Aluminum Extrusion Troubleshooting

Blow out or inflation, convex (rounded top and bottom, light or heavy walls) (LR)

Problem Description

The extrusion exhibits outward bulging or convex deformation, often in hollow sections with light or uneven walls.

Cause–Correction Mapping
  • Bearing not flat
    Cause in: Die

      Corrections

    • Square the bearings perpendicular to die face, flatten bearing perpendicular to metal flow.

  • Caved in die (core, mandrel, housing) that creates a core bearing lower than plate bearing
    Cause in: Die

      Corrections

    • Replace die components as required.

    • Check support tooling for flatness and hardness.

    • Cut die face to provide shear edge where sufficient bearing length exists.

      Disadvantage: Shortens die life, temporary fix.
  • Core shifted
    Cause in: Die

      Corrections

    • Check support tooling for flatness, hardness.

    • Check for cracked armpits, webs, replace tool.

    • If delivery is critical, open thin walls to balance.

      Disadvantage: May shorten die life.
  • Excess billet temperatures
    Cause in: Equipment

      Corrections

    • Reduce billet temperatures

      Disadvantage: Reducing billet temperature may reduce production.
  • Excess extrusion speed
    Cause in: Equipment

      Corrections

    • Reduce extrusion speed.

  • Mandrel bearings too long
    Cause in: Die

      Corrections

    • Reduce bearing length on mandrel/modify lengths as required to balance flow.

      Advantage: Increases in production, proper shape and lower scrap rate.
  • Washed out mandrel bearing
    Cause in: Die

      Corrections

    • Smooth mandrel bearings/consider die replacement.

      Disadvantage: Might make section overweight and walls heavy.

Please note that the information provided in this article is intended to be a general guide to the causes and corrections of Blow out or inflation, convex (rounded top and bottom, light or heavy walls) (LR) in aluminum extrusion. However, it is important to note that the specific cause and correction of any particular defect will vary depending on the specific extrusion process, alloy, and other factors. Therefore, it is important to consult with an experienced and professional engineer to ensure that the correct diagnosis is made and the most suitable correction is chosen.