jamius.com

Hi everyone!

My first post.. Lets make it a good one.

For a few years I have been pondering the idea of getting a cnc mill... I was originally going to save up around $4000 for a factory made mill, but I stumbled on a website that goes through making one step by step. (http://buildyourcnc.com/latest.aspx)The idea is to make a functional ( but ugly) mill that can create another super nice looking mill, hopefully high enough quality to satisfy my needs of making great parts with good enough accuracy. (.01mm would be great). It would be great if a few of us could start making one, and show the progress in this thread. Jamie that includes you, I know you would like to CNC some metal plate, stuff that puny LASER BLASTER can't cut.

I think I will be going for a 2' x 4' cutting size...

This will be a long project for me. I need to get some finances and time. I have maybe 5 different projects going on right now. More on those later.

P.S. Jamie, GREAT IDEA on hosting a forum! Good stuff!!!

The hardest part about making a small mill is the electronics. You need the right motors (stepper motors or I guess servos could be used), and you need the ability to control them. I'm sure you could buy pre-made motor controllers but that's no fun! Building the actual frame and rails is the easy part.

Programming your own microcontroller would be the most fun and educational way to go. It's not hard, per-say, just very complicated. I've done a bit of microcontroller programming myself, but I'm always held back by the fact that I'm not an electrical engineer. I can make the microcontroller do whatever I want, I just suck at making GOOD circuits.

Programming microcontrollers is all about turning certain switches on and certain ones off. If you want your MC (microcontroller) to do THIS, you need to turn this switch on, this one off, and set this bank of switches (bits) to 165. That's pretty much the extent of programming them. (You need to know the programming language of course, I program in C.) All MCs (at least the ones I've seen) come with an extensive manual, that tells you EXACTLY which switches to turn on and which ones to turn off.

Anyway, I've toyed with the idea for a while as well, if you get yours working I'd love to see how it turns out. Apparently you can use motors out of old printers... They use steppers.

What do you plan on using for a cutting blade? Don't forget the width of the blade when you're making your CAD files. And if your blade is mounted center to where the "line" is on the computer, it's going to cut half of the blade's width INTO whatever you're cutting.

This is great news. I am more proficient in electronics versus the structural part of the project!

For stepper motors I plan on using NEMA motors. I am not sure on size but I am guessing at least 300oz of torque. Those will be last on the to do list. (I like to save the fun parts for last)

The 24v or 36v power supply is easy to construct as well. Just a transformer, rectifier, a few caps and a nice enclosure. Not sure on the PCB, if I get my laser printer pcb method working, I will likely DIY with a serial port, or maybe USB FTDI.. If not, I will get a kit from a reputable site.

Cutting blade will be a router. Not sure if I will cheap out and get a harbor freight one or something more 'quality'.

Structure will be made out of MDF like the diy website. Next version will be a better quality material. Not sure what yet.

Good news is that there are a few open-source CNC projects out there, so the software and electronics aren't reinventing the wheel. First one that comes to mind is the "cupcake CNC", which is based around doing small tricky things but ought to be scalable up to just about any size.

Damn, name escapes me, but there's another one where the system is designed to build all its own parts. So you find somebody who's built one, and they can run all the parts you need to build yours. Nice sharing model, that.

LithiumFlame wrote:This is great news. I am more proficient in electronics versus the structural part of the project!
...
Structure will be made out of MDF like the diy website. Next version will be a better quality material. Not sure what yet.

That's awesome! Good for you! I would have to say my greatest electronics achievement was a moonlight I built for my fish tank. I used phototransistors to check for light, and when the lights went out, the sunset/moonlights came on. First I had bright white lights that dimmed down slowly so the fish weren't shocked by the sharp cutoff of light. Then the moonlights came on, and the "moon" moved across the sky. Then in the morning the "sunrise" lights came on to acclimate the fish to the bright lights about to come on. It was cool. Never worked the way I wanted it to (probably due to my shody wiring), but it was cool none the less.

Just a warning though, if you haven't worked with it, MDF is a... uh... well it's hard to work with. It's decently hard to cut (even with brand new saws), and it gets dust EVERYWHERE! (You're essentially cutting through glue...) And, you CANNOT get this stuff wet. It will swell up like a... well.. it'll just swell up really bad. Then it's unusable. I honestly don't know if you can seal it with polyurethane or something. I'm sure you could, but that's just one more step ya know? I used to use it to build speaker boxes for people's cars. It's fine once you get used to it. Just don't say I didn't warn ya.

The 24v or 36v power supply is easy to construct as well. Just a transformer, rectifier, a few caps and a nice enclosure.

So, as I'm trying to learn these types of things, I'm going to try to guess what each component is for.

The transformer is easy. It drops the mains voltage (110VAC/220VAC/whatever) down to 24VAC or 36VAC. Then the rectifier makes that AC into DC. And the caps are to give you a nice constant source (gets rid of ripples). Now, I have a question for you, how the HECK do you buy transformers. I was looking into one once to build an automated lawnmower with the electronics powered by a car alternator, but for the life of me, I couldn't figure out which one to pick! I usually buy that kind of stuff for digikey, and they have a million, so maybe that was my problem...

You are correct.

This will be a new experiment for me also. I usually salvage my transformers from useless junk. The burnt out ones make for MILES of super thin wire, so not useless either.

I will likely buy a new one since I do not have anything that fits the bill here.
I think you would need to know the amperage you will pull and find a suitable transformer based on that. Make sure you get either a step-up or step-down based on your requirement.

Thanks for letting me know about the MDF. What would be a suitable wood to use instead? No need for fancy, a cheap species will work fine if the flex is not much different from MDF..

LithiumFlame wrote:Thanks for letting me know about the MDF. What would be a suitable wood to use instead? No need for fancy, a cheap species will work fine if the flex is not much different from MDF..

Well, that is the thing. MDF is VERY stiff. I honestly don't think you can bend it without breaking it. If you take care to not get it wet, I think you'll be fine. Just don't try to cut it with a dull saw/router bit since you probably already have the router.

I built one last year out of x and y axis belts/pulleys scavenged from various different printers/scanners. mounted it all in a wooden frame and wired in electronics and my mates code, hooked it into my computer and bobs your uncle, works a treat! i cant find the exact guide i followed as it was in some obscure English magazine, but there are lots of guides online (including the one you linked to) for example: http://www.instructables.com/id/How-to- ... aply-and-/

My advice for anybody looking into getting started with CNC: Do it! great fun and you get a great product at the end of it all. mine is a little on the small side but i have also used the skills i learned from this to build a laser cutter. And a desktop CNC is nice
Good luck to you matey!
Jack

3 tenths accuracy is not easy to achieve even with a factory built CNC mill. Ball screws, linear ways; all components must be manufactured and installed with high levels of accuracy if you want your machine to hold close tolerances. If you plan on machining materials such as steel, rigidity is another factor that must be accounted for with high precision.

I've looked into this as well! I liked these approaches:

http://www.brusselsprout.org/CNC/

http://www.fromorbit.com/projects/picstep