SCREW LENGTH

In a particular extruder screw the channel depth is 2.4 mm, the screw diameter is 50 mm, the screw speed is 100 rev/min, the flight angle is 17° 42 and the pressure varies linearly over the screw length of 1000 mm from zero at entry to 20 MN/m at the die entry. Estimate... 

Fig. 7. Relationship of average fiber length L/Lc and screw length 1/L0 of extruder 1 — introducing fibers into melt zone 2 — introducing fibers into leading zone [47]...

For square pitched screws, Ls = Ds, and the flights are all perpendicular to the screw axis. Extruder screws range from 25 to 150 mm in diameter, with screw lengths typically of 25 to 30 screw diameters. They rotate at speeds from 50 to 150 rpm, and deliver melt at rates from 10 to 1000 kg/h with pressures up to 40 MN/m. ... 

In its simplest form, the ratio of screw diameter is the basis for scaling. The ratio of the large diameter D2 of the large scale unit to the small diameter Z>i of the lab unit is represented by the lower case d as shown in Table 4. The primary scaling variables are channel depth H, screw length L, helix angle cj), and screw speed N. The ratio of the primary variables of the two scales is then expressed as a power of the screw diameter ratio, d. 

Geometric variables screw or inner barrel diameter D, axial screw length L, channel depth h, and clearance between the screw flight and the barrel 5... 

Using the data from Example 6.10, estimate the screw length required to melt the solid bed for a constant channel depth extruder. Estimate the screw length required if the... 

A twin screw extruder with a diameter of 32 mm has a clearance of s=0.15 mm between the screw and barrel. The screw is double-flighted. At a throughput of 50 kg/h (density p = 1000 kg/m3), a speed of 300rpm, and a melt-containing screw length of 1S/D=10, the return flow fraction results in ... 

Figure 342. Extrusion rate/pressure diagram showing the possibility of varying the capacity while maintaining pressure by a combination of screw length and baffle controls...

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.

Pressure and temperature profile as a function of the degree of fill and screw length [Michael et al., 1991, 1993, 1995 Michael and Grefen-stein, 1996]. 

Rheology and chemical reaction (heat balance ) as a function of screw length [Chen et al., 1996 Kye and White, 1996 Hu et al., 1996b]. 

Variation of morphology along the screw length [De Loor et al., 1996b]. 

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