Servo vs Pneumatic Fluid Dispensing Comparison

Applying material to a surface requires precision, efficiency, and a focus on achieving the highest quality results. At GP Reeves, we have built a wealth of expertise in precision dispensing since our founding in 1971, growing over the years to provide global industry leaders with a range of effective dispensing solutions. Our typical fluid dispensing systems leverage positive displacement pneumatic or servo dispensers. Join us as we take a deep dive into these technologies, where we’ll explore the differences between servo and pneumatic dispensing and how each contributes to the success of your production line!

Positive Displacement Dispensing

At GP Reeves, consistency and reliability are top priorities, which is why we focus on the development of cutting-edge positive displacement dispense systems. These systems only need to be set once, eliminating the need for continuous adjustments required by timed-pressure dispensing. Furthermore, positive displacement dispensers are not affected by external environmental conditions, making them ideal for materials that may change viscosity due to temperature or humidity variations.

One common type of positive displacement dispenser is the rod system. These systems operate by transferring material under pressure into and out of a measuring chamber using pneumatic or servo-powered dispense rods. This design ensures a consistent and repeatable material dispense. The dispense rods are paired with a piston (in pneumatic systems) or a linear actuator (in servo systems), which controls the transfer volume. The dispense rate is directly proportional to the diameter of the dispense rod and its speed. This relationship is represented by the following model, where Q represents the flow rate, Vp is the piston motion velocity, and Dp is the piston diameter.

Methods of Positive Displacement Dispensing

With rod-style positive displacement dispensing, there are two common methods: pneumatic and servo-powered. Understanding the distinction between these methods is key to selecting the best option for your material delivery needs. Pneumatic rod-style positive displacement systems inherently use linear motion to dispense material, while servo-powered systems convert rotational motion into linear motion for dispensing. Despite these differences, both methods offer high levels of accuracy, reliability, and efficiency, ensuring effective material application for a variety of production environments.

Basics of Pneumatic Dispense Systems

Pneumatic rod-style dispensers utilize a linear position sensor with PID controls, along with compressed air, to drive the dispense rod. The air pressure moves the rod, which in turn displaces the material. Linear position sensors track the rod’s location, providing real-time data on the distance traveled between two points of motion. Operators can program a specific dispense volume, which directly correlates to the rod’s movement distance. The PID controls continuously monitor the piston rod’s position within the dispense chamber and adjust the air pressure accordingly, ensuring a steady dispense rate. While this system offers a high level of accuracy, the reliance on air pressure means the dispensing rate may not be as consistent as in servo-powered systems.

Basics of Servo-Powered Dispense Systems

Servo-powered positive displacement rod-style dispensers operate by electromechanically converting the rotary motion of a motor into linear motion. This conversion is achieved through a ball screw within the linear actuator, which adjusts the dispensing speed and impacts the overall torque of the system. The motor directly controls the speed and force of the actuator, enabling precise movement.

In this type of dispensing system, the servo motor drives the dispense rod, which moves material out of the measuring chamber. The system ensures repeatable, consistent dosage volumes with each dispense. Operators can program the desired flow rate and dispense volume, and the servo motor will execute these parameters through its controlled rotary motion. Unlike pneumatic systems, servo-driven dispensers maintain their programmed rate and volume regardless of external environmental conditions, ensuring consistent performance even in fluctuating atmospheres.

Choosing Pneumatic vs Servo

Now that you’re familiar with the basic principles of pneumatic and servo-powered positive displacement dispensing systems, you can make a more informed decision about which system best suits your production needs. To simplify this process further, we’ve outlined the key considerations of each system, helping you easily compare the benefits they offer to your assembly process.

Servo

• Automatically adjusts rotary force to compensate for changes in temperature, air pressure, or material viscosity
• Electromechanically calculates the distance required for the piston rod to move
• Ideal for applications where verifiable dispense volumes are critical
• Offers greater control without the need to modify the air cylinder size
• Capable of maintaining tighter tolerances
• Easier to operate, integrate, and fine-tune

Final Thoughts

While the decision between a servo or pneumatic dispensing system often depends on the specifics of your application, it may ultimately come down to operational preferences and your preferred programming method. Both pneumatic and servo-powered positive displacement dispensers deliver exceptional accuracy and efficiency. With proper maintenance and adherence to safety guidelines, both systems can significantly enhance your production process. To explore which option is right for you, contact our team of dispensing experts today to discuss your servo or pneumatic positive displacement system needs!