One problem with manufacturing minute shot weights of less than one gramme is, in some cases, the very long material dwell time in the infection unit, the company says. The displacement distance of the screw can be extremely short because of the small injection volume. This is solved by operating the two screws which "share" the preparation, dosing and injection of the material. A servo-electrically driven screw pre-plasticising section, which is installed at 45 degrees to the horizontal injection unit, ensures standard granulates are prepared under suitable conditions. The molten material is then transported from the pre-plasticising stage to the injection unit.
The injection screw is used purely for transport purposes. It has a diameter of only 8 mm, is fitted with a non-return valve and operates according to the screw/piston principle. This permits the smallest shot weights to be achieved with great precision and the required travel distance. The melt is continuously fed from the material inlet to the tip of the injection screw.
Arburg’s micro-injection module is designed specifically for use on electric Allrounder A machines with a size 70 injection unit. Its enclosed construction means that it can be changed rapidly and then used on various machines, like any other Arburg cylinder module.
