PDA

View Full Version : NEW MEMBER: new joiner Leighton Buzzard



mmcp42
29-12-2010, 09:09 PM
Hi all
Just started building a very primitive CNC router (or is it a miller - what is the difference?)

looking to se what others have done, pick brains and get ideas
may be able to contribute some gcode software a bit doen the line

anyway - hello!

Mike

irving2008
29-12-2010, 10:04 PM
Hi Mike and welcome to the site. Lots of info here. Routers usually have the workpiece fixed and the cutting tool moves in at least one of X or Y... mills usually have a stationary cutting tool and the workpiece moves in both X and Y.... Mills are generally of more massive/solid construction and can generate higher cutting forces...

mmcp42
30-12-2010, 04:27 PM
Thanks irving2008
I always thought they were similar, must have missed that subtlety!

In that case I'm looking at building a very small mill

moving xy table
z gantry fixed (well apart from going up and down!)

initial aim is pcb milling

Jonathan
30-12-2010, 09:13 PM
moving xy table
z gantry fixed (well apart from going up and down!)

initial aim is pcb milling

For milling PCBs is a moving table neccarily the best idea? You want high acceleration and feedrate. Moving the table will require a greater force than to move the spindle, assuming the table is heavier, which limits your acceleration (F=ma).

You'll need to work it out properly, but it might be something to think about...

M250cnc
30-12-2010, 10:04 PM
I thought that etched was the way to go.

I have seen a thread about hacking a printer to print directly.

As far as moving tables go that could be done but takes a lot more floor space than a moving gantry.

It would be more expensive and more difficult maybe that's why you don't too many of them done.

Phil

Sent from my HTC Desire using Tapatalk

irving2008
30-12-2010, 10:11 PM
For milling PCBs is a moving table neccarily the best idea? You want high acceleration and feedrate. Moving the table will require a greater force than to move the spindle, assuming the table is heavier, which limits your acceleration (F=ma).

You'll need to work it out properly, but it might be something to think about...All depends. For a small machine with limited cutting forces (and PCB milling meets that requirement) a moving table made from, say, acrylic could work quite well and might well be a lot lighter than a spindle/gantry arrangement. The main impact on acceleration is leadscrew inertia, so keeping the screws small and short and limiting travel would be advisable. Few 'milled prototype' PCBs are going to be larger than 160 x 100mm I'd guess..

mmcp42
31-12-2010, 10:34 AM
indeed I am aiming for small PCBs
My start point is an old scanner with a small stepper motor
If I can achieve an A5 workspace I'll be pleased

Prototype is already moving XY 200mm by 70 mm (8" by 2.75" in old money)
I have a Dremel that I plan to use as the spindle
Z stage is built, but awaiting motor coupling