[miladokuma]

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

[fordav11]

that doesn't sound right. that would be like saying your car has a flat tire then pulling the motor out to fix the tire problem

abnormal noise is caused by mechanical interference or damaged mechanical parts.

The VAC Unit is a fully electronic device that controls the spindle. if the VAC Unit has any fault you would be seeing alarms on your screen. Since you see no alarms the VAC Unit must be ok.

I suggest you check the gearbox first then mechanical spindle components.

[miladokuma]

dear sir!!! I were opend the gear box but I can't found any mechanical problem any fult in bearing or gears. if that was a mechanical problem it must be from starting cnc to work to the end of working. but as i said the sound can't hear at first starting to work but over the cnc working the sound increasing. and I enclosed this problem with my friend and he said for me the problems must be in this items:

Checking items:

* Check the voltage supply going to motor standard voltage must be [175~250 V] only.

* If they have a big voltage send to the amplifier can create a vibration that can cause abnormal noise w/c what u have encountering right now.

* Please check your "frequency inverter " may be theres a problem on power module, sometimes the problem is "power transistor" voltage.

* Please check the vac " 3 Phase wire " going to motor [ 175 ~ 250 V ] only.

* Please check the insolator of motor, if only 10 M ohms "below" ( no good ), the standard must be 10 M ohms " ~ " (good condition ).

but as i hadn't any electrical manual's i can't chek this items.

[fordav11]

I still doubt its electrical or power related. but ok.
almost all of your checks are motor related. you can easily check power going to the motor without a diagram. locate the motor, locate wires connected to motor and check the terminals where they are wired in to see if incoming power is within the range you listed.

[miladokuma]

dear sir!!! I were opend the gear box but I can't found any mechanical problem any fult in bearing or gears. if that was a mechanical problem it must be from starting cnc to work to the end of working. but as i said the sound can't hear at first starting to work but over the cnc working the sound increasing. and I enclosed this problem with my friend and he said for me the problems must be in this items:

Checking items:

* Check the voltage supply going to motor standard voltage must be [175~250 V] only.

* If they have a big voltage send to the amplifier can create a vibration that can cause abnormal noise w/c what u have encountering right now.

* Please check your "frequency inverter " may be theres a problem on power module, sometimes the problem is "power transistor" voltage.

* Please check the vac " 3 Phase wire " going to motor [ 175 ~ 250 V ] only.

* Please check the insolator of motor, if only 10 M ohms "below" ( no good ), the standard must be 10 M ohms " ~ " (good condition ).

but as i hadn't any electrical manual's i can't chek this items.

[miladokuma]

dear sir; I was recorded the cnc working video if it possible i want to send it for you maybe you can help for me to solve this problem.