Nylon vs Polycarbonate: Which One Should You Choose for Precision Parts?

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You've spent weeks perfecting your 3D model. The tolerances are set, the features are aligned, and you're ready to prototype. Then comes the question that stops every hardware engineer in their tracks: Nylon or polycarbonate? Both are engineering workhorses. Both are readily available from CNC machining services. But choosing the wrong one can mean the difference between a part that performs for years and one that fails in the field.

For precision machined parts, the short answer is: choose polycarbonate if your part needs to survive impacts or be transparent; choose nylon if it needs to withstand high temperatures, constant friction, or chemical exposure. Polycarbonate offers 10x the impact strength of nylon and excellent dimensional stability, while nylon dominates in wear resistance and heat deflection. But the devil is in the details—and in the humidity.

The decision isn't always black and white. In the sections that follow, we'll break down the molecular differences between these two materials, compare their real-world performance across five critical dimensions, and give you a simple three-question decision tree to ensure your next precision part is made from the right material—the first time.

Nylon and Polycarbonate: They Aren't Even the Same "Kind" of Plastic

Before comparing performance, it's essential to understand that nylon and polycarbonate sit in entirely different families of polymers. This fundamental difference drives everything from their machining behavior to their end-use performance.

Nylon (Polyamide - PA) is a semi-crystalline polymer. Think of it like a bag of neatly organized marbles. The molecules are packed tightly in ordered regions, which gives nylon its characteristic strength, chemical resistance, and low friction. Common grades include PA6 and PA66, as well as glass-filled variants like PA66-GF30 for enhanced rigidity.

Polycarbonate (PC) , on the other hand, is an amorphous polymer. Its molecular structure is random and tangled, like a bowl of spaghetti. This lack of crystallinity allows light to pass through

—hence polycarbonate's signature transparency—and gives it its legendary impact strength.

One-Sentence Summary:

Nylon = The Warrior (tough, self-lubricating, heat-resistant)
Polycarbonate = The Transparent Heavyweight (impact-resistant, stable, clear)

When sourcing a polycarbonate block for machining, you're typically getting an amorphous material that machines cleanly with sharp tools and proper cooling, yielding excellent surface finish straight off the machine.

If Your Part Needs to "Survive a Drop," Polycarbonate Is the Only Answer

If there's one specification where polycarbonate doesn't just win—it dominates—it's impact resistance. This is polycarbonate's superpower, and it's not even close.

The Data:

Polycarbonate (PC): Notched impact strength of 80-90 kJ/m²
Nylon (PA6/66): Notched impact strength of 5-6 kJ/m²

That's right—polycarbonate is 10 to 15 times tougher than nylon when it comes to withstanding sudden impacts. This is why safety glasses, riot shields, and bullet-resistant windows are made from polycarbonate, not nylon.

Real-World Application:

A recent client came to us with an outdoor equipment housing. Their initial prototype in nylon failed consistently during drop testing—cracks propagating from corner radii on the second or third drop. We switched to CNC polycarbonate machined from the same 3D model. The result? The housing passed 50 drops without visible damage.

When to Choose Polycarbonate:

Protective enclosures and covers
Inspection windows and sight glasses
Handheld device housings
Any part that will be handled, transported, or accidentally dropped

If you're machining a polycarbonate block for machining in these applications, expect clean cuts, optical clarity (if specified), and a part that can take a beating.

If Your Part Needs "Wear Resistance" or "High Heat," Nylon Is the Right Choice

While polycarbonate wins the impact test, nylon takes the crown for friction, wear, and thermal performance. If your part moves against another surface or sits near a heat source, nylon is likely your material.

Friction and Wear:
Nylon is inherently self-lubricating, with a coefficient of friction as low as 0.25 against steel. This makes it ideal for dynamic applications where parts slide, rotate, or engage repeatedly. Polycarbonate, by contrast, has higher surface friction and can gall or wear quickly under continuous motion.

Heat Deflection:

Nylon 66: Heat deflection temperature (HDT) up to 240°C under load
Polycarbonate: HDT typically 130-140°C

This difference matters. In under-hood automotive applications, industrial machinery, or anywhere near motors or electronics, nylon maintains its strength while polycarbonate begins to soften.

Real-World Application:
An automation client originally specified polycarbonate for a drive gear in a pick-and-place unit. After 500 hours, the gear teeth showed significant wear, leading to positioning errors. Switching to CNC-machined nylon (PA6) extended gear life by over 300% with no additional design changes.

When to Choose Nylon:

Gears, bearings, and cam followers
Wear strips and guide rails
High-temperature environments (engine bays, industrial ovens)
Parts exposed to oils, greases, or solvents

For these applications, specifying a polycarbonate block for machining would be a mistake—nylon's crystalline structure is what delivers the durability required.

Precision-Sensitive? Humidity Changes? Polycarbonate Is More "Stable"

Here's the hidden variable that trips up many engineers: moisture. And this is where polycarbonate has a decisive advantage.

The Hygroscopic Reality:

Nylon 6: Water absorption up to 2.5% by weight
Polycarbonate: Water absorption only 0.2% by weight

Why does this matter? Because when nylon absorbs moisture, it expands. In high-humidity environments (think Southeast Asia assembly plants or outdoor deployment), a nylon part precision-machined to ±0.05mm can swell by 0.3-0.8%—enough to turn a precision fit into an interference fit.

The Seasonal Shift:
Engineers in temperate climates often don't realize that nylon parts behave differently in summer vs. winter. A bearing that spins freely in January might bind in July. A housing that snaps together in Arizona might refuse to close in Florida.

Polycarbonate's Advantage:
With minimal moisture uptake, polycarbonate holds its dimensions across seasons and geographies. If your精密零件 (precision part) requires consistent fit, predictable assembly, or optical alignment, polycarbonate is the safer choice.

Design Compensation:

If you must use nylon in a precision application, consider:

Drying the material before machining (critical!)
Designing for "worst-case" humidity expansion
Specifying low-moisture grades like PA12 (0.2% absorption)

If dimensional stability is non-negotiable: Choose polycarbonate and sleep well

When ordering CNC polycarbonate parts for precision assemblies, you can expect the dimensions you design to be the dimensions you receive—rain or shine.

The Ultimate Decision Tree—3 Questions to Choose Your Material

Still unsure? Here's a simple three-question flow chart to guide your decision. Run your part through these questions, and the right material will emerge.

QUESTION 1: Does the part need to be transparent?

│

├─ YES → Choose POLYCARBONATE (PC)

│ (Optical clarity is unique to PC)

│

└─ NO → QUESTION 2: Will the part experience repeated impacts or drops?

│

├─ YES → Choose POLYCARBONATE (PC)

│ (10x the impact strength of nylon)

│

└─ NO → QUESTION 3: Does the part require wear resistance,

| high heat tolerance, or self-lubrication?

│

├─ YES → Choose NYLON (PA6, PA66, or PA66-GF30)

│ (Superior friction, heat, and chemical resistance)

│

└─ NO → EITHER MATERIAL COULD WORK

Consider these tie-breakers:

• Cost: Similar, but nylon requires drying time

• Surface finish: PC can be optically clear

• Humidity: PC wins if environment varies

• Assembly: PC for snap-fits, nylon for threaded inserts

Final Pro Tip:

If you're still uncertain, send us your drawing. We run DFM (Design for Manufacturing) reviews daily and can recommend the optimal material based on your specific geometry, tolerance stack, and end-use environment. Whether you need a polycarbonate block for machining into a transparent prototype or precision CNC polycarbonate parts for production, we'll help you make the right call—the first time.

Emily

Hi, I'm Emily. With a background in technical writing and years of experience working alongside our shop floor team, I bridge the gap between complex manufacturing processes and the people who need to understand them. I believe that good content in manufacturing isn't about jargon—it's about clarity, honesty, and helping you make better decisions for your projects. When I'm not working with our production team or answering customer questions, you'll probably find me hiking or with my nose in a book. Got a question about your next project? Reach out—I'm here to help.

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