Print cooling system for 3D printers

Abstract

Print cooling system for 3D printers comprising source of cooling air, for example in the form of fan, located away from print head, for example on frame of 3D printer, and connected via cooling air duct to channel equipped with flap (8) for redirecting or dividing cooling air flow between at least one cooling nozzle (10) directed to extruder print nozzle for cooling deposited material and exhaust (7) directed into free space, while the channel fitted with flap (8) is located on print head and motor (6) is connected to flap (8) via rod to facilitate movement of flap (8). Additionally, an extruder cooler box for cooling the extruder cooler fins can be placed between the cooling air duct and channel fitted with flap (8).

Description

Print cooling system for 3D printers

[0001] The invention relates to the field of additive manufacturing of three-dimensional objects by applying a continuous drop of viscous material in the form of molten fibrous material and relates to equipment for such additive manufacturing, specifically to components for applying layers such as a print head and a print cooling system, and further relates to additive manufacturing production processes using these devices.

[0002] Cooling the printout is one of the key criteria for creating a quality printout in 3D printers based on the technique of successive layering of molten plastic filament. One reason being that printing must always be done on an already hardened layer of extruded material, as otherwise there is a risk of deformation of the print by separation of the last unhardened layer of extruded material from the previous layer. Furthermore, when printing overhangs or bridges, it is important to cool down the plastic as soon as possible and to strengthen it in place to prevent sagging of such a structure. The concept of a 3D printer using active print cooling is known, for example, from document US2018056608A1, in which, however, neither the design or method of the cooling nor the source of cooling gas are not specified, or from document EP4275868A1.

[0003] For the purpose of cooling, most 3D printers are equipped with fans on their print heads. This approach significantly speeds up cooling of the print by blowing ambient air onto the deposited material. Such a solution is known, for example, from the document EP3323594A1, where the print head is equipped with a fan blowing air into the inner space of the extruder cover where the gas is further guided through tubes and directed to the outer surroundings of the extruder print nozzle. However, in this solution, controlling the rate of air flow to the printout is only possible by changing the fan speed. Since it takes a significantly long time to spin the fan from a complete standstill to the desired speed value, which would disproportionately increase the overall printing time and significantly reduce the dynamics of the print cooling system, the fan is kept running at set minimal speed to reduce the total printing time. However, with some deposited plastic materials, such continuous, albeit minimal, cooling can negatively impact quality of the print and cause deformation or separation of layers. Another disadvantage of such a solution is the presence of a fan directly on the print head, where vibrations caused by the rotating fan negatively affect the accuracy of material deposition resulting in a limited print resolution. Placing the fan on the print head also has a major impact on the lifespan of the print head components, as well as the fan itself, especially at high speeds. Both the fan being a source of substantial vibrations and the influence of vibrations on the service life of the fan represent a technical problem, as demonstrated for example by document US8043049B2.

[0004] Document US2022203613A1 discloses a solution in form of a system supplying cooling air to the vicinity of the printhead extruder, with the source of cooling air being an external compressor unit leading air through a reduction valve to a heat exchanger enabling both cooling and heating of the flowing air, which is then further led to a three-way valve controlling the air flow to the extruder by variably distributing the current between a tube ending with cooling nozzles at the extruder space and an exhaust directed into a free space within the 3D printer. Considering the intrinsic bulkiness of three-way valves as integrated components, the valve itself cannot be located on the print head in close proximity to the extruder. Therefore, there needs to be a lengthy air duct placed between the valve and the extruder, which, due to the compressibility of air as a medium, inevitably causes a delay between the change of valve position and the change of coolant flow in the extruder space. Due to this delay, which is inherent to the very concept of this solution, the solution described in the cited document does not allow printing with a very high resolution of temperature map of deposition.

[0005] Goal of the present invention is to introduce a print cooling solution for 3D printers that eliminates the identified shortcomings of the prior art by allowing the value of the cooling air flow to be changed within the range from zero to the maximum flow in such a short time interval that the cooling of the layer being deposited does not unnecessarily extend the duration of the print job. Furthermore, it enables continuous layer deposition together with a different degree of cooling of selected sections represented by a temperature map of deposition in a very high resolution, even at high print speeds. Last but not least, it is characterized by a simple structure that does not create vibrations that would negatively affect the accuracy of deposition. Together, these advantages lead to high quality and mechanical stability of the printed object.

[0006] The present invention is a print cooling system for 3D printers eliminating the above-identified shortcomings of the prior art by comprising a source of cooling air located on the body of the 3D printer away from the print head, a flexible air duct leading from the source of cooling air to a flap located in close proximity to the extruder of the print head with the flap being constructed in such a way that it redirects or distributes the flow of supplied cooling air between at least one cooling nozzle directed to the extruder print nozzle target point, i.e., into the print deposition area, and an exhaust directed into a free space within the 3D printer.

[0007] An element in the form of a flap redirecting or distributing the flow of supplied cooling air between the cooling nozzles directed to the target point of the print nozzle of the print head extruder, where it cools the deposited material, and the exhaust directed into the free space within the 3D printer allows the source of cooling air, which is, for example, a fan, to continuously supply a sufficient amount of cooling of air so that said amount is available for redirection to cool the deposited material in any given moment of the ongoing 3D printing. Due to the fan being placed away from the print head, the 3D printer can be equipped with a larger and more powerful fan or blower or turbine that cannot be placed on the print head for dimensional reasons. Thus, it is possible to achieve a much greater air flow than with a fan located on the print head, i.e., a standard solution known from prior art. When utilizing lower than the highest operating flow rate or zero flow rate to cool the deposited material, the amount of cooling air that is not used for cooling is released into the free space outside of the deposition area.

[0008] In contrast to a theoretical solution where the flow of supplied cooling air is restricted by, for example, a throttle valve, the system according to the present invention does not experience increased pressure in the part of the system supplying the cooling air. This achieves an immediate availability of cooling air at any moment of deposition. If there was an increase in pressure, this would have to be compensated by, for example, reducing the power of the cooling air source. In that case, any subsequently demanded increase in power back to the highest operating flow would require too much time, specifically in the order of seconds. Additionally, changes in pressure in the part of the system supplying the cooling air would require presence of a feedback mechanism including a pressure gauge that would adjust setting of the element dispensing the cooling air into the deposition area based on the current system pressure. This would represent a significantly complicated solution. The system according to the present invention is characterized by a constant pressure in the part of the system supplying the cooling air and a constant flow of supplied cooling air, which makes it structurally simpler and more efficient at the same time.

[0009] The continuous flow of supplied cooling air in the system according to the present invention further enables this air to be used to cool other parts of the printer, especially the cooler of the extruder (so-called a heatsink), by leading the flow of supplied cooling air through this cooler. According to prior art, heat removal from the extruder cooler is normally managed by a second separate fan located directly on the print head, which is a source of significant print head vibrations limiting the capabilities of printing with high spatial resolution. The system according to the present invention eliminates the necessity of presence of this additional fan in or on the structure of the print head, thus achieving stability as well as reduction in the weight of the print head.

[0010] To achieve the technical effect of the present invention, it is necessary that the redirection or distribution of the flow of supplied cooling air takes place in close proximity to the deposition area. The component redirecting or distributing the flow of supplied cooling air must therefore meet the installation requirements defined by the very limited space around the extruder. For this reason, the solution known from the prior art in the form of a three-way valve is not applicable. The construction according to the present invention therefore comprises a flap located in close proximity to the deposition area as a component redirecting or dividing the flow of supplied cooling air, thereby minimizing the distance between this component and the deposition area, which results in virtual elimination of the delay between the change of flap position and the resulting change in flow of supplied cooling air to the deposition area. To achieve the technical effect of the present invention, it is also necessary to ensure a rapid change in the flap position to redirect or distribute the flow of supplied cooling air. For this purpose, the flap is controlled by a stepper motor or a servomotor reaching a high angular speed controlled by the computing unit of the 3D printer. Said computing unit contains a firmware and its program is configured before each printing to control the flap in relation to the print job and its corresponding temperature map of deposition.

[0011] The above-described system according to the present invention is able to achieve very short time frames necessary to change the speed of the flow of supplied cooling air into the deposition area to cool the deposited material. Specifically, such time frames are in the order of units to lower tens of milliseconds. This enables a different degree of cooling of selected sections of the print within one printing layer with a very high resolution of the temperature map of deposition. Even in the extreme case of the highest practically applicable speed of the print head in the print plane, which is 0.6 m / s, and with a change in the intensity of cooling of the deposited material from 0% to 100%, which is achieved by redirecting the cooling air in 40 ms, the resolution of the temperature map of deposition exhibited by the system is 24 mm. However, in typical cases, the required immediate change in the intensity of cooling of the deposited material in a significantly narrower percentage range and at a significantly lower speed of the print head in the print plane. In such cases, the system achieves redistribution of the flow of supplied cooling air in units of milliseconds.

[0012] Beneficially, the system according to the present invention can be equipped with a second flap placed in front of the cooler of the extruder, i.e., upstream in relation to the flow of supplied cooling air. Such secondary flap then redirects or distributes the flow of supplied cooling air between a pathway leading through the cooler fins for their cooling and a bypass. When bypassed, the cooling air is not led through the cooler fins, but goes directly to the main flap, i.e., to the flap redirecting or distributing the flow of supplied cooling air between the cooling nozzles directed to the target point of the print nozzle of the print head extruder, where it cools the deposited material, and the exhaust directed into the free space within the 3D printer. This secondary flap contributes to the high print quality by limiting the excessive cooling of the extruder cooler even at high air flows, while not limiting the operation of the main flap that provides cooling to the deposited material, since the secondary flap does not restrict the overall flow of supplied cooling air that is being led to the main flap in any of secondary flap’s positions, as all the cooling air is always directed towards the main flap. The secondary flap is operated by its own stepper motor or servomotor controlled by the computing unit of the 3D printer. Said computing unit contains a firmware and its program sets the position of the secondary flap based on the current temperature of the extruder cooler.Fig.1

[0013] depicts a diagram of a 3D printer equipped with a system according to the present invention with a flap located in the print head.Fig.2

[0014] depicts an axonometric view of a print head of a 3D printer equipped with a system according to the present invention.Fig.3

[0015] depicts an axonometric view of a channel fitted with a flap positioned to redirect cooling air to an exhaust directed into a free space within the 3D printer.Fig.4

[0016] depicts an axonometric view of a channel fitted with a flap positioned to redirect cooling air to cooling nozzles directed to a target point of a print nozzle of a print head extruder.Fig.5

[0017] depicts an axonometric view of a channel fitted with a flap positioned to distribute cooling air between the cooling nozzles and the exhaust.Fig.6

[0018] depicts a diagram of a 3D printer equipped with a system according to the present invention in a beneficial version with two flaps.Fig.7

[0019] depicts an axonometric view of a print head of a 3D printer equipped with a system according to the present invention with a secondary flap placed in front of an extruder cooler, i.e., upstream in relation to a flow of supplied cooling air.Example 1

[0020] Example 1 describes a print cooling system for 3D printers according to the invention equipped with a main flap located in the print head.

[0021] Source1of cooling air in the form of a fan is located on a frame2of a 3D printer away from a print head4. One end of a flexible hose of a cooling air duct3is connected to the source1of the cooling air, while the other end of the flexible hose of the cooling air duct3is connected to a housing51of a cooler5of an extruder9so that the cooling air driven by the source1of cooling air is guided through fins of the cooler5of the extruder9to cool the fins. The housing51of the cooler5contains in its lower part an outlet for the cooling air in the form of an opening and the opening is followed by a channel equipped with a flap8for redirecting or dividing a flow of supplied cooling air, which is exiting the housing51of the cooler5, between cooling nozzles10directed to a target point of a print nozzle of the extruder9, where it cools deposited material11, and an exhaust7directed into a free space within the 3D printer. The flap8is further connected via a rod61to a stepper motor6to facilitate movement of the flap8and set selected position of the flap8at any given moment of printing.Example 2

[0022] Example 2 describes a print cooling system for 3D printers according to the invention in a beneficial version equipped with a main flap located in the print head and a secondary flap.

[0023] Source1of cooling air in the form of a blower is located on a frame2of a 3D printer away from a print head4. One end of a flexible hose of a cooling air duct3is connected to the source1of the cooling air, while the other end of the flexible hose of the cooling air duct3is connected to a housing51of a cooler5of an extruder9equipped with a bypass52, where an inlet channel leading to the housing51is equipped with a secondary flap80for redirecting or dividing a flow of supplied cooling air entering the housing51of the cooler5so that the cooling air supplied by the source1of cooling air is guided either through fins of the cooler5of the extruder9to cool the fins or through the bypass52directly to a flap8, avoiding the cooler5. The secondary flap80is further connected via a rod to a stepper motor60to facilitate movement of the secondary flap80and set selected position of the secondary flap80at any given moment of printing. The housing51of the cooler5contains in its lower part an outlet for the cooling air in the form of an opening, through which the cooling air exits either the cooler5space or the bypass52, and the opening is followed by a channel equipped with the flap8for redirecting or dividing the flow of supplied cooling air, which is exiting the housing51of the cooler5, between cooling nozzles10directed to a target point of a print nozzle of the extruder9, where it cools deposited material11, and an exhaust7directed into a free space within the 3D printer. The flap8is further connected via a rod61to a stepper motor6to facilitate movement of the flap8and set selected position of the flap8at any given moment of printing.

[0024] 3D printed material with a variably flexible internal structure is industrially applicable in the manufacturing of flexible materials with controlled stiffness, for example in the field of production of sports equipment.

Claims

Print cooling system for 3D printers,characterized in thatthe source (1) of cooling air is located away from a print head (4) and is connected via a cooling air duct (3) to a channel equipped with a flap (8) for redirecting or dividing the flow of supplied cooling air between at least one cooling nozzle (10) directed to a print deposition area of an extruder (9) for cooling of deposited material (11) and an exhaust (7) directed into a free space, while the channel equipped with the flap (8) is located on the print head (4), and a motor (6) is connected to the flap (8) to facilitate movement of the flap (8).Print cooling system according to claim 1,characterized in thatbetween the cooling air duct (3) and the channel equipped with the flap (8), there is a housing (51) of the cooler (5) of the extruder (9) for cooling fins of the cooler (5) of the extruder (9).Print cooling system according to claim 2,characterized in thatan inlet channel to the housing (51) is fitted with a secondary flap (80) for redirecting or dividing the flow of supplied cooling air between the cooler (5) of the extruder (9) and the bypass (52), and the secondary flap (80) is connected to a motor (60) to facilitate movement of the secondary flap (80).Print cooling system according to claim 1,characterized in thatthe source (1) of cooling air is a fan.Print cooling system according to claim 1,characterized in thatthe source (1) of cooling air is a blower.Print cooling system according to claim 1,characterized in thatthe source (1) of cooling air is located on a frame (2) of the 3D printer.

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