How to choose a good hot press
The first need to choose your own appropriate operating table scale, hot press and machine pressure has a great relationship, now is usually hydraulic, then the hydraulic cylinder is the first part:
Fault diagnosis and treatment
1, the hydraulic cylinder misoperation or action failure
The reasons and solutions are as follows:
(1) the valve core is stuck or the valve hole is blocked. When the flow valve or direction valve spool is stuck or the valve hole is blocked, the hydraulic cylinder easy to make the wrong action or action failure. At the moment should check the oil pollution status; Check dirt or gelatinous deposits to see if they are sticking to the spool or blocking the orifice; Inspect valve body for wear.
(2) piston rod and cylinder are stuck or hydraulic cylinder is blocked. At the moment, no matter how the operation, the hydraulic cylinder does not move or little action. At this time should check the piston and piston rod seal is not too tight, is not into the dirt and gelatinous sediment: piston rod and cylinder cylinder axis line is right, vulnerable parts and seals are not failure.
(3) the control pressure of hydraulic system is too low. Control pipeline to save resistance can be too large, the flow valve improper conditioning, control pressure is not appropriate, the pressure source is disturbed. At this point, you should look at the source of the operating pressure to ensure that the pressure is regulated to the system. (4) hydraulic system into the air. First of all, there are leaks in the system. At this time should check the level of the hydraulic tank, hydraulic pump suction side seals and fittings, suction strainer is not too dirty. If so, replace the hydraulic fluid, dispose of the seals and fittings, clean or replace the coarse filter element.
(5) the initial action of the hydraulic cylinder is slow. Under the condition of lower temperature, the viscosity of hydraulic oil is large and the fluidity is poor, which causes the slow action of hydraulic cylinder. The improvement method is to replace the hydraulic oil with better viscosity temperature function, which can be heated by heater or machine itself at low temperature to improve the oil temperature at startup.
2. The hydraulic cylinder cannot drive the load during operation
The first performance for the piston rod stop position prohibition, lack of thrust, speed decline, the operation of the cause of instability is
(1) leakage in the hydraulic cylinder. The leakage in the hydraulic cylinder includes the leakage caused by excessive wear of hydraulic cylinder body seal, piston rod and seal cover seal and piston seal.
Piston rod and seal cover seal leakage reason is that the seals wrinkle, knead, tear, wear, aging, decay, deformation, at the moment should replace the new seal.
The primary cause of excessive piston seal wear is improper speed control valve conditioning, the formation of excessive back pressure and sealing device improper or hydraulic oil pollution. The second is the device when foreign matter into and sealing material quality is not good. The result is slow, weak, severe will also form the damage of piston and cylinder cylinder, presents the appearance of "cylinder". The disposal method is to adjust the speed control valve, the control device should do the necessary operation and improvement; Clean filter or replace filter core, hydraulic oil.
(2) leakage of hydraulic circuit. Includes leakage of valves and hydraulic piping. The maintenance method is to check and eliminate the leakage of hydraulic connection pipeline through the operation of the reversing valve.
(3) the hydraulic oil is returned to the oil tank through the bypass of the overflow valve. If the overflow valve into the dirt stuck spool, so that the overflow valve is often open, the hydraulic oil will bypass the overflow valve directly flow back to the oil tank, resulting in no oil into the hydraulic cylinder. If the load is too large, the relief valve regulating pressure has reached the maximum rating, but the hydraulic cylinder still can not get the thrust required for continuous action and do not move. If the pressure is low, the pressure is not enough to reach the required force, which is not good for thrust. The overflow valve should be viewed and adjusted at this time.
3, hydraulic cylinder piston slip or creep
Hydraulic cylinder piston slip or creep will make the hydraulic cylinder operation unstable. The first reason is as follows:
(1) the hydraulic cylinder internal astringency. The internal parts of the hydraulic cylinder are improper, the parts are deformed, worn or exceed the limit of the service, the action resistance is too large, so that the piston speed of the hydraulic cylinder changes with the direction of the stroke, presenting slip or creeping. The reason is mostly due to the poor quality of parts and devices, the appearance of scar or sintered iron scrap, so that the resistance increases, speed down. For example: piston and piston rod is not the same core or piston rod twists and turns, hydraulic cylinder or piston rod on the guide device azimuth deviation, sealing ring installed too tight or too loose. The solution is to repair or adjust from scratch, replace damaged parts and remove iron filings.
(2) poor smoothness or poor bore machining of hydraulic cylinder. Because piston and cylinder cylinder, guideway and piston rod all have relative motion, if smooth bad or aperture of hydraulic cylinder is out of tolerance, can aggravate wear, make cylinder cylinder center line linear sex drops. In this way, the piston in the hydraulic cylinder operation, friction resistance will be small and large, the occurrence of slip or creeping. Cleaning method is to first grinding the hydraulic cylinder, then according to the needs of the manufacture of pistons, repair grinding piston rod, equipment guide sleeve.
(3) hydraulic pump or hydraulic cylinder into the air. Air compression or expansion may cause piston slip or creep. Cleaning method is to check the hydraulic pump, set up a special exhaust device, quick operation full stroke reciprocating several exhaust.
(4) the quality of seal is directly related to sliding or creeping. When o-shaped sealing ring is used under low pressure, it is compared with u-shaped sealing ring, because the surface pressure is higher and the difference of dynamic friction resistance is larger, it simply slips or crawls. U-shaped seal face pressure to follow the progress of the pressure and increases, while sealing function also corresponding improvement, but the dynamic frictional resistance is larger, the difference between the internal pressure to add, elastic rubber, because the lip edge touch resistance increases, the seal will be tilting and lip edge elongation, simple also cause slip or prostrate, can be used to avoid the tilting bearing ring sticking to its safe.
