Multi-Mull Discharge Door Controls Upgrade
Enhances performance and efficiency by replacing either the original flop gate style door or obsolete Rotork actuated door for improved operation and precision.
Available for the Simpson Multi-Mull
21G Simpson Multi-Mull
REPLACEMENT PART: Engineering RFQ
215G Simpson Multi-Mull
REPLACEMENT PART: Engineering RFQ
22G Simpson Multi-Mull
REPLACEMENT PART: Engineering RFQ
225G Simpson Multi-Mull
REPLACEMENT PART: Engineering RFQ
23G Simpson Multi-Mull
REPLACEMENT PART: Engineering RFQ
Reduce or eliminate the requirement for manual adjustment
- Improvements in both control methodology and mechanical elements
- Accurately and continuously measures the true energy usage at the drive motor
- Accurately determines the energy required to retain a constant mass
The Challenge
The primary design objective of the Simpson Multi-Mull was to enable the preparation of large quantities of tightly controlled molding sand using less energy (horsepower), space and capital than any other muller or mixing system.
Simpson Solution
Variations in sand demand often result from changes in molding line speed, number of active lines, or sand-to-metal ratios. To help medium- to high-volume foundries maintain the benefits of continuous mulling while improving sand control under changing conditions, Simpson redesigned the discharge door and its control logic. The goal of the new system is to minimize manual adjustments while enhancing Multi-Mull performance.
The original double-door and single-leg amperage control system have been replaced with an advanced power-based control method and updated mechanical design. Instead of monitoring a single-phase amperage, the new system measures true energy usage at the drive motor using a power transducer. By tracking amperage, voltage, and phase angle across all three phases, it eliminates fluctuations that once reduced accuracy. The data is processed through a PID control loop, comparing real-time power demand to a setpoint entered via the PLC. This maintains a precise retained sand mass, improves accuracy, reduces door movement and downtime, and stabilizes sand properties.
The redesigned discharge mechanism features a single vertical gate, positioned by an electro-mechanical actuator with a variable frequency drive. This system responds rapidly to control inputs, ensuring consistent retention time without manual intervention and allowing quick rebalancing when production conditions change.
Users reported the opportunity to improve the performance of the Multi-Mull due to the following issues:
Manual adjustments and inconsistent sand control:
Maintaining optimal performance during major changes in sand demand required operators to manually reset the inner discharge door mechanism. This process demanded skilled personnel and caused downtime. When adjustments were skipped, the system’s performance suffered. In cases where the Multi-Mull was set for high capacity but demand was low, frequent starting and stopping led to poor sand consistency and increased maintenance needs.
Limited sensitivity in discharge door design:
The original design—combining a fixed inner door with a floating outer door—lacked the sensitivity to maintain tight control of sand properties during smaller fluctuations in demand. Temporary interruptions, such as pattern changes or shifts in job types (low-to-high sand/metal ratios), caused noticeable variations in sand quality.
Outdated controls and electrical inefficiencies:
Before 2000, most Multi-Mulls used separate compactability control systems with redundant components (panels, PLCs, etc.) and minimal integration with primary process controls. This raised maintenance and training costs while reducing overall performance. Additionally, unbalanced electrical loads and power fluctuations of up to 15% reduced drive motor efficiency. Monitoring only one phase of the three-phase motor failed to detect these variations, resulting in inconsistent retention control and decreased precision under modern foundry conditions.
Conversion Kit
For existing Simpson Multi-Mull installations, the system has been engineered to easily replace the old door. For new installations, the redesigned discharge door system comes standard on all new Simpson Multi-Mulls.
