SMTY is sufficient material to yield. It is a nest, not a grade. We water-jet the shape at least 1.5 mm over the finished size so your shop still has grind and edge stock. Twenty Dia 38 mm cores do not require an 800 × 1200 mm mother sheet on your floor.
CVD exists because it makes area. KM’s envelope is Dia 800 × 30 mm T. You do not want a full mother plate on a receiving dock in Ohio. You want the cookies. Send finished size. We nest, we cut fat, you receive the blank. Laser grade or optical grade is chosen first — the jet does not change absorption at 10.6 µm.
What “+1.5 mm” is for
Water-jet leaves a cut surface, not an optical edge. ZnSe is soft (Knoop 105–120; Harris, SPIE 1999). The jet exit chips. You need stock for:
- edge chip from jet exit — we also spec chip on cores separately, < 0.762 mm
- your own cylindrical grind or mill
- fixture lands
- the fact that this crystal chips if you load it against a steel jaw
Circle type, square type, thick type — those shop photos are not three products. They are three nest geometries on the same CVD sheet. Sheet-type SMTY slabs exist when your yield math wants a rectangle, not a round. Density 5.27 g/cm³: weigh the piece against CAD volume of the as-shipped oversize, not the finished print, or incoming inspection will think we shorted you.
Finished size vs as-cut size
Tell us finished size, not the size you hope the jet leaves. We add at least 1.5 mm. If CAD already includes +1.5 mm, say so or incoming inspection will see double fat. On the old shop we called water-jet SMTY SMTYSheetWJ. That is still the idea: water-jet, laser-grade or optical-grade sheet, oversized. Ship-to country on the line — this is a selenium compound; SDS travels with the crate.
If you do not want to own a generator, buy a window. If you own a polisher, buy SMTY or a core. Mixing those on one PO is how lead time grows a week of clarification emails.
References. KM Innovation ZnSe datasheet (max plate, density 5.27 g/cm³, Knoop 110) and shop practice (SMTY min. +1.5 mm; core +2.032 mm / ±0.254 mm / chip < 0.762 mm). Harris, D.C., SPIE (1999), fabrication of CVD ZnSe. KM Innovation SDS.