Die machining  
 
 

 

Profile designing

Die designing

Die machining

Extrusion

Anodizing

Powder coating

Wrapping

Fabrication

Aluminium glossary


 
 Extrusion die making processes
 

 

   
 

Die making

 

Die making involves many steps and processes starting with receipt of a profile drawing from the customer to the shipment of a die. Two distinct areas require consideration in die making. In first area, the die must be manufactured based on economic and extrusion productivity. In the second area to be considered, the die manufacture must provide for maintaining the highest quality and reliability. Modern technology allows the die
manufacturer to reduce the number of steps gradually.

 

Die correction

 

Once manufactured the die is sent to the press for testing and production or for testing only, depending on the critical features of the extrusion. Despite the introduction of CAD/CAM and CNC in the design and manufacture of aluminium extrusion dies. The shape and finish of the product may not be accurately predictable. If the produced shape is successful at the first trial, production continues with proper checks and measures,
If the extrusion does not succeed, the die needs to be corrected based on the the report of the test run along with the front piece of the extrusion. Die corrections or maintenance could be required due to many reasons, such as improper metal flow, dimensional variation, surface finish and any interference with run out table. However, die correction procedures require considerable practical experience. There are many ways to correct the same problem:

 

  -    Taper billet heating
  -    Change the extrusion speed
  -    Press alignment and adjustment
  -    Deflection of die stack
  -    Rotating the die to change its position
  -    Use of lubricant
  -    Use of canister guide
In addition, problems associated with the press can include the following: improper tool stack, flatness of the pressure ring, improper sealing of the die with the container liner, a washed out container liner and worn out dummy pads.

 
Photo: Extrusion process
1.Die, 2.Backer, 3.Die holder, 4.Die stem, 5.Stem holder, 6.Bolster
 

Solid Die

 

Correction of a solid die requires either modification in the pocket or the feeder plate or modification of the bearing length from the front or exit side of the die. The proper method of correction should be using a milling
machine instead of flexible grinder, an old carbide-tipped method. A milling cutter is used to do the machining on the hardened steel. The amount of modification done using the milling machine can be measured and recorded for further communication with the die designer or manufacturer.
Correction may also be associated with dimensions of the wall thickness of the section. Similarly, the die corrector should communicate this information to the die manufacturer to change the program in the wire EDM.

 

Hollow Die

 

The correction of hollow die is very complex compared to that of a solid die, because the aluminium is flowing through three stages : Billet to Mandrelport, Mandrelport to Weld chamber, Weld chamber to Final shape.
There are many variables associated with hollow dies such as ports, depth on bridge and the weld chamber cavity. the correction of hollow dies could be due to twist, angularity, split corners, convex wall, concave wall and uneven wall.
To correct the flow on a hollow die the port first before working on the bearings. Ports control the volume of metal which needs to be balanced in relation to the cross-sectional area of the extrusion that each port is feeding.

 
(a) Choke at the front of bearing; (b) Increased relief angle at the back
 
 
 
 



2010 ...... All rights reserved.