Aluminium extrusion

Extruded aluminium surface defects

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Identify and understand extruded aluminium surface defects with our comprehensive guide. Explore different types of defects and their causes.

All presented surface defects are classified into three sections for reasons of their occurrence:

The document is intended to facilitate coordination between customers and manufacturers of extruded aluminium profiles by providing agreed terminology, description and images that are understandable to both parties. It can also be useful in training new employees in the production and supply of extruded aluminium profiles.

Below are examples of defect descriptions and brief information on the content  of sections 1, 2 and 3 of this catalogue of defects.

1 Extrusion-press-related surface defects

1.1 Pickups (pick-ups)

Small particles of aluminium and aluminium oxides that were torn from the surface of the aluminium profile and later settled on its surface again. They are in the form of a comma or comet, which are oriented in the direction of extrusion. May occurs in connection with the “die lines” defect [4].

Torn, comma-like spots on the surface of extruded products caused by a local material deposition on the surface of the die [5].

the "pick-ups" - extruded aluminium surface defects

Picture 1 – Schematic view of the “pick-ups” defect [4]

“Comet tail” appearance of the "pick-ups" surface defect

Figure 2 – “Comet tail” appearance of the “pick-ups” defect [3]

Model of the “pick-up” aluminium extruded surface defect

Figure 3 – Model of the “pick-up” defect [7]

1.2 Die lines

Grooves running in the direction of extrusion, which often end at points where alumi-nium material particles adhere. May occurs in connection with “pick-ups” defect [4].

Continuous longitudinal line formed on an extruded product caused by minor irregularities and/or the build-up of aluminium or non-metallic inclusions on the bearing surfaces of the die [5].

Micro die lines. Even with an optimum die bearing length and extrusion temperature, together with highly polished die bearings, die lines are still observed to occur. These die lines are finer and shallower and are termed micro die lines [3].

Schematic view of the "die lines" defect

Figure 4 – Schematic view of the “die lines” defect [4]

Die lines and micro die linesFigure 5 – Die lines and micro die lines [3]

Further  this section 1 includes 13 more defect types and 20 more images.

2 Metallurgical-related surface defects

The section 2 includes 8 defect types and 14 images.

 

3 Mechanical-related surface defects

The section 3 includes 12 defect types and 20 images.

References

  1. P. K. Saha, Aluminum Extrusion Technology – ASM International, 2000.
  2. Extrusion of Aluminium Alloys / T. Sheppard – Springer Science+Business Media Dordrecht, 1999
  3. Extrusion Defects Fundamentals & Solutions for Optimum Finish / J. Fourmann – Rio Tinto – 2017
  4. Merkmale von Aluminium-Strangpreβprofilen – IWK, Aachen, 2001
  5. GAG Guidance Document 001, Terms and Definition – 2011.
  6. Product defects in aluminum extrusion and their impact on operation cost / A.F.M Arif et al, KFUPM, Saudi Arabia, 2002.
  7. Surface quality of aluminium extrusion products / X. Ma, PhD Thesis – University of Twente, The Netherlands, 2011
  8. Defect Analysis in Anodizing / Barry R. Ellard – ET 2000 – 2000
  9. The Identification and Prevention of Defects on Anodizing Aluminium Parts / T. Short – Metal Finishing Information Service Ltd – 2003.
  10. Care of Aluminium – https://www.hulamin.com – 2021

 To be continued.