Need Help!- Stepper Motor help?

[robe_uk]

Hi All

My cnc build is continuing and I was planning to use the stepper motors I have used before.
My current build is using rack and pinion geared down 3-1 but when I tried to use the motors I have I was disappointed with how easily they stalled, turns out they are only 100 oz-in,
So now am thinking of getting stronger motors, ideally I would just buy the package from cncrouterparts which includes driver and motors etc and job done, But I don't have the $$$.

My current Drivers are PicStep bipolar drivers which can output 3A and run about 40-45v.

I was looking at these motors and considering running them in bipolar series mode which would allow the PicStep drivers to drive them, I think Bipolar parallel is the better mode to run but the amps would be to high.

Can I have your thoughts on these motors or suggestions

Thanks Rob

[hemsworthlad]

Hi rob,

Motors wired in series tend to run out of puff much sooner than parallel they also need lots more volts and 40-45 wont be enough so they will still be under performing.!

R&P tends to be less efficeint so you'll want the extra torque parallel gives.! depending on weight being shifted I'd also think about 34's they are much stronger and better suited to R&P IMO.

My advise is save up and buy new drives that will handle more A & V and go with 34's if large machine or heavy gantry.

Edit: Are you wiring the existing motors in series.?

[robe_uk]

HHmmmm I was afraid that might be my answer, I think I have the motor in parallel and get good torque when set at very slow feed rate but the torque drops very quickly.
I am reluctant to put to much more in the (hobby) machine for no real return, I had thought rack and pinion would be quite efficeint, it was cheaper to setup then ball screws and has less alignment issues, but I guess I should have done more research.
Any suggestions on motor/driver packages?

I have added a couple of pics of my build, cutting area about 1500x900mm. I plan to fill the box section with sand for damping at a later date.

Cheers Rob

[tkubic]

I am running a similarly sized machine using nema23 motors run in unipolar through 32(?) volts. In unipolar mode they are rated at something like 300 oz/in. My package came from hobbycnc. My machine is 4'x4' and I have a heavier gantry.

Check out:

• Hobbycnc.com
• xylotex.com
• kelling

My motors alone were 8 wire (able to run in any series) and they were $50 a piece. I can also jog at 1000 ipm, but I've reduced it to 500 since 1000 is scary as hell.

[robe_uk]

Gosh you wouldn't think it would be so hard to select motors
I see ger21 is using 220 oz-in motors at 24v and is happy with them, 23's are faster than 34's but 34's will have more grunt at lower rpm, am sure I don't need mega fast rapids due to the size of the machine..... Really don't want to get myself in a situation where i'll be buying twice

[robe_uk]

Ok, been doing a little reading, as hemsworthlad says series connection will run less rpm before stalling compared to parallel and also have less acceleration,
But at lower rpm will produce the rated torque, so with that in mind if am happy with reduced top speed these motor should be ok? right? 34 size motors look to be £££.
After all the cutting feeds can only be some much anyway?

More views and opinions welcome, thanks Lads

Rob

[tkubic]

Some good reading if you want to learn more about steppers: Stepperworld Tutorials

My machine runs 2 23's on the x-axis, and one on the y-axis. Stepper motors are extremely strong at low rpm, they lose torque as rpm increases.

Also I am a little confused as what is meant by series wiring? I know of Unipolar and Bipolar settings using different wiring configurations like 4,5,6 wire or something for bipolar and 6,7,8 or something for unipolar. Probably have that wrong, but I don't feel like thinking about it right now lol.

[TarHeelTom]

There might be an interim economy way to go. Set your Z axis up with screws of some sort. On many rigs the Z is the lightest weight of all the moving parts.

Then buy one hefty stepper now, and put it on either the Y, then use two of your existing motors to run your X axis.

Then, if you find you're really using the machine a lot, but another hefty stepper and put it on the X. Then later buy better drivers.

You can make the machine run with what you've got, albeit slower than you'd like. Make it run, use it, then decide if you really need more speed in all the axes.

Tom

[robe_uk]

Originally Posted by TarHeelTom There might be an interim economy way to go. Set your Z axis up with screws of some sort. On many rigs the Z is the lightest weight of all the moving parts. Then buy one hefty stepper now, and put it on either the Y, then use two of your existing motors to run your X axis. Then, if you find you're really using the machine a lot, but another hefty stepper and put it on the X. Then later buy better drivers. You can make the machine run with what you've got, albeit slower than you'd like. Make it run, use it, then decide if you really need more speed in all the axes. Tom

Hi Tom
Thats really good advice, I might get the steppers and use my PicStep drivers and see how we go...
I think I have more reading to do

[robe_uk]

Another question

would the above steppers work well with this driver at 50v in parallel mode?

Cheers Rob

[hemsworthlad]

Can't see the steppers you refer to but 4.2A & 50v will you run most nema23's in parallel with out any trouble.