Commercial Processes For Metals (AQA GCSE Design & Technology): Revision Note
Exam code: 8552
Milling
Milling removes metal using a rotating multi-point cutter while the workpiece is moved accurately beneath it
How does milling work?
The workpiece is clamped in a machine vice or fixture
The correct cutter and speed are selected
The table moves in 3 controlled directions (X, Y and Z) to create slots, steps, pockets and flat faces
A depth stop, digital readout or CNC program controls dimensions
Typical uses
Brackets, machine parts, moulds, slots and precision prototypes
Quality and production
It can achieve close tolerances and high surface quality
Secure clamping and measured depth prevent undersized or oversized features
Worked Example
How can a depth stop improve quality during milling?
[1 mark]
Answer
It limits tool movement to a set depth, helping repeated features reach the same accurate measurement. [1]
Examiner Tips and Tricks
Don't justify a commercial process with words like 'quick' or 'accurate' alone. For milling, name the CNC control specifically: a CNC program repeats the exact same X, Y and Z tool paths on every part in a batch, which is what makes milling suitable for high-volume, close-tolerance commercial production rather than one-off use.
Casting
Casting forms metal by pouring or forcing molten metal into a mould where it cools and solidifies
How does casting work?
A pattern or die creates the required cavity
Metal is heated above its melting point
The molten metal enters the mould through runners and gates
After cooling, the casting is removed, trimmed and finished
Typical uses
Engine parts, handles, housings, cookware and complex components
Quality and production
Casting can make complex shapes with little machining
Shrinkage, air bubbles and incomplete filling must be controlled through good mould design and process settings
Worked Example
Name one defect that quality control may identify in a casting.
[1 mark]
Answer
An air pocket, incomplete fill, crack, excessive flash or incorrect dimension. [1]
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