Adjustable screw geometry

A liquid colorant metering system from Hanna Group offers a simple, clean and less expensive alternative to cleaning machinery and shop floors. It incorporates a three-way valve that temporarily diverts colorant from the moulding equipment to a special calibration section for weighing, keeping this 

Machinery manufacturer Parrel has developed a two-stage compounder that it claims will have the highest dispersive mixing capability of any unit yet developed. It combines a two-stage continuous mixer with a single-screw extruder, and is aimed at a wide variety of new and demanding applications. 

Key features are extra mixing length and residence time, with a greatly expanded processing window. There is a variable operating LD ratio from 5 1 to 10 1, and the counter-rotating mixer has rotor speeds of up to 1000 rpm. As well as using rotor speed, fill factor and temperature as control variables, the machine also introduces the possibility of variation in clearances of the chamber wall 

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Fig. 42 shows this relationship for such a liquid (lubricant for steam engines with ca. 7 % A1 stearate, t, = 9.7 Pa s, = 0.205 s-1). This was established with two differently sized (d = 60 and 90 mm) single-screw machines with the same profile geometry using two rotational speeds (n= 1.65 and 25 min 1). Independent of the screw diameter, the curves coincide for nY = const. The higher the rotational speed, the higher is the shear stress the straight line (a), which is also valid for Newtonian liquids, adjusts as the limit case (p= x ). 

The strong interdependence of process variables is another aspect of the process that requires a high level of operator skill and has led to extensive advancements in measurement and control techniques. There are many process variables - screw speed, nip speed, internal bubble air volume, and cooling rate (frost-line height) - that influence bubble geometry and, as a result, film properties. An adjustment to any one... 

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