Die Casting is a versatile process for manufacturing complex and intricate metal parts. Not only it is a highly efficient production technique, but it is also very cost-efficient in the long run. Therefore, various industries such as aerospace, automotive, electronics, etc. industries with a high demand for metal components opt for die casting.
However, like any other manufacturing process, die casting has some challenges as well. One of the main challenges high-pressure die casting manufacturers face is the occurrence of defects in the casting. Critical components (e.g. automobile, aircraft parts, etc.) must be free from any major defects, as it could even result in catastrophic failure.
In this article, we will explore some common defects in HPDC, their causes, and potential solutions.
Common Types of Casting Defects
There are various types of die casting defects which could be internal or superficial defects. These defects could affect the aesthetics and structural performance of a casting. Die-casting defects may be sub-categorized as follows.
1. Surface Defects:
Surface or superficial defects in a die-cast part include a range of imperfections that manifest on the outer layer of the casting. Managing surface defects is essential to ensure the desired level of aesthetics and functionality of a product. Some common surface defects are flash, blisters, drag/ejector marks, soldering, shot lube stains, etc.
2. Internal Defects:
Internal defects are formed within the casting and are much more difficult to identify as they aren’t visible from the outside. Internal casting defects are usually present in the form of pores or voids resulting from entrapped air, thermal shrinkage, or impurities. Common internal defects include porosity, blowholes, cold joints, inclusion, hot tears, cold cracks, etc.
3. Dimensional Defects:
Dimensional defects in casting refer to the deviation of size, shape, or geometry from the intended values. Inaccurate dimensions can compromise the compatibility and performance of a casting. Therefore, careful consideration is needed during design and process control. Shrinkage or warpage due to temperature variation, underfill or overfill are prevalent dimensional defects.
Apart from the aforementioned form of defects, various other defects could be present in castings. Here’s a list of the 22 most common types of die-casting defects.
| 1 | Gas Porosity | 12 | Heat Checking |
| 2 | Blister | 13 | Break Out |
| 3 | Short Fill | 14 | Flash |
| 4 | Shrinkage Porosity | 15 | Shot Lube Stain |
| 5 | Sink | 16 | Cold Shut |
| 6 | Leaker | 17 | Drag Marks |
| 7 | Hot Cracking | 18 | Warpage |
| 8 | Inclusions | 19 | Cold Flakes |
| 9 | Soldering | 20 | Hot Shortness |
| 10 | Scaling | 21 | Ejector Marks |
| 11 | Erosion | 22 | Cold Cracks |
Causes
Die-casting defects may form due to various issues during the design to execution of the process. In order to effectively address the defects, a proper understanding of the main causes behind them is essential. Here are some of the primary causes that lead to defects in die casting.
● Poor Mold Design:
A poorly designed mold is the first and foremost cause most of die casting defects. Factors like part geometry and material flow should be taken into consideration from the design stage. Otherwise, flash defects and warping will be a common occurrence.
● Inaccurate Injection Speed and Pressure:
Inadequate speed and pressure could result in short fill, and cold shuts, while excess pressure can lead to flash defects. Excess injection speed could also lead to higher levels of porosity due to the increased turbulence of molten metal.
● Poor Metal Quality:
The quality of the metal used in casting also plays a crucial in reducing casting defects. There are metal alloys specifically designed for die casting. Any impurities or inconsistent composition in the metal could lead to various defects that compromise the structural integrity.
● Poor Temperature Control:
Proper temperature managementis crucial to ensure that the molten metal fills the cavity and solidifies properly. If timing is incorrect, shrinkage or warpage defects could take place. It could also lead to internal or surface porosity/voids.
● Lack of Venting:
Inadequate provision for vents in the mold could trap gases within the cavity. These could lead to various superficial defects like blistering and porosity.
● Insufficient or Over Lubrication:
Insufficient die lubrication can increase friction between the mold and casting. Thus, resulting in defects like soldering. While using too much lubricant could stain the die-cast part.
Solutions
Now that we know the causes of die-casting defects, the solutions will be easier to comprehend. Here are some die-casting defect solutions you could implement to achieve high-quality castings.
● Improve Mold Design:
The mold-making accounts for a significant portion of the cost involved in a high-pressure die-casting process. So, it would be in your best interest to pay attention to the design of the mold. It could mitigate a substantial type of defect in an HPDC process. Make sure to follow the die casting design guidelines. And, provide sufficient gates, runners, and vents.
● Optimize Injection Parameters:
The right injection parameters vary based on the size and dimension of the casting. The injection speed and pressure should be carefully decided upon based on simulations and testing.
● Temperature Control:
Real-time temperature monitoring can be used to allow sufficient time for cooling and solidification of castings. It can prevent defects like shrinkage and warping.
● Use High-Quality Metal Alloys:
Metal alloys used for casting should be tested on a regular basis to ensure proper composition free from impurities.
● Implement Die Lubrication:
The die should be sufficiently lubricated to ensure easier removal of the casting. But avoid using too much lubricants to prevent shot lube stain.
● Process Monitoring:
Invest in advanced process monitoring and control systems. It can help you identify any deviations in real-time and take necessary actions to minimize defects.
● Quality Control and Testing:
Stringent quality control procedures should be implemented. Regularly test the finished parts to identify any defects early in the production process.
Tired of Casting Defects? Sunrise Metal Can Help!
Die casting is a highly efficient process for the production of metal components. However, dealing with different types of defects could prove to be challenging. Sunrise Metal specializes in die-casting manufacturing. We provide turnkey solutions to ensure high-quality parts and minimize defects in casting.
We strive to deliver personalized solutions to every project in order to overcome the unique challenges associated with it. You can contact us anytime if you would like to discuss your next project with us.