[scales11]

Hi all. I am a newb to CNCs and have been eyeing this DIY CNC page:
Make Your Own DIY CNC

I would like to cut wood and I figured that I would save a few bucks by using the LinuxCNC/Free software options, 3 "easy driver"s (https://www.sparkfun.com/products/10267) + arduino, and a few cheap stepper motors I acquired (Vexta pk43-01aa 1.8° Stepper Motors (Motor Only) - PK Series)

Well in all of my excitement to build a CNC, I think I may have underestimated the stepper motors/drivers. I have not bought any parts yet (I am still in the planning phase) but I would like to know what kind of requirements I should look for in a stepper motor/driver and other general advice. I see that the initial instructable's page called for something from: Stepper Motors | HobbyCNC, but I am not sure if my cheap(?) stepper would suffice.

Will my motors be too weak or slow?

Can anyone help? I had thought the process would be:
draw in inkscape or other program -->convert to gcode-->send to arduino-->moves steppers via easydrivers.

[doorknob]

The author of the "Make Your Own DIY CNC" article used stepper motors with a rated holding torque of 130 oz-in.

If I have correctly read the linked info about the stepper motor that you chose, it looks like those motors have a rated holding torque of only 28 oz-in., which is less than one quarter of the torque rating of the motors used by the author.

So there is reason to question whether the motors that you have chosen will have sufficient torque.

The stepper motors used in the article have a rated winding current of 2.1A. The EasyDriver boards have a maximum rated current of 750mA, which is about one third of what the stepper motors in the article require. So if you were to use the steppers that the author used, the EasyDriver would not be a good choice.

The EasyDriver is a closer match for the steppers that you have chosen, but even those motors have a rated winding current that exceeds the max rated current of the EasyDriver (by around 10% or so). You could run your motors with the EasyDriver, but with a reduction of torque. But if your motors are already too small for the job, you would just be making a bad situation worse.

[scales11]

Thanks Doorknob. I think I am starting to understand things a bit better now. I am not sure what my ideal torque would be, but as you pointed out, I am certainly low.

I will look for another stepper motor. Just another question: would a circuit like this suffice in controlling these motors?
CNC 3 Axis Stepper Motor Driver Controller | Lirtex - Technology on the Edge of Time

[doorknob]

They don't give a whole lot of details, but I would have some concerns with that board. That said, it would probably work for you.

For example, it is a unipolar motor driver board, so if you get it, you will need to get either 6-wire or 8-wire motors (it will not work with 4-wire motors).

The driver only supports full steps or half steps, whereas you might want the option of 1/4 or 1/8 or even 1/16 microstepping for smoother motor operation.

It's not clear what the motor winding current setting limits may be, nor is it clear how you are supposed to set the current limit. It apparently does not do "idle current reduction" so your motors may run hot even when doing no work.

You would have to find a suitable heat sink for the 12 driver transistors.

[scales11]

Doorknob,

Thank you again for helping me out, I sincerely appreciate the advice of others who have been through this before as it always makes things easier.

I think I will end up going with the 205 or 130 oz stepper motors from Stepper Motors | HobbyCNC. They seem to be powerful enough for my wood cutting applications, and reasonably priced...unless there is a cheaper option that could still provide the power? I just found this: http://www.mydiycnc.com/content/mydiycnc-stepper-motor which, unless I am mistaken, 2kg/cm = 179 oz - in (that is the holding torque, the detent!? torque is 18.8oz)

I was trying to use my laptop as the main computer, but given the fact that it lacks a parallel port, I think I may be out of luck (I don't want to spend tons on an adapter, and an older computer would probably work just as well). As you probably would have guessed, I am trying to keep costs down, but not to a point of sacrificing quality too much.

I see many stepper drivers with a parallel port on ebay, and plenty at other sites. Prices seem to range between 60 and several hundreds of dollars. I believe most of that cost difference is to accommodate larger stepper motors, more current, less heat, etc. Is there a list or a place I can go to compare some of the cheaper options? I think I just need a computer with a parallel port + 3 axis stepper driver board + motors and I will be up and running. Does that seem correct?

Also, here is a link with more specifics on the under powered steppers that I do have:
Item # PK243-01AA, Stepping Motor On Oriental Motor U.S.A. Corp.

[doorknob]

I am a bit confused since in your first post you mentioned using an Arduino, but now you are talking about using the parallel port.

An Arduino might let you use the laptop (you would download G-code via USB to the Arduino which would be responsible for actually running the steppers, but might lose out on the benefits of using the computer's screen and UI to control the process), but if you want to use the parallel port instead of the Arduino, then getting an older desktop PC to do the job would be a reasonable way to go.

[scales11]

Sorry for the confusion. Initially I wanted to use the arduino + easydriver (or grbl) but after reading your reply, realized that they easydriver and maybe (grbl) would not be able to accommodate the power needed by the more powerful stepper motors (since I want to cut wood with this cnc). I would still prefer to use the usb over parallel, but wonder how much complicated it would make things. example:

parallel port:
computer->parallel port->driver board->steppers

usb:
computer->usb->arduino->driver board->steppers (but only low powered ones?)

I am going to review the software options as well just to I am clear.

[doorknob]

It is the driver board, not the computer or Arduino, that must be capable of supplying sufficient power to the stepper motors. So, you could run larger stepper motors off of the Arduino as long as your motor driver was capable of supporting the larger motors.

[scales11]

Got it. I have a spare arduino laying around, so I can always try to use it as a type of "usb-adapter". I still need to find a better driver board that can supply the correct power to the motors. If I don't want to use the parallel port, then I will need to find a driver board that the arduino can talk to?

I am afraid to ask this next question, as it get a little bit off topic, but guess I will search to see if linuxcnc can even work with the arduino. Here is how I though the process went, and I now think is wrong:
draw in sketchup or inkscape->export to gcode->load gcode with linuxcnc->driver board

[doorknob]

Got it. I have a spare arduino laying around, so I can always try to use it as a type of "usb-adapter". I still need to find a better driver board that can supply the correct power to the motors. If I don't want to use the parallel port, then I will need to find a driver board that the arduino can talk to?

I am afraid to ask this next question, as it get a little bit off topic, but guess I will search to see if linuxcnc can even work with the arduino. Here is how I though the process went, and I now think is wrong:
draw in sketchup or inkscape->export to gcode->load gcode with linuxcnc->driver board

LinuxCNC does not run on an Arduino. Rather, it runs on a PC.

I believe that the Arduino code that takes G-code as input and sends step and direction output to stepper driver boards would be grbl (however I have not yet played with grbl - it is on my "do do someday" list). You would also need some kind of USB downloader software that would run on your PC and download the G-code to the Arduino (which is running grbl) - I am not sure what software people use for that, but it should be easy enough to find since there are a lot of people using grbl - maybe that code even comes along when you get grbl.

[scales11]

ok thanks.

So now that I understand what I was initially asking ,
1. I assume that detent torque is the absolute torque, making this motor, about 18.8 oz-in?
MyDIYCNC Stepper Motor | MyDIYCNC - Home of the DIY Desktop CNC Machine which
(2kg/cm = 179 oz - in holding torque, detent torque is 18.8oz)

2. Can anyone make a recommendation as to which driver board I should get to handle this 130oz stepper or the steppers mentioned above.

3. I also would just be interested in a simple, cheap but still sufficiently powered stepper/driver combo...bonus points if there is any documentation on connecting it to an arduino.

[doorknob]

ok thanks.

So now that I understand what I was initially asking ,
1. I assume that detent torque is the absolute torque, making this motor, about 18.8 oz-in?
MyDIYCNC Stepper Motor | MyDIYCNC - Home of the DIY Desktop CNC Machine which
(2kg/cm = 179 oz - in holding torque, detent torque is 18.8oz)

2. Can anyone make a recommendation as to which driver board I should get to handle this 130oz stepper or the steppers mentioned above.

3. I also would just be interested in a simple, cheap but still sufficiently powered stepper/driver combo...bonus points if there is any documentation on connecting it to an arduino.

Regardless of the torque specification, you probably don't want to use those motors, because the 32 mH winding inductance is extremely high, which will limit the amount of torque available at high speeds, if you can even drive them at high speeds at all (and will require a very high driver voltage). You would do better with motors with a winding inductance closer to 2 mH.

I do not normally see motors rated with both "detent torque" and "holding torque", and so I'm not sure that I could comment on that aspect. Perhaps the "detent torque" is the torque required to move the armature away from the natural detent that occurs in 200 places per revolution, with the power off, whereas the "holding torque" is the torque at the rated current when power is on. And so the actual torque that you would see when rotating the motor under load would be something less than the holding torque, depending on the speed of rotation (more torque at low speeds, loss of torque at increasing speeds). But maybe someone else could offer some comments.

Also, while I'm not certain, from the photos in the "Make Your Own DIY CNC" article, it appears that the author is using NEMA 23 size motors (physical size). The motor that you linked to is a NEMA 17 motor which is physically smaller, and so if you use one of those then you would expect to have to at least make different mounting holes for the motor. Also notice that the shaft size of that motor is a bit smaller than the typical shaft size used with NEMA 23 motors (although NEMA 23 motors may come with different shaft sizes as well).

[rinthesun]

Three solutions
1) Use the ST330 driver from SainSmart sold on Amazon for $17 each. You will also need a breakout board also available on Amazon for $23 Find a n older desk to computer with parallel port. Try Goodwill. Download LinuxCNC live DVD from their site. The ST330 will handle to 3 amp. motors. For motors try MPJA.com and get a 23.

2) If you want to use an Arduino and GRBL you will need g-code streamer software. Check this site out ShapeOko Build | zapmaker. To be able to handle 23 size motors you will need to use a driver like the ST330 so you will need to make a Arduino shield to connect to the drivers or a breakout.

3) Another choice would be to use the HobbyCNC driver and a set of unipolar 23 size motors. You will need LinuxCNC.

LinuxCNC does the g-code interpreting internally, but needs a parallel port. Since GRBL, a g-code interpreter, resides in the Arduino you can use a USB port, so a laptop or newer desktop will work. The disappearance of the parallel port is why GRBL was developed.

[scales11]

rinthesun,

Thanks for that clarification and those great links. MPJA.com almost seems too good to be true, great prices!

1. There are over a dozen NEMA-23s on MPJA.com, many with different voltages and rated torques. Any other requirements I should look for? Voltage has to match the driver board I get? I guess I could calculate the current draw too, which also depend on the driver board.

2. I did not find the ST330 driver on amazon that you were talking about...unless this is it.

3. I am most likely going to go with the NEMA-23s, as they seem to have enough power for me and are a popular choice.

4. It seems like I am unable to escape the need for a ST330. Just to clarify, if I use the arduino, the connection would be as follows:
arduino->stepper-shield(like this)->ST330-driver(or alike)->stepper motors
I did see this shield, does it negate the need for the stepper-driver-board?
I also read that this "stepper motor carrier driver" is required when using the reactive substance shield and the arduino...getting a bit confused on what is necessary after I plug the arduino into a stepper shield...

5. I know the TB6560 board would work well with a parallel port and linuxcnc, but I am unsure how I could connect the arduino to it.

[doorknob]

1. There are over a dozen NEMA-23s on MPJA.com, many with different voltages and rated torques. Any other requirements I should look for? Voltage has to match the driver board I get? I guess I could calculate the current draw too, which also depend on the driver board.

The torque, current, number of wires and inductance ratings are probably the most important. The voltage rating is less important, because you are probably going to end up using a current-limited driver that will supply a much higher voltage to the motor than the nameplate voltage.

[doorknob]

4. It seems like I am unable to escape the need for a ST330. Just to clarify, if I use the arduino, the connection would be as follows:
arduino->stepper-shield(like this)->ST330-driver(or alike)->stepper motors
I did see this shield, does it negate the need for the stepper-driver-board?
I also read that this "stepper motor carrier driver" is required when using the reactive substance shield and the arduino...getting a bit confused on what is necessary after I plug the arduino into a stepper shield...

5. I know the TB6560 board would work well with a parallel port and linuxcnc, but I am unsure how I could connect the arduino to it.

The grbl software turns the Arduino into a motion controller board that outputs step and direction signals for each axis on the Arduino board's GPIO pins.

Both the grblShield and the Reactive/Substance shield do pretty much the same thing, which is to take those output signals and supply them to the stepper motor drivers for each axis. In turn, the drivers send the high-power signals to the stepper motors. On the grblShield, the driver circuitry is soldered into place, while on the Reactive/Substance shield, you mount the Pololu driver boards onto the shield.

You could do the same thing with a multi-axis TB6560 board, but you would need to figure out a way to hook up that board's step, direction, and enable signal lines to the GPIO pins of the Arduino that are used by the grbl software. So, for example, you could get a prototype shield that would give you access to those pins, and wire up the connections from that board to the TB6560 board.

[rinthesun]

To use GRBL
1) Adafruit carries Arduino prototyping shields. Mount a 26pin IDC connector on the shield and wire it to the Arduino pins. Then make a ribbon cable 26 IDC to 25 pin DB (parallel port) connector. You will need a breakout board with the driver boards as pictured on Amazon.

2) or using the prototype board wire 3, 4 pin connectors (one for each ST330) to the Arduino pins. Now wire shield directly to the driver boards. You will also need a connector on the shield to attach the limit switches.

The GRBL shield you found has the stepper driver chips on the shield. These driver can work with a NEMA 17 but probably will have problems with a 23. Too much current needed.

The Amazon link contains the ST330 as a four axis package. Go to the SainSmart marketplace and scan the products and you will find the ST330 as single units.

Look, unless you only have USB available, drop the GRBL route and go with LinuxCNC and a mult axis board, such as ST330 set on Amazon or the HobbyCNC. Going with GRBL means you will need to build a shield.

1) LinuxCNC: CAD( the drawing) => CADCAM( creating g-code) => LinuxCNC(interpreting g-code) => CNC Router.

2) grbl:CAD( the drawing) => CADCAM( creating g-code) => g-code streamer software => grbl(interpreting g-code) => CNC Router.

See here ShapeOko Build | zapmaker for streamer software.

[scales11]

rinthesun,

Thanks for your honesty and reply. I do appreciate a little of advice on this since it obviously is the first time I have made one.

As you and DoorKnob pointed out, the trouble with grbl shields and the arduino is that neither hook up to a higher powered motor driver.

I was trying to keep my footprint small, and use a netbook to communicate with the CNC, but alas, I guess I will have to grab an older pc with a parallel port. I will post back if I stumble upon anything else.

[scales11]

This motor seems ok?
P/N: 57BYGH213
COIL: 6.2VDC/6.2Ohms/10mH
TYPE: 4 Phase Uni-Polar 6 lead
STEP ANGLE: 1.8 deg
New step motor, 9kg.cm holding torque. 6.35mm (.25") X 19mm (.75") steel shaft. 4 corner mtg. holes. 24" leads.
Compatable Driver: Order 17452-MS
L: 2-3/8" Body Sq: 2-3/16" WT: 1.6

should work fine with the TB6560 right? It is rated at 6.2V...but there are many others with many different voltages, aside from reading their torque, I just don't understand which I should choose...

I have read that people complain about this stepper board...have either of you heard the same?

[doorknob]

This motor seems ok?
P/N: 57BYGH213
COIL: 6.2VDC/6.2Ohms/10mH
TYPE: 4 Phase Uni-Polar 6 lead
STEP ANGLE: 1.8 deg
New step motor, 9kg.cm holding torque. 6.35mm (.25") X 19mm (.75") steel shaft. 4 corner mtg. holes. 24" leads.
Compatable Driver: Order 17452-MS
L: 2-3/8" Body Sq: 2-3/16" WT: 1.6

should work fine with the TB6560 right? It is rated at 6.2V...but there are many others with many different voltages, aside from reading their torque, I just don't understand which I should choose...

I have read that people complain about this stepper board...have either of you heard the same?

That is a 6-wire motor. The TB6560 board that you linked to is a "bipolar" driver which is designed to drive 4-wire motors. You could use it with a 6-wire motor, however you would need to choose which four wires to hook up - either a "full coil" hookup (which would probably not be a good idea because the inductance of the motor is relatively high), or a "half coil" hookup (which would probably work better with the TB6560 or other bipolar drivers, but not really well).

The TB6560 board has some problems - some people are successful using it but others are not - see http://www.cnczone.com/forums/genera...r_updated.html