Casting accuracy — the typical dimensional tolerance achievable with the shell moulding casting process is:

Introduction / Context:
Different casting processes offer different levels of dimensional accuracy and surface finish. Shell moulding uses a thin resin-bonded sand shell formed on heated patterns, giving better precision than green sand and approaching permanent-mould processes for many parts.

Given Data / Assumptions:

• Small to medium-sized castings typical for shell moulding.
• Standard process capabilities without special secondary operations.
• Tolerances expressed as symmetric or unilateral values in millimetres.

Concept / Approach:

Published capability data for shell moulding generally indicate tolerances around ±0.3 mm down to ±0.1–0.2 mm depending on size, making ±0.2 mm a representative average for exam purposes. Options like +0.05 mm are unrealistically tight for typical shell castings, while ±1 mm is more characteristic of conventional sand casting.

Step-by-Step Solution:

Verification / Alternative check:

Vendor datasheets and handbooks list shell moulding accuracy between green sand and investment casting, supporting ±0.2 mm as a reasonable benchmark.

Why Other Options Are Wrong:

+0.05 mm is too tight for typical shell; +0.5 mm and ±1 mm are looser than the known capability of shell moulding.

Common Pitfalls:

Confusing investment casting tolerances with shell moulding; overlooking that unilateral tolerances in options may be distractors.

Final Answer:

±0.2 mm