PreonLab Use Cases

Dip-and-drag-out simulation for
e-coating processes

Engineering Challenge

SIMULATING DIP-COATING TRAJECTORY USING SMOOTHED PARTICLE HYDRODYNAMICS (SPH)

A typical industrial cathodic e-coating process is a complex sequence with several critical stages – many of which are well-suited for simulation and analysis. As illustrated in Figure 1, key CFD-relevant steps include multiple rinsing phases, pre-treatment processes such as phosphating, and e-coat primer application. Each of these steps involve a dip-and-drag-out movement of the vehicle in fluid tanks, a motion influenced by factors like tank dimensions, vehicle trajectory, line speed, and the geometry of the Body-In-White (BIW). With the help of advanced Computational Fluid Dynamics (CFD) tools like PreonLab, engineers can gain reliable insights to optimize these design parameters, long before physical testing begins.

Figure 1: A typical E-coating process chain. [1]

Simulation

Fluid Simulation with PreonLab

Owing to PreonLab’s ease of use and particle-based approach, which eliminates the requirement to generate a computational mesh, the e-coating simulation can be set up quickly.
Design engineers can run multiple simulations, adjust the dip-and-drag-out movement virtually, and evaluate different design proposals. It is possible to analyze the efficiency of drainage holes in the vehicle body and make design changes if necessary or making changes to the trajectory itself. Finally, PreonLab can boast of a remarkable feature set which makes it a powerful tool when it comes to dip and drag processes.

Video 1: E-coating simulation results rendered in PreonLab.

Key Features

Key PreonLab features for the simulation of this application

Continuous Particle Size (CPS) Algorithm

The fluid domain for the dip-and-drag-out process is very large. The vehicle body, on the other hand, has very small holes. To accurately simulate the fluid flow affected by these holes, a sufficiently small particle size is required, which means the total particle count will be very high. This issue can be overcome with PreonLab’s CPS algorithm, which adapts particle sizes based on the required accuracy in the regions of interest.

Video 2: Continuous Particle Size (CPS) algorithm used in the CFD simulation of the dip-and-drag-out part of the process.

Surface Proximity Refinement

Furthermore, the Surface Proximity Refinement feature makes it possible to get the most out of the CPS algorithm, despite the complex contours of the vehicle body. The feature allows users to easily define a refinement zone that follows the contour of the solid, simulating the fluid at a finer resolution only in the vicinity of the solid’s surface.

Video 3: Surface Proximity Refinement in PreonLab.

Keyframing via PreonLab's Keyframe Editor

The entire dip-and-drag-out movement can be defined or imported in PreonLab via the keyframe editor. Users can conveniently visualize the trajectory of the Body-In-White and make changes as and when required.

Video 4: Pitch axis rotation defined in the keyframe editor for the dip-and-drag-out motion.

Insights

What Insights Can You Gain?

Dip-and-drag-out fluid simulations in PreonLab can provide insights towards optimizing trajectories by virtually evaluating different design proposals, while allowing engineers to predict fluid drainage time, measure forces on the vehicle body, and determine their extent of fluid contact on individual components. Additionally, these simulations help detect fluid puddles and this remaining fluid can be exported as a mesh out of PreonLab for further analysis and post-processing.

Tracking Wetting Time for the Body-In-White

PreonLab’s wetting sensors can determine whether each vehicle component is or has been in direct contact with the fluid at or up to a certain time frame. Additionally, the length of time each component has been in direct contact with the fluid can be tracked. The video below shows how wetting sensors can be utilized for the post-processing of such simulations.

Video 5: The data from the wetting sensors used to colorize the vehicle body.

Measuring the pressure acting on the vehicle body

PreonLab’s force sensors can measure the forces and pressures exerted on the vehicle body during the dip-and-drag-out process. These sensors allow users to quantify the forces, pressures, stresses, and torques acting on every component of the vehicle body, providing detailed insights into the structural performance during the process.

Video 6: The evolution of the normalized cumulative maximum pressure values acting on the vehicle body.

Calculating the fluid drainage time

Using a volume sensor allows the user to easily calculate the fluid drainage time. This is the time it takes the vehicle body to be entirely drained (if at all).
Users can analyze the evolution of the fluid volume within the entire vehicle body over time.

Figure 2: The evolution of the fluid volume in the vehicle over time.

Detection and Export of Fluid Puddles

Typically, when the Body-In-White is dragged out of the liquid container, some liquid remains in the compartment and will most likely never be drained. This is very common in the industry for initial design variants.

Usually, engineers are more often interested in larger liquid puddles, which can lead to cross-contamination in the subsequent steps of the e-coating process. With the help of PreonLab’s Python API, known as PreonPy, it is possible to detect fluid puddles automatically. Moreover, the leftover fluid puddles can be meshed using PreonLab’s built-in mesher, called the Preon Mesher. The meshes can then be exported fully or partially as CAD files. These can then be imported into other software for simulation, design, or analysis purposes.

Video 7: The left-over fluid puddles in the vehicle body.

Conclusion

LEVERAGE RAPID SIMULATION CAPABILITIES TO OPTIMIZE THE DIP-AND-DRAG-OUT TRAJECTORY

PreonLab offers unique features that greatly facilitate e-coating process chain design and assist engineers in identifying flaws in the process chain architecture before it is even constructed. Owing to PreonLab’s ease of use and the elimination of the requirement to generate a computational mesh, the user can quickly set up an e-coating simulation.With the help of CPS, proximity refinement, and powerful solver algorithms, PreonLab is able to accurately predict fluid behavior in the regions of interest efficiently. Furthermore, with built-in sensors, it is easy to predict drainage times, visualize forces on the vehicle, and evaluate design proposals. Moreover, with the built-in Python API (PreonPy), it is possible to enable target-specific and complex post-processing strategies to extract the most insight out of the simulation.

Want to learn more?

Check out the full article written by Max Flamm and Saba Golshaahi Sumesaraayi for more details here.

For more information on how PreonLab can help tackle your simulation challenges, get in touch with us here.

References

[1] G-L. Song, A dipping E-coating for Mg alloys, Progress in Organic Coatings,
Volume 70, Issue 4, 2011, pp. 252-258, doi.org/10.1016/j.porgcoat.2010.09.028