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Cret
31-03-2014, 08:53 PM
Hi guys


I've got a bunch of Nema 23 steppers and am wondering if anyone can clarify if they'd be suitable for using to convert my machine to CNC. I know it's Nema 23 I need, but not certain of what spec I can use.


The labelling on them is:


kh56km2u004b
DC 1.6v 2.1A 1.8degree/step
AX050158A/G5641921
No 4Y01
Japan Servo Co Ltd


Was thinking about these drivers/breakout board, then obviously would need a suitable power supply too:
3 Axis DIY CNC Kit for Nema17 Nema23 Nema34 Motor TB6600HG Stepper Drivers 5A | eBay (http://www.ebay.com/itm/351033591753?ssPageName=STRK:MESINDXX:IT&_trksid=p3984.m1436.l2649)
Appreciate any advice on this as I'm new to the world of CNC but have these steppers that were given to me (with assorted other ones) and would like to use them if possible to keep costs as low as I can.


Thanks
Jim

JohnHaine
31-03-2014, 09:06 PM
My little Denford Novamill uses nema 23 steppers of about this rating on x and y but has a bigger nema 34 on Z. As the x3 is a significantly bigger mill I suspect the size 23 you have will be a bit underpowered for x and y and definitely for z!

JohnHaine
31-03-2014, 09:08 PM
Oops, sorry just realised you said x2! That might be better, really you need to measure what torque you need to turn the screws and make sure your motors can deliver it. Would need less if you fitted ball screws.

JohnHaine
31-03-2014, 09:11 PM
And I bought a similar set of drivers and BoB from eBay and it works just fine.

Cret
31-03-2014, 09:13 PM
Thanks - I've not managed to find the spec on these steppers yet unfortunately so it's hard to compare to builds others have done.

People seem to suggest anything from 270-425oz for the X2, but the lower end would be fine for me to get started since I got these free. I'd only ever be doing light work and speed doesn't bother me for now.

Definitely intending to change to ballscrews but can't afford to just now. So I was hoping to achieve a cheap but functional setup before hand, so that it'll be ready automated and a big improvement when the budget allows for ballscrews in future.

Cret
31-03-2014, 09:15 PM
And I bought a similar set of drivers and BoB from eBay and it works just fine.

Thanks John - tempted to buy this given the price. It states suitability for all Nema23 motors so it ought to be ok I think. Still need to source a suitable PSU thought. Hope they're not too costly!

irving2008
31-03-2014, 09:55 PM
you won't find the spec online as these are custom windings, probably for a plotter. They retail for 10Euro on a polish auction site so don't expect great things, they're likely to be fairly high inductance and relatively low torque, around 0.8 - 1Nm, or 112 - 140ozin. You'll get some movement but feedrates will be severely limited. Even then you'll need to be running them at 40v+

Cret
31-03-2014, 10:07 PM
Ahh, bugger. :(

Thanks for the info thought - better to know now. Presume I can't tell from testing impedance on the coils etc what sort of thing to expect?
Still, for the purpose of putting something together with a theoretically working machine they'll serve a purpose proving I have an appropriately PSU.

I think they are from a printer or plotter though as my friend said he got them from a place by the local scrapper where he dismantled them from that sort of thing.

JohnHaine
31-03-2014, 11:45 PM
Well as I said my Novamill uses small 23 steppers at about 1.5 amps on the table drive, so they could work even if you have to keep the speed down. And you can get bigger higher torque modern steppers which are also size 23 so will be a mechanical replacement if you want to upgrade. For a psu see eBay item 330989848125 which I think is the one I bought. 23 quid plus shipping. They also have other voltages.

JohnHaine
31-03-2014, 11:49 PM
Post a photo of the motors?

Cret
01-04-2014, 12:47 AM
Here you are:
http://i26.photobucket.com/albums/c113/Cret/9FD8D13E-4BAE-43E3-A982-0797DBC9EAE4_zpspqive50t.jpg

Straight through shafts as well (they're 6.3mm) so potentially can still have manual control.

They're 6 wire ones but as I understand you just omit the centre tap wires for each coil to use as normal 4 wire ones, depending what the controller/driver actually needs.
47mm between mount holes, which I understand is the normal pattern for Nema23.

irving2008
01-04-2014, 09:30 AM
6 wire explains why they'll be so poor. Designed for unipolar drivers. Yes you can run them on a bipolar driver by not using the centre connection but that's essentially bipolar serial which is the highest inductance, lowest performance.

The other point to note is those drivers will have to be set to 1.8A as the next setting is 2.5A and the steppers are rated at 2.1A. You might get away with the higher setting but they will get very hot. At 1.8A setting you've lost 15% of the little torque you had.

But give it a go, you can always replace them with proper steppers later. :)

Cret
01-04-2014, 09:47 AM
Thanks, that's useful info on the current settings. I think I've got fans that might fit on these in the same box but will check.

I don't mind replacing in due case as they were free, but useful for getting something assembled hopefully and testing on principal that the whole setup will work.

Does anyone happen to know if there is such a thing as free .stl files for mounting hardware?

Wushful thinking I suspect!

stirling
01-04-2014, 12:16 PM
If you ignore the centre taps then you'll be wiring them full-coil bipolar - this will double the resistance giving a rated current of just 1.05A.

You'll get more torque from these motors if you wire them half-coil bipolar. i.e. use the centre taps and ignore two end coil wires. Then the rated current will be the 2.1A stated.

deisel
01-04-2014, 01:28 PM
ive got a complete syil kit(electronics only) I may let go if you or anyones interested that's all the electronics plus the nema 34 for the z and the 2 nema 23 motors the electronics are in a makeshift control box(pc case) all wired up just requires the motors to be rigged up,the kit came off an x3 the specs can be seen here
https://docs.google.com/file/d/0B_5RZtQMhSzBSHFTdWwtUGxvVW8/edit

Cret
01-04-2014, 02:17 PM
Could be tempted potentially, thanks, but I'll look up the details and see what it all is.

Jonathan
01-04-2014, 02:22 PM
You'll get more torque from these motors if you wire them half-coil bipolar. i.e. use the centre taps and ignore two end coil wires. Then the rated current will be the 2.1A stated.

True at 'high' speed, but rated current through half the number of turns - so less flux which means less torque than bipolar using all the coils.

Useful summary here:
UniPolar vs BiPolar wiring schemes for 2-phase Stepper Motors (http://probotix.com/stepper_motors/unipolar_bipolar/)

irving2008
01-04-2014, 06:09 PM
If you ignore the centre taps then you'll be wiring them full-coil bipolar - this will double the resistance giving a rated current of just 1.05A.

Actually the current wired bipolar series is 0.7 * rated = 1.47A, so those drivers would need to be run at 1.2A, but the holding torque is 1.4 * rated.

So assuming they are 1Nm (141ozin) motors:
Bipolar 1/2 coil: Rated 2.1A, run at 1.8A, torque = 1.8/2.1Nm = 0.85Nm (120ozin)
Bipolar Series: Rated 1.47A, run at 1.2A, torque = 1.2/1.47 *1.4 = 1.14Nm (160ozin)

So run them Bipolar Series since you'll get low feed rates anyway due to leadscrew inertia and frictional load...

irving2008
01-04-2014, 06:16 PM
ive got a complete syil kit(electronics only) I may let go if you or anyones interested that's all the electronics plus the nema 34 for the z and the 2 nema 23 motors the electronics are in a makeshift control box(pc case) all wired up just requires the motors to be rigged up,the kit came off an x3 the specs can be seen here
https://docs.google.com/file/d/0B_5RZtQMhSzBSHFTdWwtUGxvVW8/edit
There's a big issue with those drivers - the current setting is not via switches but by twiddling a variable resistor while measuring the current in the windings. That's not easy to do without appropriate test equipment, a cheap digital multimeter on DC Amps setting will be wildly inaccurate as it cant sample fast enough

Jonathan
01-04-2014, 06:41 PM
There's a big issue with those drivers - the current setting is not via switches but by twiddling a variable resistor while measuring the current in the windings. That's not easy to do without appropriate test equipment, a cheap digital multimeter on DC Amps setting will be wildly inaccurate as it cant sample fast enough

One might be better off in that situation measuring the supply current and voltage to the driver, then since you (should) know the resistance of the motor at low speed, the required supply current can be estimated fairly accurately by considering the rated power. Adjust the potentiometer to get that current. The supply current should be measurable accurately using a cheap meter due to the filtering effect of the DC-bus capacitor.

stirling
01-04-2014, 07:59 PM
Jonathan - thanks for your "useful summary" link - good to see you're still your usual patronizing little self.

Irving - thanks for correcting my shoddy maths - however you just model holding torque - most people want their steppers to move - in which case your maths say nothing.

Cret - many years ago when some folks on here were still in short pants - all I had for my first machine were unipolars and I had them wired full coil bipolar. Mariss from Gecko drive (but hell what does he know?) suggested I try half coil instead and the difference was dramatic. Try both (it's allowed) - see which best suits your requirements.

Cret
01-04-2014, 09:17 PM
Thanks for all the input guys - as a newb to messing with steppers (aside from the experience with the 3D printer I've built recently) it's all informative, interesting, and useful. Please don't snipe at each other though - I appreciate all the different arguments and perspectives.

I will indeed meddle with it all but it'll likely be quite some time before I can assemble something anyway in all honesty due to the need to come up with hardware. If I fry these steppers in the process it'll be a shame but I won't be upset, as long as I don't take out any drivers in the process of course!

I think I have one or possibly two more of these steppers spare as well but I'd have to check.

I need to figure out I'd be better looking at those X3 bits on offer over the stuff on ebay but I'm not yet sure entirely about the pros & cons of both, relatively speaking.

And after that I need to figure out mounting hardware etc. I did have an idea that potentially I could fabricate temporary mounting hardware for the steppers using my 3D printer, just until the mill can machine its own ally stuff.
People probably scoff at the thought, but the printed plastic has an awful lot of strength and I'm sure would be capable of doing the job just fine. Nothing really to lose by trying anyway.

I'm not learned in making 3D designs though and have limited free time, so if I can find .stl files for the hardware it's a huge headstart.

irving2008
02-04-2014, 12:35 AM
Irving - thanks for correcting my shoddy maths - however you just model holding torque - most people want their steppers to move - in which case your maths say nothing.
On the contrary, if he's using the original leadscrews he'll need the higher low-speed torque just to get some motion. To a first approximation you get 70% of holding torque up to the corner speed. Agreed the corner speed will be higher with the lower inductance of the single coil, but that's moot if it stalls before it gets anywhere close.

But I agree, he should try it both ways, can't hurt.

Cret
02-04-2014, 01:34 AM
I wish I knew more about the maths of this stuff currently but it'll come in due course I'm sure.

In the meantime though, I think I spotted something of a bargain that might be perfect for what I need for the X2 to get started, with 3 options I'm pondering on. Yes I was going to try on the dirt cheap with the steppers I've got but these kits are cheaper than I thought, and viglink sent me a few Ł earlier today that helps so I'm thinking it may be best to just get a kit with all the bits needed from the outset.

I found this first kit for Ł110 inc 3x 270oz steppers, driver board, and PSU delivered.
The 270oz steppers should be ok from what I've seen but I'm not hugely keen on the single combined driver board & how good it'd be. Plus I don't know if 270 is enough for my Z axis. I do have an air ram fitted so I'm guessing so but still....
【Free SHIP】 3 Axis Nema23 Stepper Motor 270oz in 3A 4LEADS 3Axis Board CNC | eBay (http://www.ebay.com/itm/Free-ship-3-axis-nema23-Stepper-Motor-270oz-in-3A-4leads-3Axis-Board-CNC-/141108012690?pt=LH_DefaultDomain_0&hash=item20dab16692)

So more realistically there are these two:

3x 435oz steppers, 3x driver boards, breakout board & 2x PSUs - $299
【Germany SHIP】3 Axis NEMA 23 Stepper Motor 435oz in Single Shaft 4LEADS CNC | eBay (http://www.ebay.com/itm/Germany-Ship-3-Axis-Nema-23-Stepper-Motor-435oz-in-single-shaft-4leads-CNC-/141086226392?pt=LH_DefaultDomain_0&hash=item20d964f7d8)

3x 425oz steppers, 3x drivers, breakout board & psu - $319
【Promotion】3 Axis NEMA 23 Stepper Motor 425oz in 112mm 3A Driver DM542A CNC | eBay (http://www.ebay.com/itm/Promotion-3-axis-nema-23-stepper-motor-425oz-in-112MM-3A-driver-DM542A-CNC-/130995664275?pt=LH_DefaultDomain_0&hash=item1e7ff33593)

Wanted to do it cheap (in my nature) but these kits look great value and I'm thinking I should bite the bullet here.
What I'm curious about is why the kit with the higher power steppers (435 over 425oz) is cheaper and includes 2x PSUs instead of a single one in the dearer kit. Have I missed something?!

Appreciate comments on these - they look just the ticket and am VERY tempted, but don't want to be rash. Not too rash anyway...

Cret
02-04-2014, 01:35 AM
Yes by the way. I'm on original metric leadscrews in my X2. I do plan to change to ballscrews but might be quite some time before I can afford to. Probably one axis at a time from the one with most backlash first etc.

Jonathan
02-04-2014, 02:01 AM
I wish I knew more about the maths of this stuff currently but it'll come in due course I'm sure.

Have you spotted Irving's spreadsheet, here (https://www.google.com/url?q=http://www.mycncuk.com/forums/machine-building-faqs-problems-solutions/1524-what-size-stepper-motor-do-i-need.html&sa=U&ei=sFA7U_SqFYaO0AXavoCACQ&ved=0CAgQFjAB&client=internal-uds-cse&usg=AFQjCNFPShYDB4pTjpFj-rQyhrxGl6UdwQ)? If you want the maths, then there's I post I made about it a few years ago here (http://www.mycncuk.com/forums/general-discussion/3861-my-cnc-sessions-now-like-laundry-day.html#post25191).

In the meantime though, I think I spotted something of a bargain that might be perfect for what I need for the X2 to get started, with 3 options I'm pondering on. Yes I was going to try on the dirt cheap with the steppers I've got but these kits are cheaper than I thought, and viglink sent me a few Ł earlier today that helps so I'm thinking it may be best to just get a kit with all the bits needed from the outset.

Keep an eye on the inductance of the motors you're looking at - one of them is pretty reasonable. These motors from CNC4You have good specifications (I've measured them) and a good price, but I strongly advise you to try using Irving's spreadsheet (or my script here (http://www.mycncuk.com/forums/machine-building-faqs-problems-solutions/7355-what-size-servo-motor-do-i-need.html), with a few tweaks) to get a better estimate of what size motors you require. The slides and leadscrews on an X2 will exhibit quite a lot of friction (compared to linear guides and ballscrews), so if comparing with other milling machine conversions bear in mind that you'll need bigger motors (to get the same feedrate) if you decide not to use ballscrews.

Cret
02-04-2014, 08:45 AM
Thanks Jonathan

I will have a look at those to see what the requirement is etc and if these suit.
I definitely want ballscrews though, and it may be the case that by the time I get it assembled and figure out the electronic/software setup etc that I already have them or have got the money together so it shouldn't be too much of an issue, just that if I'm not quite at that point I might have to be a bit wary perhaps of using anything?

irving2008
02-04-2014, 01:45 PM
I wish I knew more about the maths of this stuff currently but it'll come in due course I'm sure.

In the meantime though, I think I spotted something of a bargain that might be perfect for what I need for the X2 to get started, with 3 options I'm pondering on. Yes I was going to try on the dirt cheap with the steppers I've got but these kits are cheaper than I thought, and viglink sent me a few Ł earlier today that helps so I'm thinking it may be best to just get a kit with all the bits needed from the outset.

I found this first kit for Ł110 inc 3x 270oz steppers, driver board, and PSU delivered.
The 270oz steppers should be ok from what I've seen but I'm not hugely keen on the single combined driver board & how good it'd be. Plus I don't know if 270 is enough for my Z axis. I do have an air ram fitted so I'm guessing so but still....
【Free SHIP】 3 Axis Nema23 Stepper Motor 270oz in 3A 4LEADS 3Axis Board CNC | eBay (http://www.ebay.com/itm/Free-ship-3-axis-nema23-Stepper-Motor-270oz-in-3A-4leads-3Axis-Board-CNC-/141108012690?pt=LH_DefaultDomain_0&hash=item20dab16692)

So more realistically there are these two:

3x 435oz steppers, 3x driver boards, breakout board & 2x PSUs - $299
【Germany SHIP】3 Axis NEMA 23 Stepper Motor 435oz in Single Shaft 4LEADS CNC | eBay (http://www.ebay.com/itm/Germany-Ship-3-Axis-Nema-23-Stepper-Motor-435oz-in-single-shaft-4leads-CNC-/141086226392?pt=LH_DefaultDomain_0&hash=item20d964f7d8)

3x 425oz steppers, 3x drivers, breakout board & psu - $319
【Promotion】3 Axis NEMA 23 Stepper Motor 425oz in 112mm 3A Driver DM542A CNC | eBay (http://www.ebay.com/itm/Promotion-3-axis-nema-23-stepper-motor-425oz-in-112MM-3A-driver-DM542A-CNC-/130995664275?pt=LH_DefaultDomain_0&hash=item1e7ff33593)

Wanted to do it cheap (in my nature) but these kits look great value and I'm thinking I should bite the bullet here.
What I'm curious about is why the kit with the higher power steppers (435 over 425oz) is cheaper and includes 2x PSUs instead of a single one in the dearer kit. Have I missed something?!

Appreciate comments on these - they look just the ticket and am VERY tempted, but don't want to be rash. Not too rash anyway...


Don't touch last one, 9mH motors are not great, needs to run on 80v+ drivers.
First one is poor, single board and only 24v

Second one is best of bunch, uses reasonable steppers @3.8mH, but these ideally want 4.2A and the drives only give 3A RMS, 4.2A peak. Also PSU is only 36v. Not sure how you use 2 psu across 3 drives; you can parallel up PSUs, but not generally a good idea.

Cret
02-04-2014, 08:34 PM
Ok that's more great info and I'm learning from this stuff thanks! Great to have this assistance in avoiding some of the packages I might end up regretting.

I might message the seller and ask about the PSU thing.

In respect of the drivers and the current they can output & the rating of the motors, do the motors only pull the full rating when a load on them demands that? Or do they somehow draw that constantly? I'm not quite sure how that works sorry.

Be nice if there's a package at a sensible price that suits the X2 specifically so I'll look a bit further but may potentially come back to this second one. Maybe.

Cret
02-04-2014, 09:41 PM
On another note - looks like someone already started doing 3D printer produced stepper mounts:
Stepper Motor Mount Nema23 for Homemade CNC Router | eBay (http://www.ebay.com/itm/STEPPER-MOTOR-MOUNT-NEMA23-FOR-HOMEMADE-CNC-ROUTER-/160379861560?pt=LH_DefaultDomain_210&hash=item2557627a38)

So will see if I can find design files somewhere....

irving2008
03-04-2014, 12:41 AM
....

In respect of the drivers and the current they can output & the rating of the motors, do the motors only pull the full rating when a load on them demands that? Or do they somehow draw that constantly? I'm not quite sure how that works sorry.
.

As a general rule the power supply should be rated at 60% of total peak current, so 60% of 3 x 4.2A = 7.6A

Switch mode power supplies are not best for CNC work, linear supplies handle the peaky nature of steppers better and are easy to build.

Jonathan
03-04-2014, 07:19 PM
On another note - looks like someone already started doing 3D printer produced stepper mounts:
Stepper Motor Mount Nema23 for Homemade CNC Router | eBay (http://www.ebay.com/itm/STEPPER-MOTOR-MOUNT-NEMA23-FOR-HOMEMADE-CNC-ROUTER-/160379861560?pt=LH_DefaultDomain_210&hash=item2557627a38)

So will see if I can find design files somewhere....

Flimsy. You have a milling machine - use it.