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Subjects · Leaving Cert Engineering

Leaving Cert Engineering: CNC & CAD/CAM

How often CNC & CAD/CAM comes up on the Engineering papers, every year it was asked, and questions to try.

HL Asked on 9 of the last 9 Higher Level papers, most recently in 2025. banker

OL Asked on 9 of the last 9 Ordinary Level papers, most recently in 2025. banker

June 2028 is the first exam on the new Engineering course. These come from the 2016–2025 papers, so read them as a guide.

CNC & CAD/CAM, Higher Level(6 marks)

Quick ones on CNC & CAD/CAM.

(a)What does G00 command a CNC machine to do?
  1. Linear cutting move at feed rate
  2. Rapid move to a position, not cutting
  3. Clockwise arc
(b)What does M03 do in a CNC part program?
  1. Ends the program
  2. Switches the coolant on
  3. Starts the spindle clockwise
(c)In absolute dimensioning, every position is measured from?
  1. A single fixed datum (program zero)
  2. The tool nose radius (cutter centre)
  3. The previous tool position (last point)
Show the answers

(a) Rapid move to a position, not cutting

(b) Starts the spindle clockwise

(c) A single fixed datum (program zero)

Your turn: Higher Level questions on CNC & CAD/CAM.

Higher Level

Asked on 9 of the last 9 Higher Level papers, most recently in 2025. banker

Every paper, year by year

YearWhere it came up
2025Q1(g), Q8(c)OR
2024Q8(c)OR
2023Q1(j), Q8(c)OR
2022Q8(c)OR
2021Q8(c)OR
2019Q7(c)OR
2018Q7(c)OR
2017Q7(c)OR
2016Q1(e), Q1B, Q7(c)OR

Links open the State Examinations Commission’s paper for that year.

More CNC & CAD/CAM questions

CNC & CAD/CAM, 3 marks

What makes a CNC axis drive closed loop?

  1. The machine guard is closed before the axis moves
  2. The program loops back and repeats itself at the end of each run
  3. Encoder feedback compares actual and commanded position
Show the answer

Encoder feedback compares actual and commanded position

The controller corrects any error the feedback shows. Open-loop stepper systems assume every step happened, so missed steps go unnoticed.

CNC & CAD/CAM, 3 marks

Why is an open-loop stepper drive less reliable than a closed-loop servo drive?

  1. It needs hydraulic oil
  2. Missed steps go undetected
  3. It cannot reverse direction
Show the answer

Missed steps go undetected

Open loop assumes each pulse moved the axis. If the motor stalls or skips under load, nothing notices. A closed loop checks position with an encoder.

CNC & CAD/CAM, 3 marks

Why are tool length and diameter offsets used in CNC?

  1. The program works with tools of different sizes
  2. They speed up the rapid moves between cuts
  3. They set the spindle speed for each tool
Show the answer

The program works with tools of different sizes

Offsets store each tool's real length and radius, so the control adjusts the path. A reground or replacement tool only needs its offset updated.

Ordinary Level

Asked on 9 of the last 9 Ordinary Level papers, most recently in 2025. banker

Every paper, year by year

YearWhere it came up
2025Q1(e), Q6(c)OR
2024Q6(c)OR
2023Q1(h), Q6(c)OR
2022Q1(f), Q6(c)OR
2021Q1(j), Q6(c)OR
2019Q6(c)OR
2018Q1(a), Q1(j), Q6(c)OR
2017Q1(j), Q6(c)OR
2016Q1(f), Q6(c)OR

Links open the State Examinations Commission’s paper for that year.

More CNC & CAD/CAM questions

CNC & CAD/CAM, 2 marks

What does CNC stand for?

  1. Computer Network Cutting
  2. Controlled Numeric Casting
  3. Computer Numerical Control
Show the answer

Computer Numerical Control

A CNC machine follows a program of coordinates and codes to move the tool, so parts come out identical every time. Examples: lathes, mills, routers and laser cutters.

CNC & CAD/CAM, 3 marks

A benefit of CAD over drawing by hand?

  1. It removes the need for dimensions
  2. Designs are quick to edit, copy and share
  3. It needs no computer
Show the answer

Designs are quick to edit, copy and share

CAD drawings can be changed in seconds, stored safely, emailed and shown in 3D. The same file can go straight to a CNC machine or 3D printer (CAD/CAM).

CNC & CAD/CAM, 2 marks

What is CAM?

  1. Using computer-controlled machines to make parts
  2. Drawing and modelling designs on a computer
  3. Checking finished parts with a micrometer
Show the answer

Using computer-controlled machines to make parts

Computer Aided Manufacture takes a design, often straight from CAD, and turns it into tool paths for machines like CNC routers, lathes and laser cutters.

Other Engineering topics

All of Leaving Cert Engineering