[yorkshire grey]

I HAVE A POSSIBLE DRIVE UNIT FAULT, I HAVE BEEN TOLD THAT IT IS A REGENERATION FAULT, THE PROBLEM IS AT S2500 IT RUNS OK BUT AT S3500 IT MAKES A CHATTERING NOISE THEN IT TRIPPING A 70A BREAKER
ITS A OKUMA CROWN OSP 700L
CAN ANYONE HELP

[CNCZILLA]

Hello. I can tell you this is not a regenerative fault. That only will come into play when stopping the spindle. If you are developing noises at high rpms then this could be several things, some you simply may not be able to determine without going into the spindle and even then not be able to put you finger on anything. First look at the simple things that you can check. Look at the spindle loads when running at 2500 and at 3500. There should not be much load difference at all, maybe a few % between the two. If you notice a high load then you can stop there. REBUILD. Your load shouldnt be more than 6 or 8% on average at 3500. You can check the heat as well for the front and rear bearings. If you dont have 2 thermocouples Then you would have to remove the chuck so you can get a temp gun to read the inside bore of the spindle while running. You wont be able to check the rear bearing without removing the actuator. If you can get some thermocouples there are 2 holes in the top of the headstock casting right over the front and rear bearing. Fill these holes with a light oil like 3 in 1 oil and the place your thermocouple probes down into the holes. Start the spindle at 3500 and monitor the heat. The front bearing should not reach more than 145* and the rear should be around 130* or so. These temps can very from machine to machine depending on who built the spindle and fitted the bearings. These temps are guidelines. If you are getting temps 150* or higher stop the spindle. REBUILD. If these tests dont reveal anything and they may not then you can look for anything in the chucking, in the actuator, pulley's, belts, or anything attatched to the spindle that can transfer this noise. By the way, How do the parts look. Are you getting any finish or size issues. You can also check the runout and end play of the spindle. Of course you want this as tight as possible but anything .004mm or less and you are probably OK there. Spindles can be tricky to diagnose sometimes. It still could be electrical, thats not impossible but not likely. Let me know if i can do anything and good luck. I have rebuilt several Okuma spindles and am factory trained.