Extreme Newbie, please be gentle

[imagineer]

Hello from Northeast Ohio. A little background: I’m a Mechanical Engineer at a small manufacturing facility. I spend the bulk of each day designing and drafting (AutoCAD) components to be manufactured. Most of what I develop is machined on CNC’s (Two Romi’s, one Cincinatti Milicron and one huge Emmegi Satellite). I’m competent at machining, welding and woodworking. I know enough about electronics that only 1 in 5 of the projects I build go up in smoke. This next project is my first foray into CNC.

I’m looking into building a small, cheap “rough draft” version of a CNC mill. I plan to use small stepping motors (like from old printers), threaded rod for screws and rod stock for shafting. The remainder of components and the material used will, I’m sure, be entertaining. At best, this “rough draft” might push a dremel tool, but that’s not its purpose. The real purpose is to develop and prove out the software and electronics before investing in high dollar mechanical parts. Eventually, I plan to scale up and build a 3’ or 4’ square, 3 axis CNC unit that can be adapted for a router or a plasma cutter.

I have access to a copy of BOBCAD 18 and a spare PC to run it. I expect I’ll have to build separate stepping motor drives for each axis and maybe amplifiers too.

What I don’t know is what will be necessary between the PC and the driver boards? Will the output (I assume via the LPT port) sequence the signals to the stepping motors?

Also, will BOBCAD allow me to calibrate the output to match the screw thread pitch?

Thanks in advance.

[smarbaga]

hello:
in most cases the motor controller board provides the step sequence to the motors. the printer port just puts out a step and direction signal (hi, lo, +5v, 0v)
imo, i would aquire whatever i can get, then design the machine's aspect around what you have, or what you think you can get.

[patmul]

I'm new to CNCZone myself, but I've done a bit of Home CNC.

BobCAD does not run the machine itself...it just generates the G-Code that the CNC Controller software understands.

The G-Code is always in coordinates (inches or millimeters). The CNC software which runs your steppers (the CNC Controller) converts the G-Code commands and coordinates into step-and-direction commands. This software also does the dimension calibrations on your CNC machine's stepper-leadscrew combinations so that it "learns" how many steps it takes to move a spindle precisely one inch (or mm) on each axis.

I suggest you acquire a version of "Mach" for the controller software package. Older versions (Ver. 2 or so) can be found on the net for free downloading. You can also download an almost-fully functional version of Mach 3...the latest version...from www.machsupport.com. Installing and playing around with Mach will teach you a great deal about CNC!

For your first CNC machine you can find 3-axis, 2A/motor stepper motor drivers on eBay for under $100.00. You won't need any other amplifiers, etc., just a cheap 12 or 24-volt power supply.

The Stepper Drivers are stepper-motion converters which use Step and Direction pulses from your CNC Controller software through a Line Printer port.

The CNC drivers and software are really very easy to setup and work with. Building the CNC machine itself and getting it to run smoothly and efficiently is the hard part!

[pminmo]

An overview: http://www.pminmo.com/wiki/index.php...ystem_Overview

Although this is somewhat dated, it still gives you a look see as to what some of the software does with the parallel port signal wise: http://pminmo.com/pport/pport.htm

I say dated because most of today's software allows pin mapping.