The crankshaft repair
Repair of crankshaft wear
Generally speaking, the diameter of the journal is below 80mm, and the error of roundness and cylinder is more than 0.025mm; Or the journal diameter is more than 80mm. Crankshaft with roundness and cylinder error of more than 0.0400 shall be repaired according to the specified size, or shall be subjected to vibration surfacing, chromium plating, and iron plating before grinding to the specified size or repair size.
Repair of the crankshaft after severe wear and tear
If the engine crankshaft is badly worn, the grinding method cannot be repaired or the effect is poor, the plasma spraying method can be used to repair it.
Spray the surface treatment of the front neck
According to the wear of the journal, it is rounded in a crankshaft grinder, and the diameter is generally reduced by 0.50-1.00mm.
Cover the adjacent neck of the journal to be sprayed with copper
Use a hairdryer to treat the surface of the coating for tensile processing. A nickel strip is used as an electrode, and nickel is melted on the journal surface under 6 ~ 9v, 200 ~ 300a alternating current.
Spraying
The crankshaft is stuck on the rotatable table to adjust the distance between the spray gun and the workpiece (about 100mm). The selection of nickel-coated aluminum (Ni/AL) is the bottom material, and the mixture of wear-resistant alloy cast iron (NT) and nickel-coated aluminum is the working layer material; The bottom thickness is generally about 0.20mm, and the working layer thickness depends on the needs.
During the spraying process, the temperature of the spray neck should be controlled at 150 ~ 170. After spraying, the crankshaft is placed into the oven of 150-180 and the internal temperature of the oven is 2h and cooled with the box to reduce the stress between the spraying layer and the axial neck.
Treatment after spraying
After spraying, check whether the spraying layer and the journal matrix are closely combined, if not tight enough, remove the heavy spray. If the inspection is qualified, the crankshaft can be grinding. Due to the high hardness of the plasma spraying layer, the soft tin carbide grinding wheel is generally selected for grinding, and the feeding amount is smaller (0.05-0.10mm) when grinding, so as not to squeeze the coating. In addition, after grinding, the oil duct hole should be ground with a sand strip, so as not to scratch the tile. After cleaning, cook the crankshaft in 80-100 oil for 8~10 minutes. Yanmar engine has high engine crankshafts. In LandKingParts we sell Yanmar engine parts engines and parts for farm machinery, heavy trucks, and other large machinery. The Yanmar engine has superb quality if there is a need, welcome to consult to buy.
Analysis of the causes of crankshaft fracture
Crankshaft fracture is a serious machine fault of the engine, and the fracture usually occurs at the center of stress such as the rounded Angle of the crankpin and the shaft neck and the crank arm or the shaft oil hole.
About crankshaft maintenance requirements
1) decompose and clean crankshaft components to ensure clean and smooth oil channels within the crankshaft.
2) flaw detection of the crankshaft must be replaced if there is a crack. Carefully check the crankshaft spindle neck, connecting rod journal, and its rotating arc all surfaces shall not be scratched, burned, or touched.
3) check the crankshaft spindle neck and connecting rod journal, and repair it according to the repair grade after the size limit. Crankshaft journal repair is as follows.
4) check the hardness requirements of the crankshaft journal and connecting rod journal, which must meet the technical requirements. Otherwise, it should be reprocessed to meet the requirements of use.
5) the radial pulsation of the crankshaft radial circle and thrust in the face of the common axis of the spindle neck must meet the technical requirements. Otherwise, corrections must be made.
6) the parallel degree of the common axis of the spindle neck must meet the technical requirements.
7) when there is a serious crack, damage, and wear on the crankshaft drive gear before and after the crankshaft, the crankshaft shall be replaced.
8) if there is any crack in the crankshaft balance bolt, it must be replaced. After the crankshaft changes the balance block or the balance block bolt, the crankshaft assembly is tested for dynamic balance to ensure that the unbalance is in line with the technical requirements.
9) if there is any crack, scratch, or elongation of flywheel or pulley bolts exceeding the limit, replace them.
10) carefully check the shock absorber of the crankcase support foot, if damage, rubber aging, cracking, deformation, or crack, must be replaced.
11) when assembling the crankshaft, pay attention to the installation of spindle tile and thrust tile. Check the shaft clearance of the crankshaft and tighten the vertical and horizontal bolts of the main bearing cover as required. (first vertical, then horizontal)
