An additive printing device

Abstract

An additive printing device 1 comprising a first container 2 for storing pellets 11, and a release device 19 for releasing pellets from the first container, an extruder mount (4, fig 3) is connected t

Description

FIELD OF THE INVENTION The present invention relates to an additive printing device, for example a 3D printer. BACKGROUND OF THE INVENTION Additive printing devices are also commonly referred to as 3D printers. When using polymer pellets, the additive printing device may have a hopper for storing pellets which are delivered to an extruder or extrusion unit of the additive printing device by a supply pipe. The extrusion unit melts the pellets and ejects or extrudes the pellet material in a liquid state onto a printing bed, wherein the material subsequently solidifies to form a model. A problem is that if the extrusion unit needs to be changed then pellets are liable to spill out from where the extruder unit is disconnected from the rest of the additive printing device. It is therefore an object of the invention to improve on the known art. SUMMARY OF THE INVENTION According to the invention there is provided an additive printing device comprising: a first container for storing pellets; a release device for releasing pellets from the first container; an extruder mount connected to a motion mechanism for moving the extruder mount in three dimensions, the extruder mount having a first connector through which pellets can pass; an extruder comprising a mating second connector through which pellets can pass, the mating connector being removably connected to or mated to or with the first connector of the extruder mount to enable the extruder to be removably connected to the extruder mount, the extruder having a second container for storing pellets wherein the second container is connected to the mating second connector, and the extruder having a tool head connected to the second container, and having a heating device; and a pellet conveyor for conveying pellets from the first container to the second container via the first and second connectors when the first connector is mated to the mating second connector and when the release device releases pellets from first container, wherein the heating device is configured to melt pellets in the extruder, and the tool head is configured to extrude the molten pellet material. The release device may prevent pellets from spilling out of the additive printing device when the extruder is removed from the extruder mount. The release device may comprise a valve. The pellet conveyor may comprise at least part of the release device. At least one said conduit may comprise a flexible conduit. At least part of the flexible conduit may be housed in the motion mechanism for moving the extruder mount in three dimensions. At least one said conduit may include at least part of the release device. The release device may comprise part of a dose feed system for sending a dose or number or predetermined number of pellets from the first container to the extruder. By the dose feed system sending a dose or small number of pellets to the container of the extruder, this prevents the conduit from becoming full and being blocked with pellets. The additive printing device may include a device for moving pellets out from the at least one conduit. The additive printing device may include a device for moving pellets from the first container at least towards or to the extruder. The pellet conveyor may include the device for moving pellets from the first container at least towards or to the extruder. The dose feed system may include a timer for opening the release device for a set period time to release a dose of pellets from the first container. The dose feed system may include a device for moving a dose of pellets from the first container at least towards or to the extruder. The device for moving the dose of pellets may be activated to move the pellets when the release device is opened by the timer or is in an open state. The dose feed system may include a sensor for counting a number of pellets leaving the first container. The release device may be configured to prevent more than the dose of pellets from leaving the first container. The dose feed system may include a device for moving pellets out from the at least one conduit. The device for moving pellets may comprise a fluid compressor for injecting compressed fluid into at least one said conduit. The compressed fluid may comprise gas which may comprise air. The extruder may have an extruder pellet conveying device for conveying pellets from the second container to the tool head. The extruder pellet conveying device may comprise a screw. The heating device may be connected to or at least partially surround the tool head. The first container may have a moisture removing device for removing moisture from inside the first container. The additive printing device may include a control module or an automated or computerized processor. The control module may comprise an electronic control processor or processing device or processor unit or controller or control unit. The control module may be configured to control at least one of the release device, the motion mechanism, the device for moving pellets, the extruder pellet conveying device and the heating device. The control module may be configured to control the fluid compressor. The timer and / or the sensor of the dose feed system may be connected to the control module. DETAILED DESCRIPTION Embodiments of the invention will now be described by way of non-limiting example only and with reference to the accompanying schematic drawings, in which: Fig. 1 is a view of an additive printing device in accordance with an embodiment of the present invention; Fig. 2 is a view of the inside of the additive printing device; Fig. 3 is a view of a gantry master motion head and an extruder of the additive printing device coupled together; Fig. 4 is a perspective view of a main internal hopper of the additive printing device; Fig. 5 is a perspective view of a gantry of the additive printing device; Fig. 6 is a perspective view of the gantry master motion head and extruder uncoupled; Fig. 7 is a rear perspective view of the extruder; Fig. 8 is a front perspective view of the extruder with a front cover of the extruder being omitted; and Fig. 9 is a view showing mated connectors of the gantry master motion head and the extruder. The figures are not to scale, and same or similar reference signs denote same or similar features. An embodiment of the invention will now be described with reference to the figures. Referring particularly to Figs. 1 to 3, an additive printing device 1 has a main internal hopper or first container 2, a dose or dose feed system 3, a gantry master motion head or extruder mount 4, and a pellet extruder tool or extruder 5 removably connected to the gantry master motion head 4. The gantry master motion head 4 is mounted on a conventional gantry or motion mechanism or system 6 for moving the pellet extruder tool 5 attached to the gantry master motion head 4 in three dimensions. The additive printing device 1 has two side compartments 7, 8 with a central region or compartment 9 in between which has a printing bed 10. Access to the printing bed 10 may be via one or more doors which have been omitted from Fig. 1. In one side compartment 7 is mounted the main internal hopper 2 (see also Fig. 4) which is configured to hold pellets. The main internal hopper 2 has an upper opening in the top which is connected to an external bulk supply of pellets 11 by a flexible external bulk supply conduit 12 which has a valve 13. A supply of compressed air 14 is connected to the flexible external bulk supply conduit 12 downstream of the valve 13 wherein the supply of compressed air 14 may comprise an air compressor or pump. A level sensor 15 is located inside the main internal hopper 2. The main internal hopper 2 is connected to a dryer system or moisture removing device 16 which dries the air inside the main internal hopper 2 to remove moisture from pellets stored inside the main internal hopper 2 so as to improve the print quality of the additive printing device 1. Also in the side compartment 7 is the dose feed system 3 to which a base of the main internal hopper 2 is connected. The dose feed system 3 comprises a flexible dose feed system conduit 17 which has one end connected to a lower opening in the base of the main internal hopper 2, and the flexible dose feed system conduit 17 has a valve 19. A release device may comprise the dose feed system conduit valve 19. The opposite end of the flexible dose feed system conduit 17 is connected to one end of a through tube 20 of a “T” junction unit 21. A side tube 22 of the “T” junction unit 21 is joined to the through tube 20. The side tube 22 is connected by a conduit 23 to a supply of compressed air 24 which may comprise an air compressor or pump. In the central region 9 of the additive printing device 1 is the gantry 6 which comprises two front and two rear hollow columns 25, 26 (see also Fig. 5 which for clarity only shows one front and one rear column) wherein the columns 25, 26 are located at the comers of the printing bed 10. A frame 27 is held by the columns 25, 26 and can be raised up and down (the “z” direction) relative to the columns 25, 26 by drag chains in or by the columns 25, 26 driven by one or more motors (not shown) in a known manner wherein a lift mechanism of the gantry 6 comprises the columns 25, 26, drag chains and motor(s). The frame 27 comprises a rear rail 28 which extends between the two rear columns 26, and a pair of hollow side rails 29 which extend forward from the rear rail 28 wherein the distal end of each side rail 29 has a right-angle return 30 connecting it to a respective front column 25. A movable hollow rail 31 extends perpendicularly between the two side rails 29 and can be moved forwards and backwards (the “y” direction) by drag chains in or by the hollow side rails 29 driven by one or more motors (not shown) in a known manner. Mounted on top of the movable rail 31 is a drag chain holder 32 comprising upper and lower hollow elongate portions 33, 34 which are connected to each other at either end by arched hollow portions 35 wherein a drag chain 36 runs through the elongate and arched portions 33, 34, 35 of the holder 32. The gantry master motion head 6 is slidably mounted on the upper hollow elongate portion 33 and is connected to the drag chain 36 inside the holder 32. The gantry master motion head 4 can be slid left and right or side to side (the “x” direction) by the drag chain 36 in the holder 32 driven by a motor (not shown) in a known manner. The gantry 6 thus can move the gantry master motion head 4 in three dimensions (i.e. the “x”, “y” and “z” directions which are all perpendicular to each other). The top of the gantry master motion head 4 has an extension 37 extending or cantilevering from a rear of a main body 38 of the gantry master motion head 4 wherein the distal end of extension has a downward return 39. The width of the upper hollow elongate portion 33 of the drag chain holder 32 fits snuggly in the gap between the return 39 and the rear of the main body 38 (see particularly Fig. 3). Inside the main body 38 is a gantry master motion head outlet 40 which has at one end a hollow cylindrical male connector 41 which is inclined downwards. A flexible conduit 42 connects the gantry master motion head outlet 40 to the dose feed system 3. One end of the flexible conduit 42 is connected to the opposite end of the through tube 20 of the “T” junction unit 21 of the dose feed system 3, and an opposite end of the flexible conduit 42 is connected to an end of the gantry master motion head outlet 40 opposite to the male connector end 41. The flexible conduit 42 may be fed through one of the hollow columns 25, 26, one of the hollow side rails 29, and the hollow movable rail 31 of the gantry 4. Referring to Figs. 3 and 6 to 9, the pellet extruder tool 5 contains a pellet extruder buffer hopper or second container 43 wherein the pellet extruder buffer hopper 43 has a female mating connector 44 which protrudes from a side 54 of the pellet extruder tool 5 and is inclined upwards relative to the side 54. The female mating connector 44 is mated with the male connector 41 of the outlet 40 of the gantry master motion head 4. The female connector 44 has an annular seal 45 so that the connection between the male and female connectors 41,44 is sealed. Inside the pellet extruder buffer hopper 43 is a sensor 46. The base of the pellet extruder buffer hopper 43 is connected to a conduit 47 of a tool head 48 of the pellet extruder tool 5 below which extends through the tool head 48. The pellet extruder tool conduit 47 has a screw 49. An extruder pellet conveying device may comprise the screw 49. The tool head 48 is surrounded by a heater or heating device 50. The additive printing device 1 has a control module 51 and a timer 52 (see Fig. 2). The control module 51 is connected to the timer 52, the sensors 15, 46, the valves 13, 19, the supplies of compressed air 14, 24, the motors of the pellet extruder tool motion mechanism or gantry 6, and the screw 49 and heating device 50 of the pellet extruder tool 5. These may be wired and / or wireless connections. The control module 51 controls operation of the valves 13, 19 and screw 49, controls the supplies of compressed air 14, 24, controls the heating device 50, and controls operation of the motors of the pellet extruder tool motion mechanism 6. An interface 53, which may comprise a touchscreen or a keypad and display screen, has a wired or wireless connection to the control module 51. The timer 52 may form part of the control module 51. The timer 52 may comprise part of the dose feed system 3. The control module 51 may be controlled by a remote electronic device or a portable electronic device such as a smart phone or a tablet PC. A pellet conveyor or pellet conveyor system may comprise the conduits 19, 42 through which the pellets are conveyed from the main internal hopper 2 to the gantry master motion head 4, as well as the valve 19 and the supply of compressed air 24. A pellet conveyor or pellet conveyor system may comprise the conduit 12 through which the pellets are conveyed from the external bulk supply of pellets 11 to the main internal hopper 2. At least one of the conduits or pellet tubes 12, 19, 23, 42 may comprise a polyurethane duct. The control module 51 may comprise part of the pellet conveyor or pellet conveyor system. In use, when the sensor 46 in the pellet extruder buffer hopper 43 senses that there is an insufficient number of pellets in the hopper 43, the sensor 46 communicates with the control module 51 which activates the timer 52 to run for a set period of time during which the dose feed system valve 19 is opened. The time that the dose feed system valve 19 is opened for causes a dose or number of pellets to leave the main internal hopper 2. At the same time, the control module 51 causes a blast or surge of compressed air from the supply of compressed air 24 for the dose feed system 3 to be sent through the flexible conduit 42 to convey the dose of pellets to the pellet extruder buffer hopper 43 of the pellet extruder tool 5 via the gantry master motion head outlet 40. When the timer 52 has finished running for the set time the dose feed system valve 19 is closed. If desired, a blast or surge of compressed air from the supply of compressed air 24 for the dose feed system 3 may be sent through the flexible conduit 42 to flush the flexible conduit 42 removing any pellets therein. The control module 51 causes the pellet extruder tool screw 49 to rotate to move pellets from the pellet extruder buffer hopper 43 into the tool head 48, and the heating device 50 melts the pellets. The motors of the gantry or pellet extrusion tool motion mechanism 6 are selectively activated to move the frame 27 relative to the columns 25, 26, move the movable rail 31 relative to the frame 27 and move the gantry master motion head 4 relative to the movable rail 31 so that the tool head 48 of the pellet extruder tool 5 can be moved as it extrudes pellet material in a liquid state onto the printing bed 10 so that a model can be formed. If the pellet extruder tool 5 is to be changed then the dose feed system valve 19 is closed and a blast or surge of compressed air from the dose feed system supply 24 is sent through the flexible conduit 42 to clear any pellets in the flexible conduit 42 into the pellet extruder buffer hopper 43. The pellet extruder tool 5 is then disconnected from the gantry master motion head outlet 40 with the male connector 41 disconnected from the female connector 44. Pellets from the main internal hopper 2 are prevented from spilling out by the closed dose feed system valve 19. Another pellet extruder tool is then connected to the gantry master motion head outlet 40 with the male connector 41 being mated with the female connector of the pellet extruder tool wherein the tool head may be different. Another dose of pellets may then be sent from the main internal hopper 2 to the pellet extruder tool via the gantry tool motion head outlet 40. If the level sensor 15 detects that the amount of pellets in the main internal hopper 2 is low then the external bulk supply conduit valve 13 is opened and a supply of compressed air 14 is applied to the external bulk supply conduit 12 to move pellets from the external bulk supply of pellets 11 to the main internal hopper 2. A modified additive printing device may have a light sensor for counting pellets leaving the main internal hopper. The light sensor may be part of the dose feed system conduit, and the dose feed system valve may be closed when a required number of pellets for the dose has been counted by the light sensor leaving the main internal hopper. Many other variations of the described embodiments falling within the scope of the invention will be apparent to those skilled in the art. Any suitable means may be used to convey pellets from the main internal hopper to the pellet extruder tool.

Claims

1. An additive printing device comprising:a first container for storing pellets;a release device for releasing pellets from the first container;an extruder mount connected to a motion mechanism for moving the extruder mount in three dimensions, the extruder mount having a first connector through which pellets can pass;an extruder comprising a mating second connector through which pellets can pass, the mating connector being removably connected to the first connector of the extruder mount to enable the extruder to be removably connected to the extruder mount, the extruder having a second container for storing pellets wherein the second container is connected to the mating second connector, and the extruder having a tool head connected to the second container, and having a heating device; anda pellet conveyor for conveying pellets from the first container to the second container via the first and second connectors when the first connector is mated to the mating second connector and when the release device releases pellets from first container,wherein the heating device is configured to melt pellets in the extruder, and the tool head is configured to extrude the molten pellet material.

2. The additive printing device of claim 1, wherein pellet conveyor includes at least part of the release device.

3. The additive printing device of claim 1 or 2, wherein the pellet conveyor comprises at least one conduit.

4. The additive printing device of claim 3, wherein at least one said conduit comprises a flexible conduit.

5. The additive printing device of any preceding claim, including a device for moving pellets from the first container at least towards the extruder.

6. The additive printing device as claimed in claim 5, wherein the pellet conveyor includes the device for moving pellets from the first container at least towards the extruder.

7. The additive printing device of any one of claims 1 to 4, wherein the release device comprises part of a dose feed system for sending a dose of pellets from the first container to the extruder.

8. The additive printing device of claim 7, wherein the dose feed system includes a timer for opening the release device for a set period time to release a dose of pellets from the first container.

9. The additive printing device as claimed in claim 7 or 8, wherein the dose feed system includes a device for moving a dose of pellets from the first container at least towards the extruder.

10. The additive printing device as claimed in claim 9 when dependent on claim 8, wherein the device for moving the dose of pellets is activated to move the pellets when the release device is opened by the timer.

11. The additive printing device as claimed in claim 7, wherein the dose feed system includes a device for moving pellets out from the at least one conduit.

12. The additive printing device of claim 5, 6, 9, 10 or 11 when dependent on claims 3 or 4, wherein the device for moving pellets comprises a fluid compressor for injecting compressed fluid into at least one said conduit.

13. The additive printing device of any preceding claim, wherein the extruder has an extruder pellet conveying device for conveying pellets from the second container to the tool head.

14. The additive printing device of any preceding claim, wherein the first container has a moisture removing device for removing moisture from inside the first container.

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