Nozzle for 3D printing

Abstract

Nozzle for 3D printing with an internal segmentation comprising upstream inlet segment (1) with a channel for filament entry and downstream outlet segment (9) with a channel for melt exit, which further comprises specific segments downstream of the inlet segment (1) and upstream of the outlet segment (9), namely a primary segment (4) with at least one channel, each of the channels having an approximate shape of a circular sector, a primary transition segment (5), a secondary segment (6) with at least one channel with a non-circular circumference, with the total circumference of the channels in cross section being greater than the total circumference of the channels of the primary segment (4) in cross section, a secondary transition segment (7).

Description

Nozzle for 3D printing

[0001] The invention relates to the field of additive manufacturing of three-dimensional objects by depositing a continuous bead of viscous material using filamentary material being melted and relates to apparatus for such additive manufacturing, specifically details thereof in the form of nozzles as means for applying layers.

[0002] One of the main obstacles to a wider industrial use of 3D printers based on the method of gradual layering of molten printing material, specifically plastic filament, and their employment in the production of components or products in large volumes has so far been the limited performance in terms of the amount of extruded material per unit of time. From this point of view, the bottleneck is primarily the nozzle – a component of the 3D printer print head which is heated by a heat source and the increased temperature causes the printing material to gradually soften and melt within the nozzle‘s internal space consisting of one or more channels, allowing the printing material to be subsequently deposited from the nozzle tip into the printing space, gradually creating a print. In order to achieve a sufficient printing resolution and level of detail in the structure of the 3D print, the opening in the nozzle tip must have a narrow diameter, typically tenths of a millimeter. However, this narrowing significantly limits the maximum flow rate of the molten material, which typically ranges between 10 mm3 / s and 20 mm3 / s for desktop 3D printers, thereby limiting the speed of the 3D printing process itself and extending the time required to create a 3D print. The limitation of the maximum flow rate is caused by an insufficient heating of the printing material during its passage through the nozzle body, and therefore by an inefficient liquefaction. The printing material thus retains a high viscosity value even when passing through the nozzle tip and, due to an internal friction, causes resistance, which is manifested by an exponential increase in the necessary extrusion force.

[0003] Solutions in the form of so-called high-flow nozzles are known from the prior art. These solutions target the cause of the above-mentioned technical problem, namely the excessive viscosity of the printing material at the moment of deposition, by increasing a circumference of the channel in cross section to achieve a larger inner surface of the nozzle, and therefore a larger contact area between the nozzle and the printing material passing through it. This results in a higher heat-transfer efficiency and a higher degree of liquefaction associated with a lower viscosity and a lower internal resistance during extrusion. Document WO2022243665A1 describes a nozzle equipped with one or more transverse partitions within its inner channel leading to an increase of the inner surface of the nozzle when compared with a variant with a simple channel of circular cross section. Furthermore, document EP3445568A1 describes high-flow nozzles with their inner surface enlarged by a presence of two or more inner channels of circular or oval cross section, these inner channels being parallel to the nozzle axis and not changing their cross-sectional shape along their entire length. A nozzle constructed according to this technical solution in a variant with three inner channels of circular cross section and a tip diameter of 0.4 mm achieves a melt flow rate of 16 mm3 / s at an applied extrusion force of 50 N and a flow rate of 48 mm3 / s at 175 N. However, such flow rates represent the limit of the technology based on the aforementioned solution due to a constructional limitation, as the nozzles are manufactured using a drilling method that effectively only allows a construction of straight internal channels with a cross-sectional shape that remains unchanged throughout the entire length, or at least the major part, of the multi-channel section of the nozzle. This results in a still limited efficiency of a heat transfer from the nozzle to the printing material, considering its temperature, and therefore mechanical properties, change gradually during passage through the nozzle, and as such, the material has different properties in different parts of the nozzle, which, however, is not reflected in the solutions known from the prior art.

[0004] Another type of high-flow nozzles known from the prior art, for example from document US2024253305A1, are modular nozzles, where an insert is placed into a wider, for instance conical, space inside the nozzle body, the insert having an inverse shape in relation to the shape of the space and being divided into multiple channels. A nozzle constructed according to this technical solution in a variant with a tip diameter of 0.4 mm achieves a melt flow rate of 20 mm3 / s at an applied extrusion force of 50 N and a flow rate of 40 mm3 / s at 175 N. The drawback of this construction is an inherent introduction of obstacles into the path of the flow of the molten printing material, as the division into multiple channels in such a nozzle requires a reduction in the cross-section area of the channel. The desired larger circumference of the channel in the cross section is therefore achieved by an undesirable change in the area of the channel in its cross section.

[0005] Another factor limiting the speed of 3D printing is the speed at which the nozzle itself heats up to the working temperature, i.e., a temperature sufficient to melt the printing material. This is problematic especially in the case of multi-color or multi-material printing, which requires frequent changes of the printing filament during the printing process, as is known, for example, from document US2023173749A1. The heat source heating the nozzle is typically a resistance element, with which it takes minutes to achieve an operating temperature. The heating can be significantly accelerated by using induction heating, as is known, for example, from document US11826960B2. Using this heating method, it is potentially possible to achieve heating of the nozzle and the printing material in its internal space to the operating temperature in seconds. However, such effective heating rate is achievable only when using nozzles whose internal space is shaped to allow an efficient heat transfer throughout the entire cross section and through all internal structures of the nozzle. Nozzles known from the prior art are not specifically adapted for induction heating, and although the rate of their heating by an induction heating is higher than the rate of heating by a conventional heating, the efficiency and speed is still significantly limited.

[0006] Goal of the present invention is to introduce a nozzle for 3D printing that enables high printing speeds by achieving high melt flow rates that exceed the technological limits of high-flow nozzles known from the prior art. This is accomplished by increasing the efficiency of heat transfer from the nozzle to the printing material by utilizing a structure of the internal space of the nozzle that changes gradually throughout the length of the nozzle, thus responding to different properties of the printing material in different parts of the nozzle, and by maintaining a high degree of uniformity of the channel area in the cross section while significantly increasing the channel circumference in the cross section. Furthermore, the nozzle structure is optimized for induction heating and rapid cooling, which further increases the speed of multi-color or multi-material printing or printing with dynamic changes in deposition temperature, while the nozzle is still being functional also with conventional heating methods.

[0007] The present invention is a nozzle for 3D printing with an internal single- or multi-channel segmentation comprising specific segments located between an inlet segment for filament entry and an outlet segment for melt exit, for example in the form of a nozzle tip, namely: (a) primary segment with at least one channel, each of the channels having an approximate shape of a circular sector, upstream of (b) primary transition segment, upstream of (c) secondary segment with at least one channel with a non-circular circumference, with the total circumference of the channels in cross section being greater than the total circumference of the channels of the primary segment in cross section, upstream of (d) secondary transition segment.

[0008] In the case of a multi-channel nozzle, it further comprises a separation segment located upstream of the primary segment with at least two equally spaced channels, each of which has an approximate shape of a circular sector, the separation segment comprising a bifurcation of the channels, and a connection segment with a confluence of the channels located downstream of the secondary segment with at least two equally spaced channels with a non-circular circumference and downstream of the secondary transition segment. The primary transition segment forms a fluent shape transition between the primary segment and the secondary segment, and the secondary transition segment forms a fluent shape transition between the secondary segment and any downstream segment directly following the secondary transition segment.

[0009] The individual segments defined above may be placed in the above-described arrangement directly one after another or, while maintaining the successive arrangement, may be complemented with other relevant segments, since only the successive arrangement of the primary segment, the primary transition segment, the secondary segment, and the secondary transition segment is fully necessary to achieve the technical effect of the invention.

[0010] The nozzle of this construction features a uniformity of the channel area in the cross section across all segments, while featuring a significant change in the channel circumference in the cross section, namely a significant increase in the circumference in the secondary segment. This is achieved by a pronounced change in the shape of the channels as they pass through the nozzle, transitioning from the channel with a circular circumference of the inlet segment to the arc-shaped or C-shaped channel of the secondary segment. As a result, the nozzle achieves significantly higher melt flow rates at a given extrusion force when compared with the prior art due to the smooth flow of the melt through the nozzle channels attributable to the uniformity of the internal volume per unit of length of a segment, and also achieves a high efficiency of heat transfer from the nozzle to the printing material attributable to the large inner surface, especially in the secondary segment. The internal segmentation of the nozzle and its complex shapes correspond to the viscosity gradient of the printing material, which is gradually heated during its path through the nozzle.

[0011] Advantageously, the separation segment is provided with separation ridges gradually nearing each other, the number of ridges corresponding to the number of channels, and as such, the ridges become shear structures assisting in the smooth movement of the filament while simultaneously dividing it into individual channels. Furthermore, the nozzle may advantageously include a stabilization segment directly following the inlet segment, the stabilization segment comprising at least two stabilization ridges. The presence of the stabilization segment ensures that the filament is prevented from rotating and at the same time works up the filament for an easier shaping within the downstream segments with a dynamic change in the shape of the channel or channels.

[0012] From a fabrication standpoint, the nozzle according to the present invention can be manufactured by 3D metal printing, rather than the usual way of manufacturing nozzles by drilling.Fig.1

[0013] depicts a longitudinal section of a two-channel nozzle according to the present invention in an advantageous variant according to Example 2.Fig.2

[0014] depicts cross sections of respective segments of a single-channel nozzle according to Example 1.Fig.3

[0015] depicts cross sections of respective segments of a two-channel nozzle in an advantageous variant according to Example 2.Fig.4

[0016] depicts a chart comparing efficiency of a two-channel nozzle according to the present invention (date line 3) with a three-channel high-flow nozzle with straight channels known from the prior art (date line 2) and with a four-channel high-flow nozzle with an insert known from the prior art (date line 1).Example 1

[0017] Example 1 describes a nozzle according to the present invention in a single-channel variant.

[0018] Nozzle for 3D printing is assembled in such a way that an inlet segment1with a channel with a circular circumference for a filament entry is followed by a primary segment4with one channel in the approximate shape of an almost closed circular sector, which is followed by a primary transition segment5, which at its upstream end corresponds to the shape of the downstream end of the primary segment4and at its downstream end corresponds to the shape of the upstream end of a directly following secondary segment6with one channel in the shape of an almost closed letter "C", which is directly followed by a secondary transition segment7, which at its upstream end corresponds to the shape of the downstream end of the secondary segment6and at its downstream end forms a channel with a circular circumference corresponding to the shape of a directly following outlet segment9.Example 2

[0019] Example 2 describes a nozzle according to the present invention in a two-channel variant in an advantageous version.

[0020] Nozzle for 3D printing is assembled in such a way that it contains segments placed directly one after another in the following successive arrangement described upstream to downstream: an inlet segment1with a channel with a circular circumference for a filament entry, a stabilization segment2with four stabilization ridges, a separation segment3with two opposed separation ridges gradually nearing each other for a bifurcation into two channels, with the two separation ridges connecting to two of the four stabilization ridges of the stabilization segment2, a primary segment4with two opposed equally spaced channels, with each of the channels having an approximate shape of a half-disk, a primary transition segment5, which at its upstream end corresponds to the shape of the downstream end of the primary segment4and at its downstream end corresponds to the shape of the upstream end of a secondary segment6, the secondary segment6measuring one-fifth of the total length of the nozzle with two opposed equally spaced channels, with each of the channels having an approximate shape of an arc or a semi-circle, a secondary transition segment7, which at its upstream end corresponds to the shape of the downstream end of the secondary segment6and at its downstream end corresponds to the shape of the upstream end of a connection segment8, the connection segment8with a confluence of channels, an outlet segment9with a channel with a circular circumference for a melt exit.

[0021] Nozzle for 3D printing is industrially applicable in a construction of print heads of 3D printers.

Claims

Nozzle for 3D printing with an internal segmentation comprising upstream inlet segment (1) with a channel for filament entry and downstream outlet segment (9) with a channel for melt exit,characterized in thatit further comprises the following segments downstream of the inlet segment (1) and upstream of the outlet segment (9):a primary segment (4) with at least one channel, each of the channels having an approximate shape of a circular sector, upstream ofa primary transition segment (5), upstream ofa secondary segment (6) with at least one channel with a non-circular circumference, with the total circumference of the channels in cross section being greater than the total circumference of the channels of the primary segment (4) in cross section, upstream ofa secondary transition segment (7).Nozzle for 3D printing according to claim 1,characterized in thatthe secondary segment (6) is solid along its central upstream-downstream axis.Nozzle for 3D printing according to claim 1,characterized in thatthe secondary segment (6) comprises a channel in the shape of an almost closed letter "C".Nozzle for 3D printing according to claim 1,characterized in thatthe secondary segment (6) comprises at least two equally spaced channels, with each of the channels having an approximate shape of an arc or a semi-circle.Nozzle for 3D printing according to claim 1,characterized in thatit comprises the primary segment (4) having at least two equally spaced channels, with each of the channels having an approximate shape of a circular sector, and further comprises a separation segment (3) upstream of the primary segment (4), the separation segment (3) having a bifurcation of channels, and further comprises the secondary segment (6) having at least two equally spaced channels with a non-circular circumference, and further comprises a connection segment (8) downstream of the secondary transition segment (7), the connection segment (8) having a confluence of channels.Nozzle for 3D printing according to claim 5,characterized in thatit comprises the separation segment (3) having separation ridges gradually nearing each other for a bifurcation into channels of the primary segment (4), with the number of separation ridges corresponding to the number of channels of the primary segment (4).Nozzle for 3D printing according to claim 1,characterized in thatthe primary transition segment (5) forms a fluent shape transition between the primary segment (4) and the secondary segment (6), and the secondary transition segment (7) forms a fluent shape transition between the secondary segment (6) and any downstream segment directly following the secondary transition segment (7).Nozzle for 3D printing according to claim 1,characterized in thatit comprises a stabilization segment (2) downstream of the inlet segment (1), the stabilization segment (2) having at least two stabilization ridges for working up the filament for an easier shaping and for preventing the filament from rotating.

Images