Germanium puck slicing on the SG 20: 42% more throughput, half the operator hours

Why move germanium puck slicing to an endless wire loop?

Germanium puck slicing looks like the simplest job in an optics shop: take a thick rod, section it into thin wafers, send them downstream. The customer in this file — a germanium wafer producer supplying infrared optics manufacturers — was doing exactly that, and losing money on both ends of every cut. On the front end, chipped wafer edges. Single-crystal germanium cleaves readily along its {111} planes, and every chipped rim either scrapped a wafer outright or forced the grinding station to eat deeper into the surface to remove it. On the back end, labor: their existing sawing process needed an operator present through every cut, watching, adjusting, unloading, restarting.

Neither cost shows up on a saw's spec sheet. Both show up in cost per shipped wafer — which is why this case is measured end to end, not blade against wire.

What does the as-cut face look like?

The machine is the SG 20 endless diamond wire saw. A closed loop of electroplated diamond wire circulates in one direction at high speed — no back-and-forth reversal, no rotating blade, no reversal marks. For germanium puck slicing the wire runs straight through the rod diameter at feed rates of 10–20 mm/min, and because the abrasive surface renews continuously as the loop circulates, the cut face stays uniform from the first wafer of a rod to the last.

The result on this customer's rods matched what we see across wire-sliced germanium generally: as-cut surface roughness of Ra 0.6–1.2 μm, total thickness variation of 8–15 μm across a 50 mm wafer, and — the number that mattered most to them — no edge chipping. Their incoming inspection had been sized around finding and mapping chipped rims. After the switch, that inspection step found nothing to map.

Smooth, chip-free faces are not just a quality statistic; they are a schedule. Every micron of subsurface damage the saw leaves is a micron the grinding and polishing line must remove. Wafers off the SG 20 entered grinding with less stock to strip and no chip-repair allowance, and the downstream stations sped up without a single change to the downstream machines.

How does one program cut half the labor?

The control software on the SG 20 is developed in-house at Vimfun, and it was written around how slicing shops actually run, not around a generic motion controller. Three behaviors did the work in this deployment:

• Mixed thicknesses in one program. A single cutting job can hold different wafer thicknesses in sequence — say, a run of 5 mm wafers followed by a run of 8 mm from the same rod. The operator keys in the thickness list and quantity once.
• Unattended execution. Once the program starts, nobody needs to stand at the machine. The saw indexes, cuts, and advances through the full list on its own.
• Auto-stop with alarm. When the last programmed wafer is cut, the machine stops itself and signals completion. No operator hovering to catch the end of a job; no rod cut past the plan.

Before the switch, slicing was a full-attendance station. After it, one operator loads a rod, starts the program, and walks away to run other equipment until the alarm calls them back. Across shifts, the customer's operator requirement for germanium puck slicing fell by roughly half — not through headcount cuts at the machine, but because the machine stopped demanding an audience.

Where did the 42% actually come from?

The customer reports overall efficiency up 42% since moving germanium puck slicing onto the SG 20. It is worth being precise about what that number is, because it is not a wire-speed claim. It is an end-to-end figure across their rod-to-finished-wafer flow, and it stacks from three places:

Slicing is one system of a two-system platform

The slicing behavior documented here is one of two control systems on the SG/SGI platform. The other cuts programmed contours from CAD drawings — the capability behind our irregular germanium lens cutting case with Sunny Optical, where crescent-shaped lenses with R1 corners came off the same class of wire. A shop that buys the platform for wafers keeps the option of shapes, and vice versa.

Both cases sit at the front of the same toolchain: wire saws feeding centering, spherical grinding, and polishing stations in the germanium lens manufacturing equipment lineup, part of the full infrared optics processing equipment range. Teams sizing a complete rod-to-coated-lens flow should start from the infrared optics production line overview.