Mold opening force = mold opening oil pressure ring area × mold opening oil pressure
If you want to increase mold opening force under condition that maximum pressure is determined, you can only increase area of mold opening oil pressure ring, and you can increase area of mold opening oil pressure ring by increasing diameter of cylinder or reducing diameter of piston rod.

 

In mold opening section, due to small matching gap between hydraulic buffer sleeve and inner hole of cylinder front cover, pressure oil is slow or even difficult to enter mold opening cavity of cylinder, so maximum mold opening force cannot be provided. Increase matching gap between hydraulic buffer sleeve and inner hole of front cover of oil cylinder, so that pressure oil can quickly enter mold opening cavity of oil cylinder and form a mold opening force with a certain momentum, which may cause a certain impact when opening mold.

Design of machine hinge parameters, stroke and installation position of clamping cylinder determine final position of small hinge during high-pressure mold clamping and form a θ angle. Designed θ angle must ensure that θ angle of machine installed within accumulative machining tolerance range of each part must be absolutely less than 90°. Once θ angle exceeds 90°, small hinge will reverse hinge. At this moment, hook hinge and long hinge are actually moved towards straight line to generate a greater clamping force. Small mold opening force is not enough to overcome deformation force generated by increasing mold clamping force, so mold opening cannot be completed instantly.

After design of hinge of hinge machine is completed, magnification ratio of hinge when it produces predetermined clamping force has also been determined. Based on this, thrust of clamping cylinder can be designed to determine diameter of clamping cylinder. Oil cylinder must also ensure sufficient mold opening force. To have sufficient mold opening force, the larger diameter of oil cylinder, the better. However, if diameter of oil cylinder is too large, thrust of oil cylinder during mold clamping will be too large, which will overload mold clamping force (when mold adjustment is not good), deformation force of machine hinge is too large, and mold opening force cannot overcome excessive deformation force, resulting in failure to open mold. In this case, it is usually possible to prevent overloading of clamping force by limiting high-pressure clamping pressure and flow rate. Be patient when adjusting mold, and use a lower clamping pressure to adjust applicable clamping force as much as possible.

Due to low mold opening pressure and small flow rate, mold opening impulse is small, which cannot overcome deformation force of hinge, especially flow rate of the first stage of mold opening provided by servo control system is small, mold opening impulse is smaller, and it is more difficult to open mold. For this problem, mold opening impulse can be increased by modifying controller's PID and mold opening slope.

After a period of mold loading and pressure testing, mold will heat up and expand, and clamping force will increase, making it difficult to open mold. Pay attention to adjusting mold capacity in time to return clamping force to original value to avoid mold opening failure.

Too long downtime after mold clamping will lead to complete disappearance of lubricating oil film of machine hinge, further increase of deformation of the machine hinge, resulting in failure to open the mold, so reduce the downtime of mold clamping as much as possible, remember to open mold before shutting down, and do not lock mold in case of shutdown.

Setting mold opening back pressure at mold opening section on oil road will also lead to insufficient mold opening momentum. If this is found, cancel mold opening back pressure.

(1) Edge of oil groove in steel sleeve is not deburred, causing burrs to wear into particles and enter mating surface of large pin shaft and steel sleeve, causing mating surface to wear or burn to death. In order to avoid this problem, it is required that these parts must be machined after machining, remove burr and smooth it, check again during installation and clean all surfaces, apply grease and install.
(2) Insufficient lubrication or lubrication failure will also lead to excessive friction resistance. At this time, you can check whether each lubricating oil circuit is normal and whether lubricating pump is normal.