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UNIPD > Manufacturing Technologies > Flashcards

Manufacturing Technologies Flashcards

1
Q

Define UTS

A

Ultimate tensile strenght (maximum strenght)

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2
Q

Define true strain

A

dε = dl/l => έ = Ln(l/l°)

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3
Q

Définie engineering strain

A

e = Δl/lº
έ = Ln(1+e)

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4
Q

What hypothesis can be made about the volume of a deformed material?

A

It’s constant

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5
Q

What are the additivity specificities of the strain?

A

e1+ e2 ≠ e(tot)
ε1 + ε2 = ε(tot)

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6
Q

What are the two basics model for elastic and plastic strenght? In cold conditions

A

σ=Ε*σ (elastic behavior)
σ= Κε^n (plastic behavior) Holmon’s eq.

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7
Q

How to read the toughness on the σ/ε diagram?

A

It’s the area under the curve

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8
Q

In the Holmon equation, for metals, n is between ____ and ____

A

0.05 & 0.6 Øunit
0 -> rigid perfectly plastic
1 -> Elastic

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9
Q

In the Holmon equation, for metals, K is between ____ and ____ unit?

A

180 MPa (Al) - 2070 MPa (Co)

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10
Q

What is the effect of a temperature increase on the strain and the strenght?

A

A% increase,
σe and UTS decrease

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11
Q

Define the engineering and the true strain rate

A

ė = ν/l° engineering strain
dε/dt = ν/l

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12
Q

What is the basic model for the strenght in hot condition?

A

σ=C(dε/dt)^m
m: strain rate exponent coefficient (0.2-1.0)
C: strength coefficient (10-1000 MPa)

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13
Q

What are the name of the two phenomena (in tensile and compressive state)of shape changes?

A

Barreling
Necking

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14
Q

What are the specificities of the torsion test?

A

No friction
High level of strain
Strength gradient

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15
Q

What is the effect of the increase of the strain rate on the strength?
(No effect on strain)

A

UTS increase with the strain rate

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16
Q

What are the 3 eq. Of the generalized Hook’s law?

A

ε1 = 1/Ε [σ1 - ν(σ2+σ3)]

ε2 = 1/Ε [σ2 - ν(σ1+σ3)]

ε3 = 1/Ε [σ3 - ν(σ2+σ1)]

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17
Q

What are the generalized Mises-Levy flow rules?

A

dεi = dέ/σ [σj - 1/2(σj +σk)]

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18
Q

What is the tresca criteria?

A

It’s a value above the one we observe yielding.
In mohr circle Y=σmin-σmax
k= Y/2
Y: uniaxial yield stress of the material
k: shear yield strenght of the material

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19
Q

Define the VM criteria

A

Yielding the following equality is satisfied:
(σ1-σ2)^2 + (σ2-σ3)^2 + (σ1-σ3)^2 = 2Υ^2

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20
Q

What become the VM & tresca criteria under plan deformation?
ε2 = 0

A

σ2 = (σ1 + σ3)/2
σ1 - σ3 = 2/ vΓ(3) * Υ

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21
Q

How is calculated the deformation work?

A

u= Yf * e1
Where Yf is the average yield stress
or
u = K e1^(n+1)/(n+1)

Work = u * volume

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22
Q

Efficiency of a deformation?

A

uideal/utotal
Extrusion 30%-60%
Rolling 75%-95%

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23
Q

What is the multiplicative factor between the projected area and the real contact area ?

A

4-5 order of magnitude lesser

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24
Q

Is the friction model of coulomb usable with any τ and σ? Remind the formula

A

σ = μ.τ
Only valuable for small τ and σ. After the tresca model is better.

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25
Q

What is the tresca friction model ?

A

τ = m.k
m = τi/k

k: shear yield stress of the softer material
τi: shear strenght

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26
Q

Is the coef of friction μ increasing or decreasing with the temperature? Why?

A

It increase a lot (0.05 -> 0.2)
Because of the oxides broken
The higher chemical attractively
The elastic limit less high

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27
Q

What the Archard wear law describes?

A

It estime the amount of material removed by wear from a surface

V = k.L.W/(3p)

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28
Q

What are the different forms of lubrication?

A

Thick film
Liquid
Mixed

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29
Q

What are the function of the lubricant ?

A

Reduce friction
Reduce tool wear
Thermal barrier

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30
Q

What are the characteristics of the lubricant?

A

Easiness to apply
Non-toxic and non-inflammable
Odorless
Non-reactive
Adaptable to different process conditions

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31
Q

How is selected a lubricant?

A

In function of:
• The process
• Compatibility with the WP/tool
• Preparation of the surface
• Methods to apply it and remove it
• Treatment of exhausted lubricant
• storage and conservation
• environmental and biological hazards

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32
Q

What’s the tolerance on forging process?

A

0,5% to 1%

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33
Q

What are the advantages of the forging process (comparing to casting)

A

Metal flow and grain structure can be controlled
– Results in good strength and toughness
– Near net shape
– Design reasonably complex
* Landing gear
* Connecting rods
* Complex shafts

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34
Q

What are the disadvantage of the forging process (comparing to casting)

A

– Dies are expensive, particularly for hot forging
– Highly skilled labor required

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35
Q

What is the main problem of the open die forging?

A

Barreling

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36
Q

Describe the repartition of the stress in open die forging (plain strain)

A

pav = Yf’ (1+μa/h)

Maximal at the center:
exp(2μa/h)
a: rayon
h: height of the billet

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37
Q

What is called fullfering?

A

moves material away from center

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38
Q

What is called Edging?

A

moves material away from edges

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39
Q

What is called flashing?

A

Part of the matter outside the functional zone c(exceed of matter)

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40
Q

How is defined forgeability

A

It’s the capability of a metal to undergo deformation
without cracking

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41
Q

What test can be carried out to measure the forgeability?

A

upset test (compressive test)
hot torsion test (nb of twist before break)

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42
Q

What are the main defect of forging?

A
  • Surface cracks (forgeability limits)
  • Buckling
  • Laps
  • Internal cracks
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43
Q

What is the name of the process used to make coin?
What are its characteristics

A

coining, high pressure, die’s cavities totally closed

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44
Q

What’s is called heading?

A

Forging the end of a tip (bolt, screws)

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45
Q

What is piercing?

A

Punch inside a closed die to make a cavity

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46
Q

What is the name of the process:
* Uses rolls to shape parts
(ball bearings)
* Similar to shape rolling
but makes discrete parts
* Makes axis-symetrical parts

A

Rolling

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47
Q

What is called orbital forging?

A
  • Forms the part incrementally
    – Small forging forces
    because the die contact is
    concentrated on a small part
    of the workpiece at anyone
    time
    – Applicable to mostly
    cylindrical shapes
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48
Q

What is Isothermal forging?

A

– Dies at same
temperature of workpiece
– No workpiece cooling
– Low flow stresses
– Better material flow
– More close tolerances
and finer details can be
achieved

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49
Q

What is called cogging?

A

– Cylindrical parts subjected to radial impact forces by reciprocating dies
– Used to reduce tube diameter and introduce rifling into gun barrels

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50
Q

What are the 4 differnts types of press and their advantages?

A
  • Hydrolic press (Limited load)
  • Mechanical press (energy limited)
  • Screw press (energy limited)
  • Hamer press (energy limited)
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51
Q

what are the variable for hot rolling process?

A

Depedent variables :

  • Roll speed
  • Draft (amount of thickness reduction) or roll gap
  • Billet thickness
  • Billet width
  • Billet material
  • Billet temperature
  • Lubricant

indepedent variables :

  • Roll force
  • Power
  • Speed of exiting strip
  • Final strip temperature
  • Maximum draft
  • Roll strip contact length
  • Sheet or plate shape
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52
Q

What are the advantages and disadvantages of Hot rolling process (quote 3 of each)

A

6
Hot rolling
Advantages
– Stresses lower
– Forces smaller
– Power requirements less
– No work hardening
– Large deformations possible
– Breaks up the cast structure into preferable forms
– Closes porosity
– Sometimes the only way to create sheet
Disadvantages
– Higher friction
– Rolls need to be cooled
– Material handling difficult
– Personnel must be protected from heat

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53
Q

What are the advantages and disadvantages of cold rolling process (quote 2 of each)

A

Advantages
– Deformations of ~ 50 to 80%
– Work hardening increases strength
– Excellent surface finish
– Excellent tolerances on thickness and shape
Disadvantages
– High forces
– Small reductions give rise to surface stresses and non-
uniform stress distributions

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54
Q

What is called neutral

A

Point in the arc of
contact where the roll
velocity and the strip
velocity are the same

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55
Q

How looks like the stress distribution in hot rolling along the roling direction?

A

As an idian tepee,
More the friction coef is high, more the stress is high and centered.
The less the friction, the closer of the output is the maximium.

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56
Q

What can be done to reduce the force needed for rolling?

A

Back/forward tension

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57
Q

What is the general friction coeff. for hot rolling?

A

Between 0,2 and 0,7

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58
Q

What are the effect of a two high rolling force? What are the solution to prevent it?

A

The rollers bend and flattern.
We can reduce the bending by adding back-up rollers

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59
Q

What can we control on the final product by using hot rolling?

A
  • Thickness
    – Roll gap which impacts roll force and hence the dimensions
    of the mill frame
  • Width (due to spreading of slab)
    – Edge rollers (push material back)
    – Edge shears (cut material off)
  • Length
    – End shears
  • Mechanical Properties
    – Controlled by the microstructures which is controlled by the
    rolling parameters
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60
Q

What is called Sendzimir rolling mill?

A

A lot of back-up roller on hot rolling (pyramde 3-based+driving wheels)

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61
Q

What can be produced using shape rolling?

A

– I-Beams
– H-sections
– Rails (trains)
– Angle iron

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62
Q

How is called the process permiting to forge thorical axis-symetrical parts?

A

Ring rolling

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63
Q

What is Thread rolling?

A

It’s a process involving flat dies, moving parrally to their surface. Threads can be forged at high speed with high mechanical resistance.

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64
Q

What is called process Mannesmann?

A

A process for tubes-making using a defect (cavity) in the center of bar. The defect is opened by using a mandrel.

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65
Q

What is called trimming?

A

Removal of the flashing

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66
Q

What is called extrusion process?

A

2D geometry extruded:

  • Push an ingot through an orifice
    with the desired shape
  • Both hot and cold extrusion are
    possible
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67
Q

What are the different type of extrusion?

A
  • Direct
  • Indirect
  • Impact (mix btw indirect + forging)
  • Hydrostatic
  • Lateral extrusion
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68
Q

What are the mains parameters of direct extrusion process?

A

The die angle, reduction in cross-section, extrusion speed,
billet temperature, and lubrication all affect the extrusion pressure

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69
Q

What are the components of the force needed to carry out direct extrusion process?

A

Friction
Plastic deformation
their is an optimum die angle

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70
Q

What are the advantages of cold extrusion?

A

– Improved mechanical properties
– Work hardening
– Good control of tolerances
– Improved surface finish
– Elimination of heating costs
– High production rates

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71
Q

Describe the cold extrusion process

A

Two punch in front of each other in a closed matrix

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72
Q

What are the advantages of the hot extrusion?

A

Lower stress
Only way for certain materials.

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73
Q

To what are due the cracks in extrusion process?

A

high speed
high friction
high temperature

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74
Q

What is called chevron
defect?

A

It’s a cavity in extrusion process at the center of the part. it’s due to the material flow.

75
Q

What is called drawing process?

A

Like extrusion but material pulled out the orifice.
Used to make rod & wires

76
Q

what is called the “land” on extrusion and drawing process?

A

The zone of contact btw the WP and the die where the WP move parrallely to the die.

77
Q

What is the main limitation of the drawing process?

A

We can reduce the size of max 63% by pass => need multiple pass.

78
Q

In drawing process, what are the effect of the back tension on the stress in the WP and in the die?

A

It increasethe stress in the WP but reduce the stress in the die

79
Q

What material is used to make the die of drawing process?

A

WC

80
Q

What are the 3 basics processes of sheet forming?

A

Cutting
forming (bending, deep drawing, stretching)
finishing

81
Q

What is called Lueders bands?

A

Name of the parallele bands inclined in tensile state.

82
Q

What is “normal anysotropy”?

A

It’s a difference of A% in two direction of a plane.

83
Q

What is called bending process and what are its advantages/disadvantages?

A

Bending of a sheet
—
Advantages

– Easy to perform
– Simple, low cost tooling
– Fairly precise

—
Disadvantages
– Limited in the shapes it can produce
– Spring back difficult to estimate
– Some materials difficult to bend without tearing or
necking

84
Q

What is called MBR in bending process?

A

Minimum Bend Radius (MBR) is defined to
occur when a crack appears at the outer fibers

85
Q

What are the hypothesis made to calcul the MBR?

A

Hypotheses: the material is
homogeneous and isotropic;
the sheet is bent in a state
of plane stress

The strenght on the outer skin is equal to the elastic limit of the material.

86
Q

How is exprimed the MBR?

A

In function of the thickness of the material, (0,5T, 2T, …, 6T)

87
Q

How bendability of a material can be increased?

A

It can be increased through heating or by application of
hydrostatic pressure

88
Q

what are the variables influent on the MBR?

A

Edge condition of sheet
* Rough edges decrease bendability
– Amount and shape of inclusions
– Amount of cold work on edges due to shearing
– Anisotropy
– Elastic modulus - the springback phenomenon

89
Q

What is called springback?

A

It is caused by the elastic behavior of workpiece
material – elastic recovery

90
Q

How is called the springback factor?

A

Ks
Ks=1 no springback
Ks=0 complete elastic recovry

91
Q

How is compensed the springback effect?

A

– Overbending
– Applying compressive stresses to the bend zone
– Stretch bending/forming
– Raising temperature

92
Q

How can we prevent the collapse of the tube on itself during bending process?

A

By using a mandrel inside, sand or other to counteract the pressure.

93
Q

What is called stretching of a sheet?

A
  • The sheet metal is clamped around its edges and
    stretched over a die or form block, which moves upward,
    downward, or sideways
  • The shape is developed entirely at the expense of the
    sheet thickness
94
Q

What is called deep drawing process?

A

[Cans process]

– Place a round blank over the die
– Clamp in place by means of the blankholder
– Punch travels downward into die
* metal deforms by stretching into the die

95
Q

What are the main disadvantages of the deep drawing process?

A

– Limited shapes
– Material quality critical to obtain high-quality parts
– Dies are expensive

96
Q

Quote some of the main variables of deep drawing process

A

Blankholder force
– Too high - workpiece tears
– Too low - cup gets wrinkles
* Radius/diameter of the punch
* Diameter of the blank
* Thickness of the blank
* Clearance between the punch and die
– Clearances usually 1.07 to 1.14 thickness
– Too low - blank pierced
* Friction/lubrication
* Radius of entry into the die
* Radius on end of the punch
– too small - cracking at corners
– too large - wrinkling
* Punch force (dependent variable)

97
Q

What are the stress state under the blankholder and in the wall in deep drawing process?

A

Under the blankholder:

  • Compressive through the thickness
  • Tensile along the radius
  • Compressive along the circumference due to decreasing blank circumference

In the die:

  • Mostly tensile in the punch direction
  • Also tensile at right angles to the punch
    direction because of the cup contraction
    under tensile stresses in the cup wall
  • Stresses cause material to thin in
    punch direction and shrink around the
    die in the circumferential direction
98
Q

How is define drawability?

A

By the Limiting Drawing Ratio (LDR)

  • In an ordinary deep-drawing process, failure
    occurs by thinning in the cup wall under high longitudinal tensile stresses
  • When LDR is reached, the draw force just exceeds the force that the cup wall can support
99
Q

What is called earing?

A

It’s a defect occuring in deep drawing process when the sheet is not anysotropic. => wavy top of the walls.

100
Q

How is measured the sheet formability?

A

Tensile test:
total elongation at fracture, strain hardening
exponent, the planar and the normal anisotropy
—
Cupping test:
Erichsen and Olson tests (stretching) and
Swift and Fukui tests (drawing); to measure the capability of
the material to be stretched before fracturing
—
Bulge test:
a circular blank is clamped at its periphery and is
bulged by hydraulic pressure; to obtain effective stress-
effective strain curves for biaxial loading under frictionless
conditions

101
Q

What is the Erichsen test?

A

spherical punch pass through a sheet clamped by blankholders.

102
Q

What’s the swift test?

A

Determine the LDR (Dmax/d)
Cylindric punch goes deeper a possible.

103
Q

What is called Nakajima test?

A

Spherical punch hit the more or less width sheet.
From simple tensile to biaxial tensile.

104
Q

Describe the Forming limit diagram (FLD).

A

On the left side: Compressive stress state.
On the right side: Tensile stress state.

y-axis: major strain

A curve decreasing until the plane strain and then increasing.

105
Q

How to plot the FLD?

A

The swift test give a point on the compressive curve.

The nakajima test give the maximal strain in tensile state.

The plane strain point.

106
Q

Where is the safe zone on the FLD?

A

Between the two virtual lines passing by 0,0 and nakajima ppoint on a side and swift test by the other.

107
Q

Quote X other sheet process?

A

Hydroforming
Spining
Incremental sheet forming
Super elastic forming
Pen forming
Hot stamping

108
Q

What is called rake angle?

A

In chips formation process, the rake angle is the angle btw the tool face and the perpendicular to the machined surface.

109
Q

What is called the shear angle?

A

In chips formation mechanism, It’s the angle btw the machined surface and the shear plan (plan of dislocation)

110
Q

What is called clearence angle of a cutting tool?

A

It’s the angle between the flank of the tool and the machined surface.

111
Q

What are the hypothesis of the orthogonal cutting condition?

A
  • Process adequately represented by two-dimensional geometry
  • Tool is perfectly sharp
  • Tool only contacts workpiece on its front (rake) face
  • Primary deformation occurs in a very thin zone adjacent to the
    shear plane
  • Cutting edge is perpendicular to cutting direction
  • The chip does not flow to the side
112
Q

What is called BUE?

A

The built-up edge, it’s a accumulation of matter btw the tool and the WP.

113
Q

How to reduce the size of the BUE?

A
  • decrease the depth of cut
  • increase the rake angle
  • use a tool with a small tip radius
  • use an effective cutting fluid
  • Increase the cutting speed
114
Q

What are the different sort of chipsin orthognal cutting?

A

Segmented chips:
* Zones characterised by low and high shear strain
* Metals with low thermal conductivity and strength that
decreases sharply with temperature (like titanium)
—
Discontinuous chips:
* Brittle materials
* Materials containing hard inclusions and impurities
* When the cutting speed is too high or too low
* When the depth of cut is very large
* Without a proper cutting fluid
* When the machine is not sufficiently stiff

115
Q

What are the two componement of the force exerced by the tool on the WP? In the tool

A

Ft: Thrust force (perp. to machined surface)
—
Fc: Cutting force (// to machined surface)

116
Q

How is discomposed the force inside of the WP in orthogonal cutting?

A

Fs: Shearplan- //
Fn: Shearplan- I

117
Q

How is called the circle where all the forces in chip mechanism can be drawn?
(Force circle diagram)

A

Merchant’s circle

118
Q

The friction in milling operation lead to imortant increase of temperature. What are the main effects?

A
  • Cause dimensional changes in the workpiece
  • Induce thermal damage in the machine surface
  • Affect strength, hardness and wear resistance of the cutting tool
  • Eventually distort the machine tool itself
    Dull tools also generate heat through rubbing of the workpiece surface
119
Q

What are the parameters influents on the temperature of the WP?

A

Average chip-tool interface temperature rise
(ΔT) is a function of:

  • specific cutting energy (u)
  • cutting speed (V)
  • depth of cut (t0 )
  • workpiece thermal conductivity (k)
  • workpiece density (ρ)
  • workpiece specific heat (c)
120
Q

Where is the hotspot on the cutting tool?

A

On the tool face

121
Q

What is the difference between blanking and punching? (cutting process)

A

Punching: remove matter inside a sheet.
Blanking: remove the border arround

121
Q

What is the difference between blanking and punching? (cutting process)

A

Punching: remove matter inside a sheet.
Blanking: remove the border arround

122
Q

what are the different design of the punch in cutting operation?

A

Bevel (guillotine)
Double bevel
convex shear

123
Q

What are the different influent factors in cutting operation?

A
  • Punch and Die
    – Shape
    – Material
  • Clearance between punch and die
    – Increased clearance
  • Workpiece ductility and thickness
    – Increased ductility
    – Decreased thickness
  • Dulled tools
  • Speed of punch/shear
    – Decreased speed
  • Increased Lubrication
124
Q

One what depend the size of the clearence in cutting process?

A
  • Workpiece material
  • Thickness
  • Size of hole
  • Proximity of hole to sheet edge
    – Small holes required larger clearances
    than large holes
    – Typically range form 2-10% of sheet
    thickness
    – Can range from 1%(Fine Blanking) to 30%
125
Q

What is called Fine blanking?

A

a lower pressure cushion follow the movement (back pushing) and avoid the bending of the sheet.

The crack is much more shiny.

126
Q

What is called tool wear?

A

Matter removed from the tool on flank and rake(tool) face

127
Q

How is characterized the wear?

A

Taylor’s equation express the life time of the tool in function of the matter and the cutting speed.

128
Q

What cause the wear crater?

A

*Chemical affinity
*High temperature (=friction)

129
Q

What is called tool chipping?

A

Breaking away of a piece from the cutting edge of the tool. It’s caused by mechanical shock or thermal fatigue.

130
Q

what are the different way to estimate the usure of a tool?

A

Direct method (look, measure)

Indirect method (transducer, accoustic emmision)

131
Q

what is called surface finish

A

geometric features of the surface

132
Q

what is called surface integrity?

A

Pertains to properties as fatigue life and corrosion resistance

133
Q

What is the feed?

A

The depth of the WP eaten by the tool by revolution unit.

134
Q

Define feed rate

A

speed at which the tool travels along the
feed direction [mm/min]

135
Q

What is the depth of cut in turning operation?

A

The depth the tool remove direction perpendicular to the axis.

136
Q

What are the parameters defining the machinability?

A
  • Force and power requirements
  • Tool life obtained
  • Surface finish and integrity of the machined part
  • Chip control
137
Q

How is called the removable cutting part of the tool?

A

Insert

138
Q

What are the different materials used for making cutting tools?

A

Carbon tool steels
High speed steels
Cast alloys
Carbides
Ceramics

139
Q

What are the function of the cutting fluid?

A

Reduce friction
Cooling
Wash chips away
prevent corrosion
Reduce force energy consumtion

140
Q

How to reduce vibration in milling process?

A

Stiffer machine
Tuned dumper
active control
Support WP rigidly
Increase cutting speed
Minimize cutter overhang
Modify tool geometry
change process parameters(speed,feed,lubricant, depth of cut)

141
Q

What is called MRR

A

Material removal rate: Volume of material machined in
the time unit [mm 3 /min]

142
Q

What is the difference between climb milling and conventionnal milling?

A

In climb milling, the tooth goes perpendiculary in the matter while in conventionnal milling, the tooth goes // to the matter.

143
Q

What is the advantage of climb milling?

A

Less vibration (if the installation is very stiff)

144
Q

When the grinding process is used?

A

Too hard materials,
Too high accuracy asked

145
Q

What are the superabrasive materials?

A

cubic boron nitride,
Diamond

146
Q

what are the conventionnal abrasive

A

Silicon carbide
Alumine

147
Q

What are the different type of ligent used in the griniding wheels?

A

Vitrified
Resinoïd
Rubber
Metal bond

148
Q

What is measured by the wheel grade?

A

the bond’s strength and thus measure of the hardness of a bonded abrasive (from A-soft to Z-hard)

149
Q

What is measured by the “structure wheels factor”

A

The porosity of the bonded abrasive (1-dense to 16-open)

150
Q

What is the specificity of the rake angle in grinding?

A

The average rake angle of the grains is highly negative: consequently the shear
angle is very low and the shear strain can become very large

151
Q

Why the specific energy is so high in grinding?

A

Size effect:
The smaller the grinding chips, the higher the strenght extremely high density of dislocation in the shear
—
Wear flat:
The size of the wear flat is much larger than the grinding chips
—
Chip morphology:
shear strins are very large,
Plowingconsume energy without contributing to chip formation.

152
Q

What are the effects of the increase of temperature at the surface of the worpiece in grinding?

A
  • Tempering
  • Burning
  • Residual stress
153
Q

What is called wear flat in grinding operation?

A

The contact zone btw the grain and the machined WP.
Also called usure plan.
This plan depends on the chemical affinity.

154
Q

What are the 3 main defect attributed to the grinding

A

Attritous wear
Grain fracture
Bond fracture

155
Q

What can be done when the grinding wheel is worn?

A

We can dress the surface again with a diamond tip.

156
Q

What can be done when the grinding wheel is used?

A

We can dress the surface again with a diamond tip.

157
Q

What is the difference between conventionnal and unconventionnal machining?

A

The unconventional machining use other sort of energy than the classical one.

158
Q

What are the 4 sort of energy used in unconventional machining?

A

Electrical
Chemical
Termal
Mechanical

159
Q

What is the chemical machining?

A

Chemical attacks metals and etch them by removing small amounts
of material from the surface using reagents or etchants

160
Q

How is called the hole formed under the mask in chemical machining?

A

Undercut

161
Q

When using the unconventionnal machining can be economicaly advantagous?

A
  • Hard, Strong alloys
  • Material to flexible
  • Complex geometries
  • Very high surface finish
  • Temperature raise or residual stress undesirables
162
Q

What are the advantages/disadvantages of the Ch. Machining?

A

Advantages:
Low capital cost once basic
equipment is installed
*Many work surfaces can be
“machined” simultaneously
*No cutting forces: no distortion or thermal stress problems
*Good for delicate parts
*No edge burring
—

Disadvantages:
Undercutting of masked areas represents a problem
*Sharp corners not possible
*Work piece material must be homogeneous
*Disposal of chemical etchant expensive
*Operators require special protection against possible chemical spillage

163
Q

What is chemical blanking?

A

A process similar to the chemical machining but to clean part. (electronic, decorative)

164
Q

What is the Electro chemical machining?

A

An electrode is the tool. The WP is inside electrolyte. The metal is remover by is own ionization. (5A to 40 000A)

165
Q

What is the die-sinking?

A

A kind of electro-chemical machining where the electrode scan a whole surface.

166
Q

What part is made by using electrochemical machining?

A

compressor blade: the part who link the turnig wheel.
The electrode can have any geometry.

167
Q

What are the advanages/disadvantage of the electrochemichal machining?

A

Advantages:
*Any hardness of material can be cut
*No physical contact with work piece so
no cutting or thermal stresses generated
making it good for delicate parts
*Long tool life
*No edge burrs
*Holes complete in one “pass”
—
Disadvantages:
*Work piece must be electrically
conductive
*Capital equipment expensive,
particularly the electrolyte pumping
and cleaning systems
*Form tooling cost can be high,
particularly where 360 degree cutting
is required

168
Q

What is the advantage of electromechancal grinding?

A

only a small part of the matter is removed because of the friction, less residual stress

169
Q

What is the other name of electroerosion?

A

Elecro discharge machining

170
Q

What is the principle of the EDM?

A

The WP is in dielectric fluid,
a localized spark between the electrode (tool) and the WP melt the metal

171
Q

What are the advantages/disadvantages of EDM?

A

Advantages:

*Material of any hardness can be cut
*High accuracy and good surface finish
are possible
*No cutting forces involved
*Intricate-shaped cavities can be cut with
modest tooling costs
*Holes completed in one “pass”
—
Disadvantages:

*Limited to electrically conductive
materials
*Slow process, particularly if good
surface finish and high accuracy are
required (2-400 mm3 /min)
*Dielectric vapor can be dangerous
*Heat Affected Zone (HAZ) near cutting
edges
*Die sinking tool life is limited

172
Q

What is the material generally used as electrode in EDM?

A

Classical EDM : Graphite
Wire EDM: Brass, Copper or tungstene alloys.

173
Q

What are the advantages/Disadvantages of the laser machining?

A

Advantages:

  • Virtually any material can be cut
  • 2D and 3D shapes can be cut
  • Holes having length/diameter ratio of
    up to 100:1 is possible
  • High speed cutting possible with thin
    material
  • No consumable tooling needed
  • Work area need not be under vacuum
    as required with EBM
    —
    Disadvantages:
  • Holes bigger than 1mm (1/32”) diameter
    difficult to drill
  • HAZ formed around cut surface edges
  • Reflective surfaces difficult to machine
174
Q

What are the advantages/disadvantages of the electron-beam machining?

A

Advantages:

*Any material can be cut
*No cutting forces are involved so no
stresses imposed on part
*Exceptional drilling speeds possible
with high position accuracy and form
*Extremely small kerf width when
profiling so little material is wasted
—
Disadvantages:

*Skilled labor is required
*A suitable backing material must be used
*Maximum thickness that can be cut about
10mm (3/8”)
*Drilling length/diameter ratio up to 15:1
*Work area must be under a vacuum
*Capital equipment cost is high

175
Q

what are the water jet advantage and disadvantages?

A

Advantages:

*Materials of any hardness can be cut;
even food
*Cutting can be in any direction
*3D cutting possible with CNC nozzle
control
*No deburring is required
*No thermal stresses in the work piece
Disadvantages:

*Limited nozzle life, particularly when
abrasive is used
*High capital cost of equipment
*Very noisy process because of
supersonic nozzle velocities

176
Q

What is the limit value of µ above the one we consider the friction as high?

A

0.3

177
Q

[Deep drawing] What happen if ΔR is lower than 0?

A

Occurrence of ears defect

178
Q

How can be measure the machinability in turning?

A

By comparing the speed of the tool in the material with the one of a reference material

179
Q

Define boring & internal grooving

A

milling of a pocket from a drilled hole.

180
Q

What is called facing?

A

In turning operation the tool move l to the axis.

181
Q

What is face grooving?

A

Milling the face in turning

182
Q

What is straight turning?

A

In turning operation the tool move // to the axis.

183
Q

What are the components of the grinding specific energy in grinding?

A

u = u(chip)+u(plowing)+u(sliding)

UNIPD (4 decks)

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