Lathe Motor Speeding Up

[kendo]

Hi Guys
I'm hoping some of you folks might be able to point me in the right
direction.
I own a Warco Wm 280 VF lathe, and whenever a put put a cut on
the lathe speeds up by about 50 rpm when using the power feeds
thus increasing the speed of the feed.

It feels like the motor is hunting. So i rang Warco and spoke to a gentleman,
and he tells me its the rpm DRO, the little screen that tells you the rpm
and that its just a quirk of the machine something i just have to live with.

Well not really the answer i was looking for. So i asked could it be the
brushes in the motor are worn ( its only twelve months old ) and he told
me no he cannot see that being the problem.

It did not do this when i first got it, or is it something i just have to live
with.

Thankyou in advance for any advice you can give me.

My Best Regards
Ken

 

[LongRat]

This is caused by the load compensation circuit in the motor controller. When the current draw increases under load, the circuit tries to maintain RPM by slightly increasing the voltage to the motor - in your case it is over compensating slightly.
There will be some pots you can adjust inside the controller that will change this behaviour. If it is anything like the controller in my BF30 clone mill (like Warco WM18), which I am sure it will be, the controller in question is very similar to a KBIC unit. Google KBIC and you will find a lot of good information to help you to tune the controller to your needs. Be careful, there are some high voltages involved here and if mine is anything to go by, you may find some of the wires loose or some odd screws etc floating around near the circuit boards!
Good luck.

 

[kendo]

Hi Longrat
Thanks for your reply. Me not being too well up on electronics
i will get a friend to check this for me, as me and electrics don't
get on.
I kind of figure if i can't see it, smell it, or touch it, i ain't going
anywhere near it :big:
Will let you know how i get on, once again thankyou for your reply.

My Best Regards
Ken

 

[LongRat]

Glad to help, hope it gets sorted.
By the way, if you can see and touch it you are ok but if you can smell it you are too late ;D

If by any chance the controller fails on you I can strongly recommend getting a nice 3 phase motor and VFD to run it, you will have infinitely variable speed as now but much better durability and smoothness.

 

[Jasonb]

Its not a quirk, I've had mine for about 3 yrs now and the revs don't noticably alter when putting a cut on.

Only time that I had it hunting was when the brushes well one brush was worn and that was a few months back

 

[kendo]

Hi Longrat
Sounds like a great idea, fitting a 3 phase and vdf , i will certainly
bear that it mind if it does turn out to be the controller. Got a
friend coming over this weekend to check it out.

Hi Jason and thanks, i was hoping you might reply as i seem to
remember you having the same lathe as myself, glad to hear yours
is still running well, and continues to do so for many more
years.

My Very Best Regards
Ken