Hello everyone i've been visitng the cnc zone for some time, and must say lot of neat stuff, I've been doing a lot of reading and internet searching. I am on the verge of building my first cnc router small scale and I am excited, my question is I don't really understand the difference between stepper motors and or much on the linear guides do i have to use linear guides? I had planned on using half inch rod or thicker and use a set of pullies to rest on the rod and travel while the stepper and screw do its job.Could anyone tell me if this might work. Also I did read the book form Geoff Williams on cnc robotics can anyone elaborate on it. Thank you David :)

Try these two link for stepper and Welcome to the site
http://www.geckodrive.com/photos/Step_motor_basics.pdf
http://www.pminmo.com/drivers.htm

any system you use to move a device in a linear axis is probably a linear guide, in our case..

so, pulleys on half inch rod could work.. but i think you would get much better results trying the rollerblade bearings on 'black pipe'. I beleive 1/2" chrome rod is fairly flimsy. if your axis are to be more than 12" long each total(not just travel)... or your gantry weighs alot, 1/2" rod will be a bad choice i think..

1" or 1.5" water pipe, on the other hand, is probably good upto 48", althought the longer your axis, the less accurate it will be.. error is accumilative. it will be much easier to build an accurate small machine... and cheaper..

there is almost an endless series of caveats and if 'thens' to point out. i suggest looking at the forums... everyne who uses this place alot probably sighs everything someone asks something they have seen covered repeatedly in the forums.. their advice to you would be...

1. read alot first.
2. set realistic goals. budget and performance wise
3. consider building a 'practice machine' first.. i did this.. it was very educational and fun. it even looked really good.. it just didnt work well at all.. too weak.. wood, and not nearly enough of it.. really flimsey...
4. look at the build logs poted by others.. choose one in your price range, copy it... ask the builder questions..
5. make lists, sketches, illustrations, diagrams, calculations, and devlopment plans.. i do this. it is more fun, possibly, than drilling 100+/- accurate holes with a drill press to hold whatever together...

hope it helps!

Thank you all for the help I'm constantly reading and searching for all the help I can get, and must say I'm having fun just doing that. :)

David,

The major difference between steppers and servos is steppers "know" their position due to feedback loops. Servos do not. So with servos the software which drives them assumes their position. To test this lock down one of the axis (not really recommended) a stepper will increase power until it hits a break down point and faults out. In a servo system the machine will simply continue in place until it has to move in one of the other axis'.

lol I know someone will cough at this siteing encoders etc but encoders have no fixed starting point as in a stepper system.

David,

The major difference between steppers and servos is steppers "know" their position due to feedback loops. Servos do not. So with servos the software which drives them assumes their position. To test this lock down one of the axis (not really recommended) a stepper will increase power until it hits a break down point and faults out. In a servo system the machine will simply continue in place until it has to move in one of the other axis'.

lol I know someone will cough at this siteing encoders etc but encoders have no fixed starting point as in a stepper system.My steppers dont have a clue where they are....they just assume they know. afaik the only way to use a servo is to have a feedback system ie encoders resolvers or some such...unless you were confused in your original post :shrug:....