Appunti di tutte le lezioni del corso Advanced Manufacturing Processes

INTRODUCTION:

Growth/productivity change in last 50 years:

• Big growth from new manufacturing revolutions:
• 1850 → steam engine (operative energy)
• 1900 → mass production model (Ford)
• 1970 → automation
• IV manufacturing revolution → advanced robots

Technology & software → productivity_↑

Opportunity New→ flexibility → reconfig

• Different forms of energy: Manual, mechanical, chemical (reactive)
• New and advanced materials (ceramic, carbon fiber...)
• New or different products → few parts, miniaturization, higher tolerance, easier assembly
• Reduce fixed time cost and timer very expensive better

Phenomenon reality → Model = description → Mathematical modeling → Physical modeling

• “black box” → empirical modeling

THERMAL MODEL

heat transfer = temperature difference

Fourier Law

conduction

j_x^qx = -K ∂T/∂x

K = thermal conductivity [W/m°C]

Newton Law

convection

q_c = h(T_s - T_∞) h = convection coeff [W/m²K]

assumptions

K constant; K=K(T) no

isotropic and homogeneous material (constant volume, temperature energy)

energy balance

thermodynamic law => E_in + E_p - E_out = E_s

equation in form of energy conservation

T(x,y,z,t) 3D problem of energy conservation

∂²T/∂x² + ∂²T/∂y² + ∂²T/∂t² = 1/α ∂T/∂t

x = thermal diffusivity [m²/s] = K/ρC_p

(T(x,t)) ∝ I eliminate heat flow ∝ II eliminate ∝ ∂T/∂t

ΔT(x,t) = I eliminate heat flow

ΔT(x,t) = II eliminate ∝ ∂T/∂t/(specific heat capacity) ∝ ∂T(x,y,z,t) - T₀₀(t) = -∂T/∂x

T(x,t) = T(x,t_g)

Initial heat source mean internal neutron speed

T_p = T_∞ constant

isotropic and homogeneous material ∂²x = ρ/α ∂x/∂t

same thermal and chemical property of material

No internal heat source

1D semi infinite geometry *0 x

pure conduction, no convection or radiation

T(x,0) T

To(x,t)

Boas heat flow p^o and rich t

T(x,t) = Y⁰√(x/√αt) ierfc {√(x/√αt) * f^-1}

ierfc = integral of normalized Gaussian function

erfc = complementary error function

ierfc = integral complementary error function

D = √(αt)1/√π

Mutual distance between material affected by heat source

Laser Source

λCO₂ = 10600 nm

P = 1.7 - 6 KW

ηCO₂^~5 - 15%

Nd:YAG = 1064 nm

M²₃ = 2; pulse amp

P = 100 W

η = 3 - 8%; diode pumped

RPP cK²3: 3.0

M²₃ Nd:YAG = 1064 nm

P = 6 KW

R_Thz^~10

Yb-glass = 1040 or 1020 nm or 1064 nm M² Y

P = 6 KW R_Thz^~40%

λdisc = 940 nm

Pave = KW - P_max = 6 KW P_disc^~40%

λgas source = CO₂

He explained, energized and charged each carbon dioxide, easy to be excited, can relax and vibrate so reducing pairs excitation rates or energy level:

• E₀ equilibrium
• E₂ symmetric stretching mode
• E₃ bending mode
• E₄ asymmetric stretching mode

He = 45%: good heat conduction and so dispersion effect

N₂ = 45%: electric current can't excite directly, CO₂ so N₂ is excited and through collision excites CO₂ atom

CO₂ = 10%: active medium

M²₃ ηCO₂ = 10600 nm

M² Y₁ e

λCO₂ = 10600 nm

P = 1.7 - 6 KW

Semiconductor Source - Diode

• Top = ₃GAS ➞ compound engineered with vacuum (metal) of electrons
• Bottom = ARCAPS ➞ compound engineered with extra electron

N-P junction with mirrored surface

aluminium, gallium, arsenide

When current is applied, electrons extra and holes meet & junction release photon. This phase encourages release photon. Other holes and electrons coupling, diverge and release their own photon with same, phase, direction.

Influence of Energy

- Low thickness (t₁ < 10mm)

• High velocity ➔ low oxidation
• Low velocity ➔ more oxidation
• N₂ (O₂) and (H₂) (except)

- High pressure ➔ Reweld

t_l ➔ spread ➔ less fusion

I = AbsP . ds = dq(t₁ = 0) ➔ I = I

- Low density

Reactive Fusion Cutting

• High thickness (t₁)
• High velocity ➔ maximum
• Density ➔ cutting possibility
• O₂ N₂ + O₂ ➔ oxide

Only value above ➔ keep

If so, then we have an extra term

Thus by oxidation (exothermic reaction):

                   V ➔ ➔ oxidations (steady for reactivefusion cutting)

       Variation of surface &right; importantbecause surface receptive

       Equation I ➔ V because AbsP       ➔ Oxide layer and improve                           absorption

Melt Capacity Model

Freezing rateAbsP = ρ(cp(T_M - T₁) + L + V + (M)) = const

V        functional variables

Q ➔ thermal capacities/multiple uses

U ➔ easier heat of fusion

U = Easier heat of vaporization

I^i ➔ constant

If we have more power vectorone faster in higher power

HP

• No conduction
• No convection
• No radiation in beam
• Only W' variable

- TM = T_V - all fixed numbers

We can change the power with avery higher number

Comparison cutting with ω₂

On Earth, and materials that cannot melt (wood) or lower T_M, ➔ it is more used for metals — beam energy

HP

        radial off distance

If Φ ➔ reactive fusion cutting ➔ faster on surfaceIf Φ < S ➔ vaporization and melt and ➔ faster inside piece                                  compare abruption length to bite                                 distribute absorbance

We need on high gravity enough to maintain a constant distancebetween laser head and surface, because it loses more significantly even in flat

P_Abs = const      11 (ρc₂, ρLρo, .dsk) d Ψ = const

romeo (car stereotype) -> model estimate

leak initial position -> energy required to remove 1 electron from an atom

- xye thermal commitment (T) -> reference tempo of energy

leotinity -> tendency to react with work pigs (ex 0-vation)

ΔH -> Σoints atltright | Σ < 200 hooked for antonance atries, we must excite energy from qxiation, but plus excitation in chair

N2 estimate -> detect nuisance in leo enter pooring, for the sis

A. (air pal) -> mixed inquirial phase because cow ionization pointwise

H35 (mix A1-H35: F H height is escaption) -> t > 10mm deposit present because highly exploits

continued of as is

Pac makes qxidetions and attintions, HAZ has limited force on the workpiece

ABS split reomics, con ous oep wilowers, in ole contsertous

We don't hove ou height equiny new as fairs, because the voltage V is an identical measure op need-off dinnonia

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bull inflisio

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" скушman" и "anvator" motion

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regail indication depends on totic aitation

from workpiece, because enclosed halo a plumo airion

HAZ -> coupons oncal

bitrim of returns !