Build a CNC machine that can mill a circle out of a block of foam.

Hi all; new guy here; some pretty basic questions.

Bit of a long winded post - things that I think I might find helpful 1) Links to - buy this kit; once you’ve got it setup; you’ll be well on your way. (I’m in Europe) 2) Blogs which will help me build my understanding of any of the below 3) Any answers or corrections on any of the below.

My goal is to build a ‘hobbyist’ CNC machine that can mill a circle out of a block of foam.

I feel like I’m not quite understanding the key differences in the implementation of a 3d printer and a CNC machine. My brain is trying to tell me - they are the same; because they both require running a sequence of g-codes.

I guess I’m not miles off - as http://reprap.org/wiki/G-code states: RepRap firmwares are quite usable for CNC milling”

Seems like a Uno or a Mega is the correct starting point (for printing or CNC) But - then grbl is the software for CNC; as opposed to Marlin for printing However; I understand parts of Marlin are based on grbl. What makes grbl ‘better’ for CNC? Does it just avoid some of the extra’s that come with Marlin that aren’t needed? Or do the CNC controlling systems speak to grbl easier?

And then; I either need EasyDriver V4.4 or the Grbl Shield. Does the EasyDriver limit anything? Or is it mostly more setup? As I have to wire up 3.

The printing equivalent here is Ramps + Pololu Drivers (which was ‘inspired’ by EasyDriver) but as I understand they aren’t ‘out the box’ compatible? Although there is http://sourceforge.net/projects/grblforramps14/.

Is the main reason for the Pololu Driver being separate from the Ramps board; for easy replacement when the Pololu driver burns out?

Once I get to turning my stepper - Ramps and EasyDriver are compatible with any bi-polar stepper.

Thanks, Brent

not sure if there was any direct question in there.

look for Robin2's post of a link for an introduction to steppers.

also google for the driver A4988 stepper driver. simple to use.

understand that cutting foam has very little power needed, so wood might not be able to be cut on the same machine and metal is out of the question.

you can cut foam with a hot wire. easier than using a dremel blade but you can also cut it with a milling cutter. very easy stuff.

brentgracey: I feel like I’m not quite understanding the key differences in the implementation of a 3d printer and a CNC machine. My brain is trying to tell me - they are the same; because they both require running a sequence of g-codes.

A 3D Printer is a kind of CNC machine. Not all CNC machines are 3d Printers. For example a CNC milling machine is not a 3D Printer. Neither is a CNC lathe.

brentgracey: Seems like a Uno or a Mega is the correct starting point (for printing or CNC) But - then grbl is the software for CNC; as opposed to Marlin for printing However; I understand parts of Marlin are based on grbl. What makes grbl ‘better’ for CNC? Does it just avoid some of the extra’s that come with Marlin that aren’t needed? Or do the CNC controlling systems speak to grbl easier?

A 3D Printer generally has 4 or more stepper drivers: three for the motion system and one or more for extruders. It also has inputs and outputs for the nozzle heat, the build platform heat, a cooling fan, and other mechanisms. GRBL uses and Arduino UNO and doesn't have enough pins to control much more than three steppers. Marlin runs on an Arduino MEGA 2560 so it can support all the CNC stuff plus the printer-specific stuff plus an LCD control panel.

brentgracey: Is the main reason for the Pololu Driver being separate from the Ramps board; for easy replacement when the Pololu driver burns out?

Yes. And it allows you to choose between different models of stepper driver.

My goal is to build a 'hobbyist' CNC machine that can mill a circle out of a block of foam.

This was posted to the forum recently concerning a DIY CNC setup.

https://www.youtube.com/watch?v=f4ptBpVOSuY

zoomkat: This was posted to the forum recently concerning a DIY CNC setup.

https://www.youtube.com/watch?v=f4ptBpVOSuY

That man had time on his hands to waste.

Chuck.

Link to Stepper Motor Basics

I think you need to decide (at least roughly) how the mechanics of your foam cutter will be arranged.

If you can cut right through the foam in a single pass (as you could with a hot wire) then you just need two stepper motors for the X-Y motion. If you have to cut it in layers you will need a third stepper for the depth motion.

You might want to consider whether the cutter should be moved or the block of foam. You could move the foam by attaching it to an X-Y table.

I wonder would a device like this Polargraphbe suitable for the low loads involved in cutting foam.

...R