Newbie- Complete hobby build from SCRATCH, 3axis

[lamesh99]

Well, hello there! I've been browsing the forums for some time now, and i am more than happy with what i've seen. An idea came to me some time ago, "Why not build somethig useful for myself?". So, i started brainstorming, and found that a small CNC router would do just fine.
So, (and please, if there is a thread smilar to mine, redirect me), less talk, more questions.

First, i am building the router from SCRATCH, from nothing, virtually. I found some DIY stepper driver designs, but i'm wondering, has anyone tried that yet? Expenses are not such a big issue, but i love doing (fabricating) everything i can by myself. Plus, i am an electronic technician, so i should, as much i can, learn from trial and error.

Next, i was thinking of 40cmX40cm (cca15inX15in) working surface. Would MDF frame do the trick? Of course, there would be some aluminum "L" profiles for fastening and weight reduction. I have a habit of planning as i go. So, the frame will be changed a bunch of times until completion.

Motors are Minebea 17PM-J503-P2ST. They were built specifically for something, since i can't find specifications for that specific type. However, the specs for a similar model, 17PM-J442B are: 1.8deg step angle, 400mNm holding torque, 0,9amps rated current, 5,6ohms resistance, supply voltage 24V. I believe that should be strong enough to move a little CNC machine. Any objections?

For the cutter itself i intend to use a small dremel-like "drill". Again, i understand the limitations of the drill, so i will probably mill only styrofoam, or something else as soft.

That's about it. Sorry for my poor engrish. If there are any suggestions, or ideas, please, by all means, tell me.
Thanks in advance!
Marko

[doorknob]

If I have done the conversion correctly, it looks like a motor with a rated holding torque of 0.4 Nm is equivalent to a torque of 56 ounce inches.

That is quite small compared to the ratings of motors more typically used to build hobby CNC machines. It might be sufficient for a very small, lightweight machine (such as one using a dremel to cut styrofoam), however.

[lamesh99]

this is the stepper i intend to use. ordered from ebay, thought it would work fine for a starter.

[lamesh99]

a single reply? might as well delete the thread, since there is nobody willing to help out a new guy...

[jm82792]

From my infinitely shallow experience that stepper you are purchasing will not suffice for a machine with a 15'' by 15'' working surface. I was advised by multiple individuals that a 200 ounce stepper motor will do decently but not great for my 12'' X 9''.
MDF has been used in many smaller machines, I'm not sure how big you can go or any specifics.

[lamesh99]

Well,the motors are quite small,but i plan on using up to 10mm thick plates (for moving parts)and the "dremel like drill" only weighs about half a kilo,so i think they will be able to pull the weight. Nevertheless,i will leave room for something with more torque.
About the DIY stepper drivers,has anyone tried that yet?

[pippin88]

Originally Posted by lamesh99 a single reply? might as well delete the thread, since there is nobody willing to help out a new guy...

You are probably excited about starting this project, but patience is a virtue. You'll learn an amazing amount of stuff here and people are very willing to help (I've benefited from a lot of input during my first build) but you can't expect 10 answers instantly.

[lamesh99]

@pippin:
You are right,friend,i was a little impatient. Luckily, i am working at the moment,so i can wait

[eSilviu]

imho, for hobby, this are exactly the needed components. It will not make a perfect machine, but the builder will see where are the weakest points of the structure.

[lamesh99]

@eSilviu:
my intention exactly. first-time everything is always an a experiment, right?

[PaulRowntree]

Many have built their own stepper drivers, and for small current switching it is not that difficult. I bought the Gecko540, which is very popular for CNCs because it adds in several safety features and tries to remove mid-band resonances that rob you of power and speed.

Check out the stickies on the forum; there are some design guidelines and calculators for estimating movement speeds depending on the components that you use.

[lamesh99]

now to talk a bit about the electronics. i am building (trying, actually) a circuit that i found on another site, from a guy named tom mcwire. i modified the circuit with some help from my boss/tutor, and separated the motor drives, since they were all on one PCB, as one circuit. after some time, and some testing, the prototype PCB was made. of course, it wasn't until i started drilling holes i noticed some major mistakes in the circuit. back to the drawing board. with the driver circuit repaired, i produced the splitter circuit. again, not without mistakes. well, the mistakes have been fixed,and the circuits assembled and soldered. AGAIN, i managed to turn two IC's upside down on the board. until that is fixed, i can't say that i have a stepper driver. but, rest of the circuitry works. tested. below are some schematics. the PCB layout is actually a 3axis driver (thanks, tom mcwire!), and the schematic is a single axis driver.

my biggest concern is, will i be able to use my laptop for control. of course, the laptop has no parallel port, so i ordered a USB to parallel adapter. will it work? i have no idea. tomorrow i'll test it on an old PC at work, with LPT and an XP pro.

edit: the USB to LPT adapter obviously doesn't work. damn. tomorrow never dies.