Re: [CAD_CAM_EDM_DRO] Re: Easing Into CNC -- Ball Screws?

Thanks for the words, Hugh. I'm really hoping to get a lot of input from the
group here since when I was doing this for "big companies" money was much
less of an issue whereas for myself, I want to keep cash outlay to a minimum
for now. Although the concepts are the same in machine tool CNC (especially
home CNC), the stuff I was doing was much different so advice from folks who
have done conversions already is priceless. I think one of the things that
got me really turned on to the idea of home CNC was reading about
LinuxCNC/EMC.

Thanks, all, for the cool group!

Paul R. Hvidston, N6MGN
ACKSYS Engineering
Upland, CA

----- Original Message -----
From: <currinh@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Monday, November 12, 2001 4:23 PM
Subject: [CAD_CAM_EDM_DRO] Re: Easing Into CNC -- Ball Screws?


> Paul:
>
> I don't know why I'm attempting to answer this. From you background I'm
> convinced you have a better handle on the situtation than I. But it's a
> rainy day. :-)
>
> I moved to ball screws right off for a couple of reasons. My acme lead
> screws were worn and beat-up. I adjusted them and got 3 or 4 thousands
> backlash but I'm convinced they would wear quickly and soon be worse
> than this. The other reason was to avoid building bearing plates twice.
> I was afraid there would be variations between my existing acmes and any
> retrofit lead screws. If they did differ I'd have to modify or re-build
> my bearing/motor mounts for the new dimensions. So, I purchased a
> retrofit kit from Rockford and built my new bearing block/motor mounts
> to these.
>
> If you build motor mounts, etc for your existing acme lead screws you
> may well have to re-build or modify them when you move to ball screws.
>
> Other than this I suspect acmes will work OK. You mention back-lash and
> the possibility of "slaming" through this backlash due to climb cutting
> or similar are the problems. Also the acmes will give more friction than
> ball screws as you say. You can calculate an estimate of added torque
> due to this friction. But without doing this, I'd suspect you could size
> the motors for ball screws and only lose some speed if used with acmes.
> If you use a timing belt drive you could certainly trade torque for
> speed by changing out the sprockets.
>
> I'd suggest you consider driver kits or purchased drivers rather than
> design and build your own. I purchased stepper driver kits from
> Camtronics and have been very pleased. Even if I could have designed
> these the time I would have saved would be significant and the cost
> savings minimal. Unless you just want to tackle this design. :-)
>
> As you say, just load up linux and EMC. I did this, but it took a month
> or so of hard work. But you probably have more linux experience than I,
> most do. :-) I do like EMC.
>
> Hope this is of help.
>
> Hugh Currin
> Klamath Falls, OR