Some additive manufacturing systems, commonly referred to as 3D printers, use manufacturing materials and/or agents to build three-dimensional objects on a layer-by-layer basis.
Various features of the present disclosure will be apparent from the detailed description which follows, taken in conjunction with the accompanying drawings, which together illustrate features of the present disclosure, and wherein:
Three-dimensional, 3D, printing, also referred to as additive manufacturing, rapid prototyping or solid freeform fabrication, is a technology which may be used for manufacturing a variety of objects. Some additive manufacturing systems generate three-dimensional objects through the selective solidification of successive layers of a build material, such as a powdered build material, liquid material or sheet material. Some such systems may solidify portions of a build material by selectively depositing an agent on a layer of build material. Some systems, for example, may use a liquid binder agent to chemically solidify build material where the liquid binder agent is applied.
Other systems, for example, may use liquid energy absorbing agents, or fusing agents, that cause build material to solidify when suitable radiation, such as infra-red radiation, is applied to build material on which a fusing agent has been applied. The temporary application of radiation may cause portions of the build material on which fusing agent has been delivered, or has penetrated, to absorb energy. This in turn causes these portions of build material to heat up above the melting point of the build material and to coalesce. Upon cooling, the portions which have coalesced become solid and form part of the three-dimensional object being generated.
Some example systems may use additional agents, such as detailing agents, in conjunction with fusing agents. A detailing agent is an agent that serves, for example, to modify the degree of coalescence of a portion of build material on which the detailing agent has been delivered or has penetrated. In examples, a detailing agent may produce a cooling effect at portions of the build material on which it is applied, thereby reducing the degree of coalescence upon the application of heat to that portion of build material. In some such examples, the cooling effect produced by the detailing agent may be such that the detailing agent prevents the portion of build material to which it is applied from heating up to a sufficient degree for coalescing of that portion to occur. In an example, a detailing agent may comprise mainly water. In examples, the detailing agent may be applied adjacent to portions of build material to which the fusing agent is applied, for example to control thermal bleed to portions of build material outside of the portion intended to be fused. In some examples, a detailing agent may be applied to portions of build material to which the fusing agent is also applied, for example, in order to control thermal aspects of the fusing of such a portion of build material upon the application of heat.
The production of a three-dimensional object through the selective solidification of successive layers of build material may involve a set of defined operations. An initial process may, for example, be to form a layer of build material from which a layer of the three-dimensional object is to be generated. A subsequent process may be, for example, to selectively deposit an agent, such as a fusing agent and/or detailing agent as described above, to selected portions of a formed layer of build material. In some examples, a further subsequent process may be to supply energy to the build material on which an agent has been deposited to solidify the build material in accordance with where the agent was deposited.
As described above, the temporary application of energy may cause portions of the build material on which an agent has been delivered, or has penetrated, to heat up above the point at which the build material begins to coalesce. This temperature may be referred to as the fusing temperature. Upon cooling, the portions which have coalesced become solid and form part of the three-dimensional object being generated. These stages may then be repeated to form a three-dimensional object. Other stages and procedures may also be used with this process.
A suitable fusing agent may be an ink-type formulation comprising carbon black. Such an ink may additionally comprise an absorber that absorbs the radiant spectrum of energy emitted by the energy source 106. In one example where the fusing agent is an ink-type formulation comprising carbon black, the fusing agent may comprise the fusing agent formulation commercially known as V1Q60A “HP fusing agent”, available from HP Inc. In one example such an ink may additionally comprise a near infra-red light absorber. In one example such a fusing agent may additionally comprise a visible light absorber. In one example such an ink may additionally comprise a UV light absorber. Examples of inks comprising visible light enhancers are dye based colored ink and pigment based colored ink, such as inks commercially known as CE039A and CE042A available from HP Inc.
The support member 104 may be a fixed part of the additive manufacturing system 100 or may not be a fixed part of the additive manufacturing system 100, instead being, for example, a part of a removable module.
The agent distributor 102 may be a printhead, such as thermal print-head or piezo inkjet printhead. An example printhead may have arrays of nozzles, in other examples, the agents may be delivered through spray nozzles rather than through printheads. In some examples the printhead may be a drop-on-demand printhead. in other examples the printhead may be a continuous drop printhead. The agent distributor 102 may be an integral part of the additive manufacturing system 100 or may be user-replaceable. The agent distributor 102 may extend fully across the support member 104 in a so-called page-wide array configuration, in other examples, the agent distributor 102 may extend across a part of the support member 104. The agent distributor 102 may be mounted on a moveable carriage to enable it to move bi-directionally across the support member 104 along the illustrated y-axis. This enables selective delivery of fusing agent across the entire support member 104 in a single pass, in other examples the agent distributor 102 may be fixed, and the support member 104 may move relative to the agent distributor 102.
In some examples, there may be an additional agent distributor 110, in this example being a detailing agent distributor. The detailing agent may be selectively applied to portions of the build material which are not to be solidified and may be applied by the detailing agent distributor 110 in the manner described above for the fusing agent distributor. According to one example, a suitable detailing agent may be a formulation commercially known as V1Q61A “HP detailing agent” available from HP Inc. The fusing agent distributor 102 and the detailing agent distributor 110 may be located on the same carriage, either adjacent to each other or separated by a short distance. In other examples, two carriages each may contain fusing agent distributor 102 and detailing agent distributor 110.
The additive manufacturing system 100 further includes a build material distributor 112 to provide, e.g. deliver or deposit, successive layers of build material on the support member 104. Suitable build material distributors 112 may include a wiper blade and a roller. Build material may be supplied to the build material distributor 112 from a hopper or build material store. In the example shown the build material distributor 112 moves along the y-axis of the support member 104 to deposit a layer of build material. A layer of build material is deposited on the support member 104, and subsequent layers of build material are deposited on a previously deposited layer of build material. The build material distributor 112 may be a fixed part of the additive manufacturing system 100, or may not be a fixed part of the additive manufacturing system 100, instead being, for example, a part of a removable module.
In the example of
The energy source 106 applies energy 114 to build material to cause a solidification of portions of the build material, for example to portions to which an agent, e.g., fusing agent, has been delivered or has penetrated. In some examples, the energy source 106 is an infra-red radiation source, for example a near infra-red radiation source. The energy source 106 may comprise radiating elements, such as infra-red lamps. In an example, the energy source 106 may comprise a halogen radiation source. In examples, the energy source 106 is a scanning radiation source which is mounted on the moveable carriage (not shown). For example, the energy source 106 may apply energy to a strip of the whole surface of a layer of build material. In these examples the energy source 106 may be moved or scanned across the layer of build material such that a substantially equal amount of energy is ultimately applied across the whole surface of a layer of build material. In examples, the energy source 106 applies energy in a substantially uniform manner to the whole surface of a layer of build material, and a whole layer may have energy applied thereto simultaneously, which may increase the speed at which a three-dimensional object may be generated. In yet other examples, the energy source 106 may apply a variable amount of energy as it is moved across the layer of build material, for example in accordance with agent delivery control data. For example, the controller 108 may control the energy source 106 to apply energy to portions of build material on which fusing agent has been applied.
The energy source 106 includes a lamp or another radiating element to add or supply energy to the layers of build material. Two radiating elements, three radiating elements, or any number of radiating elements may be used side-by-side to increase the power per unit area irradiated onto the build material. Some lamps used as a radiating element in energy source 106 may include tungsten and to avoid blackening of the lamp due to tungsten condensation the lamp is operated above 300° C. Radiating elements of the energy source 106 used to fuse build material in examples described herein may be considered to act as a black body which is held at a constant, uniform temperature, so that the radiation has a spectrum and intensity depending on the temperature of the body in accordance with Planck's law, i.e., as the temperature decreases, the peak of the black-body radiation curve moves to lower intensities and longer wavelengths. In examples, portions of build material having a fusing agent applied thereto may have high absorptivity at wavelengths at which emission from the energy source peaks. Portions of build material to which a fusing agent has not been applied may absorb less of the radiation from the energy source 106. Where the energy source comprises lamps having filaments at a particular temperature, maintaining the filaments at that temperature, e.g. by applying a constant power to the radiating elements, may allow the range of wavelengths of radiation emitted by the source to be substantially constant and therefore allow control of the heating of portions of the build material.
Examples provide a reflector assembly for the energy source 106, which may for example be a scanning energy source for applying radiation to a layer of build material, as described above. The use of a reflector assembly may increase a proportion of energy irradiated from the energy source 106 which is incident upon the layers of build material on the support member 104.
The first reflecting section 250 is shown in perspective view in
In examples, each reflecting section 250, 260 is elongate and is substantially symmetrical about a central longitudinal axis of the reflecting section 250, 260. In the examples shown in the figures the reflecting surface 251 has a cross-section which is substantially elliptical in profile. That is, in this example the reflecting surface 251 extends substantially along the profile of a portion of an ellipse. The reflecting surface 251 may be made up of a plurality of straight portions, perpendicular to the direction L, substantially following the profile of an ellipse, or in another example may comprise a curved portion following the profile of an ellipse. In one example, the reflecting surface 251 is formed of two straight sections 251a and a curved section 251b joining the two straight sections 251a. In an example, the straight sections 251a extend downward at an angle of between 35 and 40° from one another and may in one example extend at around 38° from one another. In examples, the shape of the reflecting surface 251, e.g. whether the reflecting surface 251 comprises portions formed of straight sections of reflecting surface, may be chosen to provide for ease of manufacturing. The reflecting section 250 has a body 252 and has a recess 254 on its upper face. In examples, the reflecting surface 251 may be concave in shape and have a profile which is not elliptical, for example, the reflecting surface 251 may be hyperbolic. Upper corners 255 of the reflecting section 250 are beveled along the length L of the reflecting section 250. In
In the reflector assembly 200, the first reflector 210 comprises a housing 213 in which the first reflecting section 250 is mounted. Similarly, the second reflector 220 comprises a housing 223 in which the second reflecting section 260 is mounted. Each housing 213, 223, has mounting features 213a, 213b which correspond with slots 253a, 253b, 253c on the sides of the reflecting sections 250, 260. This allows each reflecting section 250, 260 to be mounted in the housing 213, 223. For example, each reflecting section 250, 260 may be removably mounted the respective housing 213, 223, for example by sliding each reflecting section 250, 260 into one of the housings 213, 223, along the direction L shown in
Examples provide for each reflector 210, 220 to comprise a plurality of reflector sections, such as reflector sections 250, 260, arranged end-to-end along the direction L. For example, the first reflector 210 and the second reflector 220 may each comprise two or more reflector sections 250, 260 arranged end-to-end along the direction L. As such, an elongate reflector made up of a plurality of stacked reflector sections 250 may be provided. This may provide for individual replacement of reflector sections 250, 260 in the reflector assembly 200. Furthermore, this can provide for a reflector assembly 200 of a particular length to be made up of separate reflector sections, such as reflector sections 250, arranged end-to-end along their lengths L.
Now turning to
In accordance with further examples, the apparatus 300 comprises an outer housing 330 for containing the reflector assembly 200 and radiating elements 51, 52. In the example shown in
Examples also provide for a reflector assembly which comprises a different number of reflectors to the two reflectors of the reflector assembly 200. As an example,
Examples provide for a reflector assembly which has a structure which can reduce the impact of back-reflection of radiation from the layer of build material on the uniformity of energy per unit area absorbed by parts of the build material. Referring now to
The layer of build material 150 comprises a first portion 152 of build material to be solidified and a surrounding portion 154 of build material which is not to be solidified. For example, the first portion 152 may be a portion to be solidified to form a 3D printed part while the surrounding portion 154 is the layer of powder surrounding the 3D printed part in the build layer 150. The first portion 152 of the layer of build material 150 is in this example more absorptive of radiation emitted from the apparatus 400 than the surrounding portion 154 of build material. That is because, as described above, an agent which increases absorption with respect to radiation applied by the radiating elements 51, 52, 53, i.e. fusing agent, is applied to the first portion 152 so that radiation may be absorbed by the first portion 152 to heat and thereby solidify the first portion 152. In an example, the fusing agent may be carbon black and the first portion 152 is consequently black after application of the fusing agent, while the surrounding portion 154 of build material comprises a substantially white powder. As such, with respect to the radiation incident on the build layer 150 from the energy source apparatus 500, the absorptivity of the first portion 152 is larger than the absorptivity of the surrounding portion 154, and correspondingly, the reflectivity of the surrounding portion 154 is larger than the reflectivity of the first portion 152.
Example reflector assemblies described herein, such as the reflector assembly 400, when used as shown in
The radiating elements 51, 52, 53 may be placed close the ceramic reflecting surfaces 251 which may provide for a reflecting geometry which achieves the above-described effect of substantially containing reflected radiation to the area beneath each reflector 410, 420, 430. The use of ceramic reflecting sections, such as ceramic reflector section 250, may allow the radiating elements 51, 52, 53 to be placed in close proximity with the reflecting surfaces 251, for example, without active cooling of the ceramic reflector sections. An example ceramic reflector section 250, due to its thermal and reflective properties, may maintain its shape at high temperatures which result from a radiating element being located in close proximity with the reflecting surface 251, and continue to act as an effective reflector at such temperatures without the use of active cooling. Furthermore, the use of a described arrangement comprising a plurality of ceramic reflector sections 250 provides for a compact apparatus 500 comprising the reflector assembly 400 and radiating elements 51, 52, 53, which can be located close to the build layer 150 in use, which may contribute to controlling the reflection of radiation as described above. The absence of active cooling for such a reflector assembly 400 may also provide for a compact apparatus 500, for example an apparatus which is moveable above a layer of build material 150.
As mentioned above, in an example reflector assembly 500 and in other example reflector assemblies described herein, radiating elements 51, 52, 53 may be placed close to the respective reflecting surface 251 of each reflector since the reflecting surface 251 is part of a ceramic reflector section 250. In examples described herein, for example where the radiating elements 51, 52, 53 are lamps, each reflecting surface 251 of the reflectors 410, 420, 430 may be at a distance of from 1 mm to 5 mm, or from 2 mm to 4 mm from the radiating elements 51, 52, 53. For example, each reflecting surface 251 may be around 2.5 mm from a surface of one of the radiating elements 51, 52, 53. In the example shown in
In examples, reflecting sections, such as reflecting section 250, as mentioned above, are formed of a ceramic material and may be formed, for example, by ceramic injection molding. Example ceramic reflecting sections may be formed of zirconia-toughened alumina, ZTA.
Examples of reflector assemblies in the present disclosure have been described in the context of additive manufacturing using a bed of build material. It should be appreciated that an example reflector assembly according to the present disclosure, such as reflector assembly 200 or 400, may be used in other types of additive manufacturing process, such as a process that uses lamps for melting, such as high-speed sintering, or a process of heating, e.g. to perform a thermal curing operation. Examples described herein may be employed in a 2D or 3D printing operation.
The preceding description has been presented to illustrate and describe examples of the principles described. This description is not intended to be exhaustive or to limit these principles to any precise form disclosed. Many modifications and variations are possible in light of the above teaching. It is to be understood that any feature described in relation to any one example may be used alone, or in combination with other features described, and may also be used in combination with any features of any other of the examples, or any combination of any other of the examples.
Filing Document | Filing Date | Country | Kind |
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PCT/US2018/057925 | 10/29/2018 | WO | 00 |