Robert Campbell reveals why piezoelectric jet valves represent a worthwhile investment
In many high-volume production environments where adhesives and fluids are used, there is a continuous drive for faster dispense rates, higher throughput and profitability. This creates a need for advanced dispensing technologies that can achieve all the above whilst providing highly accurate results. High-speed piezoelectric jet dispensing is a powerful alternative to traditional dispense valves and could fulfil these requirements with ease.
High-speed jet valve dispensing is a relatively new and innovative technology that can dramatically increase dispensing rates of adhesives and other fluids. A non-contact dispensing method, high-speed jetting is the process of material being shot from a fixed location onto the desired substrate with outstanding consistency and repeatability. As the jet valve never comes into contact with the surface, there is a much higher degree of dispensing flexibility, meaning it can be used in a wider variety of applications. Piezoelectric jet valves can dispense at approximately twice the speed of standard, pneumatic jet valves. Despite moving at such high rates, users of piezo jet valves are often amazed at how precisely and accurately they can dispense small, neat dots or lines. High-speed jet valves are operated via a sophisticated dispense controller. This controller helps optimise the dispensing process as it provides a clear overview of all components and their status throughout the entire operation.
How high-speed piezoelectric jetting works
The high-speed functionality of the valve is initiated by the advanced piezoelectric ceramic technology. In fact, piezoelectric jet valves can operate at continuous speeds of up to an impressive 1,200Hz and burst speeds of up to 2,000Hz. Rather than relying on air pressure, the piezoelectric actuator within the valve converts an electric signal into a highly precise cycle to dispense material. High-speed jet valves with this technology can achieve very fast open and close cycles that jet fluids onto the desired substrate. The piezo actuator is composed of two stacks of ceramic discs that change shape as voltage is applied. This creates a deflection in the cantilever arm, causing the actuator stem to lift at a fixed stroke. When the ceramic ball lifts off its ceramic seat, the resulting cavity fills with fluid. Then, as the ball reseats, a fluid droplet is ejected from the valve. This process is repeated up to 1,200 times per second, each time carefully dispensing a precise dot of material at the target location. The high speed achieved by this ball and seat movement simply cannot be attained when using air or spring actuated valves.
Additionally, jet valves gain a significant speed enhancement over pneumatic valves as they eliminate the Z-axis of movement. The Z-axis is traditionally equipped with height and position sensing devices and operates in an “up and down” motion. In contact-based dispense valves, this combination allows the needle to move down to touch the substrate and dispense the fluid before being pulled back into start position. In contrast, high-speed jet dispensing is contactless and shoots the material repeatedly at a fixed location above the substrate. As users do not have to monitor and reposition this axis after each dispense application, they can save valuable production time and therefore achieve much higher dispense and turnover rates.
Benefits of high-speed piezoelectric jetting
High-speed jet valves offer several key advantages over traditional, contact-based dispensing methods. High-speed jetting does not rely on actual contact with the substrate as the material is shot rather than physically placed. This allows for materials to be easily dispensed into conventionally hard to reach areas, as well as those that are uneven or irregularly shaped. The needle does not need to be dropped down onto the substrate meaning it can be easily angled to reach the desired dispense point and prevent any possible surface damage or waste of materials. This ability to dispense into narrow spaces is an important feature for electronics manufacturing processes such as underfills. Jet valves operate at a fixed stroke with no manual movement, which not only makes them extremely fast, but also increases process control. As jet valves do not require any Z-Axis motion device equipment, the overall setup costs are reduced and it removes the need for specially trained operators. Furthermore, contact dispensing applications require surface tension to pull the fluid from the needle tip. The contact-free properties of high-speed jet valves eliminate this obstacle and provide a much cleaner cut off.
High-speed valves allow operators to deposit very small and precise amounts of fluid with extremely accurate product placement. Micro dots can be achieved as small as 0.5nl, which is extremely useful for users who would traditionally struggle to achieve ultra-small dots consistently over time. For example, piezoelectric jetting is a popular choice within industries such as microelectronics, medical and automotive as operators can easily deposit these very small and precise fluids onto their substrates with improved efficiency. In addition, jet valves can create a range of dispense patterns that would not be possible with needle dispensing. From jetting multiple shots in the same location to increase dot size, to jetting fluids vertically, horizontally or in an inverted position, jet valves give operators much greater design control.
Although implementing the cutting-edge technology of piezoelectric jet valve dispensing is initially more expensive in comparison to contact-based systems, it is much more robust and requires fewer replacements and less maintenance during its lifecycle. The ability to produce accurate and repeatable shots is primarily due to the valve’s piezoelectric actuator. Designed specifically for heavy duty and heavy cycle applications, the piezoelectric actuator maintains a consistently high performance and gives the valve an estimated lifetime of over 1,000,000,000 cycles. Additionally, piezoelectric jet valves are robustly constructed and have fewer moving parts when compared to contact valves. This results in considerably less downtime for system upkeep, replacements, and cleaning.
The benefits of modular jet valves
Although there are many advantages to opting for a non-contact jet valve, manufacturers often need the flexibility to dispense a range of materials for different applications and therefore would like the option to use contact-based methods too.
Systems that incorporate modular jet valves are the perfect solution for this as they can be configured for both contact and non-contact jet dispensing. They offer all the previously outlined advantages of non-contact, high-speed piezoelectric jetting, as well as a broad range of additional benefits. By opting for a modular jet valve, users can dispense a much wider variety of fluids and fluid viscosities. This includes materials such as underfill epoxies, encapsulants and conformal coatings. Modular jet valves can further improve turnover times as the same production line can be used for a multitude of different applications. They can be easily optimised and reconfigured to suit the new requirements without having to be removed from the production line, allowing the application to resume promptly and efficiently. When configured as a contact dispense valve, operators will be able to achieve consistent dispensing of beads or lines at a higher rate than conventional time or pressure systems due to the pumping action.
Furthermore, modular dispense valves offer easy replaceability of all individual wetted parts which are subject to regular wear through usage. These features help keep set-up costs, maintenance and total cost of the operation to a minimum.
For users looking to achieve super accurate dispensing as well as higher throughput and profitability, then high-speed piezo jet valve dispensing could be an extremely worthwhile investment.
Robert Campbell is with Fisnar