FRICTION RELATED EXPLICIT CALCULATIONS ON VENDING MACHINE SECTOR

Friction Related Explicit Calculations in the Vending Machine Sector

June 24-26, 2014 - Munich

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Matteo Adobati [email protected]

Fabio Rota [email protected]

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Contents

1. N&W Group

2. R&D Department

3. Scope

4. Tea infusion sliding piston

5. Sugar dispenser sliding system

6. Conclusion

1. N&W Group

10.000 customers

200.000 150.000

OCS and Horeca machines / year

Vending machines / year

500 suppliers Worldwide presence

To be the leading producer of coffee-based drink and snack & food dispensers world-wide, by delivering an unrivalled and consistent consumer experience.

Caring for our customers, our people and the environment are the keys to our success.

1.500 3 6 15 manufacturing sites world-wide branch offices european R&D centres employees

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4

Brands & product ranges

Vending O.C.S. Ho.Re.Ca.

1. N&W Group

550

Innovation, design, excellence

100 5%

• A consolidated project management approach • Structured working flows and procedures on both Product and

Innovation development processes • Product development supported by advanced virtual validation methods

in both Design and Lab test stages

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2. N&W R&D Department

Percentage of the turnover invested

in R&D Engineers in R&D

Registered patents

Friction issues

Project targets

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3. Scope

• Sliding [plastic/rubber] - [plastic/plastic] - [steel/plastic] • Changing geometries during movements • Dry/wet surface interaction • Presence of sweetening powder or moisture • Contact pressure • Heat transient condition

• Investigate the contact finding the right LAW • Friction coefficient charaterisation - static/dynamic • Testing campaign vs FEM results comparison • Mechanical solution optimization:

contact force/pressure decrease robust and reliable assembly

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4. Tea infusion sliding system

4.1 – Finite element model Tea-Brewer

Tea-leaves infusion mechatronic dispenser

N&

W p

ate

nt

regis

tere

d

Solvers: •Optistruct NLSTAT/NLGEOM (preliminary analysis)

•Radioss

3D & FEM model

Boundary conditions: • Infusion chamber:

1 DOF (z axis) • Piston: grounded fixed • Chamber movement:

IMPVEL (z axis)

Piston Rubber gasket

Infusione chamber

Elements: •Hexa8 (# 120000)

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4.2 – Contact surfaces

Infusion chamber - Rubber Gasket

Rubber Gasket - Sliding piston

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4.3 – Material & contact

• Material: Infusion Chamber - PEI (Polyetherimide) Rubber gasket - Sylicon rubber 60 Shore Piston - PEI (Polyetherimide)

• Material numerical formulation: PEI (Polyertheremide) - Elastic - LAW1 Sylicon rubber - Ogden - LAW42

• Type7 contact interfaces • Contact parameters environment:

Assembling rubber preload Wet (low friction) / Dry (worst case) Changing piston motion direction [down - up]

Sliding piston

Supplier rubber graph used to define the Ogden law parameters: E = 4.5 Mpa

1 = 0.948 Mpa

2 =-0.236 Mpa

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4.4 – Friction behaviour

Contact pressure (dry condition)

Piston positions:

UP: t_step: 0,5 s Phase: Plug + sliding down: Piston Force: Fmax = 2.5 N

DOWN: t_step: 4,5s Phase: Reverse direction: Piston Force: Fmax = 12 N

Transient cycles:

t = 0,0 0,5 s Piston plug

t = 0,5 4,4 s Sliding down

t = 4,4 4,6 s Reverse direction

t = 4,6 6,5 s Sliding up

Normal Tangential

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4.5 – Results & test compaign

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4.6 – Conclusion

• Explicit analysis able to predict the rubber behavior

• Good support to calibrate material blend

• Samples reduction vs final solution design

• Good contact response despite of relevant mechanical clearances presence

• Good understanding on dynamic mechanism performances friction’s influence

• Good driver to improved solutions

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5.1 – Finite element model Solvers: •Optistruct NLSTAT/NLGEOM (preliminary analysis)

•Radioss •Motionsolve

Boundary conditions: • Fork: 1 DOF (axis rotation) • Plate: grounded fixed • Fork rotation: IMPVEL • Cap spring: CLOAD

Elements: •Tetra10 (# 126000) •RBE2 (# 6)

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5.2 – Contact surfaces

Cap - slider

Slider - frame

Cap - frame

Slider - fork

Fork - plate

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5.3 – Material & Contact

- Material: POM (Polyoxymethylene)

- Material numerical formulation – Law1

- Type 7 contact interfaces

- Contact parameters environment:

> humidity / temperature

> sugar powder accumulation during lifecycle

> mechanical clearances

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5.3 – Friction behaviour

- Numerical – experimental data correlation

Fu

Cam rotation [°]

Sliding force [N]

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5.4 – Results

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5.5 – Conclusion

• Explicit simulation very close to real dynamic mechanism

• Predictive solutions to optimized configuration design

• Good contact response despite of relevant mechanical clearances presence

• Good understanding on dynamic mechanism performances friction’s influence

• New leverages’ design

• Friction environment new mechanism robustness

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Thank you for your attention!

Any questions?

www.nwglobalvending.com

FRICTION RELATED EXPLICIT CALCULATIONS ON VENDING MACHINE SECTOR

Engineering

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