Thin-wall aluminum die casting parts present one of the most demanding challenges in HPDC production — and nowhere is that challenge more acute than in the die casting mold cooling system. When wall thickness varies significantly across a single part, a uniform cooling approach will always fail: cool one zone correctly and you over-cool another, or under-cool a third. This is exactly the problem Raidy Mold’s engineering team encountered — and solved — in a gear chamber production program.
After redesigning the die casting mold cooling system with PLC-controlled intermittent water supply, cycle time dropped from 109s to 86s, scrap rate decreased by 50%, and the mold temperature controller was eliminated entirely. Here’s how we did it.
Case Overview
This case study documents a die casting mold cooling system optimization project for a gear chamber component — a thin-wall aluminum HPDC part with highly uneven wall thickness and complex internal geometry including oil channels. The project required resolving multiple simultaneous quality defects that conventional cooling approaches had failed to address.
The Challenge: A Cooling System That Couldn’t Win
The gear chamber presented an inherently difficult thermal management problem. With an average wall thickness of just 2.3 mm and severe variation in thickness across the part — including thick oil channel sections alongside very thin structural walls — no single cooling approach could satisfy all zones simultaneously.
During both prototype trials and early mass production, two distinct and contradictory defect patterns emerged depending on how the cooling circuits were operated:
Problem A — All Cooling ON：Over-Cooling: Cold Shuts & Blackening
With all five cooling water circuits fully open, the mold cooled too aggressively. At the last-fill areas (water end positions) of the thin walls, the metal solidified prematurely — resulting in cold shuts, surface blackening, and poor surface quality. The thin sections simply couldn’t maintain sufficient metal temperature to fill completely before solidifying.
Problem B — Cooling Reduced/OFF：Under-Cooling: Burning, Aluminum Sticking & Deformation
When cooling circuits were partially or fully closed to address Problem A, the thick oil channel sections of the part overheated. This caused aluminum to solder (stick) to the cavity surface, significant part deformation, and surface damage to the oil channel areas from aluminum adhesion — leading to air leakage in the finished component.
The core conflict: The thin wall areas required less cooling to prevent cold shuts. The thick oil channel areas required more cooling to prevent burning and aluminum sticking. A single cooling state — either fully on or partially off — could not satisfy both requirements at the same time.
Root Cause Analysis
Raidy Mold’s engineering team approached the problem by analyzing the relationship between three factors simultaneously:
Mold Cooling Water Channel Structure
The five cooling circuit groups served different mold zones — fixed half (larger cooling assembly and sleeve) and movable half (larger cooling assembly, S4 top core, and spreader). Each zone had different thermal loads due to the part’s wall thickness variation. A uniform control approach treated all zones identically, which was the fundamental design limitation.
Mold Surface Temperature Distribution
Thermal mapping of the mold surface confirmed significant temperature variation between zones during production. Thin-wall areas were dropping below the optimal 150°C–200°C range when all cooling was active, while thick oil channel sections were exceeding 250°C when cooling was reduced — both outside the acceptable window for aluminum HPDC.
Part Quality vs. Cooling State Correlation
By mapping defect locations against the cooling circuit layout and mold temperature data, the team confirmed that the defects were directly caused by the inability of a static cooling state to manage the thermal requirements of different part zones within a single shot cycle. The solution had to be dynamic — not static.
Conclusion from analysis: The problem could not be solved by adjusting a single cooling parameter. It required a dynamic, zone-specific die casting mold cooling system — one that could apply different cooling states to different circuit groups at different points within each shot cycle.
The Solution: PLC-Controlled Intermittent Water Supply
Based on the three-factor analysis, Raidy Mold’s team designed and implemented an intermittent water supply control system — replacing manual cooling management with a PLC-controlled approach that independently manages each of the five cooling circuit groups throughout the shot cycle.
Rather than applying cooling continuously or adjusting it manually between runs, the PLC system opens and closes individual water supply circuits at precisely defined points within each 86-second shot cycle. This allows each zone of the mold to receive the exact amount of cooling it needs — when it needs it — based on the thermal requirements of the part geometry in that zone.
Why Intermittent Supply Works Where Continuous Supply Fails
In a conventional continuous cooling setup, water flows through all circuits throughout the entire cycle. The only control variable is flow rate. For a part with uniform wall thickness, this works well. For a part like the gear chamber — with extreme wall thickness variation — it creates the contradictory defect pattern described above.
Intermittent supply adds a second control variable: timing. By controlling when each circuit is active within the cycle, the system can allow thick sections to cool aggressively during the solidification phase while preventing over-cooling of thin sections during fill. The result is a mold temperature profile that matches the part’s actual thermal requirements — zone by zone, moment by moment.
Cooling System Parameters After Optimization
The following table documents the final cooling configuration for each of the five circuit groups, based on the intermittent water supply solution:
| Circuit Group | Location | Cooling Position | Injection Signal Delay | Water Supply Duration | Water During Spraying? |
|---|---|---|---|---|---|
| Fixed 1 | Fixed Half | Larger cooling assembly | 0s | 35s | None |
| Fixed 2 | Fixed Half | Sleeve | — | Long-term cooling | Yes |
| Movable 1 | Movable Half | Larger cooling assembly | 0s | 35s | None |
| Movable 2 | Movable Half | S4 top core | 2s | 20s | None |
| Movable 3 | Movable Half | Spreader | — | Long-term cooling | Yes |
Key design decisions in the final configuration: Fixed 2 and Movable 3 circuits — which serve zones requiring sustained thermal management (the sleeve and spreader) — run continuously, including during the release agent spray phase. The remaining three circuits operate intermittently, with precisely timed delays and durations that prevent over-cooling of thin-wall areas while ensuring adequate solidification in thicker sections.
Results: Three Measurable Improvements
Following implementation of the PLC-controlled intermittent die casting mold cooling system, the gear chamber program achieved the following results:
Beyond the quantitative results, the intermittent cooling solution eliminated the specific defects that had been recurring throughout the trial and early production phases: cold shuts and blackening in thin-wall areas, aluminum sticking and burning at oil channel sections, part deformation, and air leakage caused by surface damage. All quality issues were resolved within the same production setup.
Additional benefit: Through verified intermittent water supply operation, the mold temperature reached a stable, self-regulating thermal equilibrium — eliminating the need for a separate mold temperature controller unit in subsequent production. This reduced equipment cost and simplified the production setup.
Key Takeaways for Die Casting Mold Cooling System Design
This case demonstrates several principles that apply broadly to die casting mold cooling system design — particularly for thin-wall or geometrically complex aluminum HPDC parts:
1. Uniform Cooling Is Not Always the Right Approach
For parts with significant wall thickness variation, applying the same cooling state to all zones will always create a compromise — satisfying some areas while causing defects in others. Zone-specific cooling design, with independent control of each circuit group, is essential for parts where thermal requirements vary across the cavity.
2. Timing Is as Important as Flow Rate
Conventional cooling system design focuses primarily on flow rate and channel geometry. This case shows that when cooling is applied within the shot cycle can be as important as how much cooling is applied. Intermittent control adds the timing dimension that continuous systems lack.
3. Root Cause Analysis Must Precede Solution Design
The team’s decision to analyze mold structure, surface temperature, and part quality together — before proposing a solution — was what identified the true cause of the contradictory defect pattern. A supplier who had simply adjusted process parameters would have continued cycling between the two defect modes without resolving either.
4. PLC Control Delivers Consistency That Manual Adjustment Cannot
Manual cooling adjustments between shifts or operators introduce variability that undermines production consistency. Replacing manual control with PLC automation ensures that the same cooling profile is applied identically on every shot — which is what allows the mold temperature to stabilize and the quality improvements to be sustained in mass production.
About Raidy Mold
Raidy Mold is an aluminum high pressure die casting mold manufacturer with full in-house capability across mold design, mold making, and production support. The gear chamber cooling system case described in this article is representative of the engineering approach we bring to every complex project — starting with a rigorous root cause analysis, and designing a solution that addresses the actual problem rather than its symptoms.
What Makes Raidy Mold Different
We don’t just build molds — we solve production problems. From thermal simulation at the design stage to PLC-controlled cooling optimization in production, our engineering team brings the same analytical approach to every project.
Frequently Asked Questions
What is a die casting mold cooling system?
A die casting mold cooling system controls the temperature of the mold cavity during production by circulating water through internal channels. Proper cooling ensures consistent solidification, reduces cycle time, and prevents defects such as shrinkage, cold shuts, and aluminum soldering.
Why does thin-wall die casting make mold cooling more difficult?
Thin-wall parts have uneven wall thickness, which means different sections of the cavity cool at different rates. If cooling is applied uniformly, thicker sections may overheat while thinner sections over-cool — causing cold shuts, deformation, and burning simultaneously in the same part.
What is intermittent water supply in a die casting mold cooling system?
Intermittent water supply uses a PLC-controlled system to open and close individual cooling circuits at specific points in the shot cycle, rather than supplying water continuously. This allows precise thermal management of different mold zones — preventing both over-cooling and under-cooling within the same mold.
How much can an optimized cooling system reduce die casting cycle time?
In the gear chamber case documented here, optimizing the die casting mold cooling system reduced the single-part cycle time from 109 seconds to 86 seconds — a reduction of approximately 21%. Results vary by part geometry and alloy, but cooling optimization is consistently one of the highest-impact levers for cycle time reduction.
How does Raidy Mold approach cooling system design for complex parts?
Raidy Mold designs cooling systems as an integral part of the mold design process — not an afterthought. For complex or thin-wall parts, we use thermal simulation to map cavity temperature distribution before any steel is cut, and design zoned cooling circuits that can be independently controlled for precise thermal management throughout the shot cycle.
