Additive print head and method of reconfiguring the same

Abstract

An additive print head (1) has a plasticizing cylinder (2); an extrusion nozzle (3) coupled to the plasticizing cylinder (2); a feed screw (4) to advance the polymeric material inside the plasticizing cylinder (2) toward the extrusion nozzle (3) and eject the plasticized polymeric material through the extrusion nozzle (3); a tip (5) mounted on the end of the feed screw (4) in proximity of said extrusion nozzle (3); a rotary actuator (6) integral to the plasticizing cylinder (2) and configured to rotate the feed screw (4); a first add-on (13) of tubular shape configured to be mounted between the plasticizing cylinder (2) and the extrusion nozzle (3) and having a feed port (14) to feed an inert gas; and a second add-on (15) configured to be mounted at the end of the feed screw (4) and to mix the plasticized polymeric material and the inert gas within the first add-on (13).

Description

[0001] "ADDITIVE PRINT HEAD AND METHOD OF RECONFIGURING THE SAME"

[0002] Cross-Reference to Related Applications

[0003] This Patent Application claims priority from Italian Patent Application No . 102024000019840 filed on September 5 , 2024 , the entire disclosure of which is incorporated herein by reference .

[0004] Background of the Invention

[0005] The present invention relates to an additive print head for printing thermoplastic polymers starting from granules or flakes of thermoplastic material .

[0006] Prior Art

[0007] As known, the process of additive printing of a thermoplastic polymer provides for feeding a thermoplastic polymer in granules or flakes to an additive print head, advancing the polymer by means of a feed screw inside a plastici zing cylinder generally heated by electrical resistors towards an extrusion noz zle , through which a layer of thermoplastic material is deposited on a support or above a previously deposited layer .

[0008] The possibility o f obtaining complex shapes is made possible by the mobility of the additive print head with respect to the support and possibly by the mobility of the support .

[0009] Additive print heads are also known which are configured to add the melted polymer with an inert gas and to mix the inert gas with the melted polymer, so as to give the melted polymer a homogeneous cellular structure and with a density lower than the density of the melted polymer in the absence of gas .

[0010] In the present context , the term "mix" is intended to allow the inclusion of inert gas bubbles evenly distributed inside the mass of plastici zed polymeric material .

[0011] The products obtained with this technique are often defined as " foamed" and have various applications in many technical sectors and are manufactured with an additive print head speci fically configured to obtain foamed products .

[0012] Additive print heads for manufacturing products in "non-foamed" polymeric material and additive print heads for manufacturing products in " foamed" polymeric material exist on the market .

[0013] The obj ect of the present invention is to obtain an additive print head for manufacturing products in " foamed" and "nonfoamed" polymers .

[0014] Object of the invention

[0015] According to the present invention, an additive print head for thermoplastic polymers is obtained, the additive print head comprising :

[0016] - a plastici zing cylinder to plastici ze the polymeric material ;

[0017] - an extrusion noz zle coupled to the plastici zing cylinder at one end of the plastici zing cylinder ;

[0018] - a feed screw rotating about a longitudinal axis to advance the polymeric material inside the plastici zing cylinder ( 2 ) toward the extrusion nozzle and ej ect the plastici zed polymeric material through the extrusion noz zle ;

[0019] - a tip mounted on the end of the feed screw in proximity of said extrusion noz zle ;

[0020] - a rotary actuator integral to the plastici zing cylinder and configured to rotate the feed screw around said longitudinal axis ; and - a first add-on of tubular shape configured to be mounted between the plastici zing cylinder and the extrusion noz zle and having a feed port to feed an inert gas inside the first addon; and

[0021] - a second add-on configured to be mounted at the end of the feed screw in place of the tip and configured to mix the plastici zed polymeric material and the inert gas within the first add-on of tubular shape .

[0022] In this manner, it is possible to modi fy an existing additive print head for printing "non-foamed" products with assembly of the first and the second add-on in order to print " foamed" products .

[0023] In particular, the first add-on comprises a tubular body made of a metal material configured to be attached to the plastici zing cylinder and an attachment integral with the tubular body and configured to be connected with a tube to feed the inert gas at said feed port .

[0024] In this manner, the additive print head can be easily connected to an inert gas source .

[0025] Conveniently, the first add-on comprises an electrical resistor arranged around the tubular body, so as to maintain the polymeric material at a temperature that facilitates mixing with the inert gas .

[0026] The first add-on comprises a pressure sensor, which extends through the tubular body facing the feed port to detect a pressure signal of the inert gas in the mixing zone . Mixing between the polymeric material in the plastic state and the inert gas is influenced by the pressure .

[0027] In order to obtain a correct mixing of the inert gas , it is also important to have confirmation of the temperature inside the first add-on, so the first add-on comprises a temperature sensor that extends through the tubular body .

[0028] In particular, the first add-on is conveniently connected to the plastici zing cylinder and to the extrusion noz zle by means of respective threaded connections .

[0029] The second add-on comprises a shaft configured to be screwed to the feed screw and a plurality of arms that extend from the shaft , particularly in a radial direction within the first addon, so as to facilitate the inclusion of inert gas bubbles inside the mass of plastici zed polymeric material and their even distribution inside that mass .

[0030] The present invention also relates to an additive printing system comprising an additive print head as identified above and a control unit configured to control the rotary actuator and heating of the plastici zing cylinder and an inert gas source connectible to the additive print head by means of a hose , in particular a flexible hose , to allow full mobility of the additive print head .

[0031] In particular, the system comprises a pressure reducer and flow meter selectively connectible to the control unit , in order to control the pressure of the inert gas , based on the signal correlated to the pressure inside the first add-on . A further obj ect of the present invention is to reconfigure an additive print head .

[0032] In accordance with the present invention, a method of reconfiguring an additive print head is provided, the method comprising :

[0033] - removing an extrusion noz zle from a plastici zing cylinder of the additive print head;

[0034] - removing a tip arranged at the free end of a feed screw;

[0035] - mounting a second add-on configured to mix the plastici zed polymeric material and inert gas at the free end of the feed screw;

[0036] - mounting a first add-on of tubular shape and having a feed port to feed an inert gas to the free end of the plastici zing cylinder ;

[0037] - mounting the extrusion noz zle at the free end of the first add-on .

[0038] In this manner, it is possible to modi fy an existing additive print head for printing "non-foamed" products with assembly of the first and the second add-on in order to print " foamed" products .

[0039] Brief Description of the Drawings

[0040] For a better understanding of the present invention, an embodiment will now be described, by way of non-limiting example , with reference to the appended drawings , in which :

[0041] Figure 1 is a longitudinal cross-sectional view, with parts removed for clarity, of an additive print head configured to print "non- foamed" products ; Figure 2 is a partially exploded longitudinal cross- sectional view, on an enlarged scale and with parts removed for clarity, of the additive print head of Figure 1 ;

[0042] - Figure 3 is a longitudinal cross-sectional view, with parts removed for clarity, of the additive print head of Figure 1 , partially modi fied to adapt it to printing of " foamed" products ;

[0043] Figure 4 is a partially exploded longitudinal cross- sectional view, on an enlarged scale and with parts removed for clarity, of the additive print head of Figure 3 ;

[0044] Figure 5 is a partially schematic and partially cross- sectional view, with parts removed for clarity, of a system for printing " foamed" products comprising the additive print head of Figure 3 .

[0045] Preferred embodiment

[0046] With reference to figure 1 , the number 1 denotes , in its entirety, an additive print head, which is configured to plastici ze , extrude and print a thermoplastic polymeric material for manufacturing "non-foamed" products .

[0047] The additive print head 1 extends along a longitudinal axis A and comprises a plastici zing cylinder 2 to plastici ze the polymeric material ; an extrusion noz zle 3 mounted on the plastici zing cylinder 2 at the free end of the plastici zing cylinder 2 ; a feed screw 4 rotating about the longitudinal axis A which also defines an axis of rotation to advance the polymeric material inside the plastici zing cylinder 2 towards the extrusion noz zle 3 and expel the plastici zed polymeric material through the extrusion noz zle 3 ; a tip 5 mounted on the end of the feed screw 4 in proximity of the extrusion noz zle 3 ; and a rotary actuator 6 integral to the plastici zing cylinder 2 and configured to rotate the feed screw 4 around said longitudinal axis A.

[0048] The additive print head 1 comprises a feed conduit 7 , which is configured to feed the polymeric material in the solid state to the plastici zing cylinder 2 , is arranged on one side of the plastici zing cylinder 2 and converges into the plastici zing cylinder 2 . Generally, the polymeric material is fed in the solid state , in the form of granules or flakes .

[0049] With reference to Figure 2 , generally the plastici zing cylinder 2 comprises a metal tubular body 8 and electrical resistors 9 arranged around the tubular body 8 , powered by electric cables 10 .

[0050] The extrusion noz zle 3 is defined by a convergent tubular body and is mounted on the tubular body 8 by means of a threaded connection . In the case illustrated, the tubular body 8 has external threading obtained on one wall of the tubular body 8 with reduced outer diameter, whereas the extrusion noz zle 3 comprises an internal threading obtained on one wall of the extrusion noz zle 3 with increased diameter .

[0051] The feed screw 4 comprises a cylindrical body 11 and a helical protrusion 12 with rectangular cross-section that extends radially from the cylindrical body 11 and extends around the longitudinal axis A.

[0052] The external end of the helical protrusion 12 is adj acent to the inner face of the tubular body 8 and defines , between the cylindrical body 11 and the helical protrusion 12 , a helical interspace for housing the polymeric material . The diameter of the cylindrical body 11 is close to the inner diameter of the tubular body 8 , in order to reduce the radial extension of the helical interspace and facilitate contact between the hot wall of the tubular body 8 and the polymeric material .

[0053] With reference to Figure 1 , the print head is controlled by a control unit C provided with a user interface U to control the rotary actuator 6 and the electrical resistors 9 .

[0054] The additive print head 1 described performs the functions of plastici zing the polymeric material along the plastici zing cylinder 2 , advancing the polymeric material along the plastici zing cylinder 2 towards the extrusion noz zle 3 by means of the feed screw 4 , and extruding the plastici zed polymeric material through the extrusion noz zle 3 on a support or on a previously extruded and solidi fied polymeric material .

[0055] Figure 3 illustrates the additive print head 1 modi fied to make it suitable for obtaining " foamed" products , i . e . products in polymeric material with a cellular structure determined by the addition of inert gas to the plastici zed polymer inside the additive print head .

[0056] The modi fied additive print head 1 does not have the tip 5 and comprises an add-on 13 of tubular shape configured to be mounted between the plastici zing cylinder 2 and the extrusion noz zle 3 and having a feed port 14 to feed an inert gas inside the addon 13 ; and an add-on 15 configured to be mounted at the end of the feed screw 4 and configured to mix the plasticized polymeric material and the inert gas inside the tubular add-on 13 . The add-on 13 comprises a tubular body 16 made of a metal material configured to be attached to the plastici zing cylinder 2 and an attachment 17 integral with the cylindrical body 16 and configured to be connected with a feed tube 18 ( Figure 5 ) to feed the inert gas at said feed port 14 .

[0057] The add-on 13 comprises an electrical resistor 19 arranged around the tubular body 16 to heat the tubular body 16 .

[0058] The add-on 13 comprises a pressure sensor 20 , which extends through the tubular body 16 at the feed port 14 and is configured to acquire a signal correlated to the pressure of the inert gas inside the add-on .

[0059] The add-on 13 comprises a temperature sensor 21 that extends through the cylindrical body 16 to acquire a signal correlated to the temperature of the tubular body 16 .

[0060] The add-on 13 is connected to the plastici zing cylinder 2 and to the extrusion noz zle via respective threaded connections and, in practice , the two tubular bodies 8 and 16 are screwed onto one another .

[0061] The second add-on 15 comprises a shaft 22 configured to be screwed to the feed screw 4 and a plurality of arms 23 that extend from the shaft 22 , particularly in a radial direction within the add-on 13 , in order to mix the gas inside the plastici zed polymeric material to define a plastici zed polymer with cellular structure . As shown in Figure 5 , a system for obtaining products with a cellular structure , i . e , " foamed" products , is illustrated, which comprises the modi fied additive print head 1 ; the control unit C and an inert gas source 23 connected to the additive print head 1 via the hose 18 , in this case a flexible hose to guarantee freedom of movement of the additive print head 1 .

[0062] The inert gas source 24 is substantially defined by a CO2 or compressed air canister at a pressure comprised between ... and ...

[0063] The system comprises a pressure reducer 25 and a flow meter 26 , in order to measure and adj ust the quantity of inert gas fed to the additive print head 1 , based on the design parameters and to vary the density of the products obtained with the additive printing .

[0064] In this manner, it is possible to adj ust the quantity of gas also in manufacturing of a product which, based on the design, has a variable density . This is a technique known as densitybased topology optimi zation, which provides for the use of computational techniques to distribute the material in an optimal manner inside a defined domain, based on criteria such as minimising the weight and / or minimising the sti f fness .

[0065] Reconfiguration of the additive print head is relatively easy, as it provides for performing the following operations :

[0066] - removing the extrusion noz zle 3 from the plastici zing cylinder 2 ;

[0067] - removing the tip 5 arranged at the free end of a feed screw 4 ; mounting the add-on 15 configured to mix the plastici zed polymeric material and inert gas at the free end of the feed screw 4 ;

[0068] - mounting the add-on 13 at the free end of the plastici zing cylinder 2 ; and - mounting the extrusion noz zle 3 at the free end of the add-on

[0069] 13 .

[0070] Furthermore , it is necessary to connect the resistor 19 , the pressure sensor 20 and the temperature sensor 21 with the control unit C ; connect the inert gas source 23 to the attachment 17 via the hose 18 ; and connect the pressure reducer 25 and the flow meter to the control unit C .

[0071] It is also clear that changes and variants may be made to the embodiment described and illustrated here without thus deviating from the scope of protection as defined by the appended claims .

Claims

CLAIMS1. An additive print head for thermoplastic polymers, the additive print head (1) comprising: a plasticizing cylinder (2) to plasticize the polymeric material ;- an extrusion nozzle (3) coupled to the plasticizing cylinder (2) at one end of the plasticizing cylinder (2) ;- a feed screw (4) rotating about a longitudinal axis (A) to advance the polymeric material inside the plasticizing cylinder (2) toward the extrusion nozzle (3) and eject the plasticized polymeric material through the extrusion nozzle (3) ;- a tip (5) mounted on the end of the feed screw (4) in proximity of said extrusion nozzle (3) ;- a rotary actuator (6) integral to the plasticizing cylinder (2) and configured to rotate around said longitudinal axis (A) the feed screw (4) ; and- a first add-on (13) of tubular shape configured to be mounted between the plasticizing cylinder and the extrusion nozzle (3) and having a feed port (14) to feed an inert gas inside the first add-on (13) ; and- a second add-on (15) configured to be mounted at the end of the feed screw (4) in place of the tip (5) and configured to mix the plasticized polymeric material and the inert gas within the first add-on (13) of tubular shape.

2. The print head as claimed in claim 1, wherein the first addon (13) comprises a tubular body (16) made of a metal material configured to be attached to the plasticizing cylinder (2) and an attachment (17) integral with the tubular body and configured to be connected with a tube (18) to feed the inert gas at saidfeed port ( 14 ) .

3. The print head as claimed in claim 2, wherein the first addon (13) comprises an electrical resistor (19) arranged around the tubular body (16) .

4. The print head as claimed in claim 2 or 3, wherein the first add-on (13) includes a pressure sensor (20) , which extends through the tubular body opposite the feed port (14) .

5. The print head as claimed in any one of claims 2 to 4, wherein the first add-on (13) comprises a temperature sensor extending through the tubular body (16) .

6. The print head as claimed in any one of the preceding claims, wherein the first add-on (13) is connected to the plasticizing cylinder (2) and the extrusion nozzle (2) via respective threaded connections.

7. The print head as claimed in any one of the preceding claims, wherein the second add-on (15) comprises a shaft (22) configured to be screwed to the feed screw (4) and a plurality of arms (23) extending from the shaft (22) , particularly in a radial direction within the first add-on component (13) .

8. An additive printing system comprising an additive print head as claimed in any one of the preceding claims, the system comprising a control unit (C) configured to control the rotary actuator (6) and the heating of the plasticizing cylinder (2) .

9. The additive printing system as claimed in claim 8 andcomprising an inert gas source (23) connectible to the additive printing head via a hose (18) , in particular a flexible hose.

10. The system as claimed in claim 9 and comprising a pressure reducer and flow meter selectively connectible to the control unit (C) .

11. A method of reconfiguring an additive print head, the method comprising :- removing an extrusion nozzle (3) from a plasticizing cylinder (2) of the additive print head;- removing a tip (5) arranged at the free end of a feed screw (4) ;- mounting a second add-on (15) configured to mix the plasticized polymeric material and inert gas at the free end of the feed screw ( 4 ) ;- mounting a first add-on (13) of tubular shape and having a feed port (14) to feed an inert gas to the free end of the plasticizing cylinder (2) ;- mounting the extrusion nozzle (3) at the free end of the first add-on ( 13 ) .

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