Utility Carabiner v2

This is a robust 3D printed carabiner with higher load capability and better gate function than most other 3D printed carabiners out there.

Obviously these are not for climbing, they are plastic. If you depend on this carabiner to save your life from a fall, you will probably die.

v2 - Improved version with better gate:

More reliable, longer lasting, easier to assemble and disassemble. Modified frame profile to minimize overhang. Now with 3 different carabiner sizes provided and original Solidworks files.

Features:

• Design based on wire gate climbing carabiners to maximize strength and utility
• Preloaded gate tension for reliable closure
• Hook latch so gate will not pop out under load
• Major axis pushed close to spine for maximum strength under load
• Easy to assemble, twist-lock gate assembly
• Fast and easy to print, no supports, no intricate features

I have load tested these and they are surprisingly strong. With PLA and 50% infill it has a breaking force of over 150 lbs. With 100% infill it is over 300 lbs; in fact I couldn't get it to break because I didn't have enough weight. Let me know in the comments if you can break a solid one and what it took.

Carabiner Frame Dimensions:

• Small - 70 x 40 x 5 mm
• Medium - 92 x 52 x 6 mm
• Large - 134 x 74 x 7 mm

Print Recommendations:

• Material: PLA or PETG - you could try ABS, but might be too brittle for the gate. 
• Quality: 0.2 mm layers, 0.4mm nozzle 
• Initial Layer Horizontal Expansion: -0.1 - Negates elephant's foot.
• No supports

Carabiner Frame:

• Wall Line Count: 3
• Infill: 50 - 100% depending on how strong you want it to be

Carabiner Gate:

• Wall Line Count: 6+ fully filled with walls for proper spring strength

PETG is great for best springiness of the gate, but PLA works quite well too.

If you have a problem with the gate fitting through the holes, it is due to printing tolerances. Try one or more of the following to correct: Scale the gate down 0.2 mm in Z-axis only, Set horizontal expansion = -0.1 on frame, or set wall ordering = outside to inside for better dimensional accuracy.

Post-Printing

Gate Assembly

Allow the gate to fully cool before assembling for it to best retain it's shape under tension.  Follow the picture below. Push the ends of the gate through the smaller side of the hole, lower hole first. It's designed to be a tight fit so you will need to push hard and wiggle to work it through.

How I Designed This

Modeled in Solidworks based on design of wire gate climbing carabiners. Parameterized to easily adapt to different sizes. Printed 7 design iterations until the design was optimized for usability, durability, reliability, and strength. Load tested and field tested for many months.