Applications for Stratonics’ ThermaViz® Sensor Systems
Stratonics’ sensor systems are used in applications requiring real time monitoring, analysis, and control of thermal and dimensional properties. Additive manufacturing (AM), also referred to as 3D printing, is a concentrated focus in our organization. Our ThermaViz® sensor suite uniquely delivers valuable insight to solidify the understanding of this emerging technology.
AM builds a three dimensional part by adding layer upon layer of material, fusing each layer to the previous layer. Material selection includes a range of metals, plastics, and ceramics, from common materials such as ABS, to unique alloys for specific applications. AM has transitioned from its initial applications of rapid prototyping and concept modeling to the fabrication of end-use parts for industry, e.g. aerospace, automotive, medical and oil/gas/power.
There are numerous advantages to AM over traditional manufacturing (subtractive):
- Engineering: complex geometries, weight reduction, combining assemblies into single parts, rapid design iterations
- Materials: creation of new materials, improved material properties
- Manufacturing: minimized lead time and material waste, elimination of tooling, component repair
It is also recognized that these substantial advantages bring significant challenges.
Subtractive manufacturing has a long standing history of process verification and part certification. Similar methods must be established to understand AM and validate the outcome. There are two inputs into the AM equipment; geometry from a CAD model and process parameters specified for the material and the machine. Extensive knowledge of material design and the AM machine itself is required to fabricate quality parts. Currently, considerable effort is required to iterate complex deposition models to select a range of build parameters, which are expected to produce parts with high quality and specified properties.
A number of parts are built and examined for quality and properties and the range of processing parameters is narrowed to a select few. These parameters are then used to produce a large number of parts and the optimized set of process parameters is selected. This parameter set is then considered qualified for AM of the part. However, even using these qualified parameters, machine drift may allow for components that will not meet specification; hence, the need for process monitoring and control to maintain high quality of outcome.
Thermal and physical dynamics occurring at the point of melting and solidification drives the microstructure in the material and defines the mechanical properties of the part. Layering, multiple interfaces, and complex printing paths can cause defects and result in poor mechanical properties. Stratonics’ ThermaViz® Systems are critical tools used to overcome key challenges in the advancement of AM. Implementation of our systems during the research of new methods and materials reduces the iterative modeling effort, converges on a limited set of experiments and allows for model enhancement and validation. Monitoring both the melt pool and the global heat flow throughout the build and performing real-time analysis generates feed-back control to maintain defined process parameters, resulting in parts with high quality. The ability to record the image and associated analysis yields a digital thread for the additive manufacture of each part, leading to part certification and reduction in post process evaluation.
Laser Metal Deposition (LMD)
is an AM process that uses a focused high power laser beam to melt powdered metal delivered through nozzles. The melt pool forms a deposit that is fusion bonded to the previous layer. The nozzle/laser apparatus is manipulated using a CNC gantry system and its path is determined by a 3D CAD model. The process is performed in an inert gas environment, e.g. argon, to avoid oxidation. Melt pool size of a few millimeters, build velocities of 5-50 mm/second and laser power levels of 100’s to a few 1000 watts are common to the LMD process. Common materials include stainless steel, Inconel and titanium alloys. This process is also referred to as Direct Metal Deposition (DMD), Direct Laser Deposition (DLD), Laser Engineered Net Shaping (LENS), Laser Cladding, Laser Deposition Welding and Powder Fusion Welding.
A subscale test build of a rocket engine cone by Metal Additive Manufacturing using directed energy deposition at Connecticut Center for Advanced Technology’s Advanced Manufacturing Center
Directed Metal Laser Sintering (DMLS)
is an AM process that uses scanning mirrors to aim a high powered laser onto a bed of metal powder. The laser beam micro-welds the material in a pattern determined from a 3D CAD model. The laser power is paused as the layer is completed. The bed is dropped a small distance, 10-100 microns, and a re-coater blade spreads another thin layer of powder over the current deposit on the build platform. Melt pool size of 50-200 microns build velocities of 0.5 to 2 meters/second and laser power levels of 100’s of watts are common. The process is performed in an inert gas environment, e.g. argon, to avoid oxidation. Common materials include stainless steel, Inconel and titanium alloys.
Test coupon build in EOS DMLS system at the Applied Research Lab, Penn State University.
Fused Deposition Modeling (FDM)
is an AM process that extrudes a thermoplastic filament through a heated nozzle. The extruder head is moved, along with the build platform as the part is built up layer by layer. This process generally takes place in an enclosed and heated chamber to ensure consistent melting and solidification. Common materials used are ABS, Nylon, Polycarbonate and ULTEM, among others. This process is also referred to as fused filament fabrication (FFF), and Plastic Jet Printing (PJP).