What should I do if the parts of the Rexroth gear pump are worn out? The general situation of Rexroth gear pump maintenance is because the parts are seriously worn. The maintenance of gear pumps is different from other types of pumps. The parts of Rexroth gear pumps that are seriously worn are usually: tooth meshing, involute working surface and The gears are flat on both ends. When there is slight wear, the tooth surface can be sharpened with oilstone, and the flat surfaces at both ends are polished on the flat plate. When the gear tooth surface is seriously worn, it should be replaced with a new gear immediately. If only the two surfaces of the gear are worn out, you can grind it on a surface grinder. After the replacement of the gear mapping, when the modulus m = 3, the number of teeth z = 12, the tooth profile angle α = 20 °, the tooth top height coefficient f0 = 1, the tooth profile positive displacement coefficient x1 = x2 = 0.5, the geometry of each part The dimensions are calculated as follows.

Rexroth gear pump repair

Indexing circle diameter: d = mz = 3X12 = 36 (mm)

Addendum height: ha = m (f0 + x) = 3X (l + 0.5) = 4.5 (mm)

Tooth root height: hf [= m (f0 + c-x) = 3X (l + 0.25-0.5) = 2.25 (mm)

Total tooth height: h = ha + hf = 4.5 + 2.25 = 6.75 (mm)

Diameter of addendum circle: Da = d + 2ha = 36 + 2X4.5 = 45 (mm)

Fixed chord tooth thickness: Sxn = m (π / 2 * cos2a + xsin2a) = 3X (1.387 + 0.6428X0.5) = 5.125 (mm)

Tooth height for fixed chord tooth thickness measurement: hxn = m (π / 8 * sin2a + xsin2a) = 3X (0.7476X0.117X0.5) = 2.42 (mm)

Modulus m3 displacement coefficient x0.5

Tooth profile angle o20 ° fixed chord tooth thickness Sxn5.12

Tooth height coefficient f1 fixed chord tooth thickness measured the highest tooth height hxn2.42

Number of teeth z12

2. Maintenance after shaft wear

The wear of the shaft in the gear pump is usually due to the friction and wear between the two ends of the shaft and the support needle, which makes the shaft diameter smaller. If it is slightly worn, the diameter of the shaft at this part can be increased by plating a layer of hard chrome to repair the shaft. If the shaft wear is serious, it should be re-manufactured by 45 steel or 40Cr steel. After the rough shaft is roughened and refined, the bearing part should be heat-treated with a hardness of HRC60-65, and then ground, so that the surface roughness Ra of the bearing matching part Greater than 0.32μm; the roundness and cylindricity tolerance of the shaft is 0.005mm; according to H7 / h6, the surface roughness Ra should not exceed 0.63μm.

Rexroth gear pump repair

3. Maintenance after the pump body is worn

The surface wear of the pump body is mainly the arc-shaped working surface of the oil suction section. If slight wear occurs, it can be used after grinding and deburring with oil stones. The pump body is formed by cast iron casting blank, and new parts should be replaced when serious wear occurs. If the two end surfaces of the internal gear of the pump are repaired by grinding, the width of the pump body should also be changed, which is equal to the size removed by the two ends of the gear. 

4. Maintenance after the two end covers are worn

The end cover of the gear pump is made of cast iron. After the phenomenon of wear occurs, it can be slightly flattened on the flat plate. If the wear is serious, it should be flattened on the surface grinder.
The surface contact between the end cap and the pump body after the grinding should be no less than 85%. The tolerance of the parallelism of the lines is 0.01 mm. The surface roughness Ra after grinding should be no more than 1.25 μm.

5. Maintenance and replacement of needle roller bearings for pumps

After the parts in the pump are repaired, the bearing needle rollers should be replaced. The requirements for the needle rollers are: the size error of all needle roller diameters should not exceed 0.003mm, the length tolerance is 0.1mm, and the clearance between the shaft and the shaft should be about 0.01mm; The needle rollers should be arranged parallel to each other.