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When the hydraulic cylinder is working at high speed or high inertia, the piston is prone to violent impact when it moves to the end of the stroke due to insufficient dissipation of kinetic energy, resulting in cylinder damage, increased noise, and even system paralysis. The buffer device uses the throttling damping principle to achieve piston deceleration and energy absorption, and is a key component to ensure the smooth operation of the hydraulic system. This article will start from the structural principle of the buffer device and analyze its common fault types and solutions.
01.Principles, functions and types of buffer devices
1. Working principle
When the piston approaches the end of the stroke, the buffer plunger enters the buffer chamber, forcing the oil to be discharged through the throttle port. The back pressure generated by the throttling forms resistance, which slows down the piston and converts kinetic energy into heat energy dissipation.
2. Function of the buffer device
- Eliminate the mechanical collision between the piston and the cylinder head, reduce the impact force and noise.
- Extend the service life of the hydraulic cylinder and supporting equipment.
3. Types of buffer devices
- Fixed throttling type: damping is achieved through annular gaps or fixed throttle holes, with a simple structure but not adjustable.
- Adjustable type: Use the throttle valve to adjust the opening size to meet the needs of different working conditions.
- Variable throttling type: The cone surface of the buffer plunger matches the hole, and the damping is automatically adjusted as the stroke changes.
- External throttling type: Buffering is achieved through an external valve group, which is highly flexible but costly.
02. Common faults and solutions
1. Excessive buffering
Fault manifestation: The piston decelerates too quickly, and even jams or pauses.
Causes and solutions:
- The throttle is too small: adjust the valve opening to the appropriate position and tighten it.
- The buffer plunger is “uneven”: the gap between the plunger and the buffer ring is too small or there is foreign matter, which requires cleaning, gap adjustment or replacement of parts.
- Poor processing or assembly: Check the coaxiality of the piston and the cylinder (the error must be ≤0.03mm), and correct the verticality deviation.
2. Failure of buffering
Fault manifestation: The piston does not decelerate, the end impact is severe, and even the cylinder head is damaged.
Causes and solutions:
- The regulating valve is fully open or fails: re-adjust the throttle valve, repair or replace the valve core and valve seat.
- The one-way valve is not tightly sealed: remove foreign matter from the steel ball or valve core, grind the sealing surface or replace the seal.
- Leakage in the buffer chamber: Check the damage of the piston seal and replace it in time; repair the scratches on the buffer plunger or bushing.
- Design defect: When the inertia force is too large, the buffer mechanism needs to be redesigned to increase the volume of the buffer chamber.
3.”Crawling” in the buffer stroke section
Fault manifestation: The piston movement is discontinuous, and there is shaking or jamming.
Cause and solution:
- Insufficient processing accuracy: The verticality of the cylinder head and the piston end face is out of tolerance, and qualified parts need to be replaced.
- Assembly eccentricity: Re-adjust the fit of the buffer plunger and the hole to ensure coaxiality.
- Poor lubrication: Check the cleanliness and viscosity of the oil, replace the appropriate hydraulic oil and clean the system.
4. Buffer failure caused by external leakage
Cause and solution:
- Aging or damage of seals: Replace seals with good oil resistance and ensure the correct installation direction.
- Piston rod strain: Repair the surface roughness to Ra0.2μm, and install a dust ring to prevent impurities from invading.
- Installation deviation: Correct the parallelism of the hydraulic cylinder and the guide rail to avoid eccentric wear of the seal.
Article from Nancy Zhu, Sales manager, JW GROUP.
Email: nancy@jwgroup.cc
Mobile/Whatsapp:+86 15902166721
HYDRAULIC CYLINDER and CNC parts specialist
JW GROUP is an integrated steel product group, products include: hydraulic cylinder, hydraulic cylinder spare parts, drilling forging parts, pneumatic actuator-scotch yoke, CNC machinery parts etc.