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In this paper, a permeability measurement method using hybrid fiber preforms is presented. The hybrid fiber preform can be composed of different fiber mat types, different numbers of fiber mats of the same type, or both. The computational procedure for permeability based on flow front location and flow time data was derived. This approach was validated by both simulation and experimental studies. The results show that by using this method, permeability values of different fiber mat types or the relationship between permeability and fiber volume fraction (porosity) can be obtained through a single experiment. This permeability measurement method based on hybrid fiber preforms yields compatible measurement accuracies while significantly improving the measurement efficiency. It provides a fast, accurate, and easy-to-use approach for permeability characterization, which is of great significance for the integrated composite product and process development. In this paper, a permeability measurement method using hybrid fiber preforms is presented. The hybrid fiber preform can be composed of different fiber mat types, different numbers of fiber mats of the same type, or both. The computational procedure for permeability based on flow front location and flow time data was derived. This approach was validated by both simulation and experimental studies. The results show that by using this method, permeability values of different fiber mat types or the relationship between permeability and fiber volume fraction (porosity) can be obtained through a single experiment. This permeability measurement method based on hybrid fiber preforms yields compatible measurement accuracies while significantly improving the measurement efficiency. It provides a fast, accurate, and easy-to-use approach for permeability characterization, which is of great significance for the integrated composite product and process development. [ABSTRACT FROM AUTHOR]

This paper presents a study on dimensional variations and tolerance analysis and synthesis for polymer matrix fiber-reinforced composite components and assemblies. A composite component dimensional variation model was developed with process simulation based on thermal stress analysis and finite element analysis (FEA ). Using the FEA-based dimensional variation model the deformations of typical composite structures were studied and the regression-based dimensional variation models were developed. The regression-based dimensional variation models can significantly reduce computation time and provide a quick design guide for composite products with reduced dimensional variations. By introducing a material modification coefficient, the comprehensive regression models can handle various fiber and resin types and stacking sequences, which eliminates the complicated, time-consuming finite element meshing and material parameter defining process. A structural tree method (STM) was developed for rapid computation of composite assembly dimensional variations resulting from deformations on individual components, as well as the deformation of composite components with complex shapes. With the STM and the regression-based dimensional variation models, rapid design optimization was conducted to reduce the dimensional variations of composite assemblies. Cost-tolerance functions were developed using a fuzzy multiattribute utility theory based cost-estimation method. Based on the developed dimensional variation and cost-tolerance models, composite assembly tolerance analysis and synthesis were performed in this study. The exploring research work presented in this paper provides a foundation for developing practical and productive dimensional control techniques for composite products. [ABSTRACT FROM AUTHOR]

Optimizing the milling process requires a priori knowledge of injury process variables. However, the ability to include both milling stability and accuracy information is limited because current methods do not provide simultaneous milling stability and accuracy predictions. The method described within this paper, called Temporal Finite Element Analysis (TFEA), provides an approach for simultaneous prediction of milling stability and surface location error. This paper details the application of this approach to a multiple mode system in two orthogonal directions. The TFEA method forms an approximate analytical solution by dividing the time in the cut into a finite number of elements. The approximate solution is then matched with the exact solution for free vibration to obtain a discrete linear map. The formulated dynamic map is then used u, determine stability steady-state surface location error, and to reconstruct the time series for a stable cutting process. Solution convergence is evaluated by simply increasing the number of elements and through comparisons with numerical integration. Analytical predictions are compared to several different milling experiments. An interesting period two behavior, which was originally believed to be a flip bifurcation, was observed during experiment. However, evidence is presented to show this behavior can be attributed to runout in the cutter teeth. [ABSTRACT FROM AUTHOR]

With society focusing more and more on environmental issues, the recycling of materials of all types has become an important concern. As a result of previous processing and usage, the properties of recycled materials are often significantly inferior when compared to their unrecycled counterparts. Recycled polymeric materials, for example, have lowered molecular weights caused by previous thermal and/or shear histories. Thus, the scope of application for recycled materials has traditionally been very limited. With the aid of a new processing concept known as vibration-assisted injection molding (VAIM), the mechanical properties of products containing recycled polymeric materials could be dramatically improved. The current paper presents the results of an initial experimental investigation into the application of VAIM for recycled polystyrene (Recycled-PS) products. A number of recycled/new material blends were studied, and in all cases significant product mechanical property enhancements were realized through the use of VAIM. It was concluded that VAIM molded products containing as much as 50% low-grade recycled material could be made stronger than products made using traditional molding with 100% new polymer. Detailed results are presented in the paper, along with some insight into the likely fundamental mechanism underlying the utility of the VAIM technique. [ABSTRACT FROM AUTHOR]

This paper discusses the microdeposition technologies used in the fabrication of meso- and microscale structures. The ability to process a wide range of materials and the flexibility to build functional and geometrically complex structures in meso- and microscale gives the microdeposition method some advantages over micromachining or lithography methods investigated extensively in the past In this paper work on deposition technology is reviewed, including material, supply of material, powder flow rate, and manipulation of particles and microdeposition technologies. The advantages and disadvantages of each technology are summarized at the end of the paper. [ABSTRACT FROM AUTHOR]

Quality control and metrology are critical to improved productivity and yield in MEMS design and production. This paper presents a micrograting interferometer for use in measuring MEMS devices, The sensor is also capable of making dynamic measurements, qualifying the functionality of the MEMS devices. The system employs a phase sensitive diffraction grating for interferometric axial resolution and a microfabricated lens for improved lateral resolution. The microinterferometer is capable of array implementation and can be used to increase the yield of MEMS manufacturing processes. The results generated by a single microinterferometer show good correlation with both analytic models and measurements of the MEMS devices by other metrology tools. The microinterferometer enables measurement of steady state vibration of MEMS devices as well as the development of surface vibration profiles. Initial results presented in this paper also demonstrate the ability to measure quantities such as part surface curvature, as well as reduce low frequency vibrational noise. The use of a deformable diffraction grating is proposed to further enhance the sensor's capabilities. [ABSTRACT FROM AUTHOR]

This paper discusses the development of an enhanced, static model of chip formation in micromilling processes that is able to describe the intermittency of the chip formation observed at low feeds per tooth due to the dominance of the minimum chip thickness effect Experimental analyses demonstrate the validity of the proposed model by verifying the level of periodicity in the cutting forces present at various feeds per tooth. A key finding of this study is the identification of a local maximum in the radial thrust forces in the micromilling process during the noncutting regime, at feeds per tooth that are of the order of the minimum chip thickness. To overcome the challenges in the direct measurement of the minimum chip thickness, this paper presents a method for estimating the minimum chip thickness of various combinations of tools and workpiece materials based on easily attainable cutting-force data. A discussion on the selection of process parameters to avoid intermittent chip formation is also presented. [ABSTRACT FROM AUTHOR]

Optical fibers are drawn from preforms (fused silica glass rods) typically made up of two concentric cylinders (the core rod and the clad tube), which are usually joined in a separate fusion process. The setup time and hence manufacturing cost can be significantly reduced if the two cylinders can be joined in the same furnace in which the fiber is drawn. A good understanding of the transient temperature distribution is needed for controlling the feed rate to avoid thermally induced cracks. Since direct measurement of the temperature fields is often impossible, the geometrical design of the preform and the control of the feed rate have largely been accomplished by trials-and-errors. The ability to predict the transient temperature distribution and the thermally induced stresses will provide a rational basis to design optimization and feed rate control of the process. In this paper we present an analytical model to predict the transient conductive-radiative transfer as two partially joined, concentric glass cylinders with specular surfaces are fed into the furnace. Finite volume method (FVM) is used to solve the radiative transfer equation (RTE). The specular surface reflectivity is obtained by the Fresnel's law and the Snell's law. The boundary intensities are obtained through the coupling of the interior glass radiative transfer and the exterior furnace enclosure analysis. The model has been used to numerically study the transient conductive-radiative transfer in the advanced melting zone (AMZ) of an optic fiber drawing process. This problem is of both theoretical and practical interest in the manufacture of optical fibers. The computational method for the radiation transfer developed in this paper can also be applied to the simulation of the fiber drawing process and other glass-related manufacturing processes. [ABSTRACT FROM AUTHOR]

Particleboard panels are widely utilized as a raw material in the wood processing industry. It ends up as furniture, cabinets, and other industrial products. One of the problems particleboard mills face concerns the surface quality of their boards. As the demands of customers become more precise, very thin overlays are becoming more popular. Thus the problem of surface quality control and classification is clearly identified. In this paper, a particleboard surface-roughness classification system is modeled, simulated, and implemented. The particleboard model is based on the characterization of surface anomalies (pinholes. sander streaks, and grooves). Furthermore, an optical stylus surface-roughness measurement system is also modeled in order to determine whether it can be used w characterize a particleboard ‘on-ine.’ A classification algorithm is proposed to serve as an aid to the quality control operator. Simulation results are presented illustrating the change of surface roughness with increasing amounts of surface anomalies. A classification algorithm ix used to sort the simulated panels into different classes. A trial bench test using 225 panels is made to determine the applicability of this system to the industrial context. [ABSTRACT FROM AUTHOR]

Remanufacturing offers the potential for simultaneously recovering the economic value of manufactured components and improving the environment. Some design features make remanufacturing less expensive and/or increase the proportion of components that can be remanufactured. For example, sacrificial components can be used to protect key parts from wear. However, trade-offs are sometimes involved, and product designers need tools to support design for remanufacturing. This paper presents models for estimating the costs and environmental impacts of employing sacrificial components (cylinder liners) in engine blocks. These models are incorporated into a spreadsheet-based design decision tool. Three illustrative examples demonstrate that (1) remanufacturing lowers overall costs when two life cycles are considered. (2) sacrificial cylinder liners should be employed for small (2 L) engines, and their superiority increases with multiple remanufacturing cycles, and (3) for large engines (5.3 L) using cylinder liners is equally preferred to not using them, with respect to both overall cost and environmental impacts. [ABSTRACT FROM AUTHOR]

This paper presents a comparative study of the AC and MFDC resistance spot welding process. Both experiments and finite element simulation were conducted to compare the weld size and energy consumption. The experiments were performed on two identical spot welding machines, one with a single phase ac and the other with a mid-frequency DC weld control. The machines were instrumented such that both the primary and secondary voltage and current signals could be collected for energy calculation. The finite element simulation model was developed to understand the underlying mechanisms of the difference between the ac and MFDC processes. The effect of the current waveform was investigated by using the actual process measurements as an input to the simulation model. It is shown that the MFDC process generally produces larger welds than the AC process with the same root-mean-square welding current. However, this difference is more prominent when the welding current is relatively low. Overall, the AC welding process consumes more energy to make a same sized weld than the MFDC process. The larger the welding current is used, the less efficient the AC welding process will become. The differences between the two welding processes are caused by the contact resistance behavior and the electrical inductance in the AC welding process. [ABSTRACT FROM AUTHOR]

This paper deals with the conceptual design of a novel four-degree-of-freedom (dof) modularized robot which is composed of a 2-dof parallel mechanism plus a 2-dof rotating head attached to the moving platform. Patented with the name Bicept, the robot is the two-dimensional version of the Tricept robot and is designed as a reconfigurable module that can readily be integrated with 1-dof feed mechanism or a fixed base in order to form a set of reconfigurable robots with parallel-serial architecture. The dimensional synthesis of the 2-dof parallel mechanism as a component of the Bicept robot is also carried out by solving a one-dimensional nonlinear equation associated with the strut-length constraint. The dimensional parameters corresponding to various width-height ratios of the work space are obtained via examples. [ABSTRACT FROM AUTHOR]

In a number of manufacturing processes—tooling installation, calibration, and maintenance--guarantee the precision of fixtures and play important roles toward the overall quality of products. Recently, a new type of measurement equipment called a ‘laser tracker’ was developed and utilized for assembly fixture calibration to shorten calibration time and improve the accuracy of the currently used theodolite systems. Though calibration of the assembly fixture is critical for product quality, as such, calibration time creates a significant burden for productivity of multistation assembly processes. In order to shorten calibration lead time, the number of necessary setups, determined by visibility analysis, needs" to be minimized. This paper presents a screen space transformation-bated visibility analysis that allows minimizing the number of setups. The screen space transformation is applied to transform the visibility problem from three- to two-dimensional space, thus, efficiently solving the visibility problem. A case study illustrates the procedure and verifies the validity of the proposed methodology. This methodology can be applied not only for manufacturing processes, such us in-line fixture calibration, but also toward analysis and optimization of AGVs, robot navigation systems, and building security. [ABSTRACT FROM AUTHOR]

A fast temperature ramp of rapid thermal processing (RTP) with convective cooling used w shorten the cooling time for the wafer is presented in this paper. Based on thermal and stress analyses, the behavior of the highly coupled physics in RTP, such as radiative heat transfer, transient flow, and thermal stress is studied in detail. From simulation results of the flow field, a large recirculation cell between the wafer edge and the chamber wall is predicted and the effect of buoyancy on the behavior of the flow field is examined. Since the buoyancy-induced recirculation aggregates thermal nonuniformity due to edge effect. a guard ring is then suggested to be placed at the edge of the wafer to reduce the heat loss from the wafer edge and reflect the radiative energy back into the wafer during the cooling process. Furthermore, a large inlet gas mass flow rate is found to suppress the recirculation and shorten the cooling time. However, a fast convective cooling rate would result in a significant temperature difference between center and edge of the wafer, thus causing material failure due to an increase of thermal stresses. [ABSTRACT FROM AUTHOR]

A scratch inetersection based material removal mechanism for CMP processes ix proposed in this paper. The experimentally observed deformation pattern by SEM and the trends of the measured force profiles (Che et al., 2003) reveal that, for an isolated shallow scratch. the material is mainly plowed sideway along the track of the abrasive particle with no net material removal. However, it is observed that material is detached close to the intersection zone of two scratches. Motivated by this observation, it is speculated that the deformation mechanism changes from ploughing mode to shear-segmentation mode as the abrasive particle approaches the intersection of two scratches under small indentation depth for ductile metals. The proposed mechanistic material removal rate (MRR) model yields Preston constant similar to those observed experimentally for CMP processes. The proposed model also reveals that the nature of the slurry-pad interaction mechanism, and its associated force partitioning mechanism, is important for determining the variation of MRR with particle size and concentration. It is observed that under relatively soft pads, small particles and low particle concentration, the pad undergoes local deformation, yielding an increased MRR with increasing particle size and concentration. At the other extreme, the intact walls of the surface cells and the connecting cell walls between the surface pores deform globally, resembling a beam or a plate, and a decreasing trend in MRR is observed with increasing particle size and concentration. The predicted MRR trends are compared to existing experimental observations. [ABSTRACT FROM AUTHOR]

This paper reports an integrated approach for jointly solving the process selection, machining parameter selection, and tolerance design problems to avoid inconsistent and infeasible decisions. The integrated problem is formulated as a bicriterion model to handle both tangible and intangible costs. The model is solved using a modified Chebyshev goal programming method to achieve a preferred compromise between the two conflicting and noncommensurable criteria. Examples are provided to illustrate the application of the model and the solution procedure. The results show that the decisions on process selection, machining parameter selections, and tolerance design tan be made simultaneously with the model. [ABSTRACT FROM AUTHOR]

Variation propagation modeling has been proved to be an effective way for variation reduction and design synthesis in multi-operational manufacturing processes. However, previously developed approaches for machining princesses did not directly model the process physics regarding how fixture, and datum, and machine tool errors generate the same pattern on part features. Consequently it is difficult to distinguish error sources at each operation. This paper formulates the variation propagation model using the proposed equivalent fixture error concept. With this concept, datum error and machine tool error are transformed to equivalent fixture locator errors at each operation. As a result, error sources can be grouped and root cause identification can be conducted in a sequential manner. The case studies demonstrate the model validity through a real cutting experiment and model advantage in measurement reduction for root cause identification. [ABSTRACT FROM AUTHOR]

This paper proposes an analytical approach to detect depth-of-cut variations based on the cutting-force shape characteristics in end milling. Cutting forces of a single-flute end mill are analyzed and classified into three types according to their shape characteristics. Cutting forces of a multiple-flute end mill are then classified by considering both the cutting types of the corresponding single-flute end mill and the degree of overlap the successive flutes in the cut. Force indices are extracted from the cutting forces and depth-of-cut variations are detected based on the changes of the force shape characteristics via the force indices in an end-milling process. The detection methodology is validated through cutting experiments. [ABSTRACT FROM AUTHOR]

This paper presents a systematic finite element model to predict the fixture unit stiffness by introducing nonlinear contact elements on the contact surface between fixture components. The contact element includes three independent springs: two in tangential directions and one in the normal direction of the contact surface. Strong nonlinearity is caused by possible separation and sliding between two fixture components. The problem is formulated by the penalty function method and is solved by the Newton­Raphson procedure. The model was validated by two cases of analysis of a linear cantilever beam and a simple fixture unit with two components. The results are in agreement with the corresponding analytical solution of beams and the previous experimental results for fixture in the literature. [ABSTRACT FROM AUTHOR]

This paper reviews the new concept "microfactory" and related developments. Machined parts are becoming progressively smaller; so production machinery that remains a conventional size is often inappropriate for such products. The term "microfactory" represents an entirely new approach to design and manufacture that minimizes production systems to match the size of the parts they produce. It leads to conservation of space and energy, and the reduction of investment and operational costs, as well as the reduction of emissions and the load on operators. Furthermore, it provides a system with dynamic reconfigurability, aiming at a light and agile manufacturing system optimized for current manufacturing needs in a borderless and highly competitive market. In Japan, research institutes, research consortia, and the private sec- tor have carried out targeted research and development aimed at this concept for over a decade. Some systems are past the research stage and in daily use. Outside Japan, the philosophy and advantages of microfactory have reached an appreciative audience in the U.S., Europe, and Asia. Microfactory is at the cutting edge of competitive manufacturing in the 21st century, ushering in a multidimensional paradigm shift. Here we also briefly examine some future tasks. [ABSTRACT FROM AUTHOR]

Capacitive displacement sensors are widely used in precision manufacturing and metrology because they measure displacements with nanometer resolution. Prior literature usually treats capacitive sensors consisting of electrodes arranged as parallel plates. in this work, the target electrode is spherical, which is common in machine tool metrology, spindle metrology, and the measurement of sphericity. The capacitance due to a gap between flat and spherical electrodes is less than that of two flat electrodes, which causes four effects. As the diameter of the target electrode is reduced, the sensitivity increases, the sensing range decreases, the sensing range shifts toward the target, and the sensor becomes nonlinear This paper demonstrates and quantifies these effects for a representative capacitive sensor using finite element analysis and experimental testing. For larger spheres, the effects are correctible with apparent sensitivities, but measurements with the smallest spheres become increasingly nonlinear and inaccurate. [ABSTRACT FROM AUTHOR]

Nickel and nickel-alloy microparts sized on the order of 5-1000 microns have been imaged in three dimensions using a new microscopic technique, Digital Volumetric Imaging (DVI). The gears were fabricated using Sandia National Laboratories' LIGA technology (lithography, molding, and electroplating). The images were taken on a microscope built by Resolution Sciences Corporation by slicing the gear into one-micron thin slices, photographing each slice, and then reconstructing the image with software. The images were matched to the original CAD (computer aided design) model, allowing LIGA designers, for the first time, to see visually how much deviation from the design is induced by the manufacturing process. Calibration was done by imaging brass ball bearings and matching them to the CAD model of a sphere. A major advantage of DVI over scanning techniques is that internal defects can be imaged to very high resolution. In order to perform the metrology operations on the microcomponents, high-speed and high-precision algorithms are developed for coordinate metrology. The algorithms are based on a least-squares approach to data registration the {X, Y,Z} point clouds generated from the component surface onto a target geometry defined in a CAD model. Both primitive geometric element analyses as well as an overall comparison of the pan geometry are discussed. initial results of the micromeasurements are presented in the paper. [ABSTRACT FROM AUTHOR]

This paper reports on nanosurface fabrication of hard brittle materials by structured diamond tool imprinting. Ultrafine structured surfaces were fabricated on soda glass, firelite glass, quartz glass, quartz wafer and silicon. A specially designed and developed nanoindentation tester and a structured diamond tool machined by Focused Jon Beam (FIB) are used for the generation of such surfaces. Imprinted marks and the ultrafine structures are analyzed for their geometrical shape and accuracy. Load-depth analysis on the formed surfaces was carried out. Critical depth, at which ductile-to-brittle transition in deformation occurs, was assessed for the hard brittle materials. Limits of ductile mode indentation for hard brittle materials were discussed in detail. Variation in the depth of structures in an imprinted mark was studied. [ABSTRACT FROM AUTHOR]

This paper examines the surface generation process in the micro-endmilling of both single-phase and multiphase workpiece materials. We used 508 µm dia endmills with edge radii of 2 and 5 ,am to machine slots in ferrite, pearlite, and two ductile iron materials at feed rates ranging from 0.25 to 3.0 µm/flute. A surface generation model to predict the surface roughness for the slot floor centerline is then developed based on the minimum chip thickness concept The minimum chip thickness values were found through finite element simulations for the ferrite and pearlite materials. The model is shown to accurately predict the surface roughness for single-phase materials, viz., ferrite and pearlite. Two phenomena were found to combine to generate an optimal feed rate for the surface generation of single-phase materials: (i) the geometric effect of the tool and process geometry and (ii) the minimum chip thickness effect The surface roughness measurements for the ductile iron workpieces indicate that the micromilling surface generation process for multiphase workpiece materials is also affected by the interrupted chip-formation process as the cutting edge moves between phases resulting in burrs at the phase boundaries and the associated increases in surface roughness. [ABSTRACT FROM AUTHOR]

In Part II of this paper, a cutting force model for the micro-endmilling process is developed. This model incorporates the minimum chip thickness concept in order to predict the effects of the cutter edge radius on the cutting forces. A new chip thickness computation algorithm is developed to include the minimum chip thickness effect. A slip-line plasticity force model is used to predict the force when the chip thickness is greater than the minimum chip thickness, and an elastic deformation force model is employed when the chip thickness is less than the minimum chip thickness. Orthogonal, micro structure-level finite element simulations are used to calibrate the parameters of the force models for the primary metallurgical phases, ferrite and pearlite, of multiphase ductile iron workpieces. The model is able to predict the magnitudes of the forces for both the ferrite and pearlite workpieces as well as for the ductile iron workpieces within 20%. [ABSTRACT FROM AUTHOR]

This paper aims to explain the size-effect in the Primary Deformation Zone (PDZ) in machining using strain gradient plasticity theory. Considering a parallel-sided shear zone configuration, models are formulated for the evaluation of strain gradient, density of geometrically necessary dislocations, shear strength and the specific shear energy. The analysis of deformation in the PDZ shows that the length of the shear plane represents the fundamental material length scale governing the size-effect. It also provides an estimate of the lower bound on the size-effect observed in the specific shear energy. The general trends predicted by the model are shown to agree well with the experimental values obtained from the literature. [ABSTRACT FROM AUTHOR]

Microforming using a small machine (or so-called desktop machine) is an alternative new approach to those using full-size heavy equipment for manufacturing microparts. Microparts are commonly defined as parts or structures with at least two dimensions in the submillimeter range, which are used extensively in electronics and micromechanical products. However; when scaling down a conventional forming process to microscale, the influence of the so-called size effect needs to be considered. The individual micro structure (size, shape, and orientation of grains) and the interfacial conditions show a significant effect on the process characteristics. In this paper; the process of extrusion is investigated to establish it as a viable process for microforming. A forming assembly is fabricated and used in conjunction with a loading substage to extrude micropins with a final diameter of 1 mm. The effect of grain size is investigated by using workpieces heat treated to produce grain sizes varying from 32 µm up to 211 µm. Two extrusion dies with different roughness are used to study the effect of surface finish. While experiments lead to interesting questions and new discoveries, theoretical or numerical solutions are necessary tools for process optimization. Here, knowing the limits of the current widely used numerical simulation tools [i.e., the Finite Element Method (FEM)], a new method, the Reproducing Kernel Element Method (RKEM), has recently been developed to address the limitations of the FEM (for example, remeshing issue), while maintaining FEM's advantages, e.g., the polynomial reproducing property and function interpolation property. The new RKEM method is used to simulate the microextrusion problem. Its results are compared with that obtained from the FEM and the experiment result Satisfactory results were obtained. Future directions on the experimental and simulation work are addressed. [ABSTRACT FROM AUTHOR]