WO2022093019A1 - Régulation de débit dans une tête d'extrudeuse - Google Patents

Régulation de débit dans une tête d'extrudeuse Download PDF

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Publication number
WO2022093019A1
WO2022093019A1 PCT/NL2021/050652 NL2021050652W WO2022093019A1 WO 2022093019 A1 WO2022093019 A1 WO 2022093019A1 NL 2021050652 W NL2021050652 W NL 2021050652W WO 2022093019 A1 WO2022093019 A1 WO 2022093019A1
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WO
WIPO (PCT)
Prior art keywords
heat
extruder head
cylinder
extruder
peltier device
Prior art date
Application number
PCT/NL2021/050652
Other languages
English (en)
Inventor
Marcus Arnoldus Hubertus Gerardus JOOSEN
Original Assignee
Ultimaker B.V.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Ultimaker B.V. filed Critical Ultimaker B.V.
Publication of WO2022093019A1 publication Critical patent/WO2022093019A1/fr

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/02—Small extruding apparatus, e.g. handheld, toy or laboratory extruders
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/255—Flow control means, e.g. valves
    • B29C48/2556—Flow control means, e.g. valves provided in or in the proximity of dies
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/266—Means for allowing relative movements between the apparatus parts, e.g. for twisting the extruded article or for moving the die along a surface to be coated
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/78—Thermal treatment of the extrusion moulding material or of preformed parts or layers, e.g. by heating or cooling
    • B29C48/86—Thermal treatment of the extrusion moulding material or of preformed parts or layers, e.g. by heating or cooling at the nozzle zone
    • B29C48/87—Cooling
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/92—Measuring, controlling or regulating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C64/00—Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
    • B29C64/10—Processes of additive manufacturing
    • B29C64/106—Processes of additive manufacturing using only liquids or viscous materials, e.g. depositing a continuous bead of viscous material
    • B29C64/118—Processes of additive manufacturing using only liquids or viscous materials, e.g. depositing a continuous bead of viscous material using filamentary material being melted, e.g. fused deposition modelling [FDM]
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C64/00—Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
    • B29C64/20—Apparatus for additive manufacturing; Details thereof or accessories therefor
    • B29C64/205—Means for applying layers
    • B29C64/209—Heads; Nozzles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y10/00—Processes of additive manufacturing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y30/00—Apparatus for additive manufacturing; Details thereof or accessories therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C35/00—Heating, cooling or curing, e.g. crosslinking or vulcanising; Apparatus therefor
    • B29C35/16—Cooling
    • B29C2035/1608—Cooling using Peltier-effect
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2948/00—Indexing scheme relating to extrusion moulding
    • B29C2948/92—Measuring, controlling or regulating
    • B29C2948/92009—Measured parameter
    • B29C2948/92209—Temperature
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2948/00—Indexing scheme relating to extrusion moulding
    • B29C2948/92—Measuring, controlling or regulating
    • B29C2948/92323—Location or phase of measurement
    • B29C2948/92361—Extrusion unit
    • B29C2948/92409—Die; Nozzle zone
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2948/00—Indexing scheme relating to extrusion moulding
    • B29C2948/92—Measuring, controlling or regulating
    • B29C2948/92504—Controlled parameter
    • B29C2948/9258—Velocity
    • B29C2948/926—Flow or feed rate
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2948/00—Indexing scheme relating to extrusion moulding
    • B29C2948/92—Measuring, controlling or regulating
    • B29C2948/92504—Controlled parameter
    • B29C2948/92704—Temperature
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2948/00—Indexing scheme relating to extrusion moulding
    • B29C2948/92—Measuring, controlling or regulating
    • B29C2948/92819—Location or phase of control
    • B29C2948/92857—Extrusion unit
    • B29C2948/92904—Die; Nozzle zone

Definitions

  • the present invention relates to an extruder head for a fused filament fabrication printing system.
  • the invention also relates to a fused filament fabrication printing system comprising such an extruder head.
  • the invention relates to a method of FFF printing using such a fused filament fabrication printing system.
  • Fused filament fabrication is a 3D printing process that uses a continuous filament of a thermoplastic material.
  • the filament is fed from a filament supply through a heated extruder head and is deposited through a print nozzle onto an upper surface of a build surface.
  • the extruder head also referred to as print head
  • the extruder head may be moved relative to the build surface under computer control to define a printed shape.
  • the extruder head moves in two dimensions to deposit one horizontal plane, or layer, at a time.
  • the build surface, or the extruder head is then moved vertically by a small amount to begin a new layer. In this way a 3D printed object can be produced made out of a thermoplastic material.
  • a 3D object can be made using more than one 3D printable material.
  • the materials may be selected fortheir properties, which make them suitable for a particular purpose, including but not limited to colour, flexibility, tensile strength, wear resistance etc.
  • the combination of multiple materials can significantly increase the usefulness of the 3D printed object.
  • many layers of such a multi-material object consist of more than one material. This requires switching between materials at least once per layer.
  • An extruder that is currently not in use but is kept at the flowing temperature for the material that it contains may extrude material undesirably.
  • melt channel must be filled (primed) to resume printing with a known flow.
  • melt chamber i.e. hot-end
  • melt chamber i.e. hot-end
  • Flow control of the liquid material is not much easier. While it would allow fast response, it requires valves or other mechanical moving parts in the 'melt' which make the extruder head more complex and heavier.
  • Patent publication US6578596 B1 describes an extruder head comprising a heat chamber arranged inside a heated body, wherein thermoplastic filament is molten inside the heated chamber and wherein the molten filament is then guided through a flow tube towards a discharge orifice.
  • a so-called valving region of the flow tube is cooled in order to locally remove heat from the flow tube, thereby solidifying the molten material inside the flow tube, shutting off the flow of material.
  • the described device is employed to control a thermoplastic flow through the discharge orifice by selectively removing heat from the valving region in the following manner.
  • the heated body is maintained at a temperature at which the thermoplastic is flowable, thereby maintaining the flow channel at flowable temperature in the inlet and outlet regions of the flow tube.
  • a flow of coolant having a temperature lower than the lowest flowable temperature of the thermoplastic is selectively and controllably provided to a coolant inlet tube to valve on and off the flow channel.
  • the above described arrangement involves a separate cooling unit which is connected to the extruder head via a number of tubes needed to supply the fluid coolant.
  • This additional cooling unit and the accompanying tubing make the arrangement rather complex to fabricate and makes it prone to failure.
  • the switching ‘on’ of the valve i.e. opening it
  • This solution may be too slow for certain applications, and is in fact not fully controllable.
  • the aim of the present invention is to provide an extruder head wherein a flow of molten filament material to the orifice of the nozzle can be blocked and unblocked, wherein at least one of the problems of the state of the art extruder head is solved.
  • an extruder head for a Fused Filament Fabrication printing system.
  • the extruder head comprises an extruder channel and a heating element for heating part of the extruder channel so as to melt a printing material, wherein the extruder channel comprises a first cylinder and a second cylinder connected to the first cylinder, optionally via an intermediate transition part.
  • An outer end of the second cylinder comprises an orifice for depositing molten printing material.
  • the extruder head further comprises a Peltier device arranged to locally cool a region of the second cylinder, also referred to as flow tube, so as to make the printing material in the region less or non-flowable.
  • the Peltier device comprises a first heat-conductive element, a second heat-conductive element, and a plurality of thermo-electric units arranged between the first and second heat-conductive element.
  • the Peltier device is arranged to receive an electrical current in a first direction so as to cool down the region of the second cylinder if material flow out of the orifice needs to be stopped, and receive another current in a second direction opposite of the first direction so as to heat the region if the material flow out of the orifice needs to restart.
  • the flow tube can be blocked and unblocked by suitable control of the Peltier device.
  • the Peltier device only needs two power cables which is less prone to failure as compared to the tubing of the prior art systems.
  • the Peltier device can also be used to reverse the heat flow so as to heat up the flow tube, which makes the valving on considerably faster as compared to the known systems.
  • the present invention enables a faster control of the flow of material. The ability to quickly valve off the flow of material when an extruder will be unused for some time, and to quickly resume the flow, may improve the print result, both in surface finish and part strength, as well as improve productivity.
  • the second cylinder has a smaller inner diameter as compared to the first cylinder.
  • An intermediate transition part may be arranged between the first and second cylinder to provide for a transition from a first diameter of the first cylinder to a smaller second diameter of the second cylinder.
  • each of the first and second heat-conductive elements is a flat plate having a central hole, the first and second heat-conductive elements being arranged in parallel, wherein the second cylindrical part of the extruder channel extends through the holes of the first and second heat-conductive elements, and wherein the first heat-conductive element are in contact with the second cylindrical part but the second heat-conductive element is not in contact with the second cylindrical part.
  • a number of cooling fins are arranged at an outer surface of the second heat-conductive element. These cooling fins will result in a faster cooling of the second heat-conductive element, and will thus speed up the blocking of the valve region.
  • each of the first and second heat-conductive elements comprises a cylinder, the first and second heat-conductive elements being co-axially arranged around at least a part of the second cylindrical part of the extruder channel.
  • a number of cooling fins may be arranged around the second heat-conductive element to improve the cooling process.
  • the Peltier device may be a disc-shaped device wherein heat is pumped in and out in a radial direction. This configuration may allow a more compact construction measured along the axis of the flow tube than the parallel-plate configuration mentioned above.
  • each of the number of thermo-electric units has four flat outer surfaces and two curved outer surfaces so as to fill up a space in between two co-axially arranged cylinders with different diameters. Using such rounded wedge-shaped units provides for an optimal heat transfer between the first and second heat conductive elements.
  • the heating element comprises a heat conductive sleeve which is in contact with part of first cylinder and with the second heat-conductive element.
  • the second cylinder has an inner diameter in a range between 0.2 mm - 1 .5 mm. These dimensions showed good results during tests.
  • a fused filament fabrication printing system comprising at least one extruder head as describe above.
  • the printing system may comprise a controlling system arranged to control the Peltier device.
  • This controlling system may also be arranged to control other functions of the printing system such as heating the build surface, moving the gantry and/or controlling the feeders.
  • the controlling system may be arranged within a housing of the printing system. Parts of the controlling system may be arranged in or on the extruder head, and complementary parts may be arranged elsewhere such as in an inner space of the system near the bottom or walls.
  • the controlling system is arranged to control the Peltier device so as to cool down the region of the second cylinder if material flow out of the extruder head needs to be stopped, and heat the region if the material flow out of the extruder head needs to restart.
  • the controller may be arranged to control the Peltier device using e.g. a lookup table that comprises information on the value of the electrical current needed, and the time needed to sufficiently stop the flow of material, and the same may account for the heating to unblock the extruder heads.
  • the lookup table may contain heuristic data gathered during experiments to fine tune the process for different printing materials.
  • the lookup table may be stored in a memory of the controlling system.
  • the controlling system may further comprise a scheduler that plans changes in current such that the desired channel temperature is reached at the desired time.
  • controlling system is arranged to control the Peltier device so as to adjust the flow of material through the second cylinder by properly adjusting an electrical current through the Peltier device.
  • a method of FFF printing comprising:
  • Figure 1 schematically shows a cross section of a part of an extruder head according to an embodiment of the invention
  • Figure 2 schematically shows a perspective view of the Peltier device according to the embodiment of Figure 1 ;
  • Figure 3 shows a further embodiment of the extruder head with a different Peltier device
  • Figure 4A shows a perspective view of the Peltier device according to an embodiment
  • Figure 4B schematically shows a cross section of the Peltier device of Figure 4A in a plane perpendicular to a main axis of the flow tube;
  • Figure 5 shows a further embodiment of the extruder head wherein the Peltier device is enclosed by an extended heater that envelops the melt chamber as well as part of the flow tube;
  • Figure 6 shows yet a further embodiment of the extruder head wherein the Peltier device is enclosed by an extended heater that envelops the melt chamber as well as most part of the flow tube;
  • FIG. 7 schematically shows a fused filament fabrication (FFF) printing system according to an embodiment of the invention.
  • Figure 8 shows a flow chart of a method of FFF printing according to an embodiment of the invention.
  • FIG 1 schematically shows a cross section of a part of an extruder head 1 according to an embodiment of the invention.
  • the extruder head 1 comprises an extrusion channel embodied by a first cylindrical part 2, an intermediate part 3, and a second cylindrical part 4.
  • the first cylindrical part 2 has an inner diameter d1 and the second cylindrical part 4 has an inner diameter d2, wherein d2 is smaller than d1 .
  • the second cylindrical part 4 is thinner than the first cylindrical part 2.
  • a typical value for the inner diameter d2 lies in a range between 0.2 mm and 1 .5 mm.
  • the thinner part 4 is also referred to as the flow tube 4.
  • the flow tube 4 has an orifice for depositing molten plastic material which may have a bore diameter smaller than d2.
  • the extruder head 1 is supplied with a filament 6 by means of a filament feeder (not shown in Figure 1).
  • the extruder head 1 comprises a heating element 7 for heating part of the extruder channel.
  • the heating element 7 may be controlled by a controlling system (not shown in Figure 1) in orderto make the filament 6 melt when it arrives in the hot-end of the extruder head 1 .
  • Figure 1 shows molten material 8 within the hot-end.
  • the extruder head 1 also comprises a cooling element 9 for keeping the extruder channel sufficiently cold at the so-called cold-end of the extruder head 1 .
  • the cooling element 9 may comprise a number of cooling fins arranged around the extruder channel, which fins may be cooled by forced air coming from one or more fans (not shown in Figure 1).
  • the first cylindrical part 2 comprises a heat break 16.
  • the heat break 16 is thermally separating the cold-end from the hot-end as will be appreciated by the skilled reader.
  • the heat break 16 is a relatively thin part of the cylinder 2 and is made out of the same material. It is noted that the heat break 16 may be manufactured out of a different material.
  • the extruder head 1 further comprises a Peltier device 10 arranged to locally cool a valve region 11 of the second cylinder 4.
  • the Peltier device 10 comprises a first heat conductive element 12, a second heat conductive element 13, and a plurality of thermo-electric units 14 arranged between the heat conductive elements 12, 13.
  • the Peltier device 10 further comprises a number of cooling fins 25 which are arranged on the second heat conductive element 13.
  • the thermo-electric units 14 may comprise a number of P-type thermo-electric units and a number of N-type thermo-electric units which are connected electrically in series and thermally in parallel. If the thermo-electric units are connected to a power supply, a current passes through the thermo-electric units 14, and the Peltier device 10 will start working as a heat pump, wherein heat is transported from the first heat-conductive element 12 to the second heat-conductive element 13, or vice versa depending on the direction of the current.
  • the flow tube 4 When no current is applied to the Peltier device 10, the flow tube 4 will be heated by the heat coming from the heating element 7 via the heat conductive first cylindrical part and the intermediate part 3. Once the current is applied to the Peltier device 10, the first heat conductive element 12 will become cold. Heat coming from the flow tube 4 is transferred through the Peltier device 10 to the second heat conductive element 13. Due to the relatively low thermal mass and its small diameter, the flow tube 4 can be cooled off very fast. As a result, the specially arranged Peltier device 10 around the cooling section 11 of the flow tube 4 can quickly cool down a small amount of material in the valve region 11 below the glass transition temperature, thereby providing a fast flow control of this ‘freeze valve’.
  • the feed rate of the filament feeder is such as to allow for thermal expansion of the material that was recently brought into the hot-end. Retracting the solid filament will be required to allow for this expansion.
  • a control system (see also Figure 7) may be arranged to schedule the filament retraction and Peltier current based on knowledge of the thermal properties of the flow tube and the material being used.
  • thermoelectric units comprise both P- and N-type materials units which are connected electrically in series and thermally in parallel.
  • the Peltier effect occurs when current flows between two dissimilar conductors or semiconductors. When this occurs, the charge carriers flowing through the material will transfer heat from one side to the other, allowing this effect to be used to create a heat pump having no moving mechanical parts, gases or fluids. This makes it very low maintenance and in principle completely vibration-free.
  • the first and second cylinder forming the extrusion channel are in fluidic communication and may share the same axis. However, the first and second cylinder do not need to be aligned or colinear. Alternatively, they may have different orientations, such as described in the prior art wherein the axis of the second cylinder is perpendicular to the axis of the first cylinder.
  • the Peltier device only needs to cool down the material from the printing temperature to a non-flowing temperature.
  • PLA may be printed using a printing temperature of around 210°C, and will be less or non-flowable in the range of 120°C to 170°C. So, when cooling the PLA material in the valve region to around 160°C, the valve will get blocked. This means cooling off of the flow tube with only 50°C.
  • the printing temperature may be about 215°C, but the non-flowing temperature needs to be lower than 150°C, so the valve tube needs to be cooled about 65°C which is a larger cooling step as compared to PLA, but still relatively small.
  • the Peltier device only has to create this relatively small temperature difference to obtain the flow control effect.
  • the efficiency of a Peltier device depends strongly on the temperature difference between the hot and cold terminals of the device: the efficiency decreases sharply with an increased temperature gradient.
  • the outside of the Peltier device 10 can be maintained at an elevated temperature rather than the ambient temperature in the vicinity of the extruder head.
  • the heater 7 and the Peltier device 10 are not in contact and thus thermally separated. In this case it is assumed that the airflow along the hot-end (which may be forced by a fan) is sufficient to keep the outside of the Peltier device 10 at a useful temperature.
  • the airflow may actually be the other way around if this part of the hot-end is inside an insulated compartment and convection or radiation from the build compartment dominates the air flow around heater 7. Even without forced airflow this arrangement may work.
  • a temperature sensor 15 may be arranged on the outer surface of the flow tube 4 so as to measure the temperature near the valve region 11 which may be used to control the current of the Peltier device 10.
  • a further temperature sensor may also be arranged at or in the heating element 7 to measure the temperature of the melt chamber (not shown in Figure 1).
  • Figure 2 schematically shows a perspective view of the Peltier device 10 according to the embodiment of Figure 1 .
  • Figure 2 shows the first heat-conductive element 12 and the second heat-conductive element 13 where both elements 12,13 are flat plates having a central hole, one of which is visible, see hole 23 in the second heat conductive element 13.
  • Both heat-conductive elements 12, 13 are arranged in parallel, having the thermo-electric units sandwiched in between except for a central region where no thermo-electric units are located.
  • the second cylindrical part 4 of the extruder channel extends through the holes of the first and second heat-conductive elements. It is noted that the first heat-conductive element 12 is in contact with the second cylindrical part but the second heat-conductive element 13 is not in contact with the second cylindrical part 4.
  • the heat-conductive plates 12, 13 can be made from a metal such as copper or bronze, but it may alternatively be made out of a ceramic material. Other materials are conceivable as will be appreciated by the skilled person.
  • FIG. 3 shows a further embodiment of the extruder head 1 with a different Peltier device 30.
  • the Peltier device 30 comprises two cylindrical shaped conductive elements 32, 33. In between the cylindrical shaped conductive elements 32, 33, a number of thermo-electric units 34 is arranged. A first heat-conductive element 32 is arranged around the flow tube 4, whereas a second heat-conductive element 33 is arranged around the first heat-conductive element 32 and in contact with cooling fins 35.
  • the thermo-electric units 34 are arranged between the cylindrical shaped conductive elements 32, 33.
  • Figure 4A shows a perspective view of the Peltier device 30 according to an embodiment.
  • the Peltier device 30 is substantially disc-shaped and has a hole 36 in the centre.
  • Figure 4B schematically shows a cross section of the Peltier device 30 in a plane perpendicular to a main axis of the flow tube 4.
  • Figure 4B shows a number of P-type thermo-electric units 34 and a number of N-type thermo-electric units 34’ which are connected electrically in series and thermally in such a way that heat is pumped in a centrifugal direction or in a centripetal direction.
  • the arrows in Figure 4B indicate a situation wherein heat flows in the centrifugal direction.
  • thermo-electric units 34, 34’ are connected to an electrical power supply, an electric current passes through the thermo-electric units 34, 34’ and the Peltier device 30 will start working as a heat pump, wherein heat is transported from the first heat-conductive element 32 to the second heat-conductive element 33, or vice versa depending on the direction of the current.
  • the flow tube 4 is inserted into the hole 36 of the Peltier device 30.
  • the first conductive element 32 is much thicker than the second conductive element 33.
  • the thermal mass may be considerable which may be disadvantageous in case a fast switching of the freeze valve is requested.
  • this disc-shaped element may comprise one or more cut-outs so as to decrease the total mass, and thus the thermal mass.
  • a possible arrangement of cut-outs may result in the first conductive element 32 having a cross section that is similar to a wheel having spokes. The spokes will then transfer the heat in a centrifugal direction from the central part of the conductive element 32 towards the outer surface and towards the thermo-electrical units 34, 34’.
  • Figure 5 shows a further embodiment of the extruder head 1 wherein the Peltier device 30 is enclosed by an extended heater 7 that is formed as a sleeve which envelops the hot-end as well as part of the flow tube 4.
  • the sleeve may comprise a heat conductive material such as copper or brass.
  • the heat conductive sleeve 7 is in contact with part of the first cylinder 2 and with the second heat-conductive element 33.
  • Thermal separation is provided by not having the flow tube 4 in direct contact with the heater 7.
  • This arrangement allows for a stable, high reference temperature on the outside of the Peltier element, thus limiting the temperature gradient across the Peltier device and thereby improving the efficiency of the thermo-electric process.
  • Peltier devices can only transfer heat (thermal energy), they don't just set a temperature.
  • the temperature inside the valve region 11 see also Figure 3, only has to be controlled within a small range between a maximum value and a minimum value.
  • the maximum value may be the same as the temperature in the liquefier (i.e. melt chamber), whereas the minimum value needs to be only a little less so as to increase the viscosity enough to stop the flow.
  • the maximum value in the valve region can be e.g. 210°C and the minimum temperature can be e.g. 160°C.
  • Figure 6 shows yet a further embodiment of the extruder head 1 wherein the Peltier device 30 is enclosed by an extended heater 7 that envelops the hot-end as well as most part of the flow tube 4.
  • the heater 7 is a sleeve that has a narrowing close to the orifice 5 so as to enable heating of the outer end of the flow tube 4. This arrangement significantly reduces the amount of material that can flow out of the nozzle uncontrollably, while actively and accurately maintaining the temperature of the extruded material.
  • the Peltier device 30 may be used to finely control the temperature of the material before it leaves the flow tube 4, heating or cooling it as required. This is an additional advantage of the Peltier arrangement that is independent of its flow-controlling properties.
  • Peltier device 10 could be used in the configurations shown in Figure 5 and 6 with some minor amendments to the body of the heater 7.
  • FIG. 7 schematically shows a fused filament fabrication (FFF) printing system 70, also referred to as a 3D printer, according to an embodiment of the invention.
  • the 3D printer 70 comprises an extruder head 1 as described above.
  • a filament 75 is fed into the extruder head 1 (i.e. print head) by means of a feeder 73.
  • Part of the filament 75 is stored around a spool 78, which could be rotatably arranged onto a housing (not shown) of the 3D printer, or rotatably arranged within a container (not shown) containing one or more spools.
  • the 3D printer 70 comprises a controlling system 77 arranged to control the feeder 73 and the movement of the extruder head 1.
  • the controlling system 77 may comprise a memory 76 for storing instructions for printing and for controlling the Peltier device(s). The latter may be done using a lookup table containing information on how much electrical current is needed to cool or warm the Peltier devices(s) and for how long (i.e. time period) the current needs to be applied.
  • Figure 7 shows an electrical connection 80 (e.g. two power cables) through which the controlling system 77 feeds the electrical current to the Peltier device 10,30.
  • the 3D printer further comprises a Bowden tube 79 arranged to guide the filament 75 from the feeder 73 to the extruder head 1 . It is noted that alternatively the 3D printer may use a direct-drive print head, wherein the Bowden tube(s) may be absent.
  • the 3D printer 70 also comprises a gantry arranged to move the extruder head 1 at least in one direction, indicated as the X-direction.
  • the extruder head 1 is also movable in a Y-direction perpendicular to the X-direction.
  • the gantry comprises at least one mechanical driver 84 and one or more linear guides 85 and a print head docking unit 86.
  • the print head docking unit 86 holds the extruder head 1 and for that reason is also called the print head mount 86. It is noted that the print head docking unit 86 may be arranged to hold more than one extruder head, such as for example two extruder heads each receiving its own filament.
  • a build plate 88 may be arranged in or under the 3D printer 70 depending on the type of 3D printer.
  • the build plate 88 may comprise a glass plate or any other object suitable as a substrate.
  • the build plate 88 is movably arranged relative to the extruder head 1 in a Z- direction, see Figure 7.
  • material is deposited on a conveyer belt which is arranged to move perpendicular to the X-direction, and wherein the surface of the belt makes an angle with the Y-direction that is smaller than 90°, such as 45°.
  • the feeder 73 is arranged to feed and retract the filament 75 to and from the extruder head 1 .
  • the feeder 73 may be arranged to feed and retract filament at different speeds to be determined by the controlling system 77.
  • the extruder head 1 is Figure 7 comprises a Peltier device 10 in order to activate the freeze valve as was described above.
  • the Peltier device 10 is connected to the controlling system 77 so that the controlling system 77 can control the settings of the Peltier device 10 for blocking and unblocking of the flow tube of the extruder head 1 .
  • extruder 1 may alternatively be arranged in other types of fused filament fabrication printing systems, such as printing systems using delta gantries.
  • the invention is not limited to the use of specific driving means that move the extruder relative to the build plate.
  • Figure 8 shows a flow chart of a method of FFF printing according to an embodiment of the invention.
  • the method 800 comprises providing 801 a fused filament fabrication printing system as described above, and controlling 801 the Peltier device 10 so as to cool down the region 11 of the second cylinder if material flow out of the extruder head needs to be stopped, and heat the region 11 if the material flow out of the extruder head needs to restart.
  • the fused filament fabrication printing system comprises two extruder heads called A and B.
  • the extruder A may be actively printing material, while the extruder B is unused but already having a warm hot-end with molten material inside.
  • the Peltier device of extruder B is however actively cooling, so that no material comes out of extruder B (no oozing).
  • the flow tube obf the extruder A is cooled to the non-flowable temperature for the material in the extruder A and the filament is retracted from the extruder A in time, so that the flow stops.
  • the flow tube of the extruder B is heated by the Peltier device, so that the flow out of the nozzle of extruder B can start immediately once the extruder B is in the correct position. Then, the extruder A is moved away from the object, and the extruder B is moved towards it. Now, the extruder B can start printing. This process can be tuned in such a way that the flow out of the extruder B starts exactly when extruder B is in the right place. At that moment (i) the temperature of the entire melting channel is right and (ii) the material is pressurized by the feeder. Now the extruder A is inactive and may be cooled or pre-heated depending on the next printing steps to be performed.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Health & Medical Sciences (AREA)
  • Clinical Laboratory Science (AREA)
  • Thermal Sciences (AREA)
  • Extrusion Moulding Of Plastics Or The Like (AREA)

Abstract

L'invention concerne une tête d'extrudeuse pour un système d'impression FFF, comprenant un canal d'extrusion et un élément chauffant (7) pour le chauffage d'une partie du canal d'extrusion de façon à faire fondre un matériau d'impression. Le canal d'extrusion comprend un premier cylindre (2) et un second cylindre (4) raccordé au premier cylindre, facultativement par l'intermédiaire d'une pièce intermédiaire de transition (3), la tête d'extrudeuse comprenant en outre un dispositif à effet Peltier (10 ; 30) conçu pour refroidir localement une zone (11) du second cylindre de façon à rendre le matériau d'impression présent dans la zone (11) moins capable de d'écouler ou incapable de s'écouler. Le dispositif à effet Peltier comprend un premier élément thermoconducteur (12,32), un second élément thermoconducteur (13,33) et une pluralité d'unités thermoélectriques disposées entre les premier et second éléments thermoconducteurs. [Figure 1]
PCT/NL2021/050652 2020-10-29 2021-10-26 Régulation de débit dans une tête d'extrudeuse WO2022093019A1 (fr)

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NL2026789A NL2026789B1 (nl) 2020-10-29 2020-10-29 Flow control in an extruder head
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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6578596B1 (en) 2000-04-18 2003-06-17 Stratasys, Inc. Apparatus and method for thermoplastic extrusion
EP2560188A1 (fr) * 2011-08-16 2013-02-20 Leica Microsystems CMS GmbH Dispositif de détection
US20140125343A1 (en) * 2012-11-02 2014-05-08 Foxconn Technology Co., Ltd. Instrument for measuring led light source
EP3156217A1 (fr) * 2015-10-14 2017-04-19 be3D s.r.o. Ensemble extrudeuse pour une imprimante tridimensionnelle
US20180111336A1 (en) * 2016-10-26 2018-04-26 Xerox Corporation Method of operating extruder heads in three-dimensional object printers
WO2019226815A1 (fr) * 2018-05-22 2019-11-28 Markforged, Inc. Matériau de séparation apte à être fritté en fabrication additive

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6578596B1 (en) 2000-04-18 2003-06-17 Stratasys, Inc. Apparatus and method for thermoplastic extrusion
EP2560188A1 (fr) * 2011-08-16 2013-02-20 Leica Microsystems CMS GmbH Dispositif de détection
US20140125343A1 (en) * 2012-11-02 2014-05-08 Foxconn Technology Co., Ltd. Instrument for measuring led light source
EP3156217A1 (fr) * 2015-10-14 2017-04-19 be3D s.r.o. Ensemble extrudeuse pour une imprimante tridimensionnelle
US20180111336A1 (en) * 2016-10-26 2018-04-26 Xerox Corporation Method of operating extruder heads in three-dimensional object printers
WO2019226815A1 (fr) * 2018-05-22 2019-11-28 Markforged, Inc. Matériau de séparation apte à être fritté en fabrication additive

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