Re: [CAD_CAM_EDM_DRO] CNC router/mill controls

For that kind of money, you're a lot better off with bipolar motors and
some other driver, such as Geckos. Bipolar motors with chopper drivers
(Geckos, L297/L298, etc.) give a lot better performance than unipolar
motors.

The Gecko's microstepping helps performance and mid-band resonance.
Read up at the http://www.geckodrives.com website.

Screw pitch, motor size, and machine size are all interrelated with
speed and resolution. Read all you can find, see what other people use,
and jump in.

You definitely want to use acme screws or ball screws (if you intend to
use screws to drive the axes). Hardware store threaded rod is /very/
inefficient. Normal threads are designed to wedge under stress,
otherwise everything would fall apart :-). Acme threads, being square,
are much less susceptible to wedging. Ball screws are the ultimate, and
don't wedge. Have a look at McMaster Carr for cheap ball screws, and
mscdirect.com for cheap acme components.

The axes do not have to have the same pitch screws to do contouring.
The software handles that. I prefer TurboCNC, it's DOS based, and
available here: www.dakeng.com.

Keep an eye out on eBay for THK linear slides, and Thomson linear
bearings and roundways. It will simplify your machine, and your life.
Of course you can buy them new too, just get a second on your house :-)

Figure out what you intend to use for a spindle too, /before/ you build
the machine.

Regards,
JJ

On Saturday, December 13, 2003, at 10:23 PM, Gregory Kamysz wrote:

> I'm new here. I have recently started researching building a CNC
> router
> and converting mills to CNC. If any of the questions can be readily
> answered with a link please direct me.
>
> I'm going to assemble a router to learn how the things work and to gain
> experience with the required equipment and software. I've been looking
> around and have seen some products which are commonly used by CNC at
> home people. I have a few questions.
>
> I'm considering the Stepperworld FET-3 controller. To use with 3
> PK266-03 steppers. This unit is affordable and seems to be good enough
> for routing. It does halfstepping and I'm wondering if there is much
> to
> be gained with 10x microstepping of the Gecko drives. Stepperworld
> does
> not list all the specs like max stepping frequency and a few others
> listed by Gecko etc.
>
> How is the accuracy and size of the machine defined by the controller
> board and lead screws? It seems that the machine has certain size and
> speed limits based on the controller's limitations. Stepping frequency
> and screw pitch define speed to some extent. How many steps per inch
> before you're just reducing speed and not gaining accuracy? I've read
> that if you want to do circular interpolation you need to use the same
> screw pitch on X and Y axis. Is this a software or
> hardware(controller)
> limitation? Is this also true for the Z if you intend to do 3D
> contouring.
>
> Software seems to vary from freeware to industrial standard at 1000's
> of
> dollars per license. Is there a site that weighs the pros and cons of
> several types of software? Are there compatibility issues with
> controllers and software? I guess that the software to operate the
> machine can be run from DOS, Linux, or Windows. Most of the Gcode
> generators would be Windows based? I'll be designing parts in
> SolidWorks.
>
> My plan is to make a relatively accurate router, then find a larger
> tabletop mill to convert for cutting aluminum. I'd go ahead and buy a
> Sherline or similar to start with but the Y travel is not enough for
> what I want to do.
>
> Thanks for the help. Some of you may recognize me from RCGroups.
>
> Gregory Kamysz
> Crystal Lake, IL
> USA
>
>
>
> 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@...,
> timg@...
> Moderator: pentam@... indigo_red@... [Moderators]
> URL to this group: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO
>
> OFF Topic POSTS: General Machining
> If you wish to post on unlimited OT subjects goto:
> aol://5863:126/rec.crafts.metalworking or go thru Google.com to reach
> it if you have trouble.
> http://www.metalworking.com/news_servers.html
>
> http://groups.yahoo.com/group/jobshophomeshop I consider this to be
> a sister site to the CCED group, as many of the same members are
> there, for OT subjects, that are not allowed on the CCED list.
>
> NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY POSTING
> THEM. DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........
> bill
> List Mom
> List Owner
>
>
>
> Your use of Yahoo! Groups is subject to
> http://docs.yahoo.com/info/terms/
>
>