Direct melt gasification to make foamed-metal or foamed-ceramic injection moldings, controls fluid quantity injected as function of melt volumetric flow rate past injection point

摘要

Fluid injection quantity in moles is controlled as a function of melt volumetric flowrate past the fluid injection (6) point (4). This is determined from the alteration in screw (1) position during dosing. The fluid is supplied via a line in which temperature and pressure are measured. From the fluid state equation, the fluid volume injected, is calculated. Temperature and pressure of the plastic melt are measured (5) near the fluid injection point. From this, the quantity of injected fluid required to cause a desired degree of foaming, is calculated. The injected stream in moles of fluid per cm 3of plastic melt, is not uniform over the dosing path. The plasticized melt contains a large volumetric proportion of metal- or ceramic powder. Following injection, binder is removed from the molding and it is sintered. Ahead of fluid injection, the melt is transferred into a melt reservoir, ahead of the screw cylinder. This is filled with non fluid-laden melt, since fluid injection is not effected over the entire dosing path. In the screw antechamber, regions of fluid-laden melt and regions of non-fluid laden melt form. After injection, the non fluid-laden melt lies in the melt reservoir. Ahead of the injection point, the reservoir is filled by one or more melt lines. Residual fluid in the melt reservoir, is withdrawn. An independent claim IS INCLUDED FOR corresponding equipment.