MD Plastics Inc. of Columbiana, Ohio, has introduced the MDP sliding-ring, nonreturn valve that the company said provides very low pressure drop and consistency of part weigh from shot to shot.
The nonreturn valve incorporates a shaft and retaining bushing assembly engineered to transform the sliding frictional force that normally occurs in a screw tip into a radial force.
MD Plastics President Mike Durina said he was surprised with the initial test results, which looked too good to be true.
In fact, more recent test results have shown that our MDP screw tip was 10 times more accurate than what was determined in tests performed both by a major independent research lab, and in previous studies at a major supplier of front-end components, Durina said.
The shaft and bushing assembly restricts the ring's forward motion, to determine stroke during plasticizing. The ring is forced against the assembly through viscous drag.
Then, the hydraulic pressure of the plastic transforms the sliding force that normally occurs between these two surfaces into a radial force between the shaft and bushing.
Durina said a radial motion is less abrading that a sliding force, so there is less wear. That geometry contributes to much lower pressure drop across the ring giving better shutoff accuracy and shot-to-shot consistency.
Tel. 330-482-5100, fax 330-482-5211, e-mail [email protected]