Heating unit for composite printing of articles

Abstract

A heating unit (100) for a printhead is disclosed, the heating unit comprising at least two guide tubes (132, 134) comprising a first guide tube (132) adapted to guide fiber filaments to an extruder (140) of the heating unit and a second guide tube (134) adapted to guide polymer filaments to the extruder, the heating unit further comprises a heating element adapted to melt the polymer filaments and a horizontal guide channel (125) adapted to guide the molten polymer from the second guide tube to the extruder, the heating unit further comprising a printing nozzle (123) connected to the extruder and adapted to print the composite part by outputting the composite material outside the heating unit.

Description

Technical Field

[0001] The present disclosure relates to the field of additive technology and can be used to manufacture parts and structures made of composite materials reinforced with continuous fibers. Background Art

[0002] 3D printing devices using composite fibers are known in the art, such as print heads intended for manufacturing parts or structures made of composite materials.

[0003] For example, there are many 3D printer models that include specially designed print heads for printing with composite materials. Composite materials or "composites" include components with different properties and distinct boundaries between the components. Composite materials can be filled with particles, short fibers, or long fibers (which can be cyclic or continuous fibers) to reinforce the composite material. In particular, composites with long or continuous fibers provide structural materials with the advantages of high stiffness and high strength compared to composites without long or continuous fibers.

[0004] For composite printing of products and forming structural polymer composites, such fibers are introduced into a matrix, which is usually a solid thermoplastic material. The matrix is ​​a material that bonds the fibers together or fills them with short fibers. Typically, the matrix has much lower mechanical properties than the fibers. The composite fibers are fed into the extruder by a feed device, heated to a temperature exceeding the melting temperature of the matrix material of the composite fibers, laid on the print table through a print nozzle and fused to the print table, which enables the gradual formation of composite products. Heating is usually provided by a heating unit attached to or included in the print head. Here, the extruder is also referred to as an extruder fiber channel.

[0005] For example, international patent application WO 2018 / 190750A1 discloses a print head, which in particular includes a mechanism for supplying plastic filaments or more specifically polymer filaments, another mechanism for supplying fibers, a supply tube for the polymer filaments, one or more supply tubes for the fibers, a heating unit, a plurality of input channels, and a printing nozzle having an output channel for obtaining a reinforced plastic polymer after the filaments and fibers have passed through the heating unit.

[0006] As is known in the art, Figure 1A hot end unit 1 is shown, a heating block 10 having input channels, such as a fiber input 12 for receiving fiber filaments 13 and intended to guide the fiber filaments to corresponding supply channels 40, which are inside the heating unit 10, and a polymer input 14 for receiving polymer filaments 11 and intended to guide the polymer filaments to corresponding supply channels 20. The polymer filaments 11, such as thermoplastic polymers, are melted in the hot zone of the heating unit 10. The molten thermoplastic polymer is then supplied during the printing process to cover the composite fibers, thereby ensuring the connection between the different fibers within one or different layers of the article or component to be printed. The plastic or polymer then comes out of the printing nozzle 60 to build the printed article or component. It should be emphasized that the plastic filaments are usually much thicker than the composite fibers.

[0007] A disadvantage of the known device is that the fiber supply channel guiding the fiber to the print nozzle must meet strict dimensional requirements and be long and thin enough to finely guide the filaments, in particular fiber filaments, from the input on the top side of the print head to the output print nozzle on the bottom side of the heating unit.

[0008] Typically, a print head comprises a component known as a "hot end", which is the part of the print head responsible for melting and extruding a filament, such as a polymer filament in a 3D printer. The hot end typically comprises a heating block, a nozzle and a thermistor, all of which work together to melt the filament and control the temperature of the melted filament so as to deposit the filament at a desired location under the print head in a very precise manner, thereby creating a three-dimensional object. A disadvantage of known heating units and / or known hot ends is that the fibers and polymer filaments guided through the heating unit can become sticky, adhere and / or stick to the inner walls of the component. This in turn can lead to burning of the filament and / or the inner walls, further accumulation of coatings, such as residual carbonized coatings, which can eventually clog the feed channels in the heating unit. This can cause clogging of the entire print head, leading to failure of the printing process.

[0009] Thus, despite the many advances that have been made in the field of composite printing, there remains a need for a print head that is protected from undesirable clogging by fibers directed therethrough.

[0010] The solution to this problem is usually to enlarge the print head size or to enlarge the heating unit attached to the print head or other components as part thereof. However, this solution is not satisfactory for many applications because it makes the heating unit too large and bulky, for example, the provided printing device takes up too much space or is incompatible with the heating unit. In addition, in this case, the distance between the hot zone inside the heating unit and the printing nozzle from which the printed material is output may also be too large to ensure proper melting of the polymer, thereby reducing the quality of the printing process.

[0011] Rather than further reducing the size of the print head elements, it would be advantageous to provide other solutions to avoid fibers or polymer filaments from adhering to or clogging the heating cells by reducing the possible friction area of ​​the materials in the print head. Solutions have been sought to avoid plastics, polymers and other materials from burning and adhering to the walls within the print head and heating cells, but have not been successful in some applications.

[0012] Therefore, there is a need to keep print heads smaller while making the printing process more stable and economical, especially for producing thermoplastic composite articles with minimal waste. Summary of the invention

[0013] The object of the present disclosure is to solve these shortcomings, defects and problems by providing in a first aspect a heating unit for a print head, the heating unit comprising: - at least two guide tubes, each guide tube being suitable for being connected to an extruder, a first guide tube of the at least two guide tubes being suitable for guiding fiber filaments from a first inlet of the first guide tube to the extruder, a second guide tube of the at least two guide tubes being suitable for guiding polymer filaments from a second inlet of the second guide tube to the extruder, - a heating element being suitable for melting the polymer filaments guided in the second guide tube to the extruder, - a horizontal guide channel being connected to the extruder and being located below the first guide tube and the second guide tube, the horizontal guide channel being suitable for guiding the molten polymer from the second guide tube to the extruder, - an extruder being suitable for forming a composite material by covering the fiber filaments guided in the first guide tube to the extruder with the molten polymer filaments, and - a printing nozzle being connected to the extruder and being suitable for printing a composite part by outputting the composite material to the outside of the heating unit.

[0014] In one embodiment, each guide tube is connected to an extruder.

[0015] This can significantly reduce the amount of leakage, clogging and / or burning of materials used in print heads intended for printing components and elements, in particular for composite printing. In particular, such leakage, clogging and / or burning of this material can be avoided, in particular in the case where this material is a plastic material such as a thermoplastic polymer, which melts in a problematic manner when heated in previously known print heads. This further aims to prevent leakage, clogging and burning of the heating unit of the print head.

[0016] In a preferred embodiment, the fiber filaments are selected from carbon fiber filaments, glass fiber filaments or Kevlar fiber filaments.

[0017] This enables the manufacture of parts or elements with different properties depending on the type of fiber filament, taking into account that during the printing process reinforced plastics and composites are obtained to produce parts with a high strength-to-weight ratio, temperature and chemical resistance.

[0018] Specifically, carbon fiber filaments are strong and rigid filaments that can enhance the structural strength of printed parts that are lightweight and strong. Glass fiber filaments have properties similar to carbon fiber elements, but the resulting parts tend to be less brittle than those made with carbon fiber filaments. Kevlar fiber filaments enable the manufacture of parts with high strength and heat resistance, and are further able to resist cutting and abrasion. Carbon fiber reinforced plastics can also be used because they combine the strength of carbon fiber with the flexibility of a plastic matrix (such as nylon or polyester fibers) to produce lightweight and strong parts.

[0019] In a preferred embodiment, the polymer filaments are thermoplastic polymer filaments selected from the group consisting of polyetheretherketone, polyetherketoneketone, polyetherimide, polysulfone, polyphenylsulfone and polyethersulfone.

[0020] This provides a heating unit for an efficient and economical print head to produce a material with advantages far superior to known heating units. Advantageously, polyetherketoneketone (PEKK) allows the ability to print parts at high temperatures and in high temperature environments without significant loss of mechanical properties. In addition, PEKK has a high strength-to-weight ratio and excellent chemical resistance, which makes it very suitable for use in harsh environments or in the aerospace and automotive industries. Polyetherimide (PEI) provides similar advantages and is particularly suitable for electronic components. Polysulfone (PSU) provides similar advantages to PEKK and PEI, and also has high transparency and dimensional stability, which makes it a good candidate for optical applications. Polyphenylsulfone (PPSU) PPSU has good dimensional stability, excellent fatigue resistance and good hydrolysis resistance, which makes it highly reliable for high-performance components in harsh environments. Advantageously, polyethersulfone-acrylonitrile (PES or PESAN) has high rigidity, excellent dimensional stability and good flame retardant properties, which makes it an excellent choice for structural components and electrical components.

[0021] In other embodiments, the polymer filaments are selected from acrylonitrile butadiene styrene or thermoplastic polyurethane, a biodegradable thermoplastic polymer such as polylactic acid, a copolyester such as polyethylene terephthalate glycol, and nylon.

[0022] Advantageously, acrylonitrile butadiene styrene, or ABS, has a high melting point and good strength, making it suitable for a wide range of applications. Polylactic acid, or PLA, is biodegradable and easy to work with. Polyethylene terephthalate glycol, or PETG, has high strength and durability, and is also resistant to impact, extreme temperatures, and UV rays, making it a versatile plastic for a variety of applications. Nylon is strong, flexible, durable, and can be used in printing processes at low temperatures.

[0023] In a preferred embodiment, the heating unit further comprises a heat sink positioned around a portion of the length of a guide tube adapted to guide the polymer filaments and axially aligned with the vertical axis of the guide tube.

[0024] In a preferred embodiment, the heating unit also includes a heating block, and each of the at least two guide tubes is fixed on a first upper side of the heating block, the heating block also includes an extruder and a printing nozzle, the printing nozzle is positioned in the heating block so that the composite material is output outward from the heating block and from the lower side of the heating block, the lower side is opposite to the upper side, and the heating block also includes a heating element.

[0025] In a preferred embodiment, the heating unit further comprises a column attached to the heating block, and the first guide tube is located between the column and the second guide tube.

[0026] In one embodiment, the column is vertically attached to the heating block.

[0027] In one embodiment, with the column vertically attached to the heating block, the first guide tube, the column, and the second guide tube are vertically aligned with each other.

[0028] In another embodiment, the column can be positioned along an axis that forms an angle with the first guide tube and the second guide tube so that the column is attached to the heating block horizontally or obliquely.

[0029] In a preferred embodiment, the heating block comprises a first area, called thermistor area, adapted to accommodate at least one thermal sensor and / or thermistor, and a second area, called heater area, adapted to accommodate at least one heating element.

[0030] In a preferred embodiment, the heater zone comprises at least one receiving portion adapted to receive a heating element.

[0031] In a preferred embodiment, the horizontal guide channel comprises a hollow space formed in a heating block of the heating unit, the hollow space being located below at least two guide tubes attached to the heating block and being adapted to accommodate a gasket of corresponding size and shape.

[0032] In a preferred embodiment, the heating block comprises an input sleeve located below the guide tube and adapted to guide the fiber filaments, the input sleeve having an opening whose diameter is adjustable to control the flow of the fiber filaments.

[0033] In a preferred embodiment, the heating unit further comprises an empty space defining an air gap between the second guide tube and the input cannula.

[0034] In a preferred embodiment, the heating unit also includes a gasket suitable for being assembled in the horizontal guide channel, the gasket including a solid part and a hollow part located inside the solid part, the solid part is made of a material with high thermal conductivity, and the hollow part includes a gradually narrowing cut, the width of the cut is large enough to guide the molten polymer filament toward the printing nozzle.

[0035] In another aspect, a print head is proposed, comprising: - a main support, - two heating units attached to the main support, one of the two heating units being a heating unit according to any one of the preceding claims, - a cutting mechanism attached to the main support for cutting fiber filaments, and - a switching mechanism attached to the main support for controlling the height of one of the two heating units or controlling the height of both heating units.

[0036] In a preferred embodiment, the cutting mechanism comprises one or more rotatable cylindrical cutters, each rotatable cylindrical cutter comprising a radial bore and at least one cylindrical sleeve fixed to the radial bore.

[0037] In a preferred embodiment, the switching mechanism comprises a lever configured to control the vertical position of the print nozzles of one of the two heating units or to control the vertical position of the print nozzles of both heating units. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Additional features, details and advantages will be seen in the following detailed description and in the accompanying drawings, in which:

[0039] Figure 1 is a cross-sectional view of a heating unit known in the art,

[0040] Figure 2 is a cross-sectional view of a heating unit according to one embodiment,

[0041] Figure 3A , Figure 3B and Figure 3C is a schematic diagram of a heating unit according to one embodiment,

[0042] Figure 4 is a schematic diagram of a gasket for a heating unit according to one embodiment, and

[0043] Figure 5 is a diagram of a print head including one or more heating units according to one embodiment.

[0044] Unless otherwise noted, common or similar features across several figures have the same reference numerals and refer to the same elements, so that for the sake of simplicity these common features are generally not described again. DETAILED DESCRIPTION

[0045] The present invention will be further explained with reference to the following figures and embodiments.

[0046] Figure 1 What has been described previously are examples of heating units of print heads known in the art.

[0047] Reference now Figure 2 , Figure 3A , Figure 3B and Figure 3C , shows a heating unit for a print head according to one embodiment.

[0048] Specifically, in one embodiment, the heating unit 100 is shown to include a fiber tube input 112 and a polymer tube input 114 .

[0049] The heating unit also includes a heating block 150 to which the elements described before and after are attached or included.

[0050] The fiber tube input 112 can be connected to a fiber supply mechanism located outside the heating block 150, while the polymer tube input can be connected to a polymer supply mechanism also outside the heating block 150. The fiber tube input 112 serves as an inlet for fiber filaments, i.e., for guiding the fiber filaments downward into the fiber guide tube 132, while the polymer tube input 114 serves as an inlet for polymer filaments, i.e., for guiding the polymer filaments into the polymer guide tube 134.

[0051] In one embodiment, a heating element is disposed inside the heating unit 100 to heat the interior of the heating unit 100 and some or all of its elements. Examples of heating elements include resistive heating elements, infrared heating elements, cartridge heating elements, positive temperature coefficient elements, mica heating elements, and ceramic heating elements.

[0052] In one embodiment, the bottom of the heating unit 100 or the bottom of the heating block 150 of the heating unit 100 comprises a first area 170 referred to as thermistor area, which is adapted to accommodate at least one thermal sensor and / or thermistor.

[0053] In one embodiment, the bottom of the heating unit 100 or the bottom of the heating block 150 comprises a second area 172, referred to as the heater area, which forms a lodge suitable for accommodating the heating element. Advantageously, the elements 121, 122 and 123 described below are positioned so that they reach the same temperature when heated by the heating element.

[0054] In one embodiment, at least one thermal sensor and / or thermistor is disposed inside the heating unit 100 to measure the temperature of internal components of the heating unit 100 .

[0055] Advantageously, the thermistor may be configured to measure the temperature of the polymer guide tube and the temperature at different points of the polymer guide tube.

[0056] In one embodiment, the heat sink 116 is disposed around the polymer guide tube 134 along a portion of its length and is axially aligned with the vertical axis of the polymer guide tube. The heat sink 116 may include one or more additional elements selected from a heater, a dissipation block, a thermistor, and a thermocouple. The heat sink may further be attached to a heating block 150.

[0057] Advantageously, the heat sink 116 is able to dissipate excess heat from the heating unit 100 and reduce the temperature of the cold zone located above the heating unit as much as possible.

[0058] In one embodiment, the heat sink 116 may include various dissipative elements, such as a heat sink or any type of passive component that can dissipate heat by conduction. Advantageously, the dissipative elements may also be configured to minimize the temperature of any cold areas located above the heating unit.

[0059] Advantageously, such a dissipative element or passive component is made of a metal such as aluminum and has a large surface area to help dissipate heat quickly. The dissipative element may include a thermoelectric cooler for actively cooling elements inside the heating unit or inside the heating block. The dissipative element may also be a thermal paste or thermal grease, thereby providing a material for filling gaps or spaces in the print head, in the heating unit or in the heating block. This further improves the thermal conductivity between the print head and the cooling element, which helps to dissipate heat more effectively.

[0060] Advantageously, polymer filaments and fiber filaments are pushed inside the hot end using their own stiffness. After these filaments are heated inside the heating unit 100, they become soft and lose their stiffness, thereby avoiding the need to push the filaments over long distances while melting. In other words, a print head including a heating unit as described herein includes an effective thermal circuit breaker in which the maximum temperature gradient is possible.

[0061] This makes it possible to provide a uniform temperature increase along the heat sink.

[0062] In one embodiment, the print head includes a single heating unit 100 .

[0063] For example, the heating unit 100 may be a cylindrical heater adapted to be inserted into corresponding holes between the column 110 and the fiber guide tube 132 .

[0064] In other embodiments, the heating unit 100 or a print head including the heating unit includes at least one other heater element that is configured to be heated to a temperature that exceeds the melting temperature of the fiber filaments or the melting temperature of the polymer filaments that will be fed into the fiber tube input 112 or the polymer tube input 114.

[0065] In particular, the heater element may be heated to a temperature that exceeds the melting temperature of the polymer or thermoplastic filament.

[0066] If reinforcing fibers impregnated with a thermosetting binder and cured are used as the polymer filaments, the heater element can be heated to a temperature exceeding its glass transition temperature.

[0067] Optionally, the temperature can be kept constant by a feedback control system using a temperature sensor.

[0068] In one embodiment, the heat sink 116, the heating element, the at least one thermal sensor and / or thermistor are made of aluminum, copper, an aluminum alloy, a copper alloy or any other element with high thermal conductivity, which is preferably higher than 100 W / m·K, even more preferably higher than 200 W / m·K.

[0069] In one embodiment, the heater elements are adapted to melt the polymer filament melt inside the corresponding hot zone of the heating unit 100, and the molten polymer is then mechanically pushed onto or into the fiber filaments passing through the fiber guide tube 132 via the guide channel 125. The molten polymer is preferably in the form of a fluid plastic.

[0070] In a preferred embodiment, the guide channel 125 is horizontal. Preferably, the guide channel 125 extends below the two guide tubes 132 and 134 so that the outlet of each guide tube outputs the filament into the guide channel 125, which is preferably horizontal and located below the fiber guide tube 132 and the polymer guide tube 134.

[0071] In one embodiment, the guide channel 125 is a cutout in the heating block 150. The cutout in the guide channel 125 may also be filled with a gasket or any element that partially fills the guide channel 125.

[0072] In one embodiment, the fibers covered with molten polymer or plastic are then drawn out of the printing nozzle 123 of the heating unit 100 so that the nozzle can be deposited for printing parts of the composite material.

[0073] In one embodiment, the heating unit 100 has two input channels, which allows printing with fibers that are not fused to each other and can be combined, for example, by covering each other. Covering the fibers with thermoplastic inside the hot end can ensure a solid structure and bonding properties between the fibers. Examples of fibers include, for example, composite fibers impregnated with a thermosetting binder. Preferred types of fibers used have low porosity and therefore high physical and mechanical properties. Compared to fibers impregnated with thermoplastic polymers, such fibers have the advantage of lower cost because the manufacturing method is much simpler.

[0074] Advantageously, this makes the fabrication of the fibers easier and cheaper than with thermoplastics, i.e. the pre-impregnation process of thermoset polymers. The printing process for thermoset and thermoplastic impregnated fibers is roughly the same in terms of simplicity, but is more expensive.

[0075] The diameter of fiber tube inlet 112 and the diameter of polymer tube inlet 114 are suitable for being compatible with the size of corresponding fiber filament and polymer filament.In one embodiment, the diameter of fiber tube 112 is included between 3 millimeters and 10 millimeters, for example 5 millimeters.In one embodiment, the diameter of polymer tube input 114 is included between 1.5 millimeters and 3 millimeters, for example 1.75 millimeters, corresponding to the diameter of polymer filament.The diameter of the composite filament that can be used for the present embodiment can be in the scope of 0.25 millimeter to 0.8 millimeter.

[0076] Advantageously, the diameter of the through-hole of each of tube inputs 112 and 114 may be individually adjusted to optimize the printing process.

[0077] In one embodiment, the heating element has a cylindrical shape with a diameter comprised between 5 and 10 mm, preferably 6 mm, and a length comprised between 20 and 25 mm.

[0078] In one embodiment, the guide tube 132 for the fiber filaments comprises an assembly of a main tube and a tip element. Both the tube and the tip element are aligned along a common axial channel, the diameter of which is close to the diameter of the fiber filaments.

[0079] Here, the diameter of the channel "close" to the diameter of the filament or fiber is defined as the diameter of the channel being no greater than three times the diameter of the filament or fiber. For example, the thickness of the fiber may be of the order of 0.35 mm, while the diameter of the channel is of the order of 0.9 mm.

[0080] In one embodiment, the conical shape of the tip element and / or any input portion of the guide tube is utilized to ensure that the fiber filament fits into the guide tube. This enables its straightness to be maintained and further prevents any bending. This also avoids that the fiber filament misses the corresponding inlet of the heating unit when feeding or reloading after optional cutting of the fiber filament.

[0081] In one embodiment, below the guide tubes 132 and 134, the bottom of the heating unit 100 includes a heating block 150 that supports a plurality of elements.

[0082] In one embodiment, the heating block 150 includes an input sleeve 121 located below and aligned with the guide tube 132. The input sleeve can be included in and / or used as an inlet of the extruder 140.

[0083] In one embodiment, the extruder 140 includes at least one of the elements 121, 122, and 123. Preferably, the extruder 140 includes an input sleeve 121, a gasket 122, and a printing nozzle 123.

[0084] In one embodiment, the heating block includes a cap element, such as a separate cap component, which is suitable for fixing the elements 121, 122 and / or 123 together inside the heating block 150. This enables the various elements of the extruder assembly 140 to be connected as a single piece.

[0085] In one embodiment, the input cannula 121 has an adjustable opening with the possibility to adjust its diameter so that the size of its inlet can be selected and / or optimized for various parameters of the fiber filament and / or the printing profile.

[0086] In one embodiment, the heating unit includes an empty space 130 or empty space between the guide tube 132 and the input cannula 121 that defines an air gap or “cold zone” of the heating unit 100 .

[0087] Advantageously, the size of the opening or the diameter of this opening can be adjusted so as to form a small hole, thereby ensuring that the fiber filaments, such as the plastic therein, cannot leak out or flow back from above or below.

[0088] In one embodiment, the size of the input sleeve is defined based on the diameter of the fiber. In said embodiment, the diameter of the aperture of the input sleeve has a value greater than the value of the diameter of the fiber and less than three times the value of the diameter of the fiber.

[0089] For example, the diameter of the fiber may be 0.35 mm, while the diameter of the hole of the input sleeve 121 is comprised between 0.6 mm and 0.8 mm.

[0090] In one embodiment, the size of the input cannula is typically comprised between 0.6 mm and 1.2 mm, and preferably from 0.8 mm to 1.0 mm.

[0091] In order to print a part, the fiber filaments passing through the guide tube 132 are displaced through this cold zone to reach the extruder 140, also known as the extruder fiber channel. The input sleeve 121 is located at the height of the entrance of the extruder 140. The input sleeve 121 may include a gasket 122 or be attached to a gasket 122, such as a gasket made of copper. The fiber filaments covered with the molten polymer are then guided to the print nozzle 123 for outputting the material to be printed and are located in the bottom of the heating block 150, the extruder 140 thereby defining the "hot zone" of the heating unit 100. In one embodiment, the extruder includes a cap, which is suitable for covering the area around it. The print nozzle can also be accommodated in the cap, and the cap is preferably bolted to the main structure of the extruder.

[0092] In one embodiment, the print nozzle, whether it is in a cap or not, has a smooth surface so that the fibers are not damaged when leaving the print nozzle.

[0093] In one embodiment, the height of the hot zone, ie the area between the air gap and the nozzle output, is greater than 20 mm. In another preferred embodiment, the height of the hot zone, ie the area between the air gap and the nozzle output, is less than 100 mm.

[0094] The diameter of the input channel of the fiber tube input portion 112 of the heating unit 100 is smaller than the diameter of the output channel in order to minimize the melt production through the channel for feeding the fiber filaments during printing.

[0095] The presence of the interval 130 makes it possible to define an air gap, thereby allowing a maximum temperature difference between the cold zone and the hot zone, or in other words an optimal temperature gradient. When heated above the corresponding temperature, the fiber filaments lose their rigidity and become difficult to shift inside the heating unit without sticking, i.e. considering polymer fusion of the fiber with the polymer filaments.

[0096] Furthermore, the fiber filament heated by the hot zone cannot be pushed more than a few millimeters, which would hinder the extrusion and printing process. Therefore, the defined air gap enables the fiber filament to remain cold and rigid before being guided through and until it reaches the hot zone of the heating unit.

[0097] In one embodiment, upon reaching the extruder 140 , the extruder acts as a printing nozzle that outputs the material to be printed to the outside of the heating unit 100 .

[0098] This defines another advantage of the present disclosure, because in the event of incorrect or over-extrusion of the polymer filaments inside the heating unit, any molten plastic may leak out the sides of the heating unit. Worse, if the molten plastic reaches the cold zone, it may solidify and block the channel through which the fibers are guided. Advantageously, this configuration, combined with the air gap defined by the spacing 130 between the cold and hot zones of the heating unit, ensures that the molten plastic cannot reach the cold zone and hinder the printing process or cause erroneous printing.

[0099] In one embodiment, the column 110 is attached to the heating block 150 of the heating unit 100, in addition to the fiber guide tube 132 and the polymer guide tube 134, so as to form three separate components assembled as such. This assembly is such that the fiber guide tube 132 is arranged or positioned between the column 110 and the polymer guide tube 134.

[0100] In one embodiment, the heating unit 100 has two inputs 112 and 114 via a fiber guide tube 132 and a polymer guide tube 134, one of which is not connected or is not suitable for connection to a superstructure, such as another part of a print head suitable for assembly with (or connection to) the heating unit 100.

[0101] In other words, at least one of the two inputs is separated or adapted to be separated from the upper structure by another air gap. These inputs are adapted to be precisely positioned with the filament supply channel of the upper structure when the heating unit 100 is assembled or connected with another part of the print head.

[0102] Advantageously, when assembling the printhead, the column 110 enables optimization of the alignment of the heating unit 100 with at least one other portion of the printhead, and most specifically, the alignment of the fiber guide tube with the polymer guide tube. Furthermore, by positioning the heating unit 110 with the other portions of the printhead so that two of their main axes are aligned, assembly of the heating unit 110 with the other portions of the printhead is made simple, fast and efficient, said main axis being preferably vertical.

[0103] In one particular embodiment, aligning the column and the polymer supply tube with the vertical axis of another portion of the printhead is sufficient to ensure optimal positioning, and thus size, of the air gap therebetween.

[0104] In one embodiment, the column comprises a material made of titanium alloy or stainless steel.

[0105] Advantageously, columns comprising titanium have low thermal conductivity and high mechanical properties.

[0106] Reference now Figure 4 , shows a gasket for a heating unit according to one embodiment.

[0107] In one embodiment, the horizontal guide channel 125 defines a hollow space or empty space provided in the heating block 150 of the heating unit 100, which is suitable for accommodating the gasket 122 as shown. The thickness of the gasket 122 is preferably slightly greater than the depth of the empty groove to ensure that the gasket 122 is firmly pressed by the upper part of the bottom of the heating block 150 when the heating unit is assembled.

[0108] In one embodiment, in particular, this spacer 122 is located below the fiber guide tube 132 and the polymer guide tube 134 in the bottom of the heating unit 100 .

[0109] In one embodiment, the gasket 122 includes a solid portion 1222 and a hollow portion 1224. The solid portion 1222 of the gasket 122 is made of a material having high thermal conductivity, such as a metal, preferably copper. Advantageously, the use of copper ensures that the supplied polymer or plastic has a uniformly distributed temperature, avoiding defects in the resulting composite product.

[0110] In one embodiment, the hollow portion 1224 includes a slit having a width greater than at least the smallest diameter of the fiber guide tube 132 and the polymer guide tube 134. In a specific embodiment, the hollow portion 1224 includes a narrowing cutout that is large enough to allow the material output by the extruder 140 to be guided into the printing nozzle 123 of the heating unit 100.

[0111] This enables most, if not all, of the material output by the extruder 140 to be directed into the print nozzle 123, from the approximately 2 mm diameter polymer guide tube 134 into the approximately 1 mm diameter fiber feed region. The materials used for the above elements are adapted to maintain a uniform temperature of the temperature thereof and of all surrounding plastic components. In addition, all connections between these elements and components are sealed, so that the outflowing plastic can only be directed through the holes of the gasket 122 and / or guide tube, the extruder and the print nozzle.

[0112] In one embodiment, the gasket comprises a sheath made of a metal, such as copper, that is slightly thicker than the nominal space available in the heating unit 100 to accommodate it.

[0113] In one embodiment, the size of the sheath is about 1 mm, and the cutout is slightly smaller, such as 0.9 mm. When the gasket 122 is placed in the heating unit, for example, when it is bolted inside the heating unit, the metal parts are pressed against the inner wall of the heating unit, thereby providing an optimal seal.

[0114] Narrowing the guide channel also enables the plastic to move at an increased speed without any gaps or dead zones for the material flow. This improves the quality of the printing process, since no buildup of burnt coating occurs, thus avoiding clogging of the print head or the heating unit. This also makes it possible to avoid residual plastic or polymer on the sides. Otherwise, such residues could require maintenance of the print head after a few days of intensive use.

[0115] Reference now Figure 5 , showing a print head according to one embodiment.

[0116] In this embodiment, the print head includes a plurality of individual heating units, also referred to as "hot ends".

[0117] Specifically, the print head 200 includes two separate heating units 210 and 220, the first heating unit 210 is a plastic hot end, i.e., a heating unit intended for heating, guiding and / or feeding plastic filaments, and the second heating unit 220 is a composite hot end, i.e., a heating unit intended for heating, guiding and / or feeding composite filaments.

[0118] In one embodiment, the print head may also include other elements, including but not limited to a mechanism for supplying plastic filaments, a mechanism for supplying reinforcing fibers, another mechanism for cutting reinforcing fibers, one or more supply tubes for any type of filaments, and one or more supply tubes for any type of reinforcing fibers.

[0119] In one embodiment, the print head 200 also includes a main support 250 that holds all components and parts.

[0120] In one embodiment, the plastic hot end 210 is adapted to be retractable, such as by a switching mechanism 240 .

[0121] Advantageously, the switching mechanism 240 comprises a horizontal rod adapted to rotate with the nozzle. The horizontal rod is also adapted to move along a diagonal axis located on the main support 250. The rotational movement of the rod enables the nozzle to move vertically.

[0122] Additionally, the switching mechanism 240 enables positioning of the plastic hot end 210 at different height positions, including above or below the position of the print nozzle of the composite hot end 220 .

[0123] In one embodiment, the plastic hot end 210 is adapted to be fixed to the main support 250 and is not movable relative to the print head or relative to the main support.

[0124] The print head circuit board is mounted below the servo mechanism and connects all the electrical components to the control lines which connect to the printer's main board.

[0125] In one embodiment, the composite hot end 220 includes a cutting mechanism 230 disposed on a main support of the print head 200 .

[0126] In one embodiment, the cutting mechanism 230 comprises one or more rotatable cylindrical cutters. Preferably, the one or more rotatable cylindrical cutters comprise a radial hole and at least one cylindrical sleeve fixed to the radial hole.

[0127] These more rotatable cylindrical cutters enable high precision fit by cylindrical surfaces. Advantageously, these rotatable cylindrical cutters can be placed in a suitable position so that the guidance of the filament through the print head path is not hindered by any element.

[0128] In one embodiment, the composite hot end 220 further includes a servo motor or machine configured to control and rotate a rotatable cylindrical cutter adapted to cut or break the fibers passing through the radial holes.

[0129] The above are embodiments of the present invention, which do not limit the scope of the present disclosure. Equivalent structures or equivalent process changes made by using the contents of the present disclosure and the drawings or directly or indirectly applying to other related technical fields are also included in the scope of the present disclosure and the present invention.

Claims

1. A heating unit (100; 220) for a print head (200), the heating unit comprising: - at least two guide tubes (132, 134), each guide tube being adapted to be connected to an extruder (140), a first guide tube (132) of the at least two guide tubes being adapted to guide fiber filaments from a first inlet (112) of the first guide tube to the extruder, and a second guide tube (134) of the at least two guide tubes being adapted to guide polymer filaments from a second inlet (114) of the second guide tube to the extruder, - a heating element suitable for melting the polymer filaments guided in the second guide tube (134) to the extruder, - a horizontal guide channel (125) connected to the extruder (140) and located below the first guide tube (132) and the second guide tube (134), the horizontal guide channel being suitable for guiding the molten polymer from the second guide tube to the extruder, - said extruder (140) being suitable for forming a composite material by covering said fiber filaments guided to said extruder in said first guide tube (132) with molten polymer filaments, and - a printing nozzle (123) connected to the extruder and adapted to print a composite part by outputting the composite material outside the heating unit.

2. The heating unit according to claim 1, wherein: The fiber filaments are selected from carbon fiber filaments, glass fiber filaments, composite fiber filaments, optical fiber filaments or Kevlar fiber filaments.

3. The heating unit according to any one of claims 1 or 2, wherein: The polymer filaments are selected from thermoplastic polymer filaments such as polyetheretherketone, polyetherketoneketone, polyetherimide, polysulfone, polyphenylsulfone and polyethersulfone.

4. The heating unit according to any of the preceding claims, further comprising a heat sink (116) positioned around a portion of the length of a guide tube adapted to guide the polymer filaments and axially aligned with the vertical axis of the guide tube.

5. A heating unit according to any one of the preceding claims, wherein The heating unit further comprises a heating block (150), and each of the at least two guide tubes (132, 134) is fixed on a first upper side of the heating block, the heating block further comprises the extruder (140) and the printing nozzle (123), the printing nozzle is positioned in the heating block so that the composite material is output outwardly from the heating block and from a lower side of the heating block, the lower side being opposite to the upper side, and the heating block further comprises the heating element.

6. The heating unit according to claim 5, further comprising a column (110) attached to the heating block, the first guide tube (132) being located between the column (110) and the second guide tube (132).

7. The heating unit according to claim 5 or 6, wherein: The heating block (150) comprises a first region (170) referred to as thermistor region, which is suitable for accommodating at least one thermal sensor and / or thermistor, and a second region (172) referred to as heater region, which is suitable for accommodating at least one heating element.

8. The heating unit according to any one of claims 5 to 7, wherein: The heater zone (172) includes at least one receiving portion adapted to receive the heating element.

9. The heating unit according to any one of claims 5 to 8, wherein: The horizontal guide channel (125) comprises a hollow space formed in the heating block (150) of the heating unit (100), the hollow space being located below the at least two guide tubes (132, 134) attached to the heating block (150) and being adapted to accommodate a gasket (122) having a corresponding size and shape.

10. The heating unit according to any one of claims 5 to 9, wherein: The heating block (150) comprises an input sleeve (121) located below the guide tube (132) and suitable for guiding the fiber filaments, wherein the input sleeve (121) has an opening, and the diameter of the opening can be adjusted to control the flow of the fiber filaments.

11. The heating unit according to claim 10, further comprising an empty space (130), wherein the empty space defines an air gap between the second guide tube (132) and the input sleeve (121).

12. The heating unit according to any one of the preceding claims, further comprising a gasket (122) suitable for being assembled inside the horizontal guide channel (125), the gasket comprising a solid portion (1222) and a hollow portion (1224) located inside the solid portion, the solid portion being made of a material having high thermal conductivity, the hollow portion comprising a gradually narrowing cutout, the width of the cutout being large enough to guide the molten polymer filament toward the printing nozzle (123).

13. A print head (200), comprising: - Main support (250), - two heating units (210, 220) attached to the main support, one of the two heating units being a heating unit according to any of the preceding claims, - a cutting mechanism (230), attached to the main support, for cutting the fiber filaments, and - A switching mechanism (240) attached to the main support for controlling the height of one of the two heating units or controlling the height of both heating units.

14. The print head according to claim 13, wherein: The cutting mechanism (230) includes one or more rotatable cylindrical cutters, each rotatable cylindrical cutter including a radial hole and at least one cylindrical sleeve fixed to the radial hole.

15. The print head according to claim 13 or 14, wherein: The switching mechanism (240) comprises a rod, which is configured to control the vertical position of a printing nozzle of one of the two heating units or to control the vertical position of the printing nozzles of the two heating units.

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