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Polimi 1st Sem > Computer Aided Manufacturing > Flashcards

Computer Aided Manufacturing Flashcards

1
Q

[Fundamentals of Machining] What are the Main objectives of Machining processes?

A

To remove material to Transform the Raw part into a desired geometry. These include Turning, Milling, Drilling, Grinding, etc.

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2
Q

[Fundamentals of Machining] Why are machining processes typically the last step in mechanical component production?

A

Because they provide good tolerances as well as good surface finish. Which makes them great to generate the final product.

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3
Q

[Fundamentals of Machining] What are the differences between orthogonal cutting and oblique cutting?

A

Orthogonal cutting is a simplified version of oblique cutting that allows a simpler description of the dynamics and kinematics of the process, as well as the chip formation.
Orthogonal cutting is when the cutting speed is orthogonal to the cutting edge of the machine.
Oblique cutting involves the tool being at an angle with respect to the cutting direction (chip formation becomes more complex)

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4
Q

[Fundamentals of Machining] What are the key kinematic and dynamic variables in orthogonal cutting?

A
  • vc = cutting speed
  • b = cutting width
  • hD = cutting thickness (chip thickness before cutting)
  • AD = chip transversal section before cutting
  • hch = chip thickness after cutting
  • r = Chip thickness ratio < 1
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5
Q

[Fundamentals of Machining] What is the role of the rake face, flank face, and cutting edge in a cutting tool?

A
  • Rank Face: Surface on which the chip flows.
  • Flank Face: Surface looking at the machined surface
  • Cutting edge: Intersection line between rake face and flank face.
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6
Q

[Fundamentals of Machining] What are the typical ranges for the Rake Angle, Clearance angle, and Solid angle in cutting tools?

A
  • Rake Angle 𝜸𝟎: angle between rake face and the normal to the cutting direction. -15Β° <= 𝜸𝟎 <= 30Β°
  • Clearance angle 𝜢𝟎: Angle between flank face and cutting direction. 2Β° <= 𝜢𝟎 <= 15Β°
  • Solid angle 𝜷𝟎: Between rake and flank faces.
  • π›ΌπŸŽ + π›½πŸŽ + π›ΎπŸŽ = 90Β°
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7
Q

[Fundamentals of Machining] How does the Mechanism of Chip Formation work during Machining?

A

The tool stresses the material. The material is plastically deformed until fracture, separating some material from the workpiece and transforming it into chip. The chip then flows on the tool and moves away from the machining zone. Large amount of heat is generated during this process.

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8
Q

[Fundamentals of Machining] What is the significance of the shear plane in chip formation?

A

The shear plane is the plane region where the material is deformed. In reality this plane is more of a zone.
Geometrically it is the plane generated between the top of surface of the chip and the bottom at the joint to the material, which is an angular plane (shear angle).

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9
Q

[Fundamentals of Machining] How does the tool’s motion cause the material to separate and form a chip?

A

The tool deforms the material until fracture, which is when the chip is formed (some material is separated from the workpiece)

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10
Q

[Fundamentals of Machining] What are the main types of chips produced in machining, and under what conditions are they formed?

A
  • Continuous Chip: Ideal chip, leaves a good finish on the workpiece.
  • Discontinuous chip: happens on brittle materials, leaves behind an irregular surface.
  • Serrated or Segmented chip: Semi-continuous chip with saw-tooth appearance. Happen when the material gets too soft due to high temperatures (due high cutting speed and the material type)
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11
Q

[Fundamentals of Machining] How does a chip-breaker help Manage chip Formation?

A

The chip-breaker is a small rounded groove on the upper part of the tool used for cutting. It helps guide the chip to exit the machining area.

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12
Q

[Fundamentals of Machining] What are the primary differences between the shear plane and the shear zone model?

A

The shear plane is more of an approximation of the shear zone. It is a representation of where the shear plane is located in order to make analysis more simple

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13
Q

[Fundamentals of Machining] What is the Importance of studying the Card Deck model of chip formation?

A

It makes it easier to visualize what is happening during the machining process. It basically implies visualizing the chip formation as material being sheared in successive layers, resembling a stack of cards sliding over one another

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14
Q

[Fundamentals of Machining] What does the velocity diagram in chip formation represent?

A

It shows the relationship between cutting velocity, chip velocity, and shear velocity. Helping understand the material flow during cutting.

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15
Q

[Fundamentals of Machining] How does the cutting tool’s geometry influence chip formation?

A

The tool’s geometry including rake angle, clearance angle, and nose radius, affects the flow of the material being cut.
Large rake angle reduces cutting forces and chip deformation, smaller clearance angle ensures proper contact with the workpiece, the tool’s radius influences the surface finish and chip continuity.

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16
Q

[Fundamentals of Machining] What are the key parameters that affect the forces acting on the tool during machining?

A

Cutting speed, feed rate, depth of cut, rake angle, workpiece material properties, and lubrication.

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17
Q

[Fundamentals of Machining] What are the cutting force and thrust force, how are they related to the cutting speed?

A
  • Cutting Force (Fc) acts parallel to the cutting speed and is responsible for shearing the material.
  • Thrust Force (FD) acts perpendicular to the cutting force, providing stability to the tool.
  • Both of these add up to be the Total Force in orthogonal cutting.
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18
Q

[Fundamentals of Machining] How does material removal rate relate to machining efficiency?

A

MRR measures the volume of material removed per unit of time. Higher MRR indicates greater machining efficiency, but we shouldn’t compromise tool-life, surface finish, or part accuracy.

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19
Q

[Fundamentals of Machining] What factors affect the cutting pressure during machining?

A

Depth of cut, Workpiece Material, Tool material and geometry (particularly its rake angle), cutting speed, and lubrication conditions. And the uncut chip thickness

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20
Q

[Fundamentals of Machining] How does the Kronenberg relationship describe the relationship between cutting pressure and chip thickness?

A

kc = kcs/hDx
where:
- kcs is the specific cutting pressure related to the workpiece material
- x is a constant related to the tool material.
- hD is the uncut chip thickness.

It shows that the cutting pressure decreases as the uncut chip thickness increases. Thinner chips require more energy per unit volume for removal.

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21
Q

[Fundamentals of Machining] What is the role of cutting energy in machining, what factors contribute to it?

A

Cutting Energy represents the Work done to remove material and is critical for understanding power requirements and tool performance.
It depends on cutting force, cutting speed, material removal rate, and tool-material interaction.
Ec = kc*V = Fc * Lc

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22
Q

[Fundamentals of Machining] How does cutting time depend on the length of the cut and the cutting speed?

A

tc = Lc/vc = V / MRR

V is the removed material volume

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23
Q

[Turning] What are the basic principles of Turning?

A

This operation uses a single-point cutting tool to remove material from a rotating workpiece.

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24
Q

[Turning] What tools and machine tools are used in turning?

A

Single-point cutting tools and inserts. Machines primarily are lathes, including CNC lathes.

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25
Q

[Turning] How do you define appropriate process parameters for turning?

A

Parameters include: Rotational Speed, Feed Rate, Depth of Cut, and Cutting Speed. Depend on the material, surface finish, and dimensional tolerances.

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26
Q

[Turning] What are some of the different types of turning operations?

A

Straight turning, taper turning, profiling, contour turning, facing, grooving, threading, drilling, boring, and cutting-off

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27
Q

[Turning] How is profiling or contour turning different from straight turning?

A

Profiling creates complex, curved surfaces, while straight turning only produces cylindrical shapes with uniform diameters.

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28
Q

[Turning] In what scenarios is grooving used?

A

It creates narrow recessed features, such as o-ring slots in the workpiece

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29
Q

[Turning] What are the key parameters that affect the turning process?

A

Machined Diameter (D), feed rate (f), depth of cut (ap), chip thickness (hD), rotational speed (n), and cutting speed (vc)

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30
Q

[Turning]What are the applications of Facing and Cutting-Off operations?

A

Facing creates a flat surface at the end of the workpiece, while cutting-off separates a part of the workpiece.

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31
Q

[Turning] How do you determine if a part is machinable by turning operations?

A

A part is machinable by turning if it is rotationally symmetric and the required features can be achieved using a turning process.

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32
Q

[Turning] How do feed per revolution and depth of cut influence the turning process?

A

Higher feed rates increase material removal but may degrade surface finish. Greater depth of cut removes more material but increases cutting forces and therefore tool wear.

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33
Q

[Turning] What is the significance of chip section and rotational speed in turning?

A

The chip section determines the volume of material removed, while rotational speed directly affects the cutting speed, and, therefore, the MRR and heat generation.

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34
Q

[Turning] What are the principal components of a Lathe?

A
  • Headstock: The main component, where the spindle is, and where the workpiece is clamped to.
  • Tailstock: The assembly with the same center as the Headstock. Normally used for drilling, or a dead center point.
  • Carriage: The movable assembly where the tool is clamped to.
  • Bed: The base of the machine which can be clamped to the ground
  • Spindle: The rotating component inside the Headstock.
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35
Q

[Turning] What are the different types of work-holding devices used in turning?

A
  • Three-jaw chuck: Most common. Holds the piece with 3 jaws that clamp the workpiece inward (toward the center of the spindle)
  • Collet: Usually for smaller diameter workpieces. (Similar to the drillbit-holder of a drill).
  • Mandrel:Usually for hollow pieces. The mandrel is inserted into the β€œtube”. It’s normally mounted between centers on the lathe.
  • Faceplate: A thin plate mounted on the spindle that helps clamping irregular material. (Kind of like a peg board)
  • Steady/follower rest: It’s used to hold very long pieces. It’s placed in the middle (lengthwise) of the workpiece to prevent deflection.
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36
Q

[Turning] What are the main components of a single-point cutting tool?

A
  • Shank: mounts the tool.
  • Cutting head: performs the cutting.
  • Optional Inserts: replaceable cutting edges.
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37
Q

[Turning] What are the advantages of using inserts in cutting tools?

A

They are replaceable, reducing tool costs. They are available in various materials and geometries to suit different applications, improving tool-life and performance.

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38
Q

[Turning] How do the rake angle and Clearance angle influence the cutting process?

A

A Larger rake angle (𝛾0) reduces cutting forces and improves chip flow, also less resistance, less chip deformations, less cutting pressure, etc.
Clearance angle (𝛼0) ensures proper contact and reduces tool wear. Low 𝛼0 causes faster reaching of the max allowed flank wear. High 𝛼0 means the resistant section is too little.
Usually between 2Β° and 15Β°

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39
Q

[Turning] What is the importance of the main and secondary cutting edge angles?

A

These angles influence the distribution of cutting forces, tool life, and the finish of the surface.

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40
Q

[Turning] How does the cutting edge’s angle affect tool robustness and surface finish?

A

A smaller angle improves robustness and wear resistance, while a larger angle enhances surface finish

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41
Q

[Turning] What are the typical entering angles, and how do they impact turning?

A

Entering angles influence force distribution and chip flow. Lower angles improve chip evacuation but may increase tool wear, while higher angles provide better tool stability.

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42
Q

[Turning] What are the primary forces acting during turning?

A

-Feed Force: Moves the tool along the feed direction.
- Thrust Force: Stabilizes the tool perpendicular to the workpiece.
- Cutting force: Shears the material.

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43
Q

[Turning] Why is it necessary to verify cutting parameters before machining?

A

It ensures that the setup (tool, machine) can handle the forces, speeds, and cutting conditions without compromising safety or quality.

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44
Q

[Turning] How do you ensure the selected fixtures can securely hold the workpiece?

A

Fixtures must be verified for sufficient gripping force, alignment, and compatibility with the machining forces to prevent workpiece displacement or damage.
Tc <=
Tr
Cutting Torque <= Clamping Torque

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45
Q

[Turning] What are the factors to consider when verifying a lathe’s compatibility with a turning process?

A

Lathe Power, Rotational speed range, rigidity, tool-holding capability, workpiece size capacity

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46
Q

[Turning] What does the clamping pressure of a self-centering z-Jaw chuck depend on?

A

p >= pmin =
Fc . D /(z . u . A . Dstar)

z = number of jaws of the chuck
A = Jaw-Workpiece contact Area
u = static friction coefficient
D = Machined Diameter
Dstar = workpiece diameter at fixture position

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47
Q

[Turning] What causes Workpiece bending during turning?

A

Bending is caused by cutting forces acting on unsupported sections of the workpiece, especially for long or slender parts.

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48
Q

[Turning] What is the role of the moment of inertia in workpiece bending?

A

The moment of inertia determines the workpiece’s resistance to bending under cutting forces. Larger cross-sections with higher moments of inertia reduce deflection.

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49
Q

[Surface Finish] What are surface finish and surface integrity?

A
  • Surface Finish: the quality of a surface’s smoothness and appearance.
  • Surface Integrity: Surface’s mechanical, physical, and chemical properties.
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50
Q

[Surface Finish]Why are surfaces important in manufacturing and design?

A

Surfaces affect aesthetic, but also, safety, friction, wear, mechanical properties, and even functionality.

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51
Q

[Surface Finish] Why are surfaces important for electrical contacts?

A

Smooth surfaces reduce resistance at contact points, improving electrical conductivity.

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52
Q

[Surface Finish] What is the difference between an ideal surface and an actual surface?

A

An ideal surface is a perfect contour as designed. while an actual surface is one produced with manufacturing techniques, which in general produce imperfections and deviations from the ideal.

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53
Q

[Surface Finish] What is Surface Texture? What are its 4 main elements?

A

It refers to the topography and geometric features of a surface, including:
- Roughness: Fine deviations from the Ideal surface
- Waviness: Larger, periodic deviations usually caused by machine or workpiece vibrations
- Lay: the predominant direction of surface texture.
- Flaws: Irregularities like cracks, scratches, or inclusions.

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54
Q

[Surface Finish] How do mechanical processes influence the topography and geometric features of a surface?

A

Processes like machining, grinding, or casting impart characteristic patterns, roughness, and orientation to the surface due to tool marks, vibrations, and material flow during processing.

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55
Q

[Surface Finish] What is the difference between surface roughness and surface finish?

A
  • Surface Roughness: measurable parameter quantifying deviations from an ideal surface.
  • Surface Finish: Subjective term describing the overall quality and smoothness of the surface.
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56
Q

[Surface Finish] How are roughness deviations measured and characterized?

A

These are measured using stylus instruments or optical techniques. They are quantified using parameters like average roughness (Ra) or total height (Rt)

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57
Q

[Surface Finish] What is the relationship between surface roughness and surface texture?

A

Surface roughness is a component of surface texture, representing the finer, more closely spaced deviations superimposed on other texture elements like waviness.

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58
Q

[Surface Finish] How does a stylus electronic instrument measure surface roughness?

A

A stylus moves horizontally across the surface while vertically following the surface profile, with a probe touching the surface being measured, generating a trace of height deviations that can be analyzed.

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59
Q

[Surface Finish] What role does optical technology play in surface measurement?

A

Optical technology provides non-contact, high-res measurement of surface roughness and texture. Normally used for delicate, high-precision surfaces.

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60
Q

[Surface Finish] What is a cutoff length in roughness computation? Why is it used?

A

Cutoff length in roughness computation refers to a specific length selected as a sampling distance of the surface. A Sampling distance shorter than the Waviness of the surface eliminates deviations due to waviness and only includes roughness deviations.

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61
Q

[Surface Finish] In turning, what is the difference between theoretical and real roughness?

A
  • Theoretical: is calculated based o the geometric parameters of the process.
  • Real: Is the real roughness, which includes effects of tool wear, material properties, and process conditions.
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62
Q

[Surface Finish] How does tool nose radius affect surface roughness in turning?

A

A larger tool nose radius produces a smoother surface by reducing the height of the scallops (hills) left between successive tool passes.

63
Q

[Surface Finish] What are the effects of feed rate and nose radius on surface roughness (turning)?

A

A higher feed rate increases roughness by leaving larger scallops, while a larger nose radius smooths the surface by reducing scallop height.

64
Q

[Surface Finish] What are the primary international standards for specifying surface roughness?

A

ISO 21920 for profile parameters and ISO 25178 for areal surface parameters

65
Q

[Surface Finish] How do profile and areal specifications differ in surface measurement?

A
  • Profile specifications are mostly focused on the roughness along a single line (the profile).
  • Areal measure roughness over a 2D surface area, providing a more comprehensive view.
66
Q

[Surface Finish] What is the significance of parameters like Ra and Rt in defining surface characteristics?

A

Rt = f^2/(8.r) . 10^3 [ΞΌm] : is the total height of surface deviations. (f = feed and r = nose radius).
Ra = Rt/4 : is the average roughness.

67
Q

[Tool Life] What are the three primary modes of tool failure?

A

1.- Fracture failure: caused by excessive cutting forces or vibrations leading to brittle fracture.
2.- Temperature Failure: Occurs when cutting temperatures exceed the tool’s materials limits.
3.- Gradual Wear: Results from continuous use, leading to tool degradation over time.

68
Q

[Tool Life] What are the key factors that define tool life?

A

Wear criteria (Flank wear Limit, VB), cutting speed, feed rate, and depth of cut. It ends when the tool reaches a failure criterion, such as excessive wear or breakage.

69
Q

[Tool Life] What are the main materials used for cutting tools?

A

Carbon steels, high-speed steels, cast alloys, carbides, ceramics, cermets, cubic boron nitride (CBN), and diamond.

70
Q

[Tool Life] What are the properties we look for in a tool?

A

Toughness, wear resistance, hardness at increased temperatures, thermal stability, and chemical inertia.

71
Q

[Tool Life] What role does machining economics play in tool life?

A

It involves optimizing cutting conditions in order to balance tool cost, tool life, production time, and production cost for maximum efficiency and affordability.

72
Q

[Tool Life] What are the main causes of tool wear?

A
  • Mechanical: Abrasion from hard particles in the workpiece.
  • Thermal: High temperatures causing softening or deformation.
  • Chemical: Oxidation or diffusion at the tool-material interface.
73
Q

[Tool Life] What are the mechanisms of wear formation?

A
  • Abrasion: Hard particles scratch the tool.
  • Diffusion: Atoms migrate betwen the workpiece and the tool.
  • Oxidation: Oxides form and degrade the tool surface.
  • Adhesion: Built-up edge causes localized tool damage.
  • Plastic deformation: Mechanical and thermal stresses soften the tool.
  • Fatigue: Repeated thermal and mechanical cycles weaken the tool.
74
Q

[Tool Life] What factors influence tool wear?

A

Tool material and geometry. Cutting speed, feed rate, lubrication, temperature, chemical compatibility between tool and workpiece.

75
Q

[Tool Life] What are the two main locations of tool wear?

A
  • Flank wear: Occurs on the flank face, affecting surface finish and dimensional accuracy.
  • Crater wear: Develops on the rake face, weakening the tool
76
Q

[Tool Life] What parameters quantify flank and crater wear?

A
  • Flank wear is measured by VB (avrg flank wear) or VBMAX (maximum flank wear)
  • Crater wear is measured by KT (crater depths) and KM (position of the deepest point)
77
Q

[Tool Life] Why is it essential to define a failure criterion for tool life?

A

This criterion ensures tools are replaced before catastrophic failure, minimizing downtime, and possible machining error caused by these failures (maintains part quality). E.g. VBlimit

78
Q

[Tool Life] What is the typical progression of tool wear during cutting?

A

1st. Break-in period: Rapid initial wear as the tool stabilizes.
2nd. Steady-state wear: Uniform wear rate during most of the tool’s life.
3rd. Failure region: Accelerated wear leading to failure.

Graph looks like a y=x^3

79
Q

[Tool Life] What are the advantages of coated cutting tools?

A

Coatings like titanium nitride or aluminum oxide improve wear resistance, reduce friction, and enhance thermal stability, increasing tool life and performance.

80
Q

[Tool Life] What are the benefits of using advanced cutting materials like CBN or DIamond?

A

These offer exceptional hardness and wear resistance, making them suitable for high-speed cutting and machining of hard materials.

81
Q

[Tool Life] What is Taylor’s tool life law?

A

vcT^n=C
where:
vc = Cutting speed [mm/min]
T = tool life [min]
n = Exponent that depends on cutting tool material
C = Constant depending on workpiece material and other machining parameters.

82
Q

[Tool Life] How does cutting speed affect tool life?

A

Higher cutting speeds reduce tool life due to increased wear rates, while lower speeds extend tool life but may reduce productivity.

83
Q

[Tool Life] What are the primary objectives of machining optimization?

A

Minimize production costs, maximize productivity, and achieve desired surface quality.

84
Q

[Tool Life] What factors should be considered when optimizing machining conditions?

A

Cutting speed, tool material, workpiece material, cooling, machine constraints, and required surface finish.

85
Q

[Tool Life] What is the relationship between production cost and tool life?

A

Longer tool life reduces tool replacement costs but may increase machining time, affecting the balance between cost and efficiency.

86
Q

[Milling] What is the goal of Milling operations?

A

To create a wide range of surfaces, including planes, slots, shoulders, and complex geometries

87
Q

[Milling] What are the basic motions in milling?

A

The cutting motion (vc) is provided by the tool, while the feed motion (vf) is provided by the part and/or tool.

88
Q

[Milling] What is the primary tool used in milling, and what are its features?

A

The primary tool is called a β€œCutter”. It has multiple teeth (cutting edges) that engage the workpiece cyclically.

89
Q

[Milling] What are the two main forms of milling?

A
  • Peripheral milling: The cutter axis is parallel to the surface being machined, and cutting edges are on the periphery of the cutter.
  • Face milling: The cutter axis is perpendicular to the surface, and cutting edges are on both the end and periphery of the cutter
90
Q

[Milling] What are some common types of peripheral milling?

A

Slab milling, slotting, side milling, straddle milling, and form milling.

91
Q

[Milling] What are some common types of face milling?

A

Conventional face milling, partial face milling, end milling, profile milling, pocket milling, and surface contouring.

92
Q

[Milling] What is end milling, when is it used?

A

The machining of profiles and contours using an end mill. it is used for creating intricate features like slots, pockets, and surfaces.

93
Q

[Milling] What is slotting, what are its applications?

A

Slotting creates slots of various geometries (T, V, U). It is often used for keyways, grooves, and precision cuts.

94
Q

[Milling] What are the main types of milling machines?

A

Horizontal-spindle column+knee, Vertical-spindle column+knee (knee miller, and bed-types milling.

95
Q

[Milling] What are the features of a CNC milling machine?

A

These provide programmable control for precision and complex milling operations, allowing automation and consistent results.

96
Q

[Milling] What is the role of the arbor in horizontal milling machines?

A

The arbor supports the milling cutter, ensuring stability and accurate machining.

97
Q

[Milling] What are the key machining parameters in milling?

A

N. of teeth (Z), feed per toot (fz), mill diameter (D), rotational speed (n), cutting speed (vc), and feed velocity (vf)

98
Q

[Milling] What is axial depth of cut and radial depth of cut?

A
  • Axial depth of cut (ap) is the thickness of the material removed in face milling.
  • Radial depth of cut (ae) is the width of the material removed in slab milling.
99
Q

[Milling] What is slab milling?

A

It’s a type of peripheral milling where the cutter axis is parallel to the surface, and only the cylindrical part of the mill is engaged in cutting.

100
Q

[Milling] What is the difference between conventional (up) and climbing (down) milling?

A
  • Conventional: The cutter slides before cutting, causing more wear and heating.
  • Climbing: The cutter starts with a thick chip, reducing sliding but risking tool fracture due to the initial shock.
101
Q

[Milling] What are the forces acting during slab milling?

A

Cutting force (Fc)
Feed force (Ff)
their respective normal components

102
Q

[Milling] What distinguishes face milling from peripheral milling?

A

In face Milling the cutter axis is perpendicular to the surface, and both the face and periphery of the cutter are engaged in cutting

103
Q

[Milling] What is the effect of lead angle on chip thickness in face milling?

A

A larger lead angle decreases chip thickness but increases the length of contact (Chip width), affecting tool wear and finish

104
Q

[Milling] What are the forces in face milling?

A

Same as in slab milling:
Cutting force (Fc)
Feed force (Ff)
their respective normal components

105
Q

[Milling] How is cutting time in milling determined?

A

It depends on the length of the cut (L), approach distance (A), and feed velocity (vf).

106
Q

[Milling] What Factors influence surface roughness in milling?

A

Tool geometry (Nose radius, entering angle), feed rate, depth of cut, and machine/tool vibrations.

107
Q

[Milling] How does surface roughness differ between slab and face milling?

A

Slab milling roughness primarily depends on the feed per tooth (fz) and cutter diameter.
Face milling roughness is also influenced by entering angle and tool path.

108
Q

[Milling] What are the advantages of milling compared to other machining processes?

A

Milling can create a wide variety of geometries, including planar and complex surfaces, with high precision and flexibility.

109
Q

[Milling] What are some common challenges in milling operations?

A

Managing tool wear, achiving consistent surface finish, and minimizing vibrations and tool deflection.

110
Q

[Milling] How do interrupted cutting operations affect tool life in milling?

A

The cyclic engagement of the tool with the workpiece increases wear and thermal stresses but allows better cooling and chip removal.

111
Q

[Drilling] What’s the Purpose of Drilling?

A

Drilling is used to create round holes in a workpiece using a cutting tool called a drill bit

112
Q

[Drilling] What are the basic machine tools used in drilling?

A

Drill press machines (Upright, or bench-mounted), or CNC controlled.

113
Q

[Drilling] What is the difference between a Through Hole and a Blind Hole?

A

A through hole passes entirely through the workpiece.
A blind hole stops partway through the workpiece.

114
Q

[Drilling] What are some common types of holes created during drilling?

A
  • Through Holes: Pass though the workpiece.
  • Blind holes: Don’t go all the way through the workpiece.
  • Countersink: Creates a CONICAL entry to a hole (Accomodating a flat-head screw)
  • Counterbore: Creates a cylindrical recess at the top of the hole (Housing bolt heads or washers)
  • Conical Holes: Use a special tool that creates a conical hole in the workpiece instead of a cylindrical one.
  • Holes with multiple features: Usea special tools that create different features in the workpiece (Maybe like steps of different diameters)
115
Q

[Drilling] What is the function of the helicoidal flutes on a twist drill?

A

The flutes allow chips to be removed from the cutting zone. For large-diameter drills, the tool may be hollow to allow cutting fluid to reach the cutting zone.

116
Q

[Drilling] What are the key features of a twist drill?

A

It includes a point, cutting edges, flutes and a shank. It’s commonly used for drilling round Cylindrical holes.

117
Q

[Drilling] What are the main cutting parameters in drilling?

A
  • Feed per revolution (f)
  • Drill diameter (D)
  • Rotational speed (n)
  • Cutting speed (vc
118
Q

[Drilling] What forces act on the tool during drilling?

A

Forces due to chip formation, friction, and forces on the chisel edge from the feed.

119
Q

[Drilling] How does friction affect the drilling process?

A

Friction between the drill and the workpiece increases tool wear, cutting temperature, and energy consumption.

120
Q

[Drilling] What factors influence the cutting time in drilling?

A

Cutting time depends on the hole depth (L), approach distance (A), and feed velocity (vf)

121
Q

[Drilling] How does cutting speed affect drilling efficiency?

A

Higher cutting speeds reduce machining time but may increase heat generation and tool wear.

122
Q

[Drilling] What are some challenges in achieving tight tolerances during drilling?

A

Drill bending, misalignment and surface irregularities at the entry point of the drill

123
Q

[Drilling] What are the best practices for drilling precision holes?

A

Ensure a flat entry surface, drill in multiple passes (progressive increase of drill hole), and use appropriate cutting parameters.

124
Q

[Drilling] What is Reaming? When is it used?

A

Reaming enlarges existing holes to achieve tight tolerances and smooth surfaces. Reamers cannot be used to create new holes.

125
Q

[Drilling] What is tapping? What are its applications?

A

Tapping creates internal threads in holes for screws or bolts.

126
Q

[Drilling] What is countersinking? Why is it performed?

A

Countersinking creates a conical entry to a hole, often for accommodating flat-head screws.

127
Q

[Drilling] What is Counterboring? when is it used?

A

Counterboring creates a cylindrical recess at the top of a hole, often used to house bolt heads or washers.

128
Q

[Drilling] What is spot facing?

A

Spot facing creates a smooth, flat surface around a hole to ensure proper seating of fasteners.

129
Q

[Drilling] What is deep hole drilling? What tools are used for this process?

A

Deep hole drilling involves creating holes with a high depth-to-diameter ratio. Gun drills are commonly used for this purpose, which are a hollow straight-flute drill. With these we can create holes of up to 125:1 depth-to-diameter ratio.

130
Q

[Drilling] What are normal depth-to-diameter ratio of twist drills? what about straight-flute drills? and Gun drills?

A
  • Twist drill: d-t-d = 5:1
  • Straight-flute: d-t-d = 3:1
  • Gun drill: d-t-d = 125:1 (Or even more)
131
Q

[Drilling] What are the main types of drilling tools?

A
  • Twist Drills
  • Reamers
  • Taps
  • Straight-Flute Drills
  • Gun Drills
132
Q

[Drilling] What are the advantages of using a straight-flute drill over a twist drill? Disadvantages?

A

Straight-flute drills are used for specialized drilling applications, specially where rigidity and control are critical, particularly for harder or brittle materials.
They normally permit a lower depth-to-diameter ratio, limiting its uses to not so deep purposes.

133
Q

[Drilling] What is trepanning? how does it differ from conventional drilling?

A

Trepanning removes material as a ring rather than converting the hole volume into chips. This reduces power requirements.

134
Q

[Drilling] What are the main types of drill presses?

A
  • Upright drill presses: for general use
  • Bench drill presses: for smaller operations.
  • Radial drill presses: for large parts.
135
Q

[Drilling] What are the advantages of a CNC drilling machine?

A

These offer precision, repeatability, and the ability to create more complex hole patterns with minimal manual intervention.

136
Q

[Drilling] What are common work-holding devices used in drilling?

A
  • Vise: General-purpose clamp
  • Fixture: Custom-designed holder for a specific part.
  • Drill jig: Similar to a fixture but also guides the tool during drilling for accuracy.
137
Q

[Process Planning] What is Process Planning in Manufacturing?

A

Its planning of manufacturing processes to produce high-quality products economically. It includes selecting processes, determining the tooling, choosing equipment, and estimating costs.

138
Q

[Process Planning] What department is responsible for process planning in manufacturing companies?

A

The Manufacturing Engineering Department.

139
Q

[Process Planning] What are the typical steps in a processing sequence?

A
  • Basic Processes: Establish the initial geometry of the part.
  • Secondary processes: Refine the geometry into the final shape.
  • Property enhancement operations: Improve physical properties
  • Finishing operations: Achieve the desired surface quality and tolerances.
140
Q

[Process Planning] What factors should be considered when selecting equipment for process planning?

A

Use existing equipment whenever possible to save costs. If necessary, purchase new equipment or outsource operations.

141
Q

[Process Planning] What information should be specified in the process plan?

A

The types of tools, dies, molds, fixtures, gages, and cutting tools, as well as the cutting conditions and production methods (Manuel/automated, etc)

142
Q

[Process Planning] How are production costs estimated during process planning?

A

This is done in collaboration with cost estimators, considering labor, tooling, material, and equipment costs.

143
Q

[Process Planning] What is a route sheet? Why is it important?

A

It is essential to the process planner as an engineering drawing is to the designer.

144
Q

[Process Planning] What types of machining operations are typically included in process planning?

A

Turning, milling, drilling, threading, countersinking, grooving, and grinding.

145
Q

[Process Planning] Why are multiple setups often necessary in machining?

A

They allow for access to various surfaces or features of the part and accommodate different tools or workholding methods.

146
Q

[Process Planning] What is the purpose of using self-centering 3-jaw chucks in setups?

A

These ensure accurate alignment and secure holding of the workpiece during machining.

147
Q

[Process Planning] What are some operations performed in the first setup?

A

Facing, internal cylindrical turning (Roughing and finishing), countersinking, twist drilling, counterboring, and threading.

148
Q

[Process Planning] What additional operations are performed in the second setup?

A

Profiling, grooving, slotting, pocjet milling, twist drilling, and threading for multiple holes.

149
Q

[Process Planning] Why are finishing operations like grinding required?

A

These achieve tight tolerances and smooth surface finishes necessary for the part’s functionality or aesthetics

150
Q

[Process Planning] What is grinding and how does it work?

A

It’s a material removal process using abrasive particles bonded in a wheel. the wheel rotates at high speed, cutting the workpiece with precision.

151
Q

[Process Planning] What challenges must be addressed during process planning?

A

Balancing cost, efficiency, and quality. Ensuring compatibility with existing equipment. Managing complex part requiring multiple setups.

152
Q

[Process Planning]

A
153
Q

[Process Planning]

A

Polimi 1st Sem (4 decks)

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