Driving one axis with two stepper motors?

[stevesplanes]

In a 3-d mill, assuming the y-axis is the gantry, is it advisable to drive the x-axis with two stepper motors, one on either side of the gantry. My application is the x-axis is five feet, and two ball screws would be cost prohibative. A single central drive would cause problems in my application because my z axis work area is 24" and it cuts the plane of the x-y plane. If I drive from the central crew on the bottom, the gantry would have to be stiff and heavy, causing many other problems.

Has anyone driven one axis with two stepper motors?

[paulC]

The short answer is yes, you can run multiple steppers on one axis.
But I don't understand what you are trying to do. You are talking about a very big machine if its a mill. What material are you planning on milling? What accuracy do you need? There are options other than ball screws such as rack and pinion, belts or chains. You need to start by knowing what the expected result will be then designing to achieve that.
Paul

[R3D_EYE]

i ve playied around with 2 steppers on 1 axis before and it can work well
the trick is to power up a phase on each stepper and keep it live wile securing on to the axis
to my experience this is the best way to do this if you omit this step you will likely have the 2 steppers in a off phase position secured on the same axis thus fighting each other upon power up creating a lot of buzzing and no turning
i like this desing personally because i only know how to make simple drivers witch are limited in watts and this lets me split the watts between the 2 drivers needed for 2 steppers(as oppose to 1 big new expensive stepper and 1 big new expensive driver

if i recall corectly the phase you use to secure the 2 stepper onto the axis should be renamed phase 1 on each steppers
then procede with a backward sequence wirering for the oposite stepper
i hope for this to be of help

[unbwogable]

On a related question (NEWBIE ALERT!!)

I've got four smaller bipolar motors from two identical inkjet printers (two sets of two matching motors). Following my tendenacy to 'overbuild' everything I do, and seeing that these motors are probably not powerful to drive my machine theirselves, what would I have to consider if I used 4 screw drive systems (one in each corner of my X or Y axis), with 1 motor using a belt to drive 2 of the screws, and 2 motors total, all driving a carriage that is riding on some bearing wheels set in a track?

I've drawn an example



You would be seeing the unit from the end (either X or Y), the blue 'M' is the stepper, the red 'S' is the screw, and the black line is, of course, the belts driving the screws.

Or, would it be easier to use a gear-driven system in place of the wheels?

[paulC]

I suspect you are planning on using the screws alone as the guides for your axis. If this is correct you will proberbly be disapointed as there will be too much flex in the system. Have a good look around this site. There are a lot of people who have built on the cheap and you can learn a lot from their experiences. In particular look at the JRGO and JOE2000 builds.
Paul

[kamal Ismaelsso]

Originally Posted by stevesplanes In a 3-d mill, assuming the y-axis is the gantry, is it advisable to drive the x-axis with two stepper motors, one on either side of the gantry. My application is the x-axis is five feet, and two ball screws would be cost prohibative. A single central drive would cause problems in my application because my z axis work area is 24" and it cuts the plane of the x-y plane. If I drive from the central crew on the bottom, the gantry would have to be stiff and heavy, causing many other problems. Has anyone driven one axis with two stepper motors?

I have conected one axel with two step motors I send you conection diagarm.if you want.it depend of what kaind step motor you using.

[unbwogable]

Originally Posted by paulC I suspect you are planning on using the screws alone as the guides for your axis.

That's what I thought, so I changed my design a little. I've got two 1/4" hardened steel rods from the printers as well, and was planning to use those as an additional guide. Also, there would be wheels near the bottom (diagram) where it would ride, to support the weight, but also to guide. Any comments on that?

I'd hate to put all the work into it and have it fail...

Track diagram:
(red circles would indicate my track design - 'u'-channel aluminum, mortised into a wooden groove, with steel roller wheels riding inside)


CRISITICISM IS WELCOME, PLEASE!! I really want to make a sturdy design.

[Oldmanandhistoy]

Hi

I have used two stepper and two screws in one axis before (two drives wired to the same pins on the parallel port) with on problems.

I have a question on this comment.

Originally Posted by R3D_EYE i like this desing personally because i only know how to make simple drivers witch are limited in watts and this lets me split the watts between the 2 drivers needed for 2 steppers(as oppose to 1 big new expensive stepper and 1 big new expensive driver

Let’s say I am using two steppers @ 200 oz in each on my X axis. The question is will I have 400 oz in of force when I am cutting close to one side? I am no engineer but my instincts are telling me I will not and would probably be closer to say 250 oz in of force. Only while cutting in the centre will I have the full 400 oz in of force which would decrease as I moved ether side of the centre. I think of it this way; say I have a swing which is 10’ wide and I sit at one end, most of my weight is going to be supported by the chain nearest my sitting position, only when I am sitting in the middle would my weight be supported equally by both chains.

Is my thinking incorrect? If not then the best way to drive a system which required two screws would be to use one stepper motor driving both screws. That way the power would go where needed.

Your comments are welcome please put me right if I am getting this wrong.

John

[paulC]

Originally Posted by unbwogable That's what I thought, so I changed my design a little. I've got two 1/4" hardened steel rods from the printers as well, and was planning to use those as an additional guide. Also, there would be wheels near the bottom (diagram) where it would ride, to support the weight, but also to guide. Any comments on that? I'd hate to put all the work into it and have it fail... Track diagram: (red circles would indicate my track design - 'u'-channel aluminum, mortised into a wooden groove, with steel roller wheels riding inside) CRISITICISM, PLEASE!! I really want to make a sturdy design.

Please don't be put off by my criticism. I'm only hoping that it gets you thinking.
Bearings on aluminium will be subject to wear. U channels will quickly fill with dust. If the 4 threads are no longer quides why have so many.(each will have friction and alignment problems)
If you can tie the motion into what you need using bearings then why not use one screw with a belt around both steppers. Just be aware that you will have to adjust the possition of the steppers so that they are not fighting each other at rest.
Paul

[unbwogable]

Originally Posted by paulC Please don't be put off by my criticism. I'm only hoping that it gets you thinking. Bearings on aluminium will be subject to wear. U channels will quickly fill with dust. If the 4 threads are no longer quides why have so many.(each will have friction and alignment problems) If you can tie the motion into what you need using bearings then why not use one screw with a belt around both steppers. Just be aware that you will have to adjust the possition of the steppers so that they are not fighting each other at rest. Paul

I'm not put off by criticism at all, that's what I'm in the forums for! I want to design this is such a way that it will work with as little constant maintainence as possible.

I didn't consider the dust in the U channel. Perhaps replacing two of those drive screws with hardened steel rods, and using angled bearings? I assume that if I replaced the upper screws the dust would be minimal, and I could attached a small brush in front of each bearing if needed.

That would also allow me to have a more open plan, for wider stock.

Thanks for everyone's help!!

[harryn]

Hi, I have a related project crazy idea, and would like comments / criticisms as well. - Really, it is cheaper to get advice now than later.

The project is still coming together as an idea, but basically
- I have very little floor space in my garage
- I would like a lot of motion in one axis
- I am thinking of a mill / router which has a very long vertical axis - as in 4 + feet, but perhaps only 2 x 3 ft on the floor.

I prefer simple, so I can actually build it with minimal tooling.

I am thinking of mounting 4 of these

http://www.imshome.com/linear_slide_23.html

inside of a very stiff box frame for one axis. Obviously, I would need a longer than stock length for the vertical axis.

(so driving 4 stepper motors for one axis)

The box would be constructed from a double wall of the ALP stuff on sale at

http://www.panelteccorp.com/html/stockpanels.html

Yes, this is a bit off the deep end, I know.

Thanks

Harry

[paulC]

Originally Posted by harryn I am thinking of mounting 4 of these http://www.imshome.com/linear_slide_23.html

Real nice. Hope you have a good sized budget. Have you prices them out yet?
Paul