Piezo Stack - Precaution

 

Before using our products or designing a system using our products, read the precautions and specifications for the products you intend to use. 


The products are extremely reliable with proven life of more than 10¹⁰ cycles. Nevertheless, environmental influence and misconceptions in the design phase may lead to failures in application. The main failures with piezoelectric actuators are cracking of the ceramics monolithic block, short-circuit, and open-circuit. 
Before using the products, also consider safe design praxis of electrical engineering. Carefully ensure prevent electric shock, cause and spread of fire. Use the products after checking the working conditions and rated performance of each of the multilayer piezoelectric actuator series. Stay within mechanical, thermal and electrical, and environmental limits.

 

Mechanical Precaution

 

·       Be careful with the mechanical handling of piezo stack

• Do avoid tensile, torsion, shear and bending stress.
• Do not exceed rated voltage limits. Be careful in bipolar electrical operation mode and recognize reverse voltage limits.
• Do not handle the product by picking up or moving the lead wire.
• Align the centre axis of displacement of the actuator with the centre axis of the mechanical load.

• Avoid tensile, twist, shear and bending stress.
• Do not disassemble the case of the housed or metal sealed type.

• Machining of the actuator element and replacement of the lead wire are prohibited.

• Avoid excessive physical shock resulting from, for example, dropping. Otherwise, the internal piezoelectric ceramic element may be damaged.

• Store actuators where there is no vibration.  

Thermal Precautions and Ambient Conditions for Piezo Stack

• Note the ambient conditions
• Do not overheat.
• If the actuator is exposed to high temperature above 100°C or if it is used after long storage period (more than three months), it should be polarized by using the circuit configuration and conditions shown in the paragraph “Polarization”.
• Do not handle the resin-coated type with bare hands. In that case carefully clean the stack with pure Isopropanol alcohol. Otherwise, the reliability of the element would be degraded.
• Do not wash stacks with organic solvents.

• Do not use the actuator in high concentration of highly inflammable gas. Otherwise, ignition may occur.
 Use the actuator so as not to cause bending, twisting or tension.
• Store actuator preferably in a dry atmosphere (desirably below 40% RH) at ordinary temperatures (- 5 to + 40 ̊C).
• Avoid condensation on the product surface.

• These products must be handled properly as industrial waste. When disposing, please contact your local waste disposal service.
 Piezo actuator is industrial wastes, make sure disposal method under the laws.

 

Electrical Handling of Piezo Stack

 

• Carefully setting up the electric power supply. Avoid abrupt voltage jump during switch-on.
• Do not rapidly charge and discharge the actuator. These might lead to degradation of the reliability or mechanical fracture.
• Connect the red lead wire to the positive (+) terminal of the power supply.
 Connect the black lead wire with the negative terminal (-).
• Carefully avoid electric shock since a high voltage is in use.
 Never apply excessive mechanical tension to a lead wire.
• Operational procedures
• Drive the actuator so that the rising speed is more than three times as much as the resonance period (stack plus load) in order to prevent the device from damaging by mechanical overshoot.

• This, do avoid steep voltage transients e.g. during switching the amplifier on or off. Check carefully the switch-on behaviour of your circuit whether the power supply steep voltage transients to the actuator. Steep voltage steps cause high acceleration, which cause high internal tensile stress amplitudes to the actuator material. Dynamic operation of piezo actuators requires proper mechanics to provide sufficient pre-stress (see previous chapter). The pre-stress shall be sufficiently dimensioned to fully compensate tensile stress static and dynamic loads.

Polarization of Piezo Stack

 

In case the actuator was exposed to higher temperature during storage or operation clos or above the Curie temperature, the piezo material may loose its polarization. In this state, the piezo effect is weakened or non-existent. The polarisation procedure requires a voltage source. A standard Piezotechnik amplifier can be used in combination with a signal source to set the output voltage. The voltage should be ramped up to 150 +/-  0.2V and retained for 10s and than ramped down to 0V.