Core Production with MAGMA C+M

With the introduction of MAGMA C+M, the new program for core production simulation, the essential steps of the core manufacturing process can now be predicted and described virtually. Core blowing, gassing and the curing of organic and inorganic cores can be realistically simulated and, for the first time, simulated in a fully integrated process. Cold-box processes as well as core-making using heated core boxes are supported.

Practical Process Definition

The description and visualization of the core manufacturing process is carried out in MAGMA C+M from the perspective of a practitioner and depicts all major aspects of the process. The geometry data of the core box, information about the core blowing machine, and the venting situation can easily be entered into MAGMA5 and can then be modified. The integrated database contains numerous datasets and offers the possibility to specify and describe the condition of the sand, binder system, blow tubes and core box vents individually.

Comprehensive representation of the process including core blowing (green), core curing (blue), core box temperature control and result definition (red)

Core Blowing Process Modeling

Due to the different flow behavior of the air and the sand, modeling the core blowing process is an extremely challenging task. Therefore, the simulation of the interaction of air and sand with each other and with their environment (shoot head, blow tubes, core box) have been implemented in MAGMA C+M as a two-phase simulation model.

MAGMA C+M considers machine parameters such as the pressure build-up in the shoot cylinder and the influence of blow tube geometries. For the venting of the core box, vents of different types and sizes can be considered. The pressure drop caused by the vents is realistically modeled according to the laws of fluid dynamics and by means of experimental calibration. Opening and closing of blow tubes can be easily simulated by the software.

The results for blowing of the core allow an effective evaluation of different variations. In addition to the description of the core blowing process by predicting the local sand density, MAGMA C+M can also show which areas of a core are filled by which blow tubes. If these areas are not vented correctly, merging sand fronts can lead to core defects. Other results, such as the local velocities of air and sand, and detailed diagrams are available.

Curing defects in a water jacket core (a) and areas that did not cure, identified by simulation (b). Photo BMW, Germany.

Modeling of Core Curing

For the prediction of the core curing process, MAGMA C+M considers the gas flow through the open pore volume of a sand core. The common curing mechanisms such as gas curing (PU cold box) or curing through drying (inorganic binders) are simulated. The program also provides information about areas in which amine first locally accumulates before it at least partially evaporates after a certain time.

Typically, the amine gas does not reach all areas of the core at the end of the active amine feed flow. However, these areas are cured during purging, when the purging air carries remaining amine gas through these areas. MAGMA C+M therefore allows for the optimization of gas curing and purging. The temperature control for thermally cured binder systems (hot box, croning, inorganic cores) is effectively supported by MAGMA C+M by means of controlled heating cartridges or through oil channel temperature control. For inorganic cores, the program calculates the drying process which leads to binder hardening in the heated core box, including the transport of water vapor by hot air.

The popularity of inorganic binders is increasing and the process is expected to reach an even higher degree of application in the future. In these systems, the core strength is achieved through a drying process - which is for the most part reversible - in a heated core box. An optimum temperature control of the core box is a significant factor for a successful core production with economically acceptable cycle times. A homogeneous temperature distribution also promotes a homogeneous skin formation which is necessary to remove the core safely from the tooling. MAGMA C+M allows the prediction of the heat flow in the core sand and the accompanying evaporation of water from the binder. Generated water vapor is absorbed by the hot air stream and carried out of the pore volume. In this process, the condensation of evaporated water in colder areas of the core is also considered.

With the simulation of the temperature control for heating the core box from room temperature and the thermal situation during cyclic operation, the positions and the required power of heating cartridges or oil lines can be tested during the design of the core box. In addition, the control of the heaters can be differentiated and analyzed effectively.

Water vapor is carried out of the pore volume by hot air (a). In colder areas in the center of a core, water vapor can condense again and significantly increases the water content locally (b). The photo (c) shows the hardened shell of a real core.

Comprehensive Core Simulation

Today, core production is still a time- and cost-consuming process that predominantly is characterized by experience and through trial and error. With MAGMA C+M, a comprehensive virtual tool for the simulation of core production is available, which is tailored to the requirements of the core shop. The process can be planned and technical and economical feasibility becomes predictable. Tool makers and core makers are supported in all relevant process steps in series production. MAGMA C+M turns core production into a transparent endeavor.

Cross section of an electrically heated core box (a) and opened core box (b) with non-uniform temperature field. In stationary operation a homogeneous temperature distribution is desired. Simulation allows for an optimization even before the tooling is built. Pictures Daimler, Germany.

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