Nylon CNC Machining Service

Yes, nylon (especially unfilled PA6 or PA66) is generally easy and forgiving to CNC machine compared to many metals or brittle plastics. It has low friction, good toughness, and machines to a smooth surface finish (often Ra 0.8–1.6 µm without extra effort). It produces continuous, stringy chips rather than dust, and sharp tools cut it cleanly.

However, it does have well-known challenges that catch people off guard:

• Heat sensitivity — Low melting point (~220–260°C); excessive heat causes melting, gummy chips, stringy burrs, or tool clogging.
• High toughness/elasticity — Leads to long stringy chips that wrap around tools, plus raised burrs or “fuzz” on edges.
• Moisture absorption (hygroscopic) — Nylon absorbs humidity (PA6 up to ~3%, PA66 ~2–2.5%), causing slight swelling or dimensional changes post-machining.
• Filled grades (e.g., glass-filled) — Much more abrasive → faster tool wear.

Best practices to avoid issues (standard among experienced shops):

• Use sharp HSS or polished carbide tools with high positive rake angles (10–20°).
• High spindle speeds + light cuts/feed rates to minimize heat (e.g., 500–1000 SFM / 150–300 m/min).
• Compressed air or minimum quantity mist coolant (avoid heavy flood coolant unless it’s non-water-based, as water worsens moisture issues).
• Sharp tools + proper chip evacuation prevent most burrs and melting.
• For glass-filled nylon, switch to carbide or PCD tools.

With these adjustments, yield and finish are comparable to ABS or POM in professional shops.

Both PA6 and PA66 are widely machined, but PA66 (Nylon 6/6) is usually the go-to choice for most CNC projects.

Quick comparison of the two most common grades:

Standard achievable tolerances (most shops’ typical quotes):

• General parts: ±0.1 mm to ±0.05 mm
• Tighter: ±0.025 mm to ±0.01 mm
• Very tight (with extra care): ±0.005–0.01 mm possible, but often at higher cost and with strict conditions.

Dimensional stability is the #1 pain point — nylon is not as rock-stable as metals or low-absorbency plastics like Delrin/POM.

Main reasons parts “move” after machining:

1. Moisture absorption — Parts can swell 0.5–2% linearly depending on grade, humidity, and time exposed.
2. Internal stress relief — Especially in extruded or cast stock; roughing removes material → part relaxes and warps slightly.
3. Thermal expansion during cutting — Thin walls or long features distort from localized heat.

How pros handle it:

• Prefer PA66 over PA6 for lower absorption.
• Pre-dry material (80–100°C for 4–12 hours) before machining.
• Rough machine → stress-relieve/age → finish machine.
• Control shop humidity; seal/package parts immediately after machining.
• Advise clients to allow 0.1–0.3% extra stock or design with moisture in mind.
• For ±0.01 mm or better → communicate early; may need special fixturing, environment control, or post-machining stabilization.

Bottom line: Nylon CNC routinely hits ±0.02–0.05 mm reliably. Sub-0.01 mm is doable but requires planning—don’t assume it behaves like metal or acetal without precautions.

If you have a specific part drawing, application (e.g., gears, bushings, prototypes), or tolerance callout, feel free to share more details for tailored advice on grade, design tweaks, or quoting tips!