The dies that are used in the aluminium extrusion process are mostly made of tool steel. It has been observed that the initial costs and the lead time in case of aluminium extrusion dies along with the supporting tools are comparatively lower than that of vinyl extrusions. There are numerous factors that influence the actual cost and the lead-time of the dies used in aluminium extrusion. To get the very best with regard to quality, cost and performance, the die maker must understand the need of other parties in an extrusion process. An important yardstick to measure a successful die is that all the parts of the profile should emerge from the die at a similar speed. The diagram illustrates the use of dies in an aluminium extrusion process.
Dies used in the aluminium extrusion process can be broadly classified into the following three categories.

• Solid (or flat) dies
  Solid or flat dies are applied to produce solid shapes.
  


• Hollow dies
  Hollow dies used in the aluminium extrusion process, produces hollow shapes. In a single die there can be a combination of solid/semihollow, and/or hollow shapes. Two most common and popular types of hollow dies are the porthole and pancake. The advantages of these two types of design are the following:
  • Cost effective
  • Simple manufacturing process
  • Flexibility in design with regard to placement and shaping of the ports and feed
    
  


• Semi hollow dies
  A semi hollow die is used in the production of profiles having semi hollow characteristics. A semi hollow profile partially encloses a void. An example is shown here of a semi hollow profile. Actually the classification as semi hollow die stems from a mathematical formula of tongue ratio. Based on this Tongue ratio semi hollow dies can have designs like flat, pothole, weld plate and recessed-pocket. The most popular design for semi hollow profiles is the dies with port hole design.