Question 1

Which hydraulic cylinders are suitable for a test rig or testing frame?

Accepted Answer

For test rigs and testing frames the usual choice is the tie-rod CD / DK cylinders to ISO 6020/2 (160 bar, tested at 240 bar, Ø 25–200 mm). The rigid tie-rod construction maintains a precise axial force under repeated loading. If the testing frame requires position feedback to the PLC, the MD / MP series with a magnetic piston is used.

Question 2

How does a cylinder ensure a repeatable clamping force in hydraulic workpiece clamping?

Accepted Answer

The clamping force of a cylinder is given by the system pressure and the piston area, so at constant pressure the force on the workpiece is repeatable from part to part. CD / DK cylinders work up to 160 bar and, thanks to the bronze guide bushing and quality seals, hold the force stable even after many cycles — which is crucial for clamping and positioning fixtures.

Question 3

How does the MD / MP series help control a clamping or testing cycle via the PLC?

Accepted Answer

The MD / MP series has a magnetic piston and magnetic position sensors — on MD on the tie rods (adjustable along the stroke, intermediate as well as end positions), and on MP in the profile groove: SH are PNP magnetoresistive sensors, 6–30 V DC, and SR are reed sensors, 3–110 V AC/DC. The signal that the clamped or home position has been reached goes straight to the PLC, so the control system knows that the workpiece is clamped or that the test has reached its end position.

Question 4

Why is adjustable end cushioning important on testing and clamping cylinders?

Accepted Answer

Adjustable end cushioning catches the piston as it arrives at the end of the stroke and prevents hard shocks into the tester frame and the clamped fixture. On test rigs it protects the measuring system from vibration; in hydraulic clamping it softens the seating of the clamp on the workpiece. The cushioning is set according to the mass and speed of the load.

Question 5

Will the cylinders withstand cyclic loading in fatigue testing?

Accepted Answer

For fatigue testing, the cyclic life of the seals and guides is decisive. Conforti cylinders have a bronze rod guide bushing and a chrome-plated rod, which reduce wear over a large number of cycles. For high cycle frequencies we recommend the low-friction seal (L); consult the specific cycle count according to stroke, load and medium.

Question 6

Which cylinder should be chosen for a clamping fixture in a confined space?

Accepted Answer

Where space is scarce — compact clamps, fixtures on the machine table, positioning units — the compact RP / MP series is suitable. It has a shorter envelope than the tie-rod cylinders, and the MP version allows position monitoring with magnetic or IO-Link sensors. For higher clamping pressures and more demanding conditions there is the steel compact RQ series up to 250 bar with proximity end-position sensors.

Question 7

Which seals should be chosen for testing and clamping applications?

Accepted Answer

For static clamping with a long force hold, the high seal (S) is suitable; for fast cyclic testing, the low-friction seal (L), which reduces stick-slip and wear. Viton (H) is available for high temperatures and the G seal for HFC water emulsions. Metal scraper rings can also be added for contaminated workshop environments.

Question 8

Is every cylinder pressure-tested before delivery?

Accepted Answer

Yes. Every cylinder undergoes a 100% functional and pressure test at 240 bar in accordance with ISO 10100. For testing and clamping equipment this is essential — you have the certainty that the cylinder which itself performs tests or holds a workpiece is tight and reliable from the first cycle.

Question 9

Why do the cylinders have a bronze rod guide bushing?

Accepted Answer

The bronze rod guide bushing reduces friction and prevents seizing even under the side loading that often arises on clamping fixtures and testing frames. It protects the rod from scoring, maintains guiding accuracy and extends seal life under repeated cycling.

Question 10

Can CD / DK cylinders be used as a replacement for Parker or Bosch Rexroth in an existing tester?

Accepted Answer

Yes. CD / DK cylinders comply with ISO 6020/2 (DIN 24554), which defines a uniform envelope and mounting dimensions. In test rigs and clamping fixtures they can therefore directly replace Parker Hannifin, Bosch Rexroth or Festo cylinders without modifying the frame or the fixture.

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Testing and clamping cylinder FAQ