The Complete Guide to 3D Printer Filament: What It Is, Types, and How It is Made

If a 3D printer is the engine, filament is the fuel. Without it, your machine is just a robot waving a hot nozzle in the air. But what exactly is this colorful plastic wire, how is it created, and which type should you use for your next automotive project?

Here is everything you will ever need to know about 3D printing filament.

What is 3D Printer Filament?

In Fused Deposition Modeling (FDM) 3D printing, filament is a continuous thread of thermoplastic material. "Thermoplastic" means the plastic melts when heated and solidifies when cooled, over and over again without significantly changing its chemical structure.

Most desktop 3D printers use filament that is exactly 1.75mm in diameter, though some older or industrial machines use 2.85mm.

How is Filament Manufactured?

Have you ever wondered how those perfectly wound spools of plastic are actually made? It is a fascinating industrial process.

1. Raw Pellets: It starts as raw plastic resin pellets (which look like tiny beads). If the filament is going to be colored, colored masterbatch pellets are mixed in with the clear/white raw plastic.
2. Dehumidification: The pellets are baked in massive industrial dryers. Any moisture left in the raw plastic will ruin the final filament.
3. Melt Extrusion: A massive auger screw forces the dry pellets through a highly heated metal barrel. The plastic melts into a thick liquid.
4. The Die: The liquid plastic is pushed through a tiny hole (a die) that shapes it into a 1.75mm string.
5. Cooling Baths: The hot string is immediately pulled through a series of long water baths (warm water first, then cold). This perfectly solidifies the plastic while maintaining its round shape.
6. Laser Measuring: Industrial lasers measure the filament 1,000 times per second. If the diameter jumps to 1.80mm or drops to 1.70mm, the motors adjust instantly to pull it perfectly back to 1.75mm.
7. Spooling: Finally, the perfectly cooled string is wound onto cardboard or plastic spools and vacuum-sealed with a desiccant pack.

The Ultimate Filament Types

Not all plastics are created equal. Choosing the right material dictates whether your part will survive the summer heat inside a car or melt into a puddle.

1. PLA (Polylactic Acid)

• What it is: A biodegradable plastic made from corn starch or sugarcane.
• Pros: Easiest to print, smells like sweet syrup when printing, zero warping.
• Cons: Melts very easily (around 60°C).
• Automotive Use: Do NOT use in cars. A PLA dashboard piece will literally melt in the summer sun.

2. PETG (Polyethylene Terephthalate Glycol)

• What it is: The same plastic used in water bottles, but modified with Glycol to make it easier to 3D print.
• Pros: Excellent chemical resistance, waterproof, decent heat resistance (80°C).
• Cons: Very stringy, loves to stick to the nozzle.
• Automotive Use: Excellent. Great for interior parts, cup holders, and clips.

3. ABS & ASA

• What it is: The plastic used in Lego bricks and real car bumpers. ASA is the UV-resistant brother of ABS.
• Pros: Extremely strong, impact-resistant, high heat resistance (100°C+). ASA will never yellow in the sun.
• Cons: Emits toxic fumes when printing. Requires a heated enclosure because it warps massively.
• Automotive Use: The Gold Standard. Use ASA for all exterior car parts, grilles, and heavy-duty interior brackets.

4. TPU (Flexible Rubber)

• What it is: Thermoplastic Polyurethane. It behaves exactly like rubber.
• Pros: Bendable, squishy, unbreakable.
• Cons: Hard to print fast.
• Automotive Use: Perfect for custom gaskets, intake hoses, and vibration-dampening mounts.

5. Carbon Fiber Blends (PA-CF, PETG-CF)

• What it is: Standard plastics injected with microscopic strands of chopped Carbon Fiber.
• Pros: Incredible rigidity, stunning matte surface finish, hides layer lines completely.
• Cons: Abrasive. It will literally destroy a standard brass nozzle in 24 hours. You must use a hardened steel nozzle.

The Golden Rule: Keep It Dry

The biggest secret in 3D printing is that plastic absorbs water from the air (it is hygroscopic).

If you leave a spool of PETG or Nylon on your desk for a week, it absorbs microscopic water droplets. When that water hits the 250°C nozzle of your printer, it boils instantly. The steam explodes out of the nozzle, causing popping sounds, horrific stringing, and extremely weak parts.

Always store your filament in airtight boxes with silica gel, and use a dedicated filament dryer before printing engineering materials!