WO2017127113A1

WO2017127113A1 - Layering powdered build material for additive manufacturing

Info

Publication number: WO2017127113A1
Application number: PCT/US2016/014554
Authority: WO
Inventors: Brent EWALD
Original assignee: Hewlett-Packard Development Company, L.P.
Priority date: 2016-01-22
Filing date: 2016-01-22
Publication date: 2017-07-27

Abstract

In one example, a powdered build material layering system for additive manufacturing includes a work area and a dispenser to dispense powdered build material on to the work area. One or both of the dispenser and the work area being movable with respect to the other of the dispenser and/or the work area to layer powdered build material on to the work area in a thickness corresponding to a gap between the dispenser and the work area, and the gap is small enough to choke the flow of powdered build material from the dispenser to the work area when there is no relative motion between the dispenser and the work area.

Description

LAYERING POWDERED BUILD MATERIAL FOR ADDITIVE

MANUFACTURING

BACKGROUND

[0001] Additive manufacturing machines produce 3D (three-dimensional) objects by building up layers of material. Some additive manufacturing machines are commonly referred to as "3D printers." 3D printers and other additive manufacturing machines make it possible to convert a CAD (computer aided design) model or other digital representation of an object into the physical object. The model data may be processed into slices each defining that part of a layer or layers of build material to be formed into the object.

DRAWINGS

[0002] Fig. 1 is a block diagram illustrating an additive manufacturing machine implementing one example of a powdered build material layering system.

[0003] Fig. 2 is an isometric illustrating one example of a layering system, such as might be used in the machine shown in Fig. 1 , layering powdered build material on to a work area.

[0004] Figs. 3-5 are sections illustrating one example of a powdered build material layering system.

[0005] Figs. 6-9 present a sequence of sections illustrating another example of a powdered build material layering system, layering powdered build material on to a work area.

[0006] Figs. 10-18 present a sequence of sections illustrating one example for manufacturing a multi-slice object using a layering system such as those shown in Figs. 3-5 and Figs. 6-9.

[0007] Fig. 19 illustrates one example of an additive manufacturing process that uses choked flow to layer powdered build material on to a work area.

[0008] Fig. 20 is a block diagram illustrating one example of a processor readable medium with instructions to use a choked flow configuration to layer powdered build material on to a work area. [0009] Fig. 21 is a block diagram illustrating one example of an additive manufacturing machine implementing a controller with choked flow layering instructions.

[0010] The same part numbers designate the same or similar parts throughout the figures. The figures are not necessarily to scale.

DESCRIPTION

[0011] In some additive manufacturing processes, heat is used to fuse together the particles in a powdered build material to form a solid object. Heat to fuse the build material may be generated, for example, by applying a liquid fusing agent to a thin layer of powdered build material in the pattern of the object slice and then exposing the patterned area to light. Light or other energy absorbing components in the fusing agent absorb energy to help sinter, melt or otherwise fuse the build material. The process is repeated layer by layer, slice by slice to complete the object.

[0012] A new technique has been developed for dispensing powdered build material on to the work area in an additive manufacturing machine to help more effectively deliver consistent layering. In one example, the new technique is implemented in a system in which one or both of the build material dispenser and the work area is movable to layer powdered build material on to the work area in a thickness corresponding to the gap between the dispenser and the work area. The gap is small enough to choke the flow of powdered build material from the dispenser to the work area when the dispenser is stationary with respect to the work area. Thus, the build material can be layered with the dispenser alone, if desired, without dispensing excess powder and to a uniform thickness even on in-process structures and other work areas with variable coverage volumes. In another example, the new technique is implemented in an additive manufacturing process in which the flow of powdered build material to a work area is choked, the choked flow is cleared and, while clearing the choked flow, layering powdered build material on to the work area. Build material is then patterned and fused to form an object slice, and the process repeated for each slice of the object. [0013] These and other examples enable the use of a mass flow hopper to both dispense and layer powdered build material. Also, the build material can be dispensed and layered simultaneously, directly on to the work area, for uniform coverage even across areas of varying fill without dispensing excess material. Choked flow, usually an undesirable characteristic in powdered material supply systems, is exploited to help control and meter the delivery of powdered build material on to the work area in an additive manufacturing machine.

[0014] These and other examples described below and shown in the figures illustrate but do not limit the scope of the patent, which is defined in the Claims following this Description.

[0015] As used in this document: "and/or" means one or more of the connected things; a "detailing agent" means a substance that inhibits or prevents or enhances fusing a build material, for example by modifying the effect of a fusing agent; "energy" means electromagnetic radiation of any wavelength; a "fusing agent" means a substance that causes or helps cause a powdered build material to sinter, melt or otherwise fuse; and "work area" means any suitable structure to support or contain build material for fusing, including underlying layers of build material and in-process slice and other object structures.

[0016] Fig. 1 is a block diagram illustrating an additive manufacturing machine 10 implementing one example of a powdered build material layering system 12. The block diagram of Fig. 1 shows one example for the layout of a machine 10 implementing system 12. Other layouts are possible. Referring to Fig. 1 , machine 10 includes layering system 12, energy bars 14, and a fusing agent dispenser 16 located near a work area 18. Work area 18 in the figures represents any suitable structure to support or contain build material for fusing, including underlying layers of build material and in-process slice and other object structures.

[0017] Layering system 12 includes a movable dispenser 20 and a surface 18 to block the flow of powdered build material from dispenser 20 when dispenser 20 is stationary over surface 18, and to not block the flow of powdered build material from dispenser 20 when dispenser 20 is moving over surface 18. For example, dispenser 20 and surface 18 are separated by a gap that is small enough to choke the flow of powder from a stationary dispenser 20 and big enough to clear the choke and allow powder flow when dispenser 20 is moving over surface 18. In the example shown in Fig. 1 , work area 18 forms the blocking surface in layering system 12. Thus, a work area blocking surface 18 may include underlying layers of build material and in-process object slices as an object is manufactured layer by layer and slice by slice.

[0018] Also in the example shown in Fig. 1 , dispenser 20 is mounted together with a pair of energy bars 14 on a movable carriage 22. Carriage 22 carries dispenser 20 and energy bars 14 back and forth over work area 18, as indicated by direction arrows 24. Fusing agent dispenser 16 is also movable back and forth over work area 18, as indicated by direction arrows 26. Alternate "parking" positions for fusing agent dispenser 16 and carriage 22 across work area 18 are depicted by phantom lines in Fig. 1 .

[0019] Fig. 2 is an isometric showing a dispenser 20 and energy bars 14 over a work area blocking surface 18. Referring now also to Fig. 2, in operation powdered build material 28 is dispensed on to work area 18 through an elongated opening 30 in dispenser 20 as carriage 22 moves across work area 18. The moving dispenser 20 forms a layer 32 of powdered build material 28 on the stationary work area 18. Carriage 22 with dispenser 20 and energy bars 14 is exploded away from work area 18 in Fig. 2 to more clearly show layering powder 28 on to work area 18. A liquid fusing agent is selectively applied to layered build material 32 on work area 18 in a pattern corresponding to an object slice, as fusing agent dispenser 16 is scanned across work area 18 (Fig. 1 ). One or both energy bars 14 are energized to expose the patterned area to light or other electromagnetic radiation to fuse build material where fusing agent is applied, as carriage 22 (carrying bars 14) is scanned over work area 18. In the example shown in Fig. 2, each energy bar 14 is configured as an array of LEDs, laser diodes or other light sources 34 that span work area 18. The process of layering and fusing is repeated to form a multi-slice object. [0020] Figs. 3-5 illustrate one example of a powdered build material layering system 12, such as might be used in machine 10 shown in Fig. 1 . Referring to Figs. 3-5, system 12 includes a dispenser 20 and a work area or other horizontal blocking surface 18 spaced apart from dispenser 20 across a gap 36. In this example, dispenser 20 is configured as a hopper that includes a receptacle 38 to hold build material 28 and an elongated opening 30 oriented horizontally along a bottom part 40 of receptacle 38. Powdered build material 28 may be dispensed from receptacle 38 through opening 30 on to surface 18. Opening 30 extends lengthwise in a direction perpendicular to the direction of relative motion between surface 18 and dispenser 20. The direction of relative motion is indicated by arrows 24 in Fig. 4.

[0021] Gap 36 is small enough to choke the flow of powder 28 from hopper 20 when hopper 20 and surface 18 are stationary relative to one another, and big enough to allow powder flow when hopper 20 is moving over surface 18 and/or surface 18 is moving under hopper 20. In Fig. 3, hopper 20 and surface 18 are stationary relative to one another to choke (and thus block) the flow of powder 28 through opening 30 across gap 36. When hopper 20 and surface 18 are stationary as shown in Fig. 3, powder 28 will flow out of hopper 20 until the angle of repose of the powder accumulating in gap 36 meets the top of opening 30, at which point the flow is choked off. This choking condition will block the flow of powder 28 until there is relative motion between hopper 20 and surface 18.

[0022] In Fig. 4, one or both of hopper 20 and surface 18 are moving, as indicated by arrows 24, to layer powder 28 on to surface 18. When there is motion between hopper 20 and surface 18 as shown in Fig. 4, powder 28 is dragged from opening 30 and flows into gap 36 until the relative motion stops. So long as the speed of hopper 20 relative to surface 18 does not exceed the flow capacity of hopper 20, the thickness of powder layer 32 is determined by the size of gap 36. Accordingly, gap 36 can be set to the desired thickness for each layer 32 of powdered build material 28, for example by moving hopper 20 and/or surface 18 vertically with respect to other. The top surface of each layer of powdered build material is delineated with a line in the figures for clarity, and does necessarily suggest a smooth flat surface.

[0023] Figs. 6-9 present a sequence of sections illustrating one example for layering powdered build material 28 on to a work area blocking surface 18 using a layering system 12. In Figs. 6-9, hopper 20 includes a valve 42 to control the flow of powder 28 from receptacle 38 to opening 30. In Fig. 6, surface 44 of a movable platform 46 forms work area 18 and hopper 20 is parked to the side of work area 18 with valve 42 closed. In Fig. 7, valve 42 is open and hopper 20 is moving over work area 18, as indicated by direction arrow 24, to layer build material 28 on to work area 18 across a gap 36 corresponding to the desired thickness of layer 32. In Fig. 8, hopper 20 is parked on the other side of work area 18 with valve 42 closed, and platform 46 lowered for the next layer of build material, as indicated by direction arrow 48. Work area 18 is now formed by the first, underlying layer 32 of build material 28. In Fig. 9, valve 42 is open and hopper 20 is moving back over work area 18, as indicated by direction arrow 24, to layer build material 28 on to work area 18 across a gap 36 corresponding to the desired thickness of a second layer 50.

[0024] A PA 12 (polyamide 12) powdered build material 28 may be uniformly layered to a thickness in the range of 100μιη-2ιτιιτι using a choked flow technique implemented with a dispenser such as hopper 20 shown in Figs. 6-9, with vertical sidewalls defining an elongated opening 30 that is 30mm-40mm wide. The thickness of any particular powder layer that can be dispensed uniformly on to a work area will depend on several parameters including, for example, the angle of repose and compressibility of the powder, friction between the powder and the hopper, and the size and shape of the opening. However, for a given set of parameters, the thickness of the layer may be controlled by the size of the gap between the dispenser and the work area.

[0025] The sequence of sections presented in Figs. 10-18 illustrate one example for manufacturing a multi-slice object 52 (shown in Fig. 18) using a layering system 12, such as a system 12 shown in Figs. 3-5 or Figs. 6-9.

Powdered build material 28 is depicted by larger dots in Figs. 10-17 and the thickness of powder layers 32 and 50 greatly exaggerated to help more clearly illustrate the manufacturing process. In Fig. 10, a first layer 32 of powdered build material 28 is dispensed from hopper 20 on to work area 18 on platform 46, for example as described above with reference to Figs. 3-5 and Figs. 6-9. In Fig. 1 1 , a fusing agent 54 is dispensed on to build material 28 in layer 32 in a pattern 56 corresponding to a first object slice, for example with an inkjet type dispenser 16. Pattern 56 for fusing agent 54 is depicted by an area of dense stippling in the figures.

[0026] In some examples, a detailing agent 58 may be dispensed on to build material 28 in layer 32, for example with an inkjet type dispenser 60, as shown in Fig. 12. Detailing agent 58 may be applied before or after fusing agent 54 to inhibit or prevent or enhance fusing targeted areas of build material 28 for improved dimensional accuracy and overall quality of the manufactured object. In the example shown in Fig. 12, detailing agent 58 is dispensed on to an area 62 covering the area where a second object slice will overhang the first slice. Area 62 treated with detailing agent 58 is depicted by light stippling in the figures. Detailing agent 58 may be dispensed on to other areas of build material layer 32 to help define other aspects of the object slice, including interspersed with the pattern of fusing agent, for example, to change the material

characteristics of the slice.

[0027] Although two dispensers 16 and 60 are shown, agents 54 and 58 could be dispensed from dispensers integrated into a single device, for example using different printheads (or groups of printheads) in a single inkjet printhead assembly. In this example, fusing agent 54 includes a light absorbing component to absorb light to generate heat that sinters, melts or otherwise fuses patterned build material. Thus, in Fig. 13 the area of layer 32 patterned with fusing agent 54 is exposed to light 64 from a light bar 14 to fuse build material and form first object slice 66.

[0028] In Fig. 14, a second layer 50 of build material 28 is dispensed on to work area 18 on the underlying in-process structure 68, which includes untreated powdered build material 28, first slice 68 (fused build material), and treated build material in area 62. In Fig. 15, fusing agent 54 is dispensed on to powdered build material 28 in second layer 50 in a pattern 70 corresponding to a second object slice. In Fig. 16, detailing agent 58 is dispensed on to powdered build material 28 in layer 50 in area 72 to help prevent unwanted fusing of build material along the edge of the second slice. In Fig. 17, the area 70 of second layer 50 patterned with fusing agent 54 is exposed to light 64 to fuse build material and form second object slice 74. While distinct first and second slices 66, 74 are shown in Fig. 17, the two slices actually fuse together into a single part. The now fused slices 66, 74 may be removed from platform 46 as a finished object 52 shown in Fig. 18. Although a simple two-slice object 52 is shown, the same processes may be used to form more complex, multi- slice objects.

[0029] Fig. 19 illustrates one example of an additive manufacturing process 100 that uses a choked flow condition to layer powdered build material on to a work area. Referring to Fig. 19, a flow of powdered build material is choked (block 102) and then cleared (block 104). While clearing the choked flow, powdered build material is layered on to a work area (block 106). Then, powdered build material layered on to the work area is fused (block 108), for example as described above with reference to Figs. 1 1 -14. The flow of powdered build material may be choked at block 102, for example, as described above with reference to Fig. 3 by making a hopper 20 and a work area or other blocking surface 18 stationary with respect to one another across a gap 36 that is small enough to choke the flow of powder 28. The choke may be cleared and the powder layered at blocks 104, 106, for example, as described above with reference to Fig. 4 by moving hopper 20 over work area 18 across gap 36. Layering powdered build material at block 106 occurs simultaneously with clearing choked flow at block 104 in process 100 because the mechanism for clearing the choke and layering the powder is the same - relative motion across the gap. Initiating relative motion between hopper 20 and surface 18 across gap 36 clears the choke and simultaneously begins to layer build material 28 on to surface 18. Thereafter, ceasing relative motion will immediately choke off continued flow for gap sizes and corresponding layer thicknesses practical for powder based additive manufacturing, gaps in the range of 100μιη to 2mm for example. [0030] Fig. 20 is a block diagram illustrating a processor readable medium 76 with instructions 78 to use a choked flow configuration to layer powdered build material on to a work area, for example by initiating relative motion between hopper 20 and work area 18 across gap 36 in Fig. 4. Choked flow layering instructions 78 may also include instruction to fuse powdered build material layered on to the work area, for example as described above with reference to Figs. 1 1 -14. A processor readable medium 76 in Fig. 20 is any non-transitory tangible medium that can embody, contain, store, or maintain instructions for use by a processor, and may include for example a hard drive, a random access memory (RAM), a read-only memory (ROM), memory cards and sticks and other portable storage devices. Processor readable medium 76 with choked flow layering instructions 78 may be implemented, for example, in a CAD computer program product, in an object model processor, or in a controller for an additive manufacturing machine.

[0031] Fig. 21 is a block diagram illustrating one example of an additive manufacturing machine 10 implementing a controller 80 with choked flow layering instructions 78. Referring to Fig. 21 , machine 10 includes controller 80, a work area 18, a build material layering system 12, a fusing agent dispenser 16, a detailing agent dispenser 60, and an energy source 14. Controller 80 represents the processor (or multiple processors), the associated memory (or multiple memories) and instructions, and the electronic circuitry and

components needed to control the operative elements of machine 10. In particular, controller 80 includes a memory 82 having a processor readable medium 76 with layering instructions 78, and a processor 84 to read and execute instructions 78. For example, controller 80 would receive control data and other instructions generated by a CAD program to make an object and execute layering instructions 78 as part of the process of making the object.

[0032] Any suitable powdered build material may be used, including for example metals, composites, ceramics, glass and polymers, and processed to make the desired solid object which may be hard or soft, rigid or flexible, elastic or inelastic. Suitable build materials for an additive manufacturing process such as that shown in Figs. 10-18 may include, for example, polyamides and other thermoplastics. A build material may also include a charging agent to suppress or otherwise modify charge characteristics or a flow aid to improve flowability.

[0033] Energy source 14 supplies energy to help fuse build material patterned with a fusing agent. Energy source 14 may be implemented, for example, as an infra-red (IR) or near infra-red light source, a halogen light source, or a light emitting diode. A light source 14 may be a single light source or an array of multiple light sources configured to apply light energy in a substantially uniform manner simultaneously to the whole area of a layer of build material or to apply light energy to just select areas of a layer of build material.

[0034] Suitable fusing agents may include pigments, dyes, polymers and other substances that have significant light or other energy absorption. Carbon black ink and light absorbing color inks commercially known as CM997A, CE039A and CE042A available from HP Inc. may be suitable fusing agents with the appropriate light source.

[0035] Suitable detailing agents may separate individual particles of the build material to prevent the particles from fusing. Examples of this type of detailing agent include colloidal, dye-based, and polymer-based inks, as well as solid particles that have an average size less than the average size of particles of the build material. In one example, a salt solution may be used as a detailing agent. In other examples, inks commercially known as CM996A and CN673A available from HP Inc. may be used as a detailing agent. Suitable detailing agents may act to modify the effects of a fusing agent by preventing build material from reaching temperatures above its fusing point. A liquid that exhibits a suitable cooling effect may be used as this type of detailing agent. For example, when build material is treated with a cooling liquid, energy applied to the build material may be absorbed evaporating the liquid to help prevent build material from reaching its fusing point. Thus, for example, a fluid with a high water content may be a suitable detailing agent. Other types of detailing agent may be used. Examples of a detailing agent to enhance fusing may include plasticizers and surface tension modifiers (that increase the wettability of particles of build material). [0036] "A", "an" and "the" used in the claims means one or more. For example, "a dispenser" means one or more dispensers and "the dispenser" means the one or more dispensers.

[0037] The examples shown in the figures and described above illustrate but do not limit the patent, which is defined in the following Claims.

Claims

1 . A powdered build material layering system for additive manufacturing, the system comprising:

a work area; and

a dispenser to dispense powdered build material on to the work area; where:

one or both of the dispenser and the work area being movable with respect to the other of the dispenser and/or the work area to layer powdered build material on to the work area in a thickness corresponding to a gap between the dispenser and the work area; and

the gap is small enough to choke the flow of powdered build material from the dispenser to the work area when there is no relative motion between the dispenser and the work area.

2. The layering system of Claim 1 , where:

the work area lies in a horizontal plane;

the dispenser is spaced apart from the work area vertically across the gap; and one or both of the dispenser and the work area being movable horizontally with respect to the other of the dispenser and/or the work area to layer powdered build material on to the work area.

3. The layering system of Claim 2, where the dispenser includes:

a receptacle to hold powdered build material;

an elongated opening oriented horizontally along a bottom part of the receptacle through which powdered build material may be dispensed from the receptacle on to the work area; and

a valve operatively connected between the receptacle and the opening, the valve operable between an open position in which powdered build material may flow from the receptacle to the opening and a closed position in which powdered build material may not flow from the receptacle to the opening.

4. The layering system of Claim 3, where one or both of the dispenser and the work area being movable with respect to the other of the dispenser and/or the work area to keep the gap uniform in the direction of motion as powdered build material is dispensed on to the work area.

5. The layering system of Claim 4, where one or both of the dispenser and the work area being movable with respect to the other of the dispenser and/or the work area to keep the gap uniform in the direction of motion and along a length of the opening as powdered build material is dispensed on to the work area.

6. The layering system of Claim 5, comprising powdered build material in the receptacle.

7. A powdered build material layering system for additive manufacturing, the system comprising:

a movable hopper including a receptacle to hold powdered build material and an elongated opening along a bottom part of the receptacle through which powdered build material may be dispensed from the hopper; and

a surface to cover the opening and block a flow of powdered build material from the receptacle on to the surface through the opening when the hopper is stationary over the surface and to not block the flow of powdered build material on to the surface from the receptacle through the opening when the hopper is moving over the surface.

8. The layering system of Claim 7, where the surface is part of a work area.

9. The layering system of Claim 8, where the surface is powdered and/or solidified build material in the work area.

10. The layering system of Claim 7, where the hopper includes a valve operatively connected between the receptacle and the opening, the valve operable between an open position in which powdered build material may flow from the receptacle to the opening and a closed position in which powdered build material may not flow from the receptacle to the opening.

1 1 . A non-transitory processor readable medium including instructions thereon that when executed cause an additive manufacturing machine to:

choke a flow of powdered build material;

clear the choked flow;

while clearing the choked flow, layer the powdered build material on to a work area; and then

fuse powdered build material layered on to the work area.

12. The medium of Claim 1 1 , where the instructions to clear and to layer comprise instructions to move a hopper containing powdered build material over the work area or move the work area under a hopper containing powdered build material.

13. The medium of Claim 1 1 , where the instructions to fuse include instructions to fuse powdered build material in the work area to form a slice and to repeatedly choke, clear, layer, and fuse successively to form multiple slices.

14. The medium of Claim 1 1 , where the instructions to fuse include instructions to: dispense a fusing agent on to layered build material in a pattern corresponding to an object slice;

dispensing a detailing agent on to layered build material; and

exposing layered build material patterned with fusing agent to light to fuse build material and form the object slice.

15. An additive manufacturing machine controller that includes the processor readable medium of Claim 1 1 .