Die casting clip is a typical surface defect in the die casting process, which seriously affects the appearance quality and structural integrity of castings. It is mainly manifested as obvious delamination or peeling on the casting surface—these defects not only reduce the product’s market competitiveness but may also cause safety hazards in high-precision application scenarios (such as automotive parts or electronic components). To help manufacturers effectively identify, prevent, and solve this problem, this article will systematically analyze the causes of die casting clip and provide practical solutions.
1. What Exactly Is Die Casting Clip? Key Characteristics and Harm
Before exploring solutions, it is essential to clearly understand the nature of die casting clip. This section uses a definition + harm structure to help readers quickly grasp the core of the defect.
1.1 Core Definition
Die casting clip refers to a surface flaw formed when metal materials (especially aluminum alloys) undergo abnormal bonding or separation during the die casting process. Its most obvious feature is that the casting surface appears as a layered structure—when touched or subjected to external force, the surface layer may peel off, exposing the inner metal structure. Unlike small scratches or stains, this defect is not a superficial issue but a sign of internal structural inconsistency.
1.2 Potential Harm
The impact of die casting clip on products goes far beyond appearance:
- Appearance failure: Delamination or peeling makes the casting unable to meet the surface quality requirements, leading to direct scrapping or rework.
- Structural weakness: The layered area becomes a stress concentration point. During use, it may crack or break under load, affecting the product’s service life.
- Production loss: For mass-produced parts, even a small proportion of die casting clip defects can significantly increase production costs (including material waste, rework time, and inspection costs).
2. Root Causes of Die Casting Clip: Three Key Factor Categories
Die casting clip is not caused by a single factor but by the interaction of mold, injection process, and material management. The following table sorts out the specific causes of each category, making it easier for manufacturers to locate problems.
| Factor Category | Specific Causes | Mechanism of Defect Formation |
| Mold-Related Issues | 1. Insufficient mold rigidity2. Excessive gap between sliding/splicing parts3. Local high-temperature zones in the cavity | 1. Mold jitters during metal filling, causing uneven metal flow and layered bonding.2. Gaps exceed the allowable range, and aluminum skin (molten metal residue) is embedded between layers, forming a “sandwich” structure.3. High temperature causes alloy to adhere to the mold surface; when the casting is ejected, the adhered layer is torn, leading to peeling. |
| Injection Process Problems | 1. Punch crawling phenomenon2. Disordered metal flow (due to improper sprue system design) | 1. Poor coordination between the injection punch and pressure chamber results in uneven injection speed—fast and slow flow areas form layered interfaces.2. Metal flows in an incorrect order; the first-filled metal layer solidifies early, and the later-filled metal cannot bond with it, forming delamination. |
| Material & Process Management | 1. Fluctuations in alloy chemical composition2. Unclean parting surfaces (residues of aluminum skin/flash) | 1. Changes in element content (e.g., increased silicon or copper) enhance the alloy’s affinity with the mold, increasing adhesion and peeling risk.2. Residues on the parting surface are pressed into the new casting during mold clamping, becoming a barrier between metal layers. |
3. Targeted Solutions: From Prevention to Resolution
Aiming at the three major factor categories above, this section provides step-by-step solutions—covering mold optimization, process improvement, and material management—to help manufacturers fundamentally reduce the occurrence of die casting clip.
3.1 Mold Optimization: Eliminate Structural Hidden Dangers
Mold is the foundation of die casting. Unreasonable mold design or wear is one of the main causes of die casting clip. The following measures can effectively improve mold performance:
- Enhance mold rigidity: Tighten all mold components (such as guide pillars, bolts, and templates) and add reinforcing ribs to key stress-bearing parts. This reduces mold jitter during high-pressure injection, ensuring stable metal flow.
- Adjust sliding part clearance: Use precision measuring tools (e.g., feeler gauges) to check the gap between sliding/splicing parts. For aluminum alloy die casting, the gap should generally be controlled within 0.05-0.1mm; if it exceeds this range, repair or replace worn parts in time.
- Control cavity temperature: Use CAE simulation software to identify local high-temperature zones in the cavity. For these areas, add point cooling water channels or extend the local spraying time of the release agent to keep the cavity temperature uniform (avoiding overheating-induced adhesion).
3.2 Injection Process Improvement: Ensure Stable Metal Flow
The injection process directly determines the filling state of the metal liquid. Optimizing process parameters can avoid disordered flow and layered bonding:
- Solve punch crawling: First, check whether the punch and pressure chamber are worn (if the inner wall of the pressure chamber is scratched, it should be re-polished). Then, adjust the lubrication of the punch—use high-temperature resistant lubricating oil to ensure smooth movement and uniform injection speed.
- Reconstruct the sprue system: Use the “black oil trace method” to observe the actual metal flow sequence: apply black oil to the mold cavity, conduct a trial injection, and check the oil trace distribution. Based on the results, optimize the position and cross-sectional area of the inner gate to ensure that the metal fills the cavity synchronously (avoiding early solidification of local layers).
- Select suitable release agents: Use special die-casting release agents (not general-purpose lubricants). For aluminum alloys, silicone-based or graphite-based release agents are recommended—they form a thin, uniform protective film between the metal and mold, reducing adhesion without affecting metal bonding.
3.3 Material & Process Management: Avoid Human-Caused Defects
Good material control and daily maintenance can prevent die casting clip caused by operational errors:
- Monitor alloy composition: Use spectral analysis equipment to test the chemical composition of the alloy before melting. Ensure that key elements (such as magnesium in aluminum alloys) are within the process range—fluctuations should not exceed ±0.1% to avoid increasing the alloy’s affinity with the mold.
- Clean the parting surface regularly: After each mold opening, use a high-pressure air gun or non-metallic scraper to remove flash and aluminum skin residues on the parting surface. Do not use hard tools (such as steel scrapers) to avoid scratching the mold surface (which may exacerbate adhesion).
4. Yigu Technology’s Perspective on Die Casting Clip
At Yigu Technology, we believe that solving die casting clip requires a “prevention-first” mindset rather than post-repair. Many manufacturers only focus on reworking defective parts but ignore the root causes—for example, ignoring mold gap wear or irregular release agent replacement. In fact, die casting clip is a “early warning signal” of the production system: it may indicate mold aging, process parameter drift, or inadequate operator training.
We recommend that manufacturers establish a defect traceability system: record the occurrence time, mold number, and process parameters of each die casting clip defect. Through data analysis, find the correlation between defects and factors (e.g., “defects increase when mold temperature exceeds 220°C”). Additionally, conduct regular training for operators—let them recognize the appearance characteristics of die casting clip and master basic adjustment methods (such as adjusting release agent dosage). By combining technical optimization with management upgrading, die casting clip can be controlled at a rate of less than 0.5%.
5. FAQ: Common Questions About Die Casting Clip
Q1: How to distinguish die casting clip from ordinary surface peeling?
Ordinary surface peeling is usually caused by external force (such as collision) and only affects the outermost layer; the peeled part is small and irregular. Die casting clip is a structural defect—its peeling layer is larger, has a regular shape (consistent with the mold cavity), and the inner surface of the peeled layer is smooth (indicating incomplete bonding during casting).
Q2: Will increasing the injection pressure help reduce die casting clip?
Not necessarily. Moderately increasing the injection pressure can improve metal flow uniformity, but excessive pressure (exceeding the mold’s bearing capacity) will increase mold jitter and gap expansion, which may instead exacerbate die casting clip. The key is to match the injection pressure with the mold rigidity—for molds with insufficient rigidity, first strengthen the mold before adjusting the pressure.
Q3: Can die casting clip be repaired after occurrence?
For non-critical parts (such as decorative components), small-area die casting clip can be repaired by welding (using the same alloy material) + grinding. However, for load-bearing parts (such as engine brackets), repaired areas may still have structural hidden dangers, so it is recommended to scrap them directly. The most effective way is to prevent defects during production rather than relying on post-repair.