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FP2 Y-axis vertical power feed shaft repair

If I remember right, the keys for the sprocket and the pulley were in good condition.
The sprocket is pressed in axial direction and driven in one direction only. I suppose, that the sprocket wouldn't be a source for noise.

One or two slits in axial direction could be cut in the sprocket (red lines in the sketch). Then the sprocket can be "shrinked" with a slitted adjusting ring with a shape like this (green lines in the sketch):
Kunststoff-Stellring, geteilt, Innendurchmesser 30mm | eBay

ritzel.jpg

Karl
 
Have to change a previous statement i made regarding the fitting of "Polly-Vee" pulleys to my FP3....The drawings of the input shaft has (sort of) refreshed my memory on the work done.
In fact i did not use a taper lock hub on the driven pulley when I changed to the Polly-Vee style
Personally i think its a poor practice based on the overall design of the shaft and all its components.
The center bolt is what keeps everything from moving or rattling.....You really want to keep dynamic tension (center bolt torque) on the shaft assembly.
If the faces of all the stacked sleeves, pulleys and sprocket are flat and parallel and at right angles to the shaft axis, then making the center bolt tight will prevent movement of the stacked parts.
Of course the fits need to be good. All drives are one directional so if everything is pulled up tight there should be no motion once the key takes up in the powered direction....
Also should be noted that keeping the center bolt tight also has the added advantage of making the entire gear stack more rigid owing to having a greater overall diameter (sleeves etc).

Cheers Ross
 
95 mm taper lock pulley and 24mm bushing (these are for the motor) arrived today. Both are from Optibelt and look to be decent quality. Since I've never used taper lock parts before, out of curiosity I installed them on a 24mm grinding arbor mounted between centers. The arbor has no visible runout on a 0.01mm indicator. The pulley has between 0.03mm and 0.05mm of runout along the belt faces and radial features. Is that acceptable? I then mounted the pulley on the motor shaft (again, mounted between centers). Runout was similar, indicating that I won't improve matters by touching up the motor shaft.

What level of runout is acceptable on a motor pulley if I'm trying to reduce noise and vibration?
 
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Have to change a previous statement i made regarding the fitting of "Polly-Vee" pulleys to my FP3....The drawings of the input shaft has (sort of) refreshed my memory on the work done.
In fact i did not use a taper lock hub on the driven pulley when I changed to the Polly-Vee style
Personally i think its a poor practice based on the overall design of the shaft and all its components.
The center bolt is what keeps everything from moving or rattling.....You really want to keep dynamic tension (center bolt torque) on the shaft assembly.
If the faces of all the stacked sleeves, pulleys and sprocket are flat and parallel and at right angles to the shaft axis, then making the center bolt tight will prevent movement of the stacked parts.
Of course the fits need to be good. All drives are one directional so if everything is pulled up tight there should be no motion once the key takes up in the powered direction....
Also should be noted that keeping the center bolt tight also has the added advantage of making the entire gear stack more rigid owing to having a greater overall diameter (sleeves etc).

Cheers Ross


We were talking about a fix for a more or less worn shaft isn`t it
Peter
 
Yep....grind the shaft true, buy a pulley with a smaller bore, finish to the required size, assemble as with original parts with a proper torqued end bolt that applies constant dynamic tension on the shaft.
Could also (which i have done) turn the hub out of the current pulley and fabricate a new hub with flange that bolts to the pulley face with a center bore that fits a trued shaft....
Good news here is that the damaged part is really the final element on the shaft,so grinding the shaft slightly smaller poses no assembly problem...The hand wheel really does not figure in the repairs as
it really mounts via its face....
IMO the important design feature here is the need to apply and maintain constant compression to all the shaft elements.....otherwise you will have other parts of that shaft / gears allowed work loose.

Cheers Ross
 
Yep....grind the shaft true, buy a pulley with a smaller bore, finish to the required size, assemble as with original parts with a proper torqued end bolt that applies constant dynamic tension on the shaft.
Could also (which i have done) turn the hub out of the current pulley and fabricate a new hub with flange that bolts to the pulley face with a center bore that fits a trued shaft....
Good news here is that the damaged part is really the final element on the shaft,so grinding the shaft slightly smaller poses no assembly problem...The hand wheel really does not figure in the repairs as
it really mounts via its face....
IMO the important design feature here is the need to apply and maintain constant compression to all the shaft elements.....otherwise you will have other parts of that shaft / gears allowed work loose.

Cheers Ross


You discribe a total rebuild
I discribed a decent fix

With a rebuild and the shaft out I would crome the shaft and grind to original diam

IMO the important design feature here is the need to apply and maintain constant compression to all the shaft elements.....otherwise you will have other parts of that shaft / gears allowed work loose.

I agree But with a short bolt like that holds the handwheel you cannot get enough stretch to keep constant compression on it for years and years My experience is that this design feature is not that strong A simple setscrew on the key would improve things significantly

I had a simular issue once with a 4 year old OKK CNC machine ballscrew The screw had a fault at changing direction
Turned out the coupling to the servo had developped a bad key/keyway
Replaced the key and put a setscrew on Never heard about that problem anymore and that is more as 20 years ago Machine is still in use

Peter
 
I am going to reassemble with the taper thrust pulley on the motor shaft and see if that and the new rear bearing make everything quieter.

I checked the specs. It was hard to find run-out specs for the taper-lock pulleys, but eventually I found that for SPA V-belt pulley diameters < 100mm the allowed runout is 0.2mm both radially and on faces. So what I am observing (0.05mm) is well below spec.

I also found the shaft spec for taper lock bushing. For shaft diameters < 30mm the shaft tolerance range is h11, which is +0-0.130mm. So if needed I can grind the motor shaft down 0.08mm which would make it clean. But not clear that it's worth it, since I think most of the motor pulley runout is intrinsic, not due to the worn motor shaft.

Peter, if the machine is now quieter I will probably just add some setscrews over the key on the upper shaft (will tighten these AFTER the end bolt on the inching handle!) and see if those seem to be adding more noise/vibration. It it seems pretty quiet then I will stick with that.

Ross, I'll check that all of the mating end faces of the parts along the upper shaft are square and flat. If not that's an easy grinding job.
 
Machine is back together and running, but without the side and back covers, which I am going to paint those later this month. So I've added some temporary power wiring:

attachment.php


For Y-axis feed shaft repair I made this part, which clamps on to the undamaged part of the upper shaft, after which you add a taper pin. The idea is to locate the connector from the undamaged parts of the upper shaft, above and below the taper pin damage. This should also be easy to remove in case there is further damage in the future, just remove the two screws and cut the tube just above the bottom of the slit, then work the two halves apart:

attachment.php


It works nicely, here it is:

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and a last photo, showing that my part fits over the rear cover.

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The combination of the new rear bearing and taper-lock motor pulley have made the machine much quieter, so it was worth it!

PS: slightly off topic, but for painting purposes it would be nice to remove the on/off pushbutton switches from the operator-side cover. How are they held in? From behind I can see the threaded bodies of the switches, but no obvious way to remove them. I tried turning the switches from behind to see if they would "screw out" but stopped after it appeared that reasonable forces didn't turn them.
 
Great thread !

I think our machine in belt driven off the main motor ?
Yours appears to be chain drive, am I missing something here ?

On edit : Ah ok I think I get it, the pulleys were removed and this chain drive is
behind. I'll read the thread through properly and look at the machine prints
tomorrow.

( I think I see the upper pulley a few posts above, two belts right ? )

IMG_3171.jpg
 
I think our machine in belt driven off the main motor ? Yours appears to be chain drive, am I missing something here ?

I only have experience with a single machine, my 1964 FP2.

The motor drives a pair of identical V-belts. These run on a larger upper pulley, that drives the input shaft for the upper (spindle speed) gearbox. That input shaft also carries a chain gear. The chain transfers power down to the lower (feed) gearbox.

Another question for the group: the chain on my machine has quite a bit of slop. That's surely also a source of noise/vibration. Has anyone tried a Roll-Ring tensioner : ROLL-RING Kettenspanner & Zahnriemenspanner . Seems like a simple/easy way to keep the chain tensioned and (hopefully) quieter. Would it help here?
 
All those chains are loose
I used those things inthe past on a industrial application They worked pretty decent there
This is a special narrow chain however So I would be curious if you can find one
On this particulary application ithat device does not help to make the circomference on the lower sprocket bigger eighter
Perhaps there is space for a idler wheel?? Not to tight though

Peter
 
IIRC the 06B chain is only a bit wider So it fits the sprockets but a ring tensioner might be to wide
I do not have a chain right here so I cannot verify
But you can :)

Peter

On edit :
I have 2 sprockets for that top shaft laying around
One for a FP1 and one for a FP2 or 3
The sprocket for theFP1 is 3.5 mm wide The one for the FP2/3 is 5.3mm wide(That is 06B)
So perhaps/probably you have different chains on the different machines
Also from a pump I have here the sprocket is 3.5mm
 
Fit your own mechanical tensioner.....Does not even have to have a sprocket or teeth, for that matter doesn't even need to have a roller....lots of automotive
chain tensioners are simple smooth slick plastic like Teflon...that rub against the chain.
I would favor a simple spring loaded sprocket on the slack side of the chain if you think anything is needed.
Or if you want to make things quiet...can the chain and go for a cog belt.....
Cheers Ross
 
Hi Ross,

Or if you want to make things quiet...can the chain and go for a cog belt..

Yup, quiet is what I am after, and I'm afraid that a plastic-pad tensioner like you describe will make more noise, not less. But the cog belt idea has merit. Would that have to be wider than the chain to carry the same power? Not sure if there is enough space.

Cheers,
Bruce
 
Likely not strong enough in the space available....don't think a friction tensioner pad would make more noise unless its set too tight.
Maybe a scientific test to evaluate some different designs....:D
Now if we could just get that pesky end mill to run quietly ......maybe if the flutes were smooth .........
Cheers Ross
 








 
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