Improving production yield in micro-volume dispensing hinges on four key elements.
A more detailed explanation of these elements is detailed below.
Temperature plays a crucial role in fluid dispensing processes for several reasons:
The viscosity of fluids typically changes with temperature. For many fluids, viscosity decreases as temperature increases, making them flow more easily. Conversely, lower temperatures increase viscosity, making fluids thicker and more resistant to flow. Controlling temperature ensures that the fluid maintains the desired viscosity for accurate dispensing.
Temperature affects the rate at which fluids flow through dispensing systems. Consistent temperature control helps maintain a stable flow rate, which is crucial for precise dispensing in manufacturing processes.
Some fluids can undergo chemical changes or phase transitions at specific temperatures. For example, certain adhesives or sealants may cure or harden more quickly or slowly depending on temperature. Proper temperature control ensures that these materials behave predictably during dispensing and do not prematurely cure in holding containers.
Dispensing equipment, such as pumps, valves, and nozzles, can be sensitive to temperature variations. Extreme temperatures can affect the performance and longevity of these components. Maintaining optimal operating temperatures helps to ensure reliable and efficient dispensing operations.
Temperature variations in the environment where the dispensing occurs can also impact fluid properties. Changes in ambient temperature can affect the temperature of the fluid itself or the dispensing equipment, influencing the dispensing process.
In essence, temperature control is critical in fluid dispensing to ensure consistent fluid properties, accurate dispensing rates, reliable equipment performance, and overall quality of the dispensed product or material.
Cavitation refers to the formation and subsequent collapse of vapor-filled bubbles within a
fluid, typically when the pressure in the fluid falls below its vapor pressure. This
phenomenon can occur in pumps, propellers, turbines, and other fluid systems. Cavitation is a
significant issue in fluid dynamics because it can have various impacts on both the fluid and
the equipment involved.
Process of Cavitation
The process can be represented as below:
When the local pressure in a fluid drops below its vapour pressure, small vapor bubbles form.
Subsequent decrease in fluid pressure contributes to the bubble growing larger.
As the pressure in the fluid rises again the vapour bubbles collapse rapidly, often creating shock waves.
Impact of Cavitation on Fluids and Equipment
The collapse of the bubbles generates high-intensity microjets and shockwaves, which can erode metal and polymer surfaces and damage equipment. This is commonly seen in pumps, valves, and syringes, leading to premature wear and reduced efficiency. The wear material can also be carried by the dispensing fluid potentially leading to foreign bodies in the finished product which contribute to defects.
Cavitation reduces the efficiency of fluid systems. For example, in pumps syringes and tubing, cavitation causes bubble formation. This in turn contributes to inconsistent dispensed volumes due to dispensing of entrained air. These air pockets can cause underfilling or sputtering of materials on guide rails, heat sealers impacting packaging quality.
The implosion of cavitation bubbles generates localized heat, which can increase the temperature of the surrounding fluid and equipment surfaces. This heat can cause thermal stress, and in some cases accelerate material degradation contributing to effects such as pitting in contact lens manufacturing. In certain cases, the implosion of cavitation bubbles can generate high temperatures and pressures that lead to chemical reactions, potentially altering the fluid’s properties or causing unwanted side effects.
Preventing Cavitation
To avoid the negative effects of cavitation, we design and build our systems to Increase the Fluid Pressure, trying to ensure the pressure in the system remains above the vapour pressure of the fluid, thus reducing the conditions required for cavitation. We Optimise and Control Flow Speed as reducing the flow velocity can help prevent pressure drops that cause cavitation. Through Proper Equipment Design we Optimise the entire fluid path within optimal conditions to reduces the likelihood of cavitation.
In summary, while cavitation is a natural phenomenon in fluid dynamics, its impact on fluids and equipment can be detrimental, leading to wear, noise, loss of efficiency, and potential damage. Proper design and operational strategies are essential to mitigate these effects.
Viscosity and rheology play crucial roles in the dispensing of microvolumes. Here’s how they affect the process:
Viscosity, or resistance to flow, has an impact on Flow Characteristics. Higher viscosity fluids flow more slowly and may require more pressure to dispense effectively. This can affect the speed and accuracy of dispensing microvolumes as time is required to dispense and once the product is flowing how do you ensure it does not overdose. Lower viscosity fluids tend to dispense more accurately for microvolumes because they are less prone to variations in flow rate.
Rheology is the study of how materials flow and deform under force.
A Newtonian fluid is a fluid whose viscosity remains constant, no matter how much force (shear rate) is applied to it. In other words, it flows consistently and predictably regardless of how fast or slow it is stirred, pumped, or moved. It also starts flowing as soon as any stress is applied—there’s no threshold force needed.
Most fluids are Non-Newtonian Fluids with some exhibiting complex rheology (like shear-thinning or shear-thickening behaviour) and changing viscosity under different conditions. This variability can complicate the precise dispensing of microvolumes.
The design, optimisation and tuning of dispensing equipment need to account for the viscosity and rheology of the fluid being dispensed.
Viscosity and rheology affect how fluid moves through the dispensing system, influencing factors such as droplet size, consistency of dispensing volume, and overall precision. Different fluids may require different types of reservoirs and tempering systems, dispensers and adjustments in dispensing parameters, transfer tubing dimensions, dispense needle specifications etc to effectively and consistently dose the required volume.
In summary, understanding the viscosity and rheology of fluids is crucial for effectively dispensing microvolumes. It impacts the choice of equipment, the frequency of calibration of dispensing systems, and ultimately the accuracy and reliability of the dispensing process.
The accuracy of dispensed volume in manufacturing, can be influenced by several factors and here are some key considerations:
Proper calibration of dispensing equipment is crucial. If pipettes, dispensers, or pumps are not calibrated regularly or correctly, they may not dispense the intended volume accurately. Also, as systems wear calibration and adjustment will allow tuning to deliver required performance.
The precision of the equipment used affects its accuracy. High-quality instruments designed for precise measurements tend to offer better accuracy in dispensing volumes. Syringe pumps will always outperform peristaltic pump for microvolume dispensing. The dispensing system including ancillary components need to offer performance suitable for the dispense requirements.
The technique used by the operator plays a significant role. Factors such as speed of dispensing, angle of dispensing, and consistent handling of equipment can impact the accuracy of volume dispensed. A standard operating procedure is require to ensure system setup is as per defined operating protocols to ensure accuracy and precision.
Temperature and atmospheric pressure can affect the volume of liquids. Changes in these conditions may alter the density of the liquid, thus impacting the accuracy of volume dispensed. Understanding and control of environmental parameters is required for consistency.
Liquids with higher viscosity may adhere differently to dispensing equipment or require different techniques for accurate dispensing compared to low-viscosity liquids. The system needs to be tuned according to Viscosity and Rheology of the dispensed fluid.
The accuracy of the measurement scale or readout used to verify dispensed volume is crucial. Even a small error in measurement can compound over multiple dispenses. Ensure any equipment used to verify dispense if regularly calibrated and verified.
The quality and cleanliness of consumables such as tips, tubes, or syringes used for dispensing can affect accuracy. Contamination or improper fit can lead to inconsistent volumes. Only use high quality consumables.
Certain systematic errors can arise from inherent design flaws in equipment or from consistent errors in technique that need to be identified and corrected through validation and training. We design and beta test system to ensure they perform to specification and user requirements in production environments. We can also assist with validation and tuning on the lien to optimise productivity, accuracy and precision.
Proper handling and maintenance of dispensing equipment are essential. Regular cleaning, proper storage, and adherence to manufacturer’s guidelines can prevent issues that affect accuracy. We offer a support and repair service for supplies systems.
Regular validation and verification of dispensed volumes against a standard reference is necessary to ensure ongoing accuracy. This helps identify any drift or errors that may occur over time.
Addressing these factors through proper design, build, integration, training, maintenance, and validation processes can significantly improve the accuracy of dispensed volumes in microvolume applications.
Get in touch with us below to get started. Feel free to call us on +353 (0)46 900 9050 or email
info@industrial-fluidics.com
Get in touch with us below to get started. Feel free to call us on
+353 (0)46 900 9050 or email
info@industrial-fluidics.com
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