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Engineering Plastics Guide: Why Nylon (PA) is the Ideal Choice for CNC Machined Parts

Author:

sindhmachining

Looking for high-quality CNC machined Nylon parts? We specialize in PA6, PA66, and Glass-filled Nylon with tight tolerances. Get a fast quote for your custom industrial components today!

What material is nylon?

Nylon was first developed by American chemist Wallace Carothers at DuPont Company in the 1930s and was put into industrial production in the late 1930s, marking a new era in human synthetic fiber industry. According to the different sources of monomers and molecular structures, nylon can be classified into several varieties such as nylon 6, nylon 66, nylon 11, and nylon 12. It is mainly produced through condensation reactions of diacid and diamine, or ring-opening polymerization reactions of amide monomers. In general, nylon has the characteristics of high strength, good wear resistance, resistance to fatigue, resistance to oil and chemical corrosion. However, it has a strong hygroscopicity, and its dimensional stability and electrical properties may change when affected by environmental humidity.

In the world of precision manufacturing, Nylon (Polyamide) has earned its reputation as the "Steel of Plastics." As a versatile engineering thermoplastic, Nylon is frequently used to replace metal components in demanding environments. But what makes it so special for CNC machining? This Metal to Plastic conversion guide explores the properties, benefits, and common applications of Nylon.

What Makes Nylon (PA) Unique?

Nylon is a high-performance polymer known for its exceptional mechanical properties. The most common grades used in CNC machining are Nylon 6 and Nylon 6/6.

High Strength: Excellent tensile and compressive strength.
Wear Resistance: Low coefficient of friction makes it ideal for moving parts.
Chemical Resistance: Stands up well against oils, fuels, and many chemicals.

Indicator	PA6	PA66	Description
Chemistry Formula	C6H13NO	C36H66N6O6
Density	0.9±0.1 g/cm³	1.09 g/cm³	Belongs to lightweight engineering plastics
Boil	255.0±0.0 °C at 760 mmHg	452.1ºC at 760 mmHg	for reference only
Fusing Point	220ºC	250-260ºC	The melting point increases as the crystallinity increases.
Flash Point	102.2±18.4 °C	227.2ºC	for reference only
Solubleness	It dissolves in formic acid, phenol, meta-cresol, concentrated sulfuric acid, dimethylformamide, etc., but does not dissolve in ethanol, ether, acetone, ethyl acetate, and hydrocarbons.	Soluble acetic acid and phenolic compounds
Tensile Strength	60–75 MPa	70–85 MPa	PA66 is of a higher grade.
Bending Strength	80–100 MPa	100–120 MPa	Used for load-bearing structural components
Impact Strength	80–100 kJ/m²	90–120 kJ/m²	Demonstrate excellent resilience
Absorption Rate (Saturated)	7–9 %	3–4 %	PA6 has a stronger moisture absorption property, which affects the dimensional stability.
Thermal Decomposition	>300 ℃	>350 ℃	Better stability even at temperatures above the operating temperature.

Nylon 6 (PA6) VS Nylon 66 (PA66)

Key Benefits of CNC Machined Nylon Parts

Lightweighting: Nylon is significantly lighter than most metals (about 1/7th the weight of steel), making it perfect for aerospace and automotive applications to improve fuel efficiency.
Self-Lubrication: Unlike metal gears that require constant oiling, Nylon’s natural lubricity reduces maintenance and noise.
Impact Absorption: Nylon has the unique ability to absorb vibrations and shocks without cracking, protecting the entire mechanical system.
Cost-Effectiveness: It is generally more affordable than high-end alloys and requires less energy to machine.

Other Classifications of Nylon Materials

High Performance / Modified: Overcame the shortcomings of ordinary nylon

Glass-Filled Nylon - PA66 GF30: Add approximately 30% of glass fibers

Advantages: Significantly improves rigidity, strength and dimensional stability, and greatly reduces water absorption rate.
Applications: Surrounding parts of automotive engines, structural support components.

MoS₂ Filled Nylon:

Advantages: This type of nylon is usually grayish-black and has extremely strong self-lubricating properties. Its wear resistance lasts much longer than that of ordinary nylon.
Applications: Bushings and pulleys that require high-speed operation and cannot be frequently lubricated.

Cast Nylon / MC Nylon：

Advantages: Typically used for manufacturing large-sized parts, with less internal stress and excellent toughness.
Applications: Crane pulleys, large industrial rollers.

Nylon 11 / Nylon 12 (PA11 / PA12)：

Core advantage: Extremely low water absorption rate. Ordinary nylon will expand and deform when absorbing water, but PA12 can maintain its size stability in a humid environment.
Applications: Precision parts for outdoor use, underwater equipment, aviation fuel systems.

Looking for cost-effectiveness?	Choose PA6
Want to be wear-resistant and make gears?	Choose PA66.
Afraid of deformation due to moisture?	Choose PA12 or Glass-Filled Nylon
Heavy-duty moving parts?	Choose MoS₂ Filled Nylon

Why Your Nylon Parts Don't Meet Tolerance? (Inside Our QC Secrets)

Although nylon is easy to cut, it has a high thermal expansion coefficient and is prone to absorbing water. To ensure precise tolerances, we recommend following the process guidelines:

1. Tool Selection: Pursuing "ultimate sharpness"

Technique: Use a dedicated aluminum cutting tool or a single-edge milling cutter with a positive rake angle. Nylon melts easily at high temperatures, and a sharp cutting edge can reduce friction and heat generation.
Key point: The tool must be polished to ensure smooth chip removal and prevent molten nylon from adhering to the blade.

2. Heat Control: Cooling is the Key to Success/Failure

Technique: Nylon has poor heat conductivity, and the heat will accumulate rapidly in the cutting area, causing the workpiece to deform.
Key point: During processing, continuous spraying of coolant or compressed air must be maintained. If the precision requirements are extremely high, it is recommended to perform rough machining first, let it cool naturally, and then proceed with fine machining.

3. Stress Relief: Preventing Deformation after Processing

Technique: For thick-walled or complex nylon parts, "curving" often occurs after processing.
Key point: Before processing or after rough processing, the material should undergo annealing treatment (heating to a specific temperature and then cooling) to release internal stress. This is crucial for ensuring the dimensional stability of materials such as PA66.

4. Clamping Force Management: Gentle Power

Technique: Nylon is softer than metal. Excessive clamping force can cause the workpiece to undergo elastic deformation.
Key point: Use soft jaws or evenly distributed fixtures to avoid leaving marks on the surface of the part and ensure that the size does not rebound after releasing the fixture.

5. Humidity control: Size Determined by the Environment

Technique: Considering the water absorption property of nylon, the material should be stored in a dry environment before and after precision processing.
Key point: If the parts will be used in a humid environment, appropriate tolerance compensation should be reserved during the processing.

What is nylon properties?
Nylon (PA) is a high-performance engineering plastic with excellent comprehensive properties. It features high strength, toughness and impact resistance, along with good wear resistance and self-lubrication. Lightweight and corrosion-resistant to oil, chemicals and mild acids/alkalis, it also has good machinability, dimensional stability and electrical insulation, widely used in mechanical and electrical components.
What is nylon used for?
Nylon is a highly versatile material used in many industries: automotive (gears, bearings, fuel lines) for its strength and heat resistance; consumer goods (ropes, zippers) for tensile strength and flexibility; industrial manufacturing (rollers, machine parts) for toughness and chemical resistance; electronics (connectors, insulators) for insulation; and aerospace (fasteners, structural parts) for lightweight and high tensile strength.
What p ost-treatment techniques are commonly used for nylon?
Several post-processing techniques are used to improve nylon parts’ properties: annealing relieves internal stresses to enhance dimensional stability and mechanical properties; surface treatments (plasma, chemical, vapor smoothing) boost adhesion; machining (CNC milling, turning) ensures precise dimensions; dyeing/coloring achieves desired aesthetics and UV protection.

CNC Machining Nylon FAQs

Custom nylon parts

We offer CNC machining and 3D printing services for nylon components. Simply upload your CNC file, and we will provide you with detailed pricing, lead times, You can also read more about choosing the right materials for your application and our guide to plastics.