Field of the Invention

This invention relates to improvements in the field of additive manufacturing or 3D materials printing. In various preferred embodiments the invention provides a method and apparatus for controlling the position of a material deposition tool relative to a substrate surface and facilitates the deposition of material through tool paths which exhibit variation in three dimensions.

Background of the Invention

The development of three-dimensional materials printing technology has allowed physical articles to be produced from digital data models by the selective addition and/or consolidation of materials. Articles can be produced from materials such as polymers, metals or ceramics depending on the underlying additive manufacturing technique employed. These technologies have allowed a variety of applications to be developed, from fast prototyping through to the manufacturing of products in volume.

Polymer feedstock materials such as filaments, powders or liquids can be consolidated via a range of thermal or chemical processes to form a solid body of a desired shape. The most commonly used form of polymer 3D printing - Fused Deposition Modelling or FDM - feeds filament feedstock into an extruder that melts the material and extrudes it through a nozzle onto a previous layer, with the position of the nozzle and flow rate of material being under computer control. Similarly methods for 3D printing of metal materials have been developed which typically make use of metal powders or wires thermally melted or sintered to form a consolidated body.

With the majority of current 3D printing methods, it is common to divide the digital model data into a number of 2D parallel planar layers of equal thickness - this is typically referred to as "slicing". Each layer or slice is sequentially deposited in the consolidation process to form a three-dimensional body. This approach allows a printer deposition tool, heat or energy source to access an entire 'slice' by moving in a horizontal plane relative to a substrate surface to deposit and consolidate a single 'slice' of material in accordance with the digital model being printed.

Most 3D printing systems that use powders, filaments or fluids as feedstocks are suited to depositing nominally flat planar layers of uniform thickness. Where deviations from flat planar deposit layers are encountered in practice, these deviations are often treated as undesirable with efforts made to minimise these deviations and adhere closely to a planar, uniform thickness layer.

Different 3-D printing methods used to deposit a variety of materials can often apply layers with variable deposit geometry and characteristics. This can be due to natural variation inherent to the way the printing technique functions, or can be controllable through variation of process parameters. These variations can result in non-uniform changes in the geometry and characteristics of the deposit at different areas of a layer. Process parameters may be varied to attempt to cancel out these non- uniform variations, but in many instances corrections may not be feasible, practical or possible.

For example in the case of Arc directed energy deposition - 'Arc DED' - or Wire Arc Additive Manufacturing - 'WAAM' - material is deposited along a path by a translating electric arc heat source that forms a localised melt pool. Feedstock metal wire is added to the melt pool, depositing molten metal which solidifies behind the heat source as it translates along the path. The metal solidified along this path is not deposited with a flat surface as variation in the local environment including gravity, temperature and gas forces will impact on the shape of the deposit as it solidifies, resulting in the applied metal deposit having variation in geometry and potentially irregular surfaces. Furthermore the temperature of the substrate the metal is to be deposited upon also has an effect on the geometry of the track produced, where tall and thin deposits are likely to be applied under cooler substrate conditions.

The printing of sliced 2-D parallel planar layers also places some limitations on the geometries of the articles which can be printed using these techniques. The effect of gravity on each layer as it is deposited must be considered as a previously deposited material must be able to support the next layer as it is deposited and solidified. A certain amount of overhang beyond previously deposited material is achievable and depends on the deposition process and material properties. Alternatively a supporting scaffold may need to be included in the geometry to be printed as additional substrate surfaces when a new layer is to project over the edge of the deposit of a prior layer. In practical terms these constraints generally restrict or complicate the printing of articles with overhanging features due to the requirement of appropriately supporting the overhanging deposit material.

A further issue encountered in the printing of sliced 2-D planar layers is that the height of all features can only be an integer number of layer thickness, resulting in tolerance issues and discretisation errors in sloping surfaces and curves, known as staircase errors.

It would be of advantage to have improvements in the field of additive manufacturing or 3D materials printing which mitigated the above-referenced issues or at least provided the public with an alternative choice. In particular it would be of advantage to have improvements in this field which allowed for the deposition of 3-D printing materials with variable deposit characteristics and/or which allowed the deposition of material where the material deposits to be made were not constrained to parallel, planar slices for the fabrication of an article. It would also be of advantage to have improvements in this field which enabled the use of non-planar starting substrates.

Disclosure of the Invention

According to one aspect of the present invention there is provided a method of controlling the position of a material deposit tool relative to a substrate surface in an additive manufacturing process which produces an article using a plurality of tool paths to sequentially apply material deposits on prior material deposits, each tool path having a length divided into a number of points, the method including the steps of: i. obtaining an evolving tool path model which defines the three dimensional volume occupied by at least one prior tool path for an article to be produced and/or the location of a substrate surface, ii. obtaining at least one three dimensional boundary surface using a three dimensional model of the article to be produced, said at least one three dimensional boundary surface defining either a boundary to a starting tool path, or following and being offset from at least part of a prior tool path used to apply a prior material deposit,

Hi. defining a current tool path which records the relative position of the deposit tool and substrate surface at each point along the length of the current tool path which will deposit material adjacent to said at least one boundary surface and on a prior material deposit or the substrate surface, iv. integrating the current tool path into the evolving tool path model and repeating steps 1 to 3 for each subsequent material deposit required to produce the article and using the tool paths defined to control the position of the deposit tool relative to the substrate surface as each material deposit is applied by the deposit tool to produce the article.

According to a further aspect of the present invention is provided a method of controlling the position of a deposit tool relative to a substrate surface substantially as described above wherein the definition of the current tool path also includes determining at least one operational parameter to be used by the deposit tool at each point of said tool path, said operational parameter or parameters being determined using the three dimensional model of the article to deposit a current material deposit of a desired geometry.

According to yet another aspect of the present invention is provided a control apparatus for an additive manufacturing process which includes a processor loaded with computer executable instructions configured to obtain an evolving tool path model which defines the three dimensional volume occupied by at least one prior material deposit of the article to be produced and/or the location of a substrate surface, and obtain at least one three dimensional boundary surface using a three dimensional model of the article to be produced, said at least one boundary surface defining either a boundary to the path of a starting material deposit, or following and being offset from at least part of a prior tool path used to apply a prior material deposit, and define a current tool path having a length defined by a series of points, said current tool path recording the relative position of the deposit tool and substrate surface at each point of the length of the tool path which will deposit material adjacent to said at least one boundary surface and on the prior material deposit or the substrate surface, and integrate the current tool path into the evolving tool path model and repetitively obtain three dimensional boundary surfaces and define current tool paths for each subsequent material deposit required to produce the article and use the tool paths defined to control the position of the deposit tool relative to the substrate surface to apply each material deposit using the deposit tool to produce the article.

According to a further aspect of the present invention is provided a method of controlling the position of a material deposit tool relative to a substrate surface in an additive manufacturing process which produces an article using a plurality of tool paths to sequentially apply material deposits on prior material deposits, each tool path having a length divided into a number of points, the method including the steps of: i. obtaining an evolving tool path model which defines the three dimensional volume occupied by at least one prior tool path for an article to be produced and/or the location of a substrate surface, ii. obtaining at least one three dimensional boundary surface using a three dimensional model of the article to be produced, said at least one three dimensional boundary surface defining either a boundary to a starting tool path, or following and being offset from at least part of a prior tool path used to apply a prior material deposit,

Hi. defining a current tool path which records the relative position of the deposit tool and substrate surface at each point along the length of the current tool path which will deposit material adjacent to said at least one boundary surface and on a prior material deposit or the substrate surface, the current tool path defined specifying at each point along the length of the current tool path the orientation of the material deposit tool and or substrate surface relative to the force of gravity, iv. integrating the current tool path into the evolving tool path model and repeating steps 1 to 3 for each subsequent material deposit required to produce the article, and v. using the tool paths defined within the finalised tool path model to control the position of the deposit tool relative to the substrate surface as each material deposit is applied by the deposit tool to produce the article.

According to another aspect of the present invention is provided a method of controlling the position of a material deposit tool relative to a substrate surface in an additive manufacturing process which produces an article using a plurality of tool paths to sequentially apply material deposits on prior material deposits, each tool path having a length divided into a number of points, the method including the steps of: i. obtaining an evolving tool path model which defines the three dimensional volume occupied by at least one prior tool path for an article to be produced and/or the location of a substrate surface, ii. obtaining at least one three dimensional boundary surface using a three dimensional model of the article to be produced, said at least one three dimensional boundary surface defining either a boundary to a starting tool path, or following and being offset from at least part of a prior tool path used to apply a prior material deposit,

Hi. defining a current tool path which records the relative position of the deposit tool and substrate surface at each point along the length of the current tool path which will deposit material adjacent to said at least one boundary surface and on a prior material deposit or the substrate surface, iv. integrating the current tool path into the evolving tool path model and repeating steps 1 to 3 for each subsequent material deposit required to produce the article, and v. using the tool paths defined within the finalised tool path model to control the position of the deposit tool relative to the substrate surface as each material deposit is applied by the deposit tool to produce the article.

According to a further aspect of the present invention is provided a method of controlling the position of a material deposit tool relative to a substrate surface in an additive manufacturing process which produces an article using a plurality of tool paths to sequentially apply material deposits on prior material deposits, each tool path having a length divided into a number of points, the method including the steps of: i. obtaining an evolving tool path model which defines the three dimensional volume occupied by at least one prior tool path for an article to be produced and/or the location of a substrate surface, ii. obtaining at least one three dimensional boundary surface using a three dimensional model of the article to be produced, said at least one three dimensional boundary surface defining either a boundary to a starting tool path, or following and being offset from at least part of a prior tool path used to apply a prior material deposit,

Hi. defining a current tool path which records the relative position of the deposit tool and substrate surface at each point along the length of the current tool path which will deposit material adjacent to said at least one boundary surface and on a prior material deposit or the substrate surface, the current tool path defined specifying at each point along the length of the current tool path the orientation of the material deposit tool and or substrate surface relative to the force of gravity, iv. integrating the current tool path into the evolving tool path model and repeating steps 1 to 3 for each subsequent material deposit required to produce the article and using the tool paths defined to control the position of the deposit tool relative to the substrate surface as each material deposit is applied by the deposit tool to produce the article. According to yet another aspect of the present invention is provided a control apparatus for an additive manufacturing process which includes a processor loaded with computer executable instructions configured to obtain an evolving tool path model which defines the three dimensional volume occupied by at least one prior material deposit of the article to be produced and/or the location of a substrate surface, and obtain at least one three dimensional boundary surface using a three dimensional model of the article to be produced, said at least one boundary surface defining either a boundary to the path of a starting material deposit, or following and being offset from at least part of a prior tool path used to apply a prior material deposit, and define a current tool path having a length defined by a series of points, said current tool path recording the relative position of the deposit tool and substrate surface at each point of the length of the tool path which will deposit material adjacent to said at least one boundary surface and on the prior material deposit or the substrate surface, and integrate the current tool path into the evolving tool path model and repetitively obtain three dimensional boundary surfaces and define current tool paths for each subsequent material deposit required to produce the article, and use the tool paths defined within the finalised tool path model to control the position of the deposit tool relative to the substrate surface to apply each material deposit using the deposit tool to produce the article.

According to a further aspect of the present invention is provided a control apparatus for an additive manufacturing process which includes a processor loaded with computer executable instructions configured to obtain an evolving tool path model which defines the three dimensional volume occupied by at least one prior material deposit of the article to be produced and/or the location of a substrate surface, and obtain at least one three dimensional boundary surface using a three dimensional model of the article to be produced, said at least one boundary surface defining either a boundary to the path of a starting material deposit, or following and being offset from at least part of a prior tool path used to apply a prior material deposit, and define a current tool path which records the relative position of the deposit tool and substrate surface at each point along the length of the current tool path which will deposit material adjacent to said at least one boundary surface and on a prior material deposit or the substrate surface, the current tool path defined specifying at each point along the length of the current tool path the orientation of the material deposit tool and or substrate surface relative to the force of gravity, and integrate the current tool path into the evolving tool path model and repeating steps 1 to 3 for each subsequent material deposit required to produce the article and using the tool paths defined to control the position of the deposit tool relative to the substrate surface as each material deposit is applied by the deposit tool to produce the article.

According to an additional aspect of the present invention is provided a computer readable storage media storing computer executable instructions that when executed by a computer are configured to implement a method of method of controlling the position of a material deposit tool relative to a substrate surface in an additive manufacturing process which produces an article using a plurality of tool paths to sequentially apply material deposits on prior material deposits, each tool path having a length divided into a number of points, the computer executable instructions executing the steps of: i. obtaining an evolving tool path model which defines the three dimensional volume occupied by at least one prior tool path for an article to be produced and/or the location of a substrate surface, ii. obtaining at least one three dimensional boundary surface using a three dimensional model of the article to be produced, said at least one three dimensional boundary surface defining either a boundary to a starting tool path, or following and being offset from at least part of a prior tool path used to apply a prior material deposit,

Hi. defining a current tool path which records the relative position of the deposit tool and substrate surface at each point along the length of the current tool path which will deposit material adjacent to said at least one boundary surface and on a prior material deposit or the substrate surface, iv. integrating the current tool path into the evolving tool path model and repeating steps 1 to 3 for each subsequent material deposit required to produce the article, and v. using the tool paths defined within the finalised tool path model to control the position of the deposit tool relative to the substrate surface as each material deposit is applied by the deposit tool to produce the article.

According to another aspect of the present invention is provided a computer readable storage media storing computer executable instructions that when executed by a computer are configured to implement a method of method of controlling the position of a material deposit tool relative to a substrate surface in an additive manufacturing process which produces an article using a plurality of tool paths to sequentially apply material deposits on prior material deposits, each tool path having a length divided into a number of points, the computer executable instructions executing the steps of: i. obtaining an evolving tool path model which defines the three dimensional volume occupied by at least one prior tool path for an article to be produced and/or the location of a substrate surface, ii. obtaining at least one three dimensional boundary surface using a three dimensional model of the article to be produced, said at least one three dimensional boundary surface defining either a boundary to a starting tool path, or following and being offset from at least part of a prior tool path used to apply a prior material deposit,

Hi. defining a current tool path which records the relative position of the deposit tool and substrate surface at each point along the length of the current tool path which will deposit material adjacent to said at least one boundary surface and on a prior material deposit or the substrate surface, the current tool path defined specifying at each point along the length of the current tool path the orientation of the material deposit tool and or substrate surface relative to the force of gravity, iv. integrating the current tool path into the evolving tool path model and repeating steps 1 to 3 for each subsequent material deposit required to produce the article and using the tool paths defined to control the position of the deposit tool relative to the substrate surface as each material deposit is applied by the deposit tool to produce the article.

The present invention relates to a method, executable instructions and apparatus utilised to control the position of a deposit tool relative to a substrate surface in an additive manufacturing process. This additive manufacturing process produces an article by sequentially applying a material deposit on a previous material deposit. Reference in general throughout this specification will also be made to the invention in general being implemented by this method, while those skilled in the art will appreciate that an equivalent control apparatus is also within the scope of the invention.

Reference throughout this specification is also made to the present invention being used to control the position of a deposit tool relative to a substrate surface. Those skilled in the art will appreciate that in various embodiments the use of the term 'position' also will encompass an orientation or angle of attack of one of these components relative to the other. In a preferred embodiment the invention's control of the position of a deposit tool relative to a support surface may also extend to controlling the orientation of the deposit tool and/or substrate surface relative to the force of gravity. In such embodiments a tool path defined in accordance with the invention may specify an orientation for deposit tool and/or a substrate surface at one or more points defining the length of the tool path. The nature of newly deposited material may be that the direction of deposition relative to gravity may have an influence on the geometry and positioning of a deposit with respect to its tool path. In the instance of the Arc DED techniques the deposited material is initially liquid and as such is strongly influenced by gravity. This aspect of the invention therefore allows for additional control of the characteristics of material deposited at various points along the length of a tool path.

The invention builds on existing additive manufacturing technologies and uses as an input a three- dimensional model of an article which is to be produced. These may, for example, be solid geometry models or surface/shell models. Those skilled in the art will be familiar with such models that are widely used in additive manufacturing techniques. For example in various embodiments computer aided design (CAD) files may be used to implement a three-dimensional model of an article, and any equivalent modelling technology may also be utilised in conjunction with the present invention.

The invention may be utilised with a range of different additive manufacturing techniques which apply various types of material to produce an article. Feedstock materials such as polymers, ceramics or metals may be deposited in a range of embodiments in accordance with the present invention. In general terms additive manufacturing techniques employ some form of deposit tool to apply feedstock materials in a controlled manner. The form or construction of the deposit tool used will therefore vary considerably depending on the type and form of feedstock material being deposited. Again those skilled in the art will appreciate that the techniques and equipment used to deposit such feedstock materials are well known in the art and therefore need not be described in detail in this specification.

In a preferred embodiment the invention may be used to control an Arc directed energy deposition material deposit tool. Reference throughout this specification will also be made to preferential embodiments of the invention utilising Arc directed energy deposition (Arc DED) or Wire Arc Additive Manufacturing (WAAM) techniques which deposit metal feedstock materials. Again however those skilled in the art should appreciate that this is one example only of a number of materials and deposition methods which may be employed in accordance with the invention.

Furthermore those skilled in the art will also appreciate that a range of technologies or components may be used to modify or control the position of a deposit tool relative to a substrate surface. As the present invention facilitates the application of material deposits with geometries that vary in three dimensions a suitable movement or manipulation system can be provided to execute the relative movements of deposit tool and substrate surface required to achieve this. In additional embodiments the movement or manipulation system employed in conjunction with the present invention may be selected on the basis of the ability to control the orientation of the deposit tool and/or substrate surface relative to the force of gravity, thereby allowing gravitational forces to also influence the characteristics of material deposited in accordance with the invention.

For example, in one preferred embodiment the present invention may be implemented in combination with a 6-axis robotic arm used to move a deposit tool relative to a substrate surface which in turn may be mounted on a part positioning platform providing an additional two or more movement axes. However those skilled in the art will appreciate that a range of other types of movement or manipulation systems may also be utilised in conjunction with the present invention. Similarly the invention also utilises a substrate surface, or potentially a number of substrate surfaces in the execution of an additive manufacturing process. Those skilled in the art will be familiar with the use of a support substrates, baseplates, build platforms, or similar existing material surfaces which can receive and support a starting material deposit of feedstock material. Furthermore in some instances a substrate surface may be formed by an existing part or article - potentially with a geometry which varies in three dimensions - which is to be added to or repaired using the invention. A substrate surface may be intended to remain as part of the article being produced, or may be removed to result in a finish article. In a number of embodiments a substrate surface may also be formed from an array of adjacent material deposits applied through the prior use of the invention. Furthermore in various embodiments the invention may also facilitate the use of multiple substrate surfaces with different orientations and positions relative to one another used to support the production of articles with a range of geometries.

Reference throughout this specification will also be made to the invention utilising a single substantially flat substrate surface to receive and support a starting material deposit of feedstock material. Those skilled in the art will however appreciate that the invention may be used with more than one substrate surface or non-planar substrate surfaces in other embodiments.

Reference throughout this specification is also made to the invention being used to apply a starting material deposit, as well as a current material deposit on a prior material deposit. A starting material deposit is a special case where material is deposited directly on to the substrate surface instead of a prior material deposit. Current material deposits and prior material deposits reference how a particular material deposit should be deposited on a prior material deposit. A prior material deposit therefore may be a starting material deposit, or in most instances any material deposited before the current material deposit is to be applied.

The present invention executes a method of controlling the position of a deposit tool relative to a substrate surface by initially obtaining an evolving tool path model. This model can provide information relating to the three-dimensional volume to be occupied by at least one prior material deposit for an article to be produced, or the location of the substrate surface, or both existing material deposit and substrate surface information.

When the method of the invention initially starts the evolving tool path model may only contain information related to the location of a substrate surface. In some embodiments the evolving tool path model may also contain information relating to the surface contour or shape of a substrate surface used in the additive manufacturing process. As the method of the invention continues the evolving tool path model can integrate information relating to a sequence of tool paths to identify the three- dimensional volumes occupied by consecutive material deposits as they are applied along the lengths of these tool paths to form an article.

Therefore as the method of the invention executes the evolving tool path model will be updated by integrating tool paths. These tool paths may define the position of the deposit tool relative to the substrate surface at each point along the length of the tool path and the associated material deposit to be applied utilising the invention. The length of a tool path may preferably be discretised into a series of 'points' where the distance between points along the tall path can be dictated by the capabilities of the additive manufacturing technique used and the associated feedstock material deposited.

Tool paths are defined in accordance with the present invention using at least one three-dimensional boundary surface. A boundary surface may identify a collection of points, surface or areas which a material deposit is to contact, to not to extend past, or to extend past by some threshold distance in various embodiments. This boundary surface will therefore assist in defining the path which a new material deposit should follow when applied.

A boundary surface is obtained using the three-dimensional model of the article to be produced and acts as at least part of the guiding information required to form an article with a desired shape or geometry. When a boundary surface is to be used in the definition of a tool path of a starting material deposit the boundary surface will define - potentially with some tolerance - a boundary to the path of the starting material deposit as it is applied to the substrate surface.

Alternatively when a boundary surface is to be used in the definition of a tool path which dictates that a material deposit is to be applied on a prior material deposit, the boundary surface will follow and be offset from at least part of a prior tool path or paths used to apply the prior material deposit(s).

In the case of the invention the offset applied from the prior tool path allows for significant non-planar three-dimensional variations in the locations in which a current material deposit can be deposited. With prior art planar layer defined systems, a material deposit can only be vertically displaced by a determined layer height value from a prior material deposit and applied directly on top of a prior material deposit. Conversely the offset utilised by the present invention allows for a generation of the relative position and/or orientation of the current tool path so that the current material deposit need not be constrained to a vertical offset directly on top of a prior material deposit. In various embodiments geometric relations of the following form may be applied to the offset and positioning of a tool path, and those skilled in the art will appreciate that this offset may be defined relative to a substrate material and/or a prior tool path or previously applied material deposit:

• A combined rotation and translation relative to a previous tool path such that the form of a material deposit along the current tool path is located within a specified margin or overlap with one or a number of boundary surfaces and/or previously deposited material and/or substrate surfaces.

• Offset from a previous tool path or paths such that the current tool path is established on or near the surface of previously deposited material and the current material deposit does not exceed a boundary surface beyond a specified margin.

• Conformal to previously deposited material or substrate surface/s such that the current tool path is established on the surface of previous material deposit(s) and the current deposit material does not exceed a boundary surface beyond a specified margin.

For example, in some embodiments each current tool path may be offset from the last tool path integrated into the evolving tool path model by the definition of an offset vector translation for each point of the tool path. In further preferred forms of such embodiments an additional guiding vector may be provided which specifies for each point of the tool path the margin or overlap with at least one boundary surface and/or a previous material deposit and/or a substrate surface. In such embodiments the direction of the guiding vector may preferably point towards a prior proposed material deposit or a boundary surface.

The three-dimensional model of the article can be used to formulate boundary surfaces which define part of the exterior surface of the article. Alternatively the same model information can be used in internal volume filling processes to generate tool paths which control the position of material deposits used to fill an otherwise empty void within the interior of the article being produced. Those skilled in the art will appreciate that the invention may also utilise a combination of external surface and internal fill focused boundary surfaces in various embodiments to form an article. Reference in general throughout this specification will also be made to the invention defining a current tool path with reference to a single boundary surface only. However those skilled in the art will appreciate that multiple boundary surfaces may alternatively be used in the definition of a single tool path in other embodiments if desired.

Once any required three-dimensional boundary surfaces have been obtained the method of the invention can be utilised to define a current tool path which dictates the relative positions of the deposit tool and the substrate surface to each other for each point making up the length of the tool path. This tool path therefore dictates the three dimensional location or volume in which material should be applied for a specific material deposit on a prior material deposit or on the substrate surface while being bounded by the boundary surface.

In a preferred embodiment a tool path may also integrate or be associated with operational parameter information for at least one point of the length of the tool path and associated material deposit to be applied. In a further preferred embodiment the step of defining the current tool path includes determining at least one operational parameter to be used by the material deposit tool at each point of the tool path, the operational parameter or parameters being determined using the three dimensional model of the article to be produced.

An operational parameter or parameters can be used to control the functioning of the deposit tool and therefore the characteristics of the material deposited at specific points along the length of the tool path. These operational parameters may be used in some embodiments to modify the geometry of a material deposit to, for example, vary the height and width of the material deposited at specific points along the length of the tool path and material deposit and/or vary these characteristics relative to those of other material deposits. In additional embodiments the orientation of a deposit tool and/or a support substrate relative to the force of gravity may also be specified as such an operational parameter to be associated with at least one point along the length of the tool path. Furthermore these operational parameters may be used to control any one or combination of aesthetics and surface finishes applied to an article, the mechanical properties of the article, the time required to produce an article and/or the cost of production for an article.

For example in embodiments utilising Arc DED Manufacturing techniques any one or combination of the following operational parameters may potentially be modified for each point defined by a tool path:

• tool speed, being the speed at which the deposit tool traverses the tool path,

• material flow rate, being the mass per unit time of material fed out through the deposit tool,

• energy input, being operational parameters that define heat energy input through the deposit tool,

• Shielding gas flow rate and composition,

• Orientation of a substrate surface and/or deposit tool relative to the force of gravity - thereby allowing gravitation effects to be minimised when acting perpendicular to the current direction of travel of a deposit tool, or to have an impact on material deposit characteristics when not.

As indicated above, in various embodiments the orientation of an article being manufactured with respect to gravity may be provided as an operational parameter associated with each point of a tool path. This gravity orientation parameter may be specified to define a characteristic of a deposit along a tool path. In further preferred embodiments the relative direction of gravity may be defined in relation to a current direction of travel of a deposit tool at each point of a tool path. As gravity has a fixed direction, the relative direction of gravity with respect to the direction of travel of the deposit tool along a tool path can be controlled through the coordinated and continuous relative motion of the article being formed and the deposit tool. In particular, through the repositioning of the article and deposit tool continuously, the relation between gravity and direction of travel along a tool path can be maintained along complex three dimensional tool paths.

In a preferred embodiment of the invention an error test may be performed with respect to each tool path prior to the step of integrating the current tool path into the evolving tool path model. An error test may be used to determine if the deposition of material along any part of a tool path is possible using an identified material deposit tool and associated manipulation system. In such embodiment the invention can check if the current tool path can be completed within the constraints of the deposition technology being used. In various embodiments assessments may be made of rates of curvature of the current tool path. In additional embodiments assessments may be made of proximity of the current tool path to material deposits of prior tool paths integrated into the evolving tool path model. This error test may also check to ensure that the relative movements of the deposit tool and substrate surface can be completed in practice.

This error test may therefore detect if the tool path defined by the invention can actually be executed by the additive manufacturing technique, and may serve as an identification mechanism that triggers further processing of the tool paths and/or operational parameters in order to correct the error. In particular, this error checking system can include checking if the deposition tool and mechanism for positioning the tool (a 6 axis robotic arm in some cases) can actually perform the motion requested to deposit material along the tool path while also not intersecting or colliding with other tool paths and associated material deposits integrated into the evolving tool path model. The detection of such an error may trigger interventions such as an adjustment process configured for automatic adjustment of the tool path being processed, or an adjustment of how the deposit tool positioning system is following the tool path, and/or providing an indicator to an operator of the detection of the error.

Once a current tool path has been defined in accordance with the invention it may be integrated into the evolving tool path model and used in the production of the article required. The present invention may therefore iteratively define all the tool paths required to produce the article and integrate these paths into the required evolving tool path model.

Those skilled in the art will appreciate that in some embodiments the method of the invention may be performed as an off-line or batch process to define and integrate all the tool paths required to produce an article prior to the start of any associated additive manufacturing process.

However in other embodiments the method of the invention may be executed concurrently with the execution of an additive manufacturing process, with each tool path being defined and then used to deposit the required material deposit before the next tool path is defined. In further preferred forms of such embodiments the invention may also incorporate at least one sensor assembly which is able to provide information on the actual geometry, position or deposit characteristics of a material deposit once deposited.

Those skilled in the art will appreciate that various forms of sensing technology including electrical, acoustic, optical, spectral emission and thermal sensing technologies may be employed to provide such a sensor assembly or assemblies, and information provided by these components may be used to update the tool path information integrated into the evolving tool path model after the material deposit has been applied. Such sensing technologies may also include components of the material deposit tool itself, with readings related to its functioning and performance being able to provide information on the actual geometry, position or deposit characteristics of a material deposit once deposited. Furthermore material deposit geometry may be estimated from knowledge of the positions utilised in a tool path in combination with feedback data obtained during the deposition process.

In yet other embodiments a combination of the above techniques may be implemented in accordance with the invention. In such embodiments the invention can define a finalised evolving tool path model which integrates all tool paths required to form an article prior to any material deposits being made. Prior to the use of a tool path to apply a material deposit a validation test can be executed with respect to the previously applied material deposit using at least one sensor assembly associated with the material deposit tool and/or manipulation system. This validation test can use input supplied by the at least one sensor assembly to detect an invalid prior material deposit if the material applied in association with a prior tool path exceeds a specified margin or overlap with at least one boundary surface and/or a previous material deposit and/or a substrate surface.

In such embodiments the detection of an invalid material deposit can trigger the execution of a current tool path revision process to modify the current tool path prior to being used to apply a material deposit. For example, in various embodiments such a tool path revision process may assess the geometry of the deposit deemed to be invalid and modify the operational parameters of the current tool path to seek to correct this deficiency.

In the case where the invalid deposit lacks sufficient material to meet its expected height, width or other dimensions the current tool path may be modified to supply the required material to correct such a deficiency. For example, in such circumstances the current toolpath may be defined with modified operational parameters such as increased mass flow of filler material and/or an increased deposit tool energy input to re-melt the invalid (undersize) deposit to a greater depth, and infill a greater amount of material into or onto the invalid deposit to compensate for the previously detected undersize deposit condition.

In another example the deposition of a tool path deposition process may have been interrupted and only part of the intended tool path is processed, subsequently triggering the identification of an invalid material deposit. In such circumstances a current tool path revision process may operate to define a tool path to build up the part from the previously deposited material. As the deposit error was identified, the process has knowledge of where material was and was not deposited along on the previous tool path, the revised tool path would be formed to apply material where it was needed to continue building up the article to be formed.

The present invention may provide many possible advantages over the prior art or at least provide an alternative choice to the prior art.

The present invention makes use of a three-dimensional model of an article to compile an evolving tool path model. This evolving tool path model provides information on a substrate surface or surface to be used to support an article as it is produced, as well as a sequence of tool paths which describe the required positioning and motion of a deposit tool relative to the substrate surface(s) which will produce the article. Each tool path describes how and where a current material deposit is to be applied to prior material deposits, or substrate surfaces.

These tool paths can be substantially non-planar with variation along their length in three dimensions, thereby conforming to variation and complexity in the geometry of articles which can be produced in accordance with the present invention. In various preferred embodiments the material deposited may also exhibit variable geometries between different deposits and/or variable cross-sectional profiles along the length of a single deposit. This may be achieved through the incidental and intentional changing of processing conditions. These variations can be used to adjust or control the geometry of various deposits as well as characteristics such as surface finish and appearance, the mechanical properties of the article, as well as the time required to produce the article or the cost of production of the article. These steps may be taken to, for example, increase deposition rate or develop tool paths that can conform closer to the geometry and more accurately build the desired article.

In various embodiments the invention allows the force of gravity to be utilised as an operational parameter which can dictate characteristics of the article being manufactured. The invention may control the behaviour of a deposit tool and part manipulation system in such embodiments to minimize the effects of gravity on material as it is deposited, or alternatively use gravity to shape a flow of molten material before solidification.

In a preferred embodiment the part manipulation system being able to continuously reposition the substrate surface through at least two axes by means of rotating and tilting during translation of the deposit tool along a tool path as it deposits material. The relationship between the direction of travel of a deposit tool at each point along a tool path and a gravity vector can be specified and used by the invention to deposit material at a particular inclination in order to achieve a desired deposit characteristic or characteristics. For example, in various embodiments Characteristics of surface finish through intentional material runoff, height, and width of deposit may be modified by the invention depending on this inclination with respect to gravity.

In further embodiments the invention can allow for the definition of a finalised evolving tool path model which integrates all tool paths required to form an article prior to any material deposits being made. This approach allows all the tool paths required to be defined virtually before manufacturing starts with preferably these tool paths being error checked to confirm they can be executed using an identified material deposit tool and associated manipulation system. In additional embodiments which allow the force of gravity to be utilised as an operational parameter the effect on the resulting material deposit may also be modelled virtually prior to any manufacturing process being started.

Brief description of the drawings

Additional and further aspects of the present invention will be apparent to the reader from the following description of embodiments, given in by way of example only, with reference to the accompanying drawings in which:

• Figure 1 provides a flowchart of steps executed in accordance with a method of controlling the position of a deposit tool relative to a substrate surface as provided in various embodiments,

• Figure 2 provides a schematic cross-section visualisation of a tool path as provided in a further embodiment,

• Figure 3 provides a schematic cross-section visualisation of four adjacent tool paths used to apply four consecutive material deposits in various embodiments,

• Figure 4 provides a further schematic cross-section visualisation of three adjacent tool paths used to apply three consecutive material deposits adjacent to one another on an existing substrate surface in a further embodiment,

• Figure 5 provides a schematic visualisation of tool paths and associated material deposit generated relative to other material deposits in accordance with various embodiments, and • Figure 6 provides a schematic visualisation of adjacent tool paths used to apply consecutive material deposits in various embodiments,

• Figure 7a and 7b provide schematic side and perspective visualisations of a portion of an evolving tool path model,

• Figure 8 provides a further schematic visualisation of an evolving tool path model defining a portion of an article being produced by the processes of this invention, and

• Figures 9a, 9b show schematic visualisations of the use the invention in a further embodiment during the deposition of material when orientation relative to gravity is varied as an operational parameter.

Further aspects of the invention will become apparent from the following description of the invention which is given by way of example only of particular embodiments.

Best modes for carrying out the invention

Figure 1 provides a flowchart of steps executed in accordance with a method of controlling the position of a deposit tool relative to a substrate surface as provided in various embodiments.

At step A of this method a computer aided design (CAD) file is received to serve as the three- dimensional model of the article to be produced using an additive manufacturing technique. Concurrent with the receipt of the CAD file an evolving tool path model is instantiated and holds information related to the location and the geometry of a substrate surface to be used in this additive manufacturing technique. Deposition process information is also received in this step which identifies how characteristics of the material being deposited are related to process parameters.

At step B a test is executed to determine if the evolving tool path model contains sufficient tool paths and associated deposit geometry to completely produce the article represented by the received CAD file. If the evolving tool path model does contain sufficient tool paths step E is executed, and if not step C is executed as discussed further below.

At step C the identity or absence of a prior tool path from the evolving tool path model is identified and a three-dimensional boundary surface is obtained from the CAD file for the current tool path which is to be formulated next. These boundary surfaces may correspond to an exterior surface to be defined for the article to be manufactured, or may dictate the location at which material is to be deposited in an operation which fills a void or space within the interior of the article. In the case of a starting material deposit the information contained in the CAD file will define the track to be taken along the substrate surface.

Step C then defines a current tool path with use of the boundary surface. This current tool path determines the relative position of the deposit tool and substrate surface at each point along the length of the tool path which would deposit material adjacent and within a specified margin, to the boundary surface and on the substrate surface or previous material deposits. Operational parameters associated with the use of the deposit tool can also be indexed to the tool path in association with each respective point or segment along the tool path length.

The current tool path can be defined to ensure that the material deposit to be deposited is applied to prior material deposit/s while also ensuring the current material deposit maintains a desired relationship with boundary surfaces. In various embodiments this may include specific offsets and orientation about a prior tool path or exterior surface of a prior material deposit. The tool path can be defined with use of a translation operation which ensures that the material deposit to be deposited is still applied to the last or prior material deposit while also ensuring the current material deposit does not breach the boundary surface or surfaces. In various embodiments this translation may include specific vertical or horizontal offsets from a centre point or exterior surface of the last material deposit, rotations of the deposit tool about a centre point or exterior surface of the last material deposit, discontinuities in the current material deposit where material is not applied to the last material deposit, or extensions where the current material deposit is also applied to surfaces other than the exterior of the last material deposit.

At step C the evolving tool path model can be tested in combination with a newly defined tool path to identify one or more error conditions. These tests can be completed to detect if the current tool path intersects with itself or any prior tool path, and if the current tool path may cause the deposit tool or other part of the manipulator system to come into contact with prior deposited material or other structures.

If one or more error conditions are detected, the process may be paused and a warning signal or notification can be provided to an operator allowing the current tool path to be manually corrected or for manual revision of the source CAD file may be made. Alternatively an automated revision to the tool path may be made where practicable. If no error conditions are detected in the new current tool path step D is executed.

In step D the current tool path is integrated into the evolving tool path model. The evolving tool path model stores information on the relative positions of the deposit tool and substrate surface/s of the additive manufacturing equipment for the current tool path and prior tool path/s. It also contains information about the process control parameters to be used to generate a material deposit along these tool paths, and the resultant geometry and surface information for simulated or measured material deposits along prior tool paths.

In one embodiment where the physical part is being deposited as each tool path is generated, the tool path and associated control parameters are used to control the relative positions of a deposit tool and manipulator system to deposit material along the current toolpath with the desired characteristics. The evolving toolpath model is updated with the geometry of the deposit associated with the current toolpath. This current deposit geometry may be modelled from knowledge of the outcome of deposition parameters employed, or measured following deposition in a case where the deposition system has the capability to record or measure the physical characteristics of a material deposit once applied.

A further embodiment is the case where the physical part is not being deposited as each tool path is generated. In this case the evolving toolpath model is updated with the simulated/modelled geometry of the material deposit associated with the current toolpath.

Following step D, the method being executed returns to step B. As indicated above this method continues to execute and generate tool paths for deposition or simulation of material deposits in sequence until either an error condition is detected at step C or the evolving tool path model contains sufficient tool paths to allow step E to be executed.

Where physical deposits were made in step D, in step E the process concludes with the desired geometry completed. Where no physical deposits were made in step D, in step E the deposit tool is controlled along the series of toolpaths in the evolving tool path model, depositing material and building up an article to the desired geometry using the processing parameters associated with each tool path.

In some possible embodiments step E incorporates the execution of a validation test on the previously applied material deposit before the current tool path is drawn from the finalised evolving tool path model. This validation test uses the output of a sensor assembly which can measure the dimensions and geometry of the material actually applied. Process parameter feedback data collected during previous depositions can also be interpreted to provide geometric and other characteristic information on these prior deposits. The material deposit made in accordance with prior tool paths may be determined to be invalid where it exceeds a specified margin or overlap with at least one boundary surface, a previous material deposit, a substrate surface, and/or a planned interim surface intended to receive subsequent deposits.

In these embodiments the detection of an invalid material deposit triggers the execution of a current tool path revision process to modify the current tool path prior to it being used to apply a material deposit. This toolpath modification may include tool-path positional adjustments to revise planned deposit locations into desired positions relative to previous deposits, and/or other process parameter adjustments intended to revise planned deposit geometry in response to the information utilised in relation to the validation test.

Figure 2 provides a schematic cross-section visualisation of a tool path as provided in a further embodiment.

As can be seen from figure 2 a cross section of a material deposit along a tool path 21 can be visualised and defined relative to an underlying material surface 23 and a three-dimensional boundary surface 24. The underlying material surface 23 may be provided by a substrate surface on which material is applied to build up the article being produced, or may be defined by the exterior surface of a previously applied material deposit.

Each point or unit length of the deposit tool path 21 may also integrate references to or be associated with operational parameters which define the characteristics and geometry of the material applied. In the embodiment shown these variable characteristics are represented by the H and W variables which generally characterise the volume occupied by the material at this particular point or segment of the path.

Figure 3 provides a visualisation of four adjacent tool paths 31 used to apply four consecutive material deposits 32 to form a portion of an article in further embodiments. This figure illustrates how a number of tool parts can be generated in the sequence to form a desired article.

Similar to the tool path illustrated with respect to figure 2 each of the paths 31 shown are also associated with a three-dimensional boundary surface 34 , which in this embodiment is defined by the exterior surface 34 of the article to be produced.

The boundary surface 34 assists in the definition of the tool paths 31 along which material is to be deposited to achieve the exterior surface for the article to be produced. In the embodiment shown the tool paths 31 are positioned relative to the boundary surface 34 using a guiding vector 36 which is representative of the cross section of the material to be deposited along the tool paths 31 in order to achieve the specified tolerance of material deposition 37 relative to the boundary surface 34. In this embodiment this is an overlap with the nominal surface of the article to be produced which defines the external deposited surface 34.

In this embodiment each successive tool path 31 is offset from the prior tool path by an offset vector translation 35 which ensures that the subsequent tool path 31 is generated on or near to the surface of a prior deposit or substrate surface 33. Deposition of material along each successive tool path 31 will be such that it is upon the surface of the material deposit of a prior tool path or paths to enable the build-up of the item to be produced.

Figure 4 provides a further visualisation of three adjacent tool paths 41 used to apply three consecutive material deposits 42 adjacent to one another but upon an existing substrate surface 43. As with the tool paths illustrated with respect to figure 3 each adjacent tool path 41 is separated from its neighbour through the use of an offset vector translation 45.

In the instance of figure 4, a guiding vector 46 is provided parallel to the offset vector 45 and is representative of the cross section of the material to be deposited 42 along each tool path 41. The offset vector 45 translation of the subsequent tool path 41 is such that the tool path is generated on the substrate surface 43 and the guiding vector 46 is relative to the surface of a previous material deposit along a previous tool path 41 within a specified tolerance 47. The tolerance 47 is such that an overlap between materials deposited along sequential tool paths 41 is achieved.

Figure 5 provides a schematic visualisation of tool paths and associated material deposit generated relative to other material deposits in accordance with various embodiments. This figure illustrates the invention's ability to generate sequential tool paths on which material deposits are made in a variety of orientations and locations. This sequence of material deposits begins with a starting tool path 51 used to apply a starting material deposit to a substrate surface.

A second material deposit 52 can be made either on top of the prior starting material deposit, or adjacent to and laterally offset from the side of this starting material deposit.

Subsequent material deposits 53 can be applied on top of the prior material deposit, or again adjacent to and laterally offset from the side of a previously applied material deposit.

A further material deposit 54 can be applied on top of any one of the previously applied material deposit and aligned along the length of this prior material deposit. Alternatively this further material deposit may form a new starting material deposit with uses a number of previously applied material deposits as a substrate surface.

Figure 6 provides a schematic visualisation of adjacent tool paths used to apply consecutive material deposits in various embodiments. This figure illustrates the invention's ability to generate tool paths that define material deposits which vary the characteristics of the material deposited along the length of the tool path. In various embodiments this facility may be provided by associating a tool path with additional information relating to operational parameters used to control the functioning of the deposit tool used.

As is illustrated by figure 6 a starting tool path 61a and associated material deposit 61b can be applied using operational parameters which change the cross-sectional area of the deposit along the length of the tool path. In the presented case this is a reduction in cross-section from left to right along the length of the tool path. After this starting material deposit is applied a subsequent tool path 62a can be defined relative to the first tool path in accordance with the embodied procedure in figure 3 and figure 4 where the tool path is offset from the previous tool path to remain near the surface of the material deposit defined by the previous tool path 61a.

After this starting material deposit is applied a subsequent tool path 62b can be defined to apply a further material deposit 62b, 62c or 62d on top of the starting material deposit 61b.

The operational parameters associated with the subsequent tool path 62a may be varied to apply a further material deposit where:

62b exhibits a uniform cross-section along the length of the deposit,

62c exhibits a changing cross-section along the length of the deposit, increasing in cross-section from left to right to compensate for the change in shape of the starting deposit 61b relative to the starting substrate, or

62d exhibits a changing cross-section along the length of the deposit, decreasing in cross-section from left to right to replicate the form of the starting material deposit 61b of the starting tool path 61a.

Figure 7a and 7b provide further schematic side and perspective visualisations of a portion of an evolving tool path model. These figures highlight how sequential tool paths can develop and become non-planar when generated relative to previous tool paths and deposited material as the part geometry changes shape with respect to the previous tool paths.

Figure 7b highlights how each tool path generated has an associated material deposit geometry defined along their length.

The sequence of material deposits can be applied along these tool paths to build up the portion of the article shown. As can be seen from figure 7a and 7b the tool paths also need not be closed paths that are generated for the full length of a prior tool path. These partial tool paths would exceed a tolerance to the boundary surface that defines the surface of the article to be produced. The boundary surfaces associated with the article determine that these tool paths be open paths that need not follow the entire length or surface of a prior material deposit.

Figure 8 provides a schematic visualisation of an evolving tool path model defining a portion of an article being produced by the processes of this invention.

A subsequent tool path 81a is presented relative to material deposits defined along prior tool paths 81b. The subsequent tool path 81a is defined on previous tool paths 81b. This figure illustrates how complex tool path forms can evolve when following the part geometry from a starting material deposit applied to a flat substrate.

As can be seen from this figure the tool paths executed in accordance with the invention become complex and curved with variation in three-dimensions, while still able to be used in the production of articles by additive manufacturing techniques. In particular the tool paths highlighted with respect to figure 8 illustrate significant variation in three dimensions along their length as each material deposit is laid down to produce the form shown with a complex curved geometry.

Figures 9a, 9b show schematic visualisations of the use the invention in a further embodiment during the deposition of material when orientation relative to gravity is varied as an operational parameter. In the embodiment shown the characteristics of a material deposit 92 along a tool path may be altered by the relative direction of gravity. This tool path defines a direction of travel 91b for a deposition tool 98 at each point on the tool path which will deposit material in a region 91a on a substrate 93 in front of the tool 98.

Figure 9a illustrates operation of the invention in this embodiment where the force of gravity 99 acts nominally down and perpendicular to the direction of travel 91a of the deposit tool 98, and the deposited material 92 has a first cross section 92a defined by this orientation and other operational parameters.

Figure 9b illustrates operation of the invention in the same embodiment when a larger deposit cross section 92a is required. In these circumstances the direction of travel 91b along a tool path is inclined up with respect to the force of gravity 99. This will cause an applied molten material 92 to partially slump down the incline as the material is deposited. This will generate a larger deposit cross section 92a.

In such embodiments the required deposit geometry and characteristics are defined using operational parameters to achieve suitable build-up of material to build the article to be formed. To achieve this, the orientation of the article being formed with respect to gravity at each point along a tool path is defined as one of the operating parameters available for the process to vary to achieve the required deposit. This allows a required motion of the article to be defined as a rotation and/or tilt that positions the article such that gravity acts in the defined direction for each point of a tool path.

In the preceding description and the following claims the word "comprise" or equivalent variations thereof is used in an inclusive sense to specify the presence of the stated feature or features. This term does not preclude the presence or addition of further features in various embodiments.

It is to be understood that the present invention is not limited to the embodiments described herein and further and additional embodiments within the spirit and scope of the invention will be apparent to the skilled reader from the examples illustrated with reference to the drawings. In particular, the invention may reside in any combination of features described herein, or may reside in alternative embodiments or combinations of these features with known equivalents to given features.

Modifications and variations of the example embodiments of the invention discussed above will be apparent to those skilled in the art and may be made without departure of the scope of the invention as defined in the appended claims.