BACKGROUND

[0001] Three-dimensional (3D) printing systems, also referred to as additive manufacturing systems, facilitate the generation of (3D) objects on a layer-by-layer basis. Such 3D printing techniques may generate each layer of an object by delivering and spreading build material across a build volume and selectively solidifying portions of the layer.

BRIEF DESCRIPTION OF THE DRAWINGS

[0002] Figure 1 is a sectional view schematically illustrating portions of an example 3D printing system build material particulate transport system having a multi-bend segment.

[0003] Figure 2 is a sectional view illustrating the example 3D printing system build material particulate transport system of figure 1 without the multi bend segment.

[0004] Figure 3 is a graph illustrating erosion and abrasive wear of the system of Figure 1 as compared to erosion and abrasive wear of the system of Figure 2 over time.

[0005] Figure 4 is a sectional view of a portion of a conduit of the system of Figure 1 following a period of use.

[0006] Figure 5 is a sectional view of the portion of Figure 4 in the system of Figure 2 following the period of use, Figure 5 illustrating an example of erosion of the conduit that may occur in a system without the multi-bend segment. [0007] Figure 6 is a flow diagram of an example 3D printing build material particulate transport method.

[0008] Figure 7 is a sectional view schematically illustrating portions of an example 3D printing system build material particulate transport system.

[0009] Figure 8 is a diagram illustrating an example method for varying a speed of a stream of gas caring build material particles to vary the location at which the particles impinge portions of a downstream conduit.

[00010] Figure 9 is a sectional view schematically illustrated portions of an example 3D printing system build material particulate transport system.

[00011] Figure 10 is a schematic diagram illustrating portions of an example 3D printing system.

[00012] Throughout the drawings, identical reference numbers designate similar, but not necessarily identical, elements. The figures are not necessarily to scale, and the size of some parts may be exaggerated to more clearly illustrate the example shown. Moreover, the drawings provide examples and/or implementations consistent with the description; however, the description is not limited to the examples and/or implementations provided in the drawings.

DETAILED DESCRIPTION OF EXAMPLES

[00013] Disclosed are example 3D printing build material particulate transport systems and methods that transport build material particulate using a stream of gas to carry the particulate material within a 3D printing system. Such pneumatic build material transport systems allow the 3D printer to be more compact, dust free and easier to use. However, providing a conduit that is flexible for routing, that is conductive so as to reduce the accumulation of charge, that provides reliable seals (does not stress relax on barb fittings) and that offers abrasion resistance presents a challenge.

[00014] High-speed movement of the build material particulate at angles and through bends of the conduit may accelerate internal abrasion of the conduit, leading to damage and failure. Addressing abrasion by using build materials that are less coarse and less likely to abrade the conduit limits the range of materials that may be used for 3D printing. Addressing abrasion by simply forming portions of the conduit out of abrasion resistant materials limits the range of materials that may be used for the conduit and may reduce flexibility of the conduit for routing the conduit within the 3D printing system. Each of such attempts to reduce conduit abrasion and wear limits design flexibility for the 3D printing system.

[00015] Disclosed are example 3D printing build material particulate transport systems and example 3D printing build material particulate transport methods that may enhance design flexibility for a 3D printing system by facilitating the use of a wider range of build materials and a wider range of, potentially less abrasion resistant, materials for the conduit, while still reducing abrasion wear of the conduit. The example systems and methods may reduce abrasion wear of the conduit by introducing a highly abrasion resistant multi-bend segment in the conduit upstream of a bend leading to other segments of the conduit formed from less abrasion resistant materials. The multi-bend segment decelerates the build material particulate such that the build material particulate impacts internal sidewalls of the conduit at a lower speed, reducing abrasion. The other segments of the conduit, formed from the less abrasion resistant materials, provide design flexibility as the other segments may be formed from materials that are more flexible for routing, more highly conductive to reduce charge accumulation and/or that provide more sealing ability as compared to the multi-bend segment. [00016] The example systems and methods may reduce abrasion wear of the conduit by continuously or periodically moving the impingement point of the build material particulate between various locations within the conduit. By moving the impingement point of the build material particulate, the example systems and methods spread or distribute any abrasive wear across a larger internal surface area of the conduit to prolong the working life of the conduit in the 3D printing system. The example systems and methods may move the impingement points and distribute any wear by varying a non-zero speed of the build material particulate along those portions of the conduit susceptible to abrasive wear. As a result, the flow of abrasive build material particulate is not permanently pinpointed on a single spot or region of the conduit. In one implementation, the example systems and methods move the impingement point of the abrasive 3D build material particulate and spread out the abrasive wear by smoothly varying the speed of the gas flowing through the conduit and carrying the build material particulate. In some implementations, the example systems and methods sinusoidally vary the flow speed of the air moving through the conduit to continually move the impingement point of the abrasive 3D build material particulate.

[00017] Each of the disclosed transport systems and methods may be used anywhere in any of various units or components of an overall 3D printing system where build material particulate is transported from one location to another. Transport system 20 may be employed as part of a 3D printer, wherein system 20 delivers the build material particulate from a supply or reservoir to a mechanism that spreads or otherwise deposits the build material particulate in a layer across a build bed or build volume. Transport system 20 may be employed as part of a build material particulate recovery system associated with a 3D printer, wherein transport system 20 transports unsolidified build material particulate from a build bed or build volume for recycling. Transport system 20 may be employed in any modules/elements that may form part of a 3D printing system - e.g. a powder management station, a de-caking station, a powder supply module or the like. [00018] Disclosed is an example three-dimensional (3D) printing build material particulate transport system. The example system may include a build material source, a build material destination, a conduit extending between the build material source and the build material destination and a gas mover for generating a stream of gas through the conduit to carry build material particulate from the build material source downstream to the build material destination. The conduit may include an upstream segment and a downstream segment extending between the upstream segment and the build material destination at an oblique angle relative to the upstream segment.

The conduit may further include an abrasion resistant multi-bend segment between the upstream segment and the build material source which decelerates build material particulates that impinge an internal sidewall of the downstream segment.

[00019] Disclosed is an example 3D printing build material particulate transport method. The method may include carrying build material particulate in a stream of gas through a conduit towards a build material destination, angling the stream of gas, carrying the build material particulate so as to obliquely impinge an internal sidewall of a segment of the conduit downstream and directing the stream of gas through a multi-bend segment upstream the segment to decelerate build material particulate carried in the stream of gas prior to impingement with the internal sidewall.

[00020] Disclosed is an example 3D printing build material particulate transport system. The system may include a build material source, a build material destination, a conduit extending between the build material source and the build material destination and a gas mover for generating a stream of gas through the conduit to carry build material particulate from the build material source to the build material destination. The conduit may include an upstream segment and a downstream segment between the upstream segment and the build material destination, wherein the upstream segment has an axial centerline obliquely intersecting an internal sidewall of the downstream segment. The system may further include a controller to output control signals to the gas mover so as to vary a non-zero speed of the stream of gas.

[00021] Figure 1 is a diagram schematically illustrating portions of an example 3D printing system build material particulate transport system 20. Transport system 20 moves, delivers or otherwise transports 3D build material particulate along a conduit from one location to another with a stream of gas, such as air. Transport system 20 may be used anywhere in any of various units or components of an overall 3D printing system where build material particulate is transported from one location to another. Transport system 20 may be employed as part of a 3D printer, wherein system 20 delivers the build material particulate from a supply or reservoir to a mechanism that spreads or otherwise deposits the build material particulate in a layer across a build bed or build volume. Transport system 20 may be employed as part of a build material particulate recovery system associated with a 3D printer, wherein transport system 20 transports unsolidified build material particulate from a build bed or build volume for recycling. Transport system 20 may be employed in any modules/elements that may form part of a 3D printing system - e.g. a powder management station, a de-caking station, a powder supply module or the like. Transport system 20 comprises build material source 24, build material destination 28, gas mover 30 and conduit 32.

[00022] Build material source 24 comprises any component or location where build material particulate exists and is to be moved to another component or location. In one implementation, build material source 24 comprises a storage bin, container or reservoir that supplies build material for a 3D printer. In another implementation, build material source 24 comprises a build bed or build volume containing build material particulate that is to be withdrawn from the build volume for disposal or recycling. [00023] Build material destination 28 comprises any component or location where build material particulate is to be moved to from the build material source 24. In one implementation, build material destination 28 comprises a platform, tray or other location where the build material is deposited for being spread in a layer across a build bed or build volume. In another implementation, the build material destination 28 comprises a disposal tank or a storage bin, tank or other container.

[00024] Gas mover 30 comprises a mechanism that creates the stream of gas, such as a stream of air, flowing through conduit 32 from build material source 24 to build material destination 28, carrying build material from source 24 to destination 28. In one implementation, gas mover 30 comprises a fan or blower. In one implementation, gas mover 30 generates a negative pressure within conduit 32, drawing a gas and build material from source 24, through conduit 32, to destination 28. In another implementation, gas mover 30 may generate a positive pressure within conduit 32 to move a stream of air and particulate material from source 24, through conduit 32, to destination 28.

[00025] Conduit 32 comprises a pneumatic passage extending between build material source 24 and build material destination 28. Conduit 32 comprises upstream segments 40-1, 40-2 (collectively referred to as segments 40), downstream segment 42 and multi-bend segment 46 (schematically illustrated). Upstream segments 40 extend between multi bend segment 46 and build material source 24. In the example illustrated, segments 46 are part of a single integral unitary tubular body. In the example illustrated, segments 40 are connected by bend 50. Although not illustrated, in some implementations, conduit 32 may include additional segments between segment 40-1 and build material source 24.

[00026] Segment 42 extends between multi-bend segment 46 and build material destination 28 at an oblique angle relative to the segment of conduit 32 immediately preceding multi-bend segment 46, segment 40-2. In the example illustrated, segment 42 extends at an angle of between 10° and 30° relative to the axial centerline of segment 40-2. In the example illustrated, segment 42 extends immediately adjacent to multi-bend segment 46.

[00027] Segment 42 is formed from a material suited for delivering 3D build material particulate in 3D printing system 20. For example, segment 42 is formed from a material that sufficiently flexible such that it can be bent to provide nonlinear routing of build material particulate within system 20. In the example illustrated, segment 42 has a flexibility corresponding to a Shore durometer of 70. Segment 42 is formed from material that is also sufficiently charge conductive so as to minimize the accumulation of electrical charge. In the example illustrated, segment 42 has an electric charge conductivity of less than 100 ohm*cm. Segment 42 may also be formed from a material that offers reliable sealing with respect to connected fittings. For example, conduit 40 does not stress relax on barb fittings. In the example illustrated, segment 42 is formed from a material having an elasticity corresponding to Shore A durometer of 70, a radial interference of approximately 12% (for example, the inner diameter of the silicone tube conduit is 15.9 mm, and an outer diameter of the nylon mating part that it slides over is18.0 mm), and a cross-link density that suffices to keep the part from relaxing. In some implementations, segment 42 may be formed from a material that may be deficient with respect to any of the above criteria.

[00028] Many of the materials that satisfy each of the above criteria or some of the above criteria are susceptible to abrasive wear, especially at the oblique angle, given the characteristics of the build material particulate being conveyed by the airstream generated by gas mover 30 and given the speed and momentum of the particles of the airflow that would exist but for multi bend segment 46. For example, a non-brittle material such as silicone may be especially vulnerable to abrasion when impinged at an attack angle of 10° to 30°. For purposes of this disclosure, a segment of conduit 32 is considered to be undergoing abrasion when its original wall thickness (in the example, approximately 3 m ) may be reduced to zero over the course of one year of use. . In the example illustrated, segment 42 is formed from a flexible, charge conductive, sealable, yet abrasion susceptible material such as silicone. In other implementations, segment 42 may be formed from other materials such as polyurethane, or acrylonitrile butadiene (ABS).

[00029] Multi-bend segment 46 extends between upstream segment 40- 2 and downstream segment 42. Multi-bend segment 46 may be formed from a material that is more abrasion resistant as compared to the material of segment 42, but where the material of multi-bend segment 46 fails to satisfy the flexibility, charge conductivity and seal ability performance criteria satisfied by segment 42. Because multi-bend segment 46 comprises a relatively small component relative to the much longer length of downstream segment 42, any deficiencies of segment 46 do not substantially impair the overall performance of system 20. In the example illustrated, multi-bend segment 46 may be formed from a material such as carbon filled nylon material. In other implementations, other materials such as steel or copper or thermoset polyurethane may be used.

[00030] Multi-bend segment 46 comprises multiple turns or bends. The bends each have a sufficiently sharp turn such that larger, erosive build material particles impinge at a large enough angle such that the momentum of the particles is substantially reduced. Because multi-bend segment 46 is formed from abrasion resistant material, any abrasive wear of ultimate segment 46 caused by the erosive build material particles impinging the interior sides multi-bend segment 46 is at an acceptable level, a level much less than the level of abrasive wear that might otherwise occur had such particles impinged segment 42. At the same time, the multiple bends of segment 46 temporarily decelerate the flow of build material particulate to a lower speed such that the build material particulate is less abrasive when flowing out of segment 46 and impinging downstream segment 42. Although smaller particulates may follow the streamline, avoid impact and not be greatly decelerated, it is larger particles that tend to have the greatest tendency to impact conduit walls and erode them. Segment 46 reduces erosion by especially decelerating the larger particles.

[00031] Although system 220 is illustrated as comprising a single multi bend segment 46 preceding a single abrasion susceptible conduit 42, in other implementations, system 220 may include multiple abrasion susceptible conduit 42 and multiple multi-bend segments 46 each proceeding a respective abrasion susceptible conduit 42. In other words, a multi-bend segment 46 may be inserted anywhere along conduit 32 between source 24 and destination 28 where downstream portions of the conduit 32 are undergoing abrasion wear at accelerated rates that reduce the useful life of system 220 to below an acceptable period of time.

[00032] Figure 2 provides an example illustration of system 20 without multi-bend segment 46. As shown by Figure 2, build material particulate accelerates as it travels through segments 40-1 and 40-2, going from a low speed represented by arrow 60 to a medium speed represented by arrow 62 and then to a high speed represented by arrows 64. In other implementations, the particles may not further accelerate in segments 40, but may be at a sufficiently high speed when entering segments 40 so as to cause erosion of segment 42. In one implementation, the smallest build material particles, less than 10 pm in size, are carried along the streamlines while the larger particles, up to 70 to 90 pm in size, are centrifugally moved to the impingement location 70. The build material particles impinging downstream conduit 42 at impingement location 70 impinge the internal sidewalls of segment 42 at the high speed. In the example illustrated, the particles impinge conduit 42 at impingement location 70 at a speed of at least 8 m/sec and at an angle of between 10 and 30°, which results in accelerated abrasion of conduit 42 at location 70. [00033] As shown by Figure 1, multi-bend segment 46 decelerates speed of the particles such that the speed of the build material particulate exiting multi-bend segment 46 is at a lower speed represented by arrows 66, a speed less than the particulates upstream of the multi-bend segment, shown by arrow 64. This lower impingement speed results in less abrasive wear at impingement location 70. In some implementations, the speed of the flow of build material particulate is re-accelerated back up to the speed of the gas prior to reaching the build material destination 28.

[00034] In the example illustrated, multi-bend segment 46 may comprise two 90° elbows such that segment 46 has an S-shape. In other implementations, multi-bend segment 46 may comprise additional 90° elbows or other bends or turns having other angles so long as the multiple bends or turns sufficiently decelerate the speed of the build material particulate to a point such that the build material particulate has a sufficiently reduced abrasive wear of downstream segment 42. In one implementation, multi-bend segment 46 decelerates the speed of the build material particular to a point such that the wear rate is low enough to allow the conduit to last for the life of printer without replacement. This would correspond to less than 3 mm of wear for the transport of 30,000 kg of particulate..

[00035] Figure 3 is a graph illustrating differences in wear of conduit 42 during an example test. Figures 4 and 5 are sectional views of portions of conduit 42 about location 70 following the example test. As shown by Figure 3, the inclusion of multi-bend segment 46 reduces the rate of abrasion at location 70 in conduit 42. The conduit 42 in Figure 4 had a multi-bend segment 46 (similar to shown Figure 1) upstream; conduit 42 in Figure 5 which was part of a system that did not include multi-bend segment 46 (similar to Figure 2). As shown by Figure 3, the example multi-bend segment may reduce the wear rate by approximately a factor of four. [00036] Figure 5 is a flow diagram of an example 3D printing system build material particulate transport method 100. Method 100 reduces abrasion where of a conduit by decelerating erosive build material particles immediately prior to the particles impinging and abrasion vulnerable portion of the conduit. Method 100 may enhance design flexibility for a 3D printing system by facilitating the use of a wider range of build materials and a wider range of, potentially less abrasion resistant, materials for the conduit, while still reducing abrasion wear of the conduit. Although method 100 is described in the context of being carried out using system 20, it should be appreciated that method 100 may likewise be carried out with any of the following described transport systems or the other similar 3D build material particulate transport systems.

[00037] As indicated by block 104, system 20 carries build material particulate in a stream of gas through a conduit 32 towards a build material destination 28. The stream of gas may be created by a pressure differential along the conduit, with pressure decreasing in the direction of flow, and either positive or negative gage pressures in the conduit.

[00038] As indicated by block 108, the stream of gas, carrying the build material particulate is angled so as to obliquely impinge internal sidewall of a segment of the conduit 42 downstream, segment 42. In one implementation, the impingement angle is between 10° and 30°. At such impingement angles, wear may be especially accelerated.

[00039] As indicated by block 112, the stream of gas carrying the build material particulate is directed through a multi-bend segment to decelerate the build material particulate carried by the stream of gas prior to impingement with the internal sidewall, prior to impingement at impingement location 70.

As described above with respect to system 20, the erosive particles of build material are decelerated to a lower speed so as to reduce abrasive wear at the impingement location, prolonging the useful life of segment 42 and the build material transport system.

[00040] Figure 7 is a schematic diagram illustrating portions of an example 3D printing system build material particulate transport system 220. Figure 6 illustrates one example of how the speed at which build material particular to carried along conduit 32 may be varied to prolong the useful life of a build material conduit. Transport system 220 moves, delivers or otherwise transports 3D build material particulate along a conduit from one location to another with a stream of gas, such as air. Transport system 220 may be used anywhere in any of various units or components of an overall 3D printing system where build material particulate is transported from one location to another. Transport system 220 may be employed as part of a 3D printer, wherein system 220 delivers the build material particulate from a supply or reservoir to a mechanism that spreads or otherwise deposits the build material particulate in a layer across a build bed or build volume. Transport system 220 may be employed as part of a build material particulate recovery system associated with a 3D printer, wherein transport system 220 transports unsolidified build material particulate from a build bed or build volume for recycling. Transport system 220 is similar to transport system 20 described above except that transport system 220 omits multi-bend segment 46, but includes controller 274. Those remaining components of transport system 220 which correspond to components of transport system 20 are numbered similarly.

[00041] Controller 274 controls the generation of the stream of gas within conduit 32 by gas mover 30. Controller 274 comprises processing unit 276 and memory 278. Processing unit 276 outputs control signal to gas mover 30 based upon instructions provided by memory 278. Memory 278 comprises a non-transitory computer-readable medium, such as a memory or storage device, containing such instructions. Such instructions may be in the form of hardwired logic or software/programming. The instruction contained in memory 278 direct processing unit 274 to output control signals that cause gas mover 30 to vary a non-zero speed of the stream of gas, such as air, being moved through conduit 32.

[00042] As shown by Figure 7, during a first period of time, the stream of gas through conduit 32 and generated by gas mover 30 is at a first speed represented by arrow 280. Those build material particles carried by the stream of gas moving at the first speed are centrifugally moved so as to impinge conduit 42 at a first impingement location 270-1. During a second period of time, the stream of gas through conduit 32 and generated by gas mover 30 is at a second slower speed represented by arrow 282. Those build material particles carried by the stream of gas moving at the second speed are centrifugally moved so as to impinge conduit 42 at a second impingement location 270-2. During yet a third period of time, the stream of gas through conduit 32 and generated by gas mover 30 is at a third speed less than the second speed and represented by arrow 284. Those build material particles carried by the stream of gas moving at the third speed are centrifugally moved so as to impinge conduit 42 at a third impingement location 270-3.

[00043] By moving the impingement point of the build material particulate, system 220 spreads or distributes any abrasive wear across a larger internal surface area of the conduit 42 to prolong the working life of the conduit 42 in the 3D printing system. System 220 may move the impingement points 270 and distribute any wear by varying a non-zero speed of the build material particulate along those portions of the conduit 42 susceptible to abrasive wear. As a result, the flow of abrasive build material particulate is not permanently pinpointed on a single spot or region of the conduit 42.

[00044] In one implementation, system 220 moves or shifts the impingement point of the abrasive 3D build material particulate and spreads out the abrasive wear by controller 274 outputting control signals that cause gas mover 30 to smoothly vary the speed of the gas flowing through the conduit 32 and carrying the build material particulate. In some implementations, controller 274 outputs control signals causing gas mover 30 to sinusoidally vary the flow speed of the air moving through the conduit to continually move the impingement point of the abrasive 3D build material particulate.

[00045] Figure 8 is a diagram illustrating one example of how controller 274 may output control signals causing gas mover 30 to sinusoidally vary the speed of the gas flowing through conduit 32 and carrying the build material particulate. As shown by diagram 300, instructions and memory 278 may cause processor 276 to output a sinusoidally varying control voltage 302 to gas mover 30. As shown by diagram 304, this results in a sinusoidally changing speed of the gas flow through conduit 32. This smooth, sinusoidally varying speed continually moves or shifts the location at which the larger erosive build material particles impinge the internal sidewalls of conduit 42. [00046] Figure 9 is a diagram schematically illustrating portions of an example 3D build material particulate transport system 420. Figure 9 illustrates one example of how abrasion wear of a conduit delivering 3D printer build material may be reduced by both varying the speed of the airflow carrying the build material particulates and decelerating the build material particulates immediately prior to their impingement with abrasion susceptible portions of a conduit. System 420 is similar to system 220 described above except that system 420 additionally comprises multi-bend segment 46, described above. The remaining components of system 420 which correspond to components of systems 20 and 220 are numbered similarly.

[00047] System 420 is operable in one of multiple different abrasion- reducing modes as selected by an operator through an input device. In a first mode of operation, processing unit 276 of controller 274 follows instructions contained in memory 278 to output control signals causing gas mover 30 to generate a stream of gas through conduit 32 that has a substantially uniform or consistent speed, wherein multi-bend segment 46 decelerates the momentum of the 3D build material particles immediately prior to their impingement with impingement location 270 to reduce wear at impingement location 270. Following a predetermined period of time or based upon a sensed amount of wear at impingement location 270, as indicated by signals from sensor 280 (schematically illustrated) instructions contained in memory 278 may cause processing unit 276 to output control signals to gas mover 30 to adjust a speed of the gas flow through conduit 32 so as to move the impingement location 270. In one implementation, sensor 280 may comprise a capacitive sensor.

[00048] Multi-bend segment 46 slows the rate of abrasion wear at impingement location 270. Once the abrasion at location 270 has reached a predetermined amount of wear, a predetermined depth as sensed by sensor 280, or following a predetermined length of time empirically determined as corresponding to the time at which location 270 has undergone a predetermined amount of wear, controller 274 moves the impingement location 270, where the rate of future abrasion at the new location 270 is also reduced by multi-bend segment 46.

[00049] In a second mode of operation, controller 274 may operate in a fashion similar to that described above with respect to figure 6, wherein controller 274 continually moves the impingement location 275 smoothly varying the speed of the gas moving through conduit 32 and carrying the 3D build material particulate. In some implementation, controller 274 may receive input identifying the type or characteristics of the build material particulate being transported, wherein controller 274 may consult a stored lookup table of values to determine the speed or the range of speeds of gas flow that should be provided by gas mover 30 to adequately carry the build material particulate, yet reduce abrasion wear of segment 42.

[00050] Figure 10 is a schematic diagram illustrating portions of an example 3D printing system 500. 3D printing system 500 incorporates a 3D printing system build material particulate transport system similar to that shown in Figure 8 and carries out method 100 described above. 3D printing system 500 comprises build volume 522, build material platform 524, excess build material receiver 526, build floor elevator 528, build material supply (BMS) 530, build material spreader 532, spreader drive 533, solidifier 534, carriage 536, build material particulate transport system 620 and controller 540.

[00051] Build volume 522, sometimes referred to as a build bed, comprises a chamber to contain the layers of build material 546 formed by build material spreader 532 and selectively solidified or fused to form the three-dimensional part or object. Build volume 522 comprises a vertically movable floor 542. Floor 542 is raised and lowered by build floor elevator 528. Build floor elevator 528 comprises an actuator to raise and lower floor 542 as build volume 522 is being filled with build material on a layer-by-layer basis and as each of the individual layers are selectively solidified by solidifier 534. In one implementation, build floor elevator 528 comprises a motor operably coupled to build floor 542 by a rack and pinion drive to linearly raise and lower floor 542. In other implementations, build floor elevator 528 may comprise other mechanisms for raising and lowering floor 542 in a controlled fashion to control the thickness of the build layers being formed during each pass of build material spreader 532.

[00052] Build material platform 524 comprises a surface adjacent to an edge of build volume 522 and upon which a mound of build material 544 may be deposited, ready for being spread across build material volume 522 by build material spreader 532. Excess build material receiver 526 extends on opposite side of build volume 522 as platform 524. Receiver 526 receives any excess build material not used to form the topmost build layer during the most recent pass of spreader 532 across build volume 522. Such excess build material may be recovered for disposal or reuse.

[00053] In one implementation, excess build material receiver 526 comprises a platform similar to platform 524. In such an implementation, the build material spreader 532 spreads build material from right to left. Upon reaching the platform provided by receiver 526, the spreader 532is lifted above the pile remnant of build material and the spreader is moved to the left of the remnant pile on platform 526. After passing the pile remnant, the spreader 532 is lowered and then driven back to the right, spreading the remnant pile of build material in the opposite direction.

[00054] Build material supply 530 receives build material from build material transport 620 and forms a mound 544 of build material on top of platform 524 along a length of build volume 522 being spread by spreader 532. In one implementation, build material supply 530 comprises an auger that conveys and deposits the mound 544 of build material on platform 324.

In still other implementations, other mechanisms may be used to deposit mound 544 on platform 524. For example, in some implementations, a translating hopper may be used to deposit mound 544. In yet other implementations, other mechanisms may be used to form a row of build material for being spread by spreader 532.

[00055] Build material spreader 532 comprises a structure to spread build material across build volume 522 so as to form a layer of build material for being selectively solidified. Build material spreader 532 has a build material spreading surface which grades or pushes a mound of build material across a build volume, spreading the mound in a layer across the build volume.

[00056] Spreader drive 533 comprises a linear actuator to linearly translate build material spreader across the length (orthogonal to the width) of the build volume 522.

[00057] Solidifier 534 carries out solidification of selected portions of the individual layers of build material in build volume 522. In one implementation, solidifier 534 comprises fusing agent deposition and heating systems, binder agent deposition systems, laser sintering systems and the like which operate on the underlying portions of the build layers in build volume 522. In some implementations, solidifier 534 comprises a chemical binding system such as powder bed and inkjet or drop on powder (binder jet 3D printing) system or metal type 3D printing system. In some implementations, solidifier 534 heats the build material to melt the build material to a point of the liquefaction prior to being solidified. In other implementations, solidifier 534 carries out sintering of the build material, wherein the build material is compacted into a solid mass of material by heat or pressure without melting to a point of liquefaction.

[00058] Carriage 536 controllably position solidifier 534 over selected portions of build volume 522. In one implementation, carriage 536 is selectively positioned opposite to selected portions of the layers of build material provided by build volume 522 by a motor and a rack and pinion drive, an electric solenoid, a hydraulic-pneumatic cylinder a piston assembly or the like to facilitate the solidification of selected portions of the layers of build material in build volume 322.

[00059] In some implementations, solidifier 534 may have other forms and may interact with selected portions of the build material and build volume 522 in other fashions. For example, solidifier 534 may have a first portion carried by carriage 536 that selectively jets or otherwise deposits fusing agents on the build material and a second portion coupled to spreader 532 so as to be driven by spreader drive 533 and so as to complete or further carry out the solidification process (fusing or curing) with the assistance of the previously deposited fusing agents. In yet other implementations, carriage 536 may be omitted such as where solidifier 534 is carried by spreader 532 and driven by spreader drive 533 or where solidifier 534 is stationary, but is capable of interacting with a sufficient area of build volume 522. In some implementations where solidifier 524 carries out selective laser sintering, carriage 536 may be omitted. [00060] 3D printing build material particulate transport system 620 delivers 3D printer build material particulate to build material supply 530 (the build material destination) from build material source 24 in the form of a build material storage bin or reservoir. System 620 comprises gas mover 30 and controller 274 (described above with respect to systems 20 and 420, respectively). System 620 further comprises conduit 632.

[00061] Conduit 632 extends between build material source 24 and build material supply 530. Conduit 632 comprises segments 640-1 , 640-2 (collectively referred to as segments 640), segment 42 (described above) and multi-bend segment 646. Segments 640 diverge from one another. Segment 640-1 directs gas carried particulate material to a secondary destination 628. Segment 640-2 directs gas carried particulate material towards build material supply 530. Each of segments 640 may be formed from an abrasion resistant material such as a carbon filled nylon material. In other implementations, other materials such as steel or copper or thermoset polyurethane may be used.

[00062] In the example illustrated, segments 640 are integrally formed as a single unitary body which forms a housing for containing a diverter valve 641. Diverter valve 641 comprises a valve mechanism for selectively directing the flow of gas and the carried particulate material through segment 640-1 to secondary destination 628 or through segment 640-2 to build material supply 530.

[00063] As indicated by arrow 647, segment 640-2 has a centerline so as to direct the gas flow and carried particulate material in a direction oblique to the axial centerline of segment 42. As a result, but for multi-bend segment 646, the gas carried particles would impinge the interior side walls of segment 42, potentially eroding the interior side walls of segment 42. In the example illustrated, segment 640-2 has a centerline that extends at an oblique angle of between 10° and 30° relative to the axial centerline of segment 42. At such an angle, a direct connection between segment 640-2 and segment 42 might otherwise result in accelerated erosion of the interior side walls of segment 42.

[00064] Multi-bend segment 646 extends between segment 640-2 and segment 42 to reduce erosion of segment 42 by the gas born particles. As with multi-bend segment 46, multi-bend segment 646 is formed from a material that is more abrasion resistant as compared to the material of segment 42, but where the material of multi-bend segment 46 may fail to satisfy the flexibility, charge conductivity and seal ability performance criteria satisfied by segment 42. Because multi-bend segment 46 comprises a relatively small component relative to the much longer length of downstream segment 42, any deficiencies of segment 646 do not substantially impair the overall performance of system 620. In the example illustrated, multi-bend segment 46 may be formed from a material such as carbon filled nylon material. In other implementations, other materials such as steel or copper or thermoset polyurethane may be used.

[00065] In the example illustrated, multi-bend segment 646 comprises separate component mounted between segment 640-2 in segment 42. In some implementations, multi-bend segment 646 may be integrally formed as a single unitary body with the body forming segment 640-1 and 640-2. In some implementations, multi-bend second 646 may be co-molded with segment 640-2 and/or segment 42, wherein segment 646 is molded out of a different material as compared to segment 42.

[00066] Multi-bend segment 46 comprises multiple turns or bends. In the example illustrated, multi-bend segment 646 comprises two 90° elbows. The bends each have a sufficiently sharp turn such that larger, erosive build material particles impinge at a large enough angle such that the momentum of the particles is substantially reduced. Because multi-bend segment 646 is formed from abrasion resistant material, any abrasive wear of ultimate segment 46 caused by the erosive build material particles impinging the interior sides multi-bend segment 46 is at an acceptable level, a level much less than the level of abrasive wear that might otherwise occur had such particles impinged segment 42. At the same time, the multiple bends of segment 646 temporarily decelerate the flow of build material particulate to a lower speed such that the build material particulate is less abrasive when flowing out of segment 46 and impinging downstream segment 42. Although smaller particulates may follow the streamline, avoid impact and not be greatly decelerated, it is larger particles that tend to have the greatest tendency to impact conduit walls and erode them. Segment 46 reduces such erosion by especially decelerating the larger particles.

[00067] Although system 620 is illustrated as including a single multi bend segment 646, in other implementations, system 620 may include additional multi-bend segments upstream of any other locations where gas carried particles may impinge and abrasively erode a downstream location. For example, additional multi-bend segments may be provided upstream of any location where gas carried particles may impinge a downstream abrasion vulnerable portion of a conduit at an angle of between 10° and 30°. In some implementations, system 620 may additionally include a multi-bend segment similar to segment 646 between segment 640-1 and the secondary destination 628, such as where the particles being carried by the gas flowing through segment 640-1 would otherwise impinge the internal sidewalls of a downstream abrasion vulnerable segment, similar to segment 42.

[00068] Controller 274 is described above. As described above, controller 274 may be operable in one of multiple different abrasion-reducing modes as selected by an operator through an input device. In a first mode of operation, processing unit 276 of controller 274 follows instructions contained in memory 278 to output control signals causing gas mover 30 to generate a stream of gas through conduit 32 that has a substantially uniform or consistent speed, wherein multi-bend segment 646 decelerates the momentum of the 3D build material particles immediately prior to their impingement with impingement location 270 to reduce wear at impingement location 270. Following a predetermined period of time or based upon a sensed amount of wear at impingement location 270, as indicated by signals from sensor 280 (schematically illustrated) instructions contained in memory 278 may cause processing unit 276 to output control signals to gas mover 30 to adjust a speed of the gas flow through conduit 32 so as to move the impingement location 270. In one implementation, sensor 280 may comprise a capacitive sensor.

[00069] Multi-bend segment 646 slows the rate of abrasion wear at impingement location 270. Once the abrasion at location 270 has reached a predetermined amount of wear, a predetermined depth as sensed by sensor 280, or following a predetermined length of time empirically determined as corresponding to the time at which location 270 has undergone a predetermined amount of wear, controller 274 moves the impingement location 270, where the rate of future abrasion at the new location 270 is also reduced by multi-bend segment 646.

[00070] In a second mode of operation, controller 274 may operate in a fashion similar to that described above with respect to figure 6, wherein controller 274 continually moves the impingement location 270, smoothly varying the speed of the gas moving through conduit 42 and carrying the 3D build material particulate. In some implementation, controller 274 may receive input identifying the type or characteristics of the build material particulate being transported, wherein controller 274 may consult a stored lookup table of values to determine the speed or the range of speeds of gas flow that should be provided by gas mover 30 to adequately carry the build material particulate, yet reduce abrasion wear of conduit 42.

[00071] Controller 540 controls the positioning of carriage 536 as well as the solidification of portions of the build layers by solidifier 534. Controller 540 comprises memory 550 and processing unit 552. Memory 550 contains instructions for directing processing unit 552 to carry out control determinations and to output control signals to carriage 536 and solidifier 534. For example, instruction contained in memory 550 may direct processing unit 552 to access a file 554 describing the composition, shape and size of a three-dimensional object 560 to be formed on a layer-by-layer basis in build volume 522. Based upon information read from the file, processing unit 552, following instruction contained in memory 550, output signals to carriage 536 to then position solidifier 534 opposite to appropriate portions of the layer of build material. Such instructions further direct solidifier 534 to carry out a solidification process on selected portions of the layer of build material currently being presented in build volume 522. This process is repeated layer by layer until the three-dimensional object defined in the file 554 has been formed. In some implementations, once each three-dimensional object has been formed within the build volume 522, the build volume 522 may be removed from system 500 and transferred to a processing station where the formed objects are removed and the unused build material is recovered and potentially recycled. In some implementations, the unused build material is auto-extracted and recycled. In some implementations, the control functions of controller 540 and controller 274 may be combined and carried out by a single control unit.

[00072] Figure 10 further illustrates the forming of an example three- dimensional part or object 560 on a layer-by-layer basis in build volume 522. To form the next success of solidified layer of object 560, controller 540 communicates with controller 274 causing controller 274 to output control signals causing gas mover 30 to deliver a stream of gas carrying the build material particles from build material source 24 through conduit 632 to build material supply 530. Build material supply 530 deposits mound 544 of the build material on platform 524 along the width of build volume 522. Once the mound 544 of build material has been deposited upon platform 524, controller 540 outputs control signals causing spreader drive 533 to translate build material spreader 532 across build volume 522, grading or pushing the mound 544 of build material over and across build volume 522.

[00073] Figure 10 illustrates the repositioning of build material spreader 532 (shown in broken lines) as it is been moved or translated across build volume 522 by spreader drive 533. As further shown in broken lines, during its movement across build volume 522, build material spreader 532 creates a new layer of build material on top of build volume 522. As indicated by arrow 564, selected portions of this layer are solidified by solidifier 534, building object 560 on a layer-by-layer basis. Any remaining excess build material not used to form layer 560 is pushed into receiver 526.

[00074] Although the present disclosure has been described with reference to example implementations, workers skilled in the art will recognize that changes may be made in form and detail without departing from disclosure. For example, although different example implementations may have been described as including features providing various benefits, it is contemplated that the described features may be interchanged with one another or alternatively be combined with one another in the described example implementations or in other alternative implementations. Because the technology of the present disclosure is relatively complex, not all changes in the technology are foreseeable. The present disclosure described with reference to the example implementations and set forth in the following claims is manifestly intended to be as broad as possible. For example, unless specifically otherwise noted, the claims reciting a single particular element also encompass a plurality of such particular elements. The terms “first”, “second”, “third” and so on in the claims merely distinguish different elements and, unless otherwise stated, are not to be specifically associated with a particular order or particular numbering of elements in the disclosure.