Doosan is showcasing its new DNM 750L this week at IMTS. It features the power to cut deep into tough materials, the rigidity to hold tight specs, and the size to produce precise parts within its 85.0” x 30.0”, x 25.6” machining envelope. Its heavily ribbed, one-piece bed resists deformation often caused by heavy cuts. A fine-grain Meehanite casting helps dissipate heat and dampen vibration. Large, four row, roller-type linear guideways enable high speed movement along the machines’ three axes, while preserving the rigidity needed for +/-0.0002” full-stroke positioning and +/- 0.00008” repeatability. The 85.0” x 29.9” table supports a hefty 3,970 lbs.
The machine’s 8,000 rpm (12,000 rpm optional) 40-taper spindle is supported by four permanently lubricated bearings. The bearings are ceramic to prevent thermal growth. A 25 Hp AC motor transmits power through cogged belts to eliminate slippage, promote thermal stability, and minimize vibration. Feeding the spindle is a 30-pot, ATC with a random-access, double–arm tool changer. Tools are secured with a dual-contact Big Plus tooling system, and achieves a quick 1.3 second tool-to-tool change time. With an attached encoder, rigid tapping is standard.
Each axis is driven by a high precision, double-nut ball screw. The ball screws are positioned between the guideways, and supported at both ends by angular contact thrust bearings. The ball screws are attached directly to the servo drive motor. This design eliminates gears and belts, assuring maximum power while eliminating backlash.
A dedicated 230 psi positive displacement pump delivers coolant directly to the tool tip. This allows the DNM 750L to maintain more aggressive speeds and feeds throughout the cutting process, and eliminates the need for stopping to clear the coolant nozzles. A 126 gallon tank provides an ample supply of coolant, and is isolated to prevent heat transfer.