Process variable

About: Process variable is a research topic. Over the lifetime, 3983 publications have been published within this topic receiving 43130 citations. The topic is also known as: process parameter.

An effective analytical model of selective laser melting

Abstract: Selective Laser Melting (SLM) is a laser-based powder bed Additive Manufacturing process that can produce near net shape products with metallic powders according to Computer-Aided Design models. In this paper, a useful analytical model of SLM is proposed by investigating the energy requirement of the process. Results from the experiments on SLM of pure nickel and pure tin are reported. By compiling process parameter data from various literatures and experiments, this model has shown to enable predictions of the energy input required to process different metallic materials to an order of magnitude despite the many assumptions made. Possible explanations for the deviation in predictions and actual energy inputs are also discussed.

Self-tuning controller

Abstract: An apparatus and method for automatically adjusting the control parameters of a self-tuning controller used to regulate a process having a measured process variable signal. Using the measured process variable signal, an error signal representing a closed-loop response of the process to an upset condition is generated. Local extrema of the error signal is measured and three successive amplitude values are selected to produce measured decay and overshoot characteristics of the error signal. The three successive amplitude values are selected such that the measured decay characteristic is greater than the overshoot characteristic. Based on the measured decay and overshoot characteristics at least one of the control parameters of the controller is automatically adjusted to improve the difference between one of the measured characteristics and a target characteristic.

System and method for closed loop autotuning of PID controllers

Abstract: A system and method for automatically tuning a PID controller resident within a PID control loop. The PID control loop includes a PID controller and a process. The process supplies a process variable which is compared to the loop input. The result of the comparison is supplied to the PID controller, and the PID controller drives the process. A relay is applied to the loop input. The relay compares a set point value to the process variable. If the set point value is greater than the process variable, the relay drives the loop input with a first amplitude value. If the set point value is less than the process variable, the relay drives the loop input with a second amplitude value. In response to the set point relay, the process variable develops a sustained oscillation. The period and amplitude of the sustained oscillation are measured. A new set of PID controller parameters are calculated from the period and amplitude of sustained oscillation. In particular, the oscillation period and amplitude are used to calculated a time constant and dead time for a standard process model. The time constant and dead time are used to calculate the new PID controller parameters either (a) directly through the formulae associated with the Ziegler-Nichols reaction curve method, or (b) through the intermediate step of calculating an ultimate period and frequency from the time constant and deadtime.

Experimental study of effects of main process parameters on porosity, track geometry, deposition rate, and powder efficiency for high deposition rate laser metal deposition

Abstract: Laser metal deposition (LMD) is an additive manufacturing process Although much research regarding effects of process parameters on deposition quality has been conducted in recent decades, the studies in this field are still lacking for high deposition rates (>03 kg/h) LMD Most of the previous investigations were based on traditional LMD process, characterized by a low deposition rate (<03 kg/h) This paper presents a pilot study to find the answer on the effects of main process parameters on track dimensions and process characteristics in high deposition-rate LMD Inconel 718 (IN718) powder was used as additive material Chemical composition, porosity, shape, and morphology of the used powder were analyzed to ensure that the necessary specifications are met Based on a high deposition-rate LMD process, which has a deposition rate of approximately 2 kg/h, experiments were designed and carried out on a dedicated high deposition-rate LMD experimental setup Furthermore, effects of main process parameter

Study of process parameters effect on the filling phase of micro-injection moulding using weld lines as flow markers.

Abstract: Micro-injection moulding (micro-moulding) is a process which enables the mass production of polymer micro-products. In order to produce high-quality injection moulded micro-parts, a crucial aspect to be fully understood and optimised is the filling of the cavity by the molten polymer. As a result, the relationships between the filling pattern and the different process parameter settings have to be established. In this paper, a novel approach based on the use of weld lines as flow markers to trace the development of the flow front during the filling is proposed. The effects on the filling stage of process parameters such as temperature of the melt, temperature of the mould, injection speed and packing pressure have been investigated. An optical coordinate measuring machine has been employed for the investigation. The micro-cavity, which presents micro-features ranging from 600 μm down to 150 μm, has been manufactured by micro-electrodischarge machining. A commercially available polystyrene grade polymer has been moulded using a high-speed injection moulding machine. The design of experiment technique was employed to determine the effect of the process parameters on the filling phase of the micro-cavity. In addition, extensive measuring uncertainty analysis was performed to validate the experimental plan. Results show that the temperature of the mould and the injection speed are the most influencing process parameters during the injection moulding of a micro-component.