Analysis of working principle of two-speed sequential injection molding

In order to avoid injection defects, the injection high pressure built up in the hot runner system must be strictly controlled before the nozzle of the subsequent relay is opened. Otherwise, the plastic under high pressure will explode when each valve needle is opened, resulting in an explosion. The front end flow rate is significantly increased, causing an abnormal surface of the product on the surface of the cavity, and at the same time, the surface of the product is defective due to uneven internal structure.

To solve these problems, Synventive developed the SynFlow two-speed sequential injection hot runner technology, which allows the user to control the melt pressure in the cavity while opening the nozzle using the two-speed valve needle process.

Two-speed sequential injection molding works

SynFlow is a two-speed needle valve control technology that has been patented for sequential control of hot runner systems. This technology reduces the plastic flow rate when the needle valve is just opened, prevents the plastic from exploding after being pressurized, and then the valve needle opens at maximum speed to ensure proper filling. The two-speed process can make the whole filling process more stable, reduce the pause or rapid change of the plastic during the flow process, ensure the appearance of the product is bright and tidy, and greatly improve the injection efficiency.

Each SynFlow system is equipped with a hydraulic needle valve hot runner system and offers three nozzle diameters of 12 mm, 16 mm and 22 mm and a cylinder with sensors. SynFlow? The flow control device includes a control needle valve, a signal line that connects the control needle and position sensor, an 8-zone controller, and a hydraulic valve block (up to 8 units/64 partitions per SynFlow control system available).

SynFlow two-speed technology effectively eliminates surface defects in large injection molded parts. Problems that can be solved include: stress marks, sun spots on the opposite side of the gate, shrink marks after spraying, and reduction of product adhesion.

Through this technology, molders can reduce the scrap rate and improve the injection molding process to reduce production costs while producing cleaner and more beautiful parts.

From theory to practice

SynFlow technology has many successful cases in Europe. For example, Toyota Textile Europe's car seat back uses SynFlow technology. Toyota Textile Europe is a first-line supplier of automotive components for BMW, Daimler, Volkswagen, Audi and Opel. The company develops and manufactures automotive interior system components, including seat components, door panels, pillars, and ceiling panels.

Audi's new seat back project does not handle weld marks well using conventional sequential injection molding. Before filling, the late-opening hot nozzle is subjected to the full injection pressure. When the next needle valve is opened, there is a melt flow similar to the explosion in the cavity, resulting in a significant increase in the flow velocity at the front end of the filling, and uneven gloss on the surface of the dermatoglyph. The defect creates a pressure line and forms a sun spot on the opposite side of the gate.

After using SynFlow technology, the smooth flow rate in the cavity is realized by controlling the position of the valve needle to open, and the plastic melt flow control is realized in the sequential injection molding, which effectively avoids these problems.

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