Optimization of overlapping mesh calculations for...

STAR Global Conference, Vienna, March 17-19, 2014Madhusudhan Devanathan

Optimization of overlapping mesh calculations for simulation of paint shop

manufacturing processes

06.03.2014

Agenda

1. Simulation of Rodip© pretreatment/coating process

2. Simulation of adhesive smearing onhang-on parts

3. Simulation of automotive top coatspray booth

4. Conclusion

Source : Autoline.tv

Source Daimler AG

Source Daimler AG

© 2014 Duerr AG

Source Daimler AG

2MBtech Group GmbH & Co. KGaA Madhusudhan Devanathan

06.03.2014

Dipping of Body-In-White (BIW) in liquid tankRodip used in pretreatment / coating systems

Simulation Objective : Locate residual air pockets / liquid pondsPressure forces on hang-on partsOptimum computation time

Process time around 62s

BIW Meshing : Automated workflow in STAR-CCM+Presented in Star Global Conference 2012

Numerical model :Volume of fluid (VOF) to model air and liquid phaseHydrostatic boundary conditionsOverlapping grids and superposing motion model

Translational velocity in X and Z, rotation about YTime dependant volume sources

Case 1: Rodip© simulation

© 2014 Duerr AG

Source: Parker Engineering Co.,Ltd.

Rodip © motion in simulation3MBtech Group GmbH & Co. KGaA Madhusudhan Devanathan

06.03.2014

Local refinement of background meshVOF model : Refined air-liquid interface Overset Grid : Refined motion space

Precalculation to create time dependant volume sour cesMovement of overset boundary along path with RBMExport of overset boundary at certain frequencyWrapping exported surfaces within remesh time interval

Generation of background mesh with respective volu me sources

0 10 20 30 40 50

Simulation time

Case 1: Creation of time dependant volume sources

4

Mesh section

MBtech Group GmbH & Co. KGaA Madhusudhan Devanathan

06.03.2014

Case 1 : Analysing dip-in simulation results

Smooth flooding during dipping in180 deg rotation ensures movement of air bubblesAir pockets detected in rear floor regionOptimization of BIW construction

1

2

1 2

Location of trapped air

VOF field along midsection of carSource: Daimler AG


Air

Liquid

06.03.2014

Case 2 : Adhesive smearing during dip-in process

Smeared adhesive seen after dip-in process

Background of smearing phenomenaAdhesive is not cured before dippingNon-uniform filling of cavities of engine hoodUnbalanced pressure forces act on componentsRelative motion between components smear adhesive between them

Filling behavior during dip-in process

Source: Daimler AG

F

Air

Liquid

Source : Daimler AG

Source: Daimler AG6


06.03.2014

Mapping of forces from CFD to Structural MeshCells vertices of midplane

Additional conditions for mapping

Calculation of deformation in Abaqus

Case 2 : Calculating deformations from dipping forc es

FEmg F K U→ →

+ =

Map1F

2F1 2, FF

1 2FEF F F→ → →

= +

1 2

n N

FEF F F→ → → + =

∑ ∑

CFD mesh FE mesh

Visualizing and during dipping processFEF→

U→

* Deformation are scaled from original values

*

Source: Daimler AG

n: Number of CFD cells , N : Number of FE elements

K: Stiffness matrix, U : Deformation matrix


06.03.2014

P1

P2

P3

P4

P5

P6

P7

P8

P9

P1

P2

P3

P4

P5

P6

P7

P8

P9

Case 2: Optimizing design to maintain open contact

Initial design

Optimized design

Con

tact

ope

n in

[mm

]C

onta

ct o

pen

in [m

m]

Air

Liquid

4mm

Air

Liquid

8

- Additional Holes


06.03.2014

Case 3 : Simulation of Automotive top coat spray bo oth

22 25 3740

5 2 4 15 1 13

1 2 3

12 11 13 44116 2 46610 77

20 24173921 23

1215 11

Simulation objective :Determination of paint thickness on BIWEvaluation of robot programsOptimization of brush settingsPrediction of overspray

Process data requiredPosition of robots and their motion programsTimeline of robots Nozzle gun ON/OFF program Brush change program and settings

Spray booth layout and program timeline

Source Daimler AG


06.03.2014

Case3 : Physics of paint nozzle

Source : Eisenmannair inlet rotating bell paint inlet

Nozzle / Brush ParametersInlet air flow rate N1,N2 (L/min)Rotation rate (RPM)Paint volume flowrate PFR (ml/min)

Numerical modelCompressible airPrimary atomisation – Lagrangian particlesSecondary breakup modelParticle under influence of

Drag and pressure forcesGravitational forcesTwo way coupling

Primary atomisation

Source Daimler AG

Source Daimler AG


06.03.2014

Case 3 : Calibration of paint nozzle

Velocity (m/s)

Velocity (m/s)

150

0

75

75

0

37.5

3.69

0

1.05

Paint film (µm)

Simulation Vs ExperimentBrush A

N1=400, N2=200, RPM = 25000, PFR= 180

Brush B N1=400, N2=600, RPM =

25000 , PFR=240Brush A

Brush B

2.63

11Painting direction

A

Measuring line

Section A


06.03.2014

Robot motion : Describe movement of tool center point (TCP)Robot path : Description of over timeSTAR-CCM+ requires

First derivative of position :Starting position :

Setting robotic motion models and coordinate systemsRotation sequence :

Case 3 : Modeling robotic motion using overset grid s

[ ], , , , ,X Y Z α β γ

, , , , ,X Y Z α β γ• • • • • •

[ ]0 0 0 0 0 0, , , , ,X Y Z α β γ

( ) ( ) ( )x y zR R Rα β γ

1 2 3(XYZ) ( ) ( ) ( )X Y Z X Y Z X Y Zα β γ′ ′ ′ ′′ ′′ ′′ ′′′ ′′′ ′′′→ → →ɺ ɺ ɺ Overset mesh for nozzle

Swept volume of overset boundary

12

34

(4)

(0,1,2,3)

Source Daimler AG

12

200mm


06.03.2014

Case 3 : Programming nozzle ON/OFF and brush change s

Nozzle flow ON/OFF :Multiply flow inlet conditions by heavy side unit step function

Brush changes :One or all brush parameters changeJava script monitors all robots after everytime iterationOn brush change detection, trigger brush event

Brush change event:Change inlet velocity tableChange particle distribution tableChange wall rotation

Change particle flow rateImplementing dynamic brush change program

Source: Daimler AG


06.03.2014

Case 3 : Result of spray booth simulation

Source Daimler AG


06.03.2014

Conclusion

Complex multi-DOF motion in painting systems can be simulated using overset grid methods

Reduction of computational time was achieved by developing overset grids with time-dependant volume sources

Java based macros used to implement complex time dependant boundary conditions in STAR-CCM+

Automotive top coat simulation methodolgy developed to simulate the complex physical processes in an automotive top coat spray booth


06.03.2014

Acknowledgement

Mr.Lothar HaigisHead of structural analysis and computational fluid dynamicsMBtech Group GmbH & Co. KGaA, Germany

Mr.Jochen RathfelderInnovative Technische Berechnungen GmbH ,Germany


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