Development of CAM System for 3D Surface Machining With CNC Lathe (Tool Path Generation Considering Acceleration)

This study developed a method called non-axisymmetric curved surface turning (NACS-Turning) for a CNC lathe composed of a turning axis and two translation axes. The NACS-Turning method controls the three axes synchronously. This new machining method can reduce the lead time for non-circular shapes such as cam profiles or pistons for internal combustion engines. In our previous report, we presented an outline of a machining principle and a CAM system for NACS-Turning. However, at the same time, we found the problem that the X-axis slide exceeds the allowable acceleration. Therefore, it is preferable that the acceleration is verified during the cam application, and the tool path is generated within the allowable acceleration range. Therefore, this paper first describes the determination method of machinable conditions for NACS-Turning in the cam application. Next, based on the result, relationships between the acceleration of the X-axis slide and machining conditions are clarified. Finally, the experimental procedure showed that our proposed method does not exceed the allowable acceleration of the X-axis slide.

Transient Analysis of In-Plane and Through Thickness Flow During VARTM in the Presence of HPM

Modeling resin flow for a Vacuum Assisted Resin Transfer Molding (VARTM) process involves developing an approach for coupled flow-compaction, porosity-permeability, resin-cure and stress-development phenomena. In the present work, a modified transient incompressible resin flow model has been developed for VARTM without considering the constant flow rate assumption. The use of High Permeability Medium (HPM) during VARTM results in a through-thickness flow in addition to in-plane flow developing due to the pressure gradient. Results have been validated with existing literature. Fill time comparisons for with and without HPM cases have been presented. Some preliminary results of 2D plane flow have also been obtained which show promise in replicating the physics of vacuum assisted resin infusion composite manufacturing process.

Crystallization in Nano-Confinement Seeded by a Nanocrystal: A Molecular Dynamics Study

Seeded crystallization and solidification in nanoscale confinement volumes has become an important and complex topic in nanomanufacturing. Due to the complexity and limitations in observing nanoscale crystallization, computer simulation can provide valuable details for supporting and interpreting experimental observations. In this article, seeded crystallization from nano-confined liquid, as represented by the crystallization of a suspended gold nano-droplet seeded by a pre-existing gold nanocrystal seed, was investigated using molecular dynamics simulations in canonical (NVT) ensemble. We found that the crystallization temperature depends on nano-confinement volume, crystal orientation and seed size as explained by classical two-sphere model and Gibbs-Thomson effect.

A FEA Simulation Model for Thin-Walled C-Section Composite Beam Assembling With R-Angle Deviation

There are unavoidable deviations, such as shrinkage and distortions, in the composite detail parts production due to the complexity of composites fabrication. Interests in the assembly analysis of composite beams have led to a need for more accurate analysis especially in the case of fabrication deviations. This work proposes a numerical finite element model of thin-walled C-section composite beam with R-angle deviation for assembling. The rule of Hashin failure combined with cohesive element is applied to study the mechanical performance of the fiber and matrix (implemented as user subroutine UMAT in ABAQUS) while positioning and clamping. Tension and compression tests are carried out based on available standards to determine the C-section beam behavior under load. The testing data validates the proposed numerical model. The numerical model captures the experimentally obtained results with minimal error, and predicts the failure modes successfully. The proposed model allows to determine accurately the first failure location and the associated load level. It will enhance the understanding of the composite components pre-loading analysis, and help systematically improving the composites assembling efficiency in civil aircraft industry.

Functional Prototyping and Tooling of FDM Additive Manufactured Parts

In this paper, we present two additive manufacturing applications: (1) vacuum forming tooling using AM; (2) rocket functional prototype using AM for computational fluid dynamics (CFD) and wind-tunnel testing. The first application shows how additive manufacturing (AM) facilitates the manufacture of vacuum formed parts, which allows such parts to be easily produced especially in the manufacturing sector. We show how combining the advantages of the CAD and FDM technology, vacuum forming can be completed quickly, efficiently and cost effectively. The paper shows that using modified build parameters, the tools FDM creates can be inherently porous, which eliminates the time needed for drilling vent holes that are necessary for other vacuum forming tools, while improving part quality with an evenly distributed vacuum draw. Using SolidWorks CAD software, the model of the tool is created. The STL file is exported to the Insight software, and we present how the Tool Paths Custom Group feature is applied to optimize the tool-paths file and then sent to the FDM system that prints the tooling from ABS engineering thermoplastic. The tooling is then used in the Formech 686 manual vacuum forming machine to produce the vacuum formed part. The second application shows how additive manufacturing (AM) has been applied to producing functional model for wind–tunnel testing, as well as providing computational fluid dynamics (CFD) tool for comparing results obtained from the wind-tunnel testing. The present work is focused on applications of FDM technology for manufacturing wind tunnel test models. The CAD model of a rocket was analyzed for its aerodynamic properties and its functional prototype produced using AM for use in wind–tunnel testing so as to verify and tune the aerodynamic properties. Initial wall conditions were defined for the rocket in terms of the air velocity. The flow simulation was carried out and the goals examined are the velocity and pressure fields around the rocket model. The paper examines some practical issues that arise between how the model geometry for CDF process differs from that that of the FDM process. Consequently, we show that AM-based fused deposition modeling (FDM) technology is faster, less expensive and more efficient than traditional manufacturing processes for vacuum forming and for rapid prototyping of function models for wind-tunnel applications.

Influence of Hard Turning on Microstructure Evolution in the Subsurface Layers of Inconel 718

This study investigated the effects of semi finish, finish and critical finish machining parameters on the microstructural evolution of subsurface layers in Inconel 718. In order to assess the microstructural evolution in the subsurface layer following machining, advanced characterization methods including opto-digital microscopy, X-ray diffraction and nanoindentation were used. Results showed that friction between the tool and the workpiece during machining lead to microstructural changes such as hardness enhancement on the surface, and softening on the subsurface. It was also observed that damage in the machined surface is related to the presence of defects such as cracks, cavities and carbide detachment from the surface. Finally, residual stress measurements revealed that, within the investigated parameters, the cutting speed has the most significant effect on surface integrity.

Algorithm for Detecting and Solving the Problem of Under-Filled Pointed Ends Based on 3D Printing Plastic Droplet Generation

In this paper the problem of under-filled pointed ends is introduced and mathematically defined. To tackle this problem, we present a new algorithm that detects and fills the critical areas, which arise at the 3D printed plastic parts. While printing the contours and/or infill lines, due to the limitations based on the width of the extruded material, narrow edges and pointed ends remain improperly filled. This eventually results in 3D printed objects with the final geometry that differs greatly from the initial geometry. This paper presents the fundamentals for solving the problem of 3D printing of geometries which contain narrow pointed ends. The critical area of the pointed ends is mathematically defined and, depending on the angle, the formulae for the calculation of under-filled and over-filled areas are given. The newly developed algorithm, based on the 3D Printing plastic droplet generation process, assures that the droplets of the repeating contours are placed at the edges of the contour-segments and by that minimises the potential under-fills. Furthermore, an additional number of droplets is defined, that are either printed in or removed from the under-filled areas in the angle bisector. The proposed algorithm is applied on parts, whose geometry describes pointed ends. The final 3D printed parts are very appealing and their shape resembles the original geometry more than the final shape of the parts without applying the algorithm.

Direct Contact Heating for Hot Forming Die Quenching

Most hot forming lines use slow, energy-intensive roller hearth furnaces to austenitize boron steel “blanks”. This paper describes an alternative heating technology in which blanks are austenitized by bringing them into contact with a hot monolith. The austenitizing temperature was reached in less than 30 seconds, and subsequent material characterization tests on oil-quenched blanks confirm that a fully martensitic structure is formed, and that the hardness and yield strength are comparable to furnace-treated samples. An Al-Si coating is typically used to prevent the oxidation and decarburization of the blanks within the furnace; preliminary tests found that the coating adheres to the monolith, impeding blank transfer and damaging the Al-Si-Fe ternary coating. Five interchangeable striking surfaces were assessed to see if they were less prone to adhering to the molten Al-Si coating.

Effect of Tool Kinematics on the Drilling Forces and Temperature in Low Frequency High Amplitude Vibration Assisted Drilling

Defects associated with drilling of fiber reinforced polymers (FRPs) are of major economic and safety concerns for aerospace manufacturers. Delamination of layers and thermal damage of the matrix are the most critical defects associated with drilling of FRP laminates, which can be avoided by keeping the drilling forces and temperatures below some threshold levels. Vibration-assisted drilling (VAD) is an emerging drilling process that uses intermittent cutting to reduce the drilling forces and temperatures, and achieve easier chip removal compared to conventional drilling. In this paper an extensive experimental study has been conducted to provide insight into the effect of the tool kinematics corresponding to the VAD parameters (speed, feed, frequency and amplitude) on the geometry of the formed chip determined by the intersection of the trajectories of the cutting edges as well as on the drilling forces and temperature. The combinations of the VAD parameters used in this study were selected from ranges of speeds 6,000 rpm to 12,000 rpm, feeds 0.05 mm/rev to 0.15 mm/rev, frequencies 30 Hz and 60 Hz, and amplitudes 40 μm to 400 μm. The Amplitude and feed were found to have the most dominant effect on the VAD forces, while the feed and speed had the dominant effect on the VAD temperatures. The thermal performance of the VAD process was found to be enhanced by the formation of vortices in the air gap created by the separation between the tool and the machined surface, which is mainly controlled by the feed and the rotational speed of the tool.