With the rapid development of modern industry and equipment manufacturing, electric cylinders are widely applied in various fields such as equipment and precision automation. Aiming at the problems of lug fracture and abnormal noise occurring at the base of a bracket-mounted micro electric cylinder, this paper proposes a solution through mechanism analysis and experiments.
①. Mechanism Analysis
Abnormal noise is generated by dry friction between the trapezoidal nut and the lead screw. Since the movement between the trapezoidal lead screw and the nut forms a sliding friction pair with very low efficiency, it has high requirements for grease lubrication. Based on the feedback from the above tests, it can be concluded that the issue arises from insufficient internal lubrication of the electric cylinder. After multiple lifting operations, the limited internal grease is consumed by friction, resulting in dry friction in the screw pair which produces a harsh noise, amplified through the cylinder body.
②. Fracture Mechanism Analysis
Base material issues: The lugs on the base of the micro electric cylinder are welded, and the base material is 45# steel, a medium carbon steel with extremely poor weldability. Achieving ideal welding quality requires multiple process guarantees, such as preheating the base material, heating the welding electrodes, using gas metal arc welding, and performing timely stress relief heat treatment after welding.
Weld issues: Actual inspection of the fracture surface at the failure point revealed that no groove was formed at the joint of the lugs on the bottom of the electric cylinder. The weld height and width are less than 5mm, while the base material thickness is approximately 16mm.
③. Field Test Analysis
Based on the above analysis, repeated tests were conducted on the noisy micro electric cylinder. It was found that after multiple repeated tests, the cylinder became stuck. Upon opening the electric cylinder chamber, copper powder from the nut was found scattered around the lead screw, with no oil film on the lead screw surface. When grease was applied to another noisy cylinder, no abnormal noise was produced during repeated tests. This confirms that the cause of this fault in the micro electric cylinder is abnormal lubrication between the lead screw and the nut.
④. Improvement Measure Analysis
The piston rod of the micro electric cylinder is thoroughly cleaned, and sufficient Mobil 100 grease is added internally to replace the original small amount of low-temperature grease. This ensures that the surfaces of the nut and lead screw can be fully lubricated when the trapezoidal lead screw generates heat during movement, preventing the oil film from being damaged by high temperature and pressure. Additionally, an oil injection hole is added at the head end of the piston rod to facilitate maintenance after multiple movements or years of use.
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