[PurduePete]

I would like I build a simple computer controlled desktop CNC machine. It will be for cutting circuit boards. I realize that saying simple is probably a bit off. This is my first undertaking with stepper motors. It is not my first endeavor into wiring or mechanical projects. I am an engineering technology student at purdue so I should be able to handle it. But I have several questions that I'd like some help with when it comes to motor control.

I would like to build my own board first off. Limit switches would be nice but to start with, but it will not be required. The unit from lintrix has a very nice board but inhave been unable to find the schematic. After I get it running I can cut circuit boards and make a more complicated board or a better one. Probably will make a second machine. The instructable below is what I am loosely basing my project off. The motor controller used is a little odd with the lights but I will include them anyway. But my question is, will this board work well? If not can someone suggest a better schematic to use?

One last question. Can I use this parallel port board with an adapter for USB and not run into problems that can't be overcome?

http://www.instructables.com/id/EJ3KFVBF5R8QRL3/

Any suggestions or tips would be awesome. Hope this is in the right place. I have used search and scrolled through numerous posting but haven't found what I needed.


PurduePete

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[doorknob]

That stepper driver is a very simple, low-cost, no-frills unit. While it has its limitations, it may do OK for just getting started, and it will let you get some hands-on experience with stepper motors and with using a small desktop CNC. Later on you may want a more capable driver (for higher speed, microstepping, or other features).

In general, USB to parallel converters are not suitable for use in CNC applications.

There are other alternatives that you might look into, for example the Linistepper driver (which can be built from scratch, or you can obtain a ready-made PC board for it, or even a complete kit of parts):

Linistepper V2 Build Instructions

[PurduePete]

I have been looking for an alternative to the controller board that I posted. There really was no information on it which made me nervous. People get it to work though. There is information on this new board that can teach me better how to use it and learn how they work. Maybe I can design my own some day even.

I do have a question. People suggest going with NEMA 23, which seems like a form factor for the motors, but I was thinking NEMA 17. Would this board power these motors? They are nema 17 unipolar two phase stepper motors. I can't find much more information than that. 6 wires so according to the site it should work. Not much information on torque, voltage, and amp requirements though. It is really only for small pcbs so I don't think the small size motors will affect much.

The forums have a lot of information but I've been having trouble sifting through it all. Would like a simple tutorial that shows me how to build what I need. Just want to mill small pcbs to begin with. Once I figure out how to I will move up and make a better one that is larger so I can cut metal too.

The heat kind of worries me with the linistepper. Suppose it might be worth a shot. I have the PIC programmer and everything so I should be able to do it. Thanks for the post. Are there other options such as the one I posted that could I interface using USB or this computer has a 17 pin port similar to the parallel port, just lacking the full 25 pins. No clue what it is called. I'll look it up though.

[doorknob]

Motors in the NEMA 17 form factor can have torque ratings that vary over a wide range. So it would be best if you could get an idea of the torque required to do the job as well as the torque rating of the motors that you intend to get.

According to http://db.sanyodenki.co.jp/stepping_..._e_069-073.pdf, which looks like it might have the specs for that motor or a similar one, it looks like the holding torque of the motor to which you linked may be rated at 42 oz-in, which is a relatively small torque. Maybe it's enough for a really small machine running at a slow speed, but my guess is that you'd be safer getting a motor with a higher torque rating. Either the board linked in your first post or the Linistepper should be able to drive that motor, however.

Another resource that you may find useful for understanding how steppers and drivers work is PMinMO.com - look at the article list on the right side of the page.

For a USB-based stepper driver, you might consider looking into projects based on the Arduino microcontroller board - there is software that lets you download "gcode" to the board over USB, and then the 'grbl' firmware on the board translates the gcode into step and direction pulses, and there are stepper driver boards made to mate with the Arduino, or you can use another type of driver (such as the one that you linked to or a Linistepper) to actually drive the motors.

I'm not sure what to recommend as far as a design for a small-footprint CNC machine that can do PCBs, though - there is a forum on cnczone devoted to PCB milling and maybe you can find some ideas there.

[PurduePete]

Thank you. I will read the article that you mentioned to try and get a better handle. This is a project that is a bit further into the future but just trying to get a better handle on the electronics portion. I've got a handle on the mechanical aspect. I need to get a better understanding of the computer interface, been having a tough time seeing how the connect to the computer. Especially if a converter to USB is out of the question.

I didn't know that there was a section devoted to PCB milling. I'll look at that and see what some of those guys have to say.

Again, thank you for your time and help. I really appreciate the response and linked information, it has helped me a lot.

[boldford]

. . . . . .I need to get a better understanding of the computer interface, been having a tough time seeing how the connect to the computer. Especially if a converter to USB is out of the question. . . . . .

I would suggest you look for a cheap P4 machine with a paraport on e-bay or somesuch.