[~TM~]

Ok I'm gathering materials to construct a 3' x 4' cnc out of mostly 80/20 and linear slides. Therefor i hope to achieve 200ish inches/min cutting rates...maybe. Here is what i was thinking about for the axis-
KELING steppers
-nema 34 640oz (x and y axis) rated at 6A 2.4V bipolar
-nema 23 495oz (z axis) 3A 3.6V bipolar
I've read i should run these in parallel for best results right?
-Gecko 203 drivers (by what I've read they are semi-dummy proof...perfect for the electrically challenged=ME)

Ok that's what i definitely want, now what do you guys suggest for a good power supply? 36V 48V Keling? And what about a BOB? Will I need one? What would make a great friend to the geckos? Will all these components work well together? I'm just looking for experience on good combos.
And can someone double check me here on my linear path. I apologize if this sounds redundant, but before cash is thrown I want to make sure I understand.
CAD(autocad)-CAM(?)-Mach3 (this is what i'll use) - printer port-breakout board-gecko drives-steppers--voila finished artwork
Thanks for any input, I'm definitely new to this. I know how to use autocad, have ran a cnc, and am a woodworker..dangerous combo for this hobby. Thanks again
~tommy

[Eurisko]

Hi Tommy,

Sounds like you've made some good choices.

As for the power supply, the more voltage, the better. Gecko recommends 4x to 20x the motor's rated voltage, up to a max of 80 volts. An unregulated supply is fine.

You'll have to decide how you want to drive your router.
Precision ground ballscrews are the best, but out of my price range.
Rolled ballscrews are more economical, but generally less accurate.
Precision acme rods would also be a fair choice, depending on your budget.

Let's have a look at your drawings, always nice to see a new build.

[ahren]

Sounds like you are on the right track from an electronics standpoint. The voltage of the power supplies is not crucial, but the higher the voltage, the less your torque will fall off due to back emf at higher speeds. I would say the 48V will do well. Geckos are great, and should work well with the Keling motors.

What are you planning from a mechanical standpoint? How are you going to drive your axes, and what are you planning on using for linear slides?

Ahren
www.cncrouterparts.com

[~TM~]

Thanks for the encouragement guys. Have you heard much about this BOB from CNC4PC - C11G board and I guess it needs a separate power supply? And i guess i might go with a 48volt supply from keling KL-350-48 48V/7.3A
110V/230V for the drivers.

Eurisko- i'm thinking about precision acme rods 1/2 - 10 5start help me out...this means 1/2 diameter, 10 threads per inch, 5 separate running threads right? I think Joe used this setup on his new 4x4 hybrid and it seems like that should work for speed and accuracy. As far as drawings, i should have something very generic drawn up this weekend to show off and have you guys pick apart.
Ahren- tomorrow i'll take some pics of the linear slides i have, hopefully it'll give you a better understanding of what i'm thinking. I'll try to explain right now...i have THK 16mm bushings and shafts for the z-axis. For the y-axis (gantry axis) i have 30mm THK open bearings that will ride on hardened steel shafts (real nice and beefy) and for the x-axis i'm in the process of buying some THK sr25 linear dovetail rails and blocks : ) i'm using the z and x axis choices because i received them for free...but i gotta shell some out for those dovetails but hey, i wanna make something that lasts.
I will mostly be cutting wood and some plexi, etc with this router but i want to have the beef there to do even a little aluminum maybe. For now i'll use my Porta cable router as a spindle so nothing too crazy.
Like i said by the end of this weekend i should have a drawing and some pics posted of the slides i have. Stay tuned in for the beginning...

[ger21]

I'd get at least a 10 amp supply. 7.3 might not be enough if all 3 motors are running at full power.

[~TM~]

ger21- do you have a source for a 10amp power supply? Most of the 48v supplies i've found seem to peak at around 8amps. What is an unregulated power supply? Those will definitely work but they are twice as expensive. Ok so i took some pics of the slides i have.

-pic 1- 30mm open block slide and 48" 30mm hardened shaft
-pic 2- same
-pic 3- 16mm bushing and 15" shaft with tapped ends
-pic 4- same

As far as the leadscrews, what do you guys suggest? I was thinking 1/2" 10 5 start like i said, but am also considering roton ballscrews? Suggestions? Like everyone i'm trying to stay as low as possible on the price but with good results. Well gotta start drawing this thing up now, thanks for any comments.

[ger21]

http://cgi.ebay.com/50V-10A-Power-Su...QQcmdZViewItem

http://cgi.ebay.com/54V-12A-5V-12V-R...QQcmdZViewItem

[Eurisko]

I'd get at least a 10 amp supply. 7.3 might not be enough if all 3 motors are running at full power.

Gerry is absolutely right.

A parallel connected stepper will draw 2/3 of its rated current. So, a 6 amp motor will draw 4 amps, and a 3 amp motor will draw 2 amps. This info is from Gecko's Step Motor Basics.

In answer to your question,

A regulated power supply maintains a (nearly) constant output voltage, even with varying load conditions. This is a must if you're dealing with digital circuitry, but not necessary for driving a stepper motor.

An unregulated power supply usually consists of a transformer, bridge rectifier, and filter capacitors. There will always be a slight voltage ripple at the output. Use larger capacitors for less ripple.

[~TM~]

That makes sense, thanks for clarifying eurisko. The links ger21 gave are a good start on where i might get one, prices aren't too bad either as far as i can tell. I downloaded sketchup to try and draw this beast out in 3d space, but there is a learning curve. Few commands but doesn't always do what i want it to : ) I can do it in autocad but i'm very slow in 3d. Maybe i'll do some iso drawings to give an idea whats in my cluttered head. Any suggestions on leadscrews still? I'll talk more about mechanics once the drawings are posted up so you can see what i'm trying to explain.

[Eurisko]

Tommy,

Reid supply is a great resource for CAD drawings.

http://www.reidsupply.com/cad.aspx

They also sell precision acme rod, but probably not 1/2-10 5 start.
Their Nook rolled ballscrews look very nice, I just bought one this week !

I may save it for my next (bigger) router, still working on my 1st. Tough to work in a kerosene heated garage when the temperature is in the teens. Carbon monoxide has claimed way too many brain cells.

[~TM~]

I feel ya exactly eurisko, i'm in a one car garage slammed with a table saw, jointer/planer, dust collector, etc AND a Readyair kerosene heater...little cramped and crazy. Ok so i've been searching for some long rails for my x-axis. I found some thk dovetail rails around 5-6 footish that i can get for @$200 apiece. What do you guyz think? Good investment or keep searching...ebay is a bust for me : ( any sources you can suggest that's better than that i'd LOVE to here!!

Does any have or know where i can get a linear actuator for my z-axis? I'm considering this option as opposed to my 16mm bearings and shafts because the ease of it. Ballscrew is there, nice and sturdy, decent travel usually, etc.

What is a good distance from the spoil board to the bottom of the gantry also? I've heard around 15 inches, is that about right? i won't be doing anything crazy thick maybe max out material at 4-5"

[ger21]

What is a good distance from the spoil board to the bottom of the gantry also? I've heard around 15 inches, is that about right? i won't be doing anything crazy thick maybe max out material at 4-5"

The higher it is, the more the Z axis will flex when it extends down to the table. Why have the Z hanging 15" below the gantry? Make the gantry as low as possible. Just be sure to account for all conditions you might see, such as jigs or fixtures to hold parts, and clamps.

[~TM~]

Eurisko, did you ever receive your nook ballscrew? I was browsing through Reids sight and saw mostly thomson ballscrews. What exactly did you order? Was it .631" .2 lead? I'm still trying to decide on my lead screws. Either 1/2" 10 5start with dumpster nuts and pillow/flange bearings or a ballscrew from Reid. ANY suggestions would be appreciated : ) Which would have better accuracy.
I'm in the process of obtaining some thk linear guides and a @ 14" ballscrew for my z-axis. And i'm still using the 60" thk linear dovetail guides for the long axis.
One more question...would i be ok to use an unsupported 30mm hardened shaft (the picture above) as the gantry axis.

[Eurisko]

Hi Tommy,

Yes, my Nook ballscrew arrived within a few days of placing the order.
It is a .631 dia, .200 lead. 48 inches long.

Here's the link:
Nook .631-.200 ballscrew

Haven't had a chance to play with it yet. I'll probably save it for my next (larger) router.

I'm still trying to decide on my lead screws. Either 1/2" 10 5start with dumpster nuts and pillow/flange bearings or a ballscrew from Reid. ANY suggestions would be appreciated : ) Which would have better accuracy.

The Reid rolled ballscrew's lead tolerance is +-.004 per foot.
Reid precision acme threaded rod (single start) is rated at +-.003 per foot.

I don't know the specs on the multiple start acme rod, but I doubt that it will be as accurate as the precision acme or rolled ballscrew.

One more question...would i be ok to use an unsupported 30mm hardened shaft (the picture above) as the gantry axis.

I would try it unsupported BUT give myself the option of installing full supports later if necessary. It would be interesting to measure the difference in rigidity...

[~TM~]

Thanks eurisko for the info...I guess the ballscrew would lend itself to being more efficient than the acme screw then? I feel that the accuracy is close enough to being the same where it wouldn't matter. How fast would the ballscrew push the axis? I know that the acme 10 5 start could push them at around 150-250ipm from what i've heard, with the correct motor/voltage setup. Is this doable with the ballscrew? I'm wanting to achieve around 200-300ipm, so whatever it takes.

[ger21]

Is this doable with the ballscrew? I'm wanting to achieve around 200-300ipm, so whatever it takes.

First, you need to check the critical speed for the distance of the screw and see if you can spin it at 1000-1500rpm. And more importantly, how much torque will your steppers have at 1000-1500rpm. I'm going to guess and say very little.