Non-Return Valve

Proven Design Offers Precise Shutoff, High Flow, And The Lowest Pressure Drop!

The objective of Md Plastics Posi~Shut™ Valve is to empower the processor with advanced control of the valve shut off mechanism during molding. This is accomplished by eliminating a need for decompression and facilitating valve shut off at melt recovery independent of the screw’s movement forward. In a perfect molding scenario, the non-return valve closes quickly, completely at the same time for each shot. Without restriction and sacrifice of flow and self cleaning characteristics. This action ensures a repeatable process consistent from shot to shot. The benefit is lower reject rate, higher part quality, maximum yield rate and increased profit margin.

The Posi~Shut™ Valve is a mechanically operated poppet valve that is independent of screw movement to facilitate closure. The valve’s standard construction is of wear resistant heat treated H13 tool steel and there are metallurgical and surface treatment options for extreme abrasion and corrosion wear environments.

The Posi-Shut™ valve utilizes the patented Md Plastics Mini~Shut™ technology with a replaceable shutoff cartridge patent number #8734146. The valve closure is expedited by the kinetic energy created by the Belleville springs to achieve instantaneous and precise closure at the sealing surface with each shot. Upon screw recovery, valve closure and shot delivery the valve then opens upon screw rotation and positive melt flow preparing for the next shot to be delivered. Each shot is delivered with precise “Shut-off” for each cycle.

The Posi~Shut™ valve is compatible with most resins processed in the injection molding industry. A distinctive version is available for the processing of Liquid Silicone Rubber “LSR.” The Posi~Shut™
Valve is an excellent valve selection for structural foam molding. Consult Md Plastics technical staff for design considerations in molding applications involving difficult to process resins.

Thermoplastics Size Range: 50MM and up – Liquid Silicone Rubber “LSR” – customized design and size range.


  • Mechanical Shut Off Independent of Screw Position
  • Replaceable patented Shutoff Cartridge
  • Valve Body Designed to Minimize Heat
  • Low Pressure Drop and Low Shear
  • Advanced Hydraulic Flow
  • Operable at Temperatures exceeding 750° F
  • Designed for Most Machines and Resins
  • Cleans Easily with Normal Purging Methods
  • Durable H13 Tool Steel Construction
  • Metallurgical Options for Abrasion and Corrosion Applications
  • Size Range 50MM Diameter and up


  • Shot to Shot Consistency
  • Consistent Part to Part Weight
  • Lower Scrap Rate
  • Opens with Melt Flow
  • Instant Shut-Off
  • Independent of Screw Movement
  • Eliminates a need for Decompression
  • High Throughput and Self-Cleaning
  • Multi-Purpose Use
  • Ease of Installation and Removal
  • Long Wear Life
  • Competitive Price