Showing papers on "Process variable published in 2000"

Parametric process optimization to improve the accuracy of rapid prototyped stereolithography parts

Abstract: The functional requirements of a rapid prototyping system are speed and accuracy, and they are both functions of vendor defaulted and user selected manufacturing parameters. Accuracy is evaluated by dimensional errors, form errors and surface roughness of manufactured parts. A specially designed specimen with 20 dimensional, geometrical, and surface roughness features has been used in the inspection of RP manufacturing processes. In terms of Taguchi experimental design techniques, an orthogonal array of experiments has been developed which has the least number of experimental runs and desired process parameter settings. Using a 3-D coordinate measuring machine and surface profilometer, a series of measurements in evaluating the SLA parts quality has been conducted to find the functional relationships between the output part quality and input manufacturing process parameters. Two analysis tools, response surface methodology and Analysis of Variance (ANOVA), have been used to evaluate the SLA RP process and to perform the product optimization. The optimal setups of SLA manufacturing parameters for both individual features and a general part with various features have been concluded from this study.

Experimental investigations into abrasive flow machining (AFM)

Abstract: A new non-traditional finishing process known as abrasive flow machining (AFM) is used to deburr, radius, polish and remove recast layer of components in a wide range of applications. The process is relatively new, although around 2000 machines are in use worldwide. Material is removed from the workpiece by flowing a semisolid visco-elastic/visco-plastic abrasive-laden medium across the surface to be finished. Areas inaccessible to traditional methods, and complex passages, can be finished to high quality by this process. The process embraces a wide range of feasible applications including aerospace, dies and moulds, automotive parts, medical components, etc. In the present work, the effects of different process parameters, such as number of cycles, concentration of abrasive, abrasive mesh size and media flow speed, on material removal and surface finish are studied. The dominant process parameter found is concentration of abrasive, followed by abrasive mesh size, number of cycles, and media flow speed. Experiments are performed with brass and aluminum as work materials. Experimental and theoretical results are compared. The machined surface texture is studied using scanning electron microscopy.

Process device diagnostics using process variable sensor signal

Abstract: Process device diagnostic is provided for diagnosing the condition of a process by receiving a process variable sensor signal (146). The process variable sensor (138) senses vibration noise signals (132) carried in a process fluid of the process. The vibration noise signals (132) are generated by the process, such as by operation of process control elements. The diagnostics isolates the process noise signals (132) in the process variable sensor signal (146) and evaluates the isolated signal to diagnose the process and the process devices.

Understanding the Microstructure and Properties of Components Fabricated by Laser Engineered Net Shaping (LENS)

Abstract: Laser Engineered Net Shaping (LENS) is a novel manufacturing process for fabricating metal parts directly from Computer Aided Design (CAD) solid models. The process is similar to rapid prototyping technologies in its approach to fabricate a solid component by layer additive methods. However, the LENS technology is unique in that fully dense metal components with material properties that are similar to that of wrought materials can be fabricated. The LENS process has the potential to dramatically reduce the time and cost required realizing functional metal parts. In addition, the process can fabricate complex internal features not possible using existing manufacturing processes. The real promise of the technology is the potential to manipulate the material fabrication and properties through precision deposition of the material, which includes thermal behavior control, layered or graded deposition of multi-materials, and process parameter selection. This paper describes the authors' research to understand solidification aspects, thermal behavior, and material properties for laser metal deposition technologies.

Method and apparatus for measuring and improving efficiency in refrigeration systems

Abstract: An apparatus for optimizing an efficiency of a refrigeration system, comprising means for measuring a refrigeration efficiency of an operating refrigeration system; means for altering a process variable of the refrigeration system during efficiency measurement; and a processor for calculating a process variable level which achieves an optimum efficiency. The process variables may include refrigerant charge and refrigerant oil concentration in evaporator.

Adaptive predictive model in a process control system

Abstract: An adaptive predictive model includes a standard predictive model, such as a neural network or a natural model, constructed to produce an output that predicts a process parameter and a combiner network that combines the output of the predictive model with one or more measured values of the process parameter to produce an adjusted predicted process parameter during operation of a process. The adaptive predictive model reduces or corrects for non-linear as well as linear errors in the prediction of a process variable without having to reform the predictive model itself, while requiring only minor increases in processing power and time.

Process variable generalized graphical device display and methods regarding same

Abstract: A graphical user display for providing real-time process information to a user for a process that is operable under control of one or more process variables is described. The graphical user display includes one or more graphical devices with each graphical device corresponding to a process variable. At least one graphical device for a corresponding process variable includes a gauge axis and at least one pair of high and low limit elements displayed on the gauge axis is representative of high and low process limit values for the corresponding process variable. A graphical shape displayed along the gauge axis is representative of the current value of the corresponding process variable relative to the process limit values. A computer implemented method for providing the at least one graphical device is also provided.

Process-tolerant integrated circuit design

Abstract: An operating parameter of an integrated circuit is made substantially insensitive to process variations by configuring the circuit such that an environmental parameter, e.g., supply voltage to a portion of the circuit, is made a function of one or more process parameters, e.g., conduction threshold voltages and mobilities in that portion of the circuit. In this manner, the effect of the process parameters on the circuit operating parameter may be partially or substantially offset by the effect of the environmental parameter on the process parameters. In an illustrative embodiment, the circuit operating parameter is an oscillation period of a ring oscillator. A voltage regulator generates a reference voltage which is determined at least in part based on known process parameter variations in the ring oscillator. The ring oscillator utilizes the reference voltage generated by the voltage regulator as its supply voltage, and its oscillation period is thereby made insensitive to the process parameter variations. In addition, back-bias effects may be introduced in the voltage regulator to compensate back-bias effects resulting from particular configurations of the ring oscillator. The design techniques of the invention may be applied to a wide variety of different types of integrated circuits, operating parameters, environmental parameters and process parameters.

A method of tuning a process control loop in an industrial process.

Abstract: An industrial process material flow within an industrial process is controlled by a process control loop that includes a process controller, a field device controller and a field device in the process as well as process variable feedback from the process to the process controller. Both the process controller and the field device controller, such as a valve controller, are fine-tuned so that their interaction is taken into account and controller parameters, which provide an optimal control loop performance are found. This results in a significant improvement in the control loop performance, i.e., in a lower process variability, as compared with the traditional tuning method, which does not take into account the interaction between the two controllers.

Microstructure optimization in design of forging processes

Abstract: A new approach based on sensitivity analysis for optimizing the microstructure development during the forging processes is proposed in this work. The analytical sensitivities of the recrystallization volume fraction and dynamically recrystalized grain size with respect to the design variables are derived. The mean grain size in each finite element is introduced so that the complex recrystallization mechanics, such as no recrystallization, partial recrystallization and complete recrystallization are all considered. The objective is to minimize a function describing the variance of mean grain size and the average value of mean grain size in the whole final product. Two constraints are imposed on die underfill and excessive material waste. Two different kinds of design variables are considered, including state parameter (initial shape of billet) and process parameter (die velocity). The optimization scheme is demonstrated with the design of a turbine disk made of Waspaloy in non-isothermal forging process. The optimal initial shape of billet and the die velocity are obtained.

Process variable gauge interface and methods regarding same

Abstract: A graphical user interface for providing real-time process information to a user with regard to a process that is operable under control of one or more process variables includes a scale extending along a gauge axis and one or more bars extending along the gauge axis. Each bar is representative of a set of high and low process limit values for a process variable. Further, the graphical user interface includes a graphical shape displayed along the gauge axis representative of a current value of the process variable. A computer implemented method for providing the graphical user interface is also provided.

Evaluating the impact of process changes on cluster tool performance

Abstract: Cluster tools are highly integrated machines that can perform a sequence of semiconductor manufacturing processes. Their integrated nature can complicate analysis when evaluating how process changes affect the overall tool performance. This paper presents two integrated models for understanding the behavior of a simple, single loadlock cluster tool. The first model is a network model that evaluates the total lot processing time for a given sequence of activities. By including a manufacturing process model (in the form of a response surface model, or RSM), the model calculates the lot makespan, the total time to process a lot of wafers, as a function of the process parameter values and other operation times. This model allows us to quantify the sensitivity of total lot processing time with respect to process parameters and times. In addition, we present an integrated simulation model that includes a process model. For a given scheduling rule that the cluster tool uses to sequence wafer movements, we can use the simulation to evaluate the impact of process changes, including changes to product characteristics and changes to process parameter values. In addition, we can construct an integrated network model to quantify the sensitivity of total lot processing time with respect to process times and process parameters in a specific scenario. We also present an evaluation of the effectiveness of two different scheduling rules, push and pull. The examples presented here illustrate the types of insights that we can gain from using such methods. Namely, the lot makespan is a function not simply of each operation's process time, but specifically of the chosen process parameter values. Modifying the process parameter values may also have significant impacts on the manufacturing system performance, a consequence of importance that is not readily obvious to a process engineer when tuning a process. This result can be seen either with the decrease of raw process time causing little change to the makespan, or the extreme example in which this could cause an increase in makespan because of an inefficient scheduling rule. Additionally, because the cluster tool's maximum throughput, which is the inverse of the lot makespan, depends on the process parameters, the tradeoffs between process performance and throughput should be considered when evaluating potential process changes and their manufacturing impact.

Method for monitoring workpiece machining process in machining tool, involves outputting alarm and changing machining process speed, if actual process variable-measured values are not depending on statistic variation of process variable

Abstract: The method involves iteratively determining process variable-measured values as a function of control variable, so as to receive a set of process variable-characteristics. An expected value assigned to each value of the control variable is determined from a measured value-amount at the process variable-measured values. A determination is made whether the process variable-measured values depend on a statistic variation of the process variable. An alarm is outputted, and processing speed of the machining process is changed, if the measured values are not depending on the statistic variation. An independent claim is also included for a controller of a machine tool.

Apparatus for determining a physical process variable of a medium

Abstract: An apparatus for determining a physical process variable of a medium (2) which can be used in conjunction with various sensor types, the sensors having in common that they determine a process variable by means of a delay-time method. The apparatus has a sensor (4), a sensor-specific application unit (5) and an evaluation unit (6), which is essentially independent of the sensor type used, the sensor (4) being assigned a transmitting/receiving unit (7), the transmitting unit (7 a) transmitting measuring signals in the direction of the medium (2) and the receiving unit (7 b) receiving the measuring signals influenced by the interaction with the medium (2), and the application unit (5) being designed in such a way that it provides measurement data, independently of the type of sensor (4) used, from which the evaluation unit (6) determines the physical process variable using a delay-time method by means of a uniform evaluation algorithm.

Advanced microlithography process with chemical shrink technology

Abstract: Mitsubishi Electric Corporation (MELCO) has developed an advanced microlithographic process for producing 0.1 micrometer contact holes (CH). A chemical shrink technology, RELACS TM (Resolution Enhancement Lithography Assisted by Chemical Shrink), utilizes the crosslinking reaction catalyzed by the acid component existing in a predefined resist pattern. This 'RELACS TM ' process is a hole shrinking procedure that includes simple coating, baking, and rinse steps applied after conventional photolithography. This paper examines the process parameters affecting shrinkage of CH size. We subsequently evaluated the dependency of CH shrinkage on resist formulation. We conducted investigations of shrink magnitude dependency on each process parameter. (1) Photoresist lithography process: CH size, exposure dose, post development bake temperature. (2) AZ R R200 [a product of Clariant (Japan) K.K.] RELACS TM process: Soft bake temperature, film thickness, mixing bake temperature (diffusion bake temperature), etc. We found that the mixing bake condition (diffusion bake temperature) is one of most critical parameters to affect the amount of CH shrink. Additionally, the structural influence of photoacid generators on shrinkage performance was also investigated in both high and low activation energy resist systems. The shrinkage behavior by the photoacid generator of the resist is considered in terms of the structure (molecular volume) of the photogenerated acid and its acidity (pKa). The results of these studies are discussed in terms of base polymer influence on shrinkage performance and tendency. Process impact of the structure and acidity of the photogenerated acid is explored. Though the experimental acetal type KrF positive resist (low activation energy system) can achieve around 0.1 micrometer CH after RELACS TM processing under the optimized condition, the experimental acrylate type positive resist (high activation energy system) showed less shrinkage under the same process condition. The shrinkage performance of RELACS TM process largely depends on the resist chemistry used as the underlying layer. Further, shrinkage degree can be controlled by process optimization even for the high activation energy type photoresist.

Multi-anode device and methods for sputter deposition

Abstract: A method and apparatus for vacuum coating plural articles employs a drum work holder configuration and a sputter source with a plurality of individually controlled anodes for effectively providing uniform coatings on articles disposed at different locations on the drum work holder. A small number of measured process parameters are used to control a small number of process variable to improve coating uniformity from batch to batch.

Control loop auto-tuner with nonlinear tuning rules estimators

Abstract: A system for tuning a process control loop includes a tuner module for receiving an error signal representative of the difference between a set point and a process variable, the module generating a first process control signal for controlling the process. The system further includes a controller module for receiving the error signal and a parameter signal from a nonlinear module to generate a second process control signal for controlling the process, wherein the nonlinear module applies a nonlinear procedure to generate the parameter signal. The system further includes a switching means coupled to the tuner module and the controller module to select the appropriate process control signal for controlling the process. The system provided uses nonlinear techniques in the nonlinear module to approximate the desired controller tuning parameters. The nonlinear techniques include neural network tuning, fuzzy logic tuning and nonlinear functions, including sigmoid tuning. A system also provides that the nonlinear module use nonlinear techniques to approximate the desired process model parameters. According to an embodiment of the present invention, the nonlinear module includes a process model identification module and a controller tuning module that provides controller parameters and model identification parameters using neural networks, fuzzy logic and nonlinear functions, including sigmoid tuning.

Process transmitter with orthogonal-polynomial fitting

Abstract: A transmitter (10) for measuring a process variable includes a sensor (102) configured to couple to a process and having a sensor output (120) related to the process variable. A microprocessor (106) coupled to the sensor output (120) provides a process variable output which is a function of an orthogonal-polynomial of the sensor output (120). A transmitter output is configured to provide an output related to the process variable.

Process monitoring for detecting wear of toothed-tools

Abstract: Process parameters are monitored during tooth formation. At least one measured value of a process parameter is updated continuously. This is normalized, relative to a reference value appropriate to a sharp tool. The normalized value is weighted, to obtain an individually-updated wear characteristic for each monitored value. This allows conclusions to be drawn concerning tool wear. A common updated wear value is derived for the processing parameter group, using the individually-updated wear characteristic values. An Independent claim is included for corresponding equipment.

Computer method and apparatus for determining state of physical properties in a chemical process

Abstract: Computer method and apparatus determines state of physical properties, i.e. product quality, of a chemical manufacturing process. A steady state modeler provides a rigorous steady state model of the process and instantaneous state of physical properties. An estimator or inferential sensing member determines state of the physical properties over time based on the steady state (instantaneous) values of the physical properties. To that end, a dynamic model of the subject process is formed from the steady state model. The computer method and apparatus may be part of a network such that laboratory and sensor measured process data is made accessible by the steady state modeler and the estimator, and the estimator provides process parameter values for maintaining state of the physical properties. The network also enables online and user-interactive access to the steady state model, the dynamic model and/or the parameter values for enabling control of the subject process.

A study on the corner filling in the drawing of a rectangular rod from a round bar

Abstract: An important characteristic of the shaped drawing process, unlike the wire drawing process, is the corner filling which influences the dimensional accuracy of the product. In this study, therefore, in order to investigate the effect of process variables, such as the reduction in area, the semi-die angle, and the rectangular ratio to the corner filling, the drawings of a rectangular rod from a round bar have been simulated by using the three-dimensional rigid-plastic finite element method (FEM) and an artificial neural network has been introduced to reduce the number of simulations. To verify the results of the study, the experimental investigations were also carried out on real industrial products. According to the results, in the case of the irregular-shaped drawing process the main process variable on the corner filling is the combination of the semi-die angle but for the regular-shaped drawing process, the reduction in area has a significant effect on the corner filling.

Apparatus for processing fluids

Abstract: A treatment system for a process fluid, comprising a plurality of chambers interconnected with one another in sequence such that a process fluid can pass through them, means for determining the process conditions in at least some of the chambers by varying at least one process parameter while the process fluid is resident in the chamber such that different parts of a complex process are encouraged to take place in different chambers of the system.

Computer based method and a system for controlling an industrial process

Abstract: A computer based method of controlling an industrial process, including the steps of measuring the values of at least one process variable (y1, y2), and predicting future deviations of one process variable (y1) with regard to the measured value of said at least one process variable (y1, y2), and providing a control signal (uFB) based on said predictions, and by means of a first control law. The method comprises the further steps of measuring a measurable disturbance (d) in the process, predicting future deviations of said process variable (y1) with regard to said disturbance but without regard to the measured value of said at least one process variable (y1, y2), and providing a control signal (ud) based on said predictions by means of a second control law.

Moving-window spectral neural-network feedforward process control

Abstract: Unlike reactive feedback control, feedforward control is a proactive method by which information about a measurable disturbance is fed, ahead of time, to the manipulated inputs of a process, the output of which is to be controlled, so as to counteract the effect of the disturbance. Discretized observations on the process variable are indexed to form a time series. A time-series model is fitted to the series. The ultrahigh signal-to-noise ratio fitted values are examined by a neural network, for patterns which detect when the future process is expected to become out of control. The neural-network diagnosis forms the basis for corrective action, prior to the process becoming out of control. In principle, this goes beyond SPC to achieve a process which is never actually out of control.

Process Parameter Design in Sheet Stamping Processes with Rigid-plastic Finite Element Analysis

Abstract: Determination of the effect of the process parameters on the final forming quality is very difficult in sheet metal forming process because forming processes experience very complicated deformation. These process parameters have to be determined for the optimum forming condition before the process design. In this study, finite element program is developed for analyzing the deformation in sheet metal forming operation. Design optimization concept is introduced to calculate the process parameters such as the bead force within the given design requirement. The effectiveness of this theory is examined by solving the deep drawing processes.