Features of all pneumatic grips
- The separation of tensile and gripping forces ensures a constant gripping force over the course of the entire test sequence. For specimens prone to shrinkage, the gripping force is uniformly maintained by constant pneumatic pressure.
- The contact force on the specimen is reproducible.
- Gripping-sensitive specimens can be held securely by adjusting the pneumatic pressure, avoiding jaw breaks.
- The primary stress is the tensile load and it can be static or pulsating. Depending on the type of grips, compression and alternating load tests may be performed.
- Depending on the design principle, the gripping area is freely accessible.
- The larger grips can remain in place while small load cells, specimen grips, test fixtures and test devices are attached without having to dismantle the specimen grips—a great time saver.
- There are a wide range of jaws with respect to material, surface, and area of the clamping surface.
- Pneumatic grips offer a low-cost alternative to hydraulic grips.
Differentiation into three types
There are three types of ZwickRoell pneumatic grips:
- Single-actuator
Single-actuator pneumatic grips can be used for the symmetrical and asymmetrical gripping of specimens (e.g., for shear strength tests). Some of the single-actuator pneumatic grips up to 1 kN have an integral control valve—no additional external pneumatic control unit required. - Double-actuator
Double-actuator pneumatic grips always close symmetrically with respect to the tensile axis. This eliminates the need for thickness adjustment: This is a big advantage, above all, for soft specimens and/or if specimen thickness changes. - For temperature chambers (single- and double-actuator)
These pneumatic grip are single- or double-actuator specimen grips that are specifically designed for use in temperature chambers.
Differentiating between two versions
Pneumatic closing and gripping
- For specimen grips that close with pure pneumatic actuation, the closing motion only occurs as long as the closing button is activated. If the button is released during the closing process, the specimen grip automatically switches back to the safe, open position. The position is only held after the specimen grips are fully closed. The preset gripping pressure is only applied once the test starts. All pneumatic grips are available in this version.
Spring-closing and pneumatic gripping
- Spring-closing specimen grips feature a technological difference between closing and gripping. With a brief touch of the closing button, the built-in spring closes the specimen grips very quickly with a low force of < 150 N. The specimen is therefore quickly clamped and operating times are reduced. The preselected gripping pressure is applied when the test starts. Seven selected specimen grips in a force range ≤ 2.5 kN are available in this version.