Heat checking inside of hollows
Problem Description
Internal cracking or tearing occurs inside hollow sections.
sometimes visible from outside, but only in extreme cases); causes scrap, defective extrusions and possible wall thickness problems;
Cause–Correction Mapping
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Absence of undercutCause in: Die
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To assist in identifying these problems:
• When viewing appearance from outside extrusion, distorted area is sometimes shiny.
• When viewing from inside, appearance is similar to cracks shown below.
• Tear and crack lengths an widths vary.Depending on shape and number of cavities, grind shear edge in front of the bearing approximately 0.5mm to 1.5mm in depth: no more should be needed.
General practices indicate that presence of shear edge, within dimensions indicated, usually eliminates this condition.
Corrections
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Uneven flow creating internal shear (tearing)Cause in: Die
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Depending on shape and number of cavities, grind shear edge in front of the bearing approximately 0.5mm to 1.5mm in depth: no more should be needed.
Disadvantage: None as long as the shear edge is uniform around the bearing so that the pressure on the bearing is equal.
Corrections
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Please note that the information provided in this article is intended to be a general guide to the causes and corrections of Heat checking inside of hollows 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.