MHI Develops "LH250": Double Column Machining Center
Enabling High-precision Machining with 5 micro meter Level Accuracy For Long, Difficult-to-cut Plate Materials and Die Molds Up to 2 Meters

The LH250 was developed applying the concept behind the company's micro milling machine - the "µV1" (micro V1) - to large-size workpiece machining. MHI has been marketing the µV1 since 2006 for direct milling of high-precision dies and molds and machining of electrodes and precision parts. The LH250 has a 2,500 millimeter (mm) long and 1,000 mm wide table with loading capacity up to 3,000 kilogram (kg).

In the LH250, MHI employed a special sliding surface structure that has significant vibration absorption capability. The new machine also employs an inner spindle and external housing cooling system for the main spindle head which has been proved in application to precision milling machines, plus a special jet lubrication system for bearings that is highly reliable and superior in cooling efficiency. Together these devices suppress thermal displacement caused by high-speed operation of the spindle, realize high rigidity in spindle rotation by optimizing the bearing preload throughout the low- to high-speed rotation range, and provide stable machining accuracy even through long hours of operation.

For the main spindle head, the HSK-A63* is adopted. By employing the wide-range type motor capable of producing large torque through the entire spindle speed range from 200 through 20,000 revolutions per minute (rpm), the LH250 can cope with a variety of machining conditions for diverse workpiece materials. By adding extra axis table as an optional equipment, the machine becomes capable of 4- and 5-axis machining. For machining of workpieces of extraordinary height, a 250 mm higher column model is also available. For convenience in carry-in and installation at the enduser's site, the length of the machine is kept to 3,300 mm.

MHI's machine tools are widely used at company factories and at partner companies for various machining needs, a situation that enables MHI to incorporate the detailed requirements of machining shops into new product development. The company developed the LH250 in full consideration of opinions voiced by its workshops involved in various business fields, including aerospace, power generation systems, and mass- and medium-lot manufacturing products. The new machine also integrates elemental technologies accumulated from MHI's operations in large-size double column machining centers and small-size high-precision milling machines.

MHI will introduce the LH250 at Intermold 2012 (Die and Mold Asia 2012), to take place at Intex Osaka from April 18 through 21. With the addition of the new machine, MHI intends to gain momentum in expanding its customer base by steadily probing market demand for precision milling machines able to accommodate long and medium-size workpieces – a niche that has been difficult to fill with earlier machines.