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View Full Version : Stepper shaft couplings - can you ID these?



HankMcSpank
14-04-2012, 03:49 PM
Do these things exist to buy ready made or is this something you've got to knock up on a lathe yourself?

http://www.ukcnc.net/forums/showthread.php?84-Coil-Winding-Software-Advanced-Features&p=333&viewfull=1#post333 (post 19 top photo ....4th & 5th photo down you can see how it goes ontot eh stepper shaft.


I could rightly do with some of these with 8mm bores!

Lee Roberts
14-04-2012, 04:09 PM
Sorry not seen any available commercially...

Thinking you could just order some round bar (http://www.ebay.co.uk/itm/Aluminium-Round-Bar-Rod-25mm-Dia-x-250mm-Long-/160312604677?pt=UK_BOI_Metalworking_Milling_Weldin g_Metalworking_Supplies_ET&hash=item2553603805); get yourself a centre square (http://www.ebay.co.uk/itm/Small-Engineers-Centre-Square-/330515737683?pt=UK_Measuring_Tools_Levels&hash=item4cf445ec53) and bore them yourself reasonably well if you take your time.

Start off with a smaller drill bit, and then go for an 8mm should be able to get it fairly accurate without the need for a lathe?

.Me

JAZZCNC
14-04-2012, 04:17 PM
Do you mean the turned shaft collar holding the spinning bar on the DC motor or the slit connector on the stepper.?

The slit connectors are what you get from Chai (linearmotion bearings) or other Ebay vendors.

Lee Roberts
14-04-2012, 04:40 PM
4th & 5th photo down you can see how it goes ontot eh stepper shaft.

Think he means the coupler/couplings (http://www.ebay.co.uk/itm/3-flexible-coupler-coupling-6-35mm-8mm-/250586860620?pt=LH_DefaultDomain_0&hash=item3a58240c4c) I know someone who used these on a Rockcliff diy machine, can’t remember the full details but he used one of those couplers and it snapped along one of the slits with “not much force at all” as it was explained to me.

So not sure if they are any good or not, I would suggest going with a Jaw type coupler, L050 to be exact, work well sold 300+ of them not had any back (yet).

.Me

JAZZCNC
14-04-2012, 04:55 PM
Think he means the coupler/couplings (http://www.ebay.co.uk/itm/3-flexible-coupler-coupling-6-35mm-8mm-/250586860620?pt=LH_DefaultDomain_0&hash=item3a58240c4c) I know someone who used these on a Rockcliff diy machine, can’t remember the full details but he used one of those couplers and it snapped along one of the slits with “not much force at all” as it was explained to me.

Ye thats what I thought, they are ok really for the money. I had one on my Y axis for 2.5 yrs before it snapped and it had done some hard work, infact my Z axis has still got the original one on from when I bought the screws nearly 3-4 years ago now.

That said I do prefer the Jaw type my self for a few reasons but the ones I've experienced have been ok for the money and I wouldn't waste time trying to make them which I easily could.!

Edit: Hank if it's the other DC collar then I can machine them for you.

HankMcSpank
14-04-2012, 05:14 PM
It was this circled in red...

http://www.hostmyjpg.com/images/7186804c64_pic.jpg (http://www.hostmyjpg.com)

If they existed commercially (with 8mm bores to slide over my stepper shafts), then I'd likely grab a few ....I need to mount different types/varieties of backplates to a stepper shaft (for exploratory winding of coils, pickups etc).

if they don't exist commercially, then I have a big lump of cylindrical ali stock still left here, that I may commision one of you fine fellas to turn down for me (it would be like an elelphantitis version of the thing I circled in red!) ...I have previously made what I need (I'll take a photo later) but because I suck at anything to do with lathes (actually you could extend that out to anything to do with machinery in general!), it didn't turn out that accurate!

Lee Roberts
14-04-2012, 06:32 PM
So my initial interpretation was correct then, wasn’t too sure as you said “stepper shaft “.

I couldn’t do this for you as I don’t have a lathe, however could you not make some on your cnc machine?, you could clamp the stock up, do the bore, then fix using the bore, then do the profile work, shouldn’t be too hard to do?

.Me

JAZZCNC
14-04-2012, 06:48 PM
What diameter do you need them Hank.? and how many.? I can do them for you no prob thou I'm on the injured list at the minute.!
Got a piece of hot metal in my eye because was being Lazy and couldn't be bother to set bandsaw up to cut piece of flat bar and not slipping my grinding specs on for a quick 30 second cut.!! . . . Wazzak or what 30sec's going to cost me 3 days min.!!!!!:stupid: . . (Look like cross between Stevie wonder and capatain hook!)

HankMcSpank
14-04-2012, 07:15 PM
This is what I made myself ...

http://www.hostmyjpg.com/images/cdc1081679_0.jpg (http://www.hostmyjpg.com)


It took yonks with a hacksaw to hack throuygh the ali stock!!! (I think it's 100mm diameter)

http://www.hostmyjpg.com/images/f3c5254cdd_1.jpg (http://www.hostmyjpg.com)



And here the flip side...I make the blue plates on my CNC (and it's these blue plates that allow me to mount different winding options)

http://www.hostmyjpg.com/images/1563948005_2.jpg (http://www.hostmyjpg.com)


The diameter of the one I made was about 60mm ...but might want them a little wider (not much)


As it goes I'm in no rush ...as I already have what I have (might be nice to have a couple more though) it was only seeing that coupling that propmted this thread that picqued my interest

but my lathe is out of action (& like I say I sucked at making these anyway)

John S
14-04-2012, 10:29 PM
Jaw couplings are crap. They are designed for shafts that are out of line in one axis, not two axis as often happens in home built machines.
Any out of alignment takes up power to correct, run one at say 10 degrees out and see how hard it is to tun and what heat is generated.
now transpose this into two axis and that creates problems. Jaw couplings or Lovejoy couplings to give them their correct name are not designed for zero backlash, they might be well made but they are not guaranteed to be zero backlash.

The only type of drive that can handle miss-alignment in two axis is the Oldham coupling

Jonathan
14-04-2012, 11:18 PM
The only type of drive that can handle miss-alignment in two axis is the Oldham coupling

Looking at the specs Oldham couplings tolerate a surprisingly small amount of misalignment, not that that's a reason not to use them since you're doing something wrong if you can't get the shafts close enough...

Timing belts / pulleys are clearly the best solution for driving ballscrews... numerous reasons, but that's not really relevant here.

Hank, if you'd like me to make the part and can send me the drawing by tomorrow morning I should be able to fit it in. I've got plenty of aluminium bar, lots of sizes up to 3.5".

John S
14-04-2012, 11:53 PM
Looking at the specs Oldham couplings tolerate a surprisingly small amount of misalignment, not that that's a reason not to use them since you're doing something wrong if you can't get the shafts close enough...



Get your head out of theory spec sheets and into real life.

http://www.youtube.com/watch?v=utEKKox2WHA

True you should get them bang on, not close enough, 10 thou out is as bad as 100 thou out.

Jonathan
15-04-2012, 12:15 AM
Clearly the allowable misalignment is inversely proportional to the speed...as you said in the previous post misalignment absorbs power from the motor, in this case through friction. Since steppers are, relatively speaking, such low power motors this is obviously bad, even if the coupling does tolerate it in reality. I'm sure the manufacturers are conservative with the ratings. Hmm, I'm stating the obvious now, tend to make my own anyway.

This is much more interesting:

http://www.youtube.com/watch?v=G2DU1s2ukHQ&feature=endscreen

HankMcSpank
15-04-2012, 12:37 PM
Help, my "can you ID these couplings thread" has morphed into a fledgling technical debate" :-) (there must be something in the air around these parts?!)

Thanks for all the input...I guess the answer is "no, you can't buy 'em"...so when it comes to it, I'll have to get a better one made than the one I made myself......I'll limp on for now as it does work.

Thanks for the offers....I'll take one of you up on it when I get past my "make do" phase (which - using past history as a precedent - this phase will last far longer than it ought to)


Next question....where do you go to get a heap of 1.6mm thick mild steel in small rectangles made? (something like 4mm x 7mm x 1.6mm) ...I've looked in the local rag, but there's no "Small steel rectangle makers" in there!

Or if you were faced with having to make a few hundred....how would you approach it?

John S
15-04-2012, 01:27 PM
Have them laser cut.

HankMcSpank
15-04-2012, 02:26 PM
Have them laser cut.

Thanks - Is there a 'goto' laser cutter merchant that folks have used on here & can recommend?

Jonathan
15-04-2012, 02:53 PM
Thanks - Is there a 'goto' laser cutter merchant that folks have used on here & can recommend?

I've used 'True-Cut'. They were cheap at the time (few years ago) and the service was excellent...

http://www.truecut.co.uk/

ecat
15-04-2012, 04:46 PM
These guys, http://www.cncworkshop.co.uk/ , advertise on this very site (through AdSense at least)... for anyone who doesn't read the advertisements :wink-new:. They only do MDF in house, for metal they use http://www.essexlaser.co.uk/laser.html . The Essex bunch have 100 minimum order, boo, but I think that includes the cost of materials so for a large order they may be worth a try.