I recently purchased a G0678 that is almost new. PO bought and kept in his garage for about a year before selling it to me. Most of the machine still had the cosmoline coating on it when I got it home. After cleaning it up, everything seems to work well, but the spindle is noisy. This machine has a 3ph motor with VFD and a single belt to the spindle.
Running the motor without the belt installed is silent until it gets up to the max speed when I think there is a vibration caused by imbalance in the fan. Turning the spindle by hand feels silky smooth. With the belt installed, there seems to be more vibration/noise than there should be. Running the spindle with the cover open revealed a lot of movement in the belt and I can visually see the motor pulley wobble. The indicator shows .020-.030" of run out in the motor pulley with the shaft running dead true. Thinking I had located the issue, I turned a close fitting mandrel tonight so that I could true up the pulley. To my surprise, the pulley ran true on the mandrel. More inspection revealed that the motor shaft is .748" and the bore of the pulley is .756". With the key installed and set screw tightened, the clearance gives the pulley a major wobble. I *think* this wobble is causing the vibration in the belt that is leading to the noise I'm hearing.
I'm looking for options, ideas, opinions on how to proceed.
Running the motor without the belt installed is silent until it gets up to the max speed when I think there is a vibration caused by imbalance in the fan. Turning the spindle by hand feels silky smooth. With the belt installed, there seems to be more vibration/noise than there should be. Running the spindle with the cover open revealed a lot of movement in the belt and I can visually see the motor pulley wobble. The indicator shows .020-.030" of run out in the motor pulley with the shaft running dead true. Thinking I had located the issue, I turned a close fitting mandrel tonight so that I could true up the pulley. To my surprise, the pulley ran true on the mandrel. More inspection revealed that the motor shaft is .748" and the bore of the pulley is .756". With the key installed and set screw tightened, the clearance gives the pulley a major wobble. I *think* this wobble is causing the vibration in the belt that is leading to the noise I'm hearing.
I'm looking for options, ideas, opinions on how to proceed.
- Leave the pulley alone and look elsewhere for the cause of the noise.
- Machine or buy a new pulley.
- Somehow true up the existing pulley as installed.