New life for hot feed extrusion lines.

There are many hot feed extruders nearing retirement in tire manufacturing facilities in the U.S. and throughout the world. As industry requirements become more reliant on multiple compound extrusions, the old hot feed extruders which make single profiles are becoming obsolete. Even opposed-head dual hot feed extrusion lines cannot make the current profiles, which are becoming the norm.

Instead of abandoning the old hot feeds. Akron Steel Fabrictors (ASF) is suggesting to users to look at a modernization program which can take the old equipment and transform it to new technology. This allows extrusion lines already in place to remain productive and limits overall project costs using a "building-block" approach.

The building blocks

Extruder

Foremost in the need for modernization is the hot feed extruder itself. The old single or opposed extrusion head can be replaced with a state-of-the-art triplex (or even quadraplex) unit specifically designed for the multi-compound profiles required. Figure 1 shows a typical triplex head of new design. The heads are manufactured by A-Z Formen- und Maschinenbau GmbH of Germany (A-Z). ASF and A-Z have formed a working partnership to offer new heads and extruders for converting old extruders.

[Figure 1 ILLUSTRATION OMITTED]

The new heads offer flexibility in that the head can be purchased and used as a duplex unit before adding the third (or even fourth) extruder. This allows costs to be controlled while still moving ahead with new technology. Due to very short flow channel paths, the heads are very compact and easy to open for cleaning or tool changeout.

In conjunction with the new head, one or more of A-Z's Multicut Transfermix (MCTD) cold feed extruders are added for the new profile flow paths. The MCTD extruders offer very short L/D ratios and are compact. They have the unique capability of excellent control of output temperature in relation to throughput volume. This control does not require removal of pins, etc. The MCTD section of the barrel and a throttle mechanism after it allow operators to tune output temperature while in operation.

Since the heads and extruders are relatively small, layout of additions for modernization take up little room in an existing space. A typical triplex unit is shown in figure 2.

[Figure 2 ILLUSTRATION OMITTED]

Controls

Partial or complete modernization of extrusion line controls, including conversions to all variable speed A.C. drives using non-contact loop sensors, recipe driven continuous weigh systems, etc., all accessed through touch panel screens is offered.

Cooling conveyors

Many old extrusion lines use very inefficient conveyor belts with one-side cooling. Thus, their length is very extensive due to poor heat transfer. Conversion sections which use top-and-bottom spraying with open-area acetal or polypropylene belts can be fabricated. These belts offer positive tracking as a side benefit besides their cooling efficiency. In many cases, the overall length of the line can be shortened, or heavier profile sections be cooled within the same dimensional limits.

Booking conveyors

One typical complaint of booking conveyors is the noise that they make. In some plants, the operators are required to wear ear protection in the booking area. A non-corrosive roller conveyor utilizing polymer o-ring roller drive, low noise bearings and "slip rings" is available. The slip ring design allows the tread to be stopped by hand due to the low backpressure rollers. Since no chain is used, the booking conveyor runs quiet at maximum line speed.

Engineering survey

The joint efforts of ASF and A-Z can be focused on the customer's exact needs by use of a line and product survey. Our combined engineering group can review and recommend solutions based on existing or future requirements.

Manufacturing

The engineering and fabrication of extruder modernization components use the strengths of both companies to achieve the best value and delivery. A-Z is responsible for the manufacture of the extrusion heads and MCTD extruders, while ASF completes the package with the extruder bases, extruder motors and drives, all electrical panels, hydraulic controls and the full assembly on ASF's shop floor. The unit can be functionally tested before shipment.

Project coordination

ASF offers complete project management, from initial proposal through turnkey supply and installations. ASF and A-Z engineers work as a team to insure that proper equipment is specified and built, delivery targets are met, etc.

Conclusion

The entire idea of "saving" the old hot feed extruders makes good sense in this time of limited budgets. Meeting the needs of tire extrusion manufacturing can require completely new, expensive systems with long justification studies or a more efficient, step-by-step modernization, which may just be the ticket for the return-on-investment (ROI) required by management.