US-12617154-B2 - Deposition process optimization system multi extruder and related method

US12617154B2US 12617154 B2US12617154 B2US 12617154B2US-12617154-B2

Abstract

A system for optimizing the multi-extruder deposition process in a 3D printer including multiple extruders requires each extruder to have a body including an outer thermal insulation shell; the shell allowing the inlet/outlet of a fluid for the active and controlled refrigeration of the extruder. A method for optimizing the multi-extruder deposition process in a 3D printer with multiple extruders involves managing the temperature of each extruder using active refrigeration sized so as to have a sudden control of the cooling ramp and to manage the viscosity of the material in the event of extruder change. For the entire duration of the printing with another extruder, the unused extruder nozzle remains in a limited range around the extrusion temperature, thus eliminating downtime, while the solidified filament from the sudden forced cooling is pulled back into a low temperature nozzle area where it does not degrade during non-use.

Inventors

Alessio LORUSSO
Simone CUSCITO
Antonio SAPONARA
Flavio CICCARONE
Marino ANDRIANI
Matteo Rege′

Assignees

ROBOZE S.P.A.

Dates

Publication Date: 20260505
Application Date: 20231002
Priority Date: 20220930

Claims (20)

1 . A system for performing a multi-extruder deposition process in a 3D printer with two or more extruders, the system comprising: a) an outer thermal insulation shell, which is made with one or more materials having low heat exchange coefficients; said shell being configured to allow the inlet/outlet of a fluid for the active and controlled refrigeration of the extruder; b) at least one extruder; wherein said extruder has a body comprising: a polymer melting tank, an extruder nozzle, a temperature probe; a first hole for housing a heating resistor of the polymer melting tank; a second hole for housing the extruder nozzle; one or more refrigeration holes for the melting tank; a third hole for housing the temperature probe; or said extruder has a body comprising: a nozzle; a containment structure for the nozzle in which the nozzle itself is inserted, a circular band heating resistor, in which a temperature probe is integrated, is keyed onto such containment structure; a space about the heating resistor, in which the active and controlled refrigeration fluid flows about the heating resistor substantially following a spiral path starting from a lower inlet towards an outlet in an upper part, thus taking advantage of the best heat exchange coefficient determined by the swirling motion.
2 . The system according to claim 1 , wherein a lower end of the second hole for housing the nozzle has an edge with a geometry designed to favor the conduction of heat towards the area of contact with a lower tip of the nozzle itself.
3 . The system according to claim 2 , wherein said lower edge of the second hole for housing the nozzle is cylindrical or conical.
4 . The system according to claim 1 , wherein said first hole for housing the heating resistor is a through hole or a blind hole.
5 . The system according to claim 1 , further comprising means for fastening the nozzle onto the extruder body which are of the fixed type or with fast coupling/release.
6 . The system according to claim 5 , wherein, in the event of a fixed fastening, the extruder is hyperstatically bound with mechanical components which do not allow for a fast replacement of the nozzle.
7 . The system according to claim 5 , wherein, in the event of a fastening with fast coupling/release, the extruder is isostatically bound by manually or mechanically operated means, adapted to allow a fast replacement of the nozzle.
8 . The system according to claim 1 , wherein the resistor which heats the polymeric material in the melting tank absorbs a power comprised between 60 W and 300 W and is powered with voltages comprised between 12 V and 48 V.
9 . The system according to claim 1 , further comprising secondary cooling means, configured to act as a thermal break transversal to the nozzle, suitably arranged in the extruder body.
10 . The system according to claim 1 , wherein said active refrigeration is obtained by means of compressed air or other fluids to be lost in the environment or in a closed circuit; wherein the compressed air is directly or indirectly directed onto the nozzle or other components of the extruder.
11 . The system according to claim 10 , wherein inside the extruder body there are channels or ducts configured to direct the flow of air or of the cooling fluid to specific points, with a flow comprised between 20 L/min and 40 L/min.
12 . The system according to claim 11 , wherein the lower inlet opens into a first chamber where the fluid is distributed on transverse refrigeration holes, which open into a second chamber to which the outlet of the fluid itself is connected.
13 . The system according to claim 12 , wherein said refrigeration holes are arranged between the nozzle and the resistor, so that when the active refrigeration fluid passes therethrough, a relatively cooler barrier is created, parallel to the nozzle which applies a break to stop the heat flow coming from the resistor in the extruder body.
14 . The system according to claim 1 , further comprising inserts made of different materials, configured to ensure specific temperature ranges in different points of interest.
15 . The system according to claim 14 , wherein in the lower end part of the extruder body there are surface coatings or inserts, adapted to favor the heat exchange towards the lower area of the extruder, where the tip of the nozzle is placed.
16 . The system according to claim 15 , wherein such coatings or inserts are made of materials with predetermined heat exchange coefficients.
17 . The system according to claim 1 , wherein the body of said nozzle consists of a loading channel, a nozzle and a support cannula of the nozzle itself.
18 . The system according to claim 17 , wherein said nozzle and said support cannula are inserted into a corresponding containment structure of the nozzle itself, onto which said circular band heating resistor is keyed.
19 . The system according to claim 1 , wherein said outer shell is made of a monolithic ceramic material, or of a multilayer material, or of a non-ceramic material.
20 . The system according to claim 17 , wherein a continuous flow of compressed air is fed to the extruder by means of an upper junction, through a channel present in a special conveyor which is configured to direct the compressed air both to a thermal break area present on the support cannula of the nozzle, and to an air heat exchanger.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the priority under 35 USC 119(a) of IT patent application 102022000020223 filed on Sep. 30, 2022, the entirety of which is incorporated herein by reference. BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to the sector of 3D printing of three-dimensional objects, with a particular reference to the issues relating to the need to switch from one extruder to another of the same 3D printer, to use two or more different materials during the printing. More specifically, the invention relates to an innovative extruder, which below will also be called HVP-PRO (High Viscosity Polymers-Professional), which is an extruder designed for FFF technology 3D printers optimized for the extrusion of high performance polymers and for printing processes which involve the use of multiple filaments, and therefore respective extruders that must be used alternating from one to the other one, during the 3D printing of the same piece. Description of the Related Art Generally, the air or liquid refrigeration used in 3D printers performs a thermal break function, or the protection of the electrical components. It is also used to avoid thermal deformations and/or softening of the filament in areas other than the melting tank of the extruder, or alternatively, in the case of low-melting polymers, to refrigerate, and therefore solidify, the melted material once deposited. It is a peculiar feature of the present invention that—conversely to what is known—refrigeration is used for an active control of the temperature inside the melting tank, so as to modify the viscosity of the polymer based on the stage of the printing process, and reduce the times needed for the extruder heating and cooling steps. As it will be better described below, the extruder which is the subject of the present invention has been designed to achieve at least the following objects: Controlling the thermal profile and viscosity of the polymer by means of an active refrigeration systemIncreasing the printing speedsReducing preheating times by virtue of an improved energy efficiencyReducing the number of components with respect to existing technologies In addition thereto, the present invention provides a better printing performance which also derives from the increase in the extrusion speed which may not be achieved with parameter optimization alone. In this regard, it should be noticed that as the temperature increases beyond a certain threshold, there is a corresponding polymer degradation with direct consequences on the performance of the finished component; a further significant increase in temperature may cause the rapid carbonization of the molten fluid inside the duct, thus preventing the extrusion itself. Increasing the speed would correspond to a reduction in the mechanical properties of the part created, due to a lower temperature of the molten fluid exiting the nozzle, as well as an increase in printing failures due to the increase in pressure inside the melting tank which would require an increase in thrust on the filament to achieve the extrusion. From the above considerations, it may be understood that, even increasing the “Extrusion temperature” and the “Extrusion speed”, using currently known equipment, it is not possible to obtain the desired performance. The HVP-PRO extruder according to the present invention is substantially a suitably machined metal block, made up of one or more parts welded to one another, and integral with the printing head of the 3D printer. The HVP-PRO therefore overcomes the issue of needing to replace the extruder in the event of clogging or in the event of using filaments with different melting points. This leads to a significant reduction in machine preparation times and to a lesser wear of the electrical parts of the extruder which are sensitive to the manual skills of the user. The reduced waste material and the shortened preparation times lead to greater printer productivity and a lower environmental impact. The extruder described, thus, is to be considered an integral part of the printer and no longer a consumable item. Another peculiar application of the invention relates to the case in which the printing process involves multiple extruders, where it is essential to optimize the times used during the activation and deactivation sequence thereof. Commonly, this function is managed by passivating (i.e., cooling) the extruder during the entire period in which it is not directly involved in the printing process, to avoid the degradation of the polymer inside the melting tank thereof and losses of material on the printed part which would cause unwanted inclusions in the product which would make it unusable. It should be noticed that, in the case of super-polymers, this strategy is not effective due to the high process temperatures involved. The thermal inertia of the extruder, both during the heating and cooling steps, significant