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Dynisco unveils accurate, direct pressure sensor

By: Bill Bregar

January 18, 2013

FRANKLIN, MASS. -- Dynisco LLC is taking the direct approach with the new Vertex sensor, which measures melt pressure in extrusion directly, with no mercury or other liquid-fill materials, or complicated mechanical push rods.

After 10 years of development, the result is a robust pressure sensor that measures pressure more accurately, with a faster response, than traditional sensors, according to Dynisco officials.

"If you get rid of the fill materials, you have a more direct measurement. It's more accurate and more reliable," said Matthew Carrara, vice president and general manager.

Patents are pending on the capacitance technology. Melt pressure is registered directly through a single diaphragm, which is six times thicker than those on other sensors. It is made of Inconel 718 allow and coated with Dynisco's diamond-hardened DyMax, for extra protection against abrasion and corrosion.

Dynisco of Franklin is offering a longer, four-year warranty for the unit.

With Vertex,Carrarasaid, Dynisco has approached the "holy grail" of melt sensors, sensitive instruments that have to be sturdy to withstand high temperatures, pressures and other stresses in extrusion.

"I would argue that it would be the most perfect sensor on the market," Cararra said. "It addresses all the concerns of people in the market."

Mike Davis, senior product manager said representatives from every department at Dynisco participated in developing Vertex. Taking a consultative approach, they asked customers what they wanted in a sensor. A five-person team, from engineering, sales, operations engineering and marketing, worked on functionality of the sensor, and also manufacturing, marketing, sales and service.

"The entire way that this was developed internally was totally different,"Davissaid.

As a result, the new design cuts lead times from up to 14 weeks to fewer than 14 days. Vertex is designed to be a drop-in replacement for existing sensors. The new sensor can handle temperatures as high as 660°F.

Located along the barrel, melt pump and screen changer, the melt pressure sensors play a key role in consistency, throughout, quality and safety. The tip is exposed to the molten plastic, and traditionally, mercury has been placed between the sensing diaphragm and the sensitive electronics, to protect them from the heat. To replace mercury, sensor manufacturers have used other fill materials, such as sodium-potassium, oil and gallium. But mercury is still commonly used, Dynisco officials said, adding that Vertex shows that a fill medium, which results in an indirect measurement, is not needed.