General Catalog - DR. JOHANNES HEIDENHAIN GmbH - #5

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5 Precision Graduations—the Foundation for High Accuracy The heart of a HEIDENHAIN encoder is its measuring standard, usually in the form of a grating with typical line widths of 0.25 ìm to 10 ìm. These precision graduations are manufactured in a process invented by HEIDENHAIN (e.g. DIADUR or METALLUR) and are a decisive factor in the function and accuracy of encoders. The graduations consist of lines and gaps at defi ned intervals with very little deviation, forming structures with very high edge defi nition. These graduations are resistant to mechanical and chemical infl uences as well as to vibration and shock. All graduations have a defi ned thermal behavior. Phase grating with approx. 0.25 ìm grating height DIADUR DIADUR precision graduations are composed of an extremely thin layer of chromium on a substrate—usually of glass or glass ceramic. The accuracy of the graduation structure lies within the micron and submicron range. AURODUR AURODUR graduations consists of highly refl ective gold lines and matte etched gaps. AURODUR graduations are usually on steel carriers. METALLUR With its special optical composition of refl ective gold layers, METALLUR graduations show a virtually planar structure. They are therefore particularly tolerant to contamination. Phase gratings Special manufacturing processes make it possible to produce three-dimensional graduation structures, possessing certain optical characteristics. The structure widths are in the range of a few microns down to quarters of a micron. SUPRADUR Graduations manufactured with the SUPRADUR process function optically like three-dimensional phase gratings, but they have a planar structure and are therefore particularly insensitive to contamination. MAGNODUR Thin magnetically active layers in the micron range are structured for very fi ne, magnetized graduations. DIADUR and AURODUR graduations on various carrier materials