Problem- Fanuc 5T Spindle Drive Speed

[Dragoon2]

I have a Howa Sangyo NC11L lathe, I have used it in my home shop a little over the last 2 years, it has it's problems but, I moved it into my machine shop in town so we could use it more easily. Everything went well, we were very carefull not to shock the control cabinet during the move. However, when I run a program or manualy run the spindle, the RPM does not come up to the requested speed. I have checked the parameters 55-62 all are set at the correct value for this lathe. I have the program turning the spindle on with: G97S600M25 the M25 sets the range to 50-600 RPM, I have also tried M26 which set it to 70-2000; the gear shift is working and spindle speed appears to be the same, about 40 RPM. I have tried to set the RPM to S100, it does go slower, about 20 RPM. It runs the same CW or CCW. It runs through a complete program without an alarm, however the spindle never comes close to the correct RPM. I have checked the 3 phase power, it is 246 volts accross all 3 legs all the way through the contactor in the spindle servo unit (A060B 6041 H112) it has a board on the front (A20B-0005-0372/13F) that does not let me get into the unit to check the 3 phase further.

I have just removed the board, cover, and disconected and checked the SCRs with an ohm meter all (12) of them in the Spindle Drive Unit. There are 11 that check open between the big wire and the lower body, but 1 that has resistance. This may be a dumb question but, is this one bad? If so would this cause the problem? And does anyone know where to get one? Part number NEC 80P8S

Does anyone have any suggestions?

Steve Werkema

[Dragoon2]

I found at least part of my problem. I had a control cable going to the spindle drive that was laying parralell to, and touching leads comming out of a transformer just below and to the left of the drive. I figured there was a possibilty of noise or interferance so I moved them about three inches back away from each other. Then tried the spindle out, it worked in the highest gear at least up to 800 rpm (checked ok with a tach) this gear covers 150-1800 rpm, I don't want to turn it faster than about 800 rpm with the large chuck on it. But, in the three lower gears it only works toward the lower end of their ranges. I think the gear shift I/O must be working, as it completes all of the four programmed shifts ok, just will not spin at higher rpms.

[Kevin Taylor]

Check all the cables unplug and plug in seem's to not take much when you move a machine to become a headach Is there a incoder or tack on the spindel that is belt driven for feed back to the control Seem's like any lose wire or board could be the culprit Good Luck Kevin

[WGoyer]

Steve,
One of the most common troubles we have with this vintage board is the two slide switches in the lower part of the board. These choose between digital and analog speed commands on the various machine configurations. I suggest cycling the switches back and forth several times (with the power off). You might even try gently tapping on them during slow commanded speeds to see if they might be sensitive. Note their proper position before moving them! We usually remove the switches and solder jumpers if the switches prove to be sensitive.

Warren
www.uptimecorp.com