The process of pipe bending is a complex elastic and plastic deformation process. The elastic or plastic deformation of a material mainly depends on the stress and strain inside the material, and the stress or strain inside the material is mainly caused by the external load acting on the material. In the process of pipe bending, the stress and strain inside the bending part of the pipe will undergo complex changes, and the magnitude, direction and change speed of the stress and strain will affect the quality of the bending pipe. Various quality defects in the bending process, such as cracks in the outer tube wall, wrinkles in the inner tube wall and cross section distortion, on the one hand, are related to the properties of the material itself; On the other hand, maintenance for automatic cnc pipe end forming machines is related to the size, direction, speed of the external load applied to the pipe and the relative position of the external load. As follows:

1 Pre-test

1.1 Hydraulic System

a. Test oil pump pressure flow loss.

b. Detect the loss of hydraulic parts.

1.2 Mechanical System

a. Detect worm gear wear.

b. Detect chain sprocket wear.

2 Maintenance Methods

2.1 With the bed as the base component, repair the wear and deformation, and restore the geometric accuracy of the matching part.

2.2 Each sliding part is matched to meet the geometric accuracy requirements.

2.3 Dressing worm gear and matching worm.

2.4 Repair sprocket and replace chain.

3 Quality Standards

3.1 Frame and foundation

a. After the device is straightened, the bolts are not loose or cracked.

b. The vertical flatness of the frame is 0.05/ (1000mm), the full-length flatness tolerance is 0.15mm, and the horizontal flatness is 0.04/ (1000mm).

3.2 Angle control and clamping

a. The positioning accuracy error of the Angle control part is less than 1 degree.

b. The tolerance of parallelism between the clamping guide rail and the base is less than 0.1/ (1000mm).

c. The contour tolerance of the clamping component mandrel guide component is less than 0.05/ (1000mm).

3.3 Guide and master cylinder

a. The tolerance of parallelism between guide rail and frame rail is less than 0.05/ (1000mm).

b. The axial displacement of the guide component under load conditions is less than 0.5mm.

c. Master cylinder components under rated load conditions without leakage, smooth movement without impact.

d. The gap of the cylinder guide sleeve is 0.03 ~ 0.05mm. There is no blocking phenomenon in operation.

3.4 Hydraulic System

a. No leakage under rated pressure, volumetric efficiency greater than 70%. Noise is less than 90 decibels.

b. Continuous operation oil pump temperature rise is less than 30ºC, maximum temperature is less than 65ºC, pressure fluctuation is less than 0.5Mpa.

c. Cylinder piston moving pressure loss is less than 0.5Mpa.

d. Pressure regulating valve, the whole process of pressure regulation should be uniform change.

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