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 dimension between two components in a machine changes, it could be necessary to realign that dimension.

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

In contrast to the classic approach, the piezo-based PIRest shims, which only need to be inserted once, can actively adjust or readjust the dimension that has changed between the two components.

Conventional piezoceramic actuators were not suitable for this alignment process. 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 adjustment, even without an 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 adjustments or even perform other motion tasks with nanometer accuracy.

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

This considerably simplifies alignment tasks at unreachable positions because any cables required can be designed into the machine and therefore routed permanently.


The Advantages of PIRest at a Glance

  • No permanent voltage supply required to hold the position. Saves costs during initial installation and makes adjustment much easier
  • Flexible shapes and functional elements. The manufacturing process for PIRest actuators is largely identical to classical piezoceramic actuators, which PI both produces in large quantities, and is also capable of shaping according to customer specifications
  • High reliability and long lifetime of the piezo actuators
  • Displacements up to 35 µm as standard

   

  • Nanometer resolution, micrometer displacement. The PIRest technology has the same classical properties as conventional piezoceramic actuators
  • Long-term position stability
  • Easy adjustment of the displacement, e.g., with a handheld device
  • Hybrid actuators with the capability of adjustments over several millimeters or dynamic vibration compensation
  • One to six-axis versions are possible. Optional temperature sensors at the actuator

Long-Term Stability

The displacement stability of PIRest actuators only depends on a change of the ambient temperature. Long-term tests in an environment within ±1 K temperature change using an actuator with 10 µm nominal adjustment range indicated a position drift of less than ±100 nm, irrespective of the displacement.

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.


Product Overview

Flexibility Due to Different Shaping

The displacement is dictated by the length of the actuator. Simple single-axis actuators with displacements up to 35 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.

PIRest 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.