PIRest Actuators

Active Shims with Long-Term Stability and Nanometer Resolution

Applications

Applications for active shims can be found everywhere, where the alignment between two subassemblies is critical and needs to be realigned as a consequence of drifting or changes in tolerance of machine parts. Particularly when the ambient conditions and the accessibility make manual intervention complicated, PIRest actuators are a feasible option

  • For qualification and calibration of a machine
  • During first installation of machines at the customer's location
  • Realignment as a consequence of temperature drift
  • During realigning due to changed dimensions of subassemblies, for example

Due to the high resolution of the actuator within a few nanometers, not only applications are included in classical mechanical engineering, but also alignment of optical components in astronomy, or material research in synchrotrons, and in semiconductor manufacturing, for example.


Completely New Piezo Technology for Active Adjustment of Consistently Stable Gaps

When a target or actual gap between two components in a machine changes, it could be necessary to adjust it.

The disadvantage of classical flat washers that are ground exactly to the required gap, is that they need to be inserted mechanically. It is not always possible to adjust them as finely as required and the predefined gap cannot be changed any more.

This is different in the case of the piezo-based PIRest active shims, which only need to be inserted once and can actively adjust or readjust the gap between two components.

Conventional piezoceramic actuators were not suitable for this purpose. The electrical voltage (offset voltage) at the actuator needs to be maintained as long as the displacement is required – a considerable disadvantage for the lifetime of the actuator and the equipment of the machine, which also requires an additional and stable power supply.

Although the PIRest technology is based on piezo actuators, it nevertheless maintains a stable displacement with nanometer accuracy after adjusting even without offset voltage.


Easy to Use

The active shims are already designed into the machine during the initial construction. They can be made in virtually any shape and size and integrated almost anywhere – as plates or rings or even complex hybrid drive components that actively compensate vibration beyond static adjustment or perform other motion with nanometer accuracy.

To readjust the static gap, a voltage connection is provided for the active shim, which only needs to be connected to a voltage source for the respective adjusting process. PI offers a mobile power supply for this adjusting process that makes setting very easy.

This considerably simplifies adjustment at inaccessible places because any cables required can be considered during the design of the machine and therefore routed permanently in the system.


The Advantages of PIRest at a Glance

  • No permanent voltage required to hold the position. Saves costs during initial installation and makes adjustment much easier
  • Flexible shapes and functions. The manufacturing process for PIRest actuators is largely identical to classical piezoceramic actuators, which PI can already produce in large quantities, and is also in a position to shape them according to customer specifications
  • High reliability and long lifetime of the piezo actuators
  • Travel ranges up to 10 µm as standard product (longer travel ranges possible with custom products)
  • Nanometer resolution, micrometer displacement. PIRest have the same classical properties as piezoceramic actuators
  • Long-term position stability
  • Easy adjustment of the displacement, e.g., with a handheld device
  • Hybrid actuators with the capability of adjusting over several millimeters or compensating vibration dynamically
  • One to six-axis versions are possible. Optional temperature sensor for the actuator

Long-Term Stability

Tests at PI have demonstrated that the stability of the displacement of PIRest actuators depends only on changes in the ambient temperature. Using an actuator with 10 µm nominal adjustment range, long-term tests indicated a position drift of less than ±100 nm in a temperature-stable environment that does not deviate by more than 1 K.

Nanometer Resolution

The system, consisting of a PIRest actuator and a manual control device, can generate changes in length of a few nanometers irrespective of the load.


Flexibility Due to Different Shaping

 

Different Lengths and Form Factors

 

The displacement is dictated by the length of the actuator. Simple single-axis actuators with displacements up to 10 µm are available as standard. Generally, the PIRest technology can be manufactured in all form factors available in the PICMA® series product portfolio for multilayer piezo actuators.

Flexibility Due to Hybrid Actuators

 

Hybrid actuators consist of a classical and a PIRest piezo actuator. While the PIRest actuator part corrects the position permanently as described, it is possible to use this as a basis for performing dynamic motion via the classical actuator. This can be helpful for dynamic compensation of vibration in a range of several tens of Hertz or for realignment of a focal plane during a measuring or scanning process, or for controlling a laser beam in metrology or material processing.

Hybrid PIRest actuator

(available as custom product)

PIRest active shim (blue)

Adjustment range: 4.6 μm

PICMA® actuator (yellow)

Adjustment range: 5 μm

Resolution: <50 pm


Adjustment in up to Six Axes

Alignment of the machine subassemblies does not necessarily take place in one dimension with respect to its final position. Despite two-dimensional planar adjustment of components, a six-dimensional alignment includes all spatial angles, therefore allowing optimized positioning.

Thanks to sophisticated arrangement of the individual actuators, PIRest technology allows parallel-kinematic, multi-axis actuators in one single design.