Extrusion lines

The extrusion line must be capable of running the sheet in a highly controlled and precise environment, to make sure the lenticules are accurately placed (6). Extrusion must also be a clean process in order to prevent image-altering contamination. Sheets are usually extruded in a thickness range of 0.015 to 0.100 in. (0.038 to 0.254 cm). 

For uniform and stable extrusion it is important to check periodically the drive system, the take-up device, and other equipment, and compare it to its original performance. If variations are excessive, all kinds of problems will develop in the extruded product. An elaborate process-control system can help, but it is best to improve stability in all facets of the extrusion line. Some examples of instabilities and problem areas include... 

This term is used both to describe designs that are etched or engraved in the mold surface and the process of inserting a printed film into the mold, to be produced as an integral component of the finished product. Etched surfaces can be drawn both parallel and perpendicular to a parting line of molds or postforming in an extrusion line.. However, be alert with molds to the fact that parallel to the parting line additional draft is required. A wide selection of patterns is available and new ones can be readily created. 

This paper presents the world s most productive extrusion line for PCR tires. 

The target output capability for such a multiplex extrusion line is 25,000-30,000 treads per day. This results in a rubber processing capacity of 10,000 kg/h. 

Only a PLC-controlled extrusion line with recipe management can fulfill the stringent quality control required for high-tech radial tires. 

The total of the necessary equipment constitutes an extrusion line, which includes ... 

Figure 5.12 displays a diagram of a blown film extrusion line. 

A 40 mm diameter laboratory extrusion line was used to make demonstration parts using a specialty PE resin. The desire was to build a larger line with considerably higher extrusion rates. The shear viscosity of the resin is shown in Fig. 9.1. For the temperature range of the process, the heat capacity and thermal conduc-... 

A profile extrusion line was required to increase its rate from the current 75 kg/h to about 230 kg/h in order to meet business demand. The extruder was 88.9 mm in diameter and was running a HIPS resin. Operation of the existing extrusion equipment, however, caused the extrudate temperature to be too high at rates higher than about 80 kg/h. The objective of this project was to increase the rate of the profile line from the current 75 kg/h to a maximum rate of 230 kg/h while maintaining the extrudate temperature below 195 °C. 

It is imperative that the processor utilize every advantage available to ensure success since the specification of equipment in an extrusion line also affects resin usage and labor. Thus, it is always more cost effective in the long run to design and install an extrusion line that (1) has a maximum rate capability of at least 25% more than the expected maximum rate, and (2) has a properly engineered line (that might have a higher capital cost) to achieve maximum profitability. 

Table 12.2 Screw Channel Dimensions for a 63.5 mm Diameter Screw Running GPPS Resin for a Profile Extrusion Line...

Four complete extrusion lines for the manufacture of PE pipes are described which are to be supplied by Battenfeld for Moscow s district heating system. The heating system utilises freely layable steel pipes the conveying the superheated steam, the steel pipes being protected and insulated by means of the PE pipes. The cavity is filled with an insulating layer of PU foam. 

Fig. 11 Foamed sheet extrusion line. 1 Primary extruder, 2 blowing agent metering and flow control, 3 screen pack/breaker plate, 4 secondary extruder, 5 annular die, 6 cooling mandrel, 7 guide rolls, 8 winders. [38]...

Extruded polystyrene foam sheet is primarily produced in a single screw tandem extrusion line. Primary application of foam sheet is as a packaging material in items such as disposable dishes and food containers, trays for meal, poultry and produce products, and egg canons. 

The die is maintained in close proximity (typically 40 mm to 80 mm) to the chill roll so that the low-strength melt web remains unsupported for a minimal distance and time. If the die is too close, there is insufficient space for thickness draw-down and widthwise neck-in (Figure 5.8 where m = width at die, f = width on chill roll, m - f = total neck-in) to take place in a stable manner. With neck-in a beading occurs on both edges of the film. Down the extrusion line these beads are later trimmed away.200... 

Figure 5.18 Example of a wire coating extrusion line...

Different methods are used. An online ordinary common blown or cast film line uses a machine direction orienter (MDO) on the front end of biaxially oriented film heated chamber extrusion line. If only the machine direction is to be stretched, a series of precision controlled heated rolls can be used. Film is fed through a series of rolls where it is sequentially heated, drawn around rolls that increase in rotational speed providing the stretching action, annealed around larger diameter roll(s), and cooled on a final roll(s). 

Due to the plastic s viscosity, a melt shear effect is developed throughout the process. This shear is of prime importance between the calender rolls. The calender forms the web as a continuous extrusion between the rolls (Chapter 1). Unlike when processing just through a conventional extrusion line, the plastic mass cannot be confined when being calendered. Because of the lack of confinement, the shear effect and a broad melt band are essential aspects of calendering. 

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