LinkBack URL
About LinkBacks
.25" IS 1/4"! The question is are the drivfe journals on your leadscrews 8mm?
| | |
Hi,
I've been quoted a price for linear rails and ballscrews with machined ends. The couples are 3pcs of flexible couplings 6.35mm*8mm.
Is flexible better than solid couplers?
Page Title
Any suggestions?
newpatch
Last edited by newpatch; 03-20-2012 at 06:59 PM.
.25" IS 1/4"! The question is are the drivfe journals on your leadscrews 8mm?
Yeah, 6.35mm is 1/4"..I worded the question wrong...(I reworded then thread)
I should have asked if flexible couplings work better better than solid shaft ones....I've seen rubber tubing used also.
I'm assuming the flex in the coupling protects and dampens shock to the motor...
newpatch
That's pne reason. The other reason for flex couplings is that it compensates for any shaft misalignment; solid coupling would work if your motor shaft was 100% perfectly aligned with the drive jounal (or screw, though I'd probably not reccomend directly attaching screw to motor without a proper bearing block). Otherwise could lead to premature wear on your motor bearings; at the very least it would add some unneccesary friction to your system...Originally Posted by newpatch
There has been a few examples here of snapped motor shafts when solid coupling is used due to radial miss-alignment.
Al.
CNC, Mechatronics Integration and Custom Machine Design (Skype Avail).
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.
I would recommend a flexible. The reason is, even if your motor is very accurately aligned, it is physically impossible for it to be perfect. When you start rotating the assembly it is going to strain the shaft with every turn. I had a rigid coupler on my Y axis for a long time, and no matter how many set screws I used, how tight I cinched it down, and even resorted to putting in a key way it would still come loose. I ruined several work pieces due to this.
Replaced with a helical coupler, have not even looked at it since. Same setup, but no problems yet after a year or so of heavy use.
Yes.
http://www.kirkcon.com/
Shaft misalignment will overload bearings, ruin motors, and reduce torque delivery due to it fighting the misalignment. Coupling capable of parallel misalignment should be used when trying to deliver torque from one shaft to another where both are rigidly fixed.
Helical couplers suck, everybody still uses them though. Their torsional stiffness is poor, which is the biggest reason they are a bad choice, there are a couple others but a little more difficult to explain.
I suggest using Oldham style coupling, very popular over on the benchtop mill cnc side, they are cheap, and allow for massive misalignment. Below is a link:
McMaster-Carr
I started out with the common LoveJoy L series couplers, but they actually have a bit of play in them which shows up as backlash. I had switched (at LoveJoy's advice) to their GS curved-jaw couplers with a rather hard spider, and have been doing well with it since. The difference is like night and day.
I really like the helical couplers, Ive used them on a couple of machines, with servos and steppers.. Ive never had an issues with backlash.
Just be sure to get a good quality helical couplers if you go that route.. I use the stainless steel ones made for servo motors.
backlash isn't a problem at all. backlash refers typically to the "slop" or amount of play before engaging the coupler when reversing direction. Windup is how much the coupler deflects under load. For positioning applications helical couplers are bad due to their windup or high amount of deflection under load.
Posting Permissions
| | |
