Product geometry from extrusion — what sections are typically produced? The metal extrusion process is most commonly used to produce which type of cross-sections?

Introduction / Context:
Designers choose extrusion when they need long products with steady cross-sections such as bars, tubes, channels, and complex profiles. Recognising the geometric capability of extrusion is crucial in material-process selection.

Given Data / Assumptions:

• Process: hot or cold extrusion through a die of fixed profile.
• Billet flows plastically; volume conservation holds.
• Hollows are possible using mandrels/bridge dies.

Concept / Approach:
Because the die opening is constant, the exiting metal has a constant cross-section. Both solid and hollow shapes are feasible: solids use a single-orifice die; hollows use mandrel-supported dies (porthole/bridge dies) or piercing elements. Sections that vary along the length are not typical without secondary operations.

Step-by-Step Solution:
Match process physics (steady die opening) to product geometry (constant profile).Account for internal cavities: mandrel/porthole dies form hollows.Therefore, the correct choice is uniform solid and hollow sections.

Verification / Alternative check:
Common products: aluminium window frames (hollow), heat sinks (solid fins), tubing (hollow), bus bars (solid).Process textbooks consistently classify extrusion as a constant-section process.

Why Other Options Are Wrong:
Limiting to only solids or only hollows ignores die/mandrel combinations.

Non-uniform sections require additional forming or variable-die processes, not conventional extrusion.

Thin sheet is made by rolling, not by extrusion.

Common Pitfalls:
Overlooking weld seam lines in porthole-die hollows; underestimating die bearing length effects on dimensional accuracy; ignoring extrusion ratio limits and press force capacity.

Final Answer:
Uniform solid and hollow sections of constant cross-section