Okamoto ACC-2040DX

A hydrostatic spindle uses pressurized oil pumped between the spindle shaft and the spindle housing to create a frictionless, contact-free bearing. Unlike ball or roller bearings (which have rolling element contact), hydrostatic spindles run with zero solid contact — the shaft floats on an oil film. This provides: (1) zero vibration from rolling elements — surface finish improvements of 20–40% are typical; (2) excellent damping — the oil film absorbs grinding vibration rather than transmitting it to the workpiece; (3) thermal stability — no bearing heat generation from rolling contact; and (4) virtually unlimited bearing life since there are no wearing components. The trade-off is the need for a precision hydraulic pump and oil temperature control.

The ACC-2040DX electromagnetic chuck holds plates up to 500 x 1,000 mm (20 x 40 in). With the table traverse, the machine can grind plates slightly larger than the chuck using step-over grinding (multiple grinding passes with chuck repositioning). Practically, plates up to 500 x 1,050 mm fit within the table traverse. Maximum workpiece height is 350 mm from the chuck surface to the underside of the wheel guard — verify with Okamoto applications engineering for tall workpieces. Workpiece weight limit is 300 kg (661 lb) on the electromagnetic chuck.

Automatic dressing uses a single-point diamond (SID) mounted on a programmable arm to true and dress the grinding wheel at specified intervals without operator intervention. When the Okamoto E-60 CNC determines dressing is needed (based on programmed interval or wheel wear compensation), it automatically positions the diamond across the wheel face at the programmed depth of dress and traverse speed, removing a thin layer of abrasive to expose fresh, sharp grinding grit. Automatic dressing maintains consistent wheel geometry and surface finish throughout the grinding cycle — a key advantage for unattended and lights-out surface grinding.

The 500 x 1,000 mm electromagnetic chuck holds ferromagnetic workpieces: carbon steel, alloy steel, tool steel, and cast iron. The chuck cannot hold non-magnetic materials (aluminum, stainless steel, titanium, carbide). For non-magnetic materials, mechanical fixturing (ground fixture plates, tooling blocks, or sine vises) is bolted to the electromagnetic chuck surface. Magnetic chuck holding force for 500 x 1,000 mm chucks is typically 3–5 N/cm² across the chuck surface — adequate for most flat plate grinding. For thin plates that may bow under magnetic force, check flatness specifications with Okamoto applications engineering.

The Okamoto E-60 is Okamoto's proprietary CNC control running on a Windows platform with Okamoto's own grinding-specific HMI. It programs grinding cycles using Okamoto's graphical conversational programming — the operator enters workpiece dimensions, number of passes, depth of cut, cross feed, dressing conditions, and the machine calculates all axis motions. External G-code programming (CAM post-processor output) is not the primary interface. For shops that prefer G-code programming, Okamoto can typically provide information on their G-code input capability. Training on the E-60's conversational programming takes 1–2 days for experienced CNC operators.