Fused deposition modelling (FDM) creates three-dimensional parts by feeding a rigid thermoplastic filament through a heated barrel to achieve a semi-fluid state and then extruding it layer-by-layer to create a part geometry. The melt flow behavior within FDM must be analyzed in order to correctly understand the temperature gradients within the system to promote part quality, process control, and efficiency. The presented research consists of analyzing the melt flow behavior of polymer poly(lactic) acid (PLA) within FDM. This includes an experimental analysis of the power output of the resistive heat source, a theoretical analysis of external coefficients of heat-transfer, and an experimental validation of liquefier temperatures. A three-dimensional fluid-flow model is created using the accurate geometry of the extruder assembly, calculated conditions from initial experimental results, and referenced material properties. Results of this research include a significant temperature difference between the areas of the liquefier assembly close in proximity to the power source to those further away such as the inlet and outlet, suggesting that external heat transfer mechanisms play a significant role in liquefier dynamics, contrary to the more common assumption of constant wall temperature or constant heat flux used in modeling. The research presented provides new information regarding the melt flow of PLA, a method of modeling external heat transfer, and a way of understanding power consumption that can lead to liquefier design improvements. The process itself will also aid in identifying modeling considerations for further investigations of melt flow involving various extruder designs and material options. Specifically, the use of this type of comprehensive model is of interest to the additive manufacturing community with respect to thermally sensitive component specification and heating and cooling needs within process based on changing system parameters such as extrusion temperature and mass flow rates (i.e. material feed rate and/or change in extrusion diameter).

A recent development of cooling and lubrication technology for micromachining processes is the use of spray cooling. Atomization spray cooling systems have been shown to be more effective than traditional methods of cooling and lubrication for micromachining. Typical nozzle systems for atomization spray cooling incorporate the mixing of high speed air and atomized fluid. In a two-phase atomization spray cooling system, the atomized fluid can easily access the tool-workpiece interface, removing heat by water evaporation and lubricating the region by oil droplet spreading. The success of the system is determined in a large part by the nozzle design, which determines the droplet behavior at the cutting zone. In this study, computational fluid dynamics are used to investigate nozzle design and droplet delivery to the tool. An eccentric-angle nozzle design is evaluated through droplet flow modeling. This study focuses on the design parameters of initial droplet velocity, high speed air velocity, and the angle change between the two inlets. The system is modeled as a steady-state multiphase system without phase change. Droplet interaction with the continuous phase is dictated in the model by drag forces and fluid surface tension. The Lagragian method with a one-way coupling approach is used to analyze droplet delivery at the cutting zone. Following a factorial experimental design, deionized water droplets and a semi-synthetic cutting fluid are evaluated through model simulations. Statistical analysis of responses (droplet velocity at tool, tool positioning, and droplet density at tool) show that droplet velocity is crucial for the nozzle design and that modifying the parameters does not change droplet density in the cutting zone. Based on results, suggestions for future nozzle design are presented.

Recent studies show that inter-particle interaction can affect particle trajectories and particle deposition causing fouling in the microfilters used for metal working fluids (MWFs). Inter-particle interaction depends on various factors: particle geometry and surface properties, membrane pore geometry and surface properties, MWF’s properties and system operating conditions, etc. A mathematical model with a Langevin equation for particle trajectory and a hard sphere model for particle deposition has been used to study the effect of particle’s size, particle’s surface zeta potential, inter-particle distance, and shape of membrane pore wall surface on particle trajectory and its deposition on membrane pore wall. The study reveals that bigger particles have a lesser tendency to be deposited on membrane pore walls than smaller particles. The shape of the membrane pore wall surface can also affect the particle deposition behavior.

Metalworking fluids are a vital part of modern machining processes but have significant negative economic, health, and environmental impacts. In-process purification of these fluids by microfiltration has been shown to reduce these impacts. This research uses a two-stage computational modeling methodology to investigate how particles within the membrane are transported from the turbulent flow within the center of the tubular membrane to the laminar sub-layer near the membrane wall and finally into the membrane pores. A macro-model of the complete flow within the tubular membrane is used to determine the steady-state flow profile within 25 microns of the membrane surface. This flow profile is then used to develop a micro-model of the flow at the membrane wall using a flat-plate assumption. The micro-model includes individual pores randomly located and sized based on statistical analysis of alumina membrane surfaces. A 2 3 full factorial design of experiments was used with variables of cross-flow velocity, transmembrane pressure, and membrane resistance. The responses of effective filtration region and total mass flowing through the pores were analyzed. Based on the simulation results, recommendations are made for future membrane design to provide the most efficient transport of particles from the bulk into the pores.

Accelerated tool wear and tool breakage are significant problems in micro-machining processes such as micro-milling. Traditional flood cooling processes are unsuitable for micro-milling due to the excessive collision force between the fluid stream and the tool being large enough to affect the accuracy of the cutting process. In this research an atomization-based cooling and lubrication system is presented that delivers atomized cutting fluids to a micro-milling tool through the use of an original nozzle design based on two orthogonally-directed streams. The system and nozzle is used to investigate the relative importance of cooling and lubrication on micro-milling of 6061 T6 cold-rolled aluminum with a 0.508 mm diameter two-fluted end mill. Six cutting conditions are experimentally evaluated based on cutting forces and tool life. Lubrication is investigated through two concentrations (10% and 25%) of a semi-synthetic cutting fluid. Cooling is investigated through the use of atomized deionized water as well as dry cutting with cooling provided by a Ranque-Hilsch vortex tube. Dry cutting was used as a control. Statistical testing revealed the importance of lubrication relative to cooling when machining on the micro-scale as deionized water performed the worst of all tests conducted. Based on the experimental results, recommendations are made for the design of future micro-machining cooling and lubrication systems.

The micro-factory concept has gained wide support and acceptance based on the ability of small machine tools to accomplish the same tasks as traditionally sized machine tools while using a fraction of the space. Although it is frequently mentioned that a micro-factory is an energy saving endeavor, there is a dearth of hard data on how much energy is actually saved. The intent of this report is to quantify the difference in energy consumed in a micro-factory and a macro-factory though experimentation with a micro- and a macro-mill. This quantification allows for the potential of unit life cycle analyses to be performed in the future. A fluidic channel was machined in workpieces of aluminum and steel by both micro- and macro-mills under a variety of machining conditions and the recorded data has been analyzed to this end. The variables investigated were the spindle speed, the mill type, and the material the cutting process was performed on. The conclusions reached through experimentation were that the micro-mill used between 13.5% and 21.7% of the energy used for the macro-mill. Additionally the energy differences in climate control were investigated for comparable macro- and micro-factories. The mock macro-factory used for this analysis was three times the size of the micro-factory. Due to the larger size of the macro-building, the climate control energy usages were also about three times as high as in the micro-building.

Wind turbines have seen increasing use over the past decades as an alternative mode of energy production. One specific use of vertical axis wind turbines is for the powering of rural telecommunication towers. In this research a cradle-to-gate life cycle analysis is used to compare three different designs for a stackable, capped, Savonius-style vertical axis wind turbine blade capable of producing from one to three kilowatts. The analysis compares the energy consumed and carbon dioxide emissions from material production and manufacturing of two different aluminum blade designs and a polypropylene design each having the same energy generation capacity. Primary and secondary aluminum materials were included in the analysis. Life cycle inventories from two software programs were used and compared with values gleaned from published literature. The results of the analysis revealed that the least energy and carbon dioxide impact came from using a recycled aluminum design while the most was from manufacturing using primary aluminum.

Traditional flood cooling processes can cause problems in micromachining due to the collision force between the fluid stream and the tool being greater in magnitude than the cutting forces. The traditional processes produce insufficient cooling rates and are unable to effectively evacuate chips from the cutting zone. Atomization-based cooling addresses these issues through high evaporative cooling rates, low impact forces, and the use of a high velocity air stream to clear the cutting zone of chips. This paper presents a probabilistic model to determine the thickness of a microfilm forming on a rotating cylindrical surface, such as a microturning workpiece or a microendmill, and the relative importance of system parameters on film formation. The rate of microfilm formation is dependent upon droplet losses in the tube, at the nozzle, and the scatter of the atomized spray. Droplet diameters and Weber numbers in the tube and at the cylinder were experimentally determined and modeled as lognormally distributed. Parameters investigated in this model are fluid and mist properties (surface tension and droplet size) and system parameters (delivery tube air velocity, spray air velocity, spray geometry, cylinder diameter, and cylinder rotational velocity). A maximum film thickness effect was found for the variables of delivery tube velocity, droplet diameter, and surface tension with a value for each variable that provided a thickest film. As the variables increased or decreased from that value the film thickness decreased.

Microfiltration is an in-process recycling method that shows great potential to extend fluid life and reduce bacterial concentrations in synthetic and semi-synthetic metalworking fluids (MWFs). The primary problem facing this use of microfiltration is membrane fouling, which is the blocking of membrane pores causing reduced flux. In this paper a fluid dynamic model of partial and complete blocking in sintered alumina membranes is developed that includes hydrodynamic, electrostatic, and Brownian forces. Model simulations are employed to study the impact of electrostatic and Brownian motion forces on the progression of partial blocking. The simulations also examine the effects of fluid velocity, particle size, and particle surface potential. The inclusion of electrostatic and Brownian forces is shown to significantly impact the progression of the partial blocking mechanism. The addition of a strong inter-particle electrostatic force is shown to eliminate the partial blocking build-up of small particles due to the presence of the repulsive forces between the particles. As a result, the time to complete blocking of the test pore was lengthened, suggesting that flux decline is reduced in the presence of electrostatic forces. Brownian motion is shown to have a large impact at low fluid velocities. The most effective parameter set is a low fluid velocity, small particle sizes, high microemulsion surface potential, and high membrane surface potential.