In sand casting, molten metal shrinks as it solidifies. Without compensation, this contraction creates voids—shrinkage porosity that weakens the component and compromises pressure tightness. The solution? Risers (also called feeders). These reservoirs of molten metal supply the casting as it contracts, ensuring solidification without voids. At Juize Machinery, we design riser systems that deliver sound, dense castings every time. As a Gold Verified Supplier on Alibaba, our foundry expertise includes optimizing riser placement and size for maximum effectiveness.
What Are Risers?
Risers are extra cavities connected to the casting, filled with molten metal during pouring. As the casting shrinks, metal from the riser flows in to fill the space. After solidification, risers are cut off and recycled.
Why Risers Matter
Without adequate risers, castings develop:
Centerline Shrinkage: Voids along thermal centers
Surface Sinks: Depressions where internal voids collapse
Leakers: Pressure-containing castings fail under testing
Types of Risers We Use
Open Risers: Exposed to atmosphere, allowing visual inspection of metal level
Blind Risers: Fully enclosed in the mold, insulated for longer feeding
Side Risers: Attached to the casting edge
Top Risers: Placed directly above heavy sections
Our Riser Design Principles
- Size Calculation
Riser volume must exceed casting shrinkage requirements. We calculate based on alloy shrinkage rate and section modulus. - Placement Strategy
Risers feed the last areas to solidify—typically thick sections and thermal centers. Strategic placement ensures directional solidification toward the riser. - Feeding Distance
Each riser feeds a specific volume. We calculate maximum feeding distance based on section thickness and alloy fluidity. - Riser Enhancement
To extend feeding effectiveness, we use:
Insulating sleeves that slow riser solidification
Exothermic compounds that generate heat, keeping metal liquid longer
Riser necks designed for easy removal without damaging castings
Verification
We confirm riser effectiveness through:
Sample casting sectioning to inspect internal soundness
Radiographic (X-ray) inspection for critical components
Pressure testing for leak-tight requirements
