Extrusion system, small-scale

Figure I. Small-scale extrusion system. R = resin powder H = water-cooled hopper E = modified Maxwell extruder S = spinneret M = spin line manifold T = tension indicator W = variable speed wind-up assembly.

Another modular system is often called laboratory equipment it can be used for small scale production and for the laboratory evaluation of small samples. Fig. 11.26 depicts the design and some of the accessories. In the most simple execution a hopper feeds a pair of rollers which are driven by a hand crank. The rollers can be solid and may be equipped with compacting or briquetting surfaces (see Section 8.4.3) or two perforated, geared, intermeshing pelleting rolls (see Section 8.4.2) are installed to accomplish medium pressure extrusion. In a modular fashion the rollers can be motorized, screw feeders can be added, and the rolls may be oriented vertical or horizontal or in any other direction. As shown in the photographs of Fig. 11.27 the roller frame can be totally enclosed for dust control if toxic or hazardous materials are processed. A panel includes controls and instrumentation for data display and collection. 

The effect of sample size and number must be taken into account, if, for example, the mixing quality is investigated in the laboratory on a small machine, and the results are then scaled up to production levels. The number of individual samples and the volume of the individual samples in relation to the total volume should be the same in the laboratory as on the production machine. If in production, for instance, the melt forms 50 strands after extrusion, then 50 partial flows must also be produced by the laboratory-scale machine. This is not always possible or practical with the usually small volumetric flows in model experiments. For this reason, laboratory work often relies on model systems and alternative methods of evaluation. 

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