This video details the design, optimization, and testing of a 3D-printed hook for a competition at the "Makers Retreat" event, sponsored by Polymaker. The challenge required designing a hook weighing less than 50 grams, printed without assembly, and capable of attaching to 8mm shackles without disassembly. The presenter developed an innovative "interlocking J-hook" design, featuring two C-shaped sections with internal teeth and a 3D-printed spring to allow print-in-place assembly and shackle attachment. The design was optimized using theoretical calculations for a 1-ton target load and Finite Element Analysis to minimize stress concentrations, incorporating a custom hollow structure with filleted internal corners. In the competition, the PLA version of the hook proved superior, winning its rounds with a breaking force exceeding 400 kg. A subsequent destructive test demonstrated the hook's remarkable strength, breaking at over 1.1 tons (1100 kg). Post-failure analysis revealed the primary failure point was a stress concentration at the tight angle of the first tooth, leading to recommendations for future design improvements.
Summarizing the 3D-Printed Hook Challenge and Design Process
0:00 Makers Retreat Challenge: The presenter participated in a 3D-printed hook competition at the Makers Retreat event, sponsored by Polymaker, requiring a hook under 50g, printed without assembly, and attachable to 8mm shackles without disassembling them.
0:53 Design Constraints & Prior Art: The design had to accommodate an 8mm shackle opening, making a simple C-hook weak due to bending forces. While latch designs improve strength, they introduce new weak points and flexibility challenges for print-in-place designs. Previous Polymaker competitions used different rules, allowing non-opening loops.
2:57 Innovative Interlocking J-Hook Design: The presenter's solution involves two C-shaped (J-hook) parts with interlocking teeth, connected by a 3D-printed spring. This allows the hook to be printed as a single piece, open to accept the shackle, and then lock together, balancing forces like a solid loop.
3:37 Self-Engaging Teeth Mechanism: The teeth are designed to bite harder with increased tension, making disengagement nearly impossible unless the hook structure itself breaks.
4:04 Preliminary Bodyweight Test: A 10% scaled-down version (2mm thick) successfully held the presenter's 85kg body weight, indicating the full-thickness hook could theoretically hold over 850kg.
4:46 Structural Calculations for 1 Ton: Using Polymaker PLA's tensile strength (52 MPa), calculations for a 1-ton (9810N) load suggested a minimum cross-sectional area of 190 mmΒ², which was doubled for a safety factor. The hook was designed as short and wide as possible to optimize mass distribution.
5:52 Custom Hollow Section & FEA Optimization: The hook was designed with a custom hollow section (like an I-beam) with filleted internal corners to prevent stress concentrations, printed with 100% perimeter walls. Finite Element Analysis (FEA) was used to achieve uniform stress distribution, indicating peak stresses in areas that would rotate during real-world testing.
7:21 Competition Setup and Material Choice: The competition used a 2-ton hydraulic crane and a 1.5-ton scale. The presenter chose PLA for its highest rigidity, aiming to keep the interlocking teeth engaged.
8:20 Competition Victory: The presenter's team won the competition against Jon's design from Proper Printing, with their hook holding 405 kg before the opponent's hook broke.
9:07 Destructive Testing to Limit: To find the ultimate breaking point, the winning hook was re-tested. It withstood progressively increasing loads, finally breaking at an impressive 1.1 tons (over 1100 kg).
11:14 Failure Analysis & Redesign Ideas: Post-mortem analysis suggested the hook broke at the first tooth due to a tight internal angle causing a stress concentration. Proposed improvements include increasing the internal radius of the tooth and reinforcing the area around the teeth with material from the hook's sides.