What are the causes of the fracture of trapezoidal lead screws?

The fracture of trapezoidal lead screws is usually the result of the combined effect of multiple factors. Mainly, it can be attributed to the following five aspects:

1. Load and operating conditions (Improper use):

1.1. Overload and impact: Exceeding the rated load of the lead screw or experiencing sudden impact loads and instantaneous overload during equipment operation, causing the stress on the lead screw to exceed the strength limit of the material and leading to fracture.

1.2. Frequent alternating loads (fatigue fracture): Equipment operating under alternating stress for a long time or frequent start-stop, sudden acceleration and deceleration, resulting in fatigue cracks in the lead screw and eventually a fatigue fracture under low stress conditions.

1.3. Harsh operating environment: Severe vibration during equipment operation or resonance, intensifying the fatigue damage to the lead screw.

2. Installation and mechanical fit factors (Improper installation):

2.1. Installation skew and abnormal force: Failure to perform proper alignment calibration during installation, causing the lead screw to bear abnormal radial force or alternating shear stress (such as unilateral force, cantilever beam force); or improper bearing installation clearance, excessive pre-tightening force of the locking nut, resulting in the bending of the lead screw shaft neck and local stress concentration.

2.2. Mechanical interference and jamming: Equipment operation due to foreign objects entering causing jamming of the lead screw with the nut, or excessive tension of synchronous belts/ couplings, misalignment, causing the lead screw to bend repeatedly and generate additional bending moments that lead to fracture.

3. Material and manufacturing factors (Inherent defects):

3.1. Material defects: Internal defects in the raw material (such as excessive net carbide level, unqualified spheroidizing annealing structure) or insufficient material strength, causing the lead screw to fracture prematurely under normal load.

3.2. Heat treatment and processing defects: Improper heat treatment (such as excessive quenching temperature, insufficient tempering) resulting in uneven hardness, excessive internal stress, or grinding cracks during grinding processing, reducing the fracture toughness of the lead screw.

3.3. Design defects: Sharp corner design at the shoulder of the lead screw, causing local stress concentration, prone to crack formation and expansion under alternating stress.

4. Maintenance and wear factors (Post-operation deterioration):

4.1. Severe wear: Long-term operation of the equipment resulting in severe wear of the lead screw surface, or damage to the threads due to wear or foreign objects entering, weakening the cross-sectional area and strength of the lead screw, making it prone to fracture under load.

4.2. Poor lubrication: Insufficient lubrication leading to increased friction, movement jamming, excessive local temperature rise, intensifying material fatigue and wear, indirectly causing fracture.

5. Temperature factors:

Equipment operating in high-temperature or low-temperature environments for a long time, or poor lubrication resulting in excessive local temperature rise, will affect the mechanical properties of the material, reducing the strength of the lead screw, thereby causing fracture.

Contact us for more details!