The die casting runner system is the “vascular network” of the die casting process—without a well-designed system, molten metal cannot flow smoothly into the mold cavity, leading to defects like cold shuts, пористость, or undercasting. As the only channel connecting the injection device to the mold cavity, it directly impacts production efficiency, качество частично, and mold lifespan. For manufacturers struggling with high defect rates or slow production, optimizing the runner system is a cost-effective solution. This article breaks down its structure, key design parameters, defect solutions, and industry-specific applications to help you build a reliable runner system.
1. Основное определение & Role of the Die Casting Runner System
Прежде чем углубляться в детали дизайна, очень важно понимать основную функцию направляющей системы и почему это важно. В этом разделе используется определение + основная роль структура, ключевые термины выделены для ясности.
1.1 What Is a Die Casting Runner System?
Система направляющих для литья под давлением представляет собой набор прецизионных каналов в форме, которые транспортируют расплавленный металл из инъекционного устройства (НАПРИМЕР., барокамера) в полость формы. Его суть – сеть двойного назначения.: он проводит как металл (как канал потока) и тепло (контролировать затвердевание), обеспечение того, чтобы металл достигал каждого угла полости в контролируемом режиме, единообразный способ. В отличие от простого “трубы,” each part of the runner system is tailored to specific flow dynamics and material properties.
1.2 Core Roles in Die Casting Production
A well-designed runner system fulfills four non-negotiable roles—without which high-quality casting is impossible:
- Controlled Metal Delivery: Regulates the speed, давление, and temperature of molten metal to avoid turbulence or splashing (which cause porosity).
- Uniform Distribution: For multi-cavity molds or complex single-cavity parts, it distributes metal evenly to all branches—ensuring consistent filling and solidification.
- Defect Prevention: Acts as a “фильтр” to trap oxide inclusions and guide gas out (via connected relief grooves), reducing internal defects.
- Mold Protection: Minimizes wear on the mold cavity by absorbing the initial impact of high-speed molten metal—extending mold life by 20-30%.
2. Hierarchical Structure of the Die Casting Runner System
The runner system is not a single channel but a coordinated assembly of four parts. Each component has a unique function, and their collaboration is key to smooth production. The table below uses a part-by-part breakdown to explain their design, функция, and typical parameters:
| Компонент | Design Features | Основная функция | Typical Parameters (Алюминиевый сплав) |
| Main Channel (Sprue) | – Slight taper (1-3° cone angle)- Smooth inner surface (Ra ≤ 0.8 мкм)- Connected directly to the pressure chamber | Transfers molten metal from the injection punch to the cross runner; facilitates demolding via taper design | – Inlet diameter: ≥70% of pressure chamber diameter (НАПРИМЕР., 21mm for a 30mm pressure chamber)- Длина: ≤150mm (to minimize heat loss) |
| Cross Runner | – Straight or curved (avoiding sharp turns)- Constant cross-sectional area (circular or trapezoidal)- Rounded corners (radius ≥3mm) | Distributes metal horizontally to each inner gate; maintains consistent pressure and speed | – Диаметр: ≈√(casting weight in grams) (НАПРИМЕР., 8mm for a 60g casting)- Pressure loss: ≤5MPa per 100mm length |
| Inner Gate | – Тонкий, sheet-like structure- Positioned at the last-filling area of the cavity- Adjustable thickness | Acts as the “final valve” to control metal flow into the cavity; ensures the cavity fills before the runner solidifies | – Толщина: 0.5-2мм (0.5mm for thin-walled parts, 2mm for large structural parts)- Ширина: 2-5x thickness (to avoid premature solidification) |
| Relief Groove (Overflow) | – Larger volume than the runner- Connected to the end of the cavity or runner- Equipped with exhaust slots | Collects excess molten metal, oxide inclusions, and trapped gas; prevents backflow into the cavity | – Объем: 1.5-2x the volume of the largest runner section- Глубина: ≥1.2x inner gate thickness |
3. Key Design Parameters: Geometrics, Fluid Dynamics, and Material Adaptation
Designing a runner system requires balancing three critical factors: geometric dimensions (to fit the mold), fluid dynamics (to control flow), и свойства материала (to match the alloy). В этом разделе используется factor-by-factor structure with specific data and rules to ensure practicality.
3.1 Geometric Dimension Specifications
Geometric parameters directly affect flow efficiency and demolding. Ниже must-follow rules для алюминия, магний, and copper alloys:
- Main Channel:
- Taper angle: 1° for small molds (<200мм), 3° for large molds (>500mm) (balances demolding and metal flow).
- All adapters (НАПРИМЕР., main channel to cross runner) must have a rounded radius of ≥3mm—sharp corners cause turbulence and oxide formation.
- Cross Runner:
- Для алюминия: Diameter = √(casting weight in grams) (empirical formula verified in 10,000+ trials).
- For magnesium: Diameter = 1.2x aluminum diameter (magnesium has lower viscosity and needs larger channels to avoid excessive speed).
- Для меди: Diameter = 1.5x aluminum diameter (copper cools fast, requiring larger channels to maintain temperature).
- Inner Gate:
- Толщина: Never less than 0.5mm (risk of premature solidification) or more than 2mm (risk of shrinkage).
- Длина: ≤5 мм (short gate reduces pressure loss and ensures the gate solidifies first—preventing backflow).
3.2 Fluid Dynamics Considerations
Fluid dynamics determine how molten metal behaves in the runner system. Two key dimensionless numbers and one pressure parameter must be controlled:
- Reynolds Number (Re): Measures flow turbulence. Maintain Re ≥ 4000—this ensures turbulent flow, which promotes heat exchange and keeps the metal liquid longer. Для алюминия, this translates to an injection speed of 3-5 РС.
- Froud Number (Fr): Measures the risk of splashing. Keep Fr ≤ 1—this prevents the metal from “splashing” against the runner walls (который задерживает воздух). For a cross runner with a 10mm diameter, this means a maximum speed of 4.5 РС.
- Pressure Drop Gradient: Controls pressure consistency. The pressure loss per 100mm of runner length must be ≤5MPa—this ensures the metal reaches the farthest part of the cavity with enough pressure to fill gaps.
3.3 Material Adaptation Principles
Different alloys have unique properties, and the runner system must be adjusted accordingly. The table below highlights material-specific design changes:
| Alloy Type | Runner Design Adjustments | Поверхностная обработка | Ключевые меры предосторожности |
| Алюминиевый сплав (ADC12) | – Standard dimensions (per geometric rules)- Trapezoidal cross runner (better heat retention) | – Polish to Ra 0.8 мкм- Chrome-molybdenum overlay welding (for high-wear areas) | Avoid excessive runner length (>200мм) to prevent heat loss. |
| Магниевый сплав (Az91d) | – Larger cross-sectional area (1.2x aluminum)- Preheating jackets (maintain 200-250°C) | – Электрополирование (Ra ≤ 0.4 мкм)- Anti-oxidation coating (to prevent magnesium-air reaction) | Use nitrogen purge in the runner to reduce oxidation. |
| Copper Alloy (C95400) | – Spiral cross runner (замедляет охлаждение)- Thickened walls (2x aluminum) | – Твердый хромированный покрытие (5-10мкм толщиной)- Heat-resistant ceramic coating | Keep runner length ≤100mm (copper cools too fast beyond this). |
4. Typical Defects in Runner Systems: Causes and Solutions
Even well-designed runner systems can develop defects due to wear, parameter drift, or material changes. В этом разделе используется defect-cause-solution structure to help you troubleshoot quickly:
| Тип дефекта | Основные причины | Step-by-Step Solutions |
| Холодная сепарация | 1. Insufficient runner cross-sectional area (metal cools before filling)2. Низкая температура формы (≤180°C for aluminum)3. Slow injection speed (<2 РС) | 1. Expand runner diameter by 15-20% (НАПРИМЕР., from 8mm to 9.6mm for a 60g casting).2. Increase mold temperature to recommended value +20°C (НАПРИМЕР., 220°C for ADC12).3. Raise injection speed to 3-4 РС (ensure Re ≥ 4000). |
| Пористость (Air Holes) | 1. Плохой выхлоп (blocked relief grooves or no serpentine exhaust slots)2. Turbulent flow (sharp turns in cross runner)3. High moisture in raw materials | 1. Add serpentine exhaust slots (depth 0.1mm, width 5mm) to relief grooves.2. Replace sharp turns with rounded corners (радиус ≥5 мм).3. Dry raw materials at 120-150°C for 4-6 часы (reduce moisture to <0.1%). |
| Erosion Corrosion | 1. Excessive injection speed (>5 РС)2. Soft mold material (СПЧ < 45)3. Oxide inclusions in molten metal | 1. Reduce injection speed to <4 РС (check Fr ≤ 1).2. Rework mold with H13 steel (СПЧ 48-52) or add hard chrome plating.3. Install a ceramic filter in the main channel (50μm pore size) to trap inclusions. |
| Shrinkage in Runner | 1. Short holding time (<5 секунды)2. Small relief groove volume (<1.5x runner volume)3. Неровное охлаждение (hot spots in runner) | 1. Extend holding time to 8-12 секунды (matches aluminum solidification time).2. Increase relief groove volume to 2x runner volume.3. Add cooling water channels (distance 10mm from runner walls) to eliminate hot spots. |
5. Industry-Specific Runner System Designs
Runner systems are not “Один размер-все”—different industries have unique requirements, from miniaturization to high-pressure resistance. Ниже three key industry applications with real-world design examples:
5.1 Автомобильные детали (Алюминиевый сплав)
Automotive die casting (НАПРИМЕР., Двигатели корпуса, battery frames) demands high pressure resistance and uniform filling. Key design features:
- Multi-Layer Composite Runners: For large parts like EV battery frames (weight >5kg), use a 2-layer cross runner system—upper layer for main flow, lower layer for branch distribution—to handle working pressures >20MPa.
- Integrated Relief Grooves: Position relief grooves at 45° angles to the cavity (instead of straight) to better trap gas and inclusions.
- Пример: Tesla’s Giga-casting rear floor uses a 12mm main channel, 10mm cross runners, and 1.5mm inner gates—optimized via CAE simulation to reduce porosity to <1%.
5.2 Потребительская электроника (Zinc/Magnesium Alloy)
Потребительская электроника (НАПРИМЕР., средние рамки телефона, Оболочки для ноутбука) require miniaturization and smooth surfaces. Key design features:
- Miniaturized Fan-Shaped Runners: Для небольших деталей (масса <10глин), use fan-shaped inner gates with a minimum width of 2mm and surface roughness Ra <0.4 мкм (achieved via precision polishing).
- Short Runner Length: Total runner length ≤50mm (reduces heat loss for zinc, which solidifies fast).
- Пример: A smartphone middle frame (zinc alloy ZAMAK 5) uses a 4mm main channel, 3mm cross runner, and 0.8mm inner gate—producing 1000 parts/hour with a 99.5% yield.
5.3 Медицинские устройства (Титановый сплав)
Medical die casting (НАПРИМЕР., Хирургический инструмент ручки) requires biocompatibility and no metal precipitation. Key design features:
- Biocompatible Titanium Runners: Use pure titanium (Оценка 2) for runner components—avoids nickel or chrome precipitation (вреден для тканей человека).
- Полная электрополировка: Все рабочие поверхности электрополированы до Ra. <0.2 мкм — удаляет микропоры, в которых могут размножаться бактерии..
- Самоочищающаяся структура: Добавьте небольшую спираль к крестообразному бегунку. (1 поворот на длину 50 мм) к “царапать” остатков и предотвращения накопления — критически важно для стерильного производства.
6. Yigu Technology’s Perspective on Die Casting Runner Systems
В Yigu Technology, мы считаем, что система бегунов - это “невоспетый герой” литья под давлением — многие производители упускают из виду это, приводящие к предотвратимым дефектам и затратам. Слишком часто, команды сосредотачиваются на полостях пресс-формы или параметрах впрыска, но используют типовые конструкции направляющих, which fail to account for material properties or part geometry.
Мы рекомендуем simulation-first approach: Используйте программное обеспечение CAE (НАПРИМЕР., Moldflow) to simulate runner flow before mold production—this predicts issues like turbulence or uneven filling and cuts trial-and-error time by 50%. For multi-cavity molds, we also advocate “balanced runner design”—adjusting cross-sectional areas of branches to ensure flow differences <5% (achieved via flow meter testing).
For clients with high-volume production, we suggest recycling runner condensate (чистота >99%)—this reduces material costs by 15-20% while maintaining quality. By treating the runner system as a critical part of the production chain (not just a “side component”), manufacturers can significantly improve yield and reduce waste.
7. Часто задаваемые вопросы: Common Questions About Die Casting Runner Systems
1 квартал: How often should I inspect and maintain the runner system?
Для масштабного производства (>5000 частей/день), inspect runner dimensions (диаметр, толщина) каждый 5000 parts—repair if deviation exceeds 0.1mm (НАПРИМЕР., a 8mm runner wearing to 7.9mm). Clean carbon deposits in the runner weekly (use a 3mm nylon brush, not steel, to avoid scratching surfaces). For mold downtime >1 неделя, apply anti-rust oil to runners to prevent corrosion.
2 квартал: Can I reuse runner condensate, and what precautions should I take?
Yes—runner condensate (the solidified metal in the runner after casting) can be reused if processed correctly. Первый, separate runner condensate from scrap (no cavity metal, which may have defects). Затем, re-melt it with 10-15% new alloy ingots (to adjust composition) and degas thoroughly (argon rotary degassing for 10 минуты). Для алюминия, ensure the reused material accounts for ≤30% of the total melt (to avoid impurity buildup).
Q3: How to choose between a circular and trapezoidal cross-sectional runner?
Выбирать circular cross sections Для приложений высокого давления (НАПРИМЕР., Автомобильные детали) —they have uniform strength and minimize pressure loss (20% less than trapezoidal). Выбирать trapezoidal cross sections (top width > bottom width) for easy demolding (особенно для магниевых сплавов, которые легче прилипают к формам) и лучшее сохранение тепла (трапециевидные поверхности имеют 15% больше контакта с плесенью, замедление охлаждения).