3D Printable Tubes (No Supports Needed!)

This is a parametric, 3D printable 8-sided hollow tube (octagon outer profile) optimized specifically for functional 3D printing. Traditional circular tubes or square pipes usually require messy internal supports or suffer from weak structural integrity due to layer lines. This design solves both problems completely.

🛠️ Design Features

• Print Flat for Maximum Strength: Designed to lay completely flat on its length side. Printing horizontally aligns the filament layers along the entire length of the rod, dramatically increasing its tensile and bending strength compared to tubes printed standing vertically.
• 100% Support-Free Internal Core: The internal hollow cutout is a square rotated by 45 degrees. When lying flat, this forms a perfect diamond-shaped internal arch. The overhang angle never exceeds 45 degrees, allowing your printer to bridge the internal roof flawlessly without a single strand of support material.
• Stable Bed Adherence: The outer octagon profile is perfectly offset by 22.5 degrees so that it rests rock-solid on a wide, completely flat bottom face. It won't roll or wobble during printing.
• Perfect First Layer Placement: Ready to slice immediately out of the box with zero orientation tweaks required.

⚙️ How to Generate Custom Sizes in Blender

You can use the included Python script to dynamically generate custom tubes of any length, outer diameter, or inner hole size directly inside Blender.

1. Open Blender and switch to the Scripting workspace at the top of the interface.
2. Click New to create a blank text block, then copy and paste the provided Python script into the text editor window.
3. Click the Run Script play button in the text editor header to register the add-on.
4. Go back to your 3D Viewport and press Shift + A (or go to Add in the top menu bar).
5. Hover over Mesh and look at the bottom of the list. You will find two options:
   • Printable Tube: Click this to add a single custom tube. An operator panel will appear in the bottom-left corner of your viewport allowing you to input your exact Length, Outer Diameter, and Inner Hole Size.
   • Generate Tube Demo (4-30mm): Click this to instantly generate a continuous test sequence of 14 tubes ranging from 4mm to 30mm diameter spaced perfectly on your print bed.

📊 Demo & Sizing Guide

This design is highly customizable. The provided demo set includes a complete test sweep containing 14 tubes ranging from 4mm to 30mm Outer Diameter (in 2mm increments), all featuring a 20mm length and a matching safety-clamped inner core.

Geometrical Clearance Note

Because the outer shell is an octagon (low-poly circle), please note that the Outer Diameter measurement refers to the maximum point-to-point width (circumscribed).

• The actual flat-to-flat width of the outer walls measures exactly 92.38% of the stated diameter due to the 8-sided profile ($D \times \cos(22.5^\circ)$).
• Keep this in mind if you are designing tight mating sockets or matching engineering tolerances for a friction fit!

🖨️ Recommended Print Settings

• Orientation: Lay flat on its long side (Pre-oriented).
• Supports: DISABLED (Completely support-free, inside and out).
• Infill: 20% to 40% (Use Grid, Gyroid, or Rectilinear for maximum wall strength).
• Wall Loops / Perimeters: 3 to 4 walls for high structural strength.
• Material: PLA for rigidity, PETG or ABS/ASA for impact resistance and outdoor durability.