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A new way to handle changing fluid viscosity

A new way to handle changing fluid viscosity
Solving the problem of changing fluid viscosity and the 'full-to-empty' effect in dispensing application, Nordson EFD has developed a new high precision dispenser.

Silver epoxies, die-attach epoxies and underfill materials are used in many electronics and other assembling applications in production. Because these fluids change viscosity over time, they pose a unique challenge. As these materials begin to get thicker over the course of their working life, shot size gets smaller. To compensate for the characteristics of a given material, dispenser or valve controller settings need to be adjusted with usual dispensers to keep the amount of material applied consistent.

To solve these problems, Nordson EFD developed the Ultimus V High Precision Dispenser. Based on EFD's proven precision fluid dispensing technology, the Ultimus V dispenser eliminates viscosity-related issues by automatically adjusting dispensing parameters over the course of the fluid's working life to maintain uniform shot size. Unlike standard dispensers, which employ analogue air regulation, the Ultimus V features an EFD-developed electronic air regulator, so that all dispensing parameters - including time, pressure, and vacuum - are controlled electronically, for exceptional accuracy, repeatability and process control. 

Viscosity profile
When using the Ultimus V dispenser, the first step is to determine the fluid curve and track the changes of the viscosity profile over time. In many cases this information may be available from the fluid manufacturer; in others it will have to be observed and calculated in-house. 

Once the fluid curve has been determined, the Ultimus V's intuitive menu structure is used to set the time, pressure and vacuum parameters needed to accommodate each viscosity interval into the memory cells. This can be done directly from the touchpad on the face of the unit, or the user can employ the RS-232 connector and EFD User Interface software to program the Ultimus V with a personal computer or via PLC or other interface systems that utilises industry standard RS232C protocol. 

The Ultimus V features an 'Auto Increment' function that contains 400 memory cells, each storing individual pressure, dispense time, vacuum and trigger settings.  The trigger value can be set to either the number of dispense cycles that occur for each interval ('count mode') or to the amount of time in seconds that elapses for each interval ('timer mode'). When the specified interval/trigger has expired, the Ultimus V transitions to the next cell and stored settings. The Ultimus V offers a unique feature: it allows this interval/trigger to be different for each incremental step.  This reduces the number of intervals needed for each viscosity curve, so that more curves can be stored in the 400 memory cells of the Ultimus V.  

Once the appropriate settings have been programmed into the memory cells, the job can be saved or uploaded via the interactive software to a PC for the next time that material is used. In addition, the interactive software has a convenient 'offset' feature that provides an easy way to simultaneously adjust all memory settings to compensate for subtle differences between fluid batches or changes in ambient temperature within the production environment. This approach can dramatically increase productivity while saving both time and money. 
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