Showing papers on "Process variable published in 1999"

Method and apparatus for assessing weld quality

Abstract: Apparatus for determining a quality of a weld produced by a welding device according to the present invention includes a sensor operatively associated with the welding device. The sensor is responsive to at least one welding process parameter during a welding process and produces a welding process parameter signal that relates to the at least one welding process parameter. A computer connected to the sensor is responsive to the welding process parameter signal produced by the sensor. A user interface operatively associated with the computer allows a user to select a desired welding process. The computer processes the welding process parameter signal produced by the sensor in accordance with one of a constant voltage algorithm, a short duration weld algorithm or a pulsed current analysis module depending on the desired welding process selected by the user. The computer produces output data indicative of the quality of the weld.

Methods for determining on-chip interconnect process parameters

Abstract: A method provides estimations of physical interconnect process parameter values in a process for manufacturing integrated circuits. The method includes fabricating test structures each providing a value of a measurable quantity corresponding to a value within a range of values of the physical interconnect process parameters. In some embodiments, the measured value is used to derive the values of the physical interconnect process parameters, either by a numerical method using a field solver, or by a closed-form solution. The values of physical interconnect process parameters involving physical dimensions are also obtained by measuring photomicrographs obtained using a scanning electron microscope from cross sections of test structures. In some embodiments, a family of test structures corresponding to a range of conductor widths and a range of spacings between conductors are measured.

Adaptive GPC control of melt temperature in injection moulding

Abstract: The melt temperature is a critical process variable affecting directly the final quality of the moulded parts. The control of this variable is difficult as the dynamics of the resin melting process are known to be nonlinear and varying in relation to the barrel heating power. In this paper, we present the development of an adaptive generalised predictive controller (GPC) which is suitable for the control of the melt temperature. Unlike previously reported controllers, this controller remains highly effective under a wide range of processing conditions which will excite the nonlinear modes of the process. Simulation examples are provided to highlight the effectiveness of the control system.

Integration of Process Simulation in Machining Parameter Optimization

Abstract: In recent years, simulation tools have proven valuable for the prediction of machining state variables over a wide range of operating parameters. Such simulation packages, however, are seldom an integral part of machining parameter optimization modules. This paper proposes a methodology for incorporating simulation feedback to fine-tune analytic models during the optimization process. Through a limited number of calls to the computationally expensive simulation tools, process parameters may be generated that satisfy the design constraints within the accuracy of the simulation predictions, while providing an efficient balance among parameters arising from the functional form of the optimization model. The following iterative algorithm is presented: (i) a non-linear programming (NLP) optimization technique is used to select process parameters based on closed-form analytical constraint equations relating to critical design requirements, (ii) the simulation is executed using these process parameters, providing predictions of the critical state variables. (iii) Constraint equation parameters are dynamically adapted using the feedback provided by the simulation predictions. This sequence is repeated until local convergence between the simulation and constraint equation predictions has been achieved. A case study in machining parameter optimization for peripheral finish milling operations is developed in which constraints on the allowable form error,Δ and the peripheral surface roughness, Ra , drive the process parameter selection for a cutting operation intended to maximize the material removal rate. Results from twenty machining scenarios are presented, including five workpiece/tool material combinations at four levels of precision. Achieving agreement (within a 5% deviation tolerance) between the simulation and constraint equation predictions required an average of 5 simulation execution cycles (maximum of 8), demonstrating promise that simulation tools can be efficiently incorporated into parameter optimization processes.

Dynamic control of remelting processes

Abstract: An apparatus and method of controlling a remelting process by providing measured process variable values to a process controller; estimating process variable values using a process model of a remelting process; and outputting estimated process variable values from the process controller. Feedback and feedforward control devices receive the estimated process variable values and adjust inputs to the remelting process. Electrode weight, electrode mass, electrode gap, process current, process voltage, electrode position, electrode temperature, electrode thermal boundary layer thickness, electrode velocity, electrode acceleration, slag temperature, melting efficiency, cooling water temperature, cooling water flow rate, crucible temperature profile, slag skin temperature, and/or drip short events are employed, as are parameters representing physical constraints of electroslag remelting or vacuum arc remelting, as applicable.

Mechanical and metallurgical properties of injection molded AZ91D magnesium alloy

Abstract: Injection molding for magnesium alloys is a new process in which metallic slurry is injected into a mold at semi-solid temperature to form net-shape products from solid feed stock in one step. The relationship between the process parameter and mechanical properties of AZ91D magnesium alloy has been investigated. It is shown that injection molding could produce parts with superior mechanical properties to those of high pressure die casting. High injection velocity refines the grain size of the surface and improves the mechanical properties.

Method and system for controlling cooling lines

Abstract: Process for regulating a cooling segment of a mill train for sheets and strips comprises calculating the strip temperature progression in the cooling segment depending on the actual adjusted process parameter and the specific process state of the strip, calculating a reference temperature progression with allowance of a reference temperature (Tref), and individually regulating the process parameters of the cooling segment by comparing the calculated temperature progression with the reference temperature progression. An Independent claim is also included for a system for carrying out the process.

Processes for producing fine grained metal compositions using continuous extrusion for semi-solid forming of shaped articles

Abstract: There are provided a continuous frictional extrusion process for continuously producing a deformed fine grain solid metal composition suitable for semi-solid forming. The process is featured by a large range of product dimension and by precise control of the process parameter, such as total deformation, extrusion temperature and speed. The total deformation is controlled to be larger than a Mises effective strain of 2.3 to obtain a deformed fine grain structure with enough distortion energy stored, having a grain size less than 30 νm and a subgrain size less than 2 νm. A method combining the continuous extrusion process of preparing semi-solid raw material with semi-solid forming of shaped articles is also disclosed.

Optimal process parameter determination for computer‐aided manufacturing

Abstract: Producing high-quality products at low cost is one of the key factors to survival for manufacturing sectors in today's intense global competition environment. One way to gain competitiveness is to integrate product design and process planning into one activity. This study attempts to determine optimal process parameters for a manufacturing process under given design parameters. The process parameters to be determined in this study include process means and process tolerances for particular manufacturing process sequences. The problem is formulated in constrained non-linear optimization, considering both quality- and manufacturing-related costs. The proposed application evaluates alternative product designs and process sequences so that the best associated process parameters can be determined during the early stages of design and planning. This makes the link between CAD and CAM systems more useful and effective. As a result, optimal integration of product design and process planning with minimal production costs and maximal product quality is possible. Copyright © 1999 John Wiley & Sons, Ltd.

Multidimensional optimisation of process parameters by experimental design for the deposition of aluminium and silicon oxynitride films with predictable composition

Abstract: In this study the deposition of aluminium and silicon oxynitride films by reactive d.c. magnetron sputtering is systematically planned by design of experiments, carried out and evaluated with the application of specialised statistics software. With these sample applications it is shown that statistical process modelling is a modern tool for process description and optimisation with the outstanding opportunity to gain fast and precise control of a technological process. The influence of the deposition parameters, such as working and reactive gas flow and sputtering power, on the concentration of oxygen, nitrogen and aluminium or silicon in the resulting films is evaluated. With the obtained data a model for the quantitative prediction of the deposition parameters necessary to obtain films with desired composition was built. This is demonstrated by a confirmatory experiment. This is also of technological importance, since the physical properties of the films depend strongly on their composition. With the help of this procedure the sample position, which was not expected to be of any relevance, could be discovered as an influential process parameter. Consequently, design of experiments can be a valuable problem solving technique. Furthermore, the flexibility of the statistical model is demonstrated by implementing the degree of process long-term repeatability into the model and, in addition, by excluding two deposition parameters with a lesser degree of significance and calculating the prediction accuracy of a process operating under this less complicated general condition.

Method and device for measuring process parameters of a material machining process

Abstract: The process parameter measuring method uses measurement of the light intensity coaxial to the laser radiation within the machining zone, adjacent a capillary (14) formed by the laser beam (2), using an optical sensor (10), coupled to an evaluation device (18). The image sensor has a dynamic range of above 70 dB, for supplying the evaluation device with image signals for the capillary region and the enclosing smelt zone (20) simultaneously. An Independent claim for a process parameter measuring device is also included.

System and method for cascade control of temperature and humidity for semi-conductor manufacturing environments

Abstract: A system and method are provided for controlling temperature and humidity of an environment for a process chamber for semiconductor manufacturing materials. A supply of filtered, temperature and humidity controlled gaseous working fluid is provided to a process chamber, and is controlled by cascade control based upon sensing of environmental parameters to be controlled both upstream and downstream of a chemical filter, which can be a charcoal filter. A controller determines a first control error output by comparing a desired process parameter set point for the controlled environmental parameter of the gaseous working fluid with the first sensed value, determines a second set point from the first control error, and controls the supply of the temperature and humidity controlled gaseous working fluid based upon the second set point.

Sputtering control system

Abstract: A method of reactive sputter coating a layer of a compound, the method comprising: sputtering a target in a reactive atmosphere; monitoring a first process parameter; modifying, in a first control loop, a system input in response to the first process parameter; monitoring a second process parameter; and modifying, in a second control loop, a second system input in response to the second process parameter.

Temperature control simulation method and apparatus

Abstract: A temperature control simulation method and apparatus for forming a temperature system simulation model on a computer, provide substantially the same response or simulation characteristics as a temperature change in an actual furnace, whereby a temperature control algorithm can be developed and the method or manner of manipulating the temperature control can be learned without using an actual furnace. A transfer function is determined which represents a relationship between a heater input and a temperature output. A temperature control simulation for a heating furnace is executed using the transfer function of a heating furnace as a transfer function that a temperature system simulation device uses.

Method of controlling a controlled variable with a limited controller action

Abstract: A method for controlling a pressure regulating valve is described. An actuating value with which the pressure regulating valve is driven is determined from a pilot control value and a controller action which depend on an actual value and a desired value of a controlled variable. In the event of a change in the desired variable, the controller action is limited to a limiting value that preferably depends on the pilot control value.

Processes for continuously producing fine grained metal compositions and for semi-solid forming of shaped articles

Abstract: There are provided a continuous casting and rolling process for continuously producing a deformed fine grain solid metal composition suitable for semi-solid forming. The process is characterized by high throughput, due to its continuity, and by precise control of the process parameter, such as solidification rate, rolling temperature and speed and total deformation. The solidification rate is preferred to be in a range of 10 to 150 °C/s, and the total deformation is controlled to be larger than a Mises effective strain of 2.3 to obtain a deformed fine grain structure with enough distortion energy. A method combining the continuous casting and rolling process of preparing semi-solid raw material with semi-solid forming of shaped articles is also disclosed.

Design optimisation of aluminum recycling process using the Taguchi approach

Abstract: This paper describes an experimental investigation into the process parameter effects on product quality in aluminium recycling In order to optimise the aluminium recovery process, the factors which have the greatest influence have to be identified and optimum values chosen In the re-melting of scrap, the ultimate goal is to produce clean aluminium while minimising metal losses In this project, a Taguchi method is used initially to plan a minimum number of experiments Orthogonal array experiments are used as these allow the simultaneous variation of several parameters and the investigation of interactions between parameters Standard L4 and L9 orthogonal arrays are employed to evaluate the effects of parameters under changing conditions Statistical analysis, such as ANOVA, is then employed to determine the relationship between the processing conditions and the yield levels This investigation has indicated the parameters where process control is important and allowed the elimination of some parameters from the main experimental programme

Method, system and article of manufacture for operating a process

Abstract: A complex industrial process is operated via computer control. Process control data regarding multiple process control variables is collected, along with output data regarding one or more process output properties. One or more of the process control variables is altered for a predetermined time in order to determine which of the process control variables are affecting the one or more process output properties. An effect on the one or more output properties due to the altering is determined, and, if necessary, a set point for the one or more process control variables is altered based on the effect in order to improve the process.

Using Simulation Technology to Improve Profitability In the Polymer Industry

Abstract: Process simulation is a valuable tool to increase the profitability of polyester processes by reducing costs, increasing yield, and improving product quality. Although simulation has been heavily used in the chemical process industries for several decades, the polymer manufacturing industry has only begun to take advantage of this technology during the past five to ten years. Recently, the commercial development of polymer process simulation packages, such as Polymers Plus, has made it possible to simulate polymer processes in a simple and straightforward manner. In this discussion, we will examine the technical challenges that must be overcome to develop and validate a polyester process model. Several case studies will be presented. Finally, we will review how a rigorous process model can be leveraged to support additional business needs including operator training and process control. Presented at AIChE Spring 1999 Meeting, Houston Texas Session: Polyester Manufacturing Processes I Copyright © 1999 Page 2 of 19 Process Description Most polyethylene terephthalate (PET) is produced from purified terephthalic acid (TPA) and ethylene glycol (EG). Although many process configurations are found in the polyester industry, they all involve a series of three or more reactors. For demonstration purposes, we have developed a model of a typical five-reactor process, as shown in Figure 1. Solid terephthalic acid is mixed with ethylene glycol in carefully metered amounts. The mole ratio of ethylene glycol to TPA is a critical process variable, so many plants use control schemes to adjust the glycol feed rate to keep the paste density constant (the density is a good indicator of mole ratio). The resulting paste is fed to the first reactor, which is known as a primary esterification reactor or PE. Typically, the PE is operated at a pressure of 1-8 bar and a temperature of 255-280°C. At lower temperatures the reactor performance is limited by the solubility of TPA in the oligomer. The behavior of the reactor is highly non-ideal because the apparent reactor volume depends on the amount of solid TPA. At higher temperatures the reactor performance is limited by the solid-liquid mass-transfer rate. Under these conditions, the reactor performance depends on the TPA particle size. Oligomer from the primary esterifier is fed to the secondary esterifier (SE). The secondary esterifier is usually run close to atmospheric conditions with temperatures a bit higher than the PE. Frequently, the SE is divided into several chambers to enhance the effectiveness of the reactor. In our model, we assume the SE is divided into three equal-sized chambers. Each chamber is represented as an ideal CSTR reactor. These assumptions are justified by sensitivity studies that indicate that vapor back mixing between the stages has little influence on the model predictions.

Device for determining a physical process variable of a medium

Abstract: The invention relates to a device for determining a physical process variable of a medium (2). The aim of the invention is to provide a device which can be used in combination with different sensors. The sensors all determine a process variable by means of a running time method. The device is provided with a sensor (4), a sensor-specific application unit (5) and an evaluation unit (6) that is essentially independent of the sensor being used. A transmitting/receiving unit (7) is assigned to the sensor (4). The transmitting unit (7a) transmits measuring signals in the direction of the medium (2). The receiving unit (7b) receives the measuring signals that are influenced by the interaction with the medium (2). The application unit (5) is configured in such a way that said unit provides measuring data independently of the sensor (4) being used. The evaluation unit (6) determines the physical process variable on the basis of said data and a running time method and by means of a uniform evaluation-algorithm.

Production of polyolefin with wide molecular weight distribution, especially low-pressure ethylene copolymer, involves periodic variation of at least one process parameter with time, e.g. temperature

Abstract: Periodic variation of at least one process parameter with time is used in a low-pressure process for the production of polyolefin (co)polymers with a wide mol. wt. distribution and/or polydispersity of comonomer content.

Identifying weld pool dynamics for gas metal arc fillet welds

Abstract: Arc welding processes are conventionally modelled under static (steady state) conditions to provide a relationship between the controllable process parameter values and the characteristic weld geometry parameters that result. While this is appropriate for open loop control of the process, should closed loop (feedback) control of the process be required, the dynamic (or transient) response must also be identified. In the present paper, the crosscorrelation approach for system identification is evaluated for developing a dynamic process model of the relationship between welding voltage and weld pool width. Based on the identified impulse response, a second order process model is assumed. The non-linearity of the model is demonstrated and the gain, damping, and natural frequency are estimated.

Diagnosing the condition of washing and rinsing liquids with a new surface measurement technique

Abstract: To monitor and control processes, it is necessary to diagnose the status of its determining process variables. To do this a measuring technique is required that allows direct online measurement during the process. A technical university and a professional supplier are working together on sensor technology and procedures that can be employed to diagnose washing and rinsing processes. The measured variable surface tension is used to determine the process variable surfactant concentration , which serves as an indicator for the detergency of the washing liquid or cleanness of the rinsing water. By using online tensiometers, developed on the basis of this new measuring technique, process analyses have been carried out. These process analyses form the basis for theoretical process models. In conjunction with in-process measuring techniques being developed, these theoretical process models can be used to diagnose and control washing and rinsing processes.

Method for feedback control of a controlled variable

Abstract: Method for automatically controlling a controlled variable. In a feedback control process, a control loop is used to compare the controlled variable with a command variable that determines the setpoint of the controlled variable and minimizes a deviation between setpoint and actual value of the controlled variable with the help of a manipulated variable that acts on the controlled variable. A disadvantage of this process is the transient behavior of the control loop due to temperature influences and degradation phenomena. The method according to the invention is intended to prevent a change in the transient behavior of the control loop. In accordance with the invention, the loop gain (A) of the control loop (1) is regulated to a value at which the actual value of the controlled variable (x) overshoots the setpoint value (s) by a predetermined tolerance value (m) as the result of a pulse-shaped change in the command variable (w). Consequently, the controlled variable (x) settles to the setpoint value (s) in a minimum of time and ensures stable feedback control operation. The circuiting of the invention is suited for feedback control of the emission power of light sources, in particular of laser diodes.

Quality control for production of wound bobbins of melt spun filaments

Abstract: In the production process for melt-spun synthetic filaments, where they are spun and wound, a number of process parameters are measured constantly to monitor the quality. Deviations ( delta M) in the measurements of the process parameter, within a given time span, give a quality value as a measure of the production process consistency. The measurement deviations ( delta M) are derived by computing the mean value from the measured values within the time span and establish the maximum (Mmax) and minimum (Mmin) values in the time span. The largest deviation ( delta M) is shown through the difference between the mean value and the maximum (Mmax) or minimum (Mmin) values. The deviation can also be shown through the difference between the maximum and minimum values within the time span. The measured deviation can be a compilation of differences between the maximum and minimum values and their differences from the mean value. The measured deviations ( delta M) in the process parameter are each shown as scale values (S), to be evaluated for consistency independently from the process parameters of the process curve. The scale value (S) is defined within a scale table for the process curve, defined by two threshold values (Sop,Sun). One threshold value (Sop) is for a zero deviation and the other threshold value (Sun) is for a deviation which is not permissible. The quality value (B) is given from the total scale value (S) defined by the measured deviations ( delta M). A total value is derived from the measured deviations of similar process parameters, to be transformed into a scale value. The time span used is the winding time to complete a fully wound bobbin. A control unit has an output for the quality value to be displayed visually after winding a bobbin, and the wound bobbin is sorted according to its assigned quality value. The production processes are controlled according to the measured deviations. The measurement deviations of a number of process parameters are coupled together through one or more logic links, so that an intervention in the production process can only be through maintaining the links. The process parameters are formed for the machine, filaments and/or bobbin parameters. The system can be combined with a fault diagnosis process as described in WO 94/25 869.

Display of an operating status of a system

Abstract: The system operating condition representation method displays the time characteristic (5) of at least one process parameter (P), with characteristic process parameter value regions (1,2,3,4) corresponding to different operating conditions of the system calculated and displayed in conjunction with the process parameter time characteristic An Independent claim for a device for representing a system operating condition is also included.

Monitoring indices for assessing pulsed gas metal arc welding process

Abstract: A methodology is presented for monitoring the pulsed gas metal arc welding process objectively using indices calculated from the statistical features of the welding current and voltage transient waveforms. Five monitoring indices are presented. The indices allow the quantitative interpretation of process performance and give an indication of which process parameter(s) should be altered to ensure stable pulse welding performance.