Lathe speeds up when cutting

[kendo]

Hi Guys
Here's my problem, Hope someone can help. When ever i put a cut on, the lathe speeds up quite a bit. Even on cuts a small as 0.0050''.
The other day i was screw cutting a 12 TPI thread, when the lathe picked up speed and totally trashed my thread.
It doesent matter whether I'm cutting steel , brass or ally.
My Lathe is a Warco 280 VF.
Could this be worn bushes in the motor, I have only had the lathe 18 months and its not had a grate deal of use.


Thankyou in advance for any help or advise you guys can give.

Ken

 

[Ken I]

Speed up ? that's rather novel.

I don't know your particular machine but....

I presume this is a shunt wound DC motor. (ie the field winding and the armature are in paralell.)

Firstly check the applied voltage - is it rising - if so its a problem with the controller.

If the voltage is (more or less) constant check out the current - if its rising it might indicate that you have a burned field winding which draws more current as the short gets worse whilst at the same time weakening the field which will cause it to speed up.

If its a permanent magnet DC motor you might have a problem with cracked or loose magnets.

2c

Ken

 

[lensman57]

Hi Guys
Here's my problem, Hope someone can help. When ever i put a cut on, the lathe speeds up quite a bit. Even on cuts a small as 0.0050''.
The other day i was screw cutting a 12 TPI thread, when the lathe picked up speed and totally trashed my thread.
It doesent matter whether I'm cutting steel , brass or ally.
My Lathe is a Warco 280 VF.
Could this be worn bushes in the motor, I have only had the lathe 18 months and its not had a grate deal of use.


Thankyou in advance for any help or advise you guys can give.

Ken

You could certainly change the brushes if you wished to see if it cured the problem.
The alternative is to access the control board and adjust the Torque and speed pots, I would only attempt to do this if I knew exactly what I was doing as the problem as you describe could be in the feed back loop of the motor controller.

Regards,

A.G

 

[Don1966]

Do you have a speed control PC Board? If you do the settings are off. Remove the cover and check to see how many trim pots there are and if they are marked. The one you are looking for is labeled torque. Try to turn it CCW to lesson the Torque. This adjust can also be labeled I/R it is usually set at low speed to provide torque at low RPM. I would guess it is labeled torque.

Regards Don

 

[mu38&Bg#]

Yes, take a look at what Don mentioned. I've used KBC DC motor controls and they try to compensate for load by increasing the voltage to the motor to keep the speed constant.. There is a pot that controls this.

Greg

 

[Admiral_dk]

You have a problem with the variable speed controller - my guess is that it's overcompensating for load.

I haven't got any better suggestions than Don or Greg, but I would very much like to know how you do get it solved, since this is a lathe I very much consider buying myself.

 

[kendo]

Hi Guys
Sorry for being a bit late replying, I've been away for a couple of days. Great advise from all.

Don1966, the speed control board does have I/R next to a pot i will try adjusting this weekend will let you know how i get on.

I have tried phoning the warco company but keep getting, we are busy right now please leave a message after the tone, but they
have not got back as yet.

Once i have sorted this little problem, i will put a detailed post up with some photo's hope this might help others who might have the same
problem.
Once again thanks to all who replied you have been really helpfull.

Kendo

 

[moconnor]

Hello Kendo,

I had a similar issue with my Dremel Tool this week. After blowing out the carbon dust from brush wear, it was operating properly again. Maybe worth a try to just clean out the carbon dust? Can't hurt anyway. Hope you can find a solution to your problem quickly.

Kind regards,
Mike

 

[terryd]

Hi Guys
Sorry for being a bit late replying, I've been away for a couple of days. Great advise from all.

Don1966, the speed control board does have I/R next to a pot i will try adjusting this weekend will let you know how i get on.

I have tried phoning the warco company but keep getting, we are busy right now please leave a message after the tone, but they
have not got back as yet..................

Kendo

That's worrying, My WM280 VF has suffered a problem and I have been trying to contact Warco for 2 or 3 weeks and have had no reply to emails. Does anyone have any positive news recently from Warco?

Regards
Terry

 

[Don1966]

Kendo whenever you make any adjustment always mark the existing setting of the trim pot in case you want to return it to that postion. Try turning it back a forth to make it clean itself.

Mike has a point also. I do not know how old your lathe is, but if it is an older lathe carbon dust will effect some drives. I would do as Mike suggest and blow the motor out as much as possible. The carbon is not good for the motor or the drive. It causes ground currents and can distroyed the drive and motor.

Regards Don

 

[Springbok]

Thought I had heard of most things that can happen on a lathe but speeding up. Give Dave Warrens technical lads a ring they are usually very helpfull
Bob

 

[robcas631]

Hi Guys
Here's my problem, Hope someone can help. When ever i put a cut on, the lathe speeds up quite a bit. Even on cuts a small as 0.0050''.
The other day i was screw cutting a 12 TPI thread, when the lathe picked up speed and totally trashed my thread.
It doesent matter whether I'm cutting steel , brass or ally.
My Lathe is a Warco 280 VF.
Could this be worn bushes in the motor, I have only had the lathe 18 months and its not had a grate deal of use.


Thankyou in advance for any help or advise you guys can give.

Ken

Are you sure the gears are lubricated? Also, is the motor warm to touch when it speeds up?

 

[Springbok]

Hi have you tried talking to David Warren and the tech people there they are usually helpfull, though sounds like a board fault, I take it that as is a warco you are in the UK
Bob

 

[robcas631]

Bob,

I think it is wize to see issuses from all angles. I thought that your gears needed oiling or that you used you engine in one direction only. Clearly this is not the situation. So as my grandfather would say, " give them hell!"