VARIABLE INTERMESHING

Variable Intermeshing Clearance (VIC) Rotor Internal Mixer... 

The variable intermeshing clearance rotor mixer is designed to allow a variable clearance between the intermeshing rotors of the mixer. 

The factory system based on internal mixers, screw extruders, calenders, and vulcanization presses has remained basically unchanged in the past half-century. Internal mixers have had major improvements, e.g., intermeshing rotors proposed by Francis Shaw and Company [C16] and Werner and Pfleiderer [L3], and variable intermeshing clearance rotors [PI] proposed by Pomini-Farrel SpA. Sophisticated computer control systems have been introduced. The early single hot-feed extruders have been replaced by cold-feed extruders with increasingly sophisticated design including pin barrel extruders [G7, H12, H13, M18, W16] as well as complex control systems. 

A comparative study was made of the effidency of two intermeshing rotor mixers, one with fixed clearance and the other a VIC 165 variable intermeshing clearance mixer (Techint-Pomini), in the mixing of NR, EPDM and polyepichlorohydrin compounds. The results showed that the variable clearance mixer gave reduced cycle times with equal quality of the compounds produced, and that higher fill factors were possible with this mixer. The cost advantages of the VIC 165 were also analysed. 

PRODUCTION MIXER WITH VARIABLE INTERMESHING CLEARANCE Limper A Moessinger J... 

The authors compare the performance of a variable intermeshing clearance mixer, which offers the possibility of varying the intermeshing clearance between the rotors in addition to the usual adjustable process parameters, with that of conventional mixers with intermeshing rotors. 3 refs. Articles from this journal can be requested for translation by subscribers to the Rapra produced International Polymer Science and Technology. Accession no. 773787... 

Results are presented of a hnite element analysis study of the efficiency of the dispersive and distributive mixing of rubbers in variable intermeshing clearance and transfer mixers. 11 refs. 

DISTRIBUTIVE MIXING IN VARIABLE INTERMESHING CLEARANCE MIXERS SIMULATION AND EXPERIMENTS... 

A variable intermeshing clearance style mixer is an internal mixer with intermeshing rotors that provides technologists and compounders with the ability to control and adjust the variation of the clearance between the rotors. By adjusting the gap between the rotors, it is possible to optimise the amount of energy to be transferred to the compound in accordance to its actual viscosity. The results on mixed compounds presented in this article are based on tests run with industrial sized machines directly at the customer s production facility. 8 refs. 

Manchester, 17th-21st June 1996, poster 5. 012 VIC INTERNAL MIXERS WITH VARIABLE INTERMESHING CLEARANCE... 

Yao, C. H. and Manas-Zloczower, I., Influence of Design on Mixing Efficiency in a Variable Intermeshing Clearance Mixer, Int. Poly. Proeess, 7(2), 92-103, (1997). 

Li and Manas-Zloczower (31) used the CFM commercial FIDAP FEM package to simulate the three-dimensional isothermal flow patterns and distributive mixing in three consecutive filled, closed C-shaped chambers of fully intermeshing, counterrotating extruders, having the dimensions of Leistritz 30.34 (30 denotes the centerline distance and 34 the barrel diameter in mm units). An equal pressure drop per C-shaped chamber was applied for the calculations. The melt was assumed to be Power Law above y() and Newtonian below it. The design, process, and material variables are given by the authors. 

The screw conveyors are intermeshed to break up soil clumps and to improve heat transfer. The four screws of each processor are driven by a variable speed drive... 

A processor does not have control of all the steps from basic material to finished product. Material processing capability is limited by what is received and by when inspection is made or required so selection tests are important and must be subject to change (see Chapter 10). In turn, the process line has many variables that must be coordinated. A practical procedure today, with all closed-loop process control systems, is to subdivide the controls into distinct subsystems (Fig. 3-33). They can then be controlled within single control loops or by simple intermeshed circuits. A single-loop feedback circuit has one input and one output signal disturbances that affect the process are registered by the controller directly, by an ad-... 

Figure 1.9 Passoni s [55] variable clearance intermeshing internal mixer.

Finally, the effect of process variables, such as screw speed, differs with twin-screw extruders. Due to positive conveyance, the output of starve-fed twin-screw extruders (Fig. 5.36 b is independent of screw speed and, to some degree, head pressure. Head pressures and melt temperatures of intermeshing twin-screw extruders are also not as sensitive to screw speed as they are in single-screw extruders. In contrast, nonintermeshing twin-screw extruders exhibit output characteristics that are similar to those of single-screw extruders. A comparison of the characteristics of single and intermeshing twin-screw extruders is summarized in Table 5.9. 

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