Part Geometry Research Articles

The geometry of fault reactivation and uplift along the central part of the Maacama Fault Zone, Northern California Coast Ranges (USA)

Fault reactivation of bedrock structures in active fault zones influences stress state and earthquake rupture phenomena through the introduction of weak slip surfaces that impact fault zone geometry and width. Yet, geometric relationships between modern faults and older reactivated faults are difficult to quantify in rocks that have experienced multiple deformation episodes. We used new geologic mapping, geomorphic tools, and structural modeling to quantify rock uplift and subsurface fault geometry of the central part of the Maacama Fault Zone near Ukiah, California, USA, and the surrounding area. Results suggest that the northern Mayacamas Mountains are in a tectonically driven disequilibrium, with differential rock uplift focused on the western side of the range. Steeply east-dipping fault surfaces and splays characterize the geometry of the Maacama Fault Zone. We mapped two newly identified faults to the east of the main Maacama Fault, the Cow Mountain–Mill Creek Fault, and Willow Creek Fault, which align with a moderately east-dipping cluster of microseismicity between 4–10 km depth beneath the Mayacamas Mountains. Static stress modeling on the Maacama Fault Zone and newly identified faults to the east quantify slip tendency values of 0.5–0.4, which suggests that the faults are moderately to poorly suited for slip in the modern stress field and may be weak. We infer that modern uplift is driven by oblique reverse, up-to-the-east, dip-slip motion on the reactivated Cenozoic Cow Mountain–Mill Creek and Willow Creek Faults as material is advected through a restraining bend on the Maacama Fault. This study shows that reactivated bedrock faults increase the fault zone width and introduce fault surfaces that contribute a component of vertical deformation and uplift in major strike-slip fault zones. Deformation is accommodated on an interconnected network of new and reactivated faults that delineate a complex seismic hazard.

Interlayer-free laser coating of AISI H11 tool steel for H11/Cu composite material

Copper-based materials in combination with steels are of great interest for various applications in industry, such as tool manufacture, due to their high thermal conductivity. Additive manufacturing (AM) is beneficial for both tailored part geometry and customized material design. With laser-based AM, the copper-steel interface is highly prone to cracking. This study investigates a strategy of laser coating AISI H11 tool steel for a composite material consisting of AISI H11 tool steel and copper (H11/Cu) without using Ni-based interlayers. As an austenite stabilizing element, Ni dilution in H11 could lead to soft retained austenite, impeding wear resistance. The approach in this work employed presintering of tool steel powder to generate a porous H11 preform. Laser-based directed energy deposition (DED-LB/M) was used for coating H11 tool steel on the porous H11 preform followed by copper infiltration of the preform. The investigation of the effects of the main processing parameters: laser power, feed rate, and powder mass flow on the weld track geometry, clearly revealed different mechanisms when coating the porous preform compared to the conventional substrate. Defects at the coating/substrate interface such as cold crack formation were successfully avoided by adjusting the process parameters and process sequence. The developed processing strategy may in the future combine material extrusion of metals (MEX/M) and DED-LB/M to allow for intricate preform geometries and to generate H11 coatings on H11/Cu, respectively.

Generalized SmartScan: An Intelligent LPBF Scan Sequence Optimization Approach for Reduced Residual Stress and Distortion in 3D Part Geometries

Abstract Laser powder bed fusion (LPBF) is an additive manufacturing technique that is gaining popularity for producing metallic parts in various industries. However, parts produced by LPBF are prone to residual stress, deformation, cracks and other quality defects due to uneven temperature distribution during the LPBF process. To address this issue, in prior work, the authors have proposed SmartScan, a method for determining laser scan sequence in LPBF using an intelligent (i.e., model-based and optimization-driven) approach, rather than using heuristics, and applied it to simple 2D geometries. This paper presents a generalized SmartScan methodology that is applicable to arbitrary 3D geometries. This is achieved by: (1) expanding the thermal model and optimization approach used in SmartScan to multiple layers; (2) enabling SmartScan to process shapes with arbitrary contours and infill patterns within each layer; (3) providing the optimization in SmartScan with a balance of exploration and exploitation to make it less myopic; and (4) improving SmartScan’s computational efficiency via model order reduction using singular value decomposition. Sample 3D test artifacts are simulated and printed using SmartScan in comparison with common heuristic scan sequences. Reductions of up to 92% in temperature inhomogeneity, 86% in residual stress, 24% in maximum deformation and 50% in geometric inaccuracy were observed using SmartScan. An approach for using SmartScan for printing complex 3D parts in practice, by integrating it as a plug-in to a commercial slicing software, was also demonstrated experimentally, along with its benefits in significantly improving printed part quality.

Benefits derived from WASP (a Grasshopper plugin) to Design for Disassembly Principles in the Built Environment

Abstract Design for Disassembly (DfD, henceforth) is a way to improve the effectiveness of the disassembly process in built environments, and it mainly contains ten principles. Examples of the principles include deconstruction techniques; selected materials; reachable connections; utilizing connections with fewer bolts, screws, and nails; the straightforwardness of the structure and design; and versatility. On the other hand, the WASP plugin for Grasshopper (on Rhinocheros©) is a toolkit for discrete computational design to simulate the aggregation and assembly possibilities in the building system. This paper explores the integration of the WASP plugin within the context of DfD through three criteria: the aggregation processes of part geometries, connection locations, and their orientation toward the building elements. Design with discrete elements, which can be defined as shape grammars for building structure, is the primary approach for the joining behavior and detaching behavior of elements discussed in this paper. Also, this type of component-based design can optimize the geometry and data-driven generation of the structure. The design process in this way can be disassembly sequence planning and knowledge-based design by applying the design constraints. To illustrate the integration, research is conducted through WASP simulation in designing a traditional Iranian timber pavilion-inspired structure with a 3×3m footprint in a roof structure. The fusion of WASP and DfD represents a promising avenue for advancing circular design principles and achieving more sustainable, resource-efficient buildings. It is concluded from this study that WASP makes the aggregation simulation and assembly possibilities of the vertical and horizontal components in a building more accessible.

Interpass temperature impact on bead geometry of mild steel in wire-arc additive manufacturing

In wire-arc additive manufacturing (WAAM), melt pool dynamics produce variations in bead geometry that create undesired part geometries and can also lead to material defects. In the current state of the art, reducing melt pool and bead variation is still an aspect of WAAM that is underdeveloped. Several factors influence the bead geometry including the type of material that is being deposited and process inputs. In this study, ER70S-3 mild steel was deposited onto steel build plates using a cold metal transfer (CMT) deposition process. Varying plate preheat surface temperatures were used from ambient temperature to 300 °C using different welding travel speeds. To control build plate surface temperature, a preheat stage was designed and implemented to simulate different interpass temperatures. Beads were deposited and subsequently measured to determine their geometric properties such as bead height and bead width. Initial results indicate that as the preheat temperature increases, resulting bead height decreases, bead height variation decreases, and bead width increases. Initial microstructural data also indicates that as preheat temperature increases, the microstructure becomes more equiaxed with decreasing grain sizes.

Smart design and additive manufacturing of bending tools to improve production flexibility

For the automotive industry, especially on the part of Tier 1 and Tier 2 suppliers, the future will be about maintaining sovereignty in the form of technology openness and accelerating digitization. The product portfolio, which is generally passed on by OEMs to suppliers for production, often includes body parts that cannot always be manufactured economically with the prevailing production technology. The reason for this is a high diversity of model-variants, which requires smaller batches. To this end, highly flexible large-series production cells for body sheet components that can be scaled in all dimensions are being developed and tested. For the first time, they will make it possible to redesign the process planning in series production on a component-specific basis. The aim is to reduce production costs for new, geometrically different component variants. The basic components of the flexible manufacturing system are, firstly, new flexible forming technologies which have the potential to produce typical vehicle part geometries. Secondly, a process generator develops the corresponding production plan. A digital mapping of the manufacturing processes enables the selection of cost-, efficiency-, flexibility- and resilience-optimized production chains depending on the number of parts. Established manufacturing processes to produce car body components are supplemented in the cell by flexible processes such as 3D swivel bending. As a use case for flexible manufacturing, a concept for Rapid Tooling of 3D swivel bending tools is developed. In the flexible manufacturing system to be developed, a method of a standardized process sequence to produce forming tools within 24 h has been lacking to date. For this purpose, the concept of an automated design is being developed in which a reconfigurable tool body can be sliced into sheet metal stripes The active tool surface is additively manufactured after the tool has been packaged using LMD and adapted to individual requirements. The goal in the application of Rapid Tooling is to reduce lead times and development costs through a largely automated tool design and lead time-optimized manufacturing concept.

Iterative correction of robotic grinding using spatial feedback for precision applications

Since the advent of robots, many tasks that were originally performed by humans have now been tasked to industrial robots. From a manufacturing standpoint, robots have primarily been used in pick-and-place or other non-machining operations that require high repeatability. However, with the increasing availability of CAD/CAM software and the development of high-precision metrology, comes the opportunity to integrate robots into a wider variety of manufacturing processes through the use of feedback control. One such machining operation that is being explored is precision grinding of metal parts. Most other work in this area has focused on force regulation to improve grind quality; however, this paper takes a different approach. In this work, an Iterative Learning Control (ILC) algorithm is implemented to correct the geometric error directly by altering the toolpath trajectory. Specifically, in this framework, a conservative initial cutting trajectory is implemented using a 6-DoF robotic grinding system, and the resulting part geometry is measured via a high-precision laser scanner. Based on the resultant geometric error, the toolpath is corrected and then rerun on the part. This process is then repeated iteratively until sufficient accuracy is achieved. Due to the inability to replace material in overground regions, the controller is designed with an emphasis on reducing overshoot which cannot be corrected. The controller is experimentally validated by grinding an elliptical pocket which meets FAA specifications for corrosion removal in aircraft. The results showed that within seven iterations the entire error surface could be brought to a tolerance of ±0.150 mm for the given geometry.

Effect of varying part geometry and mold constraints on dimensional deviations of sand cast parts

Effect of varying part geometry and mold constraints on dimensional deviations of sand cast parts

Numerical and experimental investigation of extrusion processes from coil

The use of coil material as semi-finished product in sheet-bulk metal forming (SBMF), offers the possibility to use high-speed presses and thus to achieve high output quantities. However, compared to industrially established forming of pre-cut blanks, the reduced geometric accuracy of the parts due to the asymmetrical material flow represents a challenge. Against this background, the aim of this study is to gain an in-depth knowledge on the influence of the process setup on the material flow direction and on the forming of geared functional parts. A combined numerical-experimental approach of each a lateral and a backward extrusion process of a DC04 sheet metal ( t0 = 2 mm) is applied for a fundamental process analysis. For this purpose, process-dependent causes for the asymmetric part forming are analyzed by means of material flow simulations. Subsequently, the numerical results are verified experimentally in terms of the part geometry, the process force and grain structural changes. Based on the numerical and experimental results, cause-effect relations between material flow, part accuracy and tool load are derived. In addition, the transferability of the causes of the asymmetric material flow to processes with different primary material flow directions and part geometries is verified. The findings facilitate the future counteraction of asymmetrical material flow in SBMF from coil, which in turn leads to enhanced component quality.

Formation of a uniform velocity profile in the section of a profiled channel of a reference installation

The velocity profiles in gravity and pressure channels of flow diverters in reference installations in the field of liquid flow and quantity measurements are studied. The design shortcomings of reference installations that do not allow obtaining a flow velocity profile close to uniform in the sections of pressure nozzles over a long period of reference installation operation are described. It is shown that the placement of various straightening devices in the profiled channels and pressure nozzles of flow diverters of reference installations does not lead to obtaining a flow velocity profile close to uniform. An approach to profiling the gravity channel of the flow diverter is proposed, which allows obtaining a velocity profile close to uniform. An experimental justification of the hydraulic efficiency of the geometry of the flow part of the profiled channel of the flow diverter of the EU-3 reference installation from the State Primary Special Standard of Units of Mass and Volume of Liquid in a Flow, Mass and Volume Flow Rates of Liquid GET 63-2019 is presented. The influence of the flow velocity profile shape in the section of the profiled channel of the flow switch and the stability of the main hydro- and thermodynamic parameters of the water flow (flow rate, absolute pressure and temperature) in the pressure pipeline on the metrological characteristics of the reference installation is substantiated. Experimental studies of the velocity profile of the free-flow water flow in the section of the profiled channel are performed using high-speed total pressure meters and Pitot tubes. Close to uniform water flow velocity profiles in the section of a profiled channel were obtained for free flow in the range of investigated Reynolds numbers Re=(35...300)·103. The results of maintaining the stability of the specified value of the mass flow rate of water over a long period of time are presented. The equations for calculating the mass of water during transient processes are written down, taking into account the change in the thickness of the water flow and flow rate from zero to specified values. The presented approach and the obtained results are useful for manufacturers of reference installations and are relevant in the design, creation and modernization of profiled channels of flow switches of reference installations.

3D-Printed Phenylboronic Acid-Bearing Hydrogels for Glucose-Triggered Drug Release.

Diabetes is a major health concern that the next-generation of on-demand insulin releasing implants may overcome via personalized therapy. Therein, 3D-printed phenylboronic acid-containing implants with on-demand glucose-triggered drug release abilities are produced using high resolution stereolithography technology. To that end, the methacrylation of phenylboronic acid is targeted following a two-step reaction. The resulting photocurable phenylboronic acid derivative is accordingly incorporated within bioinert polyhydroxyethyl methacrylate-based hydrogels at varying loadings. The end result is a sub-centimeter scaled 3D-printed bioinert implant that can be remotely activated with 1,2-diols and 1,3-diols such as glucose for on-demand drug administration such as insulin. As a proof of concept, varying glucose concentration from hypoglycemic to hyperglycemic levels readily allow the release of pinacol, i.e., a 1,2-diol-containing model molecule, at respectively low and high rates. In addition, the results demonstrated that adjusting the geometry and size of the 3D-printed part is a simple and suitable method for tailoring the release behavior and dosage.

Thermal modeling of variable process parameter effects in powder bed fusion using electron beam

Purpose This study aims to develop a novel thermal modeling strategy to simulate electron beam powder bed fusion at part scale with machine-varying process parameters strategy. Single-bead and part-scale experiments and modeling were studied. Scanning strategies were described by the process controlling functions that enabled modeling. Design/methodology/approach The finite element analysis thermal model was used along with the powder bed fusion with electron beam experiments. The proposed strategy involves dividing a part into smaller sections and creating meso-scale models for each subsection. These meso-scale models take into consideration the variable process parameters, including power and velocity of the moving heat source, during part building. Subsequently, these models are integrated to perform partscale simulations, enabling more realistic predictions of thermal accumulation and resulting distortions. The model was built and validated with single-bead experiments and bulky parts with different features. Findings Single-bead experiments demonstrated an average error rate of 6%–24% for melt pool dimension prediction using the proposed meso-scale models with different scanning control functions. Part-scale simulations for three different geometries (cantilever beams with supports, bulk artifact and topology-optimized transfer arm) showed good agreement between modeled temperature changes and experimental deformation values. Originality/value This study presents a novel approach for electron beam powder bed fusion modeling that leverages meso-scale models to capture the influence of variable process parameters on part quality. This strategy offers improved accuracy for predicting part geometry and identifying potential defects, leading to a more efficient additive manufacturing process.

An experimental validation study of a numerical modeling approach to predicting post-consolidation dimensions of thermoplastic composites

Consolidation is an important step in the processing of thermoplastic unidirectional (UD) tapes, as it creates a bond between individual tapes to form a semi-finished sheet: The tape stack is first heated and then cooled, both while being subjected to pressure. If the material is in a soft or even molten state and its flow unrestricted, this compression can result in squeeze flow, the direction of which is determined by the fibers of the tapes. Extensive squeeze flow not only results in significant changes in part geometry to the point where it may fail to meet design and application specifications but can also lead to severe distortion and residual stresses. To address this, we developed a model that, given the process parameters and fiber orientation, predicts the effects of squeeze flow. Based on experimental data on UD polycarbonate tapes with 44% carbon fibers by volume consolidated at various process settings, this paper presents the validation of the model for industrial application. We found that at low heating temperatures, where the matrix viscosity is too high and prevents the material from flowing, the simulation results deviated markedly from the experimental data. With these temperatures excluded, however, the overall deviation of the model was 8.7% for thickness change and 5.3% for area change.

Very high cycle fatigue characteristics of laser beam powder bed fused AlSi10Mg: A systematic evaluation of part geometry

This study explores the influence of geometry and part size on defect distribution, melt pool size, and mechanical characteristics in laser beam powder bed fused (LB-PBF) AlSi10Mg. Five distinct geometries—hourglass, small rod, small block, large block, and large rod—were fabricated under identical process parameters. Fully reversed ultrasonic fatigue testing, operating at a frequency of 20 kHz, was conducted to assess the very high cycle fatigue properties. The findings indicated that part geometry had a major impact on the fatigue properties of the material in the very high cycle fatigue regime. Specimens machined from large rods and large blocks had the lowest porosity and highest fatigue resistance. Microstructural analysis indicated that hourglass, small rod, and small block specimens had shallower melt pools and overlap depths compared to other geometries. This observation suggests a higher cooling rate in specimens with smaller cross-sectional areas, leading to the increased presence of entrapped gas pores and a lack of fusion defects. Understanding the relationship between part geometry and fatigue properties in LB-PBF components offers insights for optimizing design and manufacturing processes in additive manufacturing applications.

Tool Path Strategies for Efficient Milling of Thin-Wall Features

The milling of thin-wall geometries has been a challenge due to inherent chatter vibrations and workpiece deflections. Moreover, tool path generation strategies in CAD-CAM systems are not able to fully address all such concerns. The objective of this study is to demonstrate potential 5-axis milling tool path strategies, which do not exist in the conventional tool path generation. The demonstration is performed for increased efficiency in milling of thin-wall features considering the main limitation of chatter. The effects of varying workpiece dynamics on milling stability are shown in case studies through simulations and cutting experiments. Based on the simulation results, tool path strategies are developed. The effect of tool path generation and the relation to parameter selection are highlighted. Most of the discussion relies on previously reported experimental results. The results showed that by tailoring the tool path considering the concerns and limitations associated with thin-wall part structure and geometry, it is possible to increase productivity by at least two folds.

Enhancing mechanical performance in SLS-printed PA12-slate composites through amino-silane treatment of mineral waste

The SLS additive manufacturing industry enables the development of products for diverse applications with distinct properties due to its excellent surface finish and ability to create varied part geometries, but it consumes high-performance materials with high acquisition costs. An extensive quarrying of stone leads to the accumulation of mineral residues, posing environmental hazards by contaminating soil and water when disposed of in landfills. The primary objective of the study was to incorporate mineral waste into the SLS technique and investigate the influence of its addition, along with a silane-based chemical treatment, on the mechanical performance of polymer-mineral composites (PA12-slate). Additionally, the feasibility of producing a highly loaded printed prototype, employing 50 wt% of mineral waste, was examined. Samples of PA12, PA12 blended with 50 wt% slate waste, and slate waste treated with silane underwent fabrication via selective laser sintering (SLS) and subsequent mechanical characterization, including tensile, flexural, and compressive tests. Additionally, the samples underwent accelerated aging using a QUV weathering tester, followed by mechanical characterization. The geometric accuracy, stability, and processing feasibility of these formulations were evaluated through SLS-printed composite prototypes utilizing PA12_50Sla_Si. It was found that the addition of 50% of slate to the PA12 presented mechanical properties decreasing compared to the printed PA12 only. However, an increase was verified when using silane-induced mineral bonding. The incorporation of mineral agents and silane enhanced the resistance of PA12 to aging. However, after aging, both tensile and flexural strength decreased across all printed samples. Nonetheless, this study showcased the feasibility of producing complex PA12-slate waste specimens containing up to 50 wt% of mineral waste using the SLS printing technique. Therefore, SLS presents itself as a viable means of adding value to this mineral waste.

Experimental investigations on the formation mechanisms of shrink lines in powder bed fusion of metals using a laser beam

The powder bed fusion of metals using a laser beam enables the tool-free fabrication of complex part geometries with merging areas and rapid cross-sectional changes. Together, these geometry features represent a structural transition leading to the formation of shrink lines. These notches on the surface of the part reduce the dimensional accuracy and the fatigue resistance. Shrink lines arise in various materials, with the dimensions of the shrink line depending on the geometric design. The formation mechanisms and influencing parameters of shrink lines have not been investigated yet. This paper demonstrates the extent of influence of the part geometry on the shrink line formation, which was quantified by varying the design of a representative structural transition. In addition, the positions of the specimens on the build platform and the scanning strategy were varied for deriving a cause-effect relationship using process monitoring. The results demonstrated that the shrink line formation was mainly caused by a local overheating at the structural transition and the global cooling behavior. The radius at the structural transition indicated the most significant impact among the investigated geometric parameters. The shrink line dimensions depended significantly on the orientation of the specimens on the build platform and the local scanning strategy applied at the height of the structural transition. The results can be used to reduce shrink lines by re-designing the part and to adjust the manufacturing strategy for structural transitions.

Effect of Printing Parameters on Mesoscale Geometry of 3D-Printed Parts through a Hybrid Experimental and Numerical Approach

Effect of Printing Parameters on Mesoscale Geometry of 3D-Printed Parts through a Hybrid Experimental and Numerical Approach

First Approach in Analysis of Tool Wear When Milling Additive Manufacturing (AM) Parts

Wire arc additive manufacturing (WAAM) and laser-based powder bed fusion (L-PBF) are additive manufacturing (AM) processes that allow the manufacturing of complex part geometries. The manufacturing of AM parts does not result in high-quality functional surfaces; therefore, postprocessing such as milling is usually required. For L-PBF parts, the support structures and, for WAAM parts, the undulating surface are usually removed after AM processes. These two application-related cases are investigated in this work, with the conclusion that support structure milling and the milling of the surface of WAAM parts lead to the dimensionally increased wear of milling tools in comparison to milling of solid material.

Injection Moulded Part Analysis by Alignment of Simulated and Referent Part Geometry

Warpage of the injection moulded parts is one of the most common defects after demoulding, which is intensively present in thin-walled moulded parts or parts with non-uniform wall thickness. The level of the warpage can be reduced by optimizing the mould tempering system in the phase of mould design, by optimizing the injection moulding parameters and recently by optimizing the shape of the mould cavity elements geometry – so-called inverse contouring. Computer simulation of injection moulding process can show the level of moulded part warpage after ejection from the mould, but it will not allow detailed measuring of critical moulded part measures deviations. Detailed analysis and prediction of the critical moulded part dimensions can be performed by aligning of the deformed moulded part design obtained with computer simulation, with moulded part reference CAD geometry. This paper shows the main steps and an example of the geometry aligning process for a specific thermoplastic part.