# Load-Bearing Assessment of Threads in 3D-Printed Polymer Elements

## TL;DR

This study compares the strength of different methods for creating threaded joints in 3D-printed polymer parts.

## Contribution

The study provides empirical data on load-bearing capacity of printed threads versus metal inserts in SLS-printed PA12.

## Key findings

- Printed threads had the lowest load-bearing capacity at 3.41 kN.
- Helicoil inserts increased strength by 40% compared to printed threads.
- Failure in all cases occurred due to thread or insert pull-out.

## Abstract

The article presents a comparative analysis of mechanical properties of M8 threaded joints produced using three different methods, in rectangular nylon (PA 12) specimens manufactured in SLS technology. Threaded holes in specimens were made by direct thread printing (specimens marked PT), thread reinforcement with Helicoil inserts (HT), and the use of heat-set inserts (IT). The specimens were subjected to a tensile testing at a constant displacement rate of 2 mm/min. The maximum force and the displacement at failure were recorded. The results indicated that the lowest load-bearing capacity FMF was observed in the printed thread specimens, with an average value of 3.41 kN. The use of heat-set inserts increased FMF to 3.83 kN, representing a 12% improvement. The highest load-bearing capacity was achieved in specimens reinforced with Helicoil inserts, which enhanced joint strength by 40% compared to printed thread specimens, reaching an average FMF of 4.78 kN. In all cases, failure occurred due to the thread or insert pull-out from the specimen material. Studies have shown that the use of metal inserts significantly enhances the strength of threaded joints in SLS-printed PA12 components. Helicoil inserts provide the highest FMF load capacity, while heat-set inserts offer better technological advantages. Although printed threads are easier to manufacture, their applicability is limited to larger thread sizes and lower mechanical loads.