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

Area of Science:

• Additive Manufacturing
• Materials Science
• Mechanical Engineering

Background:

• Selective Laser Sintering (SLS) is a key additive manufacturing technology for producing functional polymer parts.
• Threaded joints in polymer components often require reinforcement to meet mechanical demands.
• Evaluating methods for enhancing the durability of threaded connections in SLS-printed polyamide 12 (PA 12) is crucial.

Purpose of the Study:

• To comparatively analyze the mechanical properties of M8 threaded joints in PA 12 specimens fabricated via SLS.
• To assess the effectiveness of direct thread printing versus metal insert reinforcement (Helicoil and heat-set) on joint strength.
• To determine the failure modes and load-bearing capacity of different threaded joint configurations.

Main Methods:

• Rectangular PA 12 specimens were manufactured using SLS technology.
• Three types of M8 threaded joints were created: direct printed threads (PT), Helicoil inserts (HT), and heat-set inserts (IT).
• Tensile testing was performed at a constant displacement rate (2 mm/min) to record maximum force (F_MF) and displacement at failure.

Main Results:

• Direct printed threads (PT) exhibited the lowest load-bearing capacity (average F_MF = 3.41 kN).
• Heat-set inserts (IT) improved load-bearing capacity by 12% (average F_MF = 3.83 kN).
• Helicoil inserts (HT) provided the highest load-bearing capacity, enhancing joint strength by 40% (average F_MF = 4.78 kN).
• Failure in all specimens occurred due to thread or insert pull-out.

Conclusions:

• Metal inserts significantly enhance the mechanical strength and load-bearing capacity of threaded joints in SLS-printed PA 12 components.
• Helicoil inserts offer superior load capacity, while heat-set inserts present better technological advantages.
• Direct printed threads are suitable for lower mechanical loads and larger thread sizes, but have limited applicability for high-strength requirements.