On Mon, 04 Feb 2008 17:57:44 -0500, Fred warydragon--at--gmail.com
wrote:

Richard Edwards wrote:
On Sat, 02 Feb 2008 18:23:05 -0500, Fred warydragon--at--gmail.com
wrote:

My Clausing 12x37 clone will not run backwards

Today, my Clausing 12x37 clone metal lathe has stopped turning off with the lever switch on the apron. I can switch
from forward to neutral to reverse and hear relays at the front lever switch work each time but it keeps running
forward. If I want to stop it I have to hit the emergency button. This is at least aggravating. But, I can get stuff
done as long as I don't need it to run backwards.

My problem right now is I'm all set up to run backwards for a threading operation that I don't feel comfortable running
forward. The lathe will only go forward and starts right up with the apron lever in the neutral position when the start
button is pressed. It still will not start in the forward and reverse apron lever position, as it's not supposed to.
But if it's in the apron neutral position it will start running forward when the start button is pushed. Cutting power
to the lathe does not effect this behavior when reconnected.

There are several multi wire relays in the panel box on the back and I suspect one of them is the problem, or the switch
in the front controlled by the apron lever. The motor is 220 single phase.

It has happened before and not really been a problem. The next time I used it it would act normally for a while. And,
maybe I can let the thing cool down and get these threads cut later tonight or tomorrow. But, I need to eventually fix
the problem.

I do not know how to diagnose how to fix this. Any suggestions on what I should do?

Thanks,

Fred
Take a look at your "inching button" it could well be stuck in or have
welded contacts. The "Heating Relay" comprises a set of resistance
wire single layer coils wrapped around bi-metallic strips. These wires
carry the motor current which if excessive will cause heating and
therefore bending of the bi-metallic strip. The bending action on any
or all of the strips opens a contact which will cause the main
contactor to drop out (FR contact in the KM1 coil line)

--

Richard

Email address is valid but remove burrs before sending!
I'd rather not pay someone else to fix it if I can do it myself. I have
done some electrical work, like wire everything in my shop, but of
course I do not want to trash my lathe.

I don't think it's the "inching button" as it works normally when the
lathe is working normally.

Thanks for the info on the "Heating Relay".

I worked the lathe today and sometimes it would start in neutral and
sometimes not. An irregular times, sometimes a few seconds and sometime
many minutes, after I cut off the machine I hear a relay resetting in
the power box. After I hear that click, the lathe will start normally.

How do I tell which relay is malfunctioning, if in fact that is what is
happening?

Thanks,

Fred
Ok thats a bit more information.
The circuit diagram shows that K1 is the Main contactor K2 the forward
contactor and K3 the reverse contactor. Based on your comments it
would appear that SA (Selector switch) is operated by your Fwd/Rev
lever. Everything points to K2 staying in. There is an interlock
between K2 and K3 so that they cannot operate together and generate
magic smoke! From the photo of the panel it appears that this is only
an electrical interlock not mechanical.
Run the machine whilst it is in error and take a look at K2 this is
most probably the contactor that is staying in. You will be able to
see if it is in or out by looking at the black button left centre of
the labelled face of the contactor. Probe with a meter (you will be
reading 36v AC) at terminal 2 on the bottom terminal strip to terminal
0 on the transformer. When running Fwd you will see volts here. You
are hopefully monitoring the volts across K2 coil.

Options after lever to forward then neutral but machine continues to
run are ----
1 K2 "IN" and volts present - Selector switch sticking or Jog button
sticking
2 K2 stays "IN" but volts go away - Contactor sticking mechanically

Re-reading your post I now think that K2 is sticking mechanically.
Before you do the above try this.
Turn OFF all power to the machine. Manually press the aforementioned
button on each contactor and compare their responses. If K2 drops out
slower or sticks that is your problem. This is not the finest test as
your press acts in a different way to the coil pull in.
When replacing it you do not need the same manufacturer just
physically the same size, coil voltage and current capacity. The
positions of the coil connections may change maker to maker. Ensure
that you mark all wires as you strip, and make notes.
By the way did I tell you to TURN OFF ALL THE POWER TO THE MACHINE
FIRST! (and preferably pull the main fuses and keep them by you.)


Rectify and continue to make swarf!

If you are at all concerned with your abilities GET AN ELECTRICIAN!

--

Richard

Email address is valid but remove burrs before sending!