Rotating speed of the screw

Since quite a bit of difference exists between raw materials, the recipe, and the equipment, the processing procedure and conditions vary a lot. Also, the processing procedures of commercial products are usually not available to the public. Thus, much work needs to be done to find the best procedure and condition for each individual system. In general, a good procedure is a combination of optimal processing time, temperature, and rotating speed of the screw (in the case of extruder use) or the roll nip (in the case of calender use). 

The rotation speed of the screw to that of the motor is simply ... 

A single screw extruder has two Reynolds numbers. One, Re = pD2n/r]o, related to the rotational speed of the screw, and another, ReQ = Qp/rjoD, related to the mass throughput. The ratio of the two gives the dimensionless throughput ReQ /Ren Q / /) n. ... 

In extrusion problems, the rate of deformation is directly proportional to the rotational speed of the screw. Hence, a characteristic viscosity can be defined as... 

Processing conditions - Heater temperature, T, and rotational speed of the screw, nu... 

Because extruders were initially developed to serve industries other than the pharmaceutical industry, they were designed without GMP considerations. Therefore, changes are made to ensure pharmaceutical regulatory compliance, including qualification requirements. At the minimum, all the parts of the extruder that come in contact with the product must be of high-quality stainless steel, and the construction must be such that cleaning requirements are easily met. Whenever possible, the machine should permit easy monitoring and documentation of all critical process parameters such as pressure at the die plate, product temperature, power consumption or torque of the drive unit, and rotational speed of the screw. Some of... 

The pyrolysis experiments have been conducted in a horizontal tube with an internal diameter of 4 inch. The feedstock is transported through the tube by a screw. The residence time of the solids can be varied by adjusting the rotation speed of the screw. An electrical furnace supplies the heat required for the pyrolysis process, and the reactor is continuously purged with Argon. The process conditions used fw the pyrolysis experiments are given in table 1. 

It is important to minimize the rotation speed of the screw. High speeds can be used, in conjunction... 

Within TSE the shear and extensional stresses are generated by virtue of interactions between two screws. The degree to which this occurs depends on the relative direction of the screw rotation (co- or counter-rotating), shapes of the screw elements, the degree to which they intermesh, and the rotational speed of the screws [Fisher, 1958 Matthews, 1962]. 

The controlling geometric parameters that characterize the extruder are the screw diameter D and the length to diameter ratio UD. Extruders are categorized according to diameter, from which the output and the power demand for a given rotating speed of the screw are derived. 

Frictional heat is also produced by this motion. The homogeneity of the melt-an extremely important factor in obtaining high-quality moldings-is decisively influenced by the temperature of the cylinder wall and the rotational speed of the screw. While thermoplastics are heated to a temperature of 180-300°C (360-570°F), elastomers are heated to only about 100°C (212°F) in order to prevent premature cross-linking. 

Also in this equation the effects of drag flow and pressure flow can be separated the drag flow is proportional to the rotational speed of the screws, and the pressure flow is proportional to the ratio of pressure gradient and viscosity. 

The rotational speed of the screws is a parameter that still can be chosen freely, provided that the die resistance is adjusted such that... 

The position of the reaction zone in the extruder is dependent on temperature, throughput, and the rotation speed of the screws. These parameters also determine the starting point of the reaction the temperature, especially, has a large influence. The influence of the other parameters on the position of the reaction zone are marginal. Normally, the reaction starts in the partially filled zone. 

Table 4 I nfluence of the Rotation Speed of the Screws on the Polydispersity of the Polymer...

It is important to minimize the rotation speed of the screw. High speeds can be used, in conjunction with the appropriate backpressure, to mold thin and/or long parts. Injection pressure should also be as low as possible. Dimensional stability improves when pressure is lowered because of a reduction in the residual stresses in the molded part. Injection pressure may have to be increased if an improvement in the weld line or a reduction in sink marks is desired. Part design and equipment capability should always be considered in the selection of injection pressure. Backpressure should be kept at the lowest possible value. Increasing it can sometimes help increase the stock temperature. 

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