Selecting Servo and Position Cylinders
A position cylinder must not only push, it must hold a set point and return to it repeatably. The feedback sensor, friction, sealing type and the stiffness of the oil column decide the accuracy you can reach. This guide shows which criteria really matter for servo and position cylinders.
View hydraulic cylindersWhich feedback sensor fits the positioning task?
Without position feedback there is no closed-loop control. A magnetostrictive sensor inside the piston is wear-free, absolute and delivers resolution down to the micron range. Potentiometric sensors are cheaper but wear over time. For high dynamics and long strokes the integrated absolute system is usually the most robust choice.
How do friction and sealing affect accuracy?
The main enemy of fine positioning is the stick-slip effect: the piston grips, then jerks free. Low-friction seals and a good surface finish on the rod keep static friction low. For very fine motion, prefer cylinders with especially low-friction guides and lip-type seals.
- Low-friction seals with a PTFE element reduce stick-slip.
- A fine rod surface finish lowers break-away forces.
- Preloaded guides cut play under load reversal.
- A stable oil temperature keeps viscosity and friction constant.
Why does stiffness decide control quality?
The oil column behaves like a spring. Short lines, a matched piston diameter and low dead volume raise the hydraulic stiffness and with it the natural frequency of the axis. A high natural frequency allows tighter control gains and faster, stable positioning without overshoot.
Frequently asked questions
What sets a position cylinder apart from a standard cylinder?
A position cylinder is built for closed-loop motion: an integrated feedback sensor, low-friction seals and a stiff construction. That lets the controller reach and hold any position repeatably, instead of just travelling between end stops.
What oil cleanliness does a servo cylinder need?
Servo valves are sensitive to particles. A filtration rating around 5 µm and an ISO 4406 cleanliness class specified by the valve maker are common. Dirty oil causes wear, sticking and position drift.
Why does the axis jitter around the target position?
Usually stick-slip from excessive friction, trapped air in the oil column or control gains set too tight are behind it. Bleeding the system, low-friction seals and control tuned to the natural frequency solve it.
Find the right position cylinder
Our hydraulics specialists help with feedback sensor, sealing and valve for your positioning task.
Repeatable
Feedback sensor matched to the required accuracy.
Clean hydraulics
Filtration rating and oil cleanliness clearly explained.
Stable control
Stiffness and natural frequency sized correctly.
Expert advice
Hydraulics specialists support the sizing.