Re: [CAD_CAM_EDM_DRO] Bridgeport Spindle Questions

Peter Renolds wrote:

>Hi all,
>
>I've been happily cutting (lots of) chips with my CNC'd BP clone with
>the variable speed head and now am noticing a strange smell,
>particularly during heavy cuts and a lot more rattly spindle (internal)
>noise most of the time. I don't think it is a bearing problem because I
>measured the runout and it is still negligible according to my .0005"
>dial gauge and cutting quality is still excellent. I visually checked
>the big belt and it looks ok but I now have about 800 -1000 hours on the
>unit (bought new) and was wondering what is the typical belt life? FYI,
>the motor is run from a VFD at 75 Hz and the spindle actually runs at
>about 4500 rpm and I adjust my feed rates to get best cutting results.
>Also, every day I wind the vari-speed dial to low and allow things to
>warm up before going up to the higher speed.
>
>As I have CNC'd the knee, I have the quill locked 99% of the time. I
>have never used any of the quill auto feed levers or back gears. Has
>anyone experimented with removing some of the parts behind the various
>lever/access panels to reduce the number of moving parts and hence
>reduce the spindle noise level?
>
>

The power feed gears only move if the feed worm (little crank on the
front right side of the head) is engaged. The back gear mechanism is
always turning, even if not engaged. If you never use it, take the
toothed belt out. You can isolate the rattles by engaging and disengaging
various clutches. For instance, the vari-speed has a high-N-low clutch.
Put it in N, and the only thing turning is the varispeed mechanism. If
you still have the rattle, it must be in the motor, driven pulley bearings
or the variable cones, or the back gear. There is a plastic bushing in the
motor pulley hub, I think, that often causes problems. If it is quiet
in this
mode, then it must be in the spindle itself or the direct drive clutch. If
it rattles in high but not low, that really points to the direct drive
clutch,
that is on top of the spindle in the driven pulley. If it only rattles
under load,
that is due to looseness in the splines of the spindle. You can put a
bit of
heavy grease on the splines to quiet them.

Jon