Piezo Stack Actuator

Piezo: Your Premier Piezo Stack Actuator Manufacturer

The piezo stack actuators have been exploited in a number of useful applications including nanopositioning, dynamic scanning system, metrology, aerospace technology and so on.

PD Ceramic is one of the most trusted and competent participators in the piezo stack actuator OEM market since we have concentrated our frontier technology of piezo stack actuator for the precision positioning tasks worldwide for over the past 20years.

And the piezo stack actuator has proven to be reliable in this domain, alongside our rich experience in the industry. PD Ceramic is flexible and guarantees a long service lifespan, making it 100% suitable for many projects.

If you need more piezo stack actuator information, please feel free to contact us for further discussions.

Piezo Stack Actuator (stacked piezo actuator) can be provided with attached wires.

Piezo Stack Actuator (stacked piezo actuator) is completely vacuumed compatible.

Piezo Stack Actuator (stacked piezo actuator)are fully cryogenic compatible.

Piezo Stack Actuator (stacked piezo actuator)can be in customized dimensions and thickness.

Piezo Stack Actuator (stacked piezo actuator) can have customized wiring and connectors.

Piezo Stack Actuator (stacked piezo actuator) can be customized according to your mounting platform design and fabrication.

Piezo Stack Actuators: The Complete Guide by Method and Principle

  For the designers and engineers to achieve complex functions and exceptional performance levels, they must think outside the conventional engineering solutions in every aspect of their advanced systems.

This includes the actuator system as well as the systems where the classical solution may or may not be able to successfully meet the high working requirements.

A relatively unconventional approach taken by the engineers in the actuator system is the use of piezo stack actuators.

What are piezo stack actuators?

Piezo itself is a type of ceramic that can expand and contract when electrical energy is provided to the system.

The application of electric charge results in force and motion. If looked other way around, piezo materials can generate energy when enough mechanical stress is applied to the system.

Piezo actuators harness this motion to provide the system with short strokes of high frequency in a relatively very small amount of time.

Piezoelectric actuators are also capable of producing high forces relative to their size, which gives the piezo stack actuators with a significant power-to-size ratio.

Type of Piezoelectric Actuators

There are two main types of piezoelectric actuators. The stack actuators and the stripe actuators.

Stack actuators (piezo stack)

The stack actuators, also referred to as piezo stack actuators offer a high blocking force and low stroke.

Based upon the requirement of the user, the piezo stack actuators can be co-fired or discrete.

The Discrete piezo stack actuators are also called high-voltage stack actuator.

They are composite structures that are made by the stacking together separately finished piezoelectric rings or discs and metal electrode foil adhered together using a strong adhesive.

The operating voltages range from 500V through 1000V. On the other hand, the co-fired actuators also commonly referred to as monolithic stacks involve no use of any sort of adhesive.

They use high-temperature sintering to adhere to the electrode pile or complete ceramic.

The operating voltages of the co-fired stack are up to 200V. The co-fired actuators usually have rectangular cross-sections due to the ease of cutting processes in the production.

Both co-fired, and discrete stacks can be easily insulated using a coating material (a bare stack) or in stainless steel in case of protection from external mechanical stress and or environmental extremes.

Strip actuators

The stripe actuators are two layers of thin piezoelectric ceramics that are strongly bonded together.

The bonding of the ceramics is done usually in the direction of the polarization coinciding and are electrically connected in parallel.

When the electrical charge is supplied to the strip actuators, one layer of ceramic expands whereas, the other layer of ceramic contracts. This motion causes the actuator to flex and operate.

Principles of operation

Piezoelectric actuators work, and function-based over the piezoelectric effect. The ‘direct piezo effect’ implemented for example in piezoelectric force sensors represents the generation of electric charge.

This results in the effect of mechanical strain-induced over the system. The actuators are based on the reverse effect where the electrical field is parallel to the direction of the polarization which determines the elongation in the system with respect to the same direction.

The electric field generates a torque on the electrical dipoles that are found in the structure of the material which is then aligned along the field. This results in the change in the length of the mono-crystalline partitions.

The dipoles aligning in the electrical field

  In the natural monocrystalline materials, such as Rochelle, salt, tourmaline and quartz, the piezoelectric effect has quite low ampleness.

Therefore, with the advancement in technology, synthetic polycrystalline ceramics materials such as lead zirconate titanate (PZT) have been developed.

These materials have better piezoelectric properties and have high ampleness. These synthetic polycrystalline ceramics are produced in many different variants and are employed in piezoelectric actuators developed today.

The piezo stack transducers are a type of actuators that have a change in their length when they are subjected to an electric field. The elongation is directly dependent on the type of ceramic material employed, its actual length, the intensity of the electric field and the force acting over it.

The formula to summarize this elongation can be described as follows;   Where; ∆L  = the change in length (m) L   = the length of the transducer (m) E   = the electric field intensity (V/m) d_ij   = the constant of the material (m/V) C_T  = the elastic constant of the material (N/m)   The maximum elongation of the piezo stack actuator is limited by the intensity of the supplied electric field at which the actuator can be subjected without being destroyed by the tension shocks in the system.

The limits are usually around 1-22 kV/mm. The behavior of the piezo stack actuator can be recognized by the type of strain it is subjected to. There are two instances. The constant load and variable load.

Constant load (F constant)

Under this instance, the force exerted by the weight remains constant during the complete elongation process.

As the elongation capabilities of the actuator are not affected by the load, the maximum elongation will be the same as the piezo stack actuator is not mechanically stressed, however, the zero points of the position domain will be displaced down with the constant load applied on the system. This case is demonstrated in the image below;   Piezoelectric actuator under constant load

Variable load (F is as a function of the elongation)

Under this instance, the force applied to the system is dependent on the elongation of the piezo material. All the applications where the positioning element acts over an elastic wall or a spring are under the variable load category.

The more the rigid the spring or elastic wall, the higher the elastic constant C_S therefore, the less the travel of the actuator. This case is demonstrated by the image below.

Piezoelectric actuators under a variable load

The actual elongation of the piezo stack actuator can be determined by the following expression;

The above graphical representation shows that the elongation of the actuator if not linear with the supply voltage but is a hysteresis curve as the voltage rises or decreases. The hysteresis phenomenon is determined by the crystalline polarization effect.

Dynamic behavior

A piezo stack actuator can reach it’s full elongating in a time that is equal to the one-third of the resonant frequency cycle.

The resonant frequency of the unstressed actuator is in the range of micrometers and is around several tens of kHz. Any supplementary load will automatically lower the resonant frequency as per the following expression;

The actual value of the mass can be calculated using the expression below;

The unloaded piezo stack actuator as compared with the loaded piezo stack actuator

Tensile strength and preload

The piezo stack actuators are often subjected to tensile or compressive forces especially during the highly dynamic movements.

The length of the piezo stack actuator is determined by the technique that is used in the bonding of the elements together and usually is an order of magnitude that is lower than the compressive strength of the materials.

By preloading the piezo stack actuator to a value that is greater than the applied tensile load, it is ensured that the stacked actuator will always stay under some compression and therefore, can operate under highly dynamic, bi-directional application.

Successful integration in the system requires that any load or forces applied are axial and compressive only.

Manufacturers of piezo stack actuators usually offer a wide array of different mounting options to help prevent any torsional, shear or bending forces. Preload, either internal or external to the actuators ensures a suitable tensile strength

What are the key benefits of piezo stack actuators?

Piezo stack actuators have several benefits some of which are discussed below;

1. Piezo stack actuators have an unlimited theoretical resolution which often resolves to a sub-nanometer value. This means that the piezo stack actuators can detect and convert motion by the smallest changes in the supply voltage without ever stepping or skipping.
2. During the operation of piezo stack actuators, no magnetic field is generated.
3. In the operation of piezo stack actuators, high actuation forces can be generated easily without any loss in precision. For example, extremely high loads such as of 10,000 Newtons can easily be positioned with a micrometer accuracy using piezo stack
4. Piezo stack actuators have a high response time. They usually have response times of under one millisecond.
5. A piezo stack actuator has no moving parts at all such as bearings or gears. Their displacement is based directly over their crystalline solid-state dynamics where there is no wear and tear.
6. The piezo stack actuators are a vacuum and cleanroom compatible since they do not require any lubrication and causes no abrasion. This makes them ideal to be used under ultrahigh vacuum applications.
7. Piezo stack actuators have very low power consumption as the piezo effect can directly convert the input energy into motion. Under static operation, they can hold heavy loads for extended periods of time with virtually no power. A piezo stack actuator behaves very much like an electrical capacitor. When the piezoelectric actuator is at rest, there is no heat generated.
8. Piezo stack actuators have a high stiffness as these types of actuators are structural actuators.
9. The piezo stack actuators have a unique form factor and are therefore scalable down to very small dimensions.
10. Piezo stack actuators have a low drive voltage (150V).
11. Piezo stack actuators have a multi-functional performance, and their sensing and actuating capabilities can be used for stress, strain, and acceleration.
12. Due to no mechanical parts, the piezo stack actuators have a long life. They are known to work for up to 10¹⁰ cycles without any changes in their behavior.

Industrial applications of piezo stack actuators

Due to the characteristics of piezo stack actuators, they are quite popular in several domains such as;

1. Optics and measurement systems – the piezo stack actuators are employed in the positioning of mirrors, holography, rapid screening, interferometry, laser sweeping, image stabilization, and active adaptive autofocus.
2. Microelectronics – the piezo stack actuators are used in inspection and control systems, mask positioning and microlithography.
3. Medicine – the piezo stack actuators are used in physiological stimulations, micromanipulation and microsurgery, micro-dosing systems and cell penetration.
4. Precision mechanics and mechanical engineering – the piezo stack actuators are used in the adjustment and extrusion tools, piezo hammers, micropumps, micro-bots, active vibration cancellation systems, micro-etching, tools injection nozzle control and correction of wear systems.
5. Ultrasonic welding – Piezo stack actuators are used in ultrasonic welding. Many different plastics can be joined together using this process and the actuators play a crucial role in focusing the welding region to a single point.
6. Wearable technology – piezo stack actuators are now one of the major components in wearable technology. They are used in smart-watches and electric fitness bands where they are used to capture the vibrations caused by the motion and then store it for future use.
7. Sonar equipment – sonar systems rely heavily on the piezo stack actuators to transmit and receive sonar “pings”. Piezo stack actuators apart from having an ideal frequency response from sonar application (50-200kHz) have a high-power density that allows for large amounts of acoustic power to transmitted for the sonar application in small packages.
8. Diesel fuel injectors – with the regulations on the emissions from the diesel engines becoming increasingly stringent, the car manufacturers make use of piezo stack actuators to precisely time and meter the diesel injections during the combustion process. The precise movement of the actuator makes the emissions levels to below with very little compromise in the power.
9. Ultrasonic cleaning – piezo stack actuators are used in the ultrasonic cleaning of many solvents that requires intense cleaning.

High-quality piezo stack actuators from PD Ceramic R&D Co., Ltd

At PD Ceramic, we excel and specialize in meeting the piezo stack actuator needs of our customers.

Across every step of our manufacturing process, we are here to get the right piezoelectric actuator for your need. Our staff and manufacturing team is highly skilled, trained, experienced and supportive throughout the designing, constructing and testing of the piezo stack actuators for our customers.

We understand your needs and are every ready to assist you in choosing the right piezoelectric device for your need.

Our philosophy is that when you choose Height Piezoelectric, all your Piezoelectric needs must be met with the right met in a cost-effective and time-sensitive manner.

To learn more about our full line of piezo Stack actuators, contact us today.