Precise Dosing from 10 mg per Shot
Cylinder Dosing Unit for Micro Injection Molding and Extrusion
Tschritter GmbH, Dorfprozelten, Germany, has developed two different cylinder dosing units for use on injection molding and extrusion machines. The Cyclical Dosing System (WD 1) doses two or more additives directly into the (virgin) material flow on the machine. The Simultaneous Dosing System (WD 2) doses two or more different additives or pellet compounds simultaneously and in parallel directly onto the machine conveying screw. It is claimed that low dosing rates from 10 mg/shot, but also high rates up to 3 g/s (independent of the machine cycle time), are possible, which also makes the system interesting for extrusion applications, according to the manufacturer.
Through the infinitely variable adjustment of the rotation speed and cylinder design, it is claimed that each individual material type can be dispensed in controlled amounts. The flow rate is controlled by three different cylinders, which are available in plastic or stainless steel. The link to other machines of the manufacturer (e. g. feed units) but also to customers’ machines is provided by a control unit (WDx), which, besides formulation control, also features logbook recording and user management, which, in the company’s view, is a positive feature for quality management.
The system is currently patent pending and, according to the manufacturer, promises great potential in dosing technology, where ever faster material exchange and greater precision will be important in future.
Where other cylinder systems reach their limits, the WD system uses a technology that first loosens the pellet stream, repacks it and then meters it in microsteps directly into feed of the injection molding machine or extruder. This results in a uniform pigment or additive dosing rate. According to the manufacturer, the reject rate can be reduced to 0 %, minimizing the material costs. The system is also said to be easy to clean with no wear parts such as scraper bars. Thanks to the rapid response of the system, prompt color and material exchange are claimed to be possible.
Translated from Kunststoffe 10/2015, p. 12.
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