Re: [CAD_CAM_EDM_DRO]Backlash & Wobbly Spindle on my Bridgeport

not sure of exactly how your ball screws are mounted....but on w occasions I have traced errors down to the nuts on the end of the ballscrew being loose.

Alex Canale wrote:

> Hi Jon, and everybody else who kindly answered!
>
> I did a series of measurements with the dial indicator in the X and Y axis.
> These are the results:
>
> Location: approx. towards center of table
> All movements were done with a feed of 2IPM.
>
> Y-axis
> Screen display Indicator Reading
> .5000 .4950 (.0050)
> .2500 .2445 (.0045)
> .1000 .0960 (.0040)
> .0500 .0460 (.0040)
> .0250 .0205 (.0045)
> .0100 .0060 (.0040)
> .0050 .0010 (.0040)
> .0010 .0000
>
> X-axis
> Screen Display Indicator Display
> .5000 .4985 (.0015)
> .2500 .2490 (.0010)
> .1000 .0990 (.0010)
> .0500 .0490 (.0010)
> .0250 .0235 (.0015)
> .0100 .0090 (.0010)
> .0050 .0035 (.0015)
> .0010 .0000
>
> I went ahead and ran the same test on another part of the table
> Location: Top Right Corner of Table
>
> Y-axis
> Screen Display Indicator Reading
> .5000 .4955 (.0045)
> .2500 .2450 (.0050)
> .1000 .0960 (.0040)
> .0500 .0460 (.0040)
> .0250 .0210 (.0040)
> .0100 .0065 (.0035)
> .0050 .0020 (.0030)
> .0010 .0000
>
> X-axis
> Screen Display Indicator Reading
> .5000 .4995 (.0020)
> .2500 .2480 (.0020)
> .1000 .0980 (.0020)
> .0500 .0480 (.0020)
> .0250 .0230 (.0020)
> .0100 .0080 (.0025)
> .0050 .0030 (.0020)
> .0010 .0000
>
> I'm not very sure if this is a problem of excess table wear because the
> problem does not seam to diminish when the table is moved. Also when ever I
> would bring the table back to x0 y0 the reading on the indicator would be
> "dead nuts" zero! It's almost like the ball screw would shift on it's axis a
> little bit until it would engage the table and start moving it.
>
> I did try to measure the backlash as you described I zeroed out the table in
> "X" and then I moved it an inch with the indicator on one side I measured
> the the difference in the indicator to be .0025" Then I zeroed the table
> again (brought back to the zero position) moved the indicator to the other
> side and displaced the table an inch in the other direction and measured the
> difference to be .0030". Does this mean that the backlash is .0055"? If it
> is WOW!!!!
>
> I haven't done any of the other measurements for the runout on the
> head/spindle. Partly because I don't understand half the stuff that you told
> me (sorry I'm still climbing the ste learning curve)and also because I
> wanted to deal with the table issues first. But Answering your question
> about the tilt head, yes it does have one, and I have indexed it before but
> i suspect it is not quite right yet. I used the top of the vise to index it.
>
> With respect to the gauge blocks......well I think I'm gonna have to ask
> that one again 'cause that was way over my head.
>
> Now back to the table problem. I checked the belt on the y-axis and it seams
> to be ok, other than it needs a little lubrication. There is no noticeable
> slop or play. In another mail, some suggested that the thrust bearing could
> be the culprits or also the screws that secure the ball nuts. How can I
> check for these guys and where can I finde them.
>
> Also is there a service manual for these things, or would that be pretty
> much a fossil.
>
> Thanks, Jon and everybody else that replied, you guys are great help.
>
> Dead in the water, Alex
>
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