Extruder, print head and printing device for enhancing interlayer performance of 3D printed concrete

Abstract

The present invention discloses an extrusion head, a printing head, and a printing device for enhancing the interlayer performance of 3D-printed concrete. The extrusion head includes a base and an extrusion hole disposed on the base. The extrusion hole is characterized in that: the outlet shape of the extrusion hole is a rectangular shape with one concave and one convex on two opposite sides of the rectangle, the concave and convex having the same shape; the concave is composed of a base and two oblique sides symmetrically distributed on either side of the base, the angle between the oblique sides and the base plate is not less than π / 2, the horizontal projection length L3 of the oblique sides is not greater than the width L1 of the base, the depth H1 of the concave is between 1 / 8 and 3 / 4 of the width H2 of the extrusion hole outlet, and the distance L2 from the outlet edge of the extrusion hole to the edge of the concave is not less than the horizontal projection length L3 of the oblique sides JX9 of the concave. The present invention improves the mechanical properties of the interlayers of 3D-printed concrete by extruding specially shaped concrete strips to form a self-locking structure between printed layers.

Description

Technical Field

[0001] The present invention belongs to the field of 3D printing construction technology, and in particular relates to an extruder head, a print head and a printing device. Background Art

[0002] With national development and technological advancements, the construction industry continues to move toward green, lightweight, and efficient approaches. 3D printing concrete technology, considered a game-changer for traditional construction and instrumental in transforming and upgrading the industry, has emerged. This technology significantly shortens construction cycles, reduces labor costs, and is environmentally sustainable. During the 3D printing concrete construction process, the print head largely determines the cross-sectional shape of the strips and the properties between concrete layers, significantly impacting printing efficiency and build quality.

[0003] Currently, existing printhead shapes are mostly circular, rectangular, and triangular. Existing research shows that the shape of the printhead has a significant impact on the interlayer gaps, interlayer adhesion, and mechanical properties of the printed layers. While all three types of printheads have their own characteristics and advantages, the porosity of printed specimens is greater and there are more interlayer weak points compared to cast-in-place specimens. Concrete's mechanical properties are generally directly related to its porosity and defect morphology. Printed products using existing printheads have a high number of interlayer defects, making them unsuitable for concrete printing applications that require high mechanical properties and refinement. Summary of the Invention

[0004] The purpose of the present invention is to provide an extruder head, a print head and a printing device that significantly improve the interlayer performance of 3D printed concrete.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] The present invention first provides an extrusion head, including a base and an extrusion hole arranged on the base, characterized in that the outlet shape of the extrusion hole is a quasi-rectangular shape with one concave and one convex on two opposite sides of the rectangle, and the shapes of the concave and convex are consistent.

[0007] The concave is composed of a base and two oblique sides symmetrically distributed on both sides of the base. The angle between the oblique side and the bottom plate is not less than π / 2, the horizontal projection length L3 of the oblique side is not greater than the width L1 of the base, the depth H1 of the concave is between 1 / 8 and 3 / 4 of the outlet width H2 of the extrusion hole, and the distance L2 from the outlet edge of the extrusion hole to the edge of the concave is not less than the horizontal projection length L3 of the concave oblique side JX9.

[0008] The shape parameters of the extrusion hole outlet are obtained according to the following steps:

[0009] 1) Set the outlet area S 设 , select the angle α between the hypotenuse and the base plate and the aspect ratio k;

[0010] The α value is selected in the angle interval [π / 2, π) according to the following conditions:

[0011]

[0012]

[0013] Where, τ 粘结 is the interlayer shear strength of the 3D printed concrete strips in the stacking direction; σ 粘结 is the interlayer compressive strength of the 3D printed concrete strips in the stacking direction; τ c is the shear strength of 3D printed concrete; σ c The compressive strength of 3D printed concrete;

[0014] The k value is selected in the range of [1 / 8, 3 / 4] according to the relationship between the influence of the change in the length of the concave part and the mechanical properties of the concrete;

[0015] 2) After determining α, k, S 设 After these parameters were calculated, the length-to-width ratio ξ, the size parameter L2 / L1, and the concrete water-cement ratio ω were used as orthogonal test factors for the printing performance of 3D printed concrete. Through orthogonal experiments, the optimization under the influence of multiple factors was carried out to determine the final values ​​of the length-to-width ratio ξ, the size parameter L2 / L1, and the concrete water-cement ratio ω, where ξ = A / H2, A is the length of the extrusion port, and H2 is the width of the extrusion port;

[0016] 3) According to the final value of the aspect ratio ξ determined in step 2) and the outlet area S set in step 1) 设 , get the final values ​​of the extrusion port length A and the extrusion port width H2;

[0017] 4) Based on the final value of the extrusion port width H2 obtained in step 3) and the α and k selected in step 1), the parameter b is determined according to the following formula:

[0018] k= b sin(π-α) / H2;

[0019] 5) According to the parameter b obtained in step 4) and the α selected in step 1), the horizontal projection length L3 of the hypotenuse and the depth H1 of the concave are obtained;

[0020] 6) According to the extrusion port length A obtained in step 3), the final value of the dimensional parameter L2 / L1 determined in step 2), and L3 obtained in step 5), the final bottom edge width L1 and the distance L2 from the outlet edge of the extrusion hole to the concave edge are obtained.

[0021] The present invention also provides a print head, comprising an inner print head shell and an outer print head shell, wherein the inner print head shell is connected to the outer print head shell, and is characterized in that the lower portion of the outer print head shell is the extrusion head described above.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The extruder's outlet is shaped like a rectangle with concave and convex edges. This creates a self-locking concrete strip between printed layers, improving the bending and tensile properties of the 3D-printed concrete. The outlet shape can be designed based on the actual structure dimensions and the mechanical properties of the material to ensure print performance for structures of varying sizes. The extruder is quick and easy to manufacture, and it connects to 3D printing equipment via threads. Its rational design offers flexible variations, a wide range of sizes, and easy assembly, making it suitable for a variety of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of the extrusion head of the present invention from a first angle;

[0025] Figure 2 This is a schematic diagram of the extrusion head of the present invention from a second angle;

[0026] Figure 3 A top view of the extrusion head of the present invention;

[0027] Figure 4 This is a diagram showing the shape of the lower outlet of the extrusion head of the present invention;

[0028] Figure 5 This is a schematic diagram of the design of the lower outlet size of the extrusion head of the present invention;

[0029] Figure 6 This is an overall schematic diagram of the print head of the present invention;

[0030] Figure 7 for Figure 6 Schematic cross-sectional view of ;

[0031] Figure 8 for Figure 6 Schematic elevation diagram;

[0032] Figure 9 It is a plan (top view) schematic diagram of the present invention;

[0033] Figure 10 It is a plan (bottom-up) schematic diagram of the present invention;

[0034] Figure 11 It is a schematic diagram of the stacking and axial direction of concrete strips;

[0035] Explanation of the accompanying symbols: 1. Print head inner shell, 2. Extrusion head, 3. Print head outer shell, 4. Elastic cushion, 5. First movable baffle, 6. Second movable baffle, 7. Buckle, 8. Gear transmission device, 9. Gear, 10. Slide rail, 11. Electromagnetic adsorption device, 12. Threaded interface. DETAILED DESCRIPTION

[0036] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. The described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0037] Example 1

[0038] The present invention provides an extrusion head for enhancing the interlayer performance of 3D printed concrete, the structure of which is as follows: Figure 1-Figure 3 As shown, it includes a base 21 and an extrusion hole 22 located in the base 21. The outlet shape of the extrusion hole 22 is a rectangular shape with one side having an inner concave and the other having an outer convex on two opposite sides of the rectangle. Figure 4 The four sides of the rectangle are JX1, JX2, JX7, and JX8. JX and JX6 are on the same line and together form a side of the rectangle. JX8 and JX12 are on the same line and together form a side of the rectangle. Sides JX9, JX10, and JX11 form a concave shape, while sides JX3, JX4, and JX5 form a convex shape. Sides JX1 and JX7 are parallel, and side JX8 is parallel to side JX2. The lengths of the sides satisfy JX1 = JX7, JX8 = JX6, JX9 = JX5, JX10 = JX4, JX11 = JX3, and JX12 = JX2.

[0039] The angle between sides JX8 and JX9 is the upper angle α, and the angle between sides JX9 and JX10 is the lower angle β. Both the upper angle α and the lower angle β are not less than π / 2; the depth H1 of the concave is between 1 / 8 and 3 / 4 of the extrusion port width H2; the distance L2 from the edge of the extrusion port to the edge of the concave is not greater than the horizontal projection length L3 of the concave oblique side JX9; the horizontal projection length of the concave oblique side JX9 is not less than the width L1 of the concave bottom side JX10.

[0040] The dimensions of the extrusion head outlet shape of the present invention are designed as follows: the upper corner α, the lower corner β, the depth H1 of the concave, the distance L2 from the edge of the extrusion outlet to the edge of the concave, the horizontal projection length L3 of the concave hypotenuse, the width L1 of the concave bottom edge, and the width H2 of the extrusion outlet are as follows, with reference to Figure 5 :

[0041] 1) Concrete strength τ c , σ c 、F设x 、F 设Y 、F 设Z ; Interlayer bonding strength value τ between stripes 粘结 , σ 粘结 It can be measured by axial compression and splitting tests. The mechanical properties of early concrete can be determined by direct shear tests and unconfined uniaxial compression tests. α∈[π / 2,π), where the depth-to-width ratio is k, k=b sin(π-θ) / B, and k∈[1 / 8,3 / 4]. When calculating, the bond surface between the upper and lower strips is considered as a bond surface with a thickness approaching 0. The bond surface stress and bond surface area are considered separately in the calculation. Since the bond surface between strips in the same layer does not change, it is incorporated into the concrete compressive stress σ in the calculation of the axial compressive mechanical properties in the X, Y, and Z directions. c ×A c unified processing;

[0042] 2) According to the target mechanical properties and anisotropy requirements of the printing material, α = 120° is taken in the angle range [π / 2, π) according to the following formula;

[0043]

[0044]

[0045] Where, τ 粘结 is the interlayer shear strength of the 3D printed concrete strips in the stacking direction; σ 粘结 is the interlayer compressive strength of the 3D printed concrete strips in the stacking direction; τ c is the shear strength of 3D printed concrete; σ c The compressive strength of 3D printed concrete;

[0046] 3) Referring to the study of Zareiyan et al. in Effects of interlocking on interlayer adhesion and strength of structures in 3D printing of concrete, based on the relationship between the effect of the change in the length of the concave part on the mechanical properties of concrete, a k value that can significantly improve the mechanical properties is selected as the design value. In this embodiment, k = 1 / 4 is selected as the design value;

[0047] 4) Extrusion outlet area S 设 Pre-set, S 设 =A H2, take S 设 =312.12mm 2 ;

[0048] 5) After determining θ, k, S 设 After these parameters are calculated, the length-width ratio ξ, the size parameter L2 / L1, and the concrete water-cement ratio ω are used as orthogonal test factors for 3D printing concrete printing performance. Through orthogonal test, the optimization under the influence of multiple factors is carried out to determine the specific values ​​of the length-width ratio ξ, the size parameter L2 / L1, and the concrete water-cement ratio ω. 设 =A H2 to determine the extrusion port length A and width H2 of the printhead designed in this invention; b is calculated from b = kH2 / sin(π - α). Based on strip molding tests during extrusion, the difference between L2 and L1 should not exceed 10%. During design and production, each parameter can be rounded off to two decimal places based on actual processing accuracy capabilities.

[0049] In the orthogonal test of 3D printing concrete printing performance, a continuous printing method was adopted to print concrete strips using a 3D printer. Each time, a strip with a length of 400 mm was printed. A vernier caliper with an accuracy of 0.01 mm was used to measure the width of the strip at three positions. The width values ​​W1, W2, and W3 were obtained, and the average value W was taken. avg The strip width test result is the change in the width of the printed strip, δ, δ = W avg -A is used as an evaluation index for strip forming quality. The testers visually observed the strip surface quality, with a continuous and smooth surface being considered excellent; a relatively continuous and smooth surface with occasional cracks and particles being considered good; and a surface with numerous cracks, particles, or even tears or breaks being considered poor. The strip surface quality was used as an auxiliary reference index. The orthogonal experimental design and results are shown in the table below:

[0050] Table 1. Orthogonal test factor levels for 3D printed concrete printing performance

[0051]

[0052] Table 2 Orthogonal test results of 3D printed concrete printing performance

[0053]

[0054]

[0055] k1, k2, and k3 are average values, and R is the range. The magnitude of the R value reflects the order of significance of the factors in this test: B > A > C. Taking into account the evaluation index δ and the surface quality of the strip during testing, according to the orthogonal test results table, the optimal solution is A2 B2 C3 (Test No. 5). To facilitate processing design, L2 = L1 = 5.53 mm.

[0056] The final parameter values ​​are α=120°, k=1 / 4, S 设=312.12mm 2 , ξ=4 / 3, A=20.4mm, H2=15.3mm, b=4.47mm, L2=L1=5.53mm, ω=0.35.

[0057] In one embodiment, the rectangular extrusion hole 22 is formed by 12 inclined planes, each with a slope i (slope tangent) ∈ (0, 0.36). The bottom of the 12 inclined planes forms the rectangular exit of the extrusion hole 22. The 12 inclined planes are arranged in the order XM1-XM12 shown in the figure. The upper portions of the 12 inclined planes form the entrance of the extrusion hole 22, with the entrance cross-section of the extrusion hole 22 being larger than the exit cross-section. The extrusion hole formed by the 12 inclined planes allows the concrete to be pre-formed within the extrusion head, ensuring good extrusion printing quality.

[0058] In one embodiment, the twelve inclined surfaces are laser processed to form a three-dimensional micro-texture.

[0059] Example 2

[0060] This embodiment provides a print head for enhancing the interlayer performance of 3D printed concrete, including a print head inner shell 1, an extrusion head 2, a print head outer shell 3, an elastic cushion layer 4, a first movable baffle 5, a second movable baffle 6, a buckle 7, a gear transmission device 8, a gear 9, a slide rail 10 and an electromagnetic adsorption device 11. The upper end of the print head inner shell 1 is internally provided with a threaded interface 12. The print head inner shell 1 is connected to the upper printer through a threaded interface 12. The inner wall diameter of the print head inner shell 1 and the outer wall diameter of the 3D printer outlet to which it is connected should not differ by more than 2%, and the thread size is consistent to ensure that the connection between the two is firm and reliable; the extrusion head 2 is the extrusion head in Example 1, and the extrusion hole of the extrusion head 2 is composed of an inclined surface, and the inclined surface is laser-processed to form a three-dimensional micro-texture, so that the concrete extrusion is smooth; the motor inside the gear transmission device 8 drives the gear 9 to rotate, and the gear teeth on the print head outer shell 3 serve as the driven wheel. Driven by the gear 9, the print head outer shell 3 is rotated along the slide rail 10 to adjust the outlet direction of the extrusion head 2 connected to the print head outer shell 3. After adjusting to the target position, the electromagnetic adsorption device 11 is connected to fix the print head inner shell 1 and the print head outer shell 3 to prevent separation and detachment under the action of extrusion pressure and material gravity during printing. , and then continue printing, so that the print head can extrude concrete strips of special shapes in all directions according to the design; the upper surface of the elastic cushion layer 4 is flush with the upper edge of the print head housing 3, preventing external debris from entering the slide rail, reducing the extrusion of the inner and outer walls caused by temperature and external forces; the first movable baffle 5 and the second movable baffle 6 are controlled by a motor and can rotate freely, and are fixed by a buckle 7; when the first movable baffle 5 is rotated to the plane of the extrusion port, the edge of the first movable baffle 5 coincides with the edge JX6, and the lower surface of the extruded strip becomes a plane for printing the bottom layer of concrete; when the second movable baffle 6 is rotated to the plane of the extrusion port, the edge of the second movable baffle 6 coincides with the concave bottom edge JX10, and the upper surface of the extruded strip becomes a plane for printing the top layer of concrete; when both movable baffles are fixed at the plane of the extrusion port, they can be used as a rectangular print head for printing.

[0061] The extrusion head 2 and the print head housing 3 are Figure 7 In the embodiment, the print head housing 3 is integrally formed, i.e., a rectangular extrusion hole is provided at the bottom of the print head housing 3, thereby forming the extrusion head 2 at the bottom of the print head housing 3. The extrusion head 2 and the print head housing 3 may also be two detachable components, with the extrusion head 2 fixed to the bottom of the print head housing 3, thereby making the extrusion head 2 replaceable.

[0062] Experiments have shown that the present invention utilizes the inner concave and outer convex portions provided at the extrusion outlet to enable the printed strips to achieve a self-locking structure between layers, thereby improving the interlayer performance of 3D printed concrete and enhancing the bearing capacity of the printed structure.

[0063] In this example, the model object dimensions are 150 mm long, 150 mm wide, and 150 mm high, printed continuously and uniformly. During printing, baffles are adjusted to print the top and bottom layers of concrete, while baffles are not used during the middle portion of the print. This ensures that the concrete is neatly stacked and the top and bottom are flat, improving interlayer performance and enhancing load-bearing capacity.

[0064] The comparison and analysis of theoretical calculation and experimental results in this embodiment are as follows:

[0065] The relevant dimensions of the print head of the present invention are: α = 120°, k = 1 / 4, S 设 =312.12mm 2 ,ξ=4 / 3、A=20.4mm、H2=15.3mm,b=4.47mm、L2=L1=5.53mm、ω=0.35。With the cross-sectional size of 15×20(A=300mm 2 ) are compared with a square print head, and the cross-sectional areas of the print heads are close (difference of 4.04%).

[0066] ① X-axis compressive properties:

[0067] The bearing capacity of 3D printed concrete in the X direction is F x

[0068] F x =F 粘结 +F c =τ 粘结 ×A 粘结 +σ c ×A c

[0069] When the print head designed by the present invention is used, the change in bonding area is recorded as ΔA. 粘结 , the concrete compression area is recorded as ΔA c , and the two are calculated as follows:

[0070] ΔA 粘结 =Σ(2a i +2b i +c i )L i -A i L i =Σ2b i L i [1-cos(π-α i )], ΔA c Approaching 0,

[0071] Simplified:

[0072] The change in bearing capacity in the X direction is:

[0073] ΔFx =τ 粘结 ×ΔA 粘结 =τ 粘结 ×2ΣLi b[1-cos(π-α)]

[0074] ②Y-axis compressive properties:

[0075] The bearing capacity of 3D printed concrete in the Y direction is F Y , F of conventional print head Y常 As shown in formula I, the print head F designed by the present invention Y设 As shown in formula II;

[0076]

[0077] Formula II - Formula I: ΔF Y =τ c A τ +σ c A N -τ 粘结 ΔA 粘结 Substitute and simplify:

[0078] The change in bearing capacity in the Y direction is:

[0079] ΔF Y =ΣLi{τ c bcos(π-α)+σ c bsin(π-α)-τ 粘结 [A-(2L2+L1)]}

[0080] ③Z-axis compressive properties:

[0081] The bearing capacity of 3D printed concrete in the Z direction is F Z , F of conventional print head Z常 As shown in formula III, the print head F designed by the present invention Z设 As shown in formula IV;

[0082]

[0083] Formula IV - Formula III gives: ΔF Z =τ c A τ +σ c A N -σ 粘结 ΔA 粘结 Substitute and simplify:

[0084] The change in bearing capacity in the Z direction is:

[0085] ΔF Z =ΣLi{2τ cbsin(π-α)+2σ c bcos(π-α)-σ 粘结 [A-(2L2+L1)]}

[0086] Substitute the calculated growth amount X 计 =6.11MPa, Y 计 =10.7MPa, Z 计 =8.85MPa, the test measured the growth of X 测 =3.3MPa, Y 测 =7.3MPa, Z 测 =6.2MPa.

[0087] In summary, it can be concluded that the print head designed in the present invention can achieve enhanced mechanical properties.

[0088] Example 3

[0089] This embodiment provides a printing device for enhancing the interlayer performance of 3D printed concrete. The printing device uses the print head of Example 2 to complete the printing of 3D printed concrete.

[0090] It should be noted that the relevant printing parameters of the printing device in this embodiment are set according to the requirements of the relevant printing device. Any implementation methods not shown or described in the drawings or the main text of the specification are known to those skilled in the art and are not described in detail. In addition, the above definitions of the various components and methods are not limited to the various specific structures, shapes, or methods mentioned in the embodiments. Those skilled in the art may make simple modifications or substitutions. For example:

[0091] (1) The movable baffle can also be fixed and rotated in other ways;

[0092] (2) The above-mentioned print head can be manufactured using other manufacturing processes;

[0093] (3) The outer contour of the print head body can be a square, a triangle, etc.

[0094] (4) The connection between the print head and the printing device may also be achieved by bolt connection, fixed connection or other types of connection;

[0095] (5) The above-mentioned cement-based materials may also use other materials such as gypsum, clay, geopolymers, etc.;

[0096] (6) This document may provide examples of parameters containing specific values, but these parameters do not need to be exactly equal to the corresponding values, but can be approximated to the corresponding values ​​within acceptable error tolerances or design constraints.

Claims

1. An extrusion head for enhancing interlayer performance of 3D printed concrete, comprising a base and an extrusion hole provided on the base, characterized in that: The outlet shape of the extrusion hole is a rectangular shape with one concave and one convex on two opposite sides of the rectangle, and the shapes of the concave and convex are consistent; The concave portion is composed of a base and two oblique sides symmetrically distributed on both sides of the base. The angle between the oblique sides and the bottom plate is not less than π / 2. The horizontal projection length L3 of the oblique sides is not greater than the width L1 of the base. The depth H1 of the concave portion is between 1 / 8 and 3 / 4 of the width H2 of the outlet of the extrusion hole. The distance L2 from the outlet edge of the extrusion hole to the edge of the concave portion is not less than the horizontal projection length L3 of the oblique sides of the concave portion. The shape parameters of the extrusion hole outlet are obtained according to the following steps: 1) Set the outlet area S 设 , select the angle α between the hypotenuse and the base plate and the aspect ratio k; The α value is selected in the angle interval [π / 2, π) according to the following conditions; (a) (b) Where, τ 粘结 is the interlayer shear strength of the 3D printed concrete strips in the stacking direction; σ 粘结 is the interlayer compressive strength of the 3D printed concrete strips in the stacking direction; τ c is the shear strength of 3D printed concrete; σ c The compressive strength of 3D printed concrete; The k value is selected in the range of [1 / 8, 3 / 4] according to the relationship between the influence of the change in the length of the concave part and the mechanical properties of the concrete; 2) After determining α, k, S 设 After these parameters were calculated, the length-to-width ratio ξ, the size parameter L2 / L1, and the concrete water-cement ratio ω were used as orthogonal test factors for the printing performance of 3D printed concrete. Through orthogonal experiments, the optimization under the influence of multiple factors was carried out to determine the final values ​​of the length-to-width ratio ξ, the size parameter L2 / L1, and the concrete water-cement ratio ω, where ξ=A / H2, A is the length of the extrusion port, and H2 is the width of the extrusion port; 3) Based on the final value of the aspect ratio ξ determined in step 2) and the outlet area S set in step 1) 设 , get the final values ​​of the extrusion port length A and the extrusion port width H2; 4) Based on the final value of the extrusion width H2 obtained in step 3) and the α and k selected in step 1), determine the parameter b according to the following formula: k = b sin (π-α) / H2; 5) According to the parameter b obtained in step 4) and the α selected in step 1), the horizontal projection length L3 of the hypotenuse and the depth H1 of the concave are obtained; 6) Based on the extrusion port length A obtained in step 3), the final value of the dimension parameter L2 / L1 determined in step 2), and L3 obtained in step 5), the final bottom edge width L1 and the distance L2 from the outlet edge of the extrusion hole to the concave edge are obtained.

2. The extrusion head according to claim 1, characterized in that: The rectangular extrusion hole is formed by 12 inclined planes, and the slope of the inclined plane is i∈(0, 0.36]; the bottom of the 12 inclined planes forms a rectangular outlet shape of the extrusion hole, and the upper part of the 12 inclined planes forms an inlet shape of the extrusion hole, and the inlet cross-section of the extrusion hole is larger than the outlet cross-section.

3. The extrusion head according to claim 2, wherein: The 12 inclined surfaces are laser processed to form a three-dimensional micro-texture.

4. A print head for enhancing interlayer performance of 3D printed concrete, comprising an inner shell and an outer shell connected to the inner shell, characterized in that: The lower part of the print head housing is the extrusion head described in any one of claims 1-3.

5. A print head according to claim 4, characterized in that: A first movable baffle and a second movable baffle are provided at the lower end of the print head housing; when the first movable baffle is rotated to the extrusion port plane, the edge of the first movable baffle is flush with the convex rectangular edge; when the second movable baffle is rotated to the extrusion port plane, the edge of the second movable baffle is flush with the concave bottom edge.

6. A print head according to claim 4, characterized in that: The print head housing is provided with a print head housing gear for connecting with a transmission mechanism; the print head housing is rotated relative to the print head inner housing by the rotation of the print head housing gear.

7. A print head according to claim 4, characterized in that: An electromagnetic adsorption device is further provided between the print head inner shell and the print head outer shell: the electromagnetic adsorption device is used to fix the print head inner shell and the print head outer shell when they are connected.

8. A printing device for enhancing the interlayer performance of 3D printed concrete, characterized in that: Use the print head described in any one of claims 4 to 7.

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