Additive Projects

My Master's thesis is on studying how various process parameters affect mechanical properties of Laser Powder Bed Fusion printed parts. Lack of consistency in mechanical properties of L-PBF printed parts prevent widespread adaptation of this technique in industry. To understand the factors that cause variability and inconsistency in mechanical properties two plates each of tensile and compression samples were L-PBF printed in various orientations using Inconel 718 alloy. One plate each of compression and tensile samples was subjected to solution annealing and double aging heat treatment. Tensile, compressive and hardness properties were measured in as built and heat-treated condition. Compressive properties were also characterized in the machined condition to understand the influence of all post-processing activities on mechanical properties. Porosity of compression samples was characterized with X-ray micro computed tomography to understand the influence of porosity on mechanical properties.

Apart from build orientation, factors such as shape, thickness and laser scanning path were found to cause variation in mechanical properties. Anisotropy in mechanical properties that developed because of build orientation and laser scanning path was retained after heat treatment. Hardness increased by 58% after heat treatment. More than 50% of porosity by volume was found to be removed after machining compression samples from 2mm nominal diameter down to 1.5mm diameter. The samples also showed higher yield and Young's modulus after machining. An attempt has been made to explain the observed variability in mechanical properties across orientation and part position on the build plate using machine learning algorithms. Although the regression approach could not explain the variability, the classification technique seems to be a plausible approach. Orientation and position could not completely explain the variability in mechanical properties. This suggests that more variables are involved in determining the final mechanical properties of L-PBF printed parts.

I started my internship at Elementum 3D from 2nd of July 2018. As an intern I was trained on various stages of Additive Manufacturing process as follows,

• Powder metallic material handling and safety
• Preparation of 3D CAD models for 3D printing and selection of build orientation.
• Using EOS print for designing the build layout and selection of build parameters.
• Operation and user maintenance of EOS M290 and EOS M400 L-PBF systems.
• Using Materialise Magics software for adding support structures.
• I have involved in a project of characterizing sub-surface porosity of 3D printed Al2024 alloy and found the combination of laser parameters which produce least porosity.

The Schrade backpacking shovel was originally disassembled to begin the process of a complete redesign for additive manufacturing. By analyzing each part and modeling them in Solidworks, the team began to make changes to the parts in order to capitalize on the benefits available from additive manufacturing. Throughout the term, adjustments were made to this design based upon prints made for each design.

These test prints were done using the Colorado School of Mines CECS Garage. This facility offered MakerBot and UPrint machines available for use in this project. This enabled the team to find an optimal printing configuration for the parts. As the design iterations continued, the team was able to reduce the total of number of parts in the shovel, simplify the labor required for assembly, decreased total weight, and improved aesthetic appeal.

Challenges were faced due to the low resolution of the available printers, as well as part distortion due to surface material residue. This problem especially surfaced in the threaded areas of the part. Through multiple design iterations, these problems were overcome and resulted in a successful product which was optimized for additive manufacturing.

Conductive polymer composites are manufactured using additive manufacturing for a variety of purposes. These materials show great potential for use in electronic devices, circuits, sensors, and EMI shielding. Through advances in additive manufacturing, these conductive materials could be seamlessly integrated alongside insulating materials to create a conductive run within a solid part.

Due to the fundamental changes a material undergoes of melting and solidification for additive manufacturing, it is important to understand the impact this process has upon the material. Through changes in the printer’s extrusion temperature, layer thickness, nozzle diameter, etc, the resulting characteristics of the printed part may vary from the original filament. This research will explore the electrical characterization of additive manufactured conductive polymer composites under various printing configurations and conditions.

By formulating a diverse sample set with a consistent characterization plan, a solid understanding of each material’s resistance is derived from this data. The carbon black filament proved to be much more user-friendly during the printing process. It was stable when printed under various conditions and did not show signs of clogging the printing head. The graphene filament, on the other hand, proved to be a little more difficult to work with. While this is a favorable property of the carbon black, the electrical properties of graphene seem to be far superior. Not only were the graphene samples of a significantly lower resistance than carbon black, but they were also much more consistent. The carbon black samples varied greatly in resistance based on the layer size and extrusion temperature, while the graphene remained very consistent and predictable.

Both materials appear to be comparable in mechanical properties, exhibiting good strength and no signs of delamination or distortion. However, more work should be done to fully understand the differences in mechanical properties between these two composites.