HI everybody:

I have a okuma LB15 cnc lathe 1991. when i starting to work with this machine at first about 5-6houers the lower gear sounds can hear form gearbox it's like that the gears collision together(gears abnormal noise). after this time the sounds raising.(the sound in lower speeds about 400rpm not hear but when the speed raising up to 1300rpm and uper the sound is very loud). i invited the cnc mechanic to inspected this problem he said the spindle bearings are good the problem is from VAC unit. then i invited electronic engineer and they couldn't solve this problem.I haven't any maintenence or service manual for this machine for solving the problem.the VAC II board number of this machine is (E4809-045-140-1006-1104-72-18)VAC drive unit TYPE A. our prediction is that the problem is from VAC unit if you Please lead me solve this problem.

thanks and regards