Motors and Motor Drivers

[geometrix]

All,

Hello. This is my first post.

I am a mechanical engineering consultant by profession. I would like to build a CNC router for a "pet" project. I have very good mechanical engineering expertise and some electronics expertise.

I want to build a CNC router with travel of about x=24", y=36", and z=8". I want a large build envelope because I want the flexiblilty to cut a sign out of wood, or a consumer product that I am developing out of Delrin. I may even want to cut an instrument panel out of 6061 aluminum. I do not expect that I will be cutting steel.

I have found many resources for acme screws, ball screws, and slides, bearings, etc. I have also found some very good resources for stepper motors (i.e. Jameco).

As I begin to put together a set of requirements, many questions come to mind. What size stepper motor do I need? Can I build a stepper motor controller using a Basic Stamp or PIC microcontroller (I have designed a stepper motor driver before). When I connect my controller to my PC, does the CAM software just turn the motors on and off, forward and reverse? Or is something more complicated happening? In other words, if the output of the CAM software just telling the controller to move x, y, and z, are these just HIGH and LOW signals to my contoller? When my controller receives a X HIGH command, it moves in the x-direction until X LOW? Where can I find this protocol???


Thanks,
Neal

[ger21]

First, I recommend taking a look at the Joe 2006 model. A proven design that many members here have built, and about the size your looking for.
http://www.cnczone.com/forums/joes_cnc_model_2006/

Originally Posted by geometrix As I begin to put together a set of requirements, many questions come to mind. What size stepper motor do I need?

Probably around 300 oz-in

Can I build a stepper motor controller using a Basic Stamp or PIC microcontroller (I have designed a stepper motor driver before).

Define controller? Most here use a software control program. Mach3 is by far the most popular.

When I connect my controller to my PC, does the CAM software just turn the motors on and off, forward and reverse? Or is something more complicated happening? In other words, if the output of the CAM software just telling the controller to move x, y, and z, are these just HIGH and LOW signals to my contoller? When my controller receives a X HIGH command, it moves in the x-direction until X LOW? Where can I find this protocol??? Thanks, Neal

Stepper drives take a step and direction signal. The direction is either high or low, depending on the direction. Step signals are sent to the motor individually. Most stepper motors need 200 steps per revolution, but most people use microstepping drives which make it 1600 or 2000 steps per revolution. Mach3 can output steps at up to 100,000 per second with a fast PC. You also have to consider acceleration and deceleration. There is a lot involved in controlling a machine.

A CAM program does not control a machine, it just outputs a g-code file from a drawing or 3D model.

[geometrix]

Gerry,

Thank you for all the great info. I looked at Joe's design and it is in fact quite similar to the CNC router that I have started designing. The biggest difference is that I think that Joe's machine is fabricated from aluminum and my first machine will be fabricated from wood. After I get the first machine fabricated, I will look into using that machine to build the next...and so on...

Thanks,
Neal

[ger21]

I was referring to Joes 2006 model, which is MDF. Not the 4x4 model, which is aluminum and steel.