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Title:
A METHOD OF CONSTRUCTING A LAYERED STRUCTURE AND APPARATUS THEREFOR
Document Type and Number:
WIPO Patent Application WO/2017/111708
Kind Code:
A1
Abstract:
This invention discloses a method of constructing a layered structure comprising the steps of receiving the physical data of the object to be modeled; providing a data set of at least one predefined voxel shape; generating a geometric representation corresponding to the said physical data using the selected voxel shape; providing a chamber filled with a non-flowable material and a print head means connected with the said chamber having at least one nozzle; dispensing a plurality of drops of the non-flowable material on a periodic basis directed vertically downward to a target surface underneath in a layerwise fashion; and repeating said dispensing to form a layered structure, wherein the step of generating a plurality of drops comprises the step of configuring the position of the nozzle such that, with reference to the position of the earlier drop, the subsequent drop has a predetermined horizontal distance displacement whereby allowing voxels formed by the earlier drop and the subsequent drop be arranged in an overlapping manner; and wherein a compression between a partially formed voxel created by an earlier drop and a subsequent drop causes the sacrifice of at least some volume of voxel and fusion of the material at the points of compression thereby forming a fused zone, and wherein at least one part of said voxel is partially protected from compression thereby providing strength to the cured structure and forming a non-compressed zone.

Inventors:
PRASITTISOPIN LAPYOTE (TH)
PONGPAISNSEREE KITTISAK (TH)
SNGUANYAT CHALERMWUT (TH)
DINI ENRICO (IT)
TAWEEKARN NAPHAT (TH)
Application Number:
PCT/TH2015/000096
Publication Date:
June 29, 2017
Filing Date:
December 24, 2015
Export Citation:
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Assignee:
SCG CEMENT CO LTD (TH)
International Classes:
B29C67/00; B28B1/00; B33Y10/00
Foreign References:
EP2189272A22010-05-26
US6146567A2000-11-14
US20060071367A12006-04-06
CA2015000080W2015-02-11
US20150014726W2015-02-06
Attorney, Agent or Firm:
KRAIRIT, Poondej (9Th Floor Rama IV Road,Suriyawongse, Bangrak, Bangkok, TH)
Download PDF:
Claims:
CLAIMS

A method of constructing a layered structure comprising the steps of Receiving the physical data of the object to be modeled Providing a data set of at least one predefined voxel shape

Generating a geometric representation corresponding to the said physical data using the selected voxel shape

Providing a chamber filled with a non-flowable material and a print head means connected with the said chamber having at least one nozzle

Dispensing a plurality of drops of the non-flowable material on a periodic basis directed vertically downward to a target surface underneath in a layerwise fashion

Repeating said dispensing to form a layered structure wherein the step of generating a plurality of drops comprises the step of configuring the position of the nozzle such that, with reference to the position of the earlier drop, the subsequent drop has a predetermined horizontal distance displacement whereby allowing voxels formed by the earlier drop and the subsequent drop be arranged in an overlapping manner, and; wherein a compression between a partially formed voxel created by an earlier drop and a subsequent drop causes the sacrifice of at least some volume of voxel and fusion of the material at the points of compression thereby forming a fused zone, and wherein at least one part of said voxel is partially protected from compression thereby providing strength to the cured structure and forming a non-compressed zone.

A method of constructing a layered structure as cited in Claim 1 wherein for each predefined voxel shape, each has a predefined instruction for processing the matching physical data of the object to be modeled.

A method of constructing a layered structure as cited in Claim 2 wherein the step of generating a geometric representation corresponding to the said physical data using the selected voxel shape comprises the selection of a specific shape of voxel from a set of predefined shapes corresponding to the physical data of the object to be modeled.

4. A method of constructing a layered structure as cited in any of the aforementioned claims wherein each voxel has a horizontal surface in the shape of a square, pentagon, circle, or hexagon.

5. A method of constructing a layered structure as cited in any of the aforementioned claims wherein the displacement is configured such that the overlapped horizontal surface area of voxels in different layers is in the range of 1 : 10 to 3:4.

6. A method of constructing a layered structure as cited in Claim 1 wherein the periodic basis is defined based on the property of the material and adjustable by the user.

7. A method of constructing a layered structure as cited in Claim 6 wherein the time before printing the upper layer is calculated from the total height, height of each layer, compressed height of each layer, and speed of a vertical movement of a print head

8. A method of constructing a layered structure as cited in Claim 7 wherein the said time is expressed as

T = f (D / n(y) Sy)

Whereby D = height; n = height of each layer; y = a ratio between the compressed height and the height of voxel; Sy = vertical movement of a print head

9. An apparatus for the layered construction comprising A chamber filled with a non-flowable material;

A print head means connected with the said chamber having at least one nozzle and configured to receive said non-flowable material from the chamber and generate a plurality of drops of the non-flowable material on a periodic basis directed substantially downward to a target surface underneath in a layerwise fashion;

A controller, being a drop forming mechanism, connected to said print head means and adapted to configure the position of the nozzle and the shape of drop generated from said nozzle; wherein the said controller comprises a data receiving means for receiving the physical data of the object to be modeled, a memory unit comprising a data set of at least one predefined voxel shape, and a translation mechanism connected with said data receiving means and said memory unit and configured to select a voxel shape and generate a geometric representation corresponding to the said physical data using the selected voxel shape; and wherein the said controller adapted to configure the position of nozzle such that, with reference to the position of the earlier drop, the subsequent drop has a predetermined horizontal distance displacement whereby allowing voxels formed by the earlier drop and the subsequent drop be arranged in an overlapping manner; and wherein a compression between a partially formed voxel created by an earlier drop and a subsequent drop causes the sacrifice of at least some volume of voxel and fusion of the material at the points of compression thereby forming a fused zone, and wherein at least one part of said voxel is partially protected from compression thereby providing strength to the cured structure and forming a non-compressed zone.

10. An apparatus for the layered construction as cited in Claim 9 wherein the memory unit contains a plurality of datasets of predefined voxel shapes, each having a predefined instruction for processing the matching physical data of the object to be modeled.

1 1. An apparatus for the layered construction as cited in Claim 10 wherein the controller

comprises the second translation mechanism configured to select a specific shape of voxel from a set of predefined shapes corresponding to the physical data of the object to be modeled.

12. An apparatus for the layered construction as cited in any of the claims 9 to 1 1 wherein each voxel has a horizontal surface in the shape of a square, pentagon, circle or hexagon.

13. An apparatus for the layered construction as cited in any of the claims 9 to 12 wherein the displacement is configured such that the overlapped horizontal surface area of voxels in different layers is in the range of 1 : 10 to 3:4.

14. An apparatus for the layered construction as cited in Claim 9 wherein the periodic basis is defined based on the property of the material and adjustable by the user.

15. An apparatus for the layered construction as cited in Claim 14 wherein the time before printing the upper layer is calculated from the total height, height of each layer, compressed height of each layer, and speed of the vertical movement of a print head.

16. An apparatus for the layered construction as cited in Claim 15 wherein the said time is expressed as

T = f (D / n(y) Sy)

Whereby D = height; n = height of each layer; y = a ratio between the compressed height and the height of voxel; Sy = vertical movement of a print head

17. An apparatus for the layered construction as cited in Claim 9 wherein the nozzle is

positioned at a predefined height above the top surface of the layered structure.

18. An apparatus for the layered construction as cited in Claim 17 wherein the nozzle is moved to an upper position after construction of each layer whereby maintaining the predefined height between the nozzle and the top surface of the layered structure.

19. An apparatus for the layered construction as cited in Claims 9, 17, or 18 wherein the

apparatus comprises a plurality of nozzles.

20. An apparatus for the layered construction as cited in Claim 19 wherein the nozzles are

arranged in a row.

21. An apparatus for the layered construction as cited in Claim 20 wherein a plurality of nozzles arranged in a row are configured to print voxels of material concurrently.

22. An apparatus for the layered construction as cited in Claim 9 wherein the print head means further comprise a mould for forming a drop shape before dispensing and an air pump adapted to pump air for pushing the material from the mould.

AMENDED CLAIMS

received by the International Bureau on 21 April 2017 (21.04.2017)

A method of constructing a layered structure, the method comprising the steps of:

receiving, by a user input system, a set of physical data of an object to be modeled from at least one user;

providing, by a memory unit, the received data set of at least one predefined voxel shape;

generating, by a data processing unit, a geometric representation corresponding to the said physical data using the selected voxel shape by a data processing unit;

providing a chamber filled with a non-flowable material, and a print head means connected with the said chamber having at least one nozzle;

dispensing via the nozzle of the print head based on a input from one or more controllers, a plurality of drops of the non-flowable material on a time periodic basis directed vertically downward to a target surface underneath in a layerwise fashion, and repeating the step of said dispensing process to form a layered structure, said nozzle is moved to an upper position after construction of each layer whereby maintaining the predefined height between the nozzle and the top surface of the layered structure, wherein the time before printing the upper layer is calculated from a total height, a height of each layer, a compressed height of each layer, and a speed of a vertical movement of a print head, and the said time is expressed as,

T= f(D/n(y) Sy)

whereby D = height; n=height of each layer; y=a ratio between the compressed height and the height of voxel; Sy=vertical movement of a print head, wherein the step of generating plurality of drops comprises:

configuring the position of the nozzle with reference to the position of the earlier drop, i\ subsequent drop comprises a predetermined horizontal distance displacement whereby allowing voxels formed by the earlier drop and the subsequent drop arranged in an overlapping manner, and

creating the compression between a partially formed voxel by an earlier drop and a subsequent drop thereby causing the sacrifice of at least some volume of the voxel, and fusion of the material at the points of compression forming a fused zone, and wherein ai: least one part of said voxel is partially protected from compression thereby providing strength to a cured structure and forming a non-compressed zone.

2. The method of claim 1, wherein the each dataset of the predefined voxel shape is provided with a predefined instruction for processing the matching physical data of the object t :> be modeled.

3. The method of claim 1, wherein the step of generating a geometric representation corresponding to the said physical data using the selected voxel shape comprises the selection of a specific shape of voxel from a set of predefined shapes corresponding to the physical data of the object to be modeled.

4. The method of claim 1, wherein each voxel comprises a horizontal surface in the shape of a square, pentagon, circle, or hexagon.

5. The method of claim 1 , wherein the displacement is configured to form overlapped horizontal surface area of voxels in different layers ranging from 1 :10 to 3:4.

6. The method of claim 1, wherein the time periodic basis is based on the property of the material.

7. An apparatus for the layered construction, the apparatus comprising:

a chamber filled with a non-flowable material;

a print head means connected with the said chamber having at least one nozzle, configured to receive said non-flowable material from the chamber and generate a plurality of drops of the non- flowable material on a time periodic basis directed substantially downward to a target surface underneath in a layerwise fashion, wherein the time before printing the upper layer is calculated from the total height, height of each layer, compressed height of each layer, and speed of a vertical movement of a print head, and the said time is expressed as,

T= f(D/n(y) Sy)

whereby D = height; n=height of each layer; y=a ratio between the compressed height and the height of voxel; Sy=vertical movement of a print head;

a controller connected to said print head means and adapted to configure the position of the nozzle and shape of drop generated from said nozzle, said nozzle is moved to an upper position after construction of each layer whereby maintaining the predefined height between the nozzle and the top surface of the layered structure;

wherein the said controller comprises a data receiving the physical data of the object to be modeled, a memory unit comprising a data set of at least one predefined voxel shape, and a translation mechanism connected with said data receiving means and said memory unit, configured to select a voxel shape and generate a geometric representation corresponding to the said physical data using the selected voxel shape; and

wherein the said controller adapted to configure the position of nozzle with reference to the position of the earlier drop, the subsequent drop comprises a predetermined horizontal distance displacement whereby allowing voxels formed by the earlier drop and the subsequent drop arranged in an overlapping manner, and create a compression between a partially formed voxel by an earlier drop and a subsequent drop thereby causing the sacrifice of at least some volume c f the voxel, and fusion of the material at the points of compression forming a fused zone, and wherein at least one part of said voxel is partially protected from compression thereby providin;;; strength to a cured structure and forming a non-compressed zone.

8. The apparatus of claim 7, wherein the memory unit comprises a plurality of datasets of predefined voxel shapes, and each dataset having a predefined instruction for processing the matching physical data of the object to be modeled.

9. The apparatus of claim 7, wherein the controller comprises a second translation mechanism configured to select a specific shape of voxel from a set of predefined shapes corresponding to the physical data of the object to be modeled.

10. The apparatus of claim 7, wherein each voxel comprises a horizontal surface in the shape of a square, pentagon, circle or hexagon.

11. The apparatus of claim 7, wherein the displacement is configured to form overlapped horizontal surface area of voxels in different layers ranging from 1 :10 to 3:4.

12. The apparatus of claim 7, wherein the time periodic basis is based on the property of thi material.

13. The apparatus of claim 7, wherein the plurality of nozzles is positioned at a predefined height above the top surface of the layered structure.

14. The apparatus of claim 7, wherein the plurality of nozzles arranged in a row are configured to print voxels of material concurrently.

15. The apparatus of claim 7, wherein the print head means further comprises a mould for forming a drop shape before dispensing, and an air pump adapted to pump air for pushing the material from the mould.

Description:
A METHOD OF CONSTRUCTING A LAYERED STRUCTURE AND APPARATUS THEREFOR

FIELD OF INVENTION The present invention relates generally to the file of three-dimensional printing, and more particularly to a method of constructing a layered structure and apparatus.

BACKGROUND

The techniques of three-dimensional printing have been disclosed and known in various industries for some time. Such techniques are different according to the application and the material used for printing. In the construction industry, the structures are generally constructed layer by layer using different printing techniques with the primary aim of obtaining a structure having a sufficient strength with a faster construction. These techniques are also expected to bring other advantages including accurate construction and reduced labor cost. Generally, in the construction industry, particularly for large-scale construction, the primary techniques at present are based on the principle of having a custom extrusion head that moves along predetermined routes thereby forming a series of layers of the required structure which is known as a continuous extrusion. These include the disclosure such as in the International Application No.

PCT/CA2015/000080 concerning multi-material extruder and extrusion method for three- dimensional printing.

Different techniques are also known. These include the manufacture of three-dimensional objects wherein a build platform descends as a three dimensional object is progressively built upward in a direction away from the build platform which is known as "right-side up" and the opposite approach known as the "upside down" process wherein a build platform is suspended upside down and progressively moves upward as the three-dimensional object is progressively built in a downward direction. The example of which includes the disclosure according to the

International Application No. PCT/US2015/014726. However, these prior arts do not teach or disclose the factors influencing strength and the correlation between them. It can be seen that such factors and correlations thereof are not obvious and therefore the different techniques according to the prior arts lead to the results that are vastly different in terms of the strength, speed, necessary procedure, and materials. It is thus difficult to find a common ground that can be adopted and regarded as a standard in the industry. Consequently, the benefits and advantages that can be expected from the utilization of this technology have not been clearly seen and the balance between the times required in the construction and the strength necessary to ensure safety still needs to be further explored.

SUMMARY OF THE INVENTION

Therefore, one of the objectives of this invention is to present a method that can ensure the achievement of the reasonable benefits with confidence in the strength of the structure obtained. This invention can be applied to different fields in the construction industry.

This invention discloses a method of constructing a layered structure comprising the steps of receiving the physical data of the object to be modeled; providing a data set of at least one predefined voxel shape; generating a geometric representation corresponding to the said physical data using the selected voxel shape; providing a chamber filled with a non-flowable material and a print head means connected with the said chamber having at least one nozzle; dispensing a plurality of drops of the non-flowable material on a periodic basis directed vertically downward to a target surface underneath in a layerwise fashion; and repeating said dispensing to form a layered structure, wherein the step of generating a plurality of drops comprises the step of configuring the position of the nozzle such that, with reference to the position of the earlier drop, the subsequent drop has a predetermined horizontal distance displacement whereby allowing voxels formed by the earlier drop and the subsequent drop be arranged in an overlapping manner; and wherein a compression between a partially formed voxel created by an earlier drop and a subsequent drop causes the sacrifice of at least some volume of voxel and fusion of the material at the points of compression thereby forming a fused zone resulting in creating stronger bonding , and wherein at least one part of said voxel is partially protected from compression thereby providing strength to the cured structure and forming a non-compressed zone.

An apparatus for implementing said method is also disclosed herein. The said apparatus comprises a chamber filled with a non-flowable material; a print head means connected with the said chamber having at least one nozzle and configured to receive said non-flowable material from the chamber and generate a plurality of drops of the non-flowable material on a periodic basis directed substantially downward to a target surface underneath in a layerwise fashion; a controller, being a drop forming mechanism, connected to said print head means and adapted to configure the position of the nozzle and the shape of drop generated from said nozzle; wherein the said controller comprises a data receiving means for receiving the physical data of the object to be modeled, a memory unit comprising a data set of at least one predefined voxel shape, and a translation mechanism connected with said data receiving means and said memory unit and configured to select a voxel shape and generate a geometric representation corresponding to the said physical data using the selected voxel shape; and wherein the said controller adapted to configure the position of nozzle such that, with reference to the position of the earlier drop, the subsequent drop has a predetermined horizontal distance displacement whereby allowing voxels formed by earlier drop and subsequent drop be arranged in an overlapping manner; and wherein a compression between a partially formed voxel created by an earlier drop and a subsequent drop causes the sacrifice of at least some volume of voxel and fusion of the material at the points of compression thereby forming a fused zone resulting in creating stronger bonding, and wherein at least one part of said voxel is partially protected from compression thereby providing strength to the cured structure and forming a non-compressed zone.

In one aspect of the invention, the memory unit contains a plurality of dataset of predefined voxel shapes, each having a predefined instruction for processing the matching physical data of the object to be modeled. The controller may also comprise the second translation mechanism configured to select a specific shape of voxel from a set of predefined shapes corresponding to the physical data of the object to be modeled. The possible shapes of the horizontal surface include such as the shape of a square, pentagon, circle, or hexagon.

In another aspect of the invention, the displacement is configured such that the overlapped horizontal surface area of voxels in different layers is in the range of 1 : 10 to 3 :4. For the construction time which depends on the time of constructing a single layer, the said time period depends on the property of the material and is adjustable by the user. The time before printing the upper layer is calculated from the total height, height of each layer, compressed height of each layer, and speed of the vertical movement of a print head. The said time (T) can be expressed as

T = f (D / n(y) Sy)

Whereby D = height; n = height of each layer; y = a ratio between the compressed height and the height of voxel; Sy = vertical movement of a print head In another aspect of the invention, the nozzle is positioned at a predefined height above the top surface of the layered structure and is moved to an upper position after the construction of each layer whereby maintaining the predefined height between the nozzle and the top surface of the layered structure.

In another aspect of the invention, the apparatus comprises a plurality of nozzles which are arranged in a row and configured to print voxels of the material concurrently. The print head means can further comprise a mould for forming a drop shape before dispensing and an air pump adapted to pump air for pushing the material from the mould.

The objectives and unique characteristics and other aspects of this invention will be described more in detail by way of the examples and drawings included and the best mode will also be further described.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the diagram of the components of the apparatus

FIG. 2 shows the preferred shape of a voxel

FIG. 3 shows the preferred arrangement of the voxels

FIG. 4 shows the comparison of the compressive strengths for different voxel sizes

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

For a better understanding of the preferred embodiment and to show how it may be performed, it will now be described in more detail by way of examples only with reference to the accompanying drawings. The parts shown in the drawings will be represented by the referenced number. The description, however, does not imply to any limitation and the scope of the invention will be in accordance with the claims attached herein.

This invention discloses a method of constructing a layered structure comprising the steps of receiving the physical data or numerical control programming data set of the object to be modeled; providing a data set of at least one predefined voxel shape; generating a geometric representation corresponding to the said physical data using the selected voxel shape; providing a chamber filled with a non-flowable material and a print head means connected with the said chamber having at least one nozzle; dispensing a plurality of drops of the non-flowable material on a periodic basis directed vertically downward to a target surface underneath in a layerwise fashion; and repeating said dispensing to form a layered structure, wherein the step of generating a plurality of drops comprises the step of configuring the position of the nozzle such that, with reference to the position of the earlier drop, the subsequent drop has a predetermined horizontal distance displacement whereby allowing voxels formed by the earlier drop and the subsequent drop be arranged in an overlapping manner; and wherein a compression between a partially formed voxel created by an earlier drop and a subsequent drop causes the sacrifice of at least some volume of voxel and fusion of the material at the points of compression thereby forming a compressed zone, and wherein at least one part of said voxel is partially protected from compression thereby providing strength to the cured structure and forming a non-compressed zone. The applicable non-flowable materials include the material which becomes flowable when external force is applied to the material such as a low- slump material. The material is dispensed from the nozzle in the form of a plurality of

discontinuous drops which forms an array of elements of volume or voxels.

An apparatus for implementing said method is also disclosed herein. The said apparatus comprises a chamber 1 17 filled with a non-flowable material; a print head 1 1 1 comprises mould 1 13 and nozzle 1 15 and a print head 1 1 1 is connected with the said chamber having at least one nozzle 1 15 and configured to receive said non- flowable material from the chamber and

consequently generate a plurality of drops of the non-flowable material on a periodic basis directed substantially downward to a target surface underneath in a layerwise fashion; a controller 107, being a drop forming mechanism, connected to said print head means 1 1 1 and adapted to configure the position of the nozzle 1 15 and the shape of the drop generated from said nozzle 1 15; wherein the said controller 107 comprises a data receiving means as an input system 101 for receiving the physical data of the object to be modeled, a memory unit 103 comprising a data set of at least one predefined voxel shape, and a translation mechanism which can be a data processing unit 105 connected with said data input system 101 and said memory unit 103 and configured to select a voxel shape and generate a geometric representation corresponding to the said physical data using the selected voxel shape; and wherein the said controller 107 adapted to configure the position of nozzle such that, with reference to the position of the earlier drop, the subsequent drop has a predetermined horizontal distance displacement whereby allowing voxels formed by the earlier drop and the subsequent drop be arranged in an overlapping manner; and wherein a compression between a partially formed voxel created by an earlier drop and a subsequent drop causes the sacrifice of at least some volume of voxel and fusion of the material at the points of compression thereby forming a fused zone, and wherein at least one part of said voxel is partially protected from compression thereby providing strength to the cured structure and forming a non-compressed zone. Fig. 1 schematically shows the overall configuration of the system. In a preferred embodiment, the user input system 101 is a computer system capable of receiving the input from the user. Such input may contain a set of instructions, information on the structure to be modeled, the characteristics of the material to be used, and/or any other user requirements. After receiving the input, the information received will be contained in one or more memory units 103 and processed by the data processing unit 105. The said memory unit may contain the instructions for processing input data in order to generate the appropriate configuration for the controller 107. The said controller will then further control the speed and direction of the movement of the print head or nozzle and also the shape of the voxel and the quantity of the required material. In the possible embodiments, the said controller can be separated into different controllers according to each functionality. For example, the controller may comprise a controller for controlling a horizontal movement of the print head 201, a controller for controlling a vertical movement of the print head 202, a controller for controlling the amount of material required for building each voxel 203, and a controller for voxel shape selection 204. In this regard, the term "print head" and similar terms thereof including nozzle are to be understood to include any device or technique that deposits or creates material on a surface in a controlled manner. In a preferred embodiment, a plurality of print heads positioned along the surface area of the structure is used. In some embodiments, one or more print heads movable along the said surface is used instead. A preferred embodiment may comprise at least one pusher 1 19 which assists in pushing the material through print heads and can be implemented in the form of an air pump. In one aspect, the user is allowed to input the shape of the structure to be formed. After processing the said input data, the controller 204 may be configured to select the suitable voxel shape based on the prerecorded database 109. The selection may be based on the relationship between the physical shapes of the voxels and the final structure. The information on the structure size, the level of strength required, moving direction of the print head, and the construction time may also be considered The setting time can be used in controlling the quality of the layered structure obtained from the disclosed method and apparatus. One may determine that the waiting time before dispensing subsequent drops forming an upper layer is less than the setting time of the lower layer formed by earlier drops. Hence, the range of the said waiting time can be expressed as the ratio fallen in the range of 0 to 1 of the actual setting time. The time before printing the upper layer can be calculated from the total height, height of each layer, compressed height of each layer, and speed of a vertical movement of a print head and expressed as

T = f (D / n(y) Sy)

Whereby D = height; n = height of each layer; y = a ratio between the compressed height and the height of voxel; Sy = vertical movement of a print head

In practice, the time required for printing one layer is in the range of 25-30 seconds.

After dropping and forming the preferred voxel, as shown in Figure 3, it is also necessary to have these voxels positioned in an overlapping manner with each other so that there is a certain surface area that can be fused together, providing higher bonding. The relationship between the necessary area and strength is not linear and there is also a range of the overlapped area that corresponds to the acceptable strength of the structure. In the preferred embodiment, the voxels are organized to overlap in the range of 2/8 to 4/8 (overlapped area to the overall area of a voxel) with the optimum ratio of 3/8. It is also preferable to have the nozzle move in a specific direction (i.e. horizontal direction). Such overlapping manner based on the said nozzle movement will also contribute to a higher level of strength.

Also shown in Figure 3, the overlapped area in the preferred embodiment is created via a displacement along the horizontal direction. Additionally, in the preferred embodiment, a plurality of the print head positioned in series at the same horizontal plane is provided and prints one layer of an object onto the previously printed layer. A plurality of voxels can then be produced

simultaneously for at least a section of a layer of the layer as a whole. These voxels may have the same dimension or different dimensions. The layers may have the same level of thickness or different levels of thickness. However, in a preferred embodiment, each voxel has the same shape and dimension and also the same level of thickness. A plurality of print heads may be sequentially and vertically raised after successfully creating each layer in order to form an upper layer. In the preferred embodiment, the preferred voxel is the hexagonal-surfaced voxel. It is also preferable to obtain a voxel having a certain thickness which would correspond to higher strength and construction speed. From the findings, the relationship between the level of thickness and the strength achieved is not a linear relationship. Hence, there is a specific preferable range of thickness. Beyond the said preferable range of thickness, the strength may be lower. The height of the voxel is also preferred to be in the appropriate level. From the experiment, the comparison of the compressive strength and the appropriate voxel size of material are shown in Figure 4. Test results indicate that the normalized compressive strength of the embodied increases as the overlapped zone increases from 1/8 to 3/8. The normalized compressive strength of the embodied decreases after the voxels are overlapped more, indicating that the optimal overlapped zone is 3/8.

For the material used, the general cement-based material or the equivalent replacement can be used such as geopolymer.

It will be appreciated by persons skilled in the art that the present inventions are not limited by what has been particularly shown described hereinabove. Rather the scope of the present invention includes both combinations and sub-combinations of the features described hereinabove as well as modifications and variations thereof which would occur to a person of skill in the art upon reading the foregoing description and which are not in the prior art.