Why is it Easy for Die Casting Demoulding to Produce Pores?

Die casting is a widely used manufacturing process for producing high-precision metal components in industries such as automotive, aerospace, and electronics. One of the most common quality issues in die casting is the formation of pores (porosity) on the surface or within the structure of the cast part. These pores not only affect mechanical strength but also impact surface finishing, coating adhesion, and product durability.

Among the various factors that cause porosity, the demoulding stage plays a crucial role. Improper release conditions during demoulding can trap gases, disrupt surface flow, and create structural weaknesses. Understanding why pores form during demoulding—and how to minimize them—is essential for manufacturers aiming to improve casting yield and quality.

Why Demoulding Leads to Pores in Die Casting

1. Gas Entrapment During Release
   When molten metal solidifies, trapped gases can expand if the release surface is not optimized. Poor lubrication or insufficient release agents may cause metal to stick, leading to gas pockets and pores.

2. Uneven Cooling and Shrinkage
   During demoulding, uneven mold temperatures can accelerate shrinkage in localized areas, causing micro-voids or shrinkage porosity in the part.

3. Surface Tension and Adhesion
   If the casting adheres strongly to the mold wall, excessive force is required to demould. This mechanical stress can cause surface tearing, which exposes pores or weak areas.

4. Improper Release Agent Selection
   Traditional release oils may not form a uniform layer, resulting in poor coverage and inconsistent release. This increases the risk of surface pores, blowholes, and visible defects.

Technical Solutions to Reduce Porosity in Demoulding

1. Use of Advanced Wax-Based Release Agents

   • Wax release agents form a uniform and stable micro-layer on the mold surface.

   • They provide excellent lubricity, ensuring smooth metal flow and controlled demoulding.

   • By minimizing adhesion and stress, they reduce pore formation and improve surface density.

2. Optimized Mold Temperature Control

   • Maintaining consistent temperature across the mold avoids thermal stress and shrinkage voids.

   • Wax additives enhance thermal stability and can reduce hot spots during release.

3. Improved Venting and Gas Removal

   • Ensuring proper venting channels allows trapped gases to escape before solidification.

   • In combination with effective release coatings, gas-related porosity can be significantly reduced.

4. Fine-Tuning of Process Parameters

   • Proper control of injection speed and pressure ensures complete filling without turbulence.

   • Wax-modified release agents improve metal flow, lowering turbulence-related gas entrapment.

A leading automotive die caster producing engine housings faced recurring issues with surface pores after demoulding. By switching to a wax-based release agent instead of conventional oil-based agents, they achieved:

• 30% reduction in porosity defects

• Improved surface finish, reducing post-machining costs

• Higher production efficiency due to smoother demoulding and reduced sticking

This case highlights how small adjustments in release chemistry can deliver significant improvements in die casting quality.

Die casting porosity is a critical issue that often originates during the demoulding stage. Gas entrapment, uneven cooling, and poor release conditions contribute to pore formation, but these issues can be effectively mitigated by adopting wax-based release agents and optimizing process parameters.

If you are facing challenges with pores in die casting, our specialized wax additives and release solutions can help. Contact our technical team today for expert consultation and sample support to enhance your casting quality and reduce defects.