Foundry equipment — jolt ramming action A jolt machine compacts moulding sand so that the sand is hardest at the pattern face and gradually less hard towards the back of the mould. Select the correct description of its compaction profile.

Introduction / Context:Compaction method influences the density gradient in green sand moulds, affecting permeability, strength, and surface finish. Jolt, squeeze, and jolt-squeeze machines create distinct density distributions. Understanding these profiles helps prevent defects such as erosion, scabbing, and poor surface finish.

Given Data / Assumptions:

• Mould flask mounted on a jolt table.
• Pattern face located at the bottom (near the pattern plate) during jolting.
• Standard foundry green sand mix.

Concept / Approach:In jolting, the flask is lifted and dropped rapidly. The sand near the pattern face experiences repeated impacts and compacts more densely. As distance from the pattern face increases, the transmitted energy diminishes, producing a density gradient: highest near the pattern, lowest at the back.

Step-by-Step Solution:Consider impact distribution: energy concentrates near the pattern plate.Denser sand at the pattern improves surface replication and reduces erosion.Thus, hardness decreases toward the back, matching the jolt compaction profile.

Verification / Alternative check:Hardness measurements with a mould hardness tester show higher values near the pattern for jolt-rammed moulds; squeeze action alone tends to densify near the squeeze head instead.

Why Other Options Are Wrong:Harder at back (option b) describes squeeze-only behavior; uniform hardness claims (options c and d) are unrealistic without specialized processes; deliberate loosening (option e) is not a standard objective of jolting.

Common Pitfalls:Using the wrong compaction method for deep pockets; excessive jolting causing pattern damage or poor venting.

Final Answer:Ram the sand harder at the pattern face with decreasing hardness towards the back of the mould