Re: [CAD_CAM_EDM_DRO] Bent Nook ballscrews ?????

No guarentees, but you could try the method some folks use to straighten out
bent/bowed rifle barrels. Don't try this at home, (on the dining room table),
but if you've enough space on your shop bench, roll it until the ends come up as
far as they'll go. Then grab it by one end raise it up overhead, and slam it
down, hard, and flat, on the bench. reverse ends, and repeat as needed.

Bill

On Tue Aug 12 06:44:53 2003 Kim Lux wrote:

>Comments below.
>
>On Mon, 2003-08-11 at 22:24, Jon Elson wrote:
>> Kim Lux wrote:
>>
>> >A substantial amount of force would have to be greater than the pushing
>> >capacity of the motor so that there was never a force that would
>> >displace the nuts against each other. If the spring is weaker than the
>> >pushing force of the motor, then it will displace the backlash under a
>> >heavy cut.
>> >
>> >As soon as the nuts are adjusted for the maximum force the motor is
>> >capable of moving, there isn't any force left to move the cutter.
>> >
>> >
>> No, you're confusing drag with linear thrust.
>
>No, I'm pretty sure I'm not. Lets say we have an axis that needs, on
>occasion, 500 lbs of cutting force. In order to ensure that we never
>had backlash, we'd have to put a preload and the backlash nut of 500
>lbs, to keep the backlash zero in the presence of our load. That then
>puts the load on the ballscrew at 1000 lbs, ie 500lbs for the cutting
>load and 500 lbs for the backlash.
>
>> If the system is designed to
>> apply 1000 Lbs of linear thrust, you want somewhat over 1000 Lbs
>> of preload force between the two ballnuts.
>
>Yes. Thus the total load on that ballscrew is 2000 lbs. It takes twice
>the motor to turn the preloaded system.
>
>> On a good ground screw,
>> 1000 Lbs of preload will cause a very mild drag, maybe 10 Oz-In
>> when new, and decreasing as the screw and nuts wear in a little.
>
>Where do you get your information from ? A 3/4" 5 TPI ballscrew has a
>force to torque ratio of about 31 lbs force per in pound of torque.
>1000lbs/31 inlbs/lb = 32ish inlbs of torque or 516 oz in of torque, just
>to turn the backlash preload on the nuts.
>
>> You don't have to adjust the nuts until they bind up. That could be
>> 5000 - 10,000 Lbs of preload, and will quickly destroy the balls.
>
>HUH ?
>
>
>>
>> Jon

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