End-of-stroke cushioning slows the piston down in the final section of its stroke by gradually restricting the outgoing oil flow.
The kinetic energy is dissipated in a controlled way and the cylinder reaches the end of its stroke without mechanical shock, which extends the service life of both the cylinder and the machine.
On Conforti hydraulic cylinders the cushioning effect is adjustable via the adjustment screw, which also serves for air bleeding.
What cushioning does and how to integrate it into the machine
Cushioning brings the load to a stop by slowing it down gradually before it reaches the end of the stroke. When the piston enters the cushioning section, the outgoing oil flow passes through an adjustable restriction. The kinetic energy of the mass connected to the rod is dissipated in a controlled way before the piston reaches the head. This protects the heads from violent end-of-stroke impacts, one of the main causes of fatigue failure due to the high impulsive loads that can occur.
How it is built: floating ring, hardened cushions, adjustment screw
The Conforti system is based on a floating cushion ring in hardened steel. The ring self-centres in relation to the head and acts as a quick-opening valve on the return stroke, so the cylinder restarts from the end of its stroke at full speed. The cushions work against the steel seat of the head, a coupling designed to last. The cushioning effect is adjusted with a calibrated needle, locked by a Seal-Lock® sealing nut. The same assembly also acts as an air bleed. On ISO 6022 heads the needle is protected against accidental removal. At the design stage, place it in the most suitable and accessible of the available positions, so it is easy to adjust during commissioning and maintenance. The configurator shows the available positions for the oil ports and cushion adjustment screws.
When to specify it and on which side
The choice depends on the combination of mass connected to the rod, speed and cycle frequency, so each application must be assessed in its own context. Adjustable cushioning is very useful in high-speed applications, where it absorbs end-of-stroke impacts and protects the mechanical structure, and when the machine requires the load to be slowed down gradually before stopping against an external stop. Adjustment allows it to be precisely matched to the loads to be decelerated.
V, front cushioning: acts on the front head (rod end) at the end of the extension stroke.
Z, rear cushioning: acts on the rear head at the end of the retraction stroke.
K, front and rear: for end-of-stroke deceleration in both directions of the cycle.
Cushion length and cushion area: key design data
Cushioning acts in the final section of the stroke over a fixed length, which depends on the series and the bore. When the cylinder stroke is shorter than the cushion length, the cylinder is cushioned along its entire stroke. In these cases the Conforti technical department is available to work with you on the most suitable solutions. The cushion area is the effective area that generates the cushioning force when subjected to the cushioning back-pressure created by the restriction.
Bore | ISO 6020/2 CD/DK/MD/HD/HK series | ISO 6022 DP series | ||
Cushion length | Cushion area | Cushion length | Cushion area | |
25 mm | 12 mm | 1,8 cm² | - | - |
32 mm | 14 mm | 3,5 cm² | - | - |
40 mm | 23 mm | 5,5 cm² | - | - |
50 mm | 21 mm | 8,3 cm² | 32 mm | 8,2 cm² |
63 mm | 21 mm | 13,8 cm² | 32 mm | 13,8 cm² |
80 mm | 28 mm | 23,8 cm² | 40 mm | 23,8 cm² |
100 mm | 28 mm | 38 cm² | 40 mm | 37,8 cm² |
125 mm | 26 mm | 56 cm² | 40 mm | 56 cm² |
160 mm | 30 mm | 99 cm² | 46 mm | 99 cm² |
200 mm | 44 mm | 151 cm² | 65 mm | 151 cm² |
ISO 6020/2 tie-rod and bolted-flange cylinders
The ISO 6020/2 CD/DK/MD series tie-rod hydraulic cylinders and the ISO 6020/2 HD/HK series bolted-flange cylinders offer adjustable cushioning at the front, rear or both heads, with a floating ring and hardened steel cushions. Every cylinder is tested to ISO 10100 before delivery.
ISO 6022 cylinders
The ISO 6022 DP series heavy-duty hydraulic cylinders offer longer cushion lengths for the same bore.
Configurator and kits
With the Conforti hydraulic cylinder CAD configurator, you choose the cushioning while building the code, and the 2D/3D CAD model is ready to download straight away. Heads with or without cushioning and floating-ring cushioning systems are also available as assembly kits for hydraulic cylinders.