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View Full Version : Noobie needs help!!



Summer
11-25-2003, 01:48 PM
Hi , I am lookin gfor a super inexpensive CNC router to build in my garage. Is there a set of plans to build something that is reallly inexpensive and easy easy to build?

It doesnt need to be super fast or incredibly accurate, I am just looking to get my feet wet.

Thank you

thielert
11-25-2003, 01:54 PM
http://www.crankorgan.com

I built my first mill from the Phoenix plans. Great learning experience!

Tim T

cncadmin
11-25-2003, 01:56 PM
http://www.cnczone.com/links.php?s=&action=viewfolder&folderid=6

Summer
11-25-2003, 02:06 PM
Thank you for the quick replies!!
is it possible to use drawer guides for a rotozip version of a cnc router?

thielert
11-25-2003, 02:28 PM
Sure you can. If you don't care about tolerances almost anything goes!

MDF (Medium Density Fiberboard) is a great building material for your first machine. $22 for a 4'x8' sheet at Home Depot.

Your most important investment will be a controller as this can move to your next machine.
A chopper drive like http://www.xylotex.com/ is great. Unipolar drivers with current limiting resistors can be a real pain in the neck.

Tim T

bb99
11-25-2003, 05:15 PM
Can someone define "chopper drive"? Is it a micor-step drive?

--bb99

Summer
11-25-2003, 06:27 PM
is there a set of plans out there using drawer slides and MDF? I would love to see them, you all have been very very helpful!!

Also will 33 oz stepper motors work?

thx!!

balsaman
11-25-2003, 07:47 PM
33 oz is a little light. Maybe on a very small machine (8" x 8"). The drawer slides work ok but the dust binds them up (and there will be dust). Still, some people have used them with success. Don't oil them. I know of no plans available that use them.

Eric

chuckknigh
11-25-2003, 11:32 PM
Can someone define "chopper drive"? Is it a micor-step drive?

Well, I'll try.

If you simply apply a voltage to a regular DC motor, let's say 1.5VDC, like a battery, then it will turn at a certain speed.

If you touch the leads really quick, and then take them off, repeatedly, then it'll turn at a different speed. Varying the "on" and "off" times will cause the motor to spin at different speeds, and with the right circuit it's a controllable speed. This type of controller is called a PWM (pulse width modulation) driver, or a chopper drive.

Basically it delivers full power pulses to the motor, but only for a fraction of the time...for half speed it'd be on half the time, and off half the time. This can be split up into thousands of pulses per second, though.

Now...steppers are run the same way...they're just a bit more complicated, because they require pulses sent to different *sets* of coils in the motor, in order to run. By using a chopper drive, you can increase the voltage, TREMENDOUSLY, but still have the same average "power" by varying the duty cycle. You can also vary the inherent speed of the motor, by doing this.

What this gains you is torque, and speed/responsiveness.

It is not a micro-step driver. A micro-step driver simply applies power to multiple coils, to make the motor move "between" the traditional steps.

The simplest form is a half-step driver. A full step is taken by energizing coil A, and then coil B, etc. A half step driver energizes coil A, then coils A & B, then coil B. Simple, really.

-- Chuck Knight

Bloy2004
11-25-2003, 11:45 PM
Nicely said! Add that to the tech articles!
Thank you, for increasing my understanding also.
John

chuckknigh
11-25-2003, 11:51 PM
is there a set of plans out there using drawer slides and MDF? I would love to see them, you all have been very very helpful!!

Also will 33 oz stepper motors work?

I've not seen a set of plans using drawer slides, but there's nothing that would keep you from using them. Warning...the drawer slides, though of fairly good quality, are relatively expensive ($20/set) and since they have open bearings, will wear out and develop "wiggle" in a relatively short time.

Now, construction ideas. The idea is to make a "platform" that slides smoothly, and without wiggle. We'll call that one X. Then, build another one, and mount it on top of the first. We'll call that one Y.

Now, you have an X-Y system. Z is literally just a platform turned on end, so it moves up and down! Simple!

Once you understand how these things are supposed to move, it's pretty easy to figure them out. The hard part is the electronics...and there are some practically plug-n-play options, out there.

Take a look at http://www.crankorgan.com and look at the pictures. Once you start to understand how these things move, his pictures will provide a wealth of information and inspiration for you. His plans aren't badly priced, either...

If you really just want to get your feet wet, let me make a suggestion. Most people interested in CNC have a home workshop, and most have a drill press. A drill press vise is a useful gadget. A cross-slide machinist's vise is a bolt-on X-Y table, for your drill press...a "specialty" version of a drill press vise.

Handscrews move each axis. Bottom line, if it moves by *turning* something, then it can be connected to a motor.

Just buy one of those (Homier tools has one for $20!) and convert it to computer control. They're small (4x6") but well constructed and practically ready to go, out of the box. A pretty good CNC-101. Suggested upgrades include *cleaning* the sliding surfaces, and upgrading the screws, but that's only to improve the performance...but making improvements can be done in a later stage! This is just to get you started.

As for the 33 oz-in motors, sure they'll work! They won't have much power, though, which means you'll either have to gear it WAAAY down (slow!) and/or take multiple passes to cut most materials. A cheap source for much beefier steppers is to take them out of old surplus HP LaserJet printers. Models I, II, and III all used the same stepper, a 100 oz-in unit that's very well built. In my area, I can pick up the printers for $0.50 - $5, without even looking hard. Thrift stores and church rummage sales are a great source. Companies sometimes throw them away, too, when they upgrade!

Just keep your eyes open, and you'll be shocked how cheaply you can get components.

-- Chuck Knight

Summer
11-25-2003, 11:58 PM
thx chuck!
Im gonna buy a set of plans I think and look for some old printers lol!!

bb99
11-26-2003, 11:22 AM
Sir Chuck,

Thanks! Your description is quite clear and easy to understand.

--bb99

Mr.Chips
11-26-2003, 11:47 AM
Chuck,
I'm interested in that $20 drill press vise from Homier tools, can't find their home page, trying to see if they have one in Austin TX. Can you send me a link?
We have A Harbor Freight in Austiin and that vise is $35+. Been waiting for it to go on sale but no luck.

Thanks
Hager

cncadmin
11-26-2003, 11:52 AM
http://www.homier.com/default.asp?page=categories.asp?dept=1

chuckknigh
11-27-2003, 12:08 AM
Sorry, I just took a look at the link I had saved, and it wasn't Homier, but Cummins Tools. Sorry...

http://www.cumminstools.com/browse.cfm/4,92.htm

That'll bring up the exact vise I have. Cummins and Homier tools both do a "travelling show" sale at the local fairgrounds, a kind of sale which seems more common out here in the country than it was when I lived in Dallas.

Fair warning...it's a cheap vise. Pretty well designed, but with Chinese quality control...that means NO quality control. Take a look at several, and buy the "best" one, if you can. The guys on their truck had no problem with my doing this.

Since you have a Harbor Freight local to you, I wonder if they'd "price match" the Cummins web site? Couldn't hurt to ask.

I'd ask in person, at the cash register, with the vise sitting on the counter, and a printout in your hand. Force their hand, if you will...

-- Chuck Knight

Summer
11-27-2003, 12:37 AM
could I make that into a CNC?

chuckknigh
11-27-2003, 12:53 AM
Yes, but only 2D. It'll move in an X and a Y plane, only. You would need to construct something that would mount a spindle above it. The guy from whom I got the idea, used a drill press as his Z axis. He puts a "pause" in his code, and then raises or lowers the bit, manually.

Here's a video...
www.electronicsam.com/video/VIDEO2.mpeg

We had a brief discussion, a while back, about this platform being a good one on which to learn CNC -- it's stiff, has screw driven X and Y axes right out of the box, and takes a lot of the uncertainty out of the equation, for the first time builder.

Anyway...the conversion is simple. He kept the leadscrews and nuts, and just mounted some motors onto them. He just used some pipe to mount the motors in place of the handwheels, made a connection with some couplers, and hooked it up to his PC. Seems to work pretty well, based on the video.

There was a problem with backlash...he took care of it by entering in compensation, in the TurboCNC setup. The best way to handle it is to get rid of the backlash, physically...compensating for it is a hack, but it does work, and from the looks of his test cuts, it works pretty well.

My own thought on recommending one of these for a first project, was that if it was an unsuccessful conversion, or an aborted effort (let's face it, not everyone finishes their projects...) then the vise would still be useful as a vise...

I'm upgrading mine to a better quality set of leadscrews, and am using a nylon insert in the original thread castings, to do it. It is important to me (why, I'd never be able to explain) that I not modify the original castings, while doing my own upgrades...

-- Chuck Knight

Summer
11-27-2003, 01:25 AM
thx chuck!! that is some great stuff!