Visual interactive simulation and artificial intelligence in design of flexible manufacturing systems

The design of flexible manufacturing systems is a complex decision-making process that typically involves the evaluation of a number of different design alternatives. The evaluation is often performed using modelling and simulation techniques. The role of visual interactive modelling and simulation in design of flexible manufacturing systems is discussed. The application of artificial intelligence techniques to implement a set of knowledge sources, used for accomplishment of various design activities, is described. An object-orientated implementation is used to illustrate the underlying concepts.     

Repair of underground buried pipes with resin transfer molding

Repairing and replacing of worn-out underground pipes, such as sewer pipes, water-supply pipes, gas pipes, and communication cables by excavating not only cause traffic congestion but also produce large amount of waste. Also, the operation requires heavy equipments and longer operating time and high cost.

In this study, the repairing–reinforcing process of underground pipes with glass fiber fabric polymer composites using resin transfer molding (RTM) which overcomes the problems of present trenchless technologies has been developed. The developed process requires shorter operation time and lower cost with smaller and simpler operating equipments than conventional trenchless technologies. For the faultless operation, a simple method to apply pressure and vacuum to the reinforcement was developed. The resin wetting and void removal during RTM process for very large and long-composite buried pipes were experimentally investigated, and the efficient void removal method was suggested. Cure status and resin filling were monitored with a commercial dielectrometry cure monitoring system, LACOMCURE.

From the investigation, it has been found that the developed repair technology with appropriate process parameters and on-line cure monitoring has many advantages over conventional methods.     

新型树脂传递模塑技术

概述了传统树脂传递模塑(RTM)及在其基础上发展起来的新型RTM工艺,包括真空辅助树脂传递模塑(VARTM)、Seemann复合材料树脂浸渍模塑成型工艺(SCRIMP)和树脂膜渗透成型工艺(RFI)的成型原理、优点,并指出目前存在的缺点及解决方法.     

Interlayer toughening of resin transfer molding composites

In previous research it was shown that through using preformed elastomer particle modified tackifier/binder, materials interlayered RTM composite structures could be manufactured. These interlayers resulted in excellent toughness improvements of traditionally brittle RTM materials. In this work, the effects of tackifier application and composition were investigated by modifying spray and powder epoxy tackifiers with polyamide 6 particles. The spray tackifier provided 30% improvements in Mode II interlaminar fracture toughness, and slight increases in the interlaminar shear strength without reducing the thermal properties. The powder tackifier showed a slightly lower performance increase due to a less homogeneous laminate structure.     

All-polyamide composites prepared by resin transfer molding

Resin transfer molding (RTM) was used to manufacture all-polyamide (all-PA) composites in which PA6 matrix was in situ formed by the anionic polymerization of ε-caprolactam (CL). Influence of molding temperature (T _M), a critical process parameter, on the structure and properties of all-PA composites was investigated using TGA, DSC, SEM, and tensile, flexural test. Increasing T _M resulted in the decrease of CL conversion and the enhancement of fiber/matrix interface bonding. By comparing the mechanical properties of all-PA composites prepared at different T _M (140–200 °C), an optimal T _M (180 °C) was found in this temperature range. As a whole, the complete consolidation of all-PA composites and the remarkable reinforcing effect of PA66 fibers on PA6 matrix were assured by low-void fraction, high-CL conversion and strong interface performance though in a wide T _M range.     

Analysis of vacuum bag resin transfer molding process

An analytical model is developed to analyze the resin flow through a deformable fiber preform during vacuum bag resin transfer molding (VBRTM) process. The force balance between the resin and the fiber preform is used to account for the swelling of fiber preform inside a flexible vacuum bag. Mold filling through multiple resin inlets is analyzed under different vacuum conditions. The formation of dry spots is demonstrated in the presence of residual air. Molding of a three-dimensional ship hull with lateral and longitudinal stiffeners is simulated to demonstrate the applicability of the model.     

Forming characteristics during the high-pressure resin transfer molding process for CFRP

The high-pressure resin transfer molding (HP-RTM) process has potential applicability to the mass production of lightweight vehicles made of carbon fiber-reinforced plastic in the automotive industry. In recent years, the development of robust equipment, new processes, and fast cure matrix systems have significantly reduced the cycle time to less than 5 min. In this study, the cavity pressure of the HP-RTM process was monitored to analyze the molding characteristics. The mold was equipped with two cavity pressure sensors and three temperature sensors. The cavity pressure characteristics during the HP-RTM injection, pressurization, and curing processes were studied. Selected process parameters such as the mold cap size, maximum pressing force, and injection volume were analyzed. The results demonstrated correlations between the selected process parameters and final forming characteristics.     

采煤机T型涨套的工艺及工装设计

主要针对我公矧采煤机中创新零件T型涨套的机加工工艺进行了优化。针对开口槽易开裂问题、材料的优化选择、加工过程中震动的消除等问题进行了分析,并提出合理的解决方案,设计了有效的工装。提高了该零件的加工精度,延长了其使用寿命,有效保证了采煤机的产品质量,且对相似结构的零件加工起到了定的借鉴作用。     

Numerical simulation of molding-defect formation during resin transfer molding

The present study investigated a numerical simulation of molding-defect formation during resin transfer molding using boundary element method and line dynamics. The proposed method enables to simulate small molding defects by increasing the node for required position during time evolution; thereby, the method computes high-resolution flow front without being affected by the initial mesh geometry. The method was applied to the radial injection RTM with single inlet, and it was confirmed by comparison with theoretical value based on Darcy’s law that the flow advancement was computed with high accuracy. In addition, the method was also applied to the flow advancement for inclusion problem with cylinder, and four-point injection problem. The simulated flow behavior, void formation, and shrinkage agreed with the results in references. Finally, the method was compared with experiments using two-point injection problem. The computed configuration of the flow front and weld line agreed well with the experimental results.     

Optimum design of structures by accounting for the manufacturing process

A mathematical statement of the problem of optimum design of structures by accounting for the manufacturing process, called a problem of bioptimum design, is examined. It is shown that solution of this problem reduces to successive solution of the problem of optimum design and optimization of the manufacturing process. To this end, a special minimizing sequence has been constructed. A problem of bioptimum design of hydraulic cylinders is discussed as an example. Four manufacturing process alternatives, including the following finishing operations, are presented: machining, autofretting with internal pressure; shaping on a mandrel; drawing with thinning. As the solution of the problem showed, drawing is the most effective process from the viewpoint of strength of hydraulic cylinders. It provides for a favorable residual stress field and best strengthening of the cylinder material.Translated from Problemy Prochnosti, No. 5, pp. 64–68, May, 1991.     

Analysis and minimization of void formation during resin transfer molding process

In the resin transfer molding process, residual air in the pores of fiber preform results in dry spots and microvoids in the finished product. The dry spots are usually formed due to irregular permeability of fiber mat and improper injection locations. The microvoids result from non-uniform microarchitecture of the fiber preform, and they are transported through the gap between fiber tows during infiltration of the resin. In this study, a real-time simulation/control method was proposed to actively control the formation and the transport of air voids during the mold filling. The flow equations were solved in real time to predict the change of the flow front shape. The flow front was detected by optical sensors and the control actions were taken based on the sensor signals. Through this automated simulation/control scheme, a real-time control of resin flow could effectively avoid the dry spots and minimize the formation of microvoids by modulating the injection pressure.     

树脂传递模塑工艺中的非饱和流动过程模拟与实验研究

针对编织类纤维增强体的纤维束之间与纤维束内孔隙的双尺度特点,建立了平纹织物的细观结构模型,并推导了汇函数的数学表达式。建立了局部细观流动特征的非饱和流动控制方程,利用有限元/控制体积方法求解,得到了局部饱和度分布。与实验进行比较,吻合较好。      

Integrated design approach for virtual production line-based reconfigurable manufacturing systems

Reconfigurable manufacturing systems (RMSs) have been recognized as a new manufacturing paradigm. In light of their enhanced flexibility and responsiveness, RMSs are considered to be mostly applicable to the very dynamic and unpredictable marketplaces of the near future. However, systematic approaches to the design and ramp-up of an RMS have not been well addressed. This paper presents a virtual production line-based (VPL) approach to the design and operation of a reconfigurable manufacturing system. Shop floor attributed finite-capacity automaton and VPL attributed finite-capacity automaton are proposed for modelling the control of an RMS, which leads to ease of control software development. Algorithms for balancing VPLs to maximize the productivity of an RMS are discussed. The results of simulation runs of the proposed methodology and algorithms applied to simplified back-end semiconductor manufacturing are provided.     

An approach to couple mold design and on-line control to manufacture complex composite parts by resin transfer molding

During impregnation of the resin into a closed mold containing the preform in the resin transfer molding (RTM) process, increased yield of successful parts can be achieved if one could account for the inherent disturbances such as race-tracking and preform variability. One way to address this is to use sensors and actuators to control the resin flow dynamics during the impregnation process to counteract the disturbances. In this paper, we use a mold filling simulation tool to develop a design and control methodology that, with the help of sensors and actuators, identifies the flow disturbance and redirects the resin flow to successfully complete the mold filling process without any voids. The methodology is implemented and experimentally validated for a mold geometry that contains complex features such as tapered regions, rib structures, and thick regions. The flow modeling for features such as ribs and tapered sections are validated independently before integrating them into the mold geometry. The approach encompasses creation of software tools that find the position of the sensors in the mold to identify anticipated disturbances and suggest flow control actions for additional actuators at auxiliary locations to redirect the flow. Laboratory hardware is selected and integrated to automate the filling process. The effectiveness of the methodology is demonstrated by conducting experiments that, with feedback from the sensors, can automate and actively control the flow of the resin to consistently impregnate all the fibers completely despite disturbances in the process.     

Development of adaptive injection flow rate and pressure control algorithms for resin transfer molding

To prevent dry spot formation during fabrication of composite parts by Resin Transfer Molding (RTM), a control interface and four different adaptive control algorithms have been developed and tested with numerical simulations. The interface is capable of controlling the flow pattern of resin as it fills a mold containing a preform of fiber reinforcement, provided that the mold is equipped with multiple inlet gates, a single vent and a spinal sensor system that continuously feeds the interface with the resin flow front locations along the spine lines connecting the inlet gates to the vent. Four different adaptive control algorithms targeting on injection flow rate control, injection pressure control, linearly-corrected pressure control, and the combined flow rate and linearly-corrected pressure control have been proposed and incorporated with the control interface. To provide desirable controllability of the filling process and effective utilization of the resin dispensing equipment, the final formulations were optimized by means of numerical simulations of a rectangular RTM part containing different permeability distributions. The results were compared to investigate the strengths and weaknesses of the spinal adaptive control algorithms in terms of dry spot size, filling speed, and the minimum responding speed of injection pump. Finally, a complex geometry case study was conducted to validate and highlight the spinal adaptive control algorithms’ capability in handling flow disturbance for a complex RTM mold filling process which involves irregular mold geometry, multiple inserts, significant permeability and racetracking variations, and non-straight spinal sensors.     

Transient gas flow technique for inspection of fiber preforms in resin transfer molding

A transient gas flow method was developed to determine the quality of fibrous preforms in resin transfer molding (RTM) prior to resin injection. The method aims at detecting defects resulting from preform misplacement in the mold, accidental inclusions, preform density variations, race tracking, shearing, etc. Unlike the previously developed method based on steady-state gas flow, the new method allows for the acquisition of continuous time-varying pressure data from multiple ports during a single test. The validity of the method was confirmed by one-dimensional flow experiments.     

Principles of design for laminated tooling

The emergence of rapid prototyping over the last 7-8 years has had a revolutionary effect in many companies undertaking new product design. Currently, the emphasis has moved from rapid prototyping to rapid tooling. Use of laminated tooling for sheet metal working has already been proved and some work has also been undertaken to build laminated tooling for moulding plastics. Laminated tooling is relatively rare at the moment and as more tools are built using this technique the benefits and limitations will become more clear.