I've put this in ideas cos I'm not sure where it fits, but the project itself is still in the ideas phase so i think it's ok :D
Basically I'm slowly assembling parts and designs for a CNC milling machine, the usual xyz stepper motors with router on top sort of thing.
What I'd like to know is if it's possible to control it from a USB-parallel converter, I've read some things about the interpreting speed not being up to it (All I have at the moment is a laptop, so no parallel port)
Or should I try and find an old cheapo desktop just to run the cnc from? (This is a less attractive option due to space considerations)
You cannot run a CNC through a laptop with a usb/parallel converter --It simply will not work. You need a full-size PC with a real parallel port.
I am just starting the second version of my CNC and I can tell you that there are about 1000 things you have not thought of yet. Read every forum and blog you can find and then read them all again. Also, if you think it is strong/rigid enough, triple it. As a point of reference, I made mine out of steel (1x2 box and 1 1/2 angle) and it is nowhere near as rigid as I need. I am now upgrading to 3x2 box tube and 2 1/2 angle --all at 1/4" thick. I am actually going to go for 3/8 thick if I can afford it. Bottom line, if you want to get through anything more than MDF at any speed over a crawl, build the crap out of the machine. In the end, I will probably be around $350 in just steel. I cannot stress this enough, making the machine rigid is your #1 priority, period.
This is the first project of this size i’ve attempted, so I’m prepared for a lot of work (and maybe doing my degree inbetween times too! :D) but stuff always crops up…
except with better linear bearings, I’ll post the results when I have some materials! I can get an old pc with no trouble, can you recommend any free CAD software for it?
with typical software is usb isn’t real time or fast enough. But, I ‘believe’ you could build a mill that used usb to make parts as long as what you were milling was forgiving. Because, you would at best be streaming the program to the arduino to convert and a pause command would not pause exactly when you asked it to. You ‘might’ be able to use a pcmcia to parallel or express card to parallel. You would need to get more info about either one of those to know for sure.
You can get a parallel port expresscard, i’ve used one with a laptop before with linuxemc, although I don’t anymore and I don’t remember which one it was.
Also, free cad software is QCad, by ribbonsoft, http://ribbonsoft.com/qcad.html I believe there is a fork called librecad now, which was from a version of qcad. You can always use blender, but that’s a bit overkill if you just want some simple 2d work IMO.
For a mill that small you could do what I did. Use Skeinforge. It is opensource software for 3D printers, but also makes GCode for EndMills, and uses a program called Pronterface for the GUI. I used it for a dremel type CNC and my laptop has no trouble running it off of USB. I also only have a laptop with no parallel port, so this is the solution that worked for me. I use a Sanguinololu board ($120 with 4 stepper drivers) but you can use an Arduino with a RAMPS 1.4 shield, both only require a USB connection. Google RepRap for more info on this route, although CNC is not well documented in their Wiki.
