Transfer & Injection Moulding Presses - Articles & Resources

Injection Molding Compounders Molders Get Control Of Their Materials The combination of an injection molding press and a twin-screw compounding extruder represents a new paradigm for processors: They create their own materials as they mold them. Although the machinery systems are expensive, they provide new opportunities for materials cost savings and flexibility to tailor formulations for individual parts. However, the molder must now take responsibility for the raw materials as well as the molded parts. And adding complexity to the process also multiplies the number of variables to control.

Nonetheless, these multi-million-dollar machines have established a growing niche. Almost four dozen have been sold, and the number of suppliers has grown to three, with a fourth supplying a different but related approach. What started out a decade ago as a way to reduce the costs of molding long-glass thermoplastic composites for structural automotive parts has spread to non-automotive applications and to other sorts of compounding and alloying tasks.

In-line compounding and injection molding got its initial impulse from the upsurge of so-called DLFT or DLFRT technologies in recent years (see Learn More). Direct Long-Fiber (Reinforced) Thermoplastic processes for in-line compounding-and-molding—either compression or injection—were aimed at helping thermoplastic composites compete more cost-effectively with thermoset SMC (also a long-fiber process). DLFT was developed to be lower cost than glass-mat thermoplastics (GMT) and long-fiber pellets produced by thermoplastic pultrusion methods. Both GMT and long-fiber pellets require sophisticated, proprietary processes to produce the intermediate raw material in sheet or pellet form. GMT has the additional disadvantage of producing substantial amounts of scrap that cannot be reused in that process.

The first DLFT processes separated the compounding and molding steps and required a manual or robotic transfer of the hot compound to the press. The latest step in the evolution is to integrate compounding and molding on an injection machine to provide greater automation and shorter cycles than can be achieved with compression molding.

Source: http://www.ptonline.com/