[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]

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.

[doorknob]

About the DIY stepper drivers,has anyone tried that yet?

The design of a DIY stepper driver will depend to a certain extent on the stepper motor details, for example, how many wires does it have?

One simple driver circuit to consider is the following:

Easy Driver stepper motor driver

For additional info about that driver, see:

EasyDriver Stepper Motor Driver - SparkFun Electronics

[acondit]

In my book the Easy Driver is to weak (less than 1amp per phase) to really be useful for CNC.

Take a look at this link for PicStep Version 4. Also take a look at this link for pminmo for comparison of various DIY stepper drivers.

Alan

[austin.mn]

Looks like you intend to learn a lot from this first experience. Good for you. Somethings just can't be learned by throwing money at the situation. Back when I started out there was very little in the way of info out there to build your own stepper drives, and I don't think there was anywhere near as many people out there who had built there own machines.

After an exhaustive search I had finally found a stepper drive schematic and built it. I didn't even etch a circuit board, everything was soldered to a jumper wire, I think I had over a hundred jumper leads on that little three axis board. Shortly after I finished a friend turned me onto the 5804 chip. Wow was that thing easy....

I think that you are going about this project great. Anyone can buy some premade drives, and you will too on your next machine.... Geckos are great, but on an exporitory machine like you are making it doesn't really even matter that it works good. My first machines used MDF and Drawer slides, for leadscrews I used 1/4 20 allthread, I had rapid speeds of 4ipm. Even though those machines were horribly slow and were barely capable of completing projects within any reasonable time frame, I learned a ton! The next machines were better and better. I think that I am onto machine ten or so now, and working on building another one.

The newest one, a plasma table, will be capable of 2000ipm and accelerate to that almost instantly. Good luck with your project, and have fun. When you are finished you will have hours of sitting in front of it watching it crawl along chewing up material and making little projects for around the house. While you are watching it the gears in your head will be turning, thinking of all the upgrades and things you will do on the next one. There is no better teacher than experience.

[zeed]

been there done that
Building cnc out of nothing,printer steper motors,diy drivers.
Alot of people dont understand that this way is much more harder then with bought NSK linear rails and gecko for example
But looking at your machine making first cuts is worth every single headeache you had trying to build it..




PS.dont build your own drivers,for the same money you can buy it...

[lamesh99]

where do i start?
@doorknob:
it seems to me too that the easydriver is too weak, capable of less than 1amp per phase(even for my baby-steppers, they draw around 1.5amps). but it seems they launched a new one:Big Easy Driver stepper motor driver. this one has got 2,1amps per phase.

@acondit
me gusta mucho, senor. picstep seems like a "serious" diy driver. i will definitely look into it a bit further. thanks for the links and the advice:cheers:

@austin
thanks, man. cost is not such an issue to me, but i always prefer to learn something new, to prosper. if i bought complete drivers, only thing i'd learn is how to program a Kcam or mach3, and that's pretty much it. this way i learn more than just about stepper drivers, i learn how electronics work. although i did go to a specialized highschool (don't know how it works outside croatia, but i went to a 4year trade school) for an electronics technician, i still need to catch up on my knowledge and remember a bunch of stuff from school

now i see what pippin meant, you guys really helped a lot.
Thanks!

again, sorry for my engrish

[hub]

The 0.4Nm torque is not a problem, add a 1:10 reduction and it's 4Nm
But, obviously that results in a very low speed feed. Which rules out the dremel type of router since it has too high RPM for low feeds. Unless using very tiny end mills / drills..

[lamesh99]

zeed, gdje si kupio drivere, i koliko su te koštali? bio sam siguran da među skoro 200 000 članova ima i nas balkanaca
i bušilica je sigurno einhell, pevec. i ja imam takvu, ali narančastu.

[lamesh99]

The 0.4Nm torque is not a problem, add a 1:10 reduction and it's 4Nm
But, obviously that results in a very low speed feed. Which rules out the dremel type of router since it has too high RPM for low feeds. Unless using very tiny end mills / drills..

why does it rule out dremel? i thought that lower speeds would help, no bits braking, bending, no "overloading" the frame, less heating up... but the reduction is a great advice. i thought already about that, but i couldn't figure out how to calculate the ratios