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www.us-tech.com


August, 2017


Progressive Cavity Pumps Enable Vital Precision and Repeatability


By Can La, Product Manager, Techcon Systems


consistent application of adhesives, epoxies and other fluids. This was especially difficult for small depositions, when working with viscous materials and when aiming for the fastest possible through- put speeds. Jetting valves — perhaps the gold standard


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for high-speed, micro-deposit applications —can be unsatisfactorily turbulent in their accuracy. Time/pressure dispensers and auger valves can deliver accuracies down to ±10 and ±5 percent, respectively. But, they have a variance that might be unacceptable for many operators, with deposit size affected by temperature-driven changes in material viscosity, as well as fluctuations in air pressure created by the changing fluid level in the syringe barrel. The original volumetric or positive displace-


ment pumps, such as piston or gear pumps, while able to get closer to the “holy grail” accuracy level of ±1 percent, are often limited in bead size and can be slow, due to their need to refill between dep- ositions. For many organizations, these limitations,


along with the mandatory balancing act among variables, require prohibitive compromises. However, for an increasing number of companies in numerous, highly-competitive industries, the search for a superior adhesive and epoxy dispens- ing option has continued.


Progressive Cavity Pumps Drawing on technology from heavy industry,


such as oil drilling and cement processing, innova- tive dispensing equipment manufacturers have become aware of progressive cavity pump technol-


p until roughly five years ago, operators of manual and automated dispensing lines had little ability to achieve highly-accurate,


ogy. Progressive cavity is a type of positive dis- placement pump technology long-proven in critical


footprint, progressive cavity pumps offer a number of advantages over conventional methods of dis- pensing.


Unlike other types of epoxy and adhesive dis-


pensing solutions, including other types of positive displacement/volumetric pumps and time/pressure valves, a progressive cavity pump is both a sealed system and a continuous-flow operation. Progressive cavity pumps can dispense micro-


beads as small as a microliter, using a wide range of materials with viscosities ranging from 1 to 300,000 cP or more. And, since internal material flow is continuous, rather than relying upon a fill- ing/refilling approach, throughput speeds are con- sistently high. Most dramatically, however, progressive cav-


ity pumps can deliver volumetric dispensing accu- racy up to ±1 percent, and do so reliably. They are unhindered by the ambient temperatures and pressures that plague unsealed pumps exposed to environmental conditions, or variations due to changing material volume levels during operation.


How it Works The essence of a progressive cavity pump is


TS8100 positive displacement progressive cavity pump.


applications that include moving heavy oils and slurries from deep underground. With the technology now successfully minia- turized and adapted to a tabletop or assembly line


that it operates by use of a continuous rotor/stator configuration, rather than ejecting material from filling chambers at fixed, separated intervals. In progressive cavity technology, the feed fluid — from water up to high-viscosity greases or solders — is held in a reservoir under positive pressure supplied by an air line. The pressure forces the fluid out of the barrel into the fluid feed path and then to the rotor/stator chamber assembly. The metal, single-helix rotor continuously


turns inside a flexible rubber stator molded with a twin-helix-shaped aperture, forming a constantly


Continued on page 52


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