Step 4: Material Selection And Surface Structure

Material Selection

The material question initially seemed problematic because the manufacturers of high-quality vibraphones on their websites give the impression that they are using specially developed alloys. This is possible, but based on our current level of knowledge it seems rather unlikely. Any kind of special alloys would have been unsuitable for us due to the small quantities and the associated costs. For the same reason, it appears to be unlikely for other manufacturers, unless they produce large quantities.

It was clear that we need hardenable aluminum alloys with higher strength for the bars, that are available as plates or profiles. The following therefore came into question:

  1. EN AW-7075 (AlZnMgCu1,5)
    tensile strength approx. 550 N/mm², not suitable for decorative anodizing, hardness HB 150
  2. EN AW-2024 (AlCuMg2 / AlCu4Mg1)
    tensile strength approx. 450 N/mm², not suitable for decorative anodizingn, hardnessHB120
  3. EN AW-2017A (AlCuMg1)
    tensile strength approx. 390 N/mm², not suitable for decorative anodizing, hardnessHB 105
From this group, only the third position material EN AW-2017A was available at low cost in our small quantities, so the decision for this material was quickly made.
It is conceivable that a harder material would possibly achieve slightly better sound results.

Surface Structure

For a first try, we had a bar blasted with glass beads before anodizing. This looked very good before anodizing, but after anodizing the surface was very stained, since the smallest difference in concentration of the blasting was emphasized by anodizing.

We then only lightly brushed our bars by hand with standard polishing mats in the longitudinal direction in order to obtain a reasonably uniform and not too reflective surface. The resulting surface structure remained visually very pleasant even after anodizing.