Precision Additive Manufacturing Research Articles

Precision additive manufacturing of NiTi parts using micro direct metal deposition

Micro manufacturing using micro direct metal deposition was successfully implemented on NiTi powder alloy. Micro direct metal deposition was optimized through a set of process parameters and designed experiments to improve the geometrical accuracy and repeatability of micro fabrication. Scanning electron microscopy and micro X-ray computed tomography were used to analyze the surface quality, micro porosity, and deviations of products with respect to nominal geometrical models. Results showed that increasing scanning speed is an efficient way to improve the surface quality and decrease the micro porosity content. Below 15% deviation to nominal geometrical models was achieved in hollow NiTi samples through a set of micro direct metal deposition process parameters and designed experiments.

Microstructure and tensile properties of Ti-6Al-4V alloys manufactured by selective laser melting with optimized processing parameters

Selective laser melting (SLM) is a precise additive manufacturing process that the metallic powders without binder are melted layer by layer to complex components using a high bright fiber laser. In the paper, Ti-6Al-4V alloy was fabricated by SLM and its microstructure and mechanical properties were investigated in order to evaluate the SLM process. The results show that the microstructure exists anisotropy between the horizontal and vertical section due to the occurrence of epitaxial growth, and the former microstructure seems equal-axis and the latter is column. Moreover, there is little difference in tensile test between the horizontal and vertical sections. Furthermore, the tensile properties of fabricated Ti-6Al-4V alloy by SLM are higher than the forged standard ones. However, the fatigue results show that there are some scatters, which need further investigation to define the fatigue initiation.

A Large Range Flexure-Based Servo System Supporting Precision Additive Manufacturing

Abstract This paper presents the design, development, and control of a large range beam flexure-based nano servo system for the micro-stereolithography (MSL) process. As a key enabler of high accuracy in this process, a compact desktop-size beam flexure-based nanopositioner was designed with millimeter range and nanometric motion quality. This beam flexure-based motion system is highly suitable for harsh operation conditions, as no assembly or maintenance is required during the operation. From a mechanism design viewpoint, a mirror-symmetric arrangement and appropriate redundant constraints are crucial to reduce undesired parasitic motion. Detailed finite element analysis (FEA) was conducted and showed satisfactory mechanical features. With the identified dynamic models of the nanopositioner, real-time control strategies were designed and implemented into the monolithically fabricated prototype system, demonstrating the enhanced tracking capability of the MSL process. The servo system has both a millimeter operating range and a root mean square (RMS) tracking error of about 80 nm for a circular trajectory.

A methodology for precision additive manufacturing through compensation

Maturation of powder-bed additive manufacturing (AM) is essential for the business benefit the rapid adoption of AM offers to industry. One of the principal challenges in powder-bed AM is the mitigation of distortion due to material shrinkage and residual stresses induced during the build process. In order to address this, a new methodology for distortion compensation is developed and presented in this paper. The novelty of the methodology lies in the use of a mathematical model for pre-distorting the design geometry based on 3D optical scanning measurement data. The methodology has been applied to two industrial Inconel 718 components (a turbine blade and an impeller). It was experimentally demonstrated that distortion compensation is achievable using the proposed methodology. The results showed the compensation methodology reduced distortion from approximately ±300μm to approximately ±65μm for both components. In summary, the novel methodology can be used to deliver near-zero distorted parts for industry using powder-bed AM processes.

Effects of error in a subordinate oscillator array

Existing research has shown that the response of a single degree of freedom resonant system can be modified by the attachment of sets of substantially smaller resonators. Such arrays of attachments, known as subordinate oscillator arrays, can increase the apparent damping of the primary structure, and the property distributions can be selected such that the collective effects result in a response of the primary resonator that is similar to an electrical band-rejection filter. Other prior work with this system has indicated high sensitivity to disorder in the individual attachment properties such that even 0.1% variation is likely to cause undesirable effects in the overall system response. Such levels of variation well below 1% are easily attributable to typical manufacturing tolerances, environmental influences, and degradation factors. This work presents experimental results of a set of prototype subordinate oscillator arrays produced with high precision additive manufacturing techniques so as to prescr...

Dexterous Printing and Fabrication of Multi-Functional Parts: Design for Science and Engineering Education

With the introduction of precision additive manufacturing techniques, the complexity of a particular fabricated part rivals that which is possible with conventional manufacturing alternatives. The drawback to this, however, is the time investment required to bring an object to its completion, which limits the practicality of an otherwise advantageous shift in manufacturing. To counteract this, an ambidextrous multipurpose hybrid machine (DEXTER), operating dual SCARA has been developed to reduce the time of single and multi-material builds. While the SCARA functionality brings forth new obstacles not inherent in conventional gantry setups, optimization studies were performed to minimize the irregularities in print performance. Ensuring a natural lateral movement in manufacturing practices between the traditional and dual arm approach. During prototyping, the current DEXTER model is being used to train the next generation in additive thinking, and to educate them on current manufacturing methods and devices. Doing so creates a generation with the skill set to join the workforce ready to take on the new revolution in manufacturing.

3D metal droplet printing development and advanced materials additive manufacturing

While commercial additive manufacturing processes involving direct metal wire or powder deposition along with powder bed fusion technologies using laser and electron beam melting have proliferated over the past decade, inkjet printing using molten metal droplets for direct, 3D printing has been elusive. In this paper we review the more than three decades of development of metal droplet generation for precision additive manufacturing applications utilizing advanced, high-temperature metals and alloys. Issues concerning process optimization, including product structure and properties affected by oxidation are discussed and some comparisons of related additive manufactured microstructures are presented.