Device and method for improving strength of material extrusion printing workpiece

Abstract

The invention discloses a device and method for improving the strength of a material extrusion printing workpiece, the device comprises a spray head, the spray head comprises a body, a printer consumable molten liquid channel is formed in the middle of the body, and an inlet of the printer consumable molten liquid channel is communicated with a wire feeding outlet of a wire feeding mechanism of an extrusion printer; a spinneret orifice is formed in an outlet of the printer consumable molten liquid channel, and the spinneret orifice is arranged according to a preset spinneret section shape; the spray head is connected with the rotating mechanism, the spray head can rotate under the driving of the rotating mechanism, the printer consumables flowing out of the spinneret orifices can generate directional deflection around the axis of the printer consumables under the rotation of the spray head, and a laying and stacking structure is formed according to a set form so as to increase the contact area between jets. By adopting the device and the method, a larger contact area between the filaments can be obtained, the bonding strength between the sprayed filaments is improved, and then the strength of a printed workpiece is improved.

Description

Technical Field

[0001] The present invention relates to the field of additive manufacturing, and in particular to a device and method for improving the strength of a workpiece printed by extrusion of a material. Background Art

[0002] Material extrusion is a type of additive manufacturing process. Typical materials such as thermoplastics and structural ceramics are extruded through nozzles or orifices to form spinnerets. The spinnerets are printed and laid layer by layer, and the spinnerets are bonded together by thermal bonding or chemical reaction to form a workpiece. The connection strength between the spinnerets is strongly positively correlated with the contact area between the spinnerets. Since the spinneret holes currently used for material extrusion are all circular, the extruded spinnerets are cylindrical. In theory, the contact between the spinnerets can only achieve line (cylindrical line) contact, and the contact area is small, thus forming a large gap, resulting in low inter-layer / intra-layer bonding strength and significant anisotropy in the mechanical properties of the printed workpiece.

[0003] At present, relevant scholars in this field have completed some strengthening research, such as Document 1: "CN 115338426 A A device and method for strengthening 3D printed workpieces" discloses a device and method for repairing tiny holes and defects inside printed metal workpieces and strengthening the surface of the workpiece by combining electromagnetic induction heating and ultrasonic cavitation. The method in Document 1 belongs to post-processing of printing and is only applicable to printed workpieces made of metal materials. Material extrusion workpieces do not have the ability to generate heat by induction because the material is non-metallic. Therefore, the method in Document 1 cannot be used to strengthen material extrusion prints, and strengthening cannot be achieved during the layer-by-layer printing process, which has great limitations. Document 2 "CN202022707916.4 A polishing and strengthening device for 3D printed models using FDM molding process" fills the printed workpiece with refined salt and heats it to melt the layer patterns on the surface of the workpiece to increase the strength. Similar to Document 1, it belongs to the post-processing link and cannot be strengthened during layer-by-layer printing, which has great limitations. Reference 3 “ANDREUA, KIM S, DITTUS J, et al. Hybrid material extrusion 3D printing to strengthen interlayer adhesion through hot rolling [J]. Additive Manufacturing, 2022, 55: 102773” uses a heated roller to compress the printed graphics during the layer-by-layer printing process to increase the interlayer bonding strength. However, the mechanical structure of this method is complex and the downward pressure of the roller will cause large deformation and damage to the suspended structure, which has great limitations. For example, reference 4 “WU W, LI J, JIANG J, et al. Influence mechanism of ultrasonic vibration substrate on strengthening the mechanical properties of fused deposition modeling [J]. Polymers, 2022, 14 (5): 904” uses ultrasonic vibration to strengthen the interface of the layer-by-layer printed spinneret placement, thereby improving the mechanical properties. Similar to reference 3, it has problems such as complex mechanical structure and damage to complex thin-walled structures, and has great limitations. Summary of the Invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a device and method for efficiently and quickly improving the strength of material extrusion printing workpieces while ensuring mechanical properties.

[0005] The technical solution of the present invention:

[0006] A device for improving the strength of a material extrusion printing workpiece according to the present invention includes a nozzle, the nozzle including a body, a printer consumables molten liquid channel opened in the middle of the body, the inlet of the printer consumables molten liquid channel is connected to the wire feeding outlet of the wire feeding mechanism of the extrusion printer, a spinneret is installed at the outlet of the printer consumables molten liquid channel, and the spinneret is arranged according to a preset spinneret cross-sectional shape; the nozzle is connected to a rotating mechanism, and the nozzle can rotate under the drive of the rotating mechanism, and the printer consumables flowing out of the spinneret can produce a directional deflection around its own axis under the rotation of the nozzle, forming a laid stacking structure according to the set form to increase the contact area between the spinnerets.

[0007] A method for improving the strength of a workpiece printed by extrusion of a material according to the present invention comprises the following steps:

[0008] S1. According to the extrusion material to be printed and the extrusion spinneret shape requirements, prepare the spinneret hole shape and size of the nozzle. The formula is:

[0009] Spinneret hole dimensions S = δS'

[0010] Wherein, S′ is the external dimension of the extruded spinneret;

[0011] δ is the scaling factor considering the barus effect related to the extrusion material;

[0012] S2, connecting the nozzle to the wire feeding mechanism, the rotating output end of the rotating mechanism and the heater respectively;

[0013] S3, connecting the cable of the motor serving as the driving device of the rotating mechanism to the controller of the extrusion printer;

[0014] S4. Cut the end of the printing consumables into a 45° sharp angle and insert it vertically into the cavity of the wire feeding mechanism;

[0015] S5, preheating the nozzle and the printing bed of the extruder;

[0016] S6. Set the wire feeding mechanism parameters;

[0017] S7. Setting motor parameters according to the spinneret placement method so that the printer consumables flowing out of the spinneret can be directional deflected around its own axis under the rotation of the nozzle, forming a stacked structure according to the set shape to increase the contact area between the spinnerets;

[0018] S8. Import the sliced ​​digital model of the printed workpiece into the controller of the extrusion printer, and start the extrusion printer to print until the printing is completed.

[0019] 1. The present invention achieves extruded spinnerets with different cross-sectional shapes by replacing nozzles with spinneret holes of varying cross-sectional shapes and sizes. This method has a simple structure and is easy to operate. The nozzle is driven by a synchronous pulley mechanism to rotate, thereby changing the placement of the spinneret. Spinnerets with altered shapes and forms can achieve a larger contact area between the spinnerets, thereby increasing the bonding strength between the spinnerets and, in turn, the strength of the printed workpiece. Furthermore, the interlocking mechanism between the spinnerets can be formed by the interlocking of the concave and convex structures of the spinneret profile, thereby increasing the strength of the printed workpiece. Therefore, the application areas and scope of material extrusion prints are greatly expanded.

[0020] 2. According to different extrusion materials, the spinneret hole shape and size calculation equation is established to design the spinneret hole dimensions to meet the shape and size requirements of the extruded spinneret under different materials.

[0021] 3. The rotatable nozzle can be controlled on demand, which can realize the twisting and other laying morphological changes of the extruded material spindle. The rotation process can cooperate with the material extrusion printing and laying action to realize the regulation of the spindle laying and stacking morphology, which is conducive to the formation of the interlocking concave and convex structures of the spindle profile, thereby improving the strength of the printed workpiece.

[0022] 4. The present invention is fully applicable to the material extrusion printing process, can realize the enhancement of the mechanical properties of the workpiece during the printing process, is not affected by the complexity of the workpiece structure, has high flexibility, a wide range of applications, and is simple and easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a front view of the overall structure of the device for improving the strength of a workpiece for material extrusion printing according to the present invention;

[0024] Figure 2 This is a cross-sectional view of the overall structure of the device for improving the strength of a workpiece for material extrusion printing according to the present invention;

[0025] Figure 3-1 It is a schematic diagram of the first correspondence between the spinneret hole and the extruded spinneret cross section;

[0026] Figure 3-2 It is a schematic diagram of the second correspondence between the spinneret hole and the extruded spinneret cross section;

[0027] Figure 4-1 is a schematic diagram of the spinneret shape and morphology of the first material extruded using the apparatus and method of the present invention;

[0028] Figure 4-2 is a schematic diagram of the spinneret shape and morphology of the second material extruded using the apparatus and method of the present invention;

[0029] Figure 4-3 is a schematic diagram of the spinneret shape and morphology of a third material extruded using the apparatus and method of the present invention;

[0030] Figure 4-4 is a schematic diagram of the spinneret shape and morphology of a fourth material extruded using the apparatus and method of the present invention;

[0031] Figure 5-1 Schematic diagram of the strengthening principle (first type of laying and stacking) of the method for improving the strength of a workpiece by extruding a material into a printed object according to the present invention;

[0032] Figure 5-2 Schematic diagram of the strengthening principle (second type of laying and stacking) of the method for improving the strength of a workpiece by extruding a material into a printed object according to the present invention;

[0033] Figure 5-3 Schematic diagram of the strengthening principle (third type of laying and stacking) of the method for improving the strength of a workpiece by extruding a material into a printed object according to the present invention;

[0034] Figure 5-4 It is a schematic diagram of the strengthening principle (fourth type of laying and stacking) of the method for improving the strength of material extrusion printing workpieces of the present invention. DETAILED DESCRIPTION

[0035] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. It should be noted that the illustrations provided in this embodiment only illustrate the basic concept of the present invention in a schematic manner. Therefore, the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component can be changed at will, and the component layout type may also be more complicated.

[0036] like Figure 1 -3, the present invention provides a device for improving the strength of a material extrusion printing workpiece, comprising a nozzle, the nozzle comprising a body, a printer consumables melt channel opened in the middle of the body, the inlet of the printer consumables melt channel being connected to the wire feeding outlet of the wire feeding mechanism 13 of the extrusion printer. A spinneret 1001 is installed at the outlet of the printer consumables melt channel, and the spinneret is arranged according to a preset spinneret cross-sectional shape, for example, Figure 3-1 As shown, the spinneret trilobal cross-sectional shape 1002 corresponds to the spinneret trilobal cross-sectional shape 7001. Figure 3-2 As shown, the spinneret hole quadrilobal cross-sectional shape 1003 corresponds to the quadrilobal spinneret cross-sectional shape 7002 .

[0037] The nozzle is connected to a rotating mechanism, and the nozzle can rotate under the drive of the rotating mechanism. The printer consumables flowing out of the spinneret can produce a directional deflection around its own axis under the rotation of the nozzle, forming a laying and stacking structure according to the set shape to increase the contact area between the spinnerets. Figure 4-1 and Figure 4-2 Shown is a non-rotating spinneret configuration. Figure 4-3 and Figure 4-4 They are Figure 4-2 Different rotary spinneret morphologies.

[0038] Preferably, the stacking structure is as follows: in a multi-layer stacking structure, adjacent left and right spinnerets and adjacent top and bottom spinnerets are interlocked with each other in a concave and convex manner to form a staggered interlocking structure. When the extruded spinnerets are laid in the same layer or between layers, there can be a variety of laying methods, such as a same-shape laying structure in the same layer and a different-shape laying structure in the adjacent layer, that is, when the same layer of extruded material is stacked, the nozzle does not rotate, and when the previous layer of extruded material is laid on the next layer of extruded material, the nozzle rotates 120 degrees (or other angles) to control the spinneret laying shape to be different from the next layer, such as Figure 5-1 ; Printing in a way that the adjacent spinnerets in the same layer have different shapes, that is, when the adjacent spinnerets are laid and stacked, the nozzle rotates 120 degrees (or other angles) to control the adjacent spinnerets in the same layer to have different shapes, such as Figure 5-2 ; The same layer and adjacent layers are laid in the same shape, such as Figure 5-3 and Figure 5-4 The laying method is different due to the shape of the spinnerets between adjacent layers or in the same layer, such as Figure 5-1 to Figure 5-4 The "lobate" structural features in the mold can form concave and convex embedding, which not only improves the surface contact rate between spinnerets (reduces the porosity, which can be as low as 1.771%, and reduces the internal voids by 86.7% compared with the traditional circular cross-section (13.322% porosity)), realizes inter-filament bonding, but also forms interlocking and inhibits interlayer separation. This composite mechanism significantly improves the interlayer bonding strength, breaks through the anisotropic bottleneck of traditional printed parts, and achieves improved workpiece strength.

[0039] like Figure 1 、 2 The figure shows a structure of the device of the present invention during actual use. The inlet of the printer consumables melt channel is connected to the wire feed outlet of the wire feed mechanism 13 of the extrusion printer, forming a conveying channel for the printing consumables 7. The extrusion printer can use existing equipment. To melt the wire feed in the printer consumables melt channel, the nozzle is set in the heater 6 to achieve uniform melting of the wire. The support plate 5 is fixed to the bottom wall of the heater body by screws 12 and supported on the throat section at the bottom of the nozzle 1, providing support for the nozzle 1 and heater 6.

[0040] The rotation mechanism can adopt a pulley structure, wherein the driven pulley 3 of the pulley structure is fixedly connected to the nozzle, the driving pulley 9 of the pulley structure is fixedly connected to the rotation output shaft 1101 of the motor 11, and the driving pulley and the driven pulley are connected by a synchronous belt 4. The motor is fixed to the motor bracket 10 by screws 14, and the motor bracket and support plate can be mounted on the support platform. Of course, the rotation mechanism can also adopt an existing gear transmission structure.

[0041] When printing a workpiece, the printing consumable 7 passes through the wire feed mechanism, and the heater 6 heats the nozzle 1, which in turn heats the printing consumable 7 within the nozzle 1, causing the printing consumable 7 to form a printer consumable molten liquid 701. The molten printing consumable 701 is then extruded from the terminal spinneret 1001 to form a spindle. The motor 11 rotates the driving pulley 9, which transmits the motion to the driven pulley 3 via the timing belt 4. The driven pulley 3 is fixed to the nozzle 1 by the set screw 2. Therefore, the driven pulley 3 can drive the nozzle 1 to rotate, achieving a change in the laydown shape of the spindle. During the rotary extrusion process, the extrusion expansion effect, surface tension, and cooling effect work together to ensure that the printing consumable molten liquid 701 maintains the predetermined spinneret cross-sectional shape during solidification.

[0042] The device of the present invention increases the contact area between spinnerets by regulating the spinneret's cross-sectional shape and placement. It also features a reinforcing mechanism that creates a concave and convex structure that interlocks and forms the spinneret's profile. This enhances the mechanical properties of complex extrusion prints, expanding the scope and range of engineering applications for these materials. The device is also easy to operate, offers high reinforcing efficiency, and can achieve reinforcing during the printing process.

[0043] The present invention also proposes a method for improving the strength of a workpiece produced by extrusion printing of a material, comprising the following steps:

[0044] S1. Prepare the spinneret hole shape and size of the nozzle 1 according to the extrusion material to be printed and the extrusion spinneret shape requirements. The formula is:

[0045] Spinneret hole dimensions S = δS'

[0046] Wherein, S′ is the external dimension of the extruded spinneret;

[0047] δ is a scaling factor related to the extrusion material taking into account the Barus effect; preferably 0.9≤δ≤1;

[0048] S2, connecting the nozzle to the wire feeding mechanism, the rotating output end of the rotating mechanism and the heater respectively;

[0049] S3. The cable of the driving device of the rotating mechanism (e.g., motor 11) is connected to the controller of the extrusion printer, such as the fourth axis control port of the multi-axis motion controller of the extrusion printer. If there is no multi-axis control port, the printer is equipped with an external motor controller such as the TMC2209 model.

[0050] S4, cutting the end of the printing consumables 7 into a 45° sharp angle and vertically inserting it into the cavity of the wire feeding mechanism 13;

[0051] S5, preheating the nozzle and the printing bed of the extruder;

[0052] S6. Set the wire feeding mechanism parameters: such as wire feeding speed (wire feeding length per second) 1 to 10 mm / s;

[0053] S7, according to the spinning placement method, set the parameters of the rotating mechanism (motor), such as the same layer with the same shape and the adjacent layer with different shapes ( Figure 5-1 ), when the printer steps one printing layer thickness in the vertical direction, the rotating mechanism (such as the motor 11 driving the pulley structure) drives the nozzle to rotate the set angle (such as 120 degrees). For the same layer and the adjacent layer, the same shape is laid. According to the pitch and wire feeding speed of the rotating shape spray, the speed of the driving device of the rotating mechanism (such as the motor 11) is set according to the following equation:

[0054] n=60v / p

[0055] Where n is the motor speed, unit is r / min

[0056] v is the wire feeding speed, unit is mm / s

[0057] p is the pitch of the rotating spinneret, in mm

[0058] For example, when the pitch is 3 mm and the wire feeding speed is 1 mm / s, the speed of the motor 11 is set to 20 r / min.

[0059] S8. Import the sliced ​​digital model of the printed workpiece into the controller of the extrusion printer, and start the extrusion printer to print until the printing is completed.

[0060] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0061] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations that come within the meaning and range of equivalents of the claims be embraced therein.

[0062] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A device for improving the strength of a material extrusion printing workpiece, comprising a nozzle, the nozzle comprising a body, a printer consumable material melt channel opened in the middle of the body, the inlet of the printer consumable material melt channel being connected to the wire feeding outlet of the wire feeding mechanism (13) of the extrusion printer, characterized in that: A spinneret (1001) is installed at the outlet of the printer consumables melt channel, and the spinneret is set according to a preset spinneret cross-sectional shape; the nozzle is connected to a rotating mechanism, and the nozzle can rotate under the drive of the rotating mechanism. The printer consumables flowing out of the spinneret can produce a directional deflection around its own axis under the rotation of the nozzle, forming a laying and stacking structure according to the set shape to increase the contact area between the spinnerets.

2. The device for improving the strength of a material extrusion printing workpiece according to claim 1, characterized in that: The spinneret hole has a trilobal cross-section or a quadlobal cross-section.

3. The device for improving the strength of a workpiece produced by extrusion printing according to claim 1 or 2, characterized in that: The laying and stacking structure is as follows: in the multi-layer laying and stacking structure, the spinnerets adjacent to each other on the left and right and adjacent to each other on the top and bottom are embedded in a concave-convex manner to form a staggered interlocking structure.

4. The device for improving the strength of a material extrusion printing workpiece according to claim 1 or 2, characterized in that: The nozzle is arranged in the heater.

5. The device for improving the strength of a workpiece produced by extrusion printing according to claim 1 or 2, characterized in that: The driving device of the rotating mechanism adopts an electric motor.

6. A method for improving the strength of a workpiece printed by extrusion of a material, applied to the device for improving the strength of a workpiece printed by extrusion of a material according to claim 5, characterized in that The following steps are involved: S1. According to the extrusion material to be printed and the extrusion spinneret shape requirements, prepare the spinneret hole shape and size of the nozzle. The formula is: Spinneret hole dimensions S = δS' Wherein, S′ is the external dimension of the extruded spinneret; δ is the scaling factor considering the barus effect related to the extrusion material; S2, connecting the nozzle to the wire feeding mechanism, the rotating output end of the rotating mechanism and the heater respectively; S3, connecting the cable of the motor serving as the driving device of the rotating mechanism to the controller of the extrusion printer; S4. Cut the end of the printing consumables into a 45° sharp angle and insert it vertically into the cavity of the wire feeding mechanism; S5, preheating the nozzle and the printing bed of the extruder; S6. Set the wire feeding mechanism parameters; S7. Setting motor parameters according to the spinneret placement method so that the printer consumables flowing out of the spinneret can be directional deflected around its own axis under the rotation of the nozzle, forming a stacked structure according to the set shape to increase the contact area between the spinnerets; S8. Import the sliced ​​digital model of the printed workpiece into the controller of the extrusion printer, and start the extrusion printer to print until the printing is completed.

7. The method for improving the strength of a material extrusion printing workpiece according to claim 6, characterized in that : The scaling factor 0.9≤δ≤1.

8. The method for improving the strength of a material extrusion printing workpiece according to claim 7, characterized in that When setting a same-layer and same-shape laying structure with adjacent layers of different shapes, the motor parameters of step S7 are set as follows: when the extrusion printer steps one printing layer thickness in the vertical direction, the rotating mechanism drives the nozzle to rotate the set angle.

9. The method for improving the strength of a material extrusion printing workpiece according to claim 7, characterized in that When setting up a structure where both the same layer and adjacent layers have the same shape, set the motor speed according to the following equation: n=60v / p Where n is the motor speed, unit is r / min; v is the wire feeding speed, in mm / s; p is the pitch of the rotary spinneret, in mm.

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