How to Select Mold Base Material Based on Product Material?
2026-05-22 13:53:20
Selecting mold base material (especially for the core and cavity parts that directly contact the product) based on the product material is a key step in balancing cost, performance, and lifespan in mold design. The core principle is: analyze the characteristics of the product material, match the properties of the mold steel, and comprehensively consider production volume and cost. Below is a systematic material selection guide.
I. Step 1: Analyze Key Characteristics of the Product Material
Different plastics or composite materials pose different challenges to the mold. Before selecting material, first clarify which category the product material falls into.
1. General Plastics (e.g., PP, PE, ABS, PS)
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Characteristics: Non-corrosive, low wear on the mold, low processing temperature.
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Mold Requirements: Basic strength, wear resistance, and machinability are sufficient.
2. Engineering Plastics (e.g., POM, PA/Nylon)
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Characteristics: High hardness (e.g., POM) or high shrinkage rate (e.g., PA), requiring higher wear resistance and dimensional stability from the mold.
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Mold Requirements: Better wear resistance to withstand abrasion from hard plastics, and better heat treatment stability to cope with dimensional changes.
3. Plastics Containing Corrosive Components (e.g., PVC, flame-retardant materials)
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Characteristics: During high-temperature processing, corrosive gases (e.g., HCl from PVC) decompose and severely erode the mold cavity.
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Mold Requirements: Must have excellent corrosion resistance (rust prevention ability).
4. High-Wear Plastics (e.g., Glass Fiber/Mineral Reinforced Plastics)
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Characteristics: Added glass fibers or mineral fillers are extremely hard, continuously wearing the mold surface like “sandpaper.”
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Mold Requirements: Must have very high hardness and wear resistance.
5. High-Surface-Quality Plastics (e.g., PC, PMMA/Acrylic)
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Characteristics: Used to produce transparent parts or high-gloss appearance parts, requiring the mold cavity to achieve a mirror finish.
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Mold Requirements: Steel must be high purity, free of impurities and pores, with excellent mirror polishing performance.
II. Step 2: Match the Properties of Mold Steel
After clarifying the challenges of the product material, you can selectively choose steel with corresponding properties. Below are the characteristics and applicable scenarios of the most commonly used mold steels.
| Steel Grade | Core Characteristics | Applicable Product Materials & Scenarios |
|---|---|---|
| P20 | Cost-effective, pre-hardened (HRC 28-32), easy to machine, no heat treatment needed. | General plastics (PP, PE, ABS), low-volume production (e.g., <100,000 shots). |
| 718 (718H) | Upgraded P20, purer material, better polishability and wear resistance, pre-hardened (HRC 33-38). | ABS, PC housings for home appliances, automotive interior parts with surface requirements, medium-volume production. |
| S136 | Corrosion resistance + high mirror finish, stainless steel, high hardness after heat treatment (HRC 48-52), polishable to mirror finish. | PVC, flame-retardant materials, transparent parts (PC, PMMA), medical devices, cosmetic packaging. |
| NAK80 | Pre-hardened mirror steel (HRC 38-42), excellent polishability, can be directly textured, no heat treatment needed. | High-gloss or complex-textured cosmetic cases, display housings, cost-effective for volumes under 500,000 shots. |
| H13 | Heat resistance + wear resistance + high toughness, hot-work die steel, good thermal fatigue resistance, excellent wear resistance. | Glass fiber reinforced plastics (e.g., PA+GF), high-temperature molding materials, and die-casting molds. |
| DC53 | High hardness + high toughness, cold-work die steel, hardness (HRC 60-63) and wear resistance better than D2, less prone to chipping. | Punches with complex shapes prone to chipping, or molds for stamping thick plates and high-strength plates. |
Strategy: Invest in high-performance materials to reduce long-term costs.
For high-gloss parts, choose S136 with heat treatment. For high-wear parts, choose H13 combined with nitriding, which can extend mold life several times. Although initial investment is higher, the mold cost per part becomes lower.
III. Advanced Optimization Strategies
1. Combined Use
You don’t need to use expensive steel for the entire mold base. Use high-performance steel (e.g., H13) for high-wear core and cavity areas, while using ordinary steel (e.g., S50C) for non-forming parts like the mold base frame to optimize cost.
2. Surface Treatment
Applying nitriding or PVD coating (e.g., TiN) to the mold can greatly improve surface hardness, wear resistance, and corrosion resistance. It is a “small investment, big return” efficiency enhancement method.
In summary, mold material selection is a systematic engineering process. Following the steps of “analyze material → match performance → consider production volume” allows you to achieve optimal cost control while meeting product quality and production efficiency. Your needs are our pursuit. Contact us quickly and let our products meet your expectations. SG MOLD looks forward to your order!