First 5-axis horizontal machining centre from OKK

Designated HM-X6000, the twin-pallet-change machine accommodates components up to 750 mm diameter by 700 mm high and weighing a maximum of 650 kg. It competes at the top end of the market in terms of accuracy and productivity and is the first 5-axis horizontal machining centre to be produced by OKK. Until now, the company has concentrated on 5-axis, vertical-spindle models and 4-axis horizontals.

The Japanese machine builder chose a tilting trunnion / rotary table design rather than incorporating the rotary axes in the spindle head. In many 5-axis machines, while the linear axes may be fast and strong, the rotary axes tend to be the weak links in terms of speed and rigidity.

This is not the case with the HM-X6000, which uses double-disc clamping of the hydraulically counterbalanced, -110 / +20 degree swivelling trunnion (A-axis), generating a holding force of 10,000 Newtons (N). A similar system on the 360-degree rotary table (C-axis) provides 6,800 N clamping force. As the pallet surface is 100 mm below the A-axis centre of rotation, the component sits more or less on the centreline, allowing maximum cutting force to be applied. Accuracy figures for positioning in A and C are an impressive ±5 and ±3 arc-seconds respectively.

Rigidity of construction is enhanced by four-collet clamping of the pallet to the table with a force of 96,000 N. Both mechanical and hydraulic methods are used and the clamping pressure is maintained even if the power supply is interrupted.

OKK has designed considerable speed into the machine to deliver high productivity. Rapid traverse of 54 m/min and 10 m/min cutting feed rate in all three linear axes minimise machine idle time.

So too does the 2-second exchange of a BT50 tool from the 40-station magazine (optionally up to 236 stations) to the 12,000 rpm, 30 kW, BIG Plus face-and-taper-contact spindle. A spindle bearing bore diameter of 100 mm indicates the robustness of machine build, as does the 20-tonnes installed weight.

Slideways are supported on high load, cross roller guides mounted onto the heavily ribbed, one-piece bed. All castings are produced in OKK’s own foundry for consistency of quality.

Steeply inclined slideway covers discourage swarf from accumulating in the working area and two coil-type chip conveyors, one either side of the table, efficiently remove the chips from the machine.

Core chilled ballscrews and the manufacturer’s proprietary Soft Scale II software in the Fanuc F310is-A5 control are employed for dynamic thermal stability.