Filament Maker:
Preparing the Bottle

A complete guide on preparing a PET bottle ready for use with our Filament Maker.

 

Introduction

Recycling PET bottles into usable filament starts with proper bottle preparation. A well-prepared bottle ensures smooth, consistent strips that can be fed into the filament-making process without jams or inconsistencies.

This guide walks you through step-by-step instructions for preparing a plastic bottle, from drilling the cap and pressurizing the bottle to heating, cutting, and measuring. By following these steps carefully, you’ll create evenly processed PET strips, leading to higher-quality filament and better final prints.

Whether you're using boiling water or a heat gun to shrink the bottle, the key is to achieve a smooth, uniform surface before cutting. Consistency at this stage will make a huge difference in the reliability of your filament. Let's get started! 🚀♻️

Getting Started

You will need:

  • Protective Gloves & Safety Goggles – Essential for handling heat and pressure safely.

  • Bottle Cutter & TR525 Tire Valve - Included with the Filament Winder

  • Drill – For creating a hole in the bottle cap.

  • 10mm Drill Bit – For accurately sizing the hole for the tire valve.

  • Bike Pump or Air Compressor – To inflate the bottle (max 25 PSI).

  • Sharp Scissors or Craft Knife – For cutting the bottle.

  • Calipers – To measure bottle thickness accurately.

  • Heat Source:

    • Option 1: Boiling water (for the water immersion method).

    • Option 2: Heat gun (for direct heating).

Optional Extras:

  • Rubbing Alcohol or Acetone – Helps remove label residue and glue from bottles.

  • Paper Towels or Cloth – Useful for cleaning bottles before cutting.

A clean, label-free bottle with a uniform cut is essential for high-quality filament. Inconsistent prep leads to weak spots and print issues.

FAQs

Step 1 - Remove Labels & Clean the Bottle

Peel off any labels and rinse the bottle thoroughly to remove any leftover liquid or residue.

Step 2 - Drill Hole in Bottle Cap

Using a 10mm drill bit, create a hole in the top of the bottle cap.

Step 3 - Insert Tire Valve

Push the TR525 tire valve into the drilled hole and tighten it securely.

Step 4 - Attach Cap to Bottle

Screw the modified cap back onto the bottle.

Step 5 - Pressurize the Bottle

Use a bike pump or air compressor to inflate the bottle to a maximum of 25 PSI (for a 2L bottle).

Step 6A - Heat the Bottle (Boiling Water Method)

Slowly pour boiling water over the bottle while rotating it for even heating. A drill with a spinning jig can help.

Step 6B - Heat the Bottle (Heat Gun Method)

Set the heat gun to high, point it upwards, and rotate the bottle evenly over the heat source.

Step 7 - Ensure a Smooth Surface

Continue heating until the bottle shrinks evenly and has a smooth, wrinkle-free surface.

Step 9 - Remove Glue Residue

After heating, check for any leftover glue from labels. Use rubbing alcohol or acetone with a cloth to remove any sticky residue before continuing.

Step 10 - Depressurise the Bottle

Slowly remove the cap to release the pressure inside.

Step 11 - Cut the Bottom Off

Use scissors or a craft knife to remove the bottom of the bottle, ensuring a clean, straight cut.

Step 12 - Measure Bottle Thickness

Use calipers to measure the bottle’s thickness—it should be between 0.1mm and 0.3mm.

Step 13 - Adjust Cutter Settings

Insert the appropriate spacers into the bottle cutter based on the measured thickness and tighten them.

0.1mm = 10mm strip

0.2mm = 9mm strip

0.3mm = 8mm strip

Step 14 - Cut Tail for Cutter

Cut a small angled tail at the bottom edge of the bottle to help guide it into the cutter.

Step 15 - Feed Bottle into Cutter

Place the bottle over the threaded rod and feed the tail into the bottle cutter.

Step 16 - Pull Tail Through Cutter

Pull the PET strip gently but firmly through the cutter to start cutting the bottle into a continuous strip.

Step 17 - Spool the Strip

Wind the cut PET strip onto the Strip Spool, following the direction of the arrows.

Congratulations!
Your rPET Filament is now ready for you to start making filament.

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