Computer Aided Manufacturing

Question 1

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

Answer 1

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

Question 2

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

Answer 2

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

Question 3

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

Answer 3

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)

Question 4

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

Answer 4

• v_c = cutting speed
• b = cutting width
• h_D = cutting thickness (chip thickness before cutting)
• A_D = chip transversal section before cutting
• h_ch = chip thickness after cutting
• r = Chip thickness ratio < 1

Question 5

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

Answer 5

• 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.

Question 6

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

Answer 6

• Rake Angle 𝜸_𝟎: angle between rake face and the normal to the cutting direction. -15° <= 𝜸_𝟎 <= 30°
• Clearance angle 𝜶_𝟎: Angle between flank face and cutting direction. 2° <= 𝜶_𝟎 <= 15°
• Solid angle 𝜷_𝟎: Between rake and flank faces.
• 𝛼_𝟎 + 𝛽_𝟎 + 𝛾_𝟎 = 90°

Question 7

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

Answer 7

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.

Question 8

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

Answer 8

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).

Question 9

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

Answer 9

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

Question 10

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

Answer 10

• 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)

Question 11

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

Answer 11

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.

Question 12

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

Answer 12

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

Question 13

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

Answer 13

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

Question 14

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

Answer 14

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

Question 15

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

Answer 15

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.

Question 16

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

Answer 16

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

Question 17

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

Answer 17

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

Question 18

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

Answer 18

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.

Question 19

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

Answer 19

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

Question 20

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

Answer 20

k_c = k_cs/h_D^x
where:
- k_cs is the specific cutting pressure related to the workpiece material
- x is a constant related to the tool material.
- h_D 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.

Question 21

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

Answer 21

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.
E_c = k_c*V = F_c * L_c

Question 22

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

Answer 22

t_c = L_c/v_c = V / MRR

V is the removed material volume

Question 23

[Turning] What are the basic principles of Turning?

Answer 23

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

Question 24

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

Answer 24

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

Question 25

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

Answer 25

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

Question 26

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

Answer 26

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

Question 27

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

Answer 27

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

Question 28

[Turning] In what scenarios is grooving used?

Answer 28

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

Question 29

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

Answer 29

Machined Diameter (D), feed rate (f), depth of cut (a_p), chip thickness (h_D), rotational speed (n), and cutting speed (v_c)

Question 30

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

Answer 30

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

Question 31

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

Answer 31

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

Question 32

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

Answer 32

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.

Question 33

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

Answer 33

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

Question 34

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

Answer 34

- 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.

Question 35

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

Answer 35

- 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 "tube". 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.

Question 36

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

Answer 36

- Shank: mounts the tool. - Cutting head: performs the cutting. - Optional Inserts: replaceable cutting edges.

Question 37

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

Answer 37

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

Question 38

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

Answer 38

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 2° and 15°

Question 39

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

Answer 39

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

Question 40

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

Answer 40

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

Question 41

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

Answer 41

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.

Question 42

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

Answer 42

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

Question 43

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

Answer 43

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

Question 44

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

Answer 44

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

Question 45

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

Answer 45

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

Question 46

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

Answer 46

p >= p_min = F_c . D /(z . u . A . D^star) z = number of jaws of the chuck A = Jaw-Workpiece contact Area u = static friction coefficient D = Machined Diameter D^star = workpiece diameter at fixture position

Question 47

[Turning] What causes Workpiece bending during turning?

Answer 47

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

Question 48

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

Answer 48

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

Question 49

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

Answer 49

- Surface Finish: the quality of a surface's smoothness and appearance. - Surface Integrity: Surface's mechanical, physical, and chemical properties.

Question 50

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

Answer 50

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

Question 51

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

Answer 51

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

Question 52

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

Answer 52

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.

Question 53

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

Answer 53

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.

Question 54

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

Answer 54

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.

Question 55

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

Answer 55

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

Question 56

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

Answer 56

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

Question 57

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

Answer 57

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

Question 58

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

Answer 58

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.

Question 59

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

Answer 59

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

Question 60

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

Answer 60

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.

Question 61

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

Answer 61

- 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.

Question 62

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

Answer 62

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

Question 63

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

Answer 63

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

Question 64

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

Answer 64

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

Question 65

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

Answer 65

- 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.

Question 66

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

Answer 66

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

Question 67

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

Answer 67

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.

Question 68

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

Answer 68

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.

Question 69

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

Answer 69

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

Question 70

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

Answer 70

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

Question 71

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

Answer 71

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

Question 72

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

Answer 72

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

Question 73

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

Answer 73

- 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.

Question 74

[Tool Life] What factors influence tool wear?

Answer 74

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

Question 75

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

Answer 75

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

Question 76

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

Answer 76

- Flank wear is measured by VB (avrg flank wear) or VB_MAX (maximum flank wear) - Crater wear is measured by KT (crater depths) and KM (position of the deepest point)

Question 77

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

Answer 77

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

Question 78

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

Answer 78

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

Question 79

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

Answer 79

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

Question 80

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

Answer 80

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

Question 81

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

Answer 81

v_cT^n=C where: v_c = 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.

Question 82

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

Answer 82

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

Question 83

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

Answer 83

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

Question 84

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

Answer 84

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

Question 85

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

Answer 85

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

Question 86

[Milling] What is the goal of Milling operations?

Answer 86

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

Question 87

[Milling] What are the basic motions in milling?

Answer 87

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

Question 88

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

Answer 88

The primary tool is called a "Cutter". It has multiple teeth (cutting edges) that engage the workpiece cyclically.

Question 89

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

Answer 89

- 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

Question 90

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

Answer 90

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

Question 91

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

Answer 91

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

Question 92

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

Answer 92

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

Question 93

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

Answer 93

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

Question 94

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

Answer 94

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

Question 95

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

Answer 95

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

Question 96

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

Answer 96

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

Question 97

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

Answer 97

N. of teeth (Z), feed per toot (f_z), mill diameter (D), rotational speed (n), cutting speed (v_c), and feed velocity (v_f)

Question 98

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

Answer 98

- Axial depth of cut (a_p) is the thickness of the material removed in face milling. - Radial depth of cut (a_e) is the width of the material removed in slab milling.

Question 99

[Milling] What is slab milling?

Answer 99

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.

Question 100

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

Answer 100

- 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.

Question 101

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

Answer 101

Cutting force (F_c) Feed force (F_f) their respective normal components

Question 102

[Milling] What distinguishes face milling from peripheral milling?

Answer 102

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

Question 103

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

Answer 103

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

Question 104

[Milling] What are the forces in face milling?

Answer 104

Same as in slab milling: Cutting force (F_c) Feed force (F_f) their respective normal components

Question 105

[Milling] How is cutting time in milling determined?

Answer 105

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

Question 106

[Milling] What Factors influence surface roughness in milling?

Answer 106

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

Question 107

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

Answer 107

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

Question 108

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

Answer 108

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

Question 109

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

Answer 109

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

Question 110

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

Answer 110

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

Question 111

[Drilling] What's the Purpose of Drilling?

Answer 111

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

Question 112

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

Answer 112

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

Question 113

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

Answer 113

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

Question 114

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

Answer 114

- 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)

Question 115

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

Answer 115

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.

Question 116

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

Answer 116

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

Question 117

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

Answer 117

- Feed per revolution (f) - Drill diameter (D) - Rotational speed (n) - Cutting speed (v_c

Question 118

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

Answer 118

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

Question 119

[Drilling] How does friction affect the drilling process?

Answer 119

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

Question 120

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

Answer 120

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

Question 121

[Drilling] How does cutting speed affect drilling efficiency?

Answer 121

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

Question 122

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

Answer 122

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

Question 123

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

Answer 123

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

Question 124

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

Answer 124

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

Question 125

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

Answer 125

Tapping creates internal threads in holes for screws or bolts.

Question 126

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

Answer 126

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

Question 127

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

Answer 127

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

Question 128

[Drilling] What is spot facing?

Answer 128

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

Question 129

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

Answer 129

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.

Question 130

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

Answer 130

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

Question 131

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

Answer 131

- Twist Drills - Reamers - Taps - Straight-Flute Drills - Gun Drills

Question 132

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

Answer 132

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.

Question 133

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

Answer 133

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

Question 134

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

Answer 134

- Upright drill presses: for general use - Bench drill presses: for smaller operations. - Radial drill presses: for large parts.

Question 135

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

Answer 135

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

Question 136

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

Answer 136

- 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.

Question 137

[Process Planning] What is Process Planning in Manufacturing?

Answer 137

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

Question 138

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

Answer 138

The Manufacturing Engineering Department.

Question 139

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

Answer 139

- 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.

Question 140

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

Answer 140

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

Question 141

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

Answer 141

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

Question 142

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

Answer 142

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

Question 143

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

Answer 143

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

Question 144

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

Answer 144

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

Question 145

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

Answer 145

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

Question 146

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

Answer 146

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

Question 147

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

Answer 147

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

Question 148

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

Answer 148

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

Question 149

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

Answer 149

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

Question 150

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

Answer 150

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

Question 151

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

Answer 151

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

Question 152

[CNC Tools] What are the main actuator types in CNC machines?

Answer 152

AC Motors: Rugged and reliable, used in spindles. DC Motors: Easy speed control, high maintenance Brushless DC: High precision, high cost Stepper Motors: Precise, low power, low cost

Question 153

[CNC Tools] What is a ball screw and why is it used?

Answer 153

A mechanism that converts rotary motion into linear motion. Highly efficient, minimal backlash, high accuracy.

Question 154

[CNC Tools] What are linear guideways and why are they used?

Answer 154

These are similar to bearings, but they're linear, so they guide the motion linearly with low friction, high accuracy, and high load capacity

Question 155

[CNC Tools] What are the types of position measurement systems?

Answer 155

- Absolute: Each position has a unique reference. - Incremental: Measures relative to the last position - Cyclic absolute: A combination of both

Question 156

[CNC Tools] What's the difference between accuracy repeatability, and resolution?

Answer 156

- Accuracy: Closeness to true position. - Repeatability: Ability to return to the same point. - Resolution: smallest detectable movement.

Question 157

[CNC Tools] What are the main components in a CNC system?

Answer 157

Actuators, Rotary-to-Linear converters, Position/Velocity sensors, Velocity controller, Part program input, HMI.

Question 158

[CNC Tools] What is the NCK?

Answer 158

Numerical Control Kernel. This is a subsystem that handles: Code parsing, interpolation, Servo control, and error compensations

Question 159

[CNC Tools] What are the types of CNC tool path control?

Answer 159

- Point-to-Point: For drilling, punching. - Continuous path: For milling, turning complex shapes

Question 160

[CNC Tools] What types of interpolation exist in CNC?

Answer 160

- Linear - Circular - Helical - Parabolic/cubic (for freeform surfaces)

Question 161

[CNC Tools] What does Helical Interpolation do?

Answer 161

This type of interpolation combines a circular interpolation in 2D with a linear motion on a 3rd axis, creating a 3D helical path. Useful for thread milling or spiral ramping.

Question 162

[CNC Tools] What are the key structural requirements of CNC machines?

Answer 162

High stiffness, High damping, Low thermal distortion, Strong foundation

Question 163

[CNC Tools] What are the differences in performance between cast iron and welded steel in a machine bed?

Answer 163

- Cast Iron: Good damping, low Cost, very heavy - Welded Steel: Lighter, better mechanical properties (stiffness), but less damping

Question 164

[CNC Tools] What are the 2 main types of CNC machine tools?

Answer 164

- Single-Purpose: For one type of operation. - Multi-Purpose: With many different capabilities

Question 165

[CNC Tools] What is a turning center and its components?

Answer 165

A lathe with CNC control with: - Automatic part loading/unloading - Multiple turrets and spindles - Driven tools (for drilling/milling) - Chip removal systems.

Question 166

[CNC Tools] What are machining centers and how are they classified?

Answer 166

CNC milling machines with automatic tool changers, classified by: - Spindle orientation: vertical/horizontal - Type of axis motion: tool movement, or table movement (or both

Question 167

[CNC Tools] What is a toolholder and what types exist?

Answer 167

A device connecting the cutting tool to the machine spindle. - ISO: Traditional, subject to deformation at high speeds. - HSK: Hollow shaft, high-speed capable, short, double contact.

Question 168

[CNC Tools] What is an Automatic Tool Changer?

Answer 168

ATC, a mechanism that switches between tools automatically.

Question 169

[CNC Tools] What is a pallet and fixture in machining centers?

Answer 169

- Pallet: Platform for fixing and referencing parts on the machine. - Fixture: Device that holds, supports, and locates the workpiece

Question 170

[CNC Programming] What are G-Code and M-Code used for?

Answer 170

G-code controls movement, coordinate systems, and interpolation M-code controls machine operations like spindle rotation, coolant and tool change.

Question 171

[CNC Programming] What coordinate systems are used in CNC?

Answer 171

- Machine coordinate system: fixed by manufacturer. - Workpiece coordinate system: fixed on the part

Question 172

[CNC Programming] What is the difference between G90 and G91 (G-code)?

Answer 172

G90 is used for absolute programming (specific absolute coordinates for the movement) G91 is used for Incremental programming (coordinates with respect to the last point for the movement)

Question 173

[CNC Programming] What are common interpolation commands?

Answer 173

- G00: rapid positioning - G01: Linear interpolation - G02/G03: Circular interpolation (CW/CCW)

Question 174

[CNC Programming] What is STEP-NC (ISO 14649)?

Answer 174

A modern standard for CNC programming based on features and operations, allowing machine-independent and intelligent part programming. It's a high level programming option.

Question 175

[Coordinate Measuring Machines] What is a CMM?

Answer 175

A device capable of measuring spatial coordinates on a workpiece surface using some sort of probing system (ISO 10360-1)

Question 176

[Coordinate Measuring Machines] What types of displacement systems are used in CCMs?

Answer 176

Ball screws, rack and pinion, pulleys, and friction-based systems.

Question 177

[Coordinate Measuring Machines] What's the difference between passive and active probes?

Answer 177

- Passive: rely on elastic deformation. - active: use actuators for dynamic control of contact forces

Question 178

[Coordinate Measuring Machines] Why is scan speed limited in CMMs?

Answer 178

Because dynamic forces and vibrations during scanning introduce errors.

Question 179

[Coordinate Measuring Machines] What is Process capability (Cp, Cpk)?

Answer 179

These are statistical measures to assess how well a process can produce parts within specified limits. Cp = (USL - LSL)/(6*sigma) Cpk = min[(USL-mean) / (3*sigma), (mean- LSL) / (3*sigma)] where USL = Upper Specification Limit and LSL= Lower Specification Limit

Question 180

[Coordinate Measuring Machines] What is one-sided vs two-sided specification?

Answer 180

One-sided: only in one direction (only upper, or only lower limit) two-sided: tolerance applies to both above and below nominal

Question 181

[Volumetric Error Compensation] What is 3D x-ray computed tomography used for?

Answer 181

A non-contact measurement method capturing volumetric data using multiple x-ray images.

Question 182

[Volumetric Error Compensation] What is voxel-based representation?

Answer 182

A spatial occupancy model using small cubes (voxels) to represent a 3D object

Question 183

[Volumetric Error Compensation] What are the main error sources in CNC machines?

Answer 183

Kinematic errors, squareness errors, thermal deformation, reversal errors, random errors.

Question 184

[Volumetric Error Compensation] What is Volumetric Error?

Answer 184

The combined error in a machine tool's workspace caused by geometric and thermal effects, affecting the tool's real and expected position

Question 185

[Volumetric Error Compensation] What are 3 software comensation methods for volumetric error?

Answer 185

- Error Grid. - Error Table. - Coefficient Table