Basic Knowledge in Mold Processing

Critical Determinants for Mold Material Selection

The choice of mold material is  following decisive factors:

1. Forming Process

The method of production dictates the choice between two fundamental types of tool steel:

A) Hot-work tool steel, which withstands the relatively high temperatures involved in die casting, forging, and extrusion.

B) Cold-work tool steel, used for blanking, shearing, cold forming, cold extrusion, cold forging, and powder compacting.

2. Plastic Material

Some plastics, such as PVC (Polyvinyl Chloride), can generate corrosive by-products during processing. Corrosion can also be induced by condensation during prolonged downtime, exposure to corrosive gases, acids, thermal cycling (cooling/heating), water, or storage conditions. In these scenarios, the use of stainless steel or corrosion-resistant grades is recommended.

3. Mold Size

Pre-hardened steels are typically used for large molds due to their stability and reduced risk of distortion during heat treatment. Through-hardening steels are often preferred for smaller molds.

4. Production Life (Number of Cycles)

Long-run molds (> 1,000,000 cycles): Require high-hardness steels, typically in the range of 48–65 HRC.

Medium-run molds (100,000 to 1,000,000 cycles): Commonly use pre-hardened steels, with a hardness of 30–45 HRC.

Short-run molds (<100,000 cycles): Can utilize softer steels, with a hardness in the range of 160–250 HB.

5. Surface Finish Requirements

Excellent surface finish is a priority for many plastic molders. It is important to note that the addition of sulfur to improve machinability often degrades the achievable surface quality. Furthermore, high-sulfur steels tend to have reduced toughness (increased brittleness).

Primary Factors Affecting Material Machinability

Several key factors determine the machinability of a material, with the following being the most critical:

1. Chemical Composition

The chemical composition of the steel is fundamental. Generally, higher alloy content correlates with poorer machinability. An increase in carbon content also reduces machinability.

2. Microstructure & Processing History

The microstructure of the steel, which is a direct result of its processing history (e.g., forged, cast, extruded, rolled, machined), is crucial. Forgings and castings often possess a difficult-to-machine surface skin or scale.

3. Material Hardness

Hardness is a primary factor. The general rule is: the harder the steel, the more difficult it is to machine. Tooling selection is directly governed by workpiece hardness:

High-Speed Steel (HSS): Suitable for materials up to 330-400 HB.

TiN-Coated HSS: Can machine materials up to 45 HRC.

Carbide, Ceramic, Cermet, or Cubic Boron Nitride (CBN): Required for hard materials in the range of 65-70 HRC.

4. Non-Metallic Inclusions

Non-metallic inclusions typically have a detrimental effect on tool life. For example, Al₂O₃ (alumina) is a pure ceramic with highly abrasive properties, which accelerates tool wear.

5. Residual Stresses

Residual stresses within the material can lead to significant machining challenges, such as distortion. It is often recommended to perform a stress-relief operation after rough machining to mitigate these issues.

Core Value Proposition

1. Seamless Integration of Design & Fabrication

We offer a comprehensive range of services, from complex mold development to precision component machining, ensuring the flawless execution of design intent.

2. Global Standards & Delivery 

Leveraging stringent quality control systems inherited from Gree and Daikin, we ensure every mold and machined part meets top-tier international standards for accuracy, durability, and reliability.

3. Technology-Driven Efficiency

By utilizing advanced technologies such as CAE simulation and 5-axis machining, we are committed to optimizing production cycles and total costs, delivering value that exceeds expectations.