The Opportunity
Most extruders today are not yet using single cell die ovens, despite their obvious advantages. If an extruder has made a satisfactory profit for many years while using a chest oven, it is naturally hard for him to become persuaded that he will benefit by the installation of several single cell die ovens. But these are no longer normal times. In today’s unique economy, it is unlikely that any extruder can afford to waste the first one or two billets at the start of every run in order to bring his die completely and uniformly to operating temperature.
For the extruder who saves the cost of a wasted billet on every run, coupled with his saving in energy costs, the return on his investment can be attractively short. Castool has assisted a number of extruders in obtaining government grants for energy conservation.
The Process
Extruding aluminum appears to be a simple process. It is not. A billet of an aluminum alloy is heated until it is soft, then it is pushed through a die which determines the resulting profile. In this very brief moment of extrusion, as the alloy passes through the die, it hardens, the profile is set, and most of the added value on which the extruder depends is generated.
If the die is well designed and well made, the shape that leaves it should meet all dimensional tolerances, have a good surface finish, and be moving at a profitable speed from the first billet to the last. This can only happen, however, if three specific conditions are satisfied. First, the alloy must enter the die at or near its optimum operating temperature. Second, the die must be completely and uniformly at the optimum operating temperature of the alloy being used. Third, the temperature of the die and the exit temperature of the extrusion should remain virtually unchanged from the beginning to the end of each extrusion cycle. Varying the ram speed should not be an option because the dimensional integrity of the profile may then be compromised.
Posted by: Paul Robbins
