In sand casting, the gating system is the network of channels that guides molten metal from the ladle into the mold cavity. Like a well-designed highway, it must deliver the right volume of metal at the right speed, without turbulence, erosion, or contamination. At Juize Machinery, we engineer gating systems that fill smoothly, trap impurities, and produce sound castings. As a Gold Verified Supplier on Alibaba, our foundry expertise includes optimizing every element of the gating network.
Components of a Gating System
- Pouring Cup (Basin)
The entry point where molten metal first enters the mold. A properly designed pouring cup:
Maintains a constant head of metal to prevent vortexing
Traps initial slag and dross
Provides easy targeting for the ladle stream
- Sprue (Downsprue)
The vertical channel that carries metal downward into the mold. Tapered design maintains full flow and prevents air aspiration. - Sprue Base / Well
A reservoir at the bottom of the sprue that absorbs the kinetic energy of falling metal, reducing turbulence before the metal enters the runner. - Runner (Cross Gate)
The horizontal channel that distributes metal to multiple gates. Runner design ensures balanced filling across all cavities. - Gates (Ingates)
The final entry points into the mold cavity. Gate location, size, and shape control flow velocity and direction. - Filters and Screens
Optional elements placed in the gating system to trap non-metallic inclusions before they reach the cavity.
Common Gating Defects and Their Causes
| Defect | Root Cause in Gating Design |
| Sand inclusions | High-velocity metal eroding mold surfaces |
| Gas porosity | Aspirated air from non-tapered sprue |
| Cold shuts | Multiple fronts meeting without proper fusion |
| Slag inclusions | No slag trap or poor pouring cup design |
| Misrun / unfilled | Insufficient gating capacity or poor metal distribution |
Our Gating Design Principles
- Streamlined Flow, No Sharp Turns
Abrupt directional changes create turbulence and erosion. We use radiused corners and gradual transitions throughout the runner system. - Bottom Fill Strategy
Metal enters the cavity from below, rising smoothly without splashing or trapping air. This is achieved by placing gates low on the casting. - Pressurized vs. Unpressurized Systems
Pressurized (choked) system: Flow controlled at the gates. Produces backpressure, reducing air aspiration. Common for higher-density alloys.
Unpressurized system: Flow controlled at the sprue or runner. Lower turbulence at gates. Common for aluminum and light alloys.
We select based on alloy and casting requirements.
- Balanced Fill for Multiple Cavities
When producing multiple parts in one mold, runner lengths and gate sizes are adjusted so all cavities fill simultaneously at the same rate. - Slag Traps
An additional runner extension beyond the last gate catches metal that has already passed the cavities, carrying the first (contaminated) metal away.
Simulation and Verification
Before cutting metal, we use simulation software to model:
Fill sequence and flow front progression
Temperature distribution during pouring
Velocity profiles to identify erosion risks
Air entrapment potential
Physical verification includes inspecting spent molds for erosion patterns and sectioning sample castings with X-ray.
Design for Gating
Clients can help by:
Avoiding thin, remote sections that are difficult to feed
Providing adequate flat surfaces for gate attachment and removal
Considering gating removal when specifying surface finish requirements
