Re: [mach1mach2cnc] Re: does that allow for any conclusions?
- You said "> I am not sure how close to zero one can get mechanically"
You can get ZERO backlash with ballscrews. Not a question. I set up my new
installation this week, and checked it using a dial indicator just as others
had described. On my x and y axes, with preloaded ballscrews, I have
absolutely ZERO backlash. Ran it many many times, amazed to see that
pointer return to absolute zero each time it traveled back and forth.
My mill Z axis (existing acme screw with heavy knee) has only 4 thou
backlash, as I was able to press the bevel gear closer for less slop. I am
very happy with the setup. The only thing I want to change is to revise the
fixed preload to a belleville spring (washer) preload to account for future
wear on both screws. Then it wil be darn near perfect.
It sounds like you have a single ballnut installation by the amount of
backlash you are seeing. You might consider reviewing the previous messages
about a month to 6 weeks back related to preloaded screws using 2 identical,
inexpensive ballnuts threaded against one another in a threaded body
attached to the table.
happy camper here...
R. William Kichman, P.E.
Kichman Engineering Associates
103 Old Furnace Road
Cornwall, PA 17016-0643
----- Original Message -----
From: "jocowa2111" <jwagner@...>
Sent: Tuesday, September 30, 2003 12:07 PM
Subject: [mach1mach2cnc] Re: does that allow for any conclusions?
> I took measurements last night.
> On each the y and x axis I I moved "in-line" and in reverse, whereby
> in-line means I traveled in minus direction, then took measurement
> trvelling further in minus direction. Reverse means, I traveled in
> plus direction, the took measurement travelling in minus direction.
> On 4 measurements of each I noted the differnce between the computer
> travel distance and my caliper reading. These were the averages:
> X Inline travel .0012 Reverse travel .0068
> Y Inline travel .0015 Reverse travel .0036
> So it looks to me that I have backlash of about .0056 on X and .0021
> on Y
> I am not sure how close to zero one can get mechanically. My
> machine has 5/8" dia ball screws with 5tpi. The Y axis has double
> ball nuts, the x axis only a single. My sense is that for the X
> axis at least the most play is right in the ball nut, not in the
> shaft bearings. Any idea whether one can adjust thsoe ball nuts for
> less play?
> --- In firstname.lastname@example.org, "Robert Hansberger"
> <rhansberger@c...> wrote:
> > Perhaps, But until you take actual measurements you don't really
> > If it does have some B/L it can be entered into the software.
> > I don't mean to be a hard a--, but I do believe in following the
> > basic procedure step by step. Never any question that way.
> > Be well
> > Bob
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