TG - 3D/2D CAD Commands

Question 1

What is a library of parts?

Answer 1

• Collection of standard parts commonly used for assemblies

- Nuts, screws, bolts, etc

Question 2

What are 3 benefits of a library of parts?

Answer 2

• Saves time as CAD designer doesn’t need to model standard parts
• Ensures standard parts are consistent with international standards
• Allows manufacturers to understand what standard components are required

Question 3

What are 5 advantages to 2D CAD over manual drawing?

Answer 3

• Quicker and more accurate production
• Easier to edit/change
• Repetitive elements can easily be imported via library
• New designs can be built off existing designs
• Drawings can easily be scaled

Question 4

What are 5 disadvantages of CAD compared to manual drawing?

Answer 4

• Start-up and maintenance costs
• Continual need to upgrade systems to remain competitive
• Risks of viruses/crashes preventing work
• Power-cuts preventing work
• Staff training costs

Question 5

What are 5 advantages of 3D CAD over physical modelling?

Answer 5

• Cheaper to model and test than physical model
• Easy to edit and change with changing design
• No need to source materials/resources
• Animation allows designer to see how parts interact
• More quick to create and more accurate

Question 6

Lists 2 different arrays

Answer 6

• Radial array

- Rectangular array

Question 7

What are 2 common files used when importing/exporting CAD models?

Answer 7

• STL

- IGES

Question 8

Name 6 different CAD constraints and their purpose

Answer 8

• Concentric: aligns two circles
• Parallel: puts two lines in parallel
• Tangent: makes a line touch a circle
• Coincidental: fixes a line to a particular point
• Collinear: causes lines/ellipses to fall on a certain line
• Perpendicular: puts a line at 90 degrees to another

Question 9

What is surface modelling?

Answer 9

• Directly changes the surface of a wire model
• Adds curves, contours or other elements to a flat surface
• Works in squares or polygons
• Does not provide solid properties, such as weight or centre of mass

Question 10

What is an extrusion along a path?

Answer 10

• A path is defined and then a profile is defined on a plane perpendicular to the path
• The profile is then extruded along the defined path

Question 11

What is morphing?

Answer 11

• Pulling or distorting a model using ‘handles’ to form a new shape
• Similar to surface modelling but with 3D CAD
• Typically used for more natural shapes

Question 12

What are irregular fillets/chamfers?

Answer 12

• Where the chamfer/fillet changes in depth/radius throughout the edge
• Fillets create curves, chamfers create flat faces

Question 13

What is a loft?

Answer 13

• Links two or more sketches together to create a 3D shape
• Can be edited and pulled to create various shapes
• Typically used for irregular geometry which can’t be achieved with extrusions/revolves

Question 14

What is blending?

Answer 14

• Similar to a chamfer/fillet
• Connects two 2D/3D sketches/objects smoothly or with a consistent curve
• Effectively ‘blends’ two shapes together
• Either a tangent or a curve blend (3rd or 5th degree spline)

Question 15

Where is the plan in third angle projection?

Answer 15

Above the elevation

Question 16

Where is the plan in first angle projection?

Answer 16

Below the elevation

Question 17

Is the trapezium to the left or right of the circle in first angle projection?

Answer 17

Left

Question 18

What does CFD stand for?

Answer 18

Computational fluid dynamics

Question 19

What does FEA stand for?

Answer 19

Finite element analysis

Question 20

What is CFD used for?

Answer 20

• Analysing how air, water, or other fluids interact with a project
• Highlights points of pressure on design
• Shows if vortexes are forming and where within the product

Question 21

What is FEA used for?

Answer 21

• Analyses how a product reacts to forces and pressures within a virtual environment
• Shows high points of stress and can estimate the breaking point for various materials/joints

Question 22

What are 3 benefits of CFD?

Answer 22

• Instantaneously yields data that is useful for improving the design
• Cost effective
• Effectively locates where vents, heaters and other air-flow machines can be placed

Question 23

What are 3 benefits of FEA?

Answer 23

• Much less expensive than testing and potentially breaking real-life models/components
• Can easily be altered and re-tested in a short amount of time
• Colours give a clear and precise idea of how the product reacts to forces

Question 24

What is mechanical animation?

Answer 24

• Create a simulation of 3D CAD models moving to represent assemblies, components or products and how they interact with each other
• Helps to show efficiency of product
• Helps to make clients understand how the product is going to look

Question 25

List 5 different CAM machines

Answer 25

• 3D printer
• Lathe
• Router
• Laser cutter
• Milling machine

Question 26

What are 5 different elements that FEA tests?

Answer 26

• Mechanical stress and vibration
• Fatigue
• Motion
• Heat transfer
• Fluid low

Question 27

What is a roughing process used for in CAM?

Answer 27

• Roughly cuts out the model
• Gets rid of excess materials
• Typically large cuts taken in a zig-zag manner

Question 28

What is a semi-finishing process used for in CAM?

Answer 28

• Works from a roughed product and takes it to a nicer finish
• Middle stages are usually required for difficult materials to process
• Uses raster passes and pencil millings

Question 29

What is a finishing process used for in CAM?

Answer 29

• Final cuts to make a smooth and high-quality finish

- Much more slow than semi-finishing or roughing due to time taken for quality

Question 30

What is contour milling?

Answer 30

• Milling which achieves a much higher quality finish

- Not only moves the tool on 4-axis but can also rotate, hence using a 5-axis tool

Question 31

How can we calculate the mass/centre of mass/volume of a model for CAM?

Answer 31

• Using CAD software packages

- Input material used and rough weight of 1 cm^3 of said material and the software will run a calculation for you

Question 32

Why is COM/mass/volume important in CAM processes?

Answer 32

• Manufacturing engineers need to check whether the mass of a product is within a CAM machines’ limits