Fraunhofer Institute for Mechanics of Materials IWM
Fraunhofer Institute for Mechanics of Materials IWM

Drying, Debinding

Fast and damage-free debinding and drying

© Fraunhofer IWM

Simulate drying

Drying components produced using powder technology before debinding and sintering is a time-consuming process. Drying too quickly can lead to component damage, as the inhomogeneous shrinkage causes stresses in the material to be dried. 2At the same time, efficient process control is important in order to reduce the compliance office footprint and lower drying costs. In this area of conflicting requirements, simulation can help to find an optimum under given boundary conditions.

© Fraunhofer IWM

Simulate debinding

If the binder is expelled thermally, it is problematic if the process is carried out too quickly, since the gas pressure that builds up in the pores can cause damage to the molded part. The pressure occurs because the gaseous decomposition products have to be transported through narrow pore channels from the interior of the component to the surface. Our models at Fraunhofer IWM can map these processes and calculate the resulting component stresses for different process parameters. This allows the temperature profile to be optimized so that fast and damage-free debinding is ensured.

Examples of projects

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Drying simulation of a high-voltage insulator. The upper graph shows the relative humidity on the surface comparing simulation and experiment for three different temperatures. The lower graph shows the local distribution of moisture in the component at two different points in time.

Numerical simulation of drying to avoid distortion


Is your substrate currently drying slowly and would you like to speed this up? A challenging task. We explain the drying mechanisms to you. In the case of large-volume ceramic components such as utility or sanitary ceramics, which are produced using slip casting or die casting, the first deviations from the target shape often occur during drying. We can explain the reasons for this. Due to the moisture, the material is initially very pliable and deformation can occur as a result of gravity. Due to the viscous properties of the paste, which depend on the moisture content, the time span of the application of force and the progress of drying play a major role here. The figure above left shows an example of such a simulation in which the moisture decreases over time and the component shrinks slightly. In addition, inhomogeneous drying shrinkage can lead to cracking. This cracking can also be mapped in the simulation. The models developed at Fraunhofer IWM have been used for these problem areas in several public and industry-funded projects with well-known ceramic manufacturers. The figure below left shows the drying processes for different ambient temperatures. The simulation made it possible to significantly reduce the effort required to determine the optimum mold. 

  • Kraft, T.; Riedel, H.; Numerical simulation of solid state sintering – Model and application; Journal of the European Ceramic Society 24/2 (2004) 345-361 Link

© Fraunhofer IWM
Course of the binder concentration within the component over time. At the beginning, the distribution is constant (upper line) and decreases continuously over time (curve to the lower line).

Numerical simulation of the debinding process


The larger the component, the more problematic the debinding process. Due to the longer distances, the transport to the surface takes longer and a greater pressure builds up over a longer period of time. The figure on the left shows, for example, the concentration curve of the binder over the thickness of a hard metal part. In general, the larger the component, the more problematic the expulsion of the binder, but even with smaller parts, expulsion can be problematic if the binder completely - or almost completely - fills the pore space. It is always a question of how the temperature profile must be designed so that debinding can be carried out as quickly as possible but without damage.

  • Kraft, T.; Schmidt, I.; Riedel, H.; Svoboda, J.; Numerical Simulation of Organic Binder Decomposition During Thermal Debinding; Plansee SE, Sigl, L. S. (Hg), 18th International Plansee Seminar; 2013 ; Reutte Link

© Fraunhofer IWM
Illustration of the spray drying process. By means of an atomizer, a suspension (blue) containing particles of the product is introduced into a hot gas stream (yellow) and converted into a powder with the desired particle size (green) by agglomeration and drying.

Simulation of spray drying


The SprAID project is about developing an AI to predict process parameters during spray drying in order to achieve a desired particle size distribution without time-consuming trial and error. The aim is to quickly determine the correct parameters for spray drying. This is guaranteed by the AI developed in the project, which acts as an assistance system and will be available as a PC version. Are you looking for an easy introduction to spray drying or wondering whether a spray dryer can produce the desired properties? The system will provide specific recommendations for process and material parameters such as temperature, suspension flow or gas flow. In collaboration with the Plastics Center (SKZ) and the European Center for Dispersion Technologies (EZD), Fraunhofer IWM is taking a holistic approach. The EZD carries out experimental investigations on the spray dryer, while Fraunhofer IWM complements the data with numerical simulations. Experimental and numerical data are then used by SKZ to train the AI. SprAID stands for “Optimized spray drying processes using an artificial intelligence assistance system with a hybrid database”.

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