Description:FIELD OF INVENTION
This invention relates to the field of large-scale 3D printing. More particularly to a method and system for sacrificial layer stacking in concrete 3D printing.
BACKGROUND OF THE INVENTION
In Construction 3D technology (offsite), the printing platform is a standalone and movable pallet made of sturdy materials. The printed modules are allowed to cure for a few days before being moved for site assembly. Constant usage, wear and tear and environmental factors cause deformation of pallets. Significance of the build platform arises from the weight of 3D printed structures, where the concrete 3D printed components weigh about 100 kg to 5000 kg; unlike FDM/Plastic 3D printed components that weigh in grams. In addition, printing of additional layers in the latter majorly contributes towards increasing bottom adhesion whereas it has no significant effect on layer compression. Due to the enormous weight of the structures being printed using concrete 3D printing, the build platform needs to meet certain structural requirements which leads to compromise on the ease of platform levelling. This is not the case with small scale 3D printers where simple screw-based build platform levelling systems are used.
Another Japanese patent JP6335782B2 relates to the fabrication of electronic and / or mechanical structures, components, and devices used in the electronics industry and the like. In particular, the invention relates to the process of using uniform or non-uniform materials in the three-dimensional fabrication of electronic and / or mechanical structures, components, and devices. The invention also relates to a selective metallization process including electroless and / or electrolytic metallization.
The patent US10761497B2 discloses about a software feature to achieve higher Z-axis dimensional accuracy. The approximation used by slicers for generating layers often compromises the total height of the component. In other words, if we need to print a 1.2 mm object with layer height of 0.25 mm, we can only achieve 1 mm or 1.25 mm object height because the total height achieved is a multiple of layer height parameter.
Another patent US9524357B1 discloses a method of generating support structures that enable one to print complex geometries. The outer surface of the 3D object is passed through vertical rays that align normal to the surface of the 3D object. These rays are later integrated into the 3D printing file as they add branches that support the overhang in the 3D object to be printed.
Build platforms in FDM or Powder-based 3D printing systems exist as a part of the printer itself which reduces the size of the platform to suit that of the printer which is also susceptible to temperature variations of the printer. To overcome the space restrictions and effects of temperature while printing, certain practices are followed. One such practice is the printing of additional layers to the printed part that act as a support structure for overhangs and increase build plate adhesion. Currently, many 3D printing slicer software allow for generating automatic support structures. The removable structures vary depending on the design of the part to be 3D printed. This structure is printed along with the part required and is removed after printing. It assists in printing complex parts that require support while printing and is commonly adopted for parts having overhangs. Some 3D printers offer the option of using dissolvable material to print support structures. A ‘lattice’ structure covers the entire bottom surface of the part whereas ‘tree-like’ structure supports only significant points of the part.
Prominent options for generating bed adhesion available in the commonly used software are listed below:
i. Raft tool creates a horizontal lattice work under the part.
ii. Skirt tool generates a structure, outlining the part without touching it
iii. Brim tool generates a thin structure attached only to the edges of the part.
The present techniques used for strengthening bottom layers pose several limitations as follows:
1. Specific design has to be generated for the structure as the layers need to be accessible during removal without affecting the actual part.
2. While the printing speed for all the layers is the same, it does not allow sufficient time for better bonding between layers. Thus, the layers become uneven due to the unevenness of the build platform.
3. Over/under extrusion of the material for bottom layers causes improper adherence to the platform surface and becomes difficult to remove.
4. Constant use of the build platform causes deformation and uneven surfaces which necessitates the tedious process of calibration for every print.
5. Environmental factors such as temperature and humidity cause significant changes to printed parts.
Material and Layer characteristics:
1. Printed layers deform after extrusion due to material non-conformity.
2. Hydrostatic pressure and self-weight generated by the subsequent layers create compression on the bottom layers.
3. Layer cycle-time depends on the geometry of the structure. Time taken for layer hardening varies, creating weak inter-layer bonding.
4. Force acting on stacked layers is generally perpendicular to them, leading to low strength.
The support structures require special equipment for removal in post-printing processes. The present subject invention elucidates a methodology for printing concrete modules with better strength and verticality. A few sacrificial layers are printed that provide the base support for the modules. The strength of a part manufactured by 3D printing is enhanced through better adhesion between the layers.
In construction 3D printing, large scale modules are printed that require stable build platforms to withstand the weight of modules. However, constant usage and environmental factors severely impact the platforms leading to damage and instability. Ideally, the printed layers will be aligned normal to the build platform. Due to the irregularity of the base platform, printed layers tend to compress and get inclined in the direction of the undulations. The module becomes distorted which cannot be used as it affects the assembly and finishing in modular construction.
The present invention provides a solution which will aid in eliminating the irregularity of the build platform through its sacrificial layers. The layers will bear the weight of the top layers, flatten according to the unevenness of the platform and get aligned to form a stable base for the module. This provides flat and vertically oriented layers in a module.
OBJECTIVE OF THE INVENTION
The main objective of our invention is to develop a process for removable support structure for printing large modules in construction 3D printing.
SUMMARY OF THE INVENTION
The following summary is provided to facilitate a clear understanding of the new features in the disclosed embodiment and it is not intended to be a full, detailed description. A detailed description of all the aspects of the disclosed invention can be understood by reviewing the full specification, the drawing and the claims and the abstract, as a whole.
In the field of concrete 3D printing, bottom layers attain special significance as structures built using this technology are generally based on modular construction. Not only does each layer in a module need to be well-adhered with adjacent layers, but the modules should also adhere well to one another for a rigid structure.
In the present invention the methodology includes a set of sacrificial layers printed that provides the required support for the top layers to self-align with respect to the normal plane and attain better strength.
The present invention includes the following processes:
1. Printing sacrificial layers
2. Preparing layer surfaces for removal
3. Removal of sacrificial layers
DETAILED DESCRIPTION OF THE INVENTION
The principles of operation, design configurations and evaluation values in these non-limiting examples can be varied and are merely cited to illustrate at least one embodiment of the invention, without limiting the scope thereof.
The embodiments disclosed herein can be expressed in different forms and should not be considered as limited to the listed embodiments in the disclosed invention. The various embodiments outlined in the subsequent sections are construed such that it provides a complete and a thorough understanding of the disclosed invention, by clearly describing the scope of the invention, for those skilled in the art.
The present invention includes three processes as mentioned above wherein the primary process includes printing the sacrificial layer. Sacrificial layers are printed as the bottom-most layers of the module. These layers are similar in dimension and orientation of the other layers of the part being printed. The layers are subjected to the weight of the entire printed part and may develop bulges or other deformations. The printing of sacrificial layers, as put forth in the subject invention, has been incorporated as a feature in our proprietary software which provides options for modifying the dimensions to suit the structure to be printed. The model to be printed is loaded into the software in which the properties of the sacrificial layers can be modified (Settings Page). The model can be viewed before printing on the Preview page of the software.
The second process of the present invention is preparing layer surfaces for removal wherein the number of sacrificial layers is determined by the nature and utility of the part to be printed. As the required number of sacrificial layers are printed, the top-most sacrificial layer is polished with a chemical (emulsified mineral oil) that enables removal of sacrificial layers without damaging the actual module. This can be carried out either manually or through automation.
The third process or the final process of the present invention is the removal of sacrificial layers. The entire module is printed and allowed to cure for one day in the print area and moved to the curing area along with the pallet and is allowed to be cured for 7 to 10 days. After the optimal strength has been attained at the end of the curing period, the sacrificial layers are removed using simple construction tools. The chemical applied on the top-most sacrificial layer helps in removing them without major damage to the printed module.
In one embodiment of the present invention the bottom sacrificial layers offer a stable, even and flat base for the module to be printed.
The method of the present invention ensures the 3D printed model will not take the shape of the uneven print platform. It helps in maintaining evenness of layers irrespective of the undulations of bed/base.
The modules that have been 3D printed on uneven build platforms often face issues during assembly at site. The uneven bottom layers cause difficulty in stacking modules over one other. Through the present method, the flatness of the bottom layers is ensured and hence improves ease of assembly at the site. It acts as the template for adjusting top layers and provides smooth surface finish at the bottom of the printed modules. It rectifies the warping and enhances bonding between module and print platform. It stabilises the printing process by aiding in priming and correcting the mechanical errors of the printer such as: a. Axis calibration (z-axis movement) b. Material extrusion c. Printer speed d. Nozzle level e. Printer orientation.
Fig. 1 illustrates the concrete 3D Printed Module on a build platform. In the present invention, in addition to the actual module, sacrificial layers are printed which are configured to suit the requirement. The present invention further includes the removing the sacrificial materials.
Methods, systems, and apparatuses of the present invention are related to the removal of sacrificial layers. The entire module is printed and allowed to cure for the required number of days. Once the modules are cured, the sacrificial layers are removed using simple construction tools. The chemical applied on the top-most sacrificial layer helps in removing them without major damage to the printed module.
A device, apparatus, article of manufacture, system, component in a system of the present invention may comprise, for example, a 3D printer, a component in a 3D printer, a print head, a print platform, a program storage device storing executable instructions that may be used to implement a method or process or any combination thereof.
Description of real-time example
1. Module Loading in the software
a. The module to be printed is loaded onto our proprietary software.
b. The software shows the options for adding the number of sacrificial layers to the module which depends on the structural and architectural utility of the module.
c. The time taken and amount of material required for printing will be depicted on the software, after which printing can be begun.
2. Printing of sacrificial layers
a. The sacrificial layers get printed first, aligned to the print platform.
b. Once the required number of sacrificial layers are printed, the printing is paused.
c. The top-most surface of the sacrificial layers is coated with an emulsified mineral oil based chemical for releasing concrete.
d. Printing is started again for the actual layers of the module.
3. Curing of modules
a. The printed module is allowed to cure on the print platform (pallet) itself for one day after printing is completed.
b. After the module attains preliminary strength at the end of one day, it is moved away from the print area along with the movable pallet to the curing area where regular curing procedures are carried out.
c. At the end of 3 to 4 days, the module attains enough strength for post-printing processes such as grouting and marking for electrical and plumbing components. Continuous curing activities are carried out.
4. Removal of sacrificial layers
a. The sacrificial layers can be removed after 7 to 10 days of curing. This process is carried out along with the next phase of offsite 3D printing construction, transporting printed modules to site.
b. For removing the sacrificial layers,
i. the module is lifted from its position of curing which automatically loosens the bond between actual and sacrificial layers due to the chemical coated
ii. the sacrificial layers are removed using simple construction tools such as chisel and hammer
c. If required, the sacrificial layers can also be removed by the above procedures at the actual site after transporting the modules.
, Claims:CLAIMS:
I/We Claim:
1. A method for three-dimensional printing, comprising:
a primary process including printing the sacrificial layer, wherein the said sacrificial layers are printed as the bottom-most layers of the module and are similar in dimension and orientation of the other layers of the part being printed;
a second process for preparing layer surfaces for removal wherein the number of sacrificial layers is determined by the nature and utility of the part to be printed; and
a third process or the final process for the removal of sacrificial layers.
2. The method for three-dimensional printing as claimed in claim 1 wherein the said layers are subjected to the weight of the entire printed part and may develop bulges or other deformations.
3. The method for three-dimensional printing as claimed in claim 1 wherein the said printing of sacrificial layers, provides options for modifying the dimensions to suit the structure to be printed, the said model to be printed is loaded into the software in which the properties of the sacrificial layers is modified.
4. The method for three-dimensional printing as claimed in claim 1 wherein the said sacrificial layers are printed, the top-most sacrificial layer is polished with a chemical that enables removal of sacrificial layers without damaging the actual module either manually or through automation.
5. The method for three-dimensional printing as claimed in claim 1 wherein the said module is printed and allowed to cure for 7 to 10 days.
6. The method for three-dimensional printing as claimed in claim 1 wherein the said cured sacrificial layers are removed using construction tools.
7. The method for three-dimensional printing as claimed in claim 1 wherein an emulsified mineral oil product applied on the top-most sacrificial layer helps in removing them without major damage to the printed module.