Feeding mechanisms for 3D printers

In order to have ensure a proper dosing of a 3D printing system, it is disclosed a feeding mechanism for feeding build material to a surface that comprises: a receptacle to receive build material; and an outlet of the build material having a substantially quadrilateral opening with a first dimension and a second dimension orthogonal to one another; the outlet further comprising a third dimension orthogonal to the first dimension and the second dimension defining the height of the outlet, and the feeding mechanism being to selectively feed build material from the receptacle through the outlet onto a surface as the feeding mechanism moves along a travel direction over the surface, being such travel direction parallel to the first dimension of the outlet, the feeding mechanism further comprising an actuator to modify the magnitude of at least one of the second dimension or the third dimension outlet.

BACKGROUND

Additive manufacture systems, commonly known as three-dimensional (3D) printers, enable objects to be generated on a layer-by-layer basis. Powder-based 3D printing systems, for example, form successive layers of a build material in a printer and selectively solidify portions of the build material to form layers of the object or objects being generated.

3D printing systems may comprise mechanisms for accurately measuring the amount of powder to be used in each of the successive layers in order to help ensure that each layer has an appropriate amount of powder and that the conditions of the system, such as layer temperature, are suitable.

DETAILED DESCRIPTION

Referring toFIGS. 1A and 1B, schematic views are shown of part of a 3D printing system according to one example.

In particular,FIGS. 1A and 1Bshow, respectively, isometric and top views of a 3D printing system100comprising a spreader104, attached to a carriage103. Furthermore, a build surface105is shown wherein a determined amount of build material is to be spread by the spreader104to generate a layer of build material, either over the build surface105or over a previously processed layer of build material. The build material is spread by means of the spreader104mounted on a first carriage103which is shown in the figures as a roller but can be any device capable of conveying powdered material such as, for example, a wiper.

In one example, the build surface105may be part of a build unit101that forms a build chamber. In one example the build unit may be removable from the other components of the 3D printing system. The 3D printing system100forms 3D objects within the build chamber as it selectively solidifies portions of each formed layer of build material. After each layer of build material is selectively solidified the build surface105is lowered, along the z-axis, to enable a new layer of build material to be formed thereon. Depending on the particular 3D printing system used, each layer of build material formed may have a height, for example, in the region of about 50 to 120 microns.

Furthermore, the system may comprise at least one auxiliary platform that can be used for support processes, such as the dosing of the build material or the processing of excess build material. In particular, the system ofFIGS. 1A and 1Bcomprise: a dosing surface102adjacent to the build surface105wherein material is prepared for an accurate dosing and pre-heating; and a recycling chamber300adjacent to the build surface105on the opposite side of the dosing surface102wherein, for example, excess material may be transferred for its reuse or disposal.

Firstly, a pile of build material is transferred from a storage to the dosing surface102by appropriate means, such as a feed mechanism106. Since build material may be powdered or particulate material, the measurement of the amount of build material that is actually transferred from the storage to the dosing surface102may be difficult to accurately quantify. It may also be difficult to uniformly locate over the dosing surface102. This may be further complicated by the fact that build material may have to be transferred rapidly so that its transfer does not affect the processing time of each layer of build material.

In an example, a pile of build material may be laid along the Y axis of the dosing surface102, by the feed mechanism106. The build material may be fed to the dosing surface102, for example, by a choked flow hopper that is moved along a laying axis D1over the dosing surface102by means of a second carriage107. The build material may be fed to the dosing surface102, for example, by gravity.

The dosing surface102may comprise pre-heating mechanisms below and/or over the dosing surface102. Therefore, it is useful to uniformly lay the build material over the dosing surface and to accurately determine the amount and height of the layer of build material so that operations like, for example, the pre-heating before the selective solidification are performed adequately.

Once a determined amount of build material has been fed to the dosing surface102and the pre-processing operations, for example, the preheating has been performed, a sweep may be performed by the spreader104together with the first carriage103along a second axis D2to spread at least part of the build material over the build surface105. Then, the build material spread over the build surface105may be selectively solidified by a printing mechanism and a new pile of build material may be transferred to the dosing surface102by the feeding mechanism106wherein the feeding of the dosing surface102is repeated for a new layer of build material, for example, once the carriage has returned back to its starting position on the left as shown inFIGS. 1A and 1B.

The motion of the first carriage103and the second carriage107are controlled, in an example, by means of a motion controller108that may be connected to a main processing unit. Also, the first carriage103and the second carriage107may move bi-directionally along a linear trajectory thereby increasing the processing speed and reducing the computational cost on the motion controller108.

FIG. 2shows a schematic process of a feeding mechanism106. The feeding mechanism106comprises an inlet1062for receiving build material10and an outlet for feeding a layer build material to the dosing surface102. The outlet has a quadrangular opening that, in this particular case, is a rectangular opening1060, in order to feed a substantially rectangular layer of build material on the dosing surface102. The rectangular opening1060may comprise a closing mechanism such as to selectively cover at least part of the opening.

In a first section201, the feeding mechanism106is located at a first position for receiving build material10, for example, in a receptacle of the feeding mechanism106. In a second section202, the feeding mechanism is shown while it moves linearly along a laying axis D1in a first direction and the rectangular opening1060is open such as to feed a layer of build material10on the dosing platform102as the feeding mechanism106follows the laying axis D1. In this example, the layer of build material10that is fed to the dosing surface102has, in its plan view, a quadrangular shape, in particular, rectangular with a layer width defined by the width W of the rectangular opening1060.

The result of the feeding of the dosing surface is shown in the third section203. Therein, a layer of build material10is laid with a width W equal to the width of the rectangular opening1060and a thickness h that may be determined by height of the outlet, as will be described with reference toFIG. 3. A substantially uniform layer is generated wherein operations, such as, e.g., pre-heating are performed more efficiently, for example since the amount of powder to heat along the length of the pile is substantially constant.

In an example, the 3D printing system100comprises a preheating mechanism (not shown) to induce heat from below the dosing surface102. Additional preheating mechanisms may be incorporated, e.g., from above the dosing surface102as to preheat the upper portion of the layer of build material10.

FIG. 3shows a schematic example of a feeding mechanism106. In this example, the feeding mechanism106comprises a receptacle1063with a top side1062that may be selectively open as to receive build material and a bottom side1061. In an example, the bottom side1061may be open as to allow build material to exit the receptacle. The feeding mechanism106may comprise an outlet connected to the open bottom side1061as to selectively allow build material to exit the receptacle1063and go through the outlet so that the build material is fed to a surface, for example, a dosing surface102.

In the example ofFIG. 3, the outlet comprises a first end wall1064and a second end wall1065that have projecting surfaces below the bottom side1061that may cover at least part of the bottom surface1061of the receptacle1063. The end walls thereby define the rectangular opening1060for build material to pass through. In this example, the width W of the rectangular opening1060is defined by the distance between the projecting surfaces of the end walls and its length by the length LRof the receptacle1063.

In a further example, the feeding mechanism106may comprise an actuator1065coupled to at least one of the first end wall1064or the second end wall1065. The actuator may comprise displacement means as to move the first end wall1064and/or the second end wall1065in a direction orthogonal to the laying axis D1. The actuator1065thereby performs a dimensioning function in directions other than the laying axis D1.

The dimensioning of the outlet is particularly relevant in the context of the feeding mechanism106because it provides the feeding mechanism106, on one hand, with a fine-tune capability on the dosing and, on the other, with flexibility for using a feeding mechanism that can feed layers of several widths on the dosing surface102.

Since the width of the layer of build material on dosing surface102determines the amount of build material that is to be used in a particular 3D printing process, having a feeding mechanism106with the capability to determine the width of the build material to be fed to the dosing surface in a single pass is a fast mechanism with low computational cost to define the amount of build material that is used for each layer of the 3D printing process.

In an example, the actuator1065may modify the height H of the outlet. For explanatory purposes and in order to maintain the references within the feeding mechanism, the height H of the outlet will be considered to be the distance between the bottom surface1060of the receptacle1063and the opening1061. In other examples, the height H can likewise be measured relative to the dosing surface102.

In a further example, the feeding mechanism106may comprise an actuator and mechanical interconnections between end walls so that an action by the actuator is transferred to the first and the second end walls and displaces their position. For example, the first end wall1064and the second end wall1065may be mechanically coupled so that an action by the actuator1065to reduce the width of the output reduces the relative distance between the end walls, e.g., by moving both of them towards each other. Furthermore, the first end wall1064and the second end wall1065may be mechanically coupled so that an action by the actuator1066to modify the height of output is transferred by the mechanical coupling to the end walls so that both of them are simultaneously displaced by the same distance.

In another example, the feeding mechanism106may comprise several actuators. The feeding mechanism may comprise one actuator1065for each of the end walls or may comprise two actuators for each end wall, e.g., one for modifying the height H of the outlet and one for modifying the width W of the outlet.

FIG. 4shows a front view of the feeding mechanism106ofFIG. 3. As mentioned above, the feeding mechanism106may comprise end walls that modify the dimension of the rectangular opening1061. In an example, the feeding mechanism106may comprise an actuator1065to modify the width W of the outlet, i.e., the opening1061by moving in a horizontal direction by a horizontal distance DW. In another example, the feeding mechanism106may comprise an actuator1065to modify the height H of the outlet by a vertical distance DH. In a further example, the feeding mechanism106may comprise one or more actuators1065to modify the height H and the width W of the outlet.

The actuator1065may be a mechanical actuator, e.g., a lever or any other type of manual mechanism. Alternatively, automatic (or semi-automatic) actuators are envisaged wherein the actuator may comprise a pneumatic or hydraulic mechanism to move the end walls or may be an electric actuator comprising, e.g., a solenoid to move the end walls. In a further example, the actuator1065may be a hybrid actuator, for example, a pneumatic actuator wherein the control signal is an electric signal.

Automatic or semi-automatic actuators1065comprise an outlet controller1067that issues a control signal that is to be received by the actuators and, in response to such control signal, move the end walls.

An automatic actuator is to be understood as an actuator1065that is configured to act with no interaction by a user (e.g., based on measurements or on a previous calibration) and a semi-automatic actuator is to be understood as an actuator that, upon receipt of a command by a user (e.g., by issuing a signal or inputting a value on the controller1067), performs an action.

The outlet controller1067may, for example, be configured to determine a quantity of powder to be delivered based on a pre-determined or user-selectable input (e.g. a layer height, material type, etc.). Further, the controller1067may be configured to modify the size or height of the opening, e.g., by moving the sidewalls horizontally or vertically. In another example, the controller1067may be configured to provide a pile of powder having the chosen width W and thickness h.

In essence, it is disclosed a feeding mechanism for feeding build material to a surface that comprises:a receptacle to receive build material; andan outlet of the build material having a substantially quadrilateral opening with a first dimension and a second dimension orthogonal to one another;
the outlet further comprising a third dimension orthogonal to the first dimension and the second dimension defining the height of the outlet, and the feeding mechanism being to selectively feed build material from the receptacle through the outlet onto a surface as the feeding mechanism moves along a travel direction over the surface, being such travel direction parallel to the first dimension of the outlet, the feeding mechanism further comprising an actuator to modify the magnitude of at least one of the second dimension or the third dimension outlet.
In an example, the feeding mechanism is coupled to a motor to move linearly along the travel direction. This bidirectional linear movement along a laying axis allows for simpler programming on the controller and lower computational cost on the control algorithms.

The actuator may be configured to modify the second dimension and the third dimension of the outlet. That is, the width and the height of the outlet, which imply, respectively, a change in the width and the thickness of the layer of build material to be fed to the dosing surface.

In an example, the outlet comprises a first end wall and a second end wall separated by a distance defining the second dimension of the outlet, being the actuator to reduce the distance between the first end wall and the second end wall, i.e., the width of the outlet.

In a further example, a first end wall and a second end wall located at the same height, being the actuator to modify by the same magnitude the height of the first end wall and the second end wall. Also, the first end wall and the second end wall may be mechanically coupled as to move jointly.

The feeding mechanism may provide a choked-flow mechanism.

Furthermore, it is disclosed a 3D printing system that comprises:a carriage to move over a surface at a determined vertical separation distance; anda feeding mechanism to jointly move with the carriage and to selectively feed build material to the surface;
wherein the feeding mechanism comprises a receptacle to store build material and an outlet of the build material, the outlet having a quadrangular opening and having at least a first end wall and a second end wall defining the dimensions of the opening, the feeding mechanism further comprising an actuator to move at least one of the one walls to modify one of: a separation between the first end wall and the second end wall or a separation between at least one of the end walls and the receptacle.

In an example, the carriage is to move linearly along a travel direction and the actuator may be configured to move at least one of the end walls in a direction orthogonal to the travel direction. This is, if the carriage is to move along the Y axis, the actuator may be to move at least one of the end walls along the X and/or Z axis. Also, actuator may comprise means for bi-directional movement of the end walls in directions orthogonal to the travel direction.

In a further example, the first end wall is mechanically coupled to the second end wall as to move simultaneously upon receipt of an action by the actuator.

Also, the feeding mechanism may comprise a cap to selectively close the rectangular opening. The cap may comprise electro-mechanical means for its actuation.

In order to act on the end walls and the cap, the actuator may comprise one of a servomotor, a solenoid, a pneumatic cylinder, or a manually-operated lever.