In metal extrusion processes (direct and indirect), evaluate the following statements and identify the most accurate one regarding tooling, kinematics, and energy losses. Which statement is correct for industrial extrusion practice?

Introduction / Context:
Extrusion pushes a heated (or cold) billet through a die to produce long products of constant cross-section. Understanding how material flows in direct versus indirect extrusion, how tooling is arranged, and where energy is dissipated (useful deformation vs redundant work and friction) is central to process design and analysis.

Given Data / Assumptions:

• Direct (forward) extrusion: billet moves relative to container; die is stationary at the container exit.
• Indirect (backward) extrusion: die moves into the billet; extrudate flows opposite to ram motion.
• Steady extrusion with measurable ram speed and extrudate exit speed.

Concept / Approach:
In indirect extrusion, the material exits through an orifice in the moving die/ram assembly; to allow the product to pass back through the ram, the ram is designed as a hollow ram. This arrangement eliminates billet–container wall sliding, reducing frictional losses. Other statements mix truths and oversimplifications that do not hold generally across processes or conditions.

Step-by-Step Solution:

Verification / Alternative check:
Process schematics in metal-forming texts consistently show hollow rams for backward (indirect) extrusion to enable product discharge through the ram body.

Why Other Options Are Wrong:

• Same speed as ram: Exit speed differs from ram speed; it depends on extrusion ratio and material flow.
• Redundant work vs die angle: Although die angle influences redundant deformation, it is not the only factor, and the statement as framed is incomplete/misleading for a single “true” choice.
• Relative motion always present: Not in indirect extrusion, where billet remains stationary relative to the container.

Common Pitfalls:
Assuming die angle alone governs energy loss; friction, material strain hardening, and extrusion ratio also contribute significantly.

Final Answer:
Hollow ram is used for indirect extrusion.