Re: [CAD_CAM_EDM_DRO] ball screw or belt drive?

Jan, Jan, Jan, (Some "in here" may-well disagree)

Are you talking about me ?
C'mon, don't scare the fellow off ! He said "small trim router" - "wood" -"wax" -
Maybe, Maybe "Engraving in Aluminum".
Probably not going to do something for NASA right away anyhow.


Zbadone ( ya, gotta name?), Open up your Mcmaster book. Select for yourself a 6
foot long, 1/2" "lead", 1/2" diameter Rolled lead screw and Corresponding
AntiBacklash nut. The screw will be like $120 something and the nut.... under
$30. If you do this right, you only need one stick of screw. You won't break the
bank, (that will come, with this hobby), you will still have enough to take your
honey out to lunch, AND, you will probably make anything and everything you ever
desired on your "First CNC Machine" !!!! If you have the room for it and a few
more bucks, Increase the diameter of the screw.

Now, the nuts mcmaster sells are a little gimpy.... maybe only good for 30 or so
pounds of push. They are under rated though. So what it if wears out in a year
and you spend another 30 bucks. Likely, you will not really ever push that hard
with what you describe wanting to do. Remember.... "build for the application".
If you really need a tougher nut, Call Kerk. They have nuts to fit that same
screw.

I have however, seen those gimpy nuts in service for 2 years, 16h/6d. When we
pulled 'em off the machines we all took them home rather than trashing them as
they were certainly still usable. Come to think of it, we had an old Vektor
Router years back. That bugger had one of those exact nuts on the Y axis. I know
it ran 3 years without anyone looking at it.

Ball Screws are great. But, if your brother inlaw doesn't sell them, they are not
worth it on your machine with what YOU want to do. trust me..............

Don't use a typical gogged belt as the entire drive mechanism though. Unless of
course your application allows for it. Hey, I heard of a fellow who does ICE
Sculpture on a router ! I bet a few thou' here and there does not matter to him
!!

There are some very nice tape drive systems that could work but they will be
pricey too. You CAN use cogged belts to connect the motors to the leadscrews. In
fact, I recommend this if you ever need to make a controller work correctly with
your particular drivers and motors. They're all different. Just look for example
the difference in motor torque curves from company to company. But, if you are a
Rocket Scientist by trade, then you could do all of the math necessary to avoid
belts and pulleys for driving the screws and make it perfect right away. (Even
then I have never seen motion control done that way, It always gets something
modified once it hits the floor and put into operation) - (ah,,ah,,, Really now.
The ONLY stuff that works is when they apply what they have learned in a previous
situation. They just act like they did the math !)

Oh, and this is not a shameless plug. If you are just starting out, have a look
at some of the pictures on my website.
http://www.data-cut.com/
It may give you some ideas as to how you can build your machine. Be sure to tell
us where we can see photos of your progress. Ain't this stuff great ??

Oh. If you do use a ball screw on your Z axis....... Don't put anything good
under it when you dump your power ! (unless you have followed all of the proper
safety guidelines and included a "braking system" of some sort, then again if you
use a 1100oz step motor on that bugger she just might stay up.)

Don't get me wrong, Ballscrews, Servo's and 15K controls are great! There just
not always in the category of a "First Machine". Build what you can afford.
You'll have a bunch of fun.

hope this helps,

Chris Luebke
DATA-CUT


JanRwl@... wrote:

> zbadone: You have a NAME?
>
> Some "in here" may-well disagree, but I don't see the point in trying to do
> "precison" work with computer-control if the MACHINE will introduce slop and
> backlash far in excess of "everyday capability". Chains won't cut it, unless
> you will be making just those notches in the ends of logs for log-cabin kits,
> etc.!
>
> Think BALL-SCREWS! For the smallish WW machine you describe, ACME with
> Turcite preloaded nuts might do, if you use at least #23 bipolar steppers, or
> #34. But I'd go with 3/4" dia. ball-screws with at least 0.2"/turn pitch, if
> not 0.5"/turn!
>
> You do NOT have to use clean-room-ground screws! Rolled ball-screws will do.
> See Ball Screws & Actuators (company) in San Jose, CA. (sorry, no further
> address).
>
> Lotsa luck. Jan Rowland, Troll
>
> Addresses:
> FAQ: http://www.ktmarketing.com/faq.html
> FILES: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/files/
>
> Post messages: CAD_CAM_EDM_DRO@yahoogroups.com
> Subscribe: CAD_CAM_EDM_DRO-subscribe@yahoogroups.com
> Unsubscribe: CAD_CAM_EDM_DRO-unsubscribe@yahoogroups.com
> List owner: CAD_CAM_EDM_DRO-owner@yahoogroups.com, wanliker@...
> Moderator: jmelson@... timg@... [Moderator]
> URL to this page: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO
> bill,
> List Manager
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/