Souran Manoochehri

Optimal cooling system design for multi-cavity injection molding

Abstract The objective of this paper is to present a methodology for optimal design of cooling systems for multi-cavity injection mold tooling. After the part layout and the injection mold are designed, the methodology optimizes cooling system layout in terms of cooling channel size, locations, and coolant flow rate. The mold cooling design is modeled as a non-linear constrained optimization problem. The objective function for the constrained optimization problem is stated as minimization of both a function related to part average temperature and temperature gradients throughout all the cavities. The constrained optimal design problem is solved using Powells conjugate direction with the penalty function method. The objective function is evaluated using finite element analysis solving the transient heat conduction problem. A matrix-free Jacobi conjugate gradient algorithm of Galerkin finite element method is utilized to simulate transient heat conduction.

Optimum parting line design of molded and cast parts for manufacturability

Abstract This paper presents a methodology for obtaining an optimal design of a mold tool for an injection molded or a diecast part based on part geometry. The methodology uses multiobjective function criteria. It considers how parting line complexity, draw depth, number of undercuts, number of unique side cores, and mold complexity affect manufacturability and cost. The design variables selected for this problem are draw direction range and parting line location. The draw direction range limits possible parting line locations to those not associated with undercuts. These design variables can be extracted from the part geometry by dividing the surfaces into concave and convex regions. The concave and convex regions determine the allowable draw range and parting line location for the part, respectively. A nonlinear programming technique generates the optimal mold configuration solution. This paper presents an example that generates the optimal mold configuration for a typical molded part using the described methodology.

A Review of Research in Materials, Modeling and Simulation, Design Factors, Testing, and Measurements Related to Electromagnetic Interference Shielding

Abstract This paper summarizes and reviews research in electromagnetic interface (EMI) shielding based on the review of over 300 articles which are presented in four separate categories. It will be noticed, however, that some articles are cited in more than one category. At the end of each subcategory. a summary is given for easy reference. A table relating each subcategory to the given references at the end of this paper is also supplied. The document comprises a comprehensive study of basic concepts in EMI shielding, analytical and numerical modeling techniques, test methods and instrumentations, material selection, and factors involved in shielding degradation. Cost comparison for various shielding techniques, and the advantages and disadvantages of using the different types of shielding materials and testing methods are reviewed.

Enhanced ac electrothermal fluidic pumping in microgrooved channels

It is important to generate fast fluid flow yet maintain low temperature rise for ac electrothermal (ac ET) pumping in microsystems with conductive fluids. This has been generally the limitation of ac ET driven micropump applications. We present an enhanced ac ET pumping mechanism using low voltage ac signals that can result in a small amount of temperature rise. Different from the published traveling wave and asymmetric electrode structures positioned on insulated flat surfaces, channels with a microgrooved surface are utilized in this study. The effects of the microgroove existence on the modification of the ET body force and recession of the vortex backflows are demonstrated. Forward and backward pumping modes are identified and analyzed. This mechanism utilizes a thin film of asymmetric electrode structure on the microgrooved channel floor that can be fabricated with common planar lithography technologies. This study demonstrates that using the microgrooved structure can increase pumping capacity by f...

A Computer-Aided Optimization Approach for the Design of Injection Mold Cooling Systems

A methodology is presented for the design of optimal cooling systems for injection mold tooling which models the mold cooling as a nonlinear constrained optimization problem. The design constraints and objective function are evaluated using Finite Element Analysis (FEA). The objective function for the constrained optimization problem is stated as minimization of both a function related to part average temperature and temperature gradients throughout the polymeric part. The goal of this minimization problem is to achieve reduction of undesired defects as sink marks, differential shrinkage, thermal residual stress built-up, and part warpage primarily due to non-uniform temperature distribution in the part. The cooling channel size, locations, and coolant flow rate are chosen as the design variables. The constrained optimal design problem is solved using Powells conjugate direction method using penalty function. The cooling cycle time and temperature gradients are evaluated using transient heat conduction simulation. A matrix-free algorithm of the Galerkin Finite Element Method (FEM) with the Jacobi Conjugate Gradient (JCG) scheme is utilized to perform the cooling simulation. The optimal design methodology is illustrated using a case study.

Microfluidic pumping optimization in microgrooved channels with ac electrothermal actuations

An optimization methodology is developed and applied to an ac electrothermal pump design with patterned microgrooved features. The microgrooved configuration can overcome the restrictions of the conventional planar configuration on pumping performance by diminishing fast backward flows and suppressing prolonged streamlines. At all frequency excitations (0.2–1000 MHz) and ion concentration conditions (5×10−3–0.1 M), the optimum microgrooved configuration generates much faster flow rate than planar configuration. This happens without additional increases in the maximum temperature values. The effects of elevated temperature on ac ET flow behavior is investigated and analyzed.

A hybrid deterministic/stochastic optimization approach for the shape configuration design of structures

This paper presents a computer-based shape configuration design methodology to generate optimum design of specified structures satisfying the structural performance requirements and the geometric connectivity of the model. Mathematically, this problem can be categorized as a large-scale, nonconvex and nonlinear problem. The solution methods, grouped into two main categories, deterministic and stochastic approaches, require enormous computational efforts to find global optimum designs, a matter of major importance since many local suboptimal solutions can exist. In this study, two popular methods belonging to each class are examined and compared. The methods understudied are selected as the enumeration technique for deterministic approach and the simulated annealing for the stochastic method. The advantages and disadvantages of each technique are investigated. Using the best properties of each method and an algorithm for phase change between the two, a hybrid global shape optimization approach is formulated. The hybrid method is structured to combine the enumeration method for local minimization process and the simulated annealing for global minimum search phase. The hybrid method can find global optimum designs in a robust and efficient way, contrary to the signle phase solutions examined in this study. To demonstrate the hybrid method and its effectiveness, several design examples are presented.

Structure-modulus relationships for injection-molded long fiber-reinforced polyphthalamides

Abstract The structural information needed for modulus evaluation of long fiber-reinforced composites includes the fiber volume fraction, the modulus and the Poissons ratio of the constituents, the fiber orientation and the fiber length distribution. In this work, the fiber orientation distribution is expressed in terms of three parameters which may vary with spatial location on the part: the average orientation angle on the surface, the average orientation angle on the mid-plane and the thickness of shell-core layers. With the independent evaluation of the fiber length distribution, composite models are used to evaluate mechanical property distribution such as modulus and Poissons ratio as a function of spatial location on the part. The approach used in this work combines the Halpin-Tsai equations and a stiffness modeling scheme which follows a combination of iso-stress and iso-strain averaging techniques to determine the anisotropic material behavior of these composites. The predictions are compared with experimental data from injection-molded plaques fabricated at different processing conditions. Modulus variation with location is measured by fabricating dog-bone tensile samples from the plaques at four in-flow and four cross-flow positions. Modulus variability is shown to be high with location and the model captures this non-uniformity over the whole range of tested samples.

Modeling of heat transfer in thermoplastic composite tape lay-up manufacturing

Abstract The process of thermoplastic composite tape lay-up has been modeled in terms of heat transfer. The main objective is to investigate the effects of process parameters on the quality of thermoplastic composite laminates fabricated by the tape placement process. Computer codes were written to generate the temperature distribution. The numerical analysis has been carried out using finite difference method. The numerical model was verified with available experimental results. The numerical results compare favorably with those published in the literature. This analysis leads to the prediction of the temperature distribution along the length and through the thickness of the composite. The prediction of the temperature distribution enables proper selection of process variables, which affects the production rate and quality of the parts

Fiber Orientation Morphological Layers in Injection Molded Long Fiber Reinforced Thermoplastics

Flow-induced fiber orientation can vary significantly across the thickness of injection molded parts and is usually present in the form of through-thickness layers. In this work, fiber orientation was examined both on the flow plane and through the thickness. The thickness of a shell layer with fiber orientation in the flow direction and a core layer with a fiber orientation mainly transverse to the flow were measured via microscopy. The effect of filling speed and mold thickness on the molded plaque morphology was identified. Mold-filling simulations were undertaken in order to provide the characteristic shell and core layer fiber orientations as well as the frozen layer thickness at the end of filling and the gap-wise shear rate gradients. The combined frozen and high shear rate regions were correlated with the experimental shell layer thicknesses.