A newly patented actuator-and-pin apparatus can help processors that perform cascade molding better control the flow rate of melt into the mold, according to Synventive Molding Solutions Inc., Peabody, Mass.
The technology, which is used in the company's SynFlow system, provides control over the opening speed of the valve pin and release of pressurized melt into the mold.
Sensors provide feedback about the pin's position. Typically, chief engineer Bill Rousseau said, the pin opens at a slow controlled speed for a short distance to control the surge of pressurized plastic into the mold; once the pin covers a set distance, it returns to maximum velocity to allow for unrestricted filling of the remainder of the cavity.
The system prevents melt from gushing into the mold, which can result in inconsistencies in part quality.
"By controlling pin opening, we can control those sudden surges and stagnations," Rousseau said.In one example cited by the company, changes in pin opening had an immediate impact on part quality. In that case, a major car manufacturer experienced surface blemishes on car interiors, which exhibited varying levels of gloss due to pressure alteration and opposite gating marks. In molding the interiors, the nozzles were under full injection pressure, and the melt entered the mold with an explosive burst, leading to a sudden increase in flow-front velocity.
Once the molder began using SynFlow, quality of the car parts improved dramatically.
"A smooth flow velocity in the cavity was achieved by a differentiated valve-pin opening control," Synventive said.
SynFlow is available for hydraulic valve-gated hot-runner systems.
Patent 9,636,858; issued May 2
In other patent news:
Preforms. Packaging manufacturer Amcor Ltd., Hawthorne, Australia, received a patent for a molding apparatus and method for applying pressure to blow molded PET preforms to control shrinkage.
The apparatus includes a primary mold, a secondary mold, a blow pin to introduce gas, and a reheating device, such as an oven that is separate from the primary and secondary molds. The reheating device is used to heat the shrunken preform before it is introduced into the secondary mold. The reheating device also can be used to heat the primary mold. Amcor's U.S. headquarters, Amcor Rigid Plastics, is in Ann Arbor, Mich.
Patent 9,636,878; issued May 2
Melt filtering. Maag Automatik Inc., Charlotte, N.C., has commercialized a device for filtering plastic melt that is applicable for pipe, sheet and profile extrusion, for pelletizing downstream of an extruder, or for plastics recycling operations involving extrusion. It includes a housing and a filter pin with a drainage channel, and combines two functions previously handled by separate devices: filtering the plastic melt and diverting the melt stream if the quality is off-spec.
During the startup of the extruder, filter changes or brief interruptions to the extrusion process, the device moves into the bypass position, draining the plastic melt until the quality is stabilized. This keeps the processing conditions constant and eliminates the need to stop and restart the extruder.
The device uses a curved screen to increase the available filter surface area without increasing its overall footprint. Maag Automatik GmbH, Grossostheim, Germany, filed the patent application.
Patent Application 20170128861; published May 11
Injection mold pod. Tessy Plastics Corp., a West Elbridge, N.Y., injection molder and contract manufacturer, has applied for a patent for modular pods that can be linked together to form a multicavity injection mold. The pods include inserts (cavities) that are shaped to produce molded parts.
If one part of the mold experiences a problem, the relevant insert can be removed and replaced quickly, eliminating the need for lengthy and costly repairs, according to the patent application.
Patent Application 20170144349; published May 25
Patents and patent applications can be viewed at www.uspto.gov
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