Bandsaw noise

[henton49er]

My bandsaw (Startrite 351E) runs well, cuts well, and does everything I expect from it .... except, when I switch the motor off, as the blade slows down, just before it comes to a halt, there is a pronounced metal-on-metal squeal. As my bandsaw knowledge is somewhat limited (could be written with a felt-tip marker on the back of a postage stamp), I am not sure where to look on the saw to identify the problem. I have checked for any accumulation of dust and removed all that I have found (very little). The blade guides look OK to me.

Any suggestions as to what might be the cause? Is it likely to need lubrication, and if so where and what type of oil?

Mike.

 

[loz]

Its the motor Brake.

 

[henton49er]

loz,

Does this model have a motor brake? It takes about 20-30 seconds to come to a stop after switching off and the screeching noise lasts for only the final 2-3 seconds.

Mike

 

[loz]

Hi Mike,

"It is equipped with cast iron wheels and electro-mechanical braking, "

http://www.startrite.co.uk/index.php?se ... ef=Bandsaw

Now that is the 352e but i'd assume similar for yours.

Regs

Loz

 

[OPJ]

How old is your machine? If it's new and doesn't stop within ten-seconds then, there's certainly something wrong. Would be worth contacting Startrite, if it's still under warranty.

On my 401e, the brake kicks only only after you release the stop button. If you continue to hold it down though, it delays the action of the braking and the blade and wheels gradually run down on their own.

 

[CHJ]

........ the blade slows down, just before it comes to a halt, there is a pronounced metal-on-metal squeal. .....

Does the Motor have a centrifugal starter switch? if so it could be something binding as it finally collapses.

 

[henton49er]

Chas,

I do not know what a centrifugal starter switch is, sorry. The on/off switch on the main column of the bandsaw is the standard NVR switch ... is that what you are referring to, or something in the motor housing itself?

Mike

 

[CHJ]

It's in the motor itself, some motors that are used in applications where a higher starting torque is required have a centrifugal switch mounted on the end of the rotor shaft (inside the motor frame). This connects a higher current starter winding in circuit when stationary and opens up when motor has spun up to disconnect the starter circuit when running normally
You can usually hear quite a loud click in the vicinity of the motor when starting if one is fitted.

 

[NetBlindPaul]

OPJ,
The operation as you describe it is not correct as once the e-stop is depressed it should stay in and the machine should stop within the alloted time.
How old is the machine please?
Is it CE marked?

CHJ,
The centrifugal switch is to switch out the starting winding which defines the direction of rotation of a single phase motor rather than provide higher starting torque.
The click is normally more audible on run down as the switch closes as the noise levels are reducing at this time.

 

[henton49er]

Olly / Paul - The machine dates from 2001 and I bought it privately in December last year. I doubt that there is any warranty!!

Chas - I cannot hear any click from the motor on start up. I have now timed the period it takes to stop once the off button is pushed - this is typically 12 seconds or so (my previous estimate of 20-30 seconds is obviously just my impatience to get on with things!!)

I am minded to remove the blade, clean everything up, reassemble and "tune" and see if that helps. Is there anything to be lubricated while I am doing this?

Another thought - I have the tension of the blade set to "high" (out of a choice of Low, Middle and High). The blade is 3/4" wide with what looks to be 4 tpi. Is this tension too high?

Thanks for your comments, gents, and sorry for asking such dumb questions. As a complete beginner it is good to know that I can get sound advice from professionals on this forum.

Mike.

 

[CHJ]

......CHJ,
The centrifugal switch is to switch out the starting winding which defines the direction of rotation of a single phase motor rather than provide higher starting torque.
...

Please note, my replies are often worded/pitched at a level I feel is consistent with my interpretation of the recipients knowledge.

Going off topic somewhat but all statements need qualifying:
The centrifugal switch does not always control direction of rotation on a machine, on one of my machines that is done by the configuration of the motor windings in the control box with an appropriate switch, the CS just disconnects the starter winding when the motor is up to speed.

I doubt very much that a cheaper/simpler permanently wired in start/run capacitor motor of the same nominal power rating would be able to get moving against the gearbox loads it would be presented with in this instance, and is the basis for my simplistic higher torque comment.

 

[CHJ]

.....Chas - I cannot hear any click from the motor on start up. I have now timed the period it takes to stop once the off button is pushed - this is typically 12 seconds or so (my previous estimate of 20-30 seconds is obviously just my impatience to get on with things!!)
.....

10 seconds always does seem a long time when you are waiting for a machine to stop, I know I was skeptical about my bandsaw meeting the requirement but I found that it does 'just' with most blades fitted. With the smallest of blades providing lower resistance and everything cleaned up and running freely it goes over 2 or 3 seconds more.

Are you sure that the noise is actually coming from the motor, place a long handled screw driver or piece of dowel against the motor housing as a sounding stick with your ear pressed against the handle or opposite end.

I have had a bandsaw wheel bearing that was seized and spinning on its shaft that only made an audible noise when the machine stopped, and it was not obvious which area it was emanating from.

 

[loz]

Mike,

Call Startrite on 01246 561 520 and ask them might be best idea

or you can register online and log a call, they will phone/email you back

http://www.startrite.co.uk/index.php?section=contact

Startrite Ltd.
Unit B
Adelphi Way
Ireland Industrial Estate
Staveley
Chesterfield
S43 3LS

 

[NetBlindPaul]

henton49,
IF you contact Startite, it may be me you get anyway as you may be in my area as you list your location as mid Wales, & I am in South Wales!
However, you should be able to narrow down where the noise is coming from yourself.
Try running the machine without the blade and see if the noise is still there and let us know, by all means give it a good clean first.
If the noise is still there, next job is drop the belts off and run the motor alone and check for the noise and let us know.

 

[NetBlindPaul]

chj,
I believe if the information I was taught when I did my C&G, my HNC, & my engineering degree is correct, that without a start winding/capacitor a single phase induction motor will not start.
The torque characteristices of the different winding configurations and capacitor combinations are different, yes, and cap start induction run is one of the higher torque variants, however, the difference between this type and the next highest tprque variant is negligible.
I do honestly believe that IF you investigate your machine you will find that the wiring and switch you have does as you say control the direction of the rotation, however if you draw out the equivalent circuit for the motor, and the connections etc between the L&N the capacitor the windings and the switch then study these you will begin to understand my point.
You will however, need to look at how the phase shift generated by the capcitor affects the start and run windings to understand how this works.
It is not easy to make a definitive calculation for phase shift, inductance, capacitance etc. as you do not have sufficient information on the motor plate, it is only the motor designer who will have this detail.
Well at least we did as a company when I worked for an employer who designed & manufactured their own motors!
Without this level of detail it is not possible to calculate the additonal torque specifically generated by the start winding.

This is a fundemental issue with squirrel cage induction motors, when on normal mains supplies, zero torque at zero rpm, we used to desing & build & sell ac motors with 100% torque at 0 rpm!

 

[CHJ]

chj,
I believe if the information I was taught when I did my C&G, my HNC, & my engineering degree is correct, that without a start winding/capacitor a single phase induction motor will not start.
...

Not disputed, but the direction of the curent flow in the start winding at a given point in time determines which way the motor will rotate, hence why my switch box crosses the connections to these over in relation to the stator windings.
As a matter of interest there are still several aircraft flying the skies with 60KW 3 phase 400hz alternator systems installed to my designs and drawings and they seem to work OK, so I do have a little knowledge of electronics and AC theory but don't always express things by the book.

A good refernce for Forum members is the document that 9fingers prepared:

http://homepage.ntlworld.com/bob.minchi ... Issue2.pdf

 

[henton49er]

Gents,

Thank you all for your help on this matter. After a few days being out of action on the workshop front, I have taken off the blade, cleaned everything out, reassembled and "tuned" the machine and used a slightly lower tension on the blade (somewhere between "medium" and "high" settings rather than the "high" that I had before). No more noise on power off.

Grateful for all your help. =D> =D> =D>

Mike

 

[CHJ]

I take it you weren't able to find the actual cause of the noise Mike, of no real consequence if the cause has now been removed/re-aligned what ever.

At least you know more about the mechanics of your machine than you did before. :lol: so not all wasted time.

Happy sawing.

 

[henton49er]

I take it you weren't able to find the actual cause of the noise Mike, of no real consequence if the cause has now been removed/re-aligned what ever.

At least you know more about the mechanics of your machine than you did before. :lol: so not all wasted time.

Happy sawing.

Chas,

No, no cause found, but I do wonder if I had the blade tension too high. Everyone seems to say better a bit too tight that a bit too loose. Maybe I had the tension much too tight!!!

Mike