Making a stepper motor controller out of a PIC

[vanepico]

i am looking for a place where i can find somewhere that tells me how i can produce a stepper motor controller that can run 3 stepper motors that can be interfaced through a rs323 (serial) connector into kcam. I would like to be able to make it using perfboard and i have recently got a PIC writer which should make it easier to make. the reason i want to do this is cause i don't have any money to buy an existing product

[Tony611]

--------------------------------------------------------------------------------

i am looking for a place where i can find somewhere that tells me how i can produce a stepper motor controller that can run 3 stepper motors that can be interfaced through a rs323 (serial) connector into kcam. I would like to be able to make it using perfboard and i have recently got a PIC writer which should make it easier to make. the reason i want to do this is cause i don't have any money to buy an existing product


This my first post so forgive me if I make a few mistakes.
I think that I may have what you are looking for. It's a book written by Geoff Williams entitled " CNC Robotics, Build Your Own Workshop Bot." I actually found the book in out local library and later bought the book. It starts with a lot technical data on stepper motors, IC's and so on. Next it goes into making the circuit boards then the rest of the project follows. The web site on the book is www.books.mcgraw-hill.com. I hope this information has helped you.

[vanepico]

unfortunately i dont think my local library would have that kind of book, nor would i be able to afford it, could you scan the diagrams and information about building it possibly? thanks

[irving2008]

vanepico,

Are you looking to build something from a kit or design something from scratch?

What size & type of steppers are you considering... if you are considering any form of high power steppers, particularly bipolar ones, then you really need to be buying/building a kit, its not feasible to build such (and make it work reliably) on perfboard. Or at least consider making something to an existing design and making up the PCBs.

Whats your level of expertise in (a) designing circuits, (b) building projects and (c) laying out PCBs, particularly those with RF or high-power transient signals.

Since you are in the UK why not come visit us at www.mycncuk.com

[vanepico]

i guess i haven't really thought about the size of stepper motors, would going down the dump and getting some old printers be a good idea to get some driver circuits and stepper motors or something?

[irving2008]

you might strike lucky, although you'll not find many printers in dumps in the UK since they have to be recycled properly. Also the sort of steppers you get in a printer are generally very small ones unsuited for this task unless you are going for a very small, light duty, machine as a learning exercise.

What sort of CNC machine are you aiming to build? Start with the basics, work out what forces/friction/etc. you will encounter, determine motors/leadscrews/etc from that then determine what controller you will need. Then if money is tight keep your eyes on ebay and other surplus sites for bits, collecting over time until you have what you need.

If you've not seen them before, and for an idea of what can be done with basic hardware, have a look at the "http://www.youtube.com/watch?v=6drMZqmyXQc"]EasyCNC series of videos on youtube. Search on EasyCNC for the set or go here for the instructions

[vanepico]

i do have one stepper motor, it resembles the ones in that video you embedded

I am aiming to create a cnc milling machine to aid in the manufacture of rc plane parts such as 1/8" ply fuselage parts, i was also thinking about developing an old cd/dvd-rw laser to cut it, but until then probably mount a dremel on it

and i was thinking along the lines of a flat bed of 40 x 40, if i have a shallow enough lead srew would that not work as a "gearbox" effectively?

[irving2008]

Do you have the specs on the stepper you have? The NEMA23 case format can be anything from around 0.3Nm to over 1.8Nm holding torque and as a guide for a 300mm x 300mm work area using round linear rails and ball sliders and acme leadscrews with delrin nuts you will need something better than 1Nm holding torque.

How many wires does your stepper have? 4 wires = bipolar = best torque/speed curve but expensive drivers, 6 = unipolar = lower torque but cheaper drivers. 8 = could be used either way.

I assume you mean to use the DVD laser as a cutter. I don't think you have really enough power there to cleanly cut ply, most of the examples I've seen are cutting plastic and or light metal. Wood tends to burn rather than cut.

A dremel isn't the best tool as a cutter as the runout is poor, the power limited and the size of bits small. For a reasonable cutting speed you need more power and larger cutters. However if a Dremel is all you have then we can work with that...

What were you thinking of using as a leadscrew? For very low cost 10x2 or 12x3 trapezoidal/acme screws with delrin nuts is common. 16x5 or 16x10 ballscrews/ballnuts are ideal but very expensive.

Just what is your budget? Is it realistic?

[vanepico]

Do you have the specs on the stepper you have? The NEMA23 case format can be anything from around 0.3Nm to over 1.8Nm holding torque and as a guide for a 300mm x 300mm work area using round linear rails and ball sliders and acme leadscrews with delrin nuts you will need something better than 1Nm holding torque.

How many wires does your stepper have? 4 wires = bipolar = best torque/speed curve but expensive drivers, 6 = unipolar = lower torque but cheaper drivers. 8 = could be used either way.

I assume you mean to use the DVD laser as a cutter. I don't think you have really enough power there to cleanly cut ply, most of the examples I've seen are cutting plastic and or light metal. Wood tends to burn rather than cut.

A dremel isn't the best tool as a cutter as the runout is poor, the power limited and the size of bits small. For a reasonable cutting speed you need more power and larger cutters. However if a Dremel is all you have then we can work with that...

What were you thinking of using as a leadscrew? For very low cost 10x2 or 12x3 trapezoidal/acme screws with delrin nuts is common. 16x5 or 16x10 ballscrews/ballnuts are ideal but very expensive.

Just what is your budget? Is it realistic?

The stepper motor only has 119gm written on it, it has 4 wires( red green black and blue), it is 1 1/2" x 1 1/2 x 1", the shaft comes out the case 1 1/2".

My dad has some long (about an inch long) m4 nuts with a hexagonal external shape, i was hoping to go to a hardware store and get some M4 threaded rod for the lead screw.

yeah thats what i thought, i have some old dell dvd-rws that don't work anymore that i can salvage from

A 'generic rotary tool' is probably all i got, i also have a 2.5mm milling bit which i may be able to use
Havent really got a set budget, any money i get i suppose, i would probably try and do it on the cheap

[irving2008]

Hi... well you have set yourself a challenge then.

The motor you describe sounds lke its a NEMA17 style case... looks the same but is small than the NEMA23 thats in the video. Unfortunately it about 10x too low in torque to be of any use for your needs.

M4 threaded rod is far too thin for a leadscrew - it will buckle under the cutting force, even on ply. Also the pitch of M4 is too fine, your cutting speed will be glacial! 8mm x 1.5mm pitch might just about do (I think thats whats in the video).

If its not a rude question, I get the impression you are rather younger than the typical member here... would I be right?

[vanepico]

yes i don't have a job, which is why i don't really have a budget

[irving2008]

well there are always ways and means... it never stopped me in my school/uni years - my hobbies were all self-funded even if it took longer than I'd have liked (come to think of it, not much has changed lol)