In machining, shaft parts are one of the main parts in the machine. It plays the role of supporting transmission, transmitting torque and bearing load. It is an indispensable part of mechanical equipment. However, in the process of production, shaft parts will wear out after working for a long time, so the maintenance method of porridge parts is very important.
Maintenance of general shaft
1. Wear of small shaft and shaft sleeve: replace with new parts, repair the small shaft as shaft sleeve or repair the shaft sleeve with small shaft.
2. Journal wear: for the wear of general transmission journal and cylindrical surface, the clearance fit or transition fit between shaft and shaft sleeve should be repaired or replaced if its accuracy exceeds half of the original fit tolerance, and the size reduction after repair should not exceed half of the nominal size; For the wear of shaft journals of transmission parts such as bearings, gears and pulleys, chrome plating or metal spraying shall be used to restore the size.
3. Wear of keyway: (1) appropriately increase the width of keyway or convert to another milling keyway when the strength allows; (2) The keyway on the shaft is reworked after surfacing.
4. Shaft end thread damage: (1) under the condition of not affecting the strength, the shaft end thread can be appropriately turned smaller; (2) Weld the threaded part of the shaft end and turn it to the size requirements.
5. The cylindrical conical surface on the shaft is damaged: (1) grind off the damaged surface according to the original taper, and grind it as little as possible; (2) The unimportant conical surface can be turned into a cylindrical shape and then fitted with a conical surface sleeve.
6. Wear of conical hole: (1) wear off the damaged part of the conical surface according to the original taper; (2) Boring into a cylindrical hole, complete with welding, and machining according to the original conical hole.
7. Pin hole damage: (1) ream the original pin hole and re allocate the pin; (2) Fill the transposition and reprocess the pin hole.
8. Flat head, end hole damage: (1) surfacing repair; (2) Reduce the size appropriately.
Maintenance of main shaft
1. The journal is worn, and its roundness and taper are different
(1) Repair and grind the journal, pay attention to maintaining the hardness layer on the surface of the shaft, shrink the inner hole of the bearing and grind it to the requirements or replace it with a new bearing;
(2) The shaft neck shall be polished, chrome plated or metal brush plated, and then externally ground to the requirements. The thickness of chromium plating layer shall not exceed 0.2mm.
2. Wear of journal installed with rolling bearing
Repair by local chrome plating, brush plating or metal spraying, and then fine grinding to restore the journal size; The maximum grinding amount of carburized main shaft journal shall not be greater than about 0.5mm; The maximum grinding amount of nitriding and cyaniding main shaft journal is about 0.1mm, and the surface hardness after grinding should not be lower than the lower limit value required by the original design.
3. Wear of spindle taper hole
There are burrs and bumps in the taper hole of the spindle, which can be removed with a scraper; If there is slight wear and the runout of the taper hole is still within the tolerance, it can be polished by grinding. If the accuracy of the taper hole is out of tolerance, it can be placed on a precision grinder to grind the inner taper hole.
3、 Maintenance of crankshaft
1. Local bending
(1) Press correction method: support the crankshaft on two V-shaped irons, press the convex surface with the press, and the amount of over correction should be greater than a certain multiple of the deflection, and maintain the load for a certain time. After straightening, conduct artificial aging.
(2) Knock the concave surface of the crankshaft with a hammer. The number of times to knock the same point should not be too many. The tapping point should be on the non machined surface.
2. Journal wear
(1) Grind down the journal, and the reduction of the journal shall not exceed 2mm.
(2) Large amount of wear can be repaired by spraying, bonding and other methods, but the strength must be checked before repair.
