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Common Plastics for CNC Machining: A Guide to Hardness, Strength, and Toughness

模型製作, 模型生產, 治具製作廠商, 模具製作廠商, 測試治具製作, 產品模型製作, 模型製作公司, 塑膠模型製作, 模型 翻模, 公仔模型製作, 公仔生產, 客 製 化模型 公仔, 樹脂公仔製作, 矽膠模具製作, pvc模型製作, 金屬模具製作, 模具製作廠商, 簡易模具製作, 塑膠模具製作流程, 矽膠模具製作, 模具開發流程, 模具設計, 塑膠模具製作流程, 模具加工流程, 汐紫模型, 3d列印代工推薦, 3d列印矽膠模具, 橡膠3d列印, 3d列印翻模, 矽膠 翻模 代 工, 3D 列印 代工 學生, 光固化代印價格, 3d列印模型, 3d列印模型製作, 3d列印公仔, 3d列印圖檔製作, 3d列印廠商, 大型3d列印代工

Common Plastics for CNC Machining: A Guide to Hardness, Strength, and Toughness

Introduction

Mechanical properties are the core indicators that determine whether a plastic part is suitable for its structural role. From a part’s scratch resistance and load-bearing capacity to its impact toughness, all are closely related to parameters such as the material’s hardness and strength. This article will explain the key mechanical properties of commonly used plastics for CNC machining to help you select the most suitable material.

Detailed Explanation of Mechanical Properties of Plastic Materials

  • ABS

This material has a well-balanced overall performance profile, with a medium surface hardness (Shore D 78) and good scratch resistance. Its yield strength is approximately 43 MPa, and its elongation at break is as high as 20-30%, demonstrating excellent toughness. Its IZOD impact strength value is approximately 21 kJ/m², indicating reliable impact and collision resistance, making it suitable for housing parts.

  • PC (Polycarbonate)

PC is known for its exceptional strength and toughness. With a yield strength of up to 60 MPa, it can withstand greater loads than ABS. Its most notable feature is its toughness, with an elongation at break exceeding 100% and an IZOD impact strength of up to 88 kJ/m², making it a top choice for parts requiring high crashworthiness, such as protective covers and durable housings.

  • ABS+PC (Composite Material)

This material combines the strength of PC with the ease of processing of ABS. Its yield strength (59 MPa) is close to that of pure PC, but its impact strength (31 kJ/m²) lies between the two, offering superior strength and crashworthiness compared to ABS.

  • PA6/PA66 (Nylon)

Nylon is a representative material for wear resistance and high strength. Its high surface hardness (Shore D 78-85) and yield strength of 74-83 MPa make it ideal for stress-bearing structural parts such as gears. After humidity conditioning, its elongation at break can reach 50-90%, demonstrating excellent toughness.

  • POM (Plasticized Metal)

POM combines high hardness (Shore D 86) with high strength (65-70 MPa) and good dimensional stability. It has moderate toughness, with an elongation at break of approximately 30-40%, but low impact resistance (5-7 kJ/m²). It is more suitable for wear-resistant parts requiring high precision rather than applications subject to high impact.

  • PMMA (Acrylic)

Acrylic has a high hardness (Rockwell M 100) and good surface scratch resistance. However, it is a relatively brittle material, with an elongation at break of only 4-6% and an IZOD impact strength of only 1-2 kJ/m². Therefore, it is less impact-resistant and should be avoided in structures subject to impact.

  • Glass Fiber Reinforced Plastic (e.g., PA+GF, PC+GF)

Adding glass fiber (GF) to plastic significantly alters its properties. Hardness and yield/flexural strength are significantly increased (for example, PA66 + 30% GF can reach 140 MPa), allowing it to withstand higher loads. However, the trade-off is increased brittleness, with elongation at break dropping sharply to 3-5%, and reduced toughness and impact resistance.

  • PEEK

PEEK is one of the most robust engineering plastics with comprehensive performance. It is not only heat-resistant but also boasts extremely high mechanical strength (100 MPa) and a 20% elongation at break, offering a perfect balance of strength and toughness. While its impact strength (4-6 kJ/m²) is lower than that of PC, it is sufficient for high-performance applications.

Key Terms

  • Hardness: This primarily measures a material’s resistance to scratches and indentations. Common testing standards include Rockwell and Shore. Higher values ​​generally indicate a more scratch-resistant surface.
  • Yield/Flexural Strength: This refers to the maximum stress a material can withstand before permanent deformation or fracture. It is a key indicator of a material’s load-bearing capacity.
  • Elongation at Break: This refers to the percentage increase in length of a material when stretched to fracture. Higher values ​​indicate greater ductility and toughness, making it less susceptible to brittle fracture.
  • IZOD Impact Strength: This measures a material’s ability to absorb impact energy, typically tested using a V-notched specimen. Higher values ​​indicate greater impact resistance (crash resistance).

Conclusion

A comprehensive assessment of hardness, strength, and toughness (elongation at break and impact strength) is key to selecting the right plastic material. For example, for housings that need to withstand impact, high-impact PC should be prioritized. For structural parts that need to bear weight, the yield strength should be considered, and PA or glass fiber reinforced materials may be suitable.