Anodizing defects: stripes from matrix marks, welds and sink marks

This type of defectType 1-B – species “banding”, but because of contaminated metal from the surface layer of the ingot, as in Type 1-A, or strips with a large grain, “rough” structure, as in Type 1-B. Defects of this type arise due to damage to the girdle matrix, as well as violations of profiles extrusion technology for anodizing, for example, too short press residue.

See. Defects aluminum anodizing – classification

Следы матрицы (риски)

English term

Die lines.

defect Source

Pressing

The manifestation of the defect

Pressing - Anodizing.

Details of the defect

Этот вид дефекта анодирования – это обычно отдельные риски на поверхности отпрессованного алюминиевого профиля (рисунок 1.7), which result from damage or girdle matrix gripping them contaminants, included, стальных частиц (например, частиц азотированного слоя или продуктов трения стенки контейнера). Depending on their depth, some traces of matrices may only manifest after etching, others will be visible even after the mechanical polishing or machining profile and abrasive brushes.

sledy-matricyFigure 1.7

Preventing defect

Avoid traces of matrices is possible only with full confidence, what:

  • on the workpiece and the tool prior to compression and in the course of it completely lacks any contamination,
  • girdle in the matrix no damage.

Not too deep traces of the matrix are removed or masked after alkali etching E6.

Transverse welds

English term

Тransverse welds

defect Source

Pressing.

The manifestation of the defect

Travlenye - Anodyrovanye.

Details of the defect

Этот дефект возникает на переднем конце каждой заготовки (кроме первой) при прессовании сплошных алюминиевых профилей на матрице со сварочной камерой и для всех полых профилей. This defect arises due to the inevitable oxide layer, appearing at the junction between the cut surface in the aluminum matrix ports and the front end face of the next workpiece.

The defect is in the form V-shaped edge strip with V, directed toward the front end of the pressed aluminum profile. This defect is shown in Figure 1.8.

For aluminum profiles, to anodization, часто (но не всегда) необходимо вырезать эти участки и отправлять их в лом. Many Extruders are looking to reduce the amount of internal scrap, and therefore increase the risk of manufacturing profiles, comprising transverse seams.

poperechnyy-shovFigure 1.8

Preventing defect

  1. Avoid the use of ingots from a variety of sources, various heat treatments or different mold structure for manufacturing a batch of profiles.
  2. One way to reduce the length of the transverse seal is to decrease the volume of metal in the matrix ports. This makes the stitch shorter, but more prominent, that makes sense, if it will later be removed.
  3. Net of the discard cut surface makes it possible to "mask" the transverse seams, including, by a minimum of grease on the blade of the knife compartment of the discard mechanism.

Utyazhina

English term

Вack-end-Defect (также сoring и piping)

defect Source

Pressing.

The manifestation of the defect

Travlenye - Anodyrovanye

Details of the defect

dark streaks, usually, inclined at an angle to the pressing direction. They usually are not visible on the profiles of the pressed state or after mechanical processing. Shown after etching and anodizing of aluminum profiles. This type of "banded" material contains defects "segregate" and oxides from the peripheral zone of the ingot. This material must not enter the profile, but it can reach the last stage of compression of the end of the blank.

In the book T. Sheppard "Extrusion of Aluminium Alloys" this defect appears as shown in Figure 1.9.1. On the image 1.9.2 from book P. K. Saha “Aluminium Extrusion Technology” shows a model of the formation of this defect. Often this defect has a tubular shape, and it is also called «piping -« sink mark ".

back-end-defectFigure 1.9.1

back-end-defect-sahaFigure 1.9.2

Preventing defect

Increasing the thickness of the discard.

Source: Barry R. Ellard, Aluminum Extrusion Technology, 2000