If the precision piston rod is pulled during operation and not dealt with in a timely manner, it may affect the use of the product, and in severe cases, the hydraulic cylinder may not work. How can we repair it? Adopt local grinding and polishing methods to repair lighter scratches; For heavier scratches, welding and manual grinding methods are used to repair them.
Formation of stretch marks: After disassembling the gas-liquid booster cylinder, it was found that one precision piston rod was severely pulled, with six stretch marks arranged side by side. The main reason for causing strain is that after the dust ring becomes brittle and falls off in a block shape, it not only loses its dust prevention function, but also accumulates a lot of dust and impurities in the expansion joint, causing the piston rod to directly rub against the impurities, resulting in strain, scratches, and damage to the cylinder rubber sealing component, causing serious leakage of the hydraulic cylinder.
Repair requirements: The filler and base material should be combined stably and smoothly; Seasoning must be easy to use and handle by hand; Manual processing should ensure that the precision piston rod diameter error is less than 0.06mm. After analysis, it was decided to use J422 welding rod as the filler. Because acidic welding rods are not sensitive to rust, oil stains, and moisture, and are not easily prone to hydrogenation pores; Good craftsmanship and easy operation; Beautiful weld formation; The material has moderate hardness and is easy to manually process; Stable arc, large melting depth, and stable bonding with the base material.
Repair process:
1. First, clean the area to be welded, and then surround the scratch with wet mud.
2. Select a welding rod with a diameter of 2.5mm, adjust the current of the welding machine to 120A, and use the straight line running method to smoothly weld.
3. After welding, clean up the mud and slag, and use a coarse file to trim along the circumference of the precision piston rod, leaving a machining allowance of 0.1-0.2mm.
4. A cylinder with an outer diameter of 185mm, an inner diameter of 125mm, and a length of 150mm is used as a reference mold (piston rod outer diameter of 125mm), which is sawed along the axis. One is a rough mold and the other is a precision mold.
5. Apply a thin layer of red ink on the inner wall of the rough mold, then press the rough mold against the part of the product to be repaired and run it back and forth along the axis several times, and then use a fine file to remove the heavier red ink on the product. Repeatedly file and leave a machining allowance of 0.04-0.07mm.
6. Then dip a 320 grit sand strip in kerosene and use a precision mold to grind the product to the specified size.
7. Afterwards, dip the back of the sandpaper in kerosene for manual polishing. After measurement, the significant error is only 0.03mm.