Fadal spindle belt shrinkage! have you guys seen it?

[pbrokaw]

Hello folks:

We have had 4 belts now that have "shrunk"!!!
Installed 2 on a 6030,24 hours later the low range had locked up be it was too tight to turn even with the idlers swung out of the way!
Same thing happened with a 4020 machine.
Belts were from CNC Pros out of ID.
No oil contamination or anything like that.

Any ideas ?

Perry

[AKELLEY]

Perry,

It sounds like motor tensioners problems or bad motor mounts.
We have three fadals never had belt problems.

[mad mark]

Replaced belts on several different machines, from several different sources. Never seen or heard of this. Are you sure it's the belts???

Mark

[pbrokaw]

Yes it is the belts.The motor mounts are fine,no rubber squeeze out at all.what is more interesting is the belt that shrinks is usually the low range belt,while the machine is running in high range.So there is no tension on the low range!The belt tensioners are good too.Just installed new bearings in the high and low idlers wheels.And yes,I did reassemble them correctly...

Perry

[B_Bueno]

I'm a day away from replacing my belts, I got the pre-shrunk ones [like my jeans] !
I didn't get the stone-wash ones though, can't see them behind the cover. . . .!

[CNCDesk]

I've been using Fadals for over 10 years and have installed countless belts. I've never experianced a belt shrinkage problem.
I have had belts that have the appearance of shrinkage but actually they have expanded. This has always happened when the Thru-Tool Coolant Seal has gone bad. The only visual that this has happened is by looking directly on top of the seal and you will see some coolant there. The belts may look perfectly fine. Usually when you have this problem it is an audiable thing. It sounds almost like gear teeth grinding or a metallic rattleing but it isn't metallic...it's the belt sqeaking inside the tight toleranced groove inside the Belt Cover that holds the belt in place.
If it isn't from the thru-tool coolant seal going bad then you need to buy your Belts from FADAL or the Sales Rep that sold you the machine.

[Delw]

CNCdesk Thanks for the confirmation of the noise.


I have the grinding problem now but only in high speed. its defiantly in the belts as when the cover is off you can see the top belt try to spin when the high speed belt is engaged. squeaky prick to until it catches and spins

a few weeks ago it made a noise like described, trying to find the problem I changed from high to low gear and it went away. so I continued to run, no problems till last wednesday I started leaking air out of a tensioner cylinder. I order the cylinder went and started the machine and the problem is still there.
replaced cylinder problem still exist but I am not leaking oil or air now.
low speed works fine high speed gives me the noise.

I am guessing I need to replace belts also????

[pbrokaw]

Our machines do not have thu-spindle coolant,so it is not that.The belts we get from CNC pros are Fadal's OEM belts.and yes,the belts do shrink,I have seen it twice now firsthand.And the maint shop boss has seen it also.I have worked on maint of Fadals for 15 years and I am puzzeled on this one.Fadal in CA is clueless,except or course to sell us more parts.

Perry

[Delw]

There is no adjustment for the belts other than the tensioners.
so if the tensioners are not engaged and your belts are still tight.
check to make sure everything is clean.
the pulleys make sure the grooves are free of nicks and dirt also
the black belt housings
if its still tight have you ever replaced either pulley? if you did was it a OEM part or an after market part?
are the pulleys loose or not aligned right? you cen tell if the belt it running true in the grooves by just hand spinning the spindle. ( could be one pulley is higher than the other).
now if all that checks out then your belts are the wrong size its pretty much that simple.
I've been in the business a really ong time both for machine tools and packaging machinery. I have never seen a belt shrink. I have seen them swell but never shrink.

Also the belts can swell with out through spindle coolant just by the mist,

one other thing to check is if you have the ar over hydraulic type tensioners has it been leaking? this will cause the bets to swell also.

[pbrokaw]

Delw:
Pulleys are clean,no misaligment of the sheaves.The hydralics of the tensioners are fine...The shrunken belts he have taken off are clean and dry.The belt guides are fine also.I have changed belts on Fadals probably at least forty times!We have 10 Fadals,4 Makinos,one DMG,one Leadwell,and one Bridgeport.In short everthing is done right to spec.We have not had this problem for some time now.The machine has run for 30 hours since belt change out. I think it was just a fluke,but it still does not make any sense...