How to repair tension marks on precision piston rods
If the precision piston rod is pulled during operation and not treated in a timely manner, it can affect the use of the product in mild cases, and in severe cases, make the hydraulic cylinder unable to work. So how do we fix it? Local grinding and polishing methods are used to repair lighter pull marks; For heavier pull marks, welding repair and manual grinding are used to repair them.
Formation of pull marks: After disassembling the gas-liquid booster cylinder, it was found that a precision piston rod was severely pulled, with 6 pull marks arranged side by side. The main reason for the pulling injury is that after the dust ring becomes brittle and falls off in a block like manner, it not only loses its dust prevention effect, but also accumulates a lot of dust and impurities in the expansion joint, causing the piston rod to grind hard with impurities, resulting in pulling injury. The scars then scratch the rubber sealing components at the cylinder port, causing serious leakage of the hydraulic cylinder.
Repair requirements: The filler and base material should be combined stably and smoothly; The seasoning must be easy to use and easy to manually process; Manual processing should ensure that the diameter error of the precision piston rod 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 prone to generating hydrogenated pores; Good craftsmanship and easy operation; Beautiful welding seam formation; The material has moderate hardness and is easy to process by hand; Stable arc, large melting depth, and stable bonding with the base material.
Repair process:
1. Clean the area to be welded first, and then surround the pull marks with damp 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 welding method to smoothly weld.
3. After all welding is completed, clean the mud and slag, and use a rough file to file 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 model (the outer diameter of the piston rod is 125mm). It is sawn along the axis, with one being a rough model and the other being a precision model.
5. Apply a thin layer of red ink on the inner wall of the rough mold, and then rub the rough mold tightly against the area to be repaired along the axis several times. Then, use a fine file to remove the heavier red ink on the product. Repeat the filing process and leave a machining allowance of 0.04-0.07mm.
6. Then use a 320 mesh sand strip dipped in kerosene and fine mold to grind the product to the specified size.
7. Afterwards, dip the back of the sandcloth in kerosene for manual polishing. After measurement, the significant error is only 0.03mm.
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