Flight depth

Max. screw speed = 100 rev/min, screw diameter — 40 mm flight depth (metering zone) = 3 mm. 

The size of flight radii on the screw channel is important for the proper performance of a single-screw extruder. The specifications of the flight radii are commonly made using a combination of personal experience and guidelines [16] from the Society of the Plastics Industry, Inc. (SPl). These guidelines state unless otherwise specified the root radius will not be less than one-half of the flight depth up to... 

Large degassing surface and/or thin melt (flight depth, and degassing zone length number of flights)... 

Igel elements (Fig. 12.26), which were also developed very early on, aptly named after their resemblance to a hedgehog. In these elements, a basic conveying element is overlapped with a backward-pumping element with the same pitch and flight depth. Very sharp edged ( spines ) are formed to divide the melt flow. 

An exception to this are very fine powders that can be pneumatically entrained by returning interparticle air in front of the left-handed plastification zone, drastically reducing the potential throughput. Air speeds decline with increasing flight depth, which explains why the ZSK MEGAvolume has stand the test for these products. 

Transition Zone-. It is the section, also called the compression zone, of a screw between the feed zone and metering zone in which the flight depth decreases in the direction of discharge. In this zone the plastics starts in both solid and molten state with target to have all molten upon leaving this zone. 

In the flight depths illustrated in Figure 12.12, a distinction is made between standard screws and shallow-flight screws. Shallow-flight screws pick up less material and, as a result, the residence time is the plasticizing unit is shortened. This can be advantageous when utilizing thermally sensitive additives, such as colorants, or when the part production rate is a small compared with extruder capacity. 

Figure 6.12 Features of a typical extrusion screw. Key L= screw length, D = diameter, h = initial flight depth, hi = final flight depth. L/D = length/diameter ratio, h/hl = compression ratio.

The change in flight depth along the screw (i.e., the ratio of the solids metering channel depth to the melt pump channel depth) is known as the... 

L 1 drum length, m radial flight depth, m Greek Symbols ... 

A a three-zone screw with feed section of constant flight depth, a compression section (it is the geometry and position of the compression section that are designed to match the melting or softening characteristics of the polymer), and a metering section ... 

The first metering zone has length = 250 mm, and flight depth H, = 4 mm. The second metering zone has length = 500 mm, and flight depth Hi 6 mm. 

Flight depth Flight width Barrel diameter Length of metering zone Heine angle ... 

First metering zone length = 360 ur flight depth = S.7 nun and flight width = 12 mm. 

Second metering zone length = 600 nun flight depth = 8.25 mm and flight width = 12 nun. 

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