US-12624892-B2 - Filament drying system

US12624892B2US 12624892 B2US12624892 B2US 12624892B2US-12624892-B2

Abstract

A system ( 27 ) arranged to dry a filament ( 5 ) used in additive manufacture, the system ( 27 ) comprising: a first heater ( 55 ) arranged to heat air; a tubing section ( 29 ) having a wall ( 31 ) defining an enclosed passage ( 33 ), the passage ( 33 ) arranged to convey a filament ( 5 ), the tubing section ( 29 ) having an air inlet ( 51 ) for providing heated air from the first heater ( 55 ) into the passage ( 33 ); and a second heater ( 59 ) arranged around along at least part of the tubing section ( 29 ), in order to further heat filament ( 5 ) within the passage ( 33 ).

Inventors

Keith Azzopardi
Edward Borg

Assignees

THOUGHT3D LIMITED

Dates

Publication Date: 20260512
Application Date: 20210112
Priority Date: 20200116

Claims (20)

1 . A system arranged to dry a filament used in additive manufacture, the system comprising: a first heater arranged to heat air; a tubing section having a wall defining an enclosed passage, the passage arranged to convey a filament, the tubing section having an air inlet for providing heated air from the first heater into the passage; and a second heater arranged along at least part of the tubing section, in order to further heat filament within the passage; wherein the tubing section comprises: a filament inlet for receiving the filament to be dried; and a filament outlet for providing dried filament, wherein the filament inlet and the filament outlet are sealable around the filament such that the passage forms a sealed space, wherein the filament inlet and/or the filament outlet comprise: an opening into the passage; and a resiliently deformable sealing member closing the opening, the sealing member having an aperture to receive the filament, the edge of the aperture arranged to engage the filament to form a seal.
2 . The system of claim 1 , wherein the tubing section further has an air outlet for drawing air from the passage, the system further comprising a recycling system for providing air withdrawn at the air outlet to the first heater in a closed loop, wherein the recycling system includes an air dryer for extracting water from the air withdrawn at the air outlet before providing it to the first heater.
3 . The system of claim 2 , wherein the recycling system comprises a desiccant arranged to extract water from the air as it passed from the air outlet to the first heater.
4 . The system of claim 3 , wherein the system is arranged to monitor the saturation of the desiccant and comprises: a first humidity sensor arranged between the air outlet and the desiccant; a second humidity sensor arranged between the desiccant and the first heater; and a recycling control module arranged to: monitor a first humidity measured by the first humidity sensor, and a second humidity measured by the second humidity sensor; and provide a warning when a difference between the first humidity and the second humidity is below a threshold, indicating saturation of the desiccant.
5 . The system of claim 3 , wherein the desiccant is provided in a replaceable cartridge.
6 . The system of claim 3 , comprising an air cooler arranged to cool air drawn from the passage, prior to providing the air to the desiccant.
7 . The system of claim 6 , wherein the system comprises a conduit for carrying air from the air outlet to the desiccant, and wherein the air cooler comprises an uninsulated portion of the conduit extending at least part of the length of the conduit.
8 . The system of claim 2 , wherein the closed loop from the air outlet to the air inlet, including the recycling system and first heater, is formed in a sealed environment.
9 . The system of claim 1 , wherein the sealing member has a thinned region around the edge of the aperture.
10 . The system of claim 1 , wherein the system is for use with filament having a diameter greater than a first size, and wherein the aperture has a diameter, the diameter of the aperture being less than the first size.
11 . A system arranged to dry a filament used in additive manufacture, the system comprising: a first heater arranged to heat air; a tubing section having a wall defining an enclosed passage, the passage arranged to convey a filament, the tubing section having an air inlet for providing heated air from the first heater into the passage; a second heater arranged along at least part of the tubing section, in order to further heat filament within the passage; a drying control module arranged to control the first heater and second heater to control the amount of water removed from the filament; a first temperature sensor arranged to measure an air temperature at an output of the first heater; and a second temperature sensor arranged to measure an air temperature within the passage; wherein the drying control module controls the first heater and the second heater based on the air temperatures measured by the first and second temperature sensors, to control the amount of water removed from the filament.
12 . The system of claim 11 , comprising: humidity sensors arranged to measure humidity of air in the passage, wherein the drying control module controls the first heater and the second heater based on the humidity measured in the passage, to control the amount of water removed from the filament.
13 . The system of claim 11 , wherein the drying control module is further arranged to control the speed filament is conveyed through the passage and/or the flow rate of air through the passage, to control the amount of water removed from the filament.
14 . The system of claim 1 , wherein the second heater has a plurality of different heating zones arranged along the length of the passage; and wherein the second heater is arranged such that the different heating zones are independently controllable.
15 . The system of claim 1 , wherein the system is provided as a modular device to retrofit to existing 3D printers.
16 . The system of claim 1 , wherein the passage is arranged to convey the filament within a filament production line.
17 . The system of claim 11 , wherein the tubing section further has an air outlet for drawing air from the passage, the system further comprising a recycling system for providing air withdrawn at the air outlet to the first heater in a closed loop, wherein the recycling system includes an air dryer for extracting water from the air withdrawn at the air outlet before providing it to the first heater.
18 . An additive manufacturing machine comprising: a filament store; a deposition head including a liquefier for liquefying filament; a filament guide for feeding filament from the filament store to the liquefier; and a system for drying the filament, the system comprising: a first heater arranged to heat air; a tubing section having a wall defining an enclosed passage, the passage arranged to convey filament from the filament store, the tubing section having an air inlet for providing heated air from the first heater into the passage and forming at least part of the filament guide; and a second heater arranged along at least part of the tubing section, in order to further heat the filament within the passage; wherein the tubing section comprises: a filament inlet for receiving the filament to be dried; and a filament outlet for providing dried filament, wherein the filament inlet and filament outlet are sealable around the filament such that the passage forms a sealed space, wherein the filament inlet and/or the filament outlet comprise: an opening into the passage; and a resiliently deformable sealing member closing the opening, the sealing member having an aperture to receive the filament, the edge of the aperture arranged to engage the filament to form a seal.
19 . The additive manufacturing machine of claim 18 , wherein the tubing section of the system for drying the filament is immediately upstream of the liquefier.
20 . The additive manufacturing machine of claim 18 , wherein the filament store is a first filament store, the filament guide is a first filament guide for feeding filament from the first filament store to the liquefier, and the system for drying the filament is a first system for drying the filament fed from the first filament store, the additive manufacturing machine further comprising: a second filament store; a second filament guide for feeding filament from the second filament store to the liquefier; and a second system for drying the filament fed from the second filament store, the second system for drying filament comprising: a third heater arranged to heat air; a second tubing section having a wall defining a second enclosed passage, the second passage arranged to convey filament from the second filament store, the second tubing section having an air inlet for providing heated air from the third heater into the second passage and forming at least part of the second filament guide; and a fourth heater arranged along at least part of the second tubing section, in order to further heat the filament from the second filament store within the second passage.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This Application is a national stage application under 35 U.S.C. § 371 of PCT International Application Serial No. PCT/EP2021/050483, filed on Jan. 12, 2021 and entitled FILAMENT DRYING SYSTEM, which application claims priority to EP application Ser. No. 20/152,241.4 filed on Jan. 16, 2020. The disclosures of the prior applications are considered part of and are hereby incorporated by reference in their entirety in the disclosure of this application. The present invention relates to a system for drying a filament used in additive manufacture and to an additive manufacturing machine comprising the filament drying system. Extrusion based additive manufacturing (AM) processes, also known as extrusion 3D printing, are widely known. Typically, raw material is provided as a plastic filament wound on a spool or reel. During a manufacturing process (printing), the filament is unwound and fed to a deposition head. The deposition head includes a liquefier, which heats the material to a temperature at which it can flow. The heated material is then extruded through a nozzle in the desired pattern defined by a CAD model, often in a number of separate layers. The material fuses and re-solidifies as it cools, forming an object. Commonly used filaments are made from water sensitive (hygroscopic) materials, such as Acrylonitrile Butadiene Styrene (ABS), Nylon/Polyamides (PA), or Polycarbonate thermoplastic. When a filament that has absorbed water is extruded, the water within the material or on the surface of the material vaporizes and creates bubbles and voids in the filament, weakening adhesion between layers in the finished object and making the finished object more susceptible to warping. Water evaporating from the filament can also leave an undesirable surface finish. This is a result of bubbling, opaqueness or changes in the colour of the material, and also due to extra material continuing to ooze out of the extruder when it is not supposed to, resulting in stringing (pieces of extra material attached to the outside surface of the printed part). Additionally, the heated moisture/water can lead to chemical degradation of the materials since it can break apart polymer chains, weakening the material. Prolonged exposure to even moderately humid environment can cause saturation of a filament. Some filament materials may experience an increase in weight of 10% or more before reaching saturation point. AM machines (3D printers) rely on tight tolerances and extremely small layer heights and unexpected changes in the size of the filament can negatively impact the process. The presence of excess water in the filament can also change the viscosity of the material as it is extruded, so it does not flow as expected. If the filament has very high water content, it can lead to catastrophic failure of the process, causing the process to need to be repeated. Conversely, removing too much water also adversely affects printing process, and changes the properties of the filament. Therefore, the filament requires conditioning to have a moisture content within a desirable range. A number of methods are known for trying to prevent a hygroscopic filament absorbing water. One technique is to keep the filament in a humidity controlled environment; either a drybox or dry cabinet. However, this often fails to prevent absorption of water as the filament is exposed to the uncontrolled environment when it is loaded into/unloaded from the machine. Another technique is to dry the whole filament reel before use. This may be by heating, leaving the reel in the presence of a desiccant or in a vacuum or other methods. This requires good environmental control and long periods of time (between 4 and 24 hours), which are different for different kinds of material types. Furthermore, if reels are regularly swapped, the repeated cycles of drying and absorbing water, can degrade the material of the filament. Over-drying (removal of too much moisture) can also occur, degrading the material and/or printing. According to a first aspect of the invention there is provided a system arranged to dry a filament used in additive manufacture, the system comprising: a first heater arranged to heat air; a tubing section having a wall defining an enclosed passage, the passage arranged to convey a filament, the tubing section having an air inlet for providing heated air from the first heater into the passage; and a second heater arranged along at least part of the tubing section, in order to further heat filament within the passage. The drying system conditions the filament to have a moisture content within acceptable limits, by drying the filament to remove some of, but not necessarily all, the moisture. In a printer using the system, filament is fed through the passage containing heated air prior to extrusion. This means that only the portion of the filament that is about to be fed to the liquefier is heated. Therefore, the portion of