couplings - lovejoy vs disc vs zero backlash vs etc ?

[Jay-D9]

Hoping someone could guide me here in the right direction.

Running all Nema 34's 1/2 shaft 1200 oz/in

Twin screws on the gantry weighing in at over 100 lbs
singles on both Y and Z

1/2" 2- start acme rod

True alignment shouldn't be too much of an issue but first time for me so really don't know what the tolerances are.

Hobby machine so speed will be kept to and anticipation speeds. :-)

Any and all suggestions or question welcome.

Thanks in advance!!

Cheers - Jeff

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[coherent]

I've used lovejoys in some older projects and then tried the oldham style with a disc... much more accurate in my opinion and simply a better design. I eventually started making my own on my cnc mill using round aluminum stock and delrin for the disc. A pretty simple project especially considering the cost of these couplers. You say alignment isn't an issue but the oldham type couplers are also much more forgiving overall regarding alignment without sacrificing accuracy and providing minimum backlash. The gantry weight shouldn't be an issue.

[bill south]

coherent;
Would it be possible to post some pix of your home brew couplers? I'm going to be installing new motors in the near future!
Many Thanks.
Bill

[Jay-D9]

I wanna see to, :-)

looked up those couplers you mentioned and for the size and torque needed ---- wow you're right; looking at $350+. Can't afford those right now so will have to try a different route,

Budgets su*k!! lol

Thanks coherent

[A_Camera]

I've used lovejoys in some older projects and then tried the oldham style with a disc... much more accurate in my opinion and simply a better design. I eventually started making my own on my cnc mill using round aluminum stock and delrin for the disc. A pretty simple project especially considering the cost of these couplers. You say alignment isn't an issue but the oldham type couplers are also much more forgiving overall regarding alignment without sacrificing accuracy and providing minimum backlash. The gantry weight shouldn't be an issue.

This is a pretty good idea. I agree that those are easy to make once you have a working CNC, I might as well try it, even thought right now using lovejoy type.

[coherent]

I read folks have even made their own oldham couplers using a manual mill with no problems and others that made some using a 3d printer. I suppose you could make them with hand tools but I don't have that kind of patience. If the finished hub (or disc) fit is a bit tight some simple filing will get the size perfect.
The simplest way is to start with some aluminum and delrin round stock in whatever diameter you want. 3/4 in or 1 in is common and what I used. Cut your "blanks" to length. Then really all you have to do is center drill for your shaft size and mill the slots in the disc and the sides leaving the extrusion on the hubs. The male/female can be on either the hubs or disc, your preference. If you make a simple jig to hold the blanks in the same position it's even easier to repeat quickly. Drill and tap the hubs for set screws. These were made in inventor for 1" stock. Simple... not sure why they cost so much. It's no effort to change the shaft bore diameter or hub height to meet your specific coupler requirements

Aluminum Hub (2ea)


Delrin Disc

[RCaffin]

Grooves and slots need to be tight fits to avoid backlash.
You could also consider using a plastic which is just slightly softer than Delrin: UHMWPE could be worth considering. A little compliance might help - but with tight slots.

Cheers
Roger