Die casting is a widely used manufacturing process for producing complex metal parts with high precision. Однако, it is not without challenges. Various defects can occur during the process, affecting the quality, производительность, and cost of the final products. Understanding these common problems and their solutions is crucial for manufacturers to improve production efficiency and product quality. Below is a detailed analysis of the key issues in die casting, along with practical solutions.
1. Key Defects in Die Casting: Обзор
Before delving into specific problems, let’s first look at a summary of the most common die casting defects, their main causes, and core solutions. This table provides a quick reference for identifying and addressing issues.
| Категория дефекта | Main Manifestations | Primary Causes | Core Solutions |
| Stomata and Looseness | Dense shadows in X-ray inspection; exposed pinholes after machining | Trapped air in the cavity (poor exhaust); hydrogen precipitation during solidification | Add serpentine exhaust tanks; use vacuum die-casting; control melting degassing |
| Shrinking Holes and Shrinking Looseness | Concentrated or dispersed shrinkage in thick parts/hot joints | Inadequate replenishment of volume shrinkage during solidification | Extend holding time; increase final pressure; optimize gating system |
| Cracks and Deformations | Thermal cracks in thin-walled parts; distortion of large flat structures | Thermal stress exceeding material strength; uneven cooling contraction | Adjust mold cooling system; increase mold temperature; use arc transitions |
| Mold Sticking and Strain | Rough casting surface; local material shortage; severe mold jamming | High chemical activity of materials (НАПРИМЕР., цинковые сплавы); poor mold surface or failed release agent | Польская полость формы; plate hard chrome; use high-temperature release agents |
| Flash and Burrs | Flake-like excess at mold parting surfaces/movable block gaps | Insufficient clamping force; износ плесени; high injection pressure | Check mold wear; increase clamping force; add sealing grooves |
2. In-Depth Analysis of Major Die Casting Problems
Each defect in die casting has unique characteristics and requires targeted solutions. The following sections break down the most critical problems using a cause-effect-solution структура, ключевые термины выделены для ясности.
2.1 Stomata and Looseness: А “Invisible Killers” of Casting Compactness
Stomata (tiny bubbles) and looseness (dispersed pores) are among the most stubborn defects in die casting. They are often invisible to the naked eye but can significantly reduce the mechanical properties of parts, such as tensile strength and fatigue resistance.
What causes them?
- During high-speed injection, air in the mold cavity is compressed into a high-pressure zone. If the exhaust channel is blocked or too narrow, this air cannot escape and becomes trapped as bubbles in the casting.
- The metal liquid absorbs hydrogen during melting. As the liquid solidifies and cools, the solubility of hydrogen decreases, causing it to precipitate as tiny pores.
How to solve them?
- Install serpentine exhaust tanks в форме: These tanks have a winding design that increases the path for air to escape, ensuring thorough exhaust.
- Усыновить vacuum die-casting technology: This method actively extracts air from the cavity before injection, reducing air trapping by up to 90%.
- Strictly control the degassing process во время плавления: Use inert gas (НАПРИМЕР., аргон) to purge the metal liquid, removing dissolved hydrogen and other gases.
2.2 Shrinkage Defects: Why Thick Parts Fail
Shrinking holes (большой, concentrated gaps) and shrinking looseness (маленький, dispersed gaps) are common in thick sections or “hot joints” (areas where multiple metal flows meet and cool slowly). These defects weaken the part’s structure and can lead to leakage in pressure-bearing components.
A comparative look at shrinkage types:
| Тип | Расположение | Размер | Impact on Performance |
| Shrinking Holes | Thick parts/hot joints | Большой (часто >1мм) | Severe reduction in compactness; may cause structural failure |
| Shrinking Looseness | Same as above | Маленький (обычно <0.5мм) | Gradual loss of mechanical properties; affects long-term durability |
Solutions to prevent shrinkage:
- Extend the время выдержки of the die casting machine: This allows more metal liquid to flow into the cavity and replenish the space left by solidification shrinkage.
- Increase the конечное давление: Higher pressure ensures the metal liquid fills even tiny gaps, reducing the formation of shrinkage.
- Optimize the стробирующая система: Position the inner gate close to the shrinkage-prone areas so the metal liquid can directly feed these regions. Добавлять overflow grooves to collect excess liquid and assist in replenishment.
2.3 Mold Sticking and Strain: A Nightmare for Production Efficiency
Mold sticking occurs when the casting adheres to the mold surface during ejection, leading to scratches, material loss, or even mold damage. This problem is particularly common with цинковые сплавы and other chemically active materials.
What are the warning signs?
- The casting surface becomes rough or has “pull marks” after ejection.
- Local areas of the casting are missing (due to material sticking to the mold).
- In severe cases, the casting gets stuck in the mold, halting production.
How to fix and prevent mold sticking?
- Regularly polish the mold cavity: A smooth mold surface reduces friction between the casting and the mold.
- Plate the mold with hard chrome: This coating increases surface hardness and resistance to adhesion, Продолжая жизнь плесени.
- Switch to high-temperature resistant release agents: Graphite-based or molybdenum disulfide release agents form a protective layer between the casting and mold, preventing sticking.
- Install forced ejection mechanisms in high-risk areas (НАПРИМЕР., deep cavities or complex shapes) to ensure smooth part removal.
3. Comprehensive Prevention Strategies for Die Casting Problems
Solving individual defects is important, but a systematic approach is needed to minimize all issues. Below are four key strategies to build a robust die casting process:
- Preliminary Verification with CAE Simulation
Use Computer-Aided Engineering (CAE) software to simulate the filling and solidification process. This predicts potential defect locations (НАПРИМЕР., air traps, hot joints) before mold production, saving time and cost on revisions.
- Real-Time Process Monitoring
Collect data on injection curves (скорость, давление) и температура формы в реальном времени. Set up control limits for these parameters to ensure the process stays within optimal ranges. Например, if mold temperature drops below a threshold, the system can alert operators to adjust heating.
- Continuous Improvement with FMEA
Conduct Failure Mode and Effects Analysis (FMEA) to review historical defects. Identify root causes (НАПРИМЕР., “mold sticking due to infrequent polishing”) and implement corrective actions. This cycle of analysis and improvement reduces defect recurrence.
- Strict Equipment Management
- Regularly calibrate the injection system of the die casting machine to ensure accurate pressure and speed control.
- Проверить cleanliness of hydraulic oil: Contaminated oil can cause system malfunctions, leading to unstable injection and defects.
4. Yigu Technology’s Perspective on Die Casting Quality
В Yigu Technology, we believe that solving die casting problems requires a balance of technical expertise and practical experience. Many defects, such as stomata and shrinkage, are interrelated—improving exhaust to reduce stomata may require adjusting injection pressure, which could affect flash formation. Thus, manufacturers should not focus on single parameters but optimize the entire process based on product structure и Свойства материала.
We recommend small-batch trials before mass production: Test different process parameters (НАПРИМЕР., температура формы, время выдержки) to find the “сладкое пятно” for each part. Кроме того, инвестиции в обучение операторов имеют ключевое значение: хорошо обученный персонал может обнаружить ранние признаки дефектов (НАПРИМЕР., грубые поверхности, неравномерное охлаждение) и оперативно корректируем процесс. Объединив передовые технологии (как моделирование CAE) с практическим опытом, Производители могут достичь последовательных, высококачественное литье под давлением.
5. Часто задаваемые вопросы: Common Questions About Die Casting Problems
1 квартал: Can vacuum die-casting completely eliminate stomata?
Нет, вакуумное литье под давлением значительно уменьшает количество устьиц (к 80-90%) но не могу их полностью устранить. Остаточный водород в металлической жидкости или небольшие зазоры выхлопных газов могут по-прежнему вызывать образование мелких пор.. Сочетание вакуумной технологии со строгой дегазацией при плавке является наиболее эффективным подходом..
2 квартал: Why do cracks often occur in thin-walled die castings?
Тонкостенные детали остывают быстрее, чем толстостенные., создание больших тепловое напряжение (из-за неравномерного распределения температуры). Когда это напряжение превышает предел прочности материала, трещины образуются. Чтобы предотвратить это, увеличьте температуру формы для замедления охлаждения и используйте дуговые переходы (вместо острых углов) Чтобы уменьшить концентрацию стресса.
Q3: How often should I replace the release agent in die casting?
Частота зависит от типа разделительного агента и объема производства.. Для разделительных агентов на основе графита, заменяйте их каждый 4-6 часы (или после 50-100 цикл) для обеспечения эффективности. Если прилипание плесени происходит чаще, проверьте наличие разделительного агента и скорректируйте график замены.