Shenzhen Alu Rapid Prototype Precision Co., Ltd.

Designing and fabricating a die-casting mold is a high-stakes engineering process. Because these tools must withstand molten metal temperatures and extreme injection pressures, the precision required is significantly higher than that of plastic injection molds.

Here is the professional workflow for die-casting mold manufacturing, covering design through to post-processing.

1. DFM (Design for Manufacturing)

Before cutting steel, the design must account for the fluid dynamics of molten metal and the thermal contraction during cooling.

• Shrinkage Allowance: Unlike plastics, metal alloys have specific solidification shrinkage rates. Your CAD model must scale the dimensions to accommodate this (typically 0.4%–0.6% for aluminum).

• Draft Angles: Metal does not shrink away from the core as easily as plastic. Proper draft angles (usually 1°–3° depending on depth) are essential to prevent galling.

• Thermal Management: Incorporate conformal cooling channels. Inadequate cooling is the #1 cause of mold failure (heat checking).

• Gating & Overflow: Precise positioning of the gate and overflow wells is critical to manage air entrapment and porosity.

2. Steel Selection

The choice of material dictates the tool's lifespan and maintenance cycle.

3. Machining & Fabrication

The transition from block steel to a precision cavity usually involves four distinct stages:

1. Roughing (CNC Milling): Rapid removal of bulk material. Leave a consistent "stock" (0.2–0.5mm) for finish machining.

2. Stress Relieving: After roughing, heat treat the steel to relieve internal stresses. This prevents warping during the final finishing stages.

3. Finishing (High-Speed CNC): Achieving the final geometry, tight tolerances, and surface finish.

4. EDM (Electrical Discharge Machining): Used for sharp corners, deep ribs, and complex geometries that milling bits cannot access. Use Wire EDM for slide inserts and precision lifters.

4. Heat Treatment

This is the most critical step for die longevity.

• Hardening & Tempering: Typically targeting a hardness of 44–48 HRC for H13 steel.

• Nitriding (Surface Treatment): Applying a gas or plasma nitriding layer (typically 0.1–0.3mm deep) increases surface hardness to 65–70 HRC. This significantly improves wear resistance and reduces the adhesion of molten aluminum to the die surface.

5. Assembly & Fitting

• Polishing: Polish in the direction of metal flow. Avoid cross-polishing, which can create drag points.

• Fit-up: Ensure perfect alignment of the parting lines, slides, and ejector pins. Misalignment under high pressure leads to flash and premature wear.

• Surface Coating: For high-volume production, consider PVD (Physical Vapor Deposition) coatings to further enhance heat resistance and mold release properties.