Die casting defects vary. Here are some common die casting defects and their possible causes:
There are patterns or traces of metal flow on the surface of casting: This may be because flow channel leading to inlet of casting is too shallow, or injection specific pressure is too high, causing metal flow rate to be too high, causing splashing of molten metal.

 

There are small protrusions on the surface of casting: This may be due to a rough surface or foreign matter on the surface of mold, which prevents molten metal from flowing smoothly during cooling process.
There are cracks or local deformations on the surface of casting: Possible reasons are that ejector rods are unevenly distributed or insufficient in number, resulting in uneven stress; ejector rod fixed plate is deflected during operation, resulting in uneven stress; casting wall is too thin and deforms after shrinkage.
There are pores on the surface of die casting: This may be due to use of too much lubricant, or gas is not completely discharged during die casting process.
There are shrinkage cavities on the surface of casting: This is usually because die casting process is unreasonable and wall thickness changes too much, causing metal to shrink unevenly during cooling process.
Outer contour of casting is not clear, shape cannot be formed, and there is a partial shortage of material: This may be because pressure of die-casting machine is not enough, injection specific pressure is too low, or temperature of molten metal is too low and fluidity is poor.
Casting part is not formed and cavity is not fully filled: reasons may include temperature of die-casting mold being too low, temperature of molten metal being too low, press pressure being too small, molten metal being insufficient, injection speed being too high, and air not being able to be discharged.
Cold separation: refers to phenomenon that metal flows with lower temperature are butted with each other without fusion and gaps appear, which may appear as blackening, accompanied by flow marks or surface bubbles.
Scratches: Refers to scratch marks on the surface of casting due to metal adhesion and too small a slope in mold manufacturing along demoulding direction, and even cracks in severe cases.
In addition, die-casting parts may also have other defects, such as poor fluidity caused by alloy composition that does not meet standards, poor filling and fusion of molten metal in parts, unreasonable gate processes and too long processes. These defects not only affect appearance quality of die castings, but may also affect their performance and safety. Therefore, in production process of die castings, various process parameters and operating procedures need to be strictly controlled to ensure that quality of die castings meets requirements.
To avoid defects in die castings, comprehensive control and management are required from multiple aspects. Here are some key measures:

 

--Choose high-quality aluminum alloy or other alloy raw materials to ensure that their chemical composition meets standard requirements and avoid defects such as poor fluidity or shrinkage caused by raw material problems.
--Strict screening and pretreatment of raw materials to remove impurities and foreign matter to ensure purity of molten metal.

- Optimize mold design to ensure uniform wall thickness, avoid areas that are too thin or too thick, reduce problems such as shrinkage cavities and cracks caused by uneven cooling.
-Improve manufacturing accuracy and surface quality of molds and reduce surface defects of castings caused by mold problems.
- Reasonably arrange cooling water path to ensure uniform mold temperature and avoid casting defects caused by too high or too low mold temperature.

- Strictly control pressure and speed parameters of die-casting machine to ensure that molten metal can flow evenly when filling mold cavity, avoid defects such as air holes and shrinkage cavities.
-Control pouring temperature of the molten metal and mold temperature to avoid problems such as poor fluidity caused by too low temperature and mold sticking caused by too high temperature.
- Reasonably arrange use of exhaust slots and coatings to ensure that gas can be discharged smoothly and prevent defects caused by gas retention.

-Regular maintenance and upkeep of die-casting machines and molds to ensure they are in good working condition and to reduce casting defects caused by equipment problems.
- Strengthen employee training, improve skill level and work responsibility of operators, ensure stability and reliability of die-casting process.

-Establish a complete quality inspection system to conduct comprehensive quality inspections of die-casting parts, promptly discover and deal with potential defects.
-Carry out cause analysis of defective castings to find out root cause of problem, take corresponding measures for improvement and optimization.
In short, avoiding die casting defects requires comprehensive management and control from multiple aspects such as raw materials, mold design, process control, operation and maintenance, and quality inspection. Only by ensuring that every link is effectively controlled can occurrence of defects in die castings be minimized and quality and performance of castings improved.
Some specific improvement measures to improve defects of die castings:
Optimize die-casting process parameters: Through experiments and simulation analysis, determine optimal die-casting temperature, injection pressure, injection speed and other key parameters to reduce product defects and improve production efficiency. At the same time, die-casting cycle time, including filling time, cooling time and ejection time, should be shortened to increase machine's output rate.
Introducing vacuum die-casting technology: Vacuum die-casting technology can reduce pores and oxidized inclusions inside die-casting parts, improve density and mechanical properties of product.
Reasonable selection and use of die-casting additives: such as die-casting coatings, release agents, granulating agents, etc., to improve filling performance, reduce mold sticking and improve surface quality.

 

Mold design and runner system optimization: Design an efficient runner system, including main channels, runner and gates, to achieve smooth flow and rapid filling of molten metal, reduce air entrainment and cold shut. At the same time, layout and diameter of cooling water channels of mold are optimized to ensure uniform cooling of mold during work, reduce thermal stress and deformation.
Take targeted measures for specific defects: For example, for porosity defects, you can add gates and vents in casting design, increase pouring pressure and speed, improve heat dissipation capacity of mold to reduce gas content of alloy. For cold shut-off defects, mold design can be optimized, pouring temperature and pressure can be increased, and fluidity of molten metal can be improved.
In general, improving die-casting defects requires comprehensive consideration and optimization from multiple aspects such as die-casting process, mold design, and use of die-casting additives. At the same time, for defects that have already occurred, specific problems must be analyzed in detail and corresponding repair measures must be taken. During production process, various process parameters also need to be strictly controlled, molds should be inspected and maintained regularly to ensure quality and performance of die castings.
Warm reminder: Above suggestions do not cover all possible die casting defects and solutions. Specific situations may need to be adjusted based on actual production environment and product requirements.