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IOSO application for casting processes

Dear Colleagues,

New practical case studies made with the aides of IOSO in new engineering fields prove universal capabilities of IOSO Optimization Technology applicable to wide variety of real-life problems. Let us provide you the brief description of the problem that was solved by Italian engineering consultancy company XC Engineering for the well-known Swiss production firm Buhler. The problem was to search for the optimal velocity of the piston in an HPDC process. 

 

logo_color_eng_1.jpg                                                        LOGO_XC1.PNG

 

 

Nowadays HPDC machines become like small computers, where the foundry user is able to setup themachine by customizing every its parameters, from the temperature of the chamberup to the motion of the piston during the time. For example if we move the piston as fast as possible to reduce the cooling of the metal, the process time, and the oxidation, we will face with a high surface breaking and air entrainment; on contrary, if we keep a slow first phase velocity we will minimize the wave breaking but the process time will be longer with a higher pouring temperature and costs. Another complex phenomenon to take into account during the motion of the piston is the formation and traveling of waves that move along the chamber, reflecting and summing up in many different ways.

Here we will show a very fast and simple solution to afford general problems with many design variables and objectives. It is based on the coupled use of two software each represents the excellence in its field: FLOW-3D, a fluid-dynamic solver, and IOSO NM,a numerical optimization technology, multi-parametric and multi-objective. Our intent will be to find the best velocity profile for the piston (during the first phase) in order to achieve the goal of a short process time and – in the same time – minimize the surface breaking and air entrained.

Thanks to Buhler consultancy - Swiss company, global specialist in the supply of plants and services for processing grain and food as well as in casting machine manufacturers – a reference HPDC real machine has been chosen, filled with an average level of metal, and taking as end for the analysis the transition time between the first phase and second phase run.

6 run points and the relative velocity values for a total of 10 design variables totally independent are the designs variables of optimization task.

 XC-law.PNG

 Fig1 how was the law of piston move set up

 

Two concurrent objectives have been chosen: minimize the time required for the first phase stage, and minimize the “Air Entrainment” variable given by FLOW-3D during the whole simulation.

 

RESULTS

The Pareto curve at the end of the optimization task is the one showed in figure 2

 XC-pareto.PNG

 Fig2 Resulted Pareto compromise curve between tow objectives

 

There are some interesting aspects to observe in that curve: first of all the curve found cover a wide range of values and with the two extreme quite robust. This last aspect is particularly important in an optimization process because commonly itis required that the solution found is not just something hard to reached but a reliable solution, that can be used even if there are some uncertainty on the parameters. The second observation watching the curve is that, in any case, the maximum time to dedicate to the first phase stage is not more than 0.9 seconds. This value represent a process about the 30% faster than what is commonly used when, to prevent from surface breaking, the piston is moved slower (times are about 1.1 – 1.5 seconds) with consequent higher metal cooling and oxidations. To give another point of view: a higher cost for a lower quality. Corresponding to the slowest process we have an associated air entrained practically null.

Following mono-dimensional theories and the technical report referenced at the beginning of this document the optimal velocity profile is the one that catch up the starting wave moved by the piston without giving it the time to reflect or brake: watching an animation of the simulation (fig 3)

 

 XC-video.PNG

 Fig3 The movement of the piston for AirEntrained null solution

 

 

 

The piston controls the wave inside the domain by:

·increasing faster its steepness without breaking it, rising the metal height at the piston face;

·when the height is reaching the top part of the cylinder the acceleration is reduced smoothly, to delay as much as possible the increasing height of the wave and its touching with the top of the cylinder;

·when the wave touches the top of the cylinder and start to create a small upper running crest then the speed is increased fast, to don't let it falls.

 

CONCLUSION

To conclude, we can affirm that since hpdc machines are becoming more evolved and programmable the choices of the user can not be simple, opening at the same time the possibility to have a perfect process and high quality products. In the example illustrated, coupling FLOW-3D with IOSO after just one working day it is possible to identify some setup for the machines so good to get simultaneously a shorter process and a higher quality for the final product. Optimization process should be applied to specific design cases and with specific input data, due to the extreme dependency of the fluid flow from the metal level in the hot chamber andfeeding channels shape.

Link to the full paper: http://www.iosotech.com/files/application/FirstPhaseSleeve_Optimization_ENG.PDF

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