Okuma OSP5020L Backlash compensation

[Rocksalt]

I've got a 5020L okuma that I want to set the backlash on. When I change the parameter to the value I need, a power cycle alarm is indicated. When powering down the machine and re-applying power the old value is displayed. The book tells me that I have to power down the machine when the BC counter displays the same value as the new value I changed to. This is somewhat confusing. The BC counter changes values with 2 digits. 01, 02...0A..0F, 11..1F, etc.. If I want a compensation of .0010 then what BC counter number am I looking for? I managed to try and set the number to .0011 when the BC counter was at 11. When I re-applied power the number changed to .0000 for the backlash compensation.

[Jarwalcot]

Jack,

Note what the BC counter is showing at the same time you are changing the Backlash setting. Once that same number appears again, it will be safe to shutdown the control and restart it. Your new value should be there once you power back up. I don't know how old of a 5020 control your working with but if you hit the F8 key do you see a "F Key" with the words Back up there? If so, just hit that and then power down.

Let me know how it turns out,

[Rocksalt]

I re-read the instructions and came up with exactly as you described. I was trying to hit the 'write' key and then immediatly powering down while the BC counter stayed the same. This works with mixed results. I still can't figure out why the value went to .0000 when I set it to .0015! I waited until the BC counter went to 15(I didn't note the BC # when 'write' was pressed). Anyway, I did it this morning and waited for the BC counter to reach the 'write' value and it worked.

I did try and hit the F8 and look for another F-option without any success.

It seems that I have another problem I need to look into... Upon checking the loss of motion, with an indicator, I noticed the NC was moving the axis .0023 to far in the opposite direction. The backlash compensation was set to .0023. At this point I was thinking "great"- no backlash. "I'll just set it to .0000 and all will be well".... I set to .0000, get indicator, check, good. Then someone asks me what I was doing, so I re-connect the indicator. Now it shows a loss of motion of .001.

For someone to se the backlash compensation to .0023 means that at some point a tech saw .0023 backlash. At least that is what I hope they saw... I think it must be a bearing problem.

The reason I decided to check the machine was due to a high frequency oscillation when a long boring bar was used. The machine would start vibrating, even with 'feed hold' applied. I think the NC was trying to move the axis into position and the backlash compensation was to high, causing the axis to overshoot position, putting the machine in a constant hunting situation. I am only guessing at this point on this hypothosis. I don't feel it's an encoder, but it could very well be. The machine is repeating well as well as picking up lead on threading.

The variance in loss of motion is perplexing though. Sounds like I will be in for a teardown in the future.

[Jarwalcot]

Rock,

Here is the file I mentioned in the private message. I'm confident that you will find it helpful.