Posi-Shut Md Plastics’ latest non-return valve (NRV) technology addresses some of the issues caused by traditional NRVs, which can fail to close consistently, producing variation in the volume of melt displaced from the screw-and-barrel chamber into the mold. In contrast, this mechanically operated poppet uses the kinetic energy of embedded springs to force instantaneous shutoff, independent of the motion of the screw. 

What’s new? The valve. Compatible with most resins, it is available in sizes ranging from 50mm to 260mm. Options also are available for particularly abrasive and corrosive applications. 

Benefits Precise shutoff, ensuring minimal deviations in part weight. This contrasts with traditional NRVs, which leave molders guessing at the effects of melt displacement. To compensate for melt displacement, most molders using traditional NRVs overpack the mold. However, they can’t be sure how much material has actually entered the mold, meaning manual inspection still is needed for 100 percent of critical parts. The NRV ensures better precision, minimizing the risk of part weight deviations and thus saving material. Using the NRV also saves energy and eliminates the need for melt decompression. In addition to providing consistent shutoff, the Posi-Shut NRV is self-cleaning and causes minimal pressure drops. With it, color and material changes are quick. It is easy to install and remove. 

Md Plastics Inc., Columbiana, Ohio, 330-482-5100, www.mdplastics.com