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RecurDynRecurDyn　　Technical Case Study in JapanTechnical Case Study in Japan

Takashi SuzukiKubota Solid Technology Corporation

Tokyo, Japan

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ThemesCoin MotionString MotionZoom MechanismDisk RotationFlexible rod with ContactBall bearingMore Challenges

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Coin Motion(1)Surface To Surface contact between coin edge surface and tube inner surface

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Coin Motion(2)A coin is standing by tube rotation while it’s being carried inside a tubeThis mechanism is used to contain coins compactly in a vending machine.

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String Motion(1)String is modeled by discretizationAs the first trial, segments are connected by BEAM. But, it’s not good for a soft string.If a reasonable value is used for longitudinal stiffness, its bending stiffness becomes too large.BEAM approach may be useful for a stiff steel wire cable simulation　

BEAM

BEAM

BEAM

BEAM

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String Motion(2)BUSHING is used to connect segments instead of BEAMBEAM is useful because the longitudinal , bending, and torsional stiffness can be defined independently.

+ +BUSHING BUSHING

Longitudinal : StiffBending : SoftTorsional : Moderate

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String Motion(3)Verification of String Model

F＝1

2*LT

U

L＝500mm

T=1N =1.0e6　gmm/s^2

U=1g/50mm=0.02 g/mm

T=10 N T=10 N

U=5g/50mm

T=1 N

7Hz 23Hz 10Hz

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String Motion(4)Contact ModelSphere is added on each segment and is used for contact

+ +BUSHING BUSHING

+ =

Segment

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String Motion(5)New possibility in v.4.1

“String guide” by SphereToTorus Contact

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Zoom Mechanism(1)Zoom Mechanism in Camera includes complicated contacts between parts.RecurDyn v.4.1 contact function is useful to simulate a zoom mechanism.We have already succeeded to simulate a simple zoom mechanism using a real CAD data of a camera company.I am sorry I am not allowed from the camera company to show it to you, but I explain how we did it.It’s not easy to simulate a complex zoom mechanism, but this success proves its possibility.

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Zoom Mechanism(2)Components in Zoom mechanism

Cam body

Zoom body

Frame body

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Zoom Mechanism(3)Geometry is from SolidWorksAssembly is imported into RecurDyn by a Parasolid fileMove the bodies into each LayerIt becomes easier to handle bodies with complex geometryChange color of each bodyJoint definition

Frame body is fixed to ground by Fixed jointCam body is connected to Frame body by RevoluteZoom body is connected to Frame body by Translational

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Zoom Mechanism(4)Switch to Body-edit mode of the Cam bodyCreate a contact surface from multiple faces of solid

This step is very useful to simplify contact definition

4 faces 1 surface

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Zoom Mechanism(5)Simplified Contact pin

Center point can be defined by circular edge selection

Zoom Body

Contact pins

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Zoom Mechanism(6)Contact definition between Contact surface and Contact pin. SphereToSurface contact is used.Contact surface is unified by the former operation, so we can select contact surface easily.

1 surface

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Disk Rotation(1)Disk is modeled as a flexible body imported from FEA software.Shaft is slightly inclined because of mechanical gap and manufacturing error. This causes Shaft Rocking phenomenon.Rotating disk is trying to stay horizontal because of Gyro moment effect.

Rocking

Small Gap at Retainer of shaft

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Disk Rotation(2)

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Flexible rod with contact(1)Block moves on Flexible shaftIf obsolete technique is used, computational burden is high. Using the new contact function, such a model can be made and solved easily.

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Flexible rod with contact(2)Flexible rod is modeled by connecting rigid cylinder segments by BEAMBlock is modeled by Box and 2 spheres in it.SphereInCylinder contact is used to keep the block on the rod.

BEAM BEAM BEAM

BLOCK

SphereInCylinder contact

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Flexible rod with contact(3)Computational burden of new analytical contacts is very low. 160sec (1GHz machine)

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Ball BearingThe new contact function Sphere To Torus makes it easy to model a ball bearing.

Torus　A Torus　B

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More challenges – Not completed yet

Sheet Folding Machine

Ball Screw

This 2sec simulation on 1GHz machine takes only 45 min. although many contacts are included. Sphere In Torus 429 Sphere In Cylinder 117 Sphere To Sphere 39