Moulding machines — achieving harder sand at the back and softer at the pattern face Which machine is used when the foundry requirement is to compact the sand harder at the back of the mould and relatively softer near the pattern face?

Introduction / Context:
Quality of a sand mould depends on how uniformly the sand is compacted. Different machines produce different density gradients within the mould, affecting surface finish, permeability, and dimensional accuracy.

Given Data / Assumptions:

• Flask with pattern mounted on one face.
• Desired result: sand is harder at the back (top side during compaction) and softer near the pattern face.
• Typical foundry equipment: jolt, squeeze, jolt-squeeze, sand slinger.

Concept / Approach:
A squeezing machine applies pressure from the top platen. Pressure is highest near the top surface and reduces with depth, creating a density gradient with harder sand at the back of the mould and comparatively softer sand at the pattern face. In contrast, a pure jolt compacts more strongly near the pattern as sand settles and densifies around it; sand slingers tend to compact uniformly but are oriented to large moulds and different use-cases.

Step-by-Step Solution:
Match required gradient (harder at back) to compaction method.Squeeze loading from the top generates higher density near the back.Therefore, choose a squeezing machine.

Verification / Alternative check:
Foundry texts describe jolt for densifying near patterns and squeeze for densifying near the top platen. Jolt-squeeze combines both to improve uniformity when needed.

Why Other Options Are Wrong:

• Sand slinger: produces different compaction characteristics and is suited to large moulds.
• Jolt machine: tends to densify sand closer to the pattern face, opposite of the requirement.
• Stripper plate machine: a pattern withdrawal aid, not a compaction method to achieve this gradient.

Common Pitfalls:
Assuming “harder near pattern” is always desirable; for venting and draw, a controlled gradient can be advantageous.

Final Answer:
squeezing machine