Extruder feeding system

USATHAMA) completed a trial burn of explosive, contaminated soil in a rotary kiln (Noland, 1984). Soil contaminated from red and pink water lagoons was successfully burned. A transportable rotary kiln yrstem was set up. The technology by Therm-All, Inc., had been used in industry for destruction of solid wastes. The normal screw feed system was not used, due to fear of a soil explosion during the extruded plug feed process. Therefore, the soil was placed in combustible buckets and individually fed by a ram into the incinerator. The feed rate was 300 to 400 Ib/hr and the operational temperature was 1200° to 1600°F in the kiln and 1600° to 2000°F in the secondary chamber. 

The material flow in an internal mixer is oriented vertically. On top of the internal mixer a more or less sophisticated feeding system can be found. Underneath the mixer a downstream device, such as a sheeting extruder with one or two tangential screws, or two roll mills are placed. 

The feed section takes the product from the feeding system and conveys it to the plastification section. At the same time, there must be sufficient free volume to allow gas reflux, e. g., air or nitrogen, to escape from the process section upstream. If the throughput rate of the extruder is less than the input product flow, the product will back up in the feed hopper, indicating that the intake limit has been reached. Along with the known extruder data, such as the screw speed, the screw pitch, and the available volume in the screw channel, other influencing factors, such as the fill rate of the screw channel, the conveying efficiency, the bulk density, and other bulk characteristics of the product sometimes affect the... 

With very large volumes a fully integrated in-line, closed loop system can be justified. The line is fed with plastics raw material, with extruders feeding directly into the thermoforming machine. 

FIGURE 14-6 Schematic diagram of the feed system for a single screw extruder. 

Hot feed systems Strips of green compound are fed from warm-up mills into an extruder feed box and then into the barrel. 

Cold feed systems Mixed compound is fed directly into the extruder system. 

This extrudable PVC has found use as tubing for blood transport and delivery systems, dialysis and enteral feeding systems, oxygen delivery systems, catheters, and drainage systems. Product numbers containing an R are special radiation resistant grades (Tables 4.6, 4.12 and 4.13). 

The feed system holds the solid material and delivers it to the extruder. The main components are the hopper and the feed throat. A material handling system (e.g., silo and vacuum loader) may transport the raw material to the hopper. 

Bayer R (2003) Feed system for continuous supply of loose materials to an extruder comprises a side screw feeder through which material is drawn by an air flow and then separated from the air by a screen. DE10201869... 

The Conex system is a relatively recent development that has introduced radical new thinking to co-extrusion. The conceptual idea was by Kirjavainen a research worker at VTT, Tampere, Finland, but the system has been developed by a collaborative venture between Uponor, NK Cables and Nextrom [58]. Instead of thinking in terms of separate extruders supplying a multiple die-head, the Conex system integrates the extrusion process and the die-head as a multiple material feed system. 

The most important component of the feed system in a flood-fed extruder is the feed hopper with possible stirrer and/or discharge screw. A mechanical malfunction of this system can be determined by visual Inspection. If the feed hopper is equipped with a discharge screw (crammer feed), constancy of the drive should be checked. For proper functioning of a crammer feeder, the drive of the crammer feeder should have a torque feedback control to ensure constant feeding and to avoid overfeeding. 

---