Claims:We claim:
1. An Additive Manufacturing (AM) System capable of printing smart materials including shape memory polymers and shape memory alloys
2. An IIoT and AI enabled compute control system in claim 1 capable of controlling and monitoring the entire AM system
3. A module in claim 2: consisting of AI enabled algorithm to control the powder mixing system, powder feeding, laser parameters and heat treatment chamber automatically based on the user input
4. A powder mixing system in claim 1: capable of mixing different ratios of shape memory alloy and polymer powders based on user input
5. A continuous monitoring system in claim 1: capable of monitoring the entire AM process build through IIoT
6. A heat treatment chamber in claim 1: capable of automatically controlling the thermomechanical programming process required to enable shape memory in the AM built part based on the shape memory alloy or polymer ratio
, Description:Additive Manufacturing System for Smart Materials
Technical field of the invention:
The present invention relates to a laser based additive manufacturing system designed exclusively for smart materials. The system can combine smart materials like shape memory alloys and polymers in user required proportions, adjust the laser parameters based on the material chosen, additively manufacture the component and perform the heat treatment processes required to achieve the shape memory effect.
Background of the invention:
Since the late 1980s, additive manufacturing (AM), also known as three-dimensional (3D) printing or rapid prototyping, is being used. It is the method of creating a three-dimensional solid object by applying a material layer by layer. Reduced tooling costs, flexibility and scalability, reduced inventory, mass customization, simplified assembly process, and elimination of material waste are all advantages of 3D printing. Although significant progress has been made in this subject, much more study is to be done in order to solve the different hurdles that remain. Additive manufacturing of smart materials and structures has recently become one of the most actively investigated areas. Smart materials are materials with the potential to modify their shape or properties in response to external stimuli. With the addition of smart materials, AM-fabricated components can change their shape or properties over time (the fourth dimension) in reaction to external stimuli. The AM of smart materials is referred as 4D (four-dimensional) printing. A 3D printing facility, one or more stimuli, a stimuli responsive smart material, an interaction mechanism between the stimuli/smart material, and a mathematical model to actualize the desired change in property, shape, or functionality are the five main components of the 4D printing process. Selecting the appropriate 3D printing process to produce the smart material structure is one of the major criteria. The 3D printing processes investigated for the various shape memory materials currently are selective laser melting (SLM) for shape memory alloys; stereolithography (SLA), digital light projection (DLP) and direct ink writing (DIW) for shape memory polymers. It is observed that the smart material structures are self-tailored for a specific application. The 3D printing processes are not standardized for printing smart materials. The current invention proposes the design and development of a laser based additive manufacturing system capable of printing smart structures from shape memory alloys, polymers and their composites.
The invention CN109746445B describes the use of selective laser melting process for the AM of 55-56 mass percent nickel and 44-45 mass percent titanium SMA. The patent also details the optimized parameters for the manufacture of Nickel-Titanium SMA using the SLM process but involves the manual mixing and loading of the Ni-Ti alloy, printing using the laser and separate heat treatment for achieving the shape memory effect. The patent CN111979466A describes the laser 3D printing of SMA which is specific only for the 48.4%Ni, Ti: 36.9%, Nb: 14.7% and also the powder mixing and heat treatment process have to be performed separately. Another patent CN110090954B also performed similar laser-based AM of NiTi shape memory alloy which was also specific to 50.6: 49.4 of Ni element and Ti element. A different alloys combination with 50-60 parts of metal foam powder, 30-40 parts of shape memory alloy particles, 3-8 parts of alcohol-soluble resin and 0.1-0.5 part of dispersant was investigated by the invention CN104801704B. The invention reported only the manufacturing method of the shape memory alloy and not the manufacturing method. Several other patents including CN103862049B and CN201510134030.6A included only the laser methods specific for printing NiTi SMA in specific proportions tailored for an application. It is clear that the prior inventions are specific only to NiTi SMAs with the powder mixing and heat treatment process carried out manually. The patents related to the shape memory polymers are related only to the preparation of different material combinations and specific to an application. It is therefore an aim of the embodiments of the present invention is to overcome or mitigate the problems of the prior arts by developing an AM system for the standardization of printing smart materials.
Summary of the invention:
The present invention aims to disclose a laser based smart additive manufacturing system that is exclusive for the manufacture of smart material structures. The manufacturing system comprises of the following modular components: a laser, a laser cladding system, smart material powder mixing system, powder deposition system, printing platform with moving axes, an inert gas chamber, a heat treatment chamber and a computer control system. The user uploads the required 3D model to be printed to the computer control system and sets the required smart material composition and material type. With the user data, the powder mixing system is capable of combining the smart materials in the user input proportion which includes shape memory alloys and shape memory polymers. The control system then sets the laser printing parameters accordingly using the intelligent software program. Once the smart material powder is mixed in the required proportion, the mixing platform transfers the powder to the powder deposition system. The powder deposition system enables the accurate deposition of the powder material layer by layer on to the printing platform based on the required layer thickness. The laser sinters the deposited powder material on the building platform based on the sliced profile from the CAD model through the cladding system. The laser cladding system and the printing platform are enclosed in an inert gas chamber for the effective functioning of laser beam. The printing platform which is capable of moving in the Z-axis supports the printed structure through the completion of printing process. Once the AM of the 3D structure is complete, the build platform moves the finished part to the heat treatment chamber which performs the thermomechanical programming of the part to enable the required shape memory effect. The entire printing process is closely controlled and monitored by the computer control system. The final part with the shape memory effect enable can be removed from the heat treatment chamber and can be used directly in the designed application.

Detailed description of the invention:
In the following description, various embodiments are explained with reference to drawings. For the purposes of understanding, specific details and configurations are set forth.
Figure 1 illustrates a schematic diagram of the additive manufacturing system for smart materials.
Figure 1 illustrates a schematic diagram for providing smart materials additive manufacturing system. The user uploads the 3D model of the required smart material structure to the computer control system (100). The user has the flexibility of selecting the required smart material composition and the material type (polymer or metal). Based on the user input the computer control system with its artificial intelligence capabilities selects the optimized laser parameters for printing the smart structure. The computer control system also controls the powder mixing system (200) to enable the system to combine the smart materials in the proportion as required by the user.
The powder mixing system (200) consists of several chambers to hold different metal and polymer materials in powder form. With the type of material and composition selected by the user, the system combines the various powder materials in the required proportion to prepare the smart material. The smart material powder is then transferred to the powder delivery system (300).
The powder delivery system (300) consists of a re-coater mechanism which deposits the powder on to the build platform (400). The system has the capability to move up and down on the Z-axis enabling the re-coater to deposit the powder material for the required layer height. The excess powder in the delivery system can be reused or discarded based on the required properties.
The build platform (400) holds the laser sintered part as the part is built layer by layer by the laser system (Laser (500) and Laser cladding (600). The build platform also consists of a heating system to heat the build plate to the required temperature to hold the first layer of printing. The build platform adjusts the layer height based on the layer thickness enabling the re-coater mechanism to deposit the powder required without contacting built part from the previous layers. This ensures that there is no layer deformation in the part.
The laser system consists of a fiber optic laser (500) depending on the power required to melt the shape memory alloy or polymer powder. The laser is directed on the powder bed based on the layer slice profile using a laser cladding system (600). The cladding system is galvanometer-based system which directs the laser beam on to the powder bed and fuses the powder particles to form a solid 3D structure. Once the part printing is completed by the laser system, the part is then moved to the heat treatment chamber automatically for further post processing and heat treatment.
The heat treatment chamber (700) consists of temperature control elements that are used to perform the thermomechanical programming of the finished part to enable the shape memory effect in the shape memory alloy or polymer. The thermomechanical programming part involves the heating of the part to a temperature above the glass transition temperature of the material; applying a mechanical load; cooling the part to room temperature; and removing the mechanical loading. The entire programming process is automated in the proposed AM system to enable the shape memory behavior of the 3D structure. Once the shape memory behavior is programmed, the finished part can be removed from the palette attached to build platform and further post processing can be carried out if needed.
The laser system consisting of the optic laser and the cladding system are enclosed inside an inert atmosphere chamber (800) for optimum functioning of the laser. The system also consists of an IIoT based monitoring and control system (900) to monitor the various parameters during the printing process. The parameters include laser power, energy density of the laser, scanning speed, hatch spacing, layer thickness, bed temperature and chamber temperature. The monitoring system enables in the maintenance of the optimum process parameters for the part to be built. Each layer being printed are monitored through various sensors in the AM system and a camera attached above the built platform to monitor the printing process layer by layer.
The above embodiments are described by the way of producing a 3D part using smart materials such as shape memory alloys and shape memory polymers using an AM system. The described manufacturing system can be designed in different variations (using different laser system, powder deposition system and mixing system) without departing from the scope of the invention.