Hydraulic Cylinder Oil Leakage Fault of Material Rack Matched with 160T Servo Punch Press

Case Study on Hydraulic Cylinder Oil Leakage Fault of Material Rack Matched with 160T Servo Punch Press, Root Cause Analysis, Repair Scheme and Long-Term Maintenance Suggestions This case targets a 160T servo open punch equipped with heavy-duty hydraulic material rack for 2–6mm thick automotive motor shell stamping. The equipment has run continuously for 14 months in 2-shift production. The user reported that oil dripped from the piston rod of material rack clamping hydraulic cylinder. The clamping force gradually decreased, coil slipped during feeding, and oil contaminated the stamping sheet, resulting in 3.2% product rejection rate before shutdown. The after-sales team carried out systematic troubleshooting step by step: visual inspection found oil film and dripping on cylinder rod surface; pressure holding test verified obvious internal leakage; oil sample test showed excessive metal particle pollution. Disassembly confirmed that the polyurethane rod seal was hardened and partially scratched, and tiny metal chips from hydraulic oil scratched the piston rod wiper seal. The root cause was that the hydraulic return filter was blocked, oil cleanliness exceeded standard, abrasive particles damaged the sealing assembly under repeated pressure impact. The repair scheme included full replacement of the complete sealing kit, cleaning of hydraulic pipeline and oil tank, replacement of filter element, new anti-wear hydraulic oil filling, pressure holding calibration and full-load operation verification. In addition, the technical team optimized the customer’s maintenance checklist and set oil sampling cycle and seal inspection reminder to prevent repeated similar failures.

Q1: What is the difference between external leakage and internal leakage of hydraulic cylinder for stamping material rack? A1: External leakage is visible oil dripping from piston rod or end cover; internal leakage means oil bypasses piston seal inside cylinder without external dripping, which only shows insufficient holding force and slow cylinder action. Q2: Why is the material rack hydraulic cylinder more prone to seal damage than ordinary hydraulic cylinders? A2: The material rack cylinder bears frequent impact load when clamping heavy steel coils. Pressure fluctuates repeatedly with punch stroke, and metal powder generated from stamping easily enters the hydraulic oil circuit and abrades seals. Q3: What seal material is recommended for heavy load material rack hydraulic cylinder on servo punch? A3: Polyurethane main seal with PTFE back-up ring and buffer ring is recommended, which can resist pressure impact and abrasion under continuous cyclic load. Q4: What are the steps for pressure holding test after cylinder overhaul? A4: Raise pressure to rated working pressure, isolate the cylinder, keep static for 30 minutes and record pressure drop, check rod and end cap for oil seepage. Q5: How to formulate periodic maintenance plan for material rack hydraulic system? A5: Conduct monthly visual inspection of oil leakage; oil sampling test every 3 months; replace filter element every 6 months; full seal inspection every 12 months. Q6: What preventive measures can reduce metal particle contamination in hydraulic oil? A6: Install high-precision return filter, regularly clean oil tank sediment, avoid mixing different hydraulic oil types, and keep the oil tank breathing filter intact.