CAD CAD Specialist Mechanical Design and Manufacturing 3 — Questions and Answers
Question 1: In parametric mechanical CAD, what is the difference between a 'driven' dimension and a 'driving' dimension?
- Driven dimensions control geometry; driving dimensions display reference values only
- Driving dimensions control geometry; driven dimensions display reference values controlled by the model (Correct answer)
- They are interchangeable terms for the same concept
- Driven dimensions are in millimeters; driving are in inches
Correct answer: Driving dimensions control geometry; driven dimensions display reference values controlled by the model
Driving dimensions actively control model geometry, while driven (reference) dimensions are calculated and displayed but do not control the model.
Question 2: What is the purpose of a 'knurl' callout on a mechanical drawing?
- Specifying the thread pitch of a fastener
- Indicating a textured surface pattern rolled onto a cylindrical part for grip (Correct answer)
- Defining the surface finish of a bearing race
- Calling out a press-fit tolerance
Correct answer: Indicating a textured surface pattern rolled onto a cylindrical part for grip
A knurl callout specifies a diamond or straight cross-hatch pattern rolled into a cylindrical surface to improve grip or enable press-fit assembly.
Question 3: Which ASME standard governs engineering drawing practices and GD&T in the United States?
- ASME Y14.5 (Correct answer)
- ISO 1101
- ANSI B4.1
- ASTM E18
Correct answer: ASME Y14.5
ASME Y14.5 is the US standard that defines all rules, symbols, and practices for Geometric Dimensioning and Tolerancing on engineering drawings.
Question 4: In CNC machining, what does the G-code command 'G00' specify?
- Feed rate for cutting moves
- Rapid traverse positioning (non-cutting movement at maximum machine speed) (Correct answer)
- Circular interpolation clockwise
- Tool change command
Correct answer: Rapid traverse positioning (non-cutting movement at maximum machine speed)
G00 commands the CNC machine to move the tool at maximum rapid speed for positioning, not for cutting material.
Question 5: What is 'design for manufacturability' (DFM) in the context of mechanical CAD?
- Adding manufacturing notes to a drawing title block
- Designing parts with geometries and tolerances that are practical and cost-effective to produce (Correct answer)
- Selecting materials from a manufacturer's catalog
- Generating CNC programs directly from the CAD model
Correct answer: Designing parts with geometries and tolerances that are practical and cost-effective to produce
DFM is the practice of designing parts so that their geometry, tolerances, and features are feasible and economical to manufacture.
Question 6: In a mechanical exploded assembly drawing, what is the purpose of the 'explode lines' (also called witness lines or lead lines)?
- To show weld locations between components
- To visually connect each disassembled part back to its assembly position along the axis of disassembly (Correct answer)
- To indicate the direction of applied forces
- To show where parts are cut in a section view
Correct answer: To visually connect each disassembled part back to its assembly position along the axis of disassembly
Explode lines in an exploded view connect each component to its assembly position, showing how parts come together along their assembly axis.
CAD CAD Specialist Mechanical Design and Manufacturing 3
In parametric mechanical CAD, what is the difference between a 'driven' dimension and a 'driving' dimension?