What are CAM and CNC, and how do they turn a CAD design into a manufactured part?
Computer-aided manufacture (CAM) and CNC machining: how a CAD model drives automated manufacture, with advantages and disadvantages.
A CCEA GCSE Engineering and Manufacturing answer on computer-aided manufacture (CAM) and CNC machining, how a CAD model is used to control automated machines, and the advantages and disadvantages of CAD/CAM.
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What this dot point is asking
CCEA expects you to know what computer-aided manufacture (CAM) and CNC machining are, how a CAD model drives them to make a part, and the advantages and disadvantages of using CAD/CAM. CAM is the manufacturing partner of CAD.
The answer
CAD versus CAM
CNC machining
The full chain is: CAD model to CAM program to CNC machine to finished part.
Advantages of CAD/CAM and CNC
- High accuracy and consistency: every part is identical and made to exact dimensions.
- Repeatability and speed: the machine repeats the job and can run continuously, ideal for batch and mass production.
- Less direct labour and the machine can run unattended.
- Easy changes: a design change in CAD updates the CAM program automatically.
Disadvantages of CAD/CAM and CNC
- High initial cost of the machines and software.
- Skilled staff are needed to program and set up the machines.
- Job losses: automation reduces the need for manual machinists.
- Less economic for one-offs: setup time and cost are only worthwhile over larger quantities.
Worked example: justifying CAM/CNC
Examples in context
- Example 1. A run of metal parts
- Designed in CAD, converted by CAM, then cut on a CNC mill so all parts are identical to within tight tolerances, far more consistent than hand machining.
- Example 2. A laser-cut panel
- A CAD outline drives a CNC laser cutter that cuts the shape precisely and repeatably from sheet, ideal for batches.
- Example 3. Quick design change
- When a dimension changes in CAD, the CAM program regenerates automatically, so the CNC machine makes the updated part with no manual reprogramming.
The pattern is that CAD/CAM/CNC links design straight to automated manufacture, giving accuracy and repeatability at the cost of high investment and the loss of some manual jobs.
Try this
Q1. What does CAM stand for, and what does it do? [2 marks]
- Cue. Computer-aided manufacture; it uses computers to control the machines that make the part.
Q2. Describe the chain from a CAD design to a finished CNC part. [2 marks]
- Cue. CAD model to CAM program (instructions) to CNC machine, which cuts the material automatically to shape.
Q3. Give one disadvantage of CNC machining. [1 mark]
- Cue. High initial cost, skilled programming needed, job losses, or uneconomic for one-offs.
Exam-style practice questions
Practice questions written in the style of CCEA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
CCEA style4 marksExplain the difference between CAD and CAM, and describe how a CAD design becomes a finished part using CNC.Show worked answer →
CAD (computer-aided design) is using software to design the part as a 2D drawing or 3D model. CAM (computer-aided manufacture) is using a computer to control the machines that make the part.
The CAD model is converted (by CAM software) into a set of instructions (a program of coordinates) that a CNC (computer numerical control) machine follows. The CNC machine - for example a CNC mill, lathe or router - then automatically cuts the material to the exact shape, repeating it identically each time.
Markers reward CAD = design, CAM = control of manufacture, and the chain CAD model to CAM/CNC program to automated machining of the part.
CCEA style3 marksGive one advantage and one disadvantage of using CNC machines instead of manual machining.Show worked answer →
One advantage: CNC machines produce parts with high accuracy and consistency, making identical parts repeatedly and able to run continuously (fast for volume work, less labour).
One disadvantage: the high initial cost of the machine and the need for skilled programming/setup; they are also less economic for a single one-off part.
Markers reward one valid advantage (accuracy, repeatability, speed, runs unattended, less labour) and one valid disadvantage (high cost, skilled setup, job losses, costly for one-offs).
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