Simple questions for building CNC

Hello all :), I want to start building my own CNC at home, so before I begin, I want to know some things like:

1. Will this stepper motors work or be strong enough to cut hard wood, acrylic and thin sheets of metal ?

The complete kit is: CNC Kit 3 Axis NEMA 23 Stepper Motor 76MM *3+ TB6560 Driver Controller + 1 Power Supply 350Watts( 24VDC/14.6A)

Specification of 57BYGH76-401A Motor:
Holding torque: 270 oz.in
Phase Resistance: 1,13 ohm
Phase Inductance: 3,6 mH
Lead wire: 4

2. If I make a large cutting area, like 40"x40"x5" ...will these motors decrease performance or cutting speed/torque instead of using a small cutting area ?

3. If I cut acrylic or plastic, will I have problems with heating when cut ? How can I solve it ?

4. What will be the estimated average speed of cutting or how to I calculate?

5. What parts do I need to measure if I want to make a customizable sized cutting area ?

6. And a dumb question:P - if I want to cut a piece of wood as large as the cutting area..how do I keep the wood in place without interfere with the drill? :withstupi

Sorry if I posted in the wrong place and sorry for my bad english, I'm new :rolleyes:

1) The materials being cut really have no impact on choice of stepper motors.

To properly select motors, you need to know how much weight your moving, how fast you want to move it, and how you're moving it.

2)If all other components remain the same, and only the size changes, than performance will be the same.

3) Depend on spindle speed, feedrate, and type of tool you use.

4) Cutting tools have a recommended chipload, and you adjust rpm and feedrate to achieve the recommended chipload.

5) don't understand the question?

6) Holding parts down to the machine can sometimes be very difficult. methods can vary from machine to machine. Sounds like vacuum might be the best solution.

While Ger is correct when he says:

"If all other components remain the same, and only the size changes, than performance will be the same."

the trouble is that when you increase the size of your machine, it will generally have to get heavier, especially parts like the gantry, which, in order to maintain the same stiffness over a larger span will need to increase its dimensions geometrically as the span increases arithmetically. To move a heavier gantry around, you need more torque from your motors, You can get that by using mechanical advantage to trade speed for torque, or by substituting stronger motors for the weaker ones suitable for a smaller machine. Since stepper motors typically don't go very fast anyway and their torque decreases with speed while their inductance increases with torque, at a certain size it makes sense to go to servo motors, which typically have speed to spare.

Andrew Werby
www.computersculpture.com

#4 - The speeds will not be that great with a TB6560. I have one and use it with 57BYGH420 motors, I get 12inches per minute and in the CNC world that is pretty slow. Works great, just slow.