What is a hydraulic nut?
Views : 3168
Author : Mr. Jiang
Update time : 2021-02-20 15:23:49
Generally, low-end small slitting machines use mechanical nuts to lock all the tools on the slitter shaft, but the pressure force in axial direction it produces is very small, and it cannot overcome the extremely small allowable unflatness of the slitter blade and the slitting tool itself. Thus the upper and lower slitter blades are not in the ideal working position and cannot form a rigid cutting system. For solving this problem, hydraulic nuts are produced.
The hydraulic nut is a special device used to press and lock all the tools on the upper and lower shafts. Its inner diameter is a nut, which is screwed on the thread on the operating side of the upper and lower shafts. For a slitting machine with coils running from left to right (viewed from the operating side), the upper shaft is a right-hand thread, and the lower shaft is a left-hand thread. Because of inertia, with slitting line running, the hydraulic nut is getting tighter and tighter on the shaft and will not loosen.
When installing the hydraulic nut on the shaft, loosen the pressure-retaining screw and manually rotate it until the pressure ring against the tool, the pressure ring is retracted to the end, and the entire nut can no longer be turned. Then tighten the pressure-retaining screw and start to add oil pressure. There are two ways to pressurize hydraulic nuts: one is a small hydraulic nut, which uses a screw on the rotating shell to push a small piston to pressurize; the other is a large hydraulic nut, which is pressurized with a pump (refer to figure 1), both can produce high oil pressure of 30 ~ 40MPa. They use hydraulic principles to transmit pressure and push the pressure ring to lock all tools including slitter blades, bonded stripper rings, spacers, etc. in the axial direction to ensure:
1. The rigidity of the entire cutting system.
2. The correct position and clearance between the upper and lower slitter blades.
3. Eliminate accumulated errors.
Don't underestimate the pressure of the hydraulic nut. If the pressure reaches 30MPa, the diameter of the ring is 200mm and the ring width is 6mm, and its axial pressure can reach 113KN. It must be pointed out here that even if the tools supplied by the tool supplier have the highest precision, they still have an error within 0.002mm in flatness, especially for thin rings, whose flatness tolerance can reach 0.01~0.02mm. Many such thin rings are put in the male and female cutting units, which will seriously affect the precision of the upper and lower slitter blades. This requires a large enough axial force to flatten it so that each tool does not deviate from the precise theoretical position where it should be due to its flatness error. In addition, due to the huge axial force, the whole set of tools forms a rigid cutting system, so that the blades will not back down and deviate when subjected to huge cutting forces, resulting in dynamic clearance errors.
Figure 2 shows the position of hydraulic nut on the shaft. Although hydraulic nut is robust, necessary maintaining is a must. About maintaining and precautions for use, we will talk about in another article.
The hydraulic nut is a special device used to press and lock all the tools on the upper and lower shafts. Its inner diameter is a nut, which is screwed on the thread on the operating side of the upper and lower shafts. For a slitting machine with coils running from left to right (viewed from the operating side), the upper shaft is a right-hand thread, and the lower shaft is a left-hand thread. Because of inertia, with slitting line running, the hydraulic nut is getting tighter and tighter on the shaft and will not loosen.
When installing the hydraulic nut on the shaft, loosen the pressure-retaining screw and manually rotate it until the pressure ring against the tool, the pressure ring is retracted to the end, and the entire nut can no longer be turned. Then tighten the pressure-retaining screw and start to add oil pressure. There are two ways to pressurize hydraulic nuts: one is a small hydraulic nut, which uses a screw on the rotating shell to push a small piston to pressurize; the other is a large hydraulic nut, which is pressurized with a pump (refer to figure 1), both can produce high oil pressure of 30 ~ 40MPa. They use hydraulic principles to transmit pressure and push the pressure ring to lock all tools including slitter blades, bonded stripper rings, spacers, etc. in the axial direction to ensure:
1. The rigidity of the entire cutting system.
2. The correct position and clearance between the upper and lower slitter blades.
3. Eliminate accumulated errors.
Don't underestimate the pressure of the hydraulic nut. If the pressure reaches 30MPa, the diameter of the ring is 200mm and the ring width is 6mm, and its axial pressure can reach 113KN. It must be pointed out here that even if the tools supplied by the tool supplier have the highest precision, they still have an error within 0.002mm in flatness, especially for thin rings, whose flatness tolerance can reach 0.01~0.02mm. Many such thin rings are put in the male and female cutting units, which will seriously affect the precision of the upper and lower slitter blades. This requires a large enough axial force to flatten it so that each tool does not deviate from the precise theoretical position where it should be due to its flatness error. In addition, due to the huge axial force, the whole set of tools forms a rigid cutting system, so that the blades will not back down and deviate when subjected to huge cutting forces, resulting in dynamic clearance errors.
Figure 2 shows the position of hydraulic nut on the shaft. Although hydraulic nut is robust, necessary maintaining is a must. About maintaining and precautions for use, we will talk about in another article.
Fig. 1 Hydraulic Nut and Oil Pump for Slitter
Fig. 2 Hydraulic Nut on the Shaft
