Technical Field of the Invention

The present invention relates to methods and apparatus for 3D printing, and products obtained therefrom. The invention further relates to methods and apparatus for 3D printing food products, in particular 3D-printed confectionery products, and products obtained therefrom.

Background to the Invention

3-dimensional (3D) printing is a process of making a 3D solid object, in which successive layers of printing material are laid down based on a pattern from a digital template. In most 3D printing applications, the layers of material are laid down through selective laser sintering, fused deposition or stereo-lithography.

A 3D printer typically includes an extrusion head or print head which has a nozzle. A feed of raw material is fed into an upper region of the extrusion head as a solid. After being melted or rendered flowable within the extrusion head, a filament exits the extruder in its molten or flowable form as a continuous stream of molten or flowable material. The molten material is then deposited layer by layer to build up the intended product. In many 3D printing applications hundreds or even thousands of layers of build material may be layered one on top of each other before the final solid object is finished.

In the majority of 3D printing apparatus and applications, the raw build material is presented in a cartridge or container and may be in filament form, or powder/granular form. Most modelling materials for use in known 3D printers are typically amorphous thermoplastic materials such as thermoplastic polymers.

It is also known to provide 3D printing of food such as confectionery. For example, US2012/0251688 provides a 3D printer for the 3D printing of chocolate in which the apparatus includes a reservoir configured to shear and heat a chocolate material to provide flowable chocolate, a pump configured to pump the flowable chocolate material from the reservoir and a print head configured to receive the pumped flowable chocolate material and extrude a portion thereof to form a 3 -dimensional solid object.

Likewise, US2017/0259482 describes an apparatus and process for the 3D printing of chocolate comprising a printer cartridge having a cartridge barrel for containing a chocolate print material, an extruder having a nozzle and a pneumatic system for enabling pressurised air to push the print material from the printer cartridge to the extruder.

Known 3D chocolate and confectionery extruders therefore generally utilise cartridges or containers of molten and/or tempered chocolate which are pushed, via pressure through an extrusion die head as the printer head. In such apparatus, it can be very difficult to control pressures within the system or apparatus, and the use of cartridges or reservoirs means that batch processing is generally undertaken, rather than continuous processing,

It would therefore be advantageous to provide a 3D printing apparatus and method, suitable for the 3D printing of chocolate and other confectionery, in which a continuous process is possible, which continuous process may be modified in situ, and in which changes in material flow, volume and consistency can be accommodated without stopping or negatively affecting the 3D printing process.

It would also be advantageous to provide a 3D printing apparatus, particularly for confectionary and chocolate, in which extrusion of the chocolate may be performed with a solid start material (such as chocolate flakes or powder), and which can be performed continuously, irrespective of changes to the volume, flow rate or consistency of the chocolate material.

It is therefore an aim of embodiments of the present invention to overcome or mitigate at least one problem of the prior art.

Summary of the Invention

According to a first aspect of the invention there is provided a 3D printing apparatus comprising at least one print head, a supply system for continuously supplying at least one print material to the or each print head in a flowable state, and at least one pressure regulation device for regulating the back pressure of the or each flowable print material to the or each print head.

The or each print material may comprise any material which is in a flowable state at ambient temperature (e.g. room temperature), or which can be heated into a flowable state.

The or each print material may comprise a polymeric material, an elastomeric material, a plastic material, a plastics material or a food material. In preferred embodiments the print material is a food material, more preferably a confectionery material. In especially preferred embodiments, the confectionery material is chocolate, such as milk chocolate, dark chocolate, white chocolate or compound chocolate.

The supply system may comprise at least one supply path. In some embodiments, the supply system comprises at least 2, 3, 4, 5, 6, 7, 8, 9 or at least 10 supply paths. In preferred embodiments, the supply system comprises 1 supply path.

The or each print head may comprise a screw-containing pump (or rotor- containing pump), such as an auger pump or a progressive cavity pump. The or each print head may comprise a nozzle at its distal end. In some embodiments, the or each print head comprises a screw-containing pump and a nozzle located at the distal end of the pump. The presence of the nozzle helps to direct the flow of print material as it exits the pump.

In embodiments wherein the or each print head comprises a screw-containing pump, print material which is being continuously supplied to the or each pump (in a flowable state) can be extruded out of the or each pump (or out of a nozzle connected thereto) at any desired rate, simply by changing the rotation speed of one or more screws and/or nozzles. Therefore, the rate of extrusion out of each pump may be individually controlled by varying the speed of each auger pump individually.

The or each supply path may comprise a single print head, or may comprise at least 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45 or at least 50 print heads and/or no more than 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45 or no more than 50 print heads. The at least one print head of a supply path may be arranged into at least one print module. In some embodiments, the or each supply path comprises at least 1, 2, 3, 4, 5, 6, 7, 8, 9 or at least 10 print modules. The or each print module may comprise at least 1 , 2, 3, 4, 5, 6, 7, 8, 9 or at least 10 print heads. In some embodiments, the or each print module comprises between 3 to 7 print heads, such as 5 print heads.

The or each supply path may comprise a conduit network connected to, and arranged to supply print material to (i.e. positioned upstream of), the or each print module.

The or each conduit network may comprise a central conduit. In some embodiments, the central conduit may comprise a print module located at its distal end. In some embodiments, the central conduit may comprise a single linear conduit with a print module located at the distal end thereof. In other embodiments, the central conduit may comprise a branched structure such that the respective supply path comprises a branched conduit network comprising a branched central conduit arranged to supply the or each print module with print material. In some embodiments, the branched central conduit may comprise one or more print modules connected to each branch. The central conduit may branch at one or more branch points, wherein a branch point is a point along the central conduit where one flow path of the print material splits into two or more flow paths (in the downstream direction - e.g. towards the or each print head).

The or each print head of a print module may be directly connected to, and supplied by, a terminal conduit. A terminal conduit is defined herein as a section of the central conduit or a branch thereof which comprises no branches (or further branches) in the downstream direction and comprises a print head at its distal end. A terminal conduit therefore follows a single flow path (in the downstream direction towards the print head) and does not branch.

The or each print module may comprise at least 1, 2, 3, 4, 5, 6, 7, 8, 9 or at least 10 terminal conduits which branch from the same branch point or different branch points of the central conduit.

Many embodiments of the conduit system may be envisaged by the skilled person and are covered by the invention. For example, travelling in a downstream direction from the source of the central conduit, there may be at least 1, 2, 3, 4, 5, 6, 7, 8, 9 or at least 10 branch points in the central conduit prior to reaching at least one print head.

The or each supply path may comprise a print material delivery device. The or each print material delivery device may be directly connected to, and arranged to supply print material to (i.e. upstream of), the conduit network of its respective supply path.

The or each print material delivery device may comprise at least one screw- containing extruder, such as a screw extruder (for example a single screw extruder or a twin screw extruder). In some embodiments, the or each screw-containing extruder may comprise a screw feeder coupled to a pump, such as a positive displacement (PD) pump. In some embodiments, the or each supply path may comprise at least 2 or at least 3 screw-containing extruders. At least 2 or at least 3 screw extruders may be arranged in succession. In such embodiments, the end of a preceding screw extruder may be arranged to overlap with the subsequent screw extruder in the longitudinal direction. In preferred embodiments, the or each supply path comprises two screw extruders arranged in succession, wherein the first screw extruder is located adjacent (preferably above) the second screw extruder, and a portion of the first screw extruder overlaps with the second screw extruder in the longitudinal direction.

The or each supply path may comprise at least one print material infeed for receiving the or each print material to eventually be supplied to the or each print head. The or each print material infeed may be directly connected to, and arranged to supply print material to (i.e. upstream of), the print material delivery device of the respective supply path(s). The print material infeed may comprise at least one volumetric feeder and/or at least one gravimetric feeder, such as a hopper, arranged to receive the print material.

The or each supply path and/or each conduit in the supply path may comprise a separate print material infeed (i.e. one infeed per supply path) or at least two supply paths may share a common print material infeed. In preferred embodiments, all supply paths share a common print material infeed. In some embodiments, the or each supply path may comprise at least 2, 3, 4 or at least 5 print material infeeds. The or each supply path may comprise its own, or a shared, pressure regulation device configured in use to regulate the back pressure of the or each flowable print material to the or each print head.

The or each pressure regulation device may comprise at least one pressureregulating chamber, such as a pressure-regulating cylinder.

The or each pressure-regulating chamber may comprise a piston arranged to move along the pressure-regulating chamber in order to regulate the back pressure of the or each flowable print material to the or each print head. The or each piston may be operated pneumatically, hydraulically and/or electrically, for example.

In other embodiments, the or each pressure-regulating chamber may comprise an adjustable volume chamber, such as an adjustable volume cylinder. In such embodiments, the volume of the chamber may be controlled in order to regulate the back pressure of the or each flowable print material to the or each print head.

The or each pressure-regulating chamber and/or a piston located therein may comprise a force and/or pressure sensor for monitoring the force and/or pressure being exerted on it by the or each print material.

In some embodiments, the or each supply path may comprise a single pressure regulating chamber, or may comprise at least 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45 or at least 50 pressure-regulating chambers and/or no more than 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45 or no more than 50 pressure-regulating chambers.

An apparatus comprising fewer pressure-regulating chambers may be advantageous due to the associated reduced cost and/or complexity of manufacturing, operating and/or maintaining such a system. However, an apparatus comprising more pressure-regulating chambers may be advantageous as it may allow for more control over more localised variations in pressure throughout the system, by locating multiple chambers at various locations, than would be possible with an apparatus with less (such as one) pressure-regulating chambers.

The or each pressure regulation device may be positioned at any suitable position along the or each supply path. In some embodiments, the or each supply path may comprise at least one pressure regulation device positioned downstream of the or each print material delivery system (such as extruder) and/or upstream of the first branch point of the central conduit. In some embodiments, at least one pressure regulation device may be positioned along the central conduit of the conduit network, which may be upstream of the first print module and/or branch point, downstream of the last print module and/or branch point, an/or between two print modules and/or branch points.

In embodiments comprising a branched central conduit, at least one pressure regulation device may be positioned at any suitable position along the or each branch. In some embodiments, the or each supply path may comprise at least one pressure regulation device positioned along the central conduit at a location downstream of at least one branch point of the central conduit and/or between two branch points of the central conduit.

In some embodiments, at least one pressure-regulating chamber may be positioned on at least one terminal conduit. In some embodiments, at least one (preferably only one) pressure regulation device, such as at least one pressureregulating chamber, may be positioned on each terminal conduit.

Having a pressure regulation device/pressure-regulating chamber positioned on each terminal conduit allows for excellent control of back-pressure to the or each print head, as each device/chamber is able to compensate for variations in back-pressure at a very localised level, i.e. down to the level of a single print head. This provides excellent accuracy of back-pressure being applied to each print head. At least one pressure regulation device may be positioned upstream of at least 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45 or at least 50 heads and/or no more than 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45 or no more than 50 print heads. In some embodiments, at least one pressure regulation device may be positioned upstream of each print head.

As described above, at least one pressure regulation device may be positioned at any suitable position on the apparatus, but preferably along the central conduit (or branches therefrom) of the conduit network. Exact positioning of a pressure regulation device thus determines the number of print heads located downstream of it. Therefore, the relative positioning of pressure regulation devices can be varied in order to optimise pressure regulation to the or each print head, especially where there may be more localised variations in back pressure within various parts or sections of the apparatus or conduit network.

In some embodiments, the central conduit (which includes any branches therefrom) may vary in size and/or shape along its length. In such embodiments, the central conduit may comprise substantially constant dimensions (for example diameter or cross-sectional area), or within a defined range, along at least one portion or the whole of its length and the or each pressure regulation device positioned along such a central conduit (or portion(s) thereof) may comprise a bulge in the central conduit (or portion(s) thereof).

In other embodiments, the central conduit may comprise at least one reservoir, which may comprise a section of the central conduit comprising much larger dimensions than the central conduit and pressure-regulating chambers as described above. The or each reservoir may be configured to hold a large volume of the or each print material. The or each reservoir may be configured to hold enough print material to last for at least 5 minutes, 10 minutes, 15 minutes, 20 minutes, 30 minutes, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 15 hours, 20, hours or at least 25 hours of continuous 3D printing. Such embodiments may be advantageous as they remove the need for continuous feed (i.e. constant flow) of the or each print material into the conduit network until the or each reservoir depletes, and so the print material delivery device (e.g. screw extruder) does not need to be constantly running. When the or each reservoir depletes of the or each print material, the print material delivery device can be actuated in order to refill them again, and can subsequently be switched off again. In such embodiments, the print material delivery device may simply comprise a hopper.

The conduit network may comprise at least 2, 3, 4, 5, 6, 7, 8, 9 or at least 10 reservoirs.

The or each reservoir may comprise a branch point of the central conduit. That is, one or more branches of the central conduit may extend downstream from the or each reservoir. In some embodiments, the conduit network comprises a single reservoir from which all branches (if any) of the central conduit extend downstream. In such embodiments, every print module is arranged downstream of, and supplied with the or each print material by, the single reservoir.

In other embodiments, the central conduit comprises a series of connected reservoirs, which may each have branches extending downstream therefrom. The or each reservoir of the series of connected reservoirs may be connected by a section of central conduit with reduced dimensions relative to the reservoirs.

The or each reservoir may be a pressure regulation device, and so may comprise a pressure-regulating reservoir.

The or each pressure-regulating reservoir may comprise a piston located therein.

In other embodiments, the or each pressure-regulating reservoir may comprise an adjustable volume reservoir.

The or each pressure-regulating reservoir may comprise any of the features as described above in relation to the pressure-regulating chambers. For example, the or each pressure-regulating reservoir may comprise a piston located therein, or may comprise an adjustable volume reservoir, and/or may comprise at least one force and/or pressure sensor.

The or each reservoir may have any suitable dimensions, for example for a reservoir of a given volume, it may be shorter and wider or longer and thinner. Longer, thinner reservoirs may be advantageous as they allow for easier fine control of backpressure and/or volume, as a given piston movement distance will alter the volume much less than an equivalent piston movement distance in a wider reservoir. In some, embodiments, the or each reservoir may have such dimensions as to have substantially the same dimensions as the central conduit and/or the central conduit itself may comprise a piston and/or an adjustable volume portion, such that it may itself function as a pressure-regulating reservoir.

The or each pressure-regulating chamber and/or reservoir may comprise at least one volume-monitoring device to monitor the volume of the or each chamber and/or reservoir and/or of the or each print material contained therein. The or each volume- monitoring device may comprise at least one sensor arranged to detect the position of a piston located within the respective chamber or reservoir and/or at least one sensor arranged to detect the position or configuration of any adjustable portion of an adjustable volume chamber or reservoir.

In some embodiments, at least one pressure regulation device may comprise a screw extruder, such as at least one single screw extruder and/or at least one twin screw extruder. The pressure-regulating screw extruder(s) may comprise part of the or each print material delivery-system. The or each screw extruder of the or each print material delivery system may therefore function as a pressure regulation device. The pressureregulating application of screw extruders is described hereinbelow in more detail in relation to the third aspect of the invention.

In some embodiments, the or each pressure regulation device may only comprise a screw extruder(s), i.e. there are no pressure-regulating chambers or pressure-regulating reservoirs. Such embodiments avoid the complexity and cost involved with manufacturing, operating and/or maintaining apparatus comprising pressure-regulating chambers and/or pressure-regulating reservoirs.

The apparatus may alternatively or additionally comprise at least one pressure and/or force sensor arranged at any suitable position within the apparatus, which is not arranged to sense the pressure and/or force inside and/or being exerted on any part of, a pressure regulation device, the position of any piston(s) located therein, or the configuration and/or position of any adjustable volume portion thereof. Nonetheless, in such embodiments, the or each force and/or pressure sensor may be operably connected to at least one pressure regulation device, any piston(s) located therein, and/or any adjustable volume portions thereof such that it/they can be operated based on information supplied by such a pressure and/or force sensor(s).

The apparatus may comprise a temperature control system configured to control the temperature of the or each print material within the apparatus by supplying heat to it or cooling it. The temperature control system may comprise at least one temperature control sleeve or jacket arranged in contact with at least part of the outer surface of the apparatus. The or each temperature control sleeve or jacket may comprise a fluid jacket, such as a liquid jacket, through which a fluid may be circulated. In preferred embodiments, the or each fluid jacket may comprise a water jacket. The or each temperature control sleeve or jacket may comprise an electrical heating sleeve.

In preferred embodiments, the or each sleeve or jacket comprises a water jacket, as water jackets can easily be configured to switch between heating and cooling functions by simply altering the temperature of the water flowing through.

At least one sleeve or jacket may be arranged around the outer surface of a portion or substantially the entirety of the or each supply path, print material infeed, print material delivery device, conduit network, central conduit (including branches of the central conduit), pressure-regulating chamber, reservoir, pressure-regulating reservoir and/or the or each print module. In preferred embodiments, substantially all surfaces which come into contact with print material inside the apparatus are temperature controlled by the temperature control system.

The temperature control system allows the temperature of the print material to be controlled as it travels through the apparatus, which is important to ensure that the print material stays within a desired temperature range, so that, for example, it doesn’t at least partially or completely solidify, or decompose under extreme heat, in the supply system and/or in the or each print head.

The print material may have to be cooled, for example where the apparatus comprises one or more screw extruders and grinding and/or mixing of the or each print material in the or each screw extruder is generating a lot of heat.

It is to be appreciated that the dimensions of the apparatus, such as the conduit network and any pressure-regulating chambers or reservoirs, may be varied in order to optimise temperature regulation of the or each print material contained therein.

According to a second aspect of the invention there is provided a 3D printing apparatus for printing food material comprising at least one print head and a supply system for continuously supplying at least one print material to the or each print head in a flowable state, wherein the supply system comprises at least one screw extruder.

The apparatus and/or its component parts may be substantially as described for the apparatus of the first aspect of the invention, and so may comprise any combination of the features listed therein (such as: at least one supply path which may each comprise at least one print material infeed; a print material delivery device; a conduit network; at least one print module; at least one auger pump; at least one pressure regulation device; at least one reservoir; at least one pressure-regulating reservoir; at least one pressureregulating chamber; and a temperature control system, for example) except that the or each print material delivery device may only comprise at least one screw extruder.

According to a third aspect of the invention there is provided a method of 3D printing using an apparatus of the first or second aspect of the invention comprising continuously supplying at least one print material in a flowable state to one or more print heads, and ejecting the or each print material out of the or each print head to form a 3D-printed product.

The or each print material may comprise any material which is in a flowable state at ambient temperature (e.g. room temperature), or which can be heated into a flowable state (and may be in a molten or heated state during the method).

The or each print material may comprise a polymeric material, an elastomeric material, a plastic material, a plastics material or a food material. In preferred embodiments the print material is a confectionery material. In some embodiments, the confectionery material may be selected from the group comprising chocolate, chewing gum and candy. The candy may be chewy candy, jelly candy, nougat, toffee, caramel, fondant, hard boiled candy or the like, for example. In especially preferred embodiments, the confectionery material is chocolate, such as milk chocolate, dark chocolate, white chocolate or compound chocolate.

The method may comprise adding the or each print material into the or each print material infeed in a flowable, semi-flowable, liquid, softened or solid state (such as pellets, granules or powder). In embodiments where chocolate is a print material, the chocolate may be fed into the or each print material infeed as pieces of chocolate material such as chocolate granules, powder, pellets or shavings.

In embodiments wherein the or each print head comprises a screw-containing pump, the method may comprise controlling the rotation speed of the or each pump in order to control the extrusion speed of material out of the or each pump (or ejection out of a nozzle attached to the end of the or each auger pump). In preferred embodiments comprising a plurality of print heads comprising screw-containing pumps, the method may comprise individually controlling the rotation speed of each pump in order to vary the rate of extrusion out of each pump (or of ejection out of a nozzle attached to each auger pump). The or each screw-containing pump may be an auger pump or a progressive cavity pump.

The method may comprise regulating the back pressure of the or each print material to the or each print head using at least one pressure regulation device, such as at least one pressure-regulating chamber, at least one pressure-regulating reservoir and/or at least one screw-containing extruder (such as at least one screw extruder). The method may comprise regulating the back pressure of the or each print material to the or each print head by actuating the or each piston within the or each pressure regulation device (such as a cylinder and piston, as described hereinabove) and/or pressureregulating reservoir, by varying the volume of the or each adjustable volume device and/or adjustable volume reservoir, and/or controlling flow (e.g. extrusion rate) through the at least one screw-containing extruder.

The method may therefore comprise moving the or each piston to increase the available volume of the pressure-regulating device it is located in, and/or increasing the available volume of the or each adjustable volume device (e.g. chamber or reservoir), such that it can hold more print material and thus reduces the pressure of the or each print material within the device and/or the apparatus. The opposite can be achieved (i.e. increase in print material pressure) by decreasing the available volume in the or each device by operating the pressure regulation device in the opposite direction.

The or each pressure-regulating device may apply pressure to the or each print material so as to pressurise the or each print material and thus regulate the back pressure of the or each print material to the or each print head.

In some embodiments, the method comprises regulating the back pressure using at least one screw extruder. In preferred embodiments, the method comprises regulating the back pressure substantially only using at least one screw extruder.

The method may comprise controlling the flow rate of the or each print material through the apparatus. In some embodiments, the method comprises controlling the rate of flow through the or each screw-containing extruder. In such embodiments, the method may comprise varying the rate of rotation of the screw(s) of the or each screw extruder in order to control the rate of extrusion out of the extruder. In some embodiments, the method comprises turning the or each screw-containing extruder on and off at particular time intervals in order to achieve the desired flow rate. In some embodiments, the method comprises adjusting the flow rate of the or each print material through the or each extruder into the or each conduit network to substantially match the rate of loss from the or each conduit network of the or each print material through deposition out of the or each print head. Therefore, the rate of flow through the conduit network and/or the back pressure of the or each print material may be regulated by varying the rate of flow through the or each print material delivery device (such as at least one screw extruder) instead of, or in combination with, controlling it with at least one pressure regulation chamber and/or at least one pressure-regulating reservoir.

Therefore, in some embodiments, the method may comprise regulating the back pressure using only at least one screw-containing extruder, such as screw extruder, by varying flow rate as described above. Such embodiments have the advantage that they avoid the complexity and cost involved with manufacturing, operating and maintaining apparatus which regulate the back pressure using at least one pressure-regulating chamber and/or at least one pressure-regulating reservoir.

Pressure regulation may involve monitoring and/or sensing of the back pressure of the or each print material. In some embodiments, the back pressure may be monitored by at least one pressure sensor and/or at least one force sensor located inside or otherwise operably connected to at least one part of the apparatus, such as at least one pressure regulating chamber, at least one pressure-regulating reservoir and/or the central conduit (which may include any branches thereof). Any piston located inside a pressure regulation device may be operably connected to at least one pressure and/or force sensor.

In some embodiments, the back pressure and/or volume of the or each print material inside a pressure-regulating chamber or reservoir comprising a piston may be monitored by monitoring the level or position of the piston. In some embodiments, the back pressure and/or volume of the or each print material inside a pressure-regulating chamber or reservoir comprising an adjustable volume chamber or reservoir may be monitored by monitoring the volume, position and/or configuration of the adjustable volume chamber or reservoir.

In preferred embodiments, the method comprises monitoring the position of at least one piston, and at least partially refilling the associated pressure-regulating chamber(s) or reservoir(s) when the piston(s) falls below a threshold height/position. Refilling may comprise temporarily increasing the extrusion rate through the or each print material delivery device, such as the or each screw extruder.

Data from sensors and monitoring devices located throughout the apparatus can then be used to allow appropriate control over various apparatus parameters, such as flow rate, extrusion rate or piston position/movement, for example. Such control may be automated, for example wherein data from the one or more sensors is fed to a control system, such as a computer control system, to automatically actuate parts of the device appropriately to maintain desired print material parameters, such as pressure, flow rate and/or volume, for example. In other embodiments, the or each sensor and/or monitoring device may trigger a direct response from a component(s) of the apparatus, for example when a piston in a pressure-regulating chamber or reservoir falls below a threshold height/distance, the sensor may send a signal directly to the at least one screw extruder to increase the flow rate therethrough in order to fill the cylinder up again.

In some embodiments, the method may comprise controlling the temperature of the print material (by either heating or cooling it with a temperature control system) during its residence time within the apparatus. The method may comprise maintaining the temperature of the or each print material within a desired range for at least a portion of its/their residence time within the apparatus. In preferred embodiments, the method comprises maintaining the temperature of the or each print material within a desired range for substantially the entirety of its/their residence time within the apparatus.

Back pressure may be maintained at the required pressure for each application and product manufacturing run. In some embodiments, the method may comprise controlling the temperature of the or each print material before and/or after it has been added to the or each print material infeed and/or while the or each print material is resident in the or each print material infeed. In some embodiments, the method may comprise cooling the or each print material before and/or after it has been deposited into the or each print material infeed and/or while the or each print material is resident in the or each print material infeed, in order to keep it in a substantially solid state. This may be advantageous as it may at least partially mitigate (or completely prevent) the or each print material at least partially (or completely) blocking the or each print material infeed.

In some embodiments, the method may comprise controlling the temperature of the or each print material while it is in the or each print material infeed, the or each material delivery device (such as an extruder), the or each conduit network and/or the or each print module, or any combination thereof. In preferred embodiments, the method comprises controlling the temperature of substantially every surface that comes into contact with the or each print material.

In embodiments comprising one or more extruder as the material delivery device, the method may comprise cooling the or each print material while it is within the or each extruder. This may be advantageous as the grinding and mixing of the or each print material in the or each extruder may produce large amounts of heat.

Detailed Description of the Invention

In order that the invention may be more clearly understood one or more embodiments thereof will now be described, by way of example only, with reference to the accompanying drawings, of which:

Figure 1 illustrates a cross-section through an embodiment of a 3D printing apparatus of the second aspect of the invention in use in an embodiment of the method of the third aspect of the invention.

Figure 2 illustrates a cross-section through a second embodiment of a 3D printing apparatus of the first and second aspects of the invention in use in an embodiment of the method of the third aspect of the invention. Figure 3 illustrates a cross-section through a third embodiment of a 3D printing apparatus of the first and second aspects of the invention in use in an embodiment of the method of the third aspect of the invention.

Figure 4 illustrates a cross-section through a fourth embodiment of a 3D printing apparatus of the first and second aspects of the invention in use in an embodiment of the method of the third aspect of the invention.

Figure 5 illustrates a cross-section through a fifth embodiment of a 3D printing apparatus of the first and second aspects of the invention in use in an embodiment of the method of the third aspect of the invention.

Figure 6 illustrates a cross-section through a sixth embodiment of a 3D printing apparatus of the first and second aspects of the invention in use in an embodiment of the method of the third aspect of the invention.

Figure 1 illustrates a cross-section through an embodiment of a 3D printing apparatus 100 of the first or second aspect of the invention in use in an embodiment of the method of the third aspect of the invention. As can be seen in Figure

1, the apparatus 100 comprises a single flow path comprising a print material infeed, in the form of a volumetric feeder 101, connected to a print material delivery device 102, in the form of first and second single screw extruders 103, 104, arranged in succession. The second screw extruder 104 is connected to a downstream conduit network 105, which comprises a branched central conduit 106 arranged to supply print material to two print modules 107. Each print module 107 comprises five terminal conduits 108, which branch from branches 109 of the central conduit 106, with print heads 1 10 at their distal ends. Each print head 110 comprises an auger pump 1 1 1 and a nozzle 112. The apparatus further comprises a temperature control jacket in the form of a water jacket 113 arranged in contact with the outer surfaces of the second extruder 104 and the conduit network 105.

In use, print material, in the form of milk chocolate, is deposited into the volumetric feeder 101 in the form of chocolate pellets 1 14 and fed into the first screw extruder 103 where it is converted to flowable chocolate 1 18. The first extruder 103 then transports the chocolate 1 14 to the second screw extruder 104. As the chocolate 1 18 is transported by the first and second screw extruders 103, 104 it is warmed into a flowable state by heat released through grinding and mixing of the chocolate 1 18 and chocolate pellets 1 14, and may also be warmed by the water jacket 1 13. In other embodiments, the temperature of the water jacket 1 13 may be adjusted so that it instead cools the chocolate 1 18, if there is too much heat being generated in the screw extruders 103, 104. When the chocolate 1 18 leaves the second screw extruder 104 it is fed into the central conduit 106 in a flowable state. The chocolate 1 18 then flows along the central conduit 106 and down the branches 109 towards each print module 107, and is thus supplied to the auger pumps 1 1 1 of the print heads 1 10. The auger pumps 1 1 1 can then be actuated (i.e. rotated) in order to carry out 3D printing by extruding chocolate 1 18 out of each auger pump 1 1 1 and depositing it out of each respective nozzle 1 12. The rotation speed of each auger pump 1 1 1 can be controlled and varied individually, and thus the extrusion and deposition rate of chocolate 1 18 can be individually and separately varied for each print head 1 10, which allows for high levels of versatility of 3D printing. In place of chocolate, other confectionery material, such as chewing gum or candy, may be used.

Figure 2 illustrates a cross-section through a second embodiment of a 3D printing apparatus 200 of the first or second aspect of the invention, in use, using an embodiment of the method of the third aspect of the invention. The apparatus 200 is substantially as described in relation to the apparatus 100 illustrated in Figure 1 (and like numbers represent like components), except that the apparatus 200 further comprises a pressure regulation system comprising a pressure regulation device in the form of a pressure-regulating cylinder 1 15. The pressure-regulating cylinder 1 15 comprises a cylinder 1 16 with a piston 1 17 located therein. The pressure-regulating cylinder 1 15 is in fluid communication with the central conduit 106 and is located between the second screw extruder 104 and the first branch 109 of the central conduit 106 (which flows into the five terminal conduits 108 and print heads 1 10 of the first print module 107).

In use, the apparatus 200 works substantially in the same way as described in relation to the apparatus 100 illustrated in Figure 1 , except that the back pressure of the chocolate 1 18 to the print heads 1 10 is regulated by the pressureregulating cylinder 1 15.

In use, chocolate 1 18 is delivered into the conduit network 105 by the second extruder 104, and a portion of it resides within the cylinder 1 16 of the pressureregulating cylinder 1 15 so that it contacts the piston 1 17. The piston 1 17 is operable to move up and down within the cylinder 1 16 in order to regulate the back pressure of the chocolate 1 18 to the print heads 1 10. For example, if there is a period of time in which chocolate 1 18 is being fed into the conduit network 105 by the second extruder 104 at a faster rate than it is being removed via the print heads 1 10 (i.e. being used to 3D print a product), then the piston 1 17 may move upwards within the cylinder 1 16 to increase the volume of the cylinder 1 16 (and therefore the conduit network 105) that is in fluid communication with the print heads 1 10, and thus take up the extra chocolate 1 18 and at least partially mitigate any increase in back pressure of the chocolate 1 18 to the print heads 1 10. Conversely, if there is a period of time in which chocolate 1 18 is being removed from the conduit network 105 via the print heads 1 10 at a faster rate than it is being fed into it by the second extruder 104, then the piston 1 17 may move downwards in the cylinder 1 16 to decrease the volume of the cylinder 1 16 that is in fluid communication with the print heads 1 10, and therefore at least partially mitigate any decrease in back pressure of the chocolate 1 18 to the print heads 1 10.

Figure 3 illustrates a cross-section through a third embodiment of a 3D printing apparatus 300 of the first or second aspect of the invention in use in an embodiment of the method of the third aspect of the invention. The apparatus 300 is substantially as described in relation to the apparatus 200 illustrated in Figure 2 (and like numbers represent like components), except that the print material delivery device 302 of the apparatus 300 only comprises one single screw extruder 304 which is directly connected to the volumetric feeder 101 and the conduit network 105, and comprises a pressure-regulating cylinder 215 (comprising a cylinder 216 and a piston 217 located therein) with a larger volume, and which is instead located between the branches 109 of the central conduit 106.

In use, the apparatus 300 works substantially in the same way as described in relation to the apparatus 200 illustrated in Figure 2. However, due to the larger volume of the cylinder 216 of the apparatus 300, the cylinder 216 is able to take up a larger volume of chocolate 1 18 in one go. This may be advantageous as it may allow the cylinder 216 to take up enough chocolate 1 18 for an entire printing run (and the volume of the cylinder may be adapted in order to hold enough chocolate, depending on the desired length of a printing run), and allows the extruder 304 to be run at a much higher rate. This has the advantage that the volumetric feeder 101 (such as a hopper) may only need to be filled up once for an entire printing run, for example at the beginning of the day for a day-long printing run. This therefore saves on effort and storage required to operate the apparatus, and means that an operator can spend more time on other tasks, such as packaging printed objects.

The position of the cylinder 216 also helps to ensure that the changes in back pressure caused by operation of the piston 217 are more evenly distributed between the branches 109 of the central conduit 106, and therefore between the two print modules 107, when compared to the cylinder positioning in the embodiment of Figure 2.

Figure 4 illustrates a cross-section through a fourth embodiment of a 3D printing apparatus 400 of the first or second aspect of the invention in use in an embodiment of the method of the third aspect of the invention. The apparatus 400 is substantially as described in relation to the apparatus 300 illustrated in Figure 3, except that the conduit network 105 comprises a pressure-regulating reservoir 415 instead of a pressureregulating cylinder. The pressure-regulating reservoir 415 comprises a reservoir 416 and a piston 417 located therein. The reservoir 416 has a much larger volume than the cylinder 216 of the apparatus 300 illustrated in Figure 3.

In use, the piston 417 is may move up and down the reservoir 416 to provide pressure regulation in a similar way as described in relation to the apparatus 300 illustrated in Figure 3.

Figure 5 illustrates a cross-section through a fifth embodiment of a 3D printing apparatus 500 of the first or second aspect of the invention in use in an embodiment of the method of the third aspect of the invention. The apparatus 500 is substantially as described in relation to the apparatus 200 illustrated in Figure 2 (and like numbers represent like components), except that the apparatus 500 further comprises pressureregulating cylinders 501 attached to the first and second branches 109 of the central conduit 106, and pressure-regulating cylinders 502 attached to a terminal conduit 108 of each print module 107.

In other embodiments, a pressure-regulating cylinder 502 could be positioned on more than one terminal conduit 108 of at least one print module 107, or there could be a pressure-regulating cylinder 502 positioned on every terminal conduit 108 of at least one print module 107, or both/all print modules 107.

In use, the pressure-regulating cylinders 501 , 502 work in essentially the same way as described above in relation to the pressure-regulating cylinder 1 15 of the apparatus 200 illustrated in Figure 2. However, having extra pressure-regulating cylinders 501 , 502 located at various points along the conduit network 105 allows more- localised variations in chocolate 1 18 back pressure to be compensated for more effectively.

Figure 6 illustrates a cross-section through a third embodiment of a 3D printing apparatus 600 of the first or second aspect of the invention in use in an embodiment of the method of the third aspect of the invention. The apparatus 600 is substantially as described in relation to the apparatus 400 illustrated in Figure 4 (and like numbers represent like components), except that instead of a single pressure-regulating reservoir there are multiple pressure regulating reservoirs 615. The pressure regulating reservoirs 615 are positioned along the central conduit 106, and act as branch points of the central conduit 106, as branches 109 extend therefrom.

In use, the pistons 617 within the reservoirs 616 may be operated to provide pressure regulation in substantially the same way as described hereinabove. The use of more than one reservoir allows for greater/fmer control over back pressure regulation to the print heads, as the pressure change created by a particular reservoir 615 is more localised to branches which branch therefrom. Therefore, operating the reservoirs 615 individually allows for finer control of back pressure within a particular branch (or branches) and any conduits and/or print modules/heads located downstream thereof.

The above embodiments are described by way of example only. Many variations are possible without departing from the scope of the invention as defined in the appended claims.