How Do I Resolve When Profile Shape Prediction Does Not Match with Real Part?

  1. Determine if the extrusion ratio is over 30 and the profile is thin (<3mm).
  2. Check the profile dimensions and ratio of wall thickness (thickest leg to thinnest leg).
  3. Check the difference in billet and tool temperatures.
  4. Check if the billet has taper heating.

When the extrusion ratio is large and the profiles are thin with and/or the difference in billet preheat and container temperatures is greater than 50C we should run the analysis as a transient moving boundary.

Other situations that could cause these differences are: Large differences in wall thicknesses (some regions are thicker (5 times or more) than other section and non-uniform heating (taper) of billet. Under these conditions, running steady state analysis will produce incorrect temperature filed and this can result in calculating wrong flow filed and hence the differences in shape predictions.

If the profiles are bulky (thick), the wall temperatures will not have a big influence on the temperature at the center. Therefore, running a steady state simulation can produce accurate shape predictions. When extrusing thin sections, we must pay attention to the differences in temperatures between tool and workpiece and run steady state analysis only when these differences are small.