Because the hydraulic cylinder is in the working process, due to the unreasonable assembly and connection of the hydraulic cylinder, the resultant action line of the hydraulic cylinder and the motion axis of the piston rod that are loaded in the working process deviate, which leads to the "special force" of the hydraulic cylinder, which causes the hydraulic cylinder to not work. This can be eliminated by following these steps:
In the design, according to the size of the load, draw a force equilibrium diagram, try to make the resultant line of the load and the center line of the piston coincide, not a straight line of different planes, not a parallel line far apart.
Injection molding machines, some use four cylinders, some use two nozzles, if each cylinder is not synchronized, it will cause uneven force. When the force is too large, the oil cylinders cannot be interchanged, and the problem of multi-cylinder linkage should be paid attention to.
The hydraulic cylinder is installed on the main engine, if it is not centered, it is easy to be forced and cannot be indexed. Align the cylinder and determine whether there is force. The piston rod can be placed in three positions: fully withdrawn, centered and fully pressed into the cylinder, and checked with a spirit level or dial gauge. When the piston rod is fully pressed, if the piston rod can be smoothly detached or fixed, it is properly installed, otherwise it needs to be adjusted.
In long-stroke hydraulic cylinders, excessive oil pressure is a prominent problem. In addition to installation errors, the mass of the piston and piston rod and cylinder can also cause excessive thrust, which increases the friction between the piston rod and cylinder head support sleeve hole, piston and cylinder bore. To this end, the weight of the piston rod must be reduced as much as possible on the piston rod (using a hollow tube), the width of the piston rod and the length of the guide sleeve must be appropriately increased, and an intermediate auxiliary support matching the outer diameter of the cylinder must be installed on the piston to reduce the cylinder separation and vibration caused by the bending stress between the piston rod and the cylinder.
The connection between the piston rod and the load should avoid the use of rigid and fastened connections, and instead use movable hinges or ball joints. For cylinders with flanges on one side of the piston rod, special attention should be paid to the verticality between the flange and the axis of the piston rod during processing and installation, so as to avoid the reaction force caused by the difference in verticality.
Due to the poor stiffness of the cylinder foundation, it will also cause uneven force, and the foundation stiffness should be strengthened to avoid foundation deformation.
Due to the reaction of the load, the cylinder is deflected and the external force is deflected. After installation, most of them can not carry out no-load test, only load test to see if there is any deviation between the thrust action line of the piston rod and the center line of the load combination under load conditions.
The surface of the slide rail connected to the hydraulic cylinder is unbalanced with the moving axis of the hydraulic cylinder, or the insert of the guide plate is squeezed too tightly (such as the injection seat in and out of the injection seat guide rail of the injection molding machine);or (non-parallel twisting of the centerline of the four cylinder guides at the closed part of the mold, and brushing of the cylinder guides (injection molding machine).Or there is a lack of lubrication on the surface of the guide rail, or there is dirt falling on the surface of the guide rail, etc., corresponding measures can be taken to eliminate. In addition, when designing, it is necessary to accurately estimate the friction of the guide rail.
In large-scale injection molding machines, hydrostatic guide rails and unloading guide rails (injection seat advance and retreat, guide rails) are used, and when the flow restrictor, lubricating oil stabilizer, etc. fails, no pressure oil will flow into the oil cavity of the guide rail, and the static pressure effect and pressure relief effect cannot be achieved. The weight of the table was hard pressed on the guide rails, and there was a lot of friction, which led to the failure of the hydraulic oil supply system.