In case of rubber extrusion dies there is a great challenge for the extruders. The dies are to be designed in a manner to get the material to flow naturally through the thick sections and at a considerable distance from the thin edges. Then there is the problem of the flow pattern within the die leading to flows that are too unbalanced for an efficient extrusion process of the desired product. Another problem is that of swelling of the rubber after it exits the die, which is also not acceptable. Two types of rubber extrusion dies are popular and they are preform and final die. Another popular die is the coin or plate die used in the extrusion process of silicone rubber. The following image is of a rubber extrusion die.
Let's see the position of extrusion dies in an extrusion line for producing extruded rubber products.



Die design of Rubber Extrusion Dies

• The first and foremost consideration of a good extrusion die design is the avoidance of dead spots. Actually these dead spots tend to catch and hold the rubber as soon as it approaches the die. If a quantity of rubber to be extruded gets trapped in the extruder for a considerable period, there is every chance that due to frictional heat the rubber may get vulcanized, leading to all sorts of troubles.
  
  
• There should be uniform flow of rubber through all the parts of the die.
  
  
• Die designs should be flexible enough to allow for corrections or adjustments.