Question about software for homeade CNC

[PaulMakesThings]

Hello, I'm new to CNC machines, but fairly experienced with robotics and programming. I usually work with PIC chips, and I have no experience interfacing a machine with CNC software.
I know that there are hundreds of programs to give you G-code from a drawing or model, and then a few that run the machine, such as Mach and TurboCNC, but I don't know where to begin making them interface with homeade driver hardware. I know there are probably many tutorials on this, but I don't know where to begin, so for now I just need someone to point me in the right direction.

Random info that might help (because the first response to such an open question is always "need more info")
Budget: low hundreds
PC programming skills: C++, Assembly, can use almost any
PIC programming skills: Mainly use C18
First intended project: 3 axis mini mill table, possible motorized etch-a-sketch for cheap proof of concept
Progress thus far: Built motor controllers for variable speed DC, Unipolar and bipolar steppers

[fatal-exception]

So your real project is that you want to make stepper motor drivers, right? You know that there are a plethora of commercially available drivers out there right?

You should download a copy of Mach3 and install. It will help to answer alot of questions that you will have during design.

Good luck,
Paul

[Robski]

You can start with old printers for parts and drivers and since you know how to program write a simple program.
Mach3 is a verry good begin and us Gcode to control the small steppermotors.
Some larger printers have DC motors for the router motor and the hardware you can use to make the guides for the X Y Z axis.
Don't forget to enjoy your self building it.

[PaulMakesThings]

Thanks, I've gotten parts from a few printers. And I've figured out a few ways to make gantry drive mechanisms. There are far more tutorials on how to make a CNC machine then there are on how to make driver for it. I guess what I was wondering is if you typically write some kind of driver extentions for these programs, or if they have custom settings. I know that they do allow you to customize the parallel port in a way that would make that method of connection pretty easy. But since I like working with USB, and I'm not sure how these software packages work with it, I'm hoping for some input on that. Besides, my new computer doesn't even have a parallel port, and is running windows 7, so while I don't like to ask annoying questions, I felt that finding out a little before I spend the money on software and change a lot of things around made sense. I am of course looking up what I can on this on my own, and I'll see if there's a free demo once I'm home (like many of us I only get to really work on this stuff on weekends).

And I will have fun, thanks I usually do when building robots. And a mini mill will make making custom plastic parts possible and make it even more fun!

[Robski]

In stead of using the drivers and hard ware from the printers you can try the software called Mach3 a small powerfull program what will do a lot of nice things for you and can be even a future controller for larger systems like a Mill, Lathe or a plasma cutter. The money for the software will be well spend.

[PaulMakesThings]

The printer parts are working out well for the small milling machine actually. The steppers are 1A 7.5º, big enough for a mini machine, these are big old office printers I'm talking about. The question is just of how to controll them. Mach 3, Kcam, and many other software packages look promising, and I would like to use an existing software package since designing new CNC software is beyond the scope of my project. The problem is that since I am a student and I'm going to want to show this machine to lots of people in different places, and it is a mini machine, I want it to be portable. Laptops rarely have Parallel ports, and some desktops where I may be working don't either.
The part where I need to compromise is that most of the popular software doesn't have any way to access a USB device, that I know of anyway. I've been told that USB to parallel adapters work poorly if at all. It may be that my best option would be to build a compact PC with a parallel port just to drive the machine, that might be acceptable, it just wouldent look as sleek and it would take more work to move it around.