greater portion of the total air flow. As the edge 536 of the deflection vane 534 moves upward, the secondary air clearance flow 519 into the exhaust chamber 538 collects more of the total air flow.

Figure 22 is a schematic view of a spray booth incorporated within the printer unit 200 'of Figure 15. As shown, a blower 510 is coupled to the spray booth 500. Air flows down through from the front opening of the booth 500, it draws the dust, passes through the filters (not shown) and returns to the inlet of the blower 510. In this configuration the de-spraying can be carried out with the same equipment as the printing.

The de-spraying booth 500 is separated from the printer unit 200 ', a cart can be used to transfer large or heavy physical models to the de-spraying booth 500. The physical models are

ES 2 387 299 T3 printed on a pallet is placed on a build board of the 3-D printer before printing begins. When printing is complete, the cart is positioned adjacent to the printer unit 200 'and the free space between them is bridged by a set of transfer rails. These rails carry a multiplicity of rollers, which allow the pallet, which supports the printed physical model, to slide smoothly on the wagon. The cart is then positioned adjacent to the de-spraying booth 500, and the transfer rails are used to slide the pallet, which supports the printed physical pattern, into the de-spraying booth 500.

Infiltration

The physical patterns created by the 3-D printing process are porous, which makes it possible to modify their properties by infiltration with various resins. The resin can be applied to the physical model in many ways including dipping, brushing or pouring. Each of these procedures is time-consuming, resin-wasting, or both. The present invention applies resin to the physical model through a spraying process. Many of the infiltrants used in 3 - D models are adhesive. Adhesive spraying creates a number of problems. First, it is necessary to contain any vapor created during the process (such as due to overspray, or kickback from the atomized sprayer). If the vapors are not contained, they can be deposited on the user, on the user's clothing or on other objects. With respect to certain infiltrants, the vapors may pose a danger to health or the environment. Another problem with spray adhesives is that the spray equipment becomes coated with the adhesive and must be cleaned thoroughly after each use. This is cumbersome and can create health or environmental problems if the solvent in the adhesive is hazardous.

Figure 23 is a schematic view of a liner for the de-spraying booth of Figure 19. A liner 560 protects the booth 500 from excessive spraying with infiltrant. The liner 560 includes a pre-filter 562 to capture airborne adhesive droplets to prevent coating the filters 524 (Figure 20) within the spray booth 500. When a physical pattern has been de-sprayed in the de-spraying booth 500, the user unfolds the liner 560, which is preferably made of corrugated cardboard, into the de-spraying booth 560 and sprays the infiltrant onto the physical pattern. Alternatively, the liner can be used to protect a vent hood or a ductless fume hood.

Figure 24 is a schematic view of a system for applying a resin infiltrant by spraying. In system 600, resin is pumped through disposable tube 604 from infiltrant reservoir 602 by peristaltic pump 603, and is then propelled through disposable spray nozzle 605. By using a system of disposable components and a peristaltic pump, which is not wetted by the adhesive, an inexpensive and easy-to-operate system for spraying adhesives is created. Cleaning consists of removing the tube and the spray nozzle.

Figure 25 is a schematic view of a system for spraying a two-component infiltrant. A two-component infiltrant is an infiltrator that solidifies when the two components are combined. In system 610 the resin components are pumped through disposable tube 614 from infiltrant reservoirs 616, 617 by a 2-head peristaltic pump 618. The two resin components are combined in a static mixer 619 and the mixture is then propelled through a disposable spray nozzle 615. The mixing ratio of the two component system can be maintained by using an appropriate diameter for each tube. In particular, a one-to-one relationship for the components requires that both tubes have the same diameter.

Dust control

Watertight seal of the pistons

It is important to seal the construction and the feed pistons so that loose powder does not leak out the sides and fall under the machine, which can cause an unwanted disorder and potentially damage the mechanisms arranged at the bottom. .

Figure 26 is a front cross-sectional view of a hermetically sealed piston. As shown, an energized tube 712 pushes outward on a felt 714 disposed on the interior surface of a piston case 710. The tube 712 is surrounded by the piston mounting plate 715 of the piston mounting 718 disposed on its top and side. The felt 714 is positioned between the sealed tube 712 and the side of the piston case 710 to form a seal.

Dust spout

3-D printing includes a supply drawer, from which the powder is fed, and a build drawer where part fabrication takes place. During the 3-D printing process, dust collects around these dust drawers on a surface (called a platform) until the dust can

ES 2 387 299 T3 be aspirated. Dust that migrates during the printing process can be a nuisance and can cause performance problems for 3-D printer parts, particularly the print head and service station. For functional reasons, the print head and the service station must be located in the plane of the upper edges of the powder drawers. If the deck is coplanar with these top edges, any dust accumulating on the deck is potentially close to these sensitive components. Accordingly, a more convenient arrangement incorporates the surface of the platform below the edges of the powder drawers, forming a gutter for the powder to fall into.

Figure 27 is a cross-sectional view of a powder drawer. The printer platform 802 is located below the upper edges 804t of the powder drawers. This configuration forms a gutter 805 where migrated dust can be collected.

Palettes

Paddles can prevent dust from migrating as it flows down the sides of the piston housings. One procedure is to use the pallets that are fixed to the gantry with springs, causing the pallets to exert a downward force on the upper platform of the 3-D printer. A specific printer includes a palette with a small magnet inside to exert a force. This allows for easier mounting and dismounting than the paddle with a spring. A further improvement involves the location of the paddles.

Figure 28 is a schematic cross-sectional view of a magnetic paddle configuration. The pallets 810-1 and 810-2 are fixed to the printer gantry 210 'in such a way that they are free to move perpendicular to the walls 804-1 and 804-2 of the powder drawers but they are fixed in such a way. effective relative to gantry 210 'in all other dimensions. Walls 804-1 and 804-2 are constructed of a soft magnetic material, such as steel. Each paddle features an embedded magnet 810-1 and 810-2 that acts on its respective wall with enough force to keep the paddle in intimate contact with the wall, forming a barrier to prevent dust 39 from spilling onto the pad 802 during a powder spreading operation.

Binder supply

Gravity Feed Binder Supply

3-D printing typically uses commercially available print heads that were designed for 2-D printing. A special binder material that conforms to the powder being printed is replaced by the ink normally distributed by the print head. . Since the atypical 3-D printed part requires much more binder than can be contained within a print head, and since print heads cannot practically be replaced while a part is being built, it is necessary to proceed to continuous filling of binder in the print head while the printer is running. This is typically accomplished by making a tubing connection between the moving print head and a fixed supply of binder.

For a print head to function properly, the pressure inside the head at the inlet of the ink jet channels must be kept at a small negative pressure, typically at a pressure between -0.76 and -1.5 x 10³ Pa. A prior art employs an ink supply whose free surface is maintained at a level of approximately 10 cm below the outlet of the print head. Print heads are available with built-in pressure regulators that maintain the required internal negative pressure while the feed line pressure to the print heads varies over a wide range of positive pressures. In general, sufficient pressure must be exerted on the binder at the supply end of the binder feed line to cause the binder to flow through the tube at a sufficient rate to keep the print head full. The required pressure basically depends on the restrictive characteristics of the feed pipe and the relative height of the supply with respect to the print head. A prior art employs a pump that maintains the supply pressure at the inlet to the print head. Due to its complexity, this solution is expensive and potentially unreliable.

Figure 29 is a schematic view of a gravity feed binder supply. As shown, a fixed supply of binder 1002 is connected to printhead 205 through an extension of tubing 1004. In particular, the free surface of the binder can vary between 8.9 and 12.7 cm per above the bottom surface of the print head. This height provides sufficient pressure to feed the binder to the print head at a higher than required rate of 8 grams / minute through a pipe segment having an inside diameter of 1.5 mm and a length of approximately 1 , 8 m. Those skilled in the art will realize that other head and pipe combinations could be selected to obtain the required flow rate.

ES 2 387 299 T3

Although the present Three-Dimensional Printer has been specifically shown and described with reference to specific embodiments, it should be understood by the person skilled in the art that various changes in shape and detail can be made without departing from the scope of the invention that is stated. claimed in the appended claims.