The Experts below are selected from a list of 1299 Experts worldwide ranked by ideXlab platform
Benoit Boulet - One of the best experts on this subject based on the ideXlab platform.
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Information Control Problems in Manufacturing 2006 - AGENT-BASED CONTROL FOR Thermoforming ProcessES
IFAC Proceedings Volumes, 2016Co-Authors: Zahir Albadawi, Benoit Boulet, Patrick Girard, Robert Diraddo, Vincent ThomsonAbstract:Abstract Modern manufacturing systems deal with highly dynamic and complex Processes and need to adapt to the rapid changes in manufacturing environments. Model-based control greatly improves Process adaptiveness by integrating deep knowledge of Process phenomena with advanced simulation tools. Agent-based technologies provide a favourable framework for implementing model-based control. An agent-based architecture developed for model-based control and an implementation for the Thermoforming Process are presented. How the architecture facilitates interoperability is described.
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Iterative learning model predictive controller of plastic sheet temperature for a Thermoforming Process
2012 American Control Conference (ACC), 2012Co-Authors: Benoit BouletAbstract:Properties of the Thermoforming Process, such as its nonlinear, time-varying dynamics and actuator constraints, make its control challenging. An iterative control technique along with model predictive control (MPC) is presented in this paper on 2D control of the Thermoforming Process. This approach utilizes not only incoming information from the ongoing cycle, but also the information stored from the past cycles. To deal with constraints as well as non-repetitive disturbances in the Process, the MPC technique is incorporated to update the control law within the cycle. To exploit the repetitive nature of the heating phase of the Process, a cycle-to-cycle iterative learning control technique direction is proposed. The iterative learning strategy is useful for achieving desired temperature despite model mismatch and disturbances. Even though the proposed multi-zone temperature controller can handle a multivariable Process, the large number of computations makes it difficult to apply to large systems such as a Thermoforming machine. To reduce the computational burden, the control laws are computed offline using multi-parametric programming.
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ACC - Iterative learning model predictive controller of plastic sheet temperature for a Thermoforming Process
2012 American Control Conference (ACC), 2012Co-Authors: Benoit BouletAbstract:Properties of the Thermoforming Process, such as its nonlinear, time-varying dynamics and actuator constraints, make its control challenging. An iterative control technique along with model predictive control (MPC) is presented in this paper on 2D control of the Thermoforming Process. This approach utilizes not only incoming information from the ongoing cycle, but also the information stored from the past cycles. To deal with constraints as well as non-repetitive disturbances in the Process, the MPC technique is incorporated to update the control law within the cycle. To exploit the repetitive nature of the heating phase of the Process, a cycle-to-cycle iterative learning control technique direction is proposed. The iterative learning strategy is useful for achieving desired temperature despite model mismatch and disturbances. Even though the proposed multi-zone temperature controller can handle a multivariable Process, the large number of computations makes it difficult to apply to large systems such as a Thermoforming machine. To reduce the computational burden, the control laws are computed offline using multi-parametric programming.
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IAS Annual Meeting - Development of an improved mathematical model of the heating phase of Thermoforming Process
2011 IEEE Industry Applications Society Annual Meeting, 2011Co-Authors: Benoit BouletAbstract:This paper presents an improved mathematical model to represent a more accurate relationship among inputs and outputs of the heating phase of the Thermoforming Process. The proposed state-space model of the heating phase of Thermoforming Process can present and explain some incidents which are impossible to explain using the existing model. The main purpose of the paper is to improve the quality of predictions of the system's output and state through more accurate evaluation of the inputs and system properties. First, the modeling is developed based on the heat transfer method and system's behaviour. Then, a series of specialized experimental data were compared with the simulation data obtained from the developed model to validate it. All three kind of heat transfer methods (conduction, convection and radiation) are considered in the development of the model of a Thermoforming machine. The proposed state space model is simulated using a Simulink model to compare with real time results. The input output relationship of the proposed model almost accurately follows the real time relationship of the inputs and outputs at different operating conditions. The proposed model gives the improved results compared to the existing model with the real time experimental data even there was some discrepancy of the existed model result with the real time data. The accuracy of the proposed model is evidenced by the results.
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A model predictive controller of plastic sheet temperature for a Thermoforming Process
Proceedings of the 2011 American Control Conference, 2011Co-Authors: Benoit Boulet, Ahmad HaidarAbstract:This paper presents a method to control the surface temperature of a plastic sheet using model predictive control (MPC). Although control techniques have been developed for the heating phase of the Thermoforming Process, oven heater temperatures in the Thermoforming industry are still largely adjusted by trial and error based on the experience of the operator. MPC is one of the advanced methods for Process control that has been used in different plants since the 1980s. Even though the MPC controller can handle a multivariable Process, the large number of computations makes it difficult to apply to large systems such as multi-zone temperature control in a Thermoforming machine. In this paper, the design of a model predictive controller is reported and implemented on a complex Thermoforming oven with a large number of inputs and outputs for precise control of sheet temperatures under hard constraints on heater temperature and their rates.
Fabrice Schmidt - One of the best experts on this subject based on the ideXlab platform.
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Identification of the temperature dependent relation between thermo-optical properties and morphology of semi-crystalline thermoplastics for Thermoforming Process
2016Co-Authors: Sinan Boztepe, Yannick Maoult, Olivier De Almeida, Fabrice SchmidtAbstract:Heating stage of the Thermoforming of thermoplastics are critical as it has great effect on their formability under forming and therefore product quality. As radiation heat transfer is widely used for the heating of thermoplastic preforms, physical background of the radiation heating of bulk thermoplastic polymers has to be understood well for an accurate prediction on their temperature profile. In the past, many numerical approaches were developed based on thermo-optical characteristics of thermoplastics whereas little attention was given to the relation between their microstructure and thermo-optical parameters. Considering semi-crystalline thermoplastics the effect of microcrystalline structure is key to identify the thermo-optical properties and develop an accurate numerical radiative heat transfer model for optimization of Thermoforming Process. Previous studies in literature showed that there is a strong coupling between microstructure of semi-crystalline thermoplastics and their thermo-optical properties in the near-infrared spectral region. In the present work, the relation between thermo-optical characteristics and microstructure of polyolefin-based (PO) polymer was studied considering the change in its morphology at various temperatures. The optical characteristics of the PO were experimentally analyzed under heating conditions using an in-house developed device that is built using a Fourier Transform Infrared spectroscopy, integrating sphere and heating plate. Thanks to the analyses, the changes in the thermo-optical properties of the PO were correlated to its varying morphology under increasing temperature. As semi-crystalline thermoplastics are heated up to melting temperature to soften enough for successful forming Process, their microcrystalline structure may show variation above glass transition temperature and this temperature-dependent relation cannot be neglected for building an accurate numerical model for infrared heating assisted Thermoforming.
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Experimental and numerical infrared heating of thermoplastic sheet during Thermoforming Process
2004Co-Authors: Sylva Andrieu, Fabrice Schmidt, Yannick MaoultAbstract:Thermoforming includes a heating stage of thermoplastic sheets by infrared lamps. The temperature distribution on the surface and through the thickness of the sheet conditions the distribution thicknesses of the thermoformed part. Our objective is to understand the heat transfers between the infrared heaters and the thermoplastic sheets. For that we developed an infrared heating device which makes it possible to carry out temperature measurements of a sheet during the heating with an infrared oven. An AGEMA 880 LW infrared camera allows measuring the back surface (non-directly exposed to the radiation) temperature distribution of the sheet. An indication of temperature discrepancy through the thickness is given by a RAYTEK Thermalert TX pyrometer. Two infrared ovens (halogen and ceramics lamps) were studied characteristics of infrared ranges (short and long wavelengths respectively) on a polymer representative of the Thermoforming market (white PS 3mm-thickness sheets). These experimental measurements allow validating the numerical models. A method of radiative transfer based on ray tracing is used to calculate the irradiance with lamp reflectors. The Rosseland approximation is used to take into account the optical properties of the polymers that were measured using infrared spectrometry. The transient heat balance equation (including 3D radiative diffusion) is solved.
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modelling of infrared heating of thermoplastic sheet used in Thermoforming Process
Journal of Materials Processing Technology, 2003Co-Authors: Fabrice Schmidt, Le Y Maoult, S MonteixAbstract:Thermoforming consists of warming a plastic sheet and forming it into a cavity or over a tool using vacuum, air pressure and mechanical means. The Process begins by heating a thermoplastic sheet slightly above the glass transition temperature, for amorphous polymers, or slightly below the melting point, for semi-crystalline materials. As the final thickness distribution of the part is drastically controlled by the initial temperature distribution inside the sheet, it is very important to optimise the heating stage. In most of the Thermoforming machine, this step is performed using an infrared oven constituted of long waves infrared emitters. The goal of this study is to determine the efficiency of short waves infrared emitters (halogen lamps) for the heating step. The infrared heating of thermoplastic sheets will be modelled following two steps: an experimental set-up developed in our laboratory permits to measure the influence of parameters such as heaters temperature, incidence of the radiation, heat transfer coefficient, etc. An 880 LW AGEMA infrared camera is used to evaluate the surface distribution of the transmitted heat flux by measuring the temperature distribution on the surface of the thermoplastic sheet. In addition, a numerical model using control volume method (software called PLASTIRAD) has been developed to simulate the heating stage. In particular, it takes into account the spectral properties of both heaters and plastic sheet as well as the heaters directivity. Comparisons between experimental data and numerical simulations allow validating the numerical model using different types of emitters and polystyrene (PS).
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Heat conditioning modelling of Thermoforming Process: comparison with experiments
2003Co-Authors: Sylva Andrieu, Fabrice Schmidt, Yannick MaoultAbstract:The goal of this study is to improve the efficiency of infrared heating ovens used in the Thermoforming Process. The heat conditioning of thermoplastic sheets before forming consists in heating up thermoplastic sheets above the glass transition temperature of the polymer. The thickness distribution of the final product is strongly dependent on the initial temperature distribution inside the sheet. Well-calculated Process parameters during the heat conditioning step will allow improvements in, for example, cycle-time reduction. For that, we use different electric heaters that operate in different infrared ranges as: long, medium and short infrared wavelengths respectively. Thermoforming machines are generally equipped with ceramic heaters that operate in long infrared wavelengths. Recently, halogen lamps that are short wavelengths heaters have started to be employed in Thermoforming applications. So, an experimental infrared heating setup has been developed in order to compare the different kinds of heaters and the efficiency of lamp reflectors. The temperature of each infrared heater in the oven is controlled independently in order to optimise the surface temperature distribution of the thermoplastic sheet. For that, an 880 LW AGEMA infrared camera has been used to measure the temperature distribution of different thermoplastic sheets. We have chosen in this study the most commonly employed polymers in Thermoforming which are: ABS and PP used for thin gage sheets. Numerical simulations using software based on control-volume method have been performed and compared with experimental data.
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Infrared Heating Modeling of Thermoplastic Sheets in Thermoforming Process
2002Co-Authors: Sylva Andrieu, Yannick Maoult, Fabrice SchmidtAbstract:The Thermoforming Process involves a heating step before forming, the thermoplastic sheet being warmed up using infrared heaters. The forming temperature is above glass transition temperature for amorphous polymers and slightly below crystalline temperature for semi-crystalline polymers. Today, industrial Thermoforming machines generally feature an infrared oven with ceramics heaters that emit infrared long waves. Other electric radiant heaters like quartz tubes or halogen lamps are also used, but not as much. The heating step of the Thermoforming Process could be improved to obtain best sheet's temperature distribution which governs the thermoformed part thickness distribution. Many parameters influence the heating step such as geometry and number of heaters, heaters temperature, position of the heaters, distance between heaters and sheet… An experimental infrared heating device is developed in order to measure the effect of the different parameters. Software called PLASTIRAD based on the volume method is used to simulate the infrared heating of polymers in order to optimise the infrared oven of an experimental setup .
Ruben Salazar - One of the best experts on this subject based on the ideXlab platform.
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effect of the Thermoforming Process variables on the sheet friction coefficient
Materials & Design, 2014Co-Authors: Rosa Amalia Morales, Maria V Candal, O O Santana, A Gordillo, Ruben SalazarAbstract:The objective of this work was to obtain, through a simple experimental assembly, the real influence of the friction and Process conditions in the assisted Thermoforming Process. The use of simulation tools to optimize this Process requires the knowledge of the sheet-plug system friction coefficient [μ], the used temperature and velocity conditions, and due to that, the software does not have a wide database. For this, the users suppose μ with the previous known difference between the simulated and the experimental data. For this reason, the obtaining of μ may allow to achieve more accurate simulations. In this work, a modified pendulous impact in Izod geometry was used to the measurements. The μ increased with the sheet temperature. On the other hand, it was not possible to detect a significant μ variations regarded with the plug material
Yoshinobu Maeda - One of the best experts on this subject based on the ideXlab platform.
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Thermoforming Process for fabricating oral appliances influence of heating and pressure application timing on formability
Journal of Prosthodontics, 2007Co-Authors: Junko Yamada, Yoshinobu MaedaAbstract:Objectives: This study was designed to examine the influence of heating and pressure application timing for thermoplastic soft materials on formability during the Thermoforming Process. Methods: Ethylene vinyl acetate (EVA) and a high shock-absorbing material (Hybrar) were used. Five specimens (20 × 10 × 4 mm) were heated to temperatures of 60, 80, 100, 120, 140, 160, 180, and 200°C and then placed under a 4 N static weight with an indentation tip. The forming capability index (FI) was evaluated by rating the shape, size, and surface texture changes of the indentation tip reproduction in specimens using specially developed scales. The suitable temperature range for forming (STF) was determined by FI. Heat-holding capability of the two materials was also evaluated by the temperature changes in the cooling Process using a digital thermometer. Timing of air pressure application was examined with the time-dependent change in negative pressure among three types of forming machines. Results: STF of the EVA (80–120°C) was lower than that for Hybrar (140–160°C). The time required to reach the lower limit of the STF was statistically different between the two materials (EVA: 41 seconds, Hybrar: 13 seconds) (p < 0.05). The maximum negative pressure (MNP) of the three forming machines ranged from −12 to –60 cmHg and time to reach the temperature, 5–60 seconds. Conclusions: The results suggest that heating conditions for each type of sheet material should be predetermined by the STF. Forming Process should be performed with the high MNP before reaching the lower limit of the STF.
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Thermoforming Process for fabricating oral appliances influence of heating and pressure application timing on formability
Journal of Prosthodontics, 2007Co-Authors: Junko Yamada, Yoshinobu MaedaAbstract:OBJECTIVES: This study was designed to examine the influence of heating and pressure application timing for thermoplastic soft materials on formability during the Thermoforming Process. METHODS: Ethylene vinyl acetate (EVA) and a high shock-absorbing material (Hybrar) were used. Five specimens (20 x 10 x 4 mm) were heated to temperatures of 60, 80, 100, 120, 140, 160, 180, and 200 degrees C and then placed under a 4 N static weight with an indentation tip. The forming capability index (FI) was evaluated by rating the shape, size, and surface texture changes of the indentation tip reproduction in specimens using specially developed scales. The suitable temperature range for forming (STF) was determined by FI. Heat-holding capability of the two materials was also evaluated by the temperature changes in the cooling Process using a digital thermometer. Timing of air pressure application was examined with the time-dependent change in negative pressure among three types of forming machines. RESULTS: STF of the EVA (80-120 degrees C) was lower than that for Hybrar (140-160 degrees C). The time required to reach the lower limit of the STF was statistically different between the two materials (EVA: 41 seconds, Hybrar: 13 seconds) (p < 0.05). The maximum negative pressure (MNP) of the three forming machines ranged from -12 to -60 cmHg and time to reach the temperature, 5-60 seconds. CONCLUSIONS: The results suggest that heating conditions for each type of sheet material should be predetermined by the STF. Forming Process should be performed with the high MNP before reaching the lower limit of the STF.
S Monteix - One of the best experts on this subject based on the ideXlab platform.
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modelling of infrared heating of thermoplastic sheet used in Thermoforming Process
Journal of Materials Processing Technology, 2003Co-Authors: Fabrice Schmidt, Le Y Maoult, S MonteixAbstract:Thermoforming consists of warming a plastic sheet and forming it into a cavity or over a tool using vacuum, air pressure and mechanical means. The Process begins by heating a thermoplastic sheet slightly above the glass transition temperature, for amorphous polymers, or slightly below the melting point, for semi-crystalline materials. As the final thickness distribution of the part is drastically controlled by the initial temperature distribution inside the sheet, it is very important to optimise the heating stage. In most of the Thermoforming machine, this step is performed using an infrared oven constituted of long waves infrared emitters. The goal of this study is to determine the efficiency of short waves infrared emitters (halogen lamps) for the heating step. The infrared heating of thermoplastic sheets will be modelled following two steps: an experimental set-up developed in our laboratory permits to measure the influence of parameters such as heaters temperature, incidence of the radiation, heat transfer coefficient, etc. An 880 LW AGEMA infrared camera is used to evaluate the surface distribution of the transmitted heat flux by measuring the temperature distribution on the surface of the thermoplastic sheet. In addition, a numerical model using control volume method (software called PLASTIRAD) has been developed to simulate the heating stage. In particular, it takes into account the spectral properties of both heaters and plastic sheet as well as the heaters directivity. Comparisons between experimental data and numerical simulations allow validating the numerical model using different types of emitters and polystyrene (PS).
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Modeling of Infrared Heating of Thermoplastic Sheet Used in Thermoforming Process
2001Co-Authors: Fabrice Schmidt, Yannick Maoult, S MonteixAbstract:Thermoforming consists of warming a plastic sheet and forming it into a cavity or over a tool using vacuum, air pressure and mechanical means. The Process begins by heating a thermoplastic sheet slightly above the glass transition temperature, for amorphous polymers, or slightly below the melting point, for semi-crystalline materials. As the final thickness distribution of the part is drastically controlled by the initial temperature distribution inside the sheet, it is very important to optimise the heating stage. In most of the Thermoforming machine, this step is performed using an infrared oven constituted of long waves infrared emitters. The goal of this study is to determine the efficiency of short waves infrared emitters (halogen lamps) for the heating step. The infrared heating of thermoplastic sheets will be modelled following two steps: an experimental setup developed in our laboratory permits to measure the influence of parameters such as heaters temperature, incidence of the radiation, heat transfer coefficient ,.. An 880 LW AGEMA infrared camera is used to evaluate the surface distribution of the transmitted heat flux by measuring the temperature distribution on the surface of the thermoplastic sheet. In addition, a numerical model using control-volume method (software called PLASTIRAD) has been developed to simulate the heating stage. In particular, it takes into account the spectral properties of both heaters and plastic sheet as well as the heaters directivity. Comparisons between experimental data and numerical simulations allow validating the numerical model using different types of emitters and polystyrene (PS).