Tools & Technologies

By Blake N. Johnson

Advanced fluid dispensing drives 3-D printing innovations

3-D printing is an actively growing additive manufacturing paradigm driven by the ability to minimize waste, personalize products and fabricate parts defined by complex three-dimensional geometry. 

Thus, researchers are examining various additive manufacturing processes. However, extrusion-based 3-D printing is an especially attractive option due to its compatibility with an expansive set of input materials, high fabrication speed, reasonable printing resolution and ability to integrate multiple materials. Extrusion- based 3-D printing is particularly promising in the healthcare sector for regenerative medicine applications, the pharmaceutical industry for drug discovery applications, and the industrial engineering community for ergonomics applications.

For years, the dispensing industry has supported various sectors, such as the electronics, packaging and automotive industries, in the area of adhesive and sealant dispensing. The development of precision-dispensing solutions for extrusion-based 3-D printing applications has become a critical focus area. However, the task is challenging because the input materials vary widely with respect to viscosity and curing characteristics. In addition, the dispensing path and time interval differ among applications and the resolution for extrusion-based 3-D printing is directly related to the precision and resolution of material extrusion.

Three primary components provide the basis for all extrusion-based 3-D printing processes: motion control, imaging and dispensing systems. Highly advanced motion control and imaging systems already support CNC milling processes, so innovations in dispensing systems currently are driving the evolution of extrusion-based 3-D printing processes.

Such dispensing innovations are occurring in several areas, including dynamic, small volume, rapid and noncontact dispensing.

One innovative solution to print materials that change viscosity throughout the manufacturing process is the Ultimus V High Precision Dispenser from Nordson EFD. The Ultimus V dynamically adjusts the dispensing pressure to maintain a constant dispense rate. For flexibility, dynamic adjustment of the dispensing pressure can be conducted based on either the dispense time or the number of dispense events. The shot size stays consistent regardless of changes in fluid viscosity, and the product has an external personal computer interface for data input. Simultaneous display of all dispensing parameters simplifies process control.

Additionally, Nordson EFD's PICO Pμlse jet valve can accommodate the printing of low-viscosity fluids. To address this challenge, a creative noncontact printing approach is being used based on material deposition via continuous jetting of microdroplets as small as 500 pL (one picoliter is equal to 1×10-12 liters) at frequencies up to 1 kilohertz. Fine-tuning of the dispense pulse time can also be adjusted in increments of 10 μs. Variable stroke makes it possible to set exact, repeatable deposit quantities, and the machine can adjust to handle highviscosity fluids.

Although the future of extrusionbased 3-D printing is still unpredictable, it is clear that advances will be linked closely to innovations such as these in advanced fluid dispensing.

Blake N. Johnson is an assistant professor in the Department of Industrial and Systems Engineering at Virginia Tech and a member of IISE's Young Professionals group.