Problem- Broken Motor to BallScrew coupler

[IMK1230]

Hello,
The Y Axis Stepping Motor to BallScrew coupler has broken on my X2 mill!
Anyone know where I can get spares in the UK please?
Or is this a generic part that is generally available in the UK and does anyone know of a supplier please.

Thanks IK

[irving2008]

Try Zapp Automation or MarchantDice

Why not come visit the UK CNC Machinist community

[IMK1230]

Problem solution at Farnell's with Oldham couplers..
Very nice and much better than the originals
http://uk.farnell.com/huco/236p25-f/...pk4/dp/7002555
http://uk.farnell.com/huco/452p25-28...5x8/dp/7075870
http://uk.farnell.com/huco/452p25-24...1-4/dp/7075868

As always many thanks IK

[Crevice Reamer]

Oldham couplers may introduce more backlash than the original helical type.

CR.

[neilw20]

Have a look at the spec sheet.
I do not know what torque you are transmitting, but the 1" part has over 1/4 degree deflection / nm of torsional stiffness.
I could not see a spec for backlash, but it wont take much wear before there is significant backlash.
Even before microstepping, at approx 0.001" / step (1.8 degrees) at half the rated torque you must expect 0.0003". Lightly loaded this may be OK but these couplers will deflect more than a helical coupler.
You will get what you pay for.

After looking at some stepper specs expect over one degree at high torque !

[IMK1230]

Originally Posted by neilw20 Have a look at the spec sheet. I do not know what torque you are transmitting, but the 1" part has over 1/4 degree deflection / nm of torsional stiffness. I could not see a spec for backlash, but it wont take much wear before there is significant backlash. Even before microstepping, at approx 0.001" / step (1.8 degrees) at half the rated torque you must expect 0.0003". Lightly loaded this may be OK but these couplers will deflect more than a helical coupler. You will get what you pay for.

Then what type, make, model of coupler should I get for the X2 Syil mill?

[neilw20]

I googled helical coupler.
Inside first link is:
http://www.ruland.com/ps_couplings_flexible.asp
Available locally for you at RS components
Investigate available shaft sizes of coupler carefully before ordering.
I'm sure there are other less expensive options.

Extra comment:
philbur has a good point.
Also the original couplers were crudely made with a slitting saw and hence have sharp corners in the edges of each slot, making a great place for a fatigue fracture to begin. I must polish mine. I am surprised they have lasted 18 months!
I never did like them. As for alignment about the best you can do is have the supports for the stepper all loose, tighten the coupler so that motor is aligned as best possible, then tighten the motor mounts.
But you need a new coupler first.
Bellow couplers are really expensive, but have impressive performance figures.

Crevice Reamer. Another better coupler no doubt.

[philbur]

Nobody has commented that you should look for why the coupling broke. The coupling will have a limit as to the amount of misalignment it can handle. A fatigue break would be the most likely cause, and that looks like it could be one. It you don’t want to mess with alignment issues then you need a more flexible coupling. Look for specs on maximum allowable misalignment.

Phil

[Crevice Reamer]

You should definitely check the shaft alignment. Keling has some interesting helical couplers for sale cheap. I have not tried them, but his other products are first rate.

http://kelinginc.net/CNCPackage.html

CR.

[philbur]

Taking another look at the photo, if the setup has not been disturbed, it looks like the 2 coupling halfs have seperated, suggesting it was under considerable tension.

Phil

[sharpshooter90]

Originally Posted by philbur Taking another look at the photo, if the setup has not been disturbed, it looks like the 2 coupling halfs have seperated, suggesting it was under considerable tension. Phil

I agree- if the jam nut on the screw was loose, then the weight of the head would be hanging from the coupler. It may have not even shown up as backlash since the weight would keep thread contact all the time.

[Crevice Reamer]

Originally Posted by sharpshooter90 I agree- if the jam nut on the screw was loose, then the weight of the head would be hanging from the coupler. It may have not even shown up as backlash since the weight would keep thread contact all the time.

It's the Y axis coupler that's broken. What does the weight of the head have to do with it?

CR.