Electrical valve gate system with servomotor for Class A surfaces

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  • Individual & precise opening/closing of valve pins with pre-selected speeds
  • Result: optimised filling of cavity at low pressure
  • HRSflow at #Fakuma

The Italian hot runner manufacturer HRSflow presents its new FLEXflow electrical valve gate system with servomotor for Class A surfaces at this year’s #Fakuma. The system is particularly suitable for large but thin-walled components such as dashboard carriers and spoilers.

The electrically-driven actuation cylinders, which were specially developed for cascade injection moulding, allow an individual and precise opening and closing of the valve pins with pre-selected speeds. This enables a precise control of melt flow and volume flow into the cavity. The result is an optimised filling process. Due to the gradual pin opening and closing, possible pressure drop marks are avoided. Such marks, visible for example on bumpers as a mat line, are not necessarily immediately visible. In many cases these visual defects appear only after subsequent painting.

FLEXflow system

Overview about a complete FLEXflow system

Individual control of up to 16 hot runner nozzles

A separate control unit operates the FLEXflow system. Currently up to 16 hot runner nozzles can be individually controlled. A maximum of eight valve pin positions are possible for each of the nozzles with a precision of up to 0.01mm. Each position can be set with individual opening speeds and, furthermore, the valve pins can still be manually adjusted. All configuration data once entered can be saved together with the data records belonging to a specific tool, and can be retrieved after changing the tools.

Tendency to warp is significantly reduced

Besides avoiding pressure drop marks and thus ensuring improved optical properties of the part, the FLEXflow system offers other technical processing advantages such as lower holding pressure compared to conventional cascade injection moulding technology. Tendency to warp is significantly reduced. And the lower pressure requirements affects the tool-specific closing force: tests with a near-production spoiler tool have demonstrated that the closing force can be up to 20% lower. This makes it feasible to clamp an appropriately equipped tool on a smaller machine.

“Overloading” of tool not required

Due to the reduced holding pressure profile, “overloading” the tool, which is seen in many cases as a conventional procedure, is not required. Apart from the fact that excessive holding pressure would involve the risk of burr formation, the high pressure also puts unnecessary stress on the tooling. On the contrary, the low holding pressure of the FLEXflow system results in reduced wear and contributes to material savings. Tests have shown savings of up to 5%.

Another feature of the FLEXflow can be described as “Dry-clean-save”. Due to the electromagnetic operation of the valve pins, there is no need for hydraulic or pneumatic cylinders including the associated pipelines. Cooling systems, as used for conventional hot runner actuation cylinders, are also not required. The heat-resistant servo drives do not require any cooling and can be even integrated into the clamping plate. Due to its design, the oil and water-free FLEXflow system is suitable for use in a clean room environment.

comparsion pressures

Comparison of pressure profiles for standard cascade molding and cascade opening with electrical cylinder.

Case study: rear spoiler

In order to demonstrate the system’s capabilities in practice, the company has built a series of production-ready test tools for the manufacturing of a rear spoiler (1,260x280x120mm; Material PP-EPDM 20% Talk). The tool was equipped with a 7-way hot runner system. Pressure sensors were integrated behind the individual injection points in order to record pressure flow.

Both conventional cascade injection moulding and the FLEXflow system have been operated with the tool. Comparison tests have shown an equal pressure flow throughout the entire cycle and a reduced pressure profile with the FLEXflow system, whereas the difference between the maximum and minimum inner tool pressure was only 50 bar instead of 100 bar.

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