Rapid Induction Printing™
The smartest way to make metal.
Rosotics has conceived, developed, and filed patents for a new method of metal additive manufacturing, a method that is more effective than any other.
Rapid Induction Printing™ expands upon the fundamental elements of directed energy deposition (DED), unifying these elements to a single piece of hardware and removing the need for a laser, electron beam, or plasma arc.
Rosotics is leveraging the benefits of Rapid Induction Printing™ in order to realize designs faster and with less resources, while allowing the process to take place from a mobile platform.
Existing technologies for metallic additive manufacturing can normally be classified within several categories; sintering or DMLS, adhesive bonding, and directed energy deposition. In sintering, a highly regulated inert gas chamber is spread with a powderized metal across a bed, which is selectively melted by a high-power laser. The selective melting of each successive layer works to form a desired object, and at the end of the process, the object is removed from the bed and cleaned. In adhesive bonding, the process is rather similar, however an adhesive is used to join the powder particles rather than the energy of a laser. These two processes are problematic because a significant amount of the powder used for this work cannot be reused, and must just be disposed of. These powders are also problematic procedurally, as they are very expensive to produce and source, and are difficult and dangerous to handle. When spilled, the dust released into the air is dangerous to inhale, and may even be an explosion risk. Lasers also have numerous safety risks, exceedingly so at the power levels required to fuse metals. Procedurally, these processes are very inefficient as the heating must be provided top-down, lasers have inherent losses in energy conversion, and numerous inefficiencies exist in material handling.
A significant innovation arrived recently in the creation of a process known as directed energy deposition (DED). In DED, a coaxial feed of wire feedstock is delivered to an energetic source (usually a laser, plasma arc, or electron beam) to form a melted or sintered layer on a substrate. The core benefit of this process is that it is capable of being conducted mostly or entirely from the print head, leading to applications at the large scale. Companies have utilized this process in tandem with large industrial robotic arms, in order to print enormous structures. However, this process has a comparatively low print resolution compared to other methods and the high energy input has significant metallurgical implications. A large heat affected zone around the melt pool is subjected to large thermal gradients that cause residual stresses which can lead to object distortion. These stresses, coupled with the cyclical nature of the thermal process, can adversely affect the grain structure and strength of the printed metal. The residual stresses in DED can often be so severe that sometimes the print must be interrupted and stress relieved. This involves constant monitoring of the print, stopping it when distortion surpasses an acceptable limit, allowing it to cool, and then moving the build (which can be enormous and heavy) to a furnace to perform lengthy heat treatment. All of these steps need to be completed before the part can be returned and realigned in the printer to continue the build. In addition, since most DED processes are low-resolution and have limited geometric capability, there is often significantly more material deposited than the final part requires. This is known as a near-net-shape process, requiring machining to refine to a net shape. DED machine prices range anywhere from $200,000 USD to upwards of $3,000,000 USD for large industrial printers. It is a useful process methodology for the large-scale market segment, however deeply and inherently flawed.
Rosotics has conceived of an improved process which enables the additive manufacturing of metal objects with a high degree of energy and material efficiency, print resolution, and performance quality. The process removes human and environmental risk factors and is completely isolated to the print head, allowing for practical mobilization (further in compliance with FAA statutes). This proprietary process is titled Rapid Induction Printing™, and is debuted within class Stinger.
We used the following criteria in search for an improved metal printing process:
Completely isolated to the print affector, requiring no regulated environment
Comprehensively optimized for mobilization and autonomy, in terms of hardware and software
Energy efficient as a foremost consideration and not a benefit
Lightweight in terms of hardware, with a small physical footprint
Low factor of human and environmental risk, not catastrophic in event of failure
Utilizing a wire feedstock rather than a metallic powder
Cost-efficient in terms of hardware required
Accurate and demonstrating an extremely high element of precision, resolution
Utilizing hardware that is manufacturable and deployable at scale
Able to extract a high volume of real-time digital information as to process performance
Easily and rapidly fault tolerant in the event of an anomaly
Demonstrating a high degree of linear print speed
Capable of depositing material at a high volume without material waste
Not requiring, or requiring absolutely minimal post-processing or heat treatment
This process we developed is principally conducted from a structure known as the injector, which is a slit and stipple vented nozzle, with an electric coil housed on the interior, and containing an additional concentric outlet channel within the nozzle wall which is concentrated inwards to the work point for a gaseous flow. The injector is affixable to either a cartesian motion system on the x/y axes, or a 6-DOF robotic arm motion system. The motion system positions the injector at a desired position, and is powered electrically. A wire feedstock is housed within a separate storage structure, while shielding gas is stored in the pressurized state within another separate storage structure. The injector is housed within a structure referred to as the terminator. A thermal camera is affixed tandem to the injector, within the terminator. The terminator also positions small cooling fans against the injector's slit and stipple to remove gas produced within the nozzle during the heating process. Digital elements are utilized to analyze the real-time process state analytics of the process as it is conducted.
Under an agreement of the National Aeronautics and Space Administration (NASA), Rosotics utilizes within Rapid Induction Printing™ a novel method of performing real-time print analysis during the process of deposition, developed by engineers of Marshall Space Flight Center in Huntsville, AL. This method is used to provide real-time dimensional inspection parallel to and during the deposition process. This eliminates the need for post-build inspection, and complex internal geometries of exceedingly large components are mapped. A closed-loop feedback control system is incorporated to enable real-time adjustments during the build process as necessary and to correct errors as they occur.
During the Rapid Induction Printing™ process, shielding gas begins to flow from the injector to function as localized shielding over the work spot in order to combat oxidation and remove the need for a controlled environment. Precise wire feed systems begin transfer of feedstock into the injector, as motion systems position the tip of the injector towards a desired printing location. Once the injector is positioned, electric current is pushed through the coiled nozzle and into the metal feedstock by means of electromagnetic induction, subjecting the metal feedstock to a phenomenon known as induction heating, through heat generated in the feedstock by eddy currents. The current delivered through induction melts the feedstock tip into the liquid state, which is ejected from the injector. Feedstock travel and melting continue while the injector moves, laying down material at rapid linear speed, which fuses together to form fully dense metal objects. Gas and heat generated during this process escapes the injector through slit vents and stipple of the nozzle.
Rapid Induction Printing™, a significant innovation in the field of metal additive manufacturing, delivers an order of magnitude higher print resolution than comparative DED processes at a higher linear print speed, which is suitable for a broad range of applications. In addition, rather than traditional methods of heat generation, such as a high power fiber laser, much greater efficiency is achieved since electricity is converted directly into heat. This makes the process more energy and material efficient, and results in a total lower cost print solution which can print much nearer net-shape. In addition, since the laser has been removed from the state flow, the system is safer in terms of human and environmental risk assessment. It eliminates the costs of working with powder, depositing on the order of kgs/hr and allowing simplistic feedstock production, ease of handling, and rapid machine resupply. This boost in productivity and reduction in raw material costs yields costs-per-print that are 30-60% lower than traditional manufacturing methods in many applications. Rosotics believes that when this process is leveraged in tandem with other variables such as swarm robotics, process state integration, and vertical supply chain integration, this value can be increased further.
Rosotics has developed the proprietary Rapid Induction Printing™ process in order to meet new design goals in the development in their mobile manufacturing platform, and is demonstrating this process operationally beginning with class Stinger.