From 15% Rejection to 2%: Enhancing Knife Gate Valve Casting Reliability
Overview
A knife gate valve body manufacturer faced issues with shrinkage and core gas defects, which compromised the structural integrity and performance of the castings. These defects resulted in high rejection rates and delayed deliveries.
Background
The knife gate valve body, used in fluid control systems, requires precise casting to ensure durability and leak-free performance. Defects like shrinkage and core gas porosity can lead to operational inefficiencies and increased maintenance costs.
Customer Issue
The customer reported a 15% rejection rate due to shrinkage and core gas porosity detected during post-machining inspections. These issues affected the valve body’s ability to maintain sealing under pressure.
Challenges
The challenge was to address shrinkage and core gas issues without compromising production efficiency. Proper core venting was essential to prevent gas-related defects, and optimizing feeding was critical to minimizing shrinkage during solidification.
Solution Approach
Our team performed thermal simulations to identify areas prone to shrinkage and gas entrapment. The method was refined by optimizing the gating and riser system to ensure proper feeding and avoid shrinkage. Additionally, the core design was modified to include sufficient vents, allowing effective gas escape during casting. Zircon and chromite sand were strategically applied to enhance thermal conductivity in critical areas.
Outcome
The optimized casting process successfully reduced shrinkage and core gas defects, bringing the rejection rate down from 15% to 2%. The knife gate valve bodies met all mechanical and dimensional requirements, ensuring consistent quality and performance.
Conclusion
This case study highlights the importance of proper venting, feeding optimization, and thermal simulation in minimizing shrinkage and core gas defects. These improvements ensured defect-free valve body production, leading to enhanced product reliability and customer satisfaction.
