Patent Application
20190344343
This invention relates to apparatus for forming 3D objects from a stream of metallic powder.
It is known to cold spray metallic powder at rates of 500 to 1,000 ms−1 onto objects to give them a protective coating. However for all functional purposes these are only 2D surface coatings and are not used to provide 3D features. Known devices for applying the 2D coatings are not able to control the relationship between the path of the powder and the object it contacts sufficiently to enable production of 3D features. It has not occurred to those in the art to develop a 3D production technique based on sprayed metallic powder. This is possibly because in a stream of powder the particles at the centre of the stream tend to move at a greater velocity than those at the fringes, with the result that particle deposition is not uniform. While this is not a concern for a 2D coating, it makes it impractical for forming 3D objects.
To elaborate, due to the higher velocities of particles in the center of a spray cross-section, and the lower velocities at the periphery of a spray cross-section, conical structures may tend to form at an interface between the substrate and the stream of powder. As the surface angle presented by the deposited material and the stream is believed to be a critical factor to the rate of deposition, this conical arrangement may slow or otherwise hinder effective deposition. As a result, the act of holding a spray stationary over a single point in the substrate may results in a conical shape which builds briefly and then ceases as remaining powder particles simply bounce off the angled sides of the cone. The applicant has discovered that by appropriately controlling the disposition of a substrate with respect to a powder stream, a targeted 3D object can be conveniently formed.
The term “comprising” if and when used in this document in relation to a combination of features or steps should not be taken to rule out the option of there being other features or steps. The term should not be interpreted in a limiting way.
According to one aspect of the invention there is provided apparatus for forming 3D objects from metallic powder, comprising:
The substrate may or may not form part of the apparatus and, in cases where it is not, it is nonetheless mentioned for ease of definition of other components. The substrate may be a base on which the object is formed, a 3D template for a new object, or a 3D object already formed but which needs to be modified or repaired.
Optionally the delivery and positioning means may be different parts or aspects of the same component. As a further option they may be separate components.
Optionally the powder moves from the delivery means to the substrate at a speed of approximately 200 to 2000 m/s.
Optionally the powder comprises pure or alloyed metal powder, atomized to an average size of between 5 and 50 microns in diameter.
Optionally the powder comprises commercially available metal powder, such as copper or aluminium powders, eg −325 mesh and water atomized. Grade 123 pure Aluminium Powder from Alcoa Corporation is considered a suitable for at least some preferred embodiments of the invention.
Optionally the powder is supplied to the delivery means at between 0° C. and 500° C. (eg between 0° C. and 300°).
Optionally the powder is supplied to the delivery means at between room temperature (eg 25° C.) and 500° C. (eg between 0° C. and 300°).
Optionally the positioning means is able to move the substrate with respect to the delivery means. In some embodiments the positioning means may be able to move the delivery means with respect to the substrate.
Optionally the positioning means is able to maintain or adjust the vertical and horizontal spacing between the delivery means and the substrate.
Optionally the positioning means is able to maintain or adjust the angular relationship between the delivery means and the substrate in at least two axes.
Optionally the apparatus is adapted to form the 3D object by applying a sequence of layers wherein each layer is formed from the metallic powder.
Optionally the delivery means comprises a spray nozzle.
Optionally the positioning means comprises an arm having means to grip the substrate.
Optionally the control means comprises a computerised system adapted to send control signals to the delivery means and the positioning means dependent on the 3D object to be formed.
Optionally the delivery means comprises a cold spray nozzle.
Optionally the apparatus includes a housing adapted to prevent or minimise egress of powder from the apparatus.
Optionally the apparatus incorporates a 3D scanner to provide the geometry data to the control means and, based on that data, the control means causes the delivery means and the positioning means to adjust for accurate formation of the object.
Optionally the positioning means incorporates a substrate gripper which facilitates automated ejection of the object when complete.
Optionally the positioning means comprises screw or belt driven axes of motion mounted on linear guide rails, otherwise known as computer numerical controlled (CNC) axes, mounted either to the substrate or the delivery means, the other being held stationary, or where both the substrate and the metal powder supplying device are mounted to separate CNC motion controlled axes.
Some preferred embodiments of the invention will now be described by way of example and with reference to the accompanying drawings, of which:
With reference to
Referring to
The computerised system may be adapted to interpret CAD drawings and use these to determine the type and number of control signals sent to the robotic arm 2 and spray nozzle 4.
The 3D printer is preferably formed to work at high speed and so that it can print metallic objects accurately from the powder with minimal restrictions in terms of the geometry of the objects.
Preferably the robotic arm 2 causes a beam of the metal powder to moves across the surface of the substrate so that the beam remains substantially perpendicular to its point of contact of the substrate or a part formed on the substrate. This is enabled by the control functions of the printer's computerised system. The printer also enables the angle of the beam to be reoriented to less than perpendicular if need be, for example in order to form the desired 3D shape.
In some embodiments of the invention the robotic arm 2 may comprise a five axis CNC frame or a six axis industrial arm. The selection of one or the other may depend on whether speed or accuracy is the most important consideration.
In a preferred embodiment the build chamber 6 serves to physically contain excess powder to enable it to be collected and reused or recycled. The chamber 6 also keeps powder away from nearby equipment that can be damaged by exposure to the powder.
In some embodiments of the invention the amount of excess powder is sensed and control parameters adjusted to reduce it, and therefore the risk of associated hazards.
In some embodiments of the invention the printer has a 3D surface scanner within the build chamber 6. This is preferably located within reach of the robotic arm 2 and allows the printer to check the build level of an object during powder deposition breaks.
In preferred embodiments of the invention it is desirable for the substrate or spray nozzle 4, or both, to be attached to a motion control system that can continuously re-orient and maintain the angle of attack of the beam of powder generally perpendicular. In addition, a sophisticated digital control system may process a targeted 3D object geometry and generate appropriate tool paths that facilitate deposition to result in a 3D item that best matches the targeted geometry.
While some preferred embodiments have been described by way of example it should appreciated that modifications and improvements can occur without departing from the scope of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2016902183 | Jun 2016 | AU | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/AU2017/050442 | 5/15/2017 | WO | 00 |
