In three-dimensional printing processes, three-dimensional (3D) objects can be built by fusing powder material. The powder material can be fused, for example, by using a fusing agent which evaporates during the printing process. When the printing process is finished, a container may contain the object of fused powder which is surrounded by non-fused powder.
After the printing process the container can be transferred to a cleaning and powder recycling station which may perform a cleaning process to separate and clean the three-dimensional object from the surrounding powder. A certain amount of the separated powder material can be recovered for a following 3D printing process.
Referring to
In the present disclosure, an “amount” may correspond to the weight of a material or a mixture of materials or the weight of an object which is built of a material. Further, an “amount” may also correspond to the volume of a material or a mixture of materials or the volume of an object which is built of a material. Accordingly, an amount corresponds to a quantity which may be defined in terms of weight and/or volume. If the density is known, the weight can be obtained from the volume and vice versa.
The first amount A1 corresponding to the content of the container 10 can be obtained, for example, by weighing the filled container of
Referring to
A1=A2+A3 (I)
After separating the amount of non-fused powder corresponding to the second amount A2 and the object 16 having residual powder material corresponding to the third amount A3 during the cleaning process C1, the non-fused powder corresponding to the second amount A2 can be recovered. The recovered powder of the second amount A2 may be recycled, i.e. it may be used in a following 3D printing process for printing another 3D object.
The second amount A2 may be derived, for example, by directly weighing the amount of separated non-fused powder, which is shown at the bottom left in
A2=A1−A3 (I′)
The third amount A3 may be obtained in a similar way to the second amount A2, namely by directly weighing the object 16 having residual powder material attached or by weighing the amount A2 and subtracting the weighing result from the amount A1, for example. That is, A3 may be obtained from A1 and A2 based on relationship (I) as:
A3=A1−A2 (I″)
Referring to
A3+A4=A5+A6 (II)
The next cleaning process C2 may be more intense than the cleaning process C1, such that material may be removed from the object which could not be removed by the previous cleaning process C1. For example, a stronger cleaning force may be applied to the object. The next cleaning process C2 may comprise the use of air pressure, movement, vibration, a blasting process or a combination thereof. The cleaning agent may be sand, a liquid, another abrasive or non-abrasive cleaning agent, or a combination thereof. For example, the next cleaning process C2 may comprise a blasting process which uses an abrasive cleaning agent, such as a sandblasting process which uses sand. In some examples, the amount of cleaning agent corresponding to the fourth amount A4 is obtained by weighing or measuring the amount of cleaning agent 18 which is used in the next cleaning process C2 before the corresponding cleaning process takes place. In other examples, the fourth amount A4 is obtained based on the cleaning time t and on the amount At of cleaning agent 18 which is used per time, i.e. by A4=t·At.
The amount of the mixture 22 corresponding to the sixth amount A6 may correspond to the sum of the residual powder material which was attached to the cleaned object 20 and which has been removed from the cleaned object 20 and the amount of cleaning agent 18 used. That is, in an ideal case, when no material is lost, the amount of the mixture 22 corresponding to the sixth amount A6 can be determined based on the amounts A3, A4 and A5 and on the above relationship (II):
A6=A3−A5+A4 (II′)
However, even in non-ideal cases, e.g. when a certain portion of material is lost and not considered, the above relationships (I) and (II) may allow for a sufficiently precise estimation of an amount or of a process parameter. The reason is, that for the processes referred to herein, the above relationships (I) and (II) may consider the flow of the major portion of material such that the unconsidered material loss may be comparatively small.
The amounts A5 and A6 may be directly obtained by weighing. Alternatively, at least one of the amounts A1 to A6 can be obtained based on other amounts of A1 to A6 by using at least one of the above relationships (I) and (II).
Referring to
The amount A7 may be determined, for example, by weighing the material which is recovered, after it has been removed from the treated mixture 24. In other examples, the seventh amount A7 corresponding to the material which may be recovered can be determined based on the height of the plane 28 along the separation direction 26. If the treated mixture 24 is confined in a defined and known volume of a particular shape, e.g. in a known recovery container, the volume and hence the amount A7 can be readily obtained from the height of the horizontal plane 28. For example, if the treated mixture 24 is confined in a cylindrical container and the plane 28 has a height, such that the plane 28 is located in the middle of the container, then the seventh amount A7 corresponds to half of the volume of the cylindrical container.
Likewise to the seventh amount A7 also the sixth amount A6 corresponding to the amount of the mixture may be determined based on a height, namely based on the height of the material of the mixture in the container. This height of the material in the container may be determined by a mechanical sensor using a moving part that changes its position according to the height of the material, such as a buoy. In other examples, an IR sensor is used to determine the height of the material in the container. For determining the height of the material in the container at least one of a mechanical sensor, such as a pressure sensor or a capacitive sensor, and an inductive sensor can be used. The sensor may be disposed on the side of the container.
The powder material, which in the example of
A8=A6−A7−A4 (III)
In another example, the eighth amount A8 corresponding the powder material wastage may be directly determined by weighing the remaining amount of the treated mixture 24 after the amount of powder material which can be recovered, namely A7, and the amount of used cleaning agent, namely A4, have been removed. If no material is lost in previous process stages or during powder recovery and if the remaining amount of the treated mixture 24 does not comprise any cleaning agent 18, the weighed eighth amount A8 corresponds exactly to the wastage of powder material. In some examples, a certain amount of material which is not taken into account for the determination of A8 may be lost in a previous or later process stage. Further, the remaining amount of the treated mixture 24 still may comprise a certain amount of cleaning agent. However, even in these examples the determination of the powder material wastage may be sufficiently precise, if the other losses or the amount of cleaning agent in the remaining amount of the treated mixture 24 are small compared to the other absolute amounts.
Based on at least two of the amounts A1 to A8, different process parameters of the 3D printing process and subsequent cleaning and recovery processes can be determined. For example, the process parameter of the powder wastage, namely A8, resulting for the combined processes of 3D printing, separating the object from the surrounding non-fused powder material, cleaning the object and recovering of powder material can be estimated based on the above relationship (III) using the amounts A6, A7 and A4. This estimation of the powder wastage, namely A8, based the amounts A6, A7 and A4, may correspond to an exact determination, if no powder material is lost except for the not recovered powder of the mixture and if the recovered amount above the plane 28, namely A7, is free of cleaning agent. If not more than a comparatively small amount of powder is lost, besides the not recovered powder wastage in the mixture or, if the powder which is recovered from the mixture, namely A7, comprises not more than a small amount of cleaning agent, the determination of A8 may be a precise estimation of the powder material wastage.
Based on at least two of the amounts A1 to A8, different process parameters of the 3D printing process and subsequent cleaning and recovery processes can be determined. For example, the process parameter of the powder consumption of the combined processes of 3D printing, separating the object from the surrounding non-fused powder material, cleaning the object and recovering of powder material can be determined. The powder consumption corresponds to the sum of the amount of fused powder of the cleaned object 20, namely A5, and the amount of powder material wastage, namely A8. Accordingly, the powder consumption may be determined based on A5 and A8. In one example, A5 and A8 are directly obtained, e.g. by weighing, and the powder consumption PC is derived by determining the sum of A5 and A8, i.e. by PC=A5+A8. In other examples the powder consumption can be determined based on other amounts A1 and A8, e.g. by using at least one of the following relationships:
A1=A2+A3 (I)
A3+A4=A5+A6 (II)
A6=A4+A7+A8 (III)
A3−A5=A7+A8 (IV)
A1−A2+A4=A5+A6 (V)
The relationships (I), (II) and (III) can be derived from the illustrations of
By combining relationship (II) and PC=A5+A8, the powder consumption PC can be determined based on a group of the amounts A3, A4, A6 and A8, namely as
PC=A3+A4−A6+A8.
By combining relationship (III) and PC=A5+A8, the powder consumption PC can be determined based on a group of the amounts A4, A5, A6 and A7, namely as
PC=A5+A6−A7−A4.
By combining relationship (IV) and PC=A5+A8, the powder consumption PC can be determined based on a group of the amounts A3 and A7, namely as
PC=A3−A7.
By combining relationship (V) and PC=A5+A8, the powder consumption PC can be determined based on a group of the amounts A1, A2, A4, A6 and A8, namely as
PC=A1−A2+A4−A6+A8.
Based on at least two of the amounts A1 to A8 which may be determined as previously explained, also other process parameters may be derived, such as the amount of utilized clean ing agent (e.g. as A4=A5+A6−A3), the amount of recovered powder RP (e.g. as RP=A2+A7), the weight of the cleaned object (e.g. as A5=A3+A4−A6), the amount of residual attached powder material AP (e.g. as AP=A3−A5). All of these parameters may be provided to a user for process control and monitoring purposes or for the purpose of optimization, wherein said optimization may be based on the knowledge of at least one actual parameter value and/or its development over time.
By shifting or adjusting the height of plane 28 upwards or downwards along the separation direction in
The improvement of the material quality of the amount A7 of powder recovered from the mixture may reduce the amount of recovered material A7 and may increase the amount of powder wastage A8 and vice versa. For example, if the object has rather rough structures which tolerate a lower quality of powder material, then for optimizing the process in terms of material exploitation, the minimum quality threshold may be reduced to achieve a minimum amount of powder wastage A8, which still is sufficient to provide a specific quality of the object, such that the powder consumption may be minimized for saving costs.
Referring to
There are other examples for obtaining the amount A4 of cleaning agent 18. For example, the amount A4 may be obtained by using the height of the plane 30 along the separation direction in a recovery container (not shown) to determine the volume of the accumulated cleaning agent 18 below plane 30, similar as explained above for the amount A7 with respect to the plane 28. According to another example, the amount A4 of material below plane 30 is removed and obtained by weighing.
In some examples, the separation after the treatment process T may not be perfectly complete, such that the material below plane 30 might not correspond to 100% of the cleaning agent 18 and the material above plane 30 might not be completely free of cleaning agent 18. In such examples, the obtained amount A4 may correspond to a sufficiently precise estimation of the amount of utilized cleaning agent 18, if the separation is sufficient and if no cleaning agent or a comparatively small amount of cleaning agent is lost outside the mixture. In the present disclosure the accuracy of an estimation may depend on the degree of separation after the treatment process, on the existence of unaccounted material losses and on the relative extent of the unaccounted material losses. Because the material losses or other constituents which are not considered by the above relationships may be relatively small, the separation can be adjusted to a degree which allows for an estimation which is sufficiently precise. For example, small portions of powder or cleaning agent may be lost when transferring the substances from one container to another. These may be neglected. As another example, the powder material can be fused by using a fusing agent which evaporates fully or to a large extend during the printing process. Any remaining parts of the fusing agent within the fused object or powder may be so small that they can be neglected and still obtain a precise estimation.
Some or all of the above process parameters may be monitored and used for adjusting the minimum quality threshold in order to obtain a corresponding process profile, wherein different process profiles may fulfill different needs in terms of quality of the powder material, such as a specific particle size, and/or in terms of consumption/wastage of powder material.
In some examples, the plane 28 corresponding to the minimum quality threshold in
In some examples the cleaning process C2 comprises sandblasting and the cleaning agent 18 comprises sand with a particle size of about 100 μm or more. In some of the examples, the minimum quality threshold corresponds to a powder particle size of about 50 μm. Additionally or alternatively, the cleaning agent 18 may also comprise a liquid.
The material property within the treated mixture 24, based on which the height of the plane 28 corresponding to the minimum quality threshold can be adjusted, can be measured. The measurement of the material property can be performed, for example, with a particle size sensor, a liquid-powder range sensor or a liquid-powder distance sensor, or by a combination of them.
Referring to
Referring to
As shown in the example of
In the cleaning unit 52, the object 16 having residual powder material attached may be cleaned from the residual powder material by using a fourth amount A4 of a cleaning agent 18, such that a fifth amount A5 corresponding to fused powder material of the cleaned object 20 and a sixth amount A6 corresponding to a mixture 22 of the cleaning agent 18 and the residual powder material may be obtained.
The mixture 22 may be transferred to the treatment unit 56. In the treatment unit 56, the mixture 22 may be treated, within the recovery container 54, to separate the residual powder material from the cleaning agent 18 to an increasing degree along a separation direction 26, wherein the particle size of the residual powder material may decrease with increasing distance from the cleaning agent 18.
After the treatment process, a seventh amount A7 of powder material may be removed from the treated mixture 24 and transferred to the recovery unit 58, as illustrated in
In the example of
In the system 46, different amounts can be determined in the different units, for example by weighing. In the example of
As illustrated in
Filing Document | Filing Date | Country | Kind |
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PCT/EP2015/058061 | 4/14/2015 | WO | 00 |