Enco lathe won't turn off.

[trainman2]

I have a problem with an Enco 12/36 model 110-2031 built 1991 serial 4257 bench lathe where there is a delay in the machine stopping when is turned off from the apron.
It can take several minutes to go off and the emergency stop also will not turn it off. Reverse works fine, emergency stop also works when in reverse. It has been like this since new and at times it works fine. The fact the emergency stop does not work really puzzles me.
I tried metering the apron switches they seem to be OK the stop button also seems to be OK. I had someone look at it that Enco recommended to no avail.
Has anyone had a problem like this or suggest where to look.. The EPO switch has to be a clue to what is wrong, but I cannot figure it out.
The device with a white knob I assume is an overload protection. Below that is a small relay I call the control relay. One leg has what appears to have a diode on it.

 

[Mr Mike]

Im going to guess bad or stuck relay..!
The fact that your emergency button stops the machine in reverse but not forward leads me to think a relay is staying engaged when power is removed from the circuit but the machine stays running.

If your machine is inspect-able at the rear you can sometime Visually "depending on the relay" see to confirm if one of the power relays is bad / stuck or still energized you can also check this by unplugging the machine when it happens and see if it start back up on its own, which may happen with a relay that is stuck closed after being de-energized.

 

[trainman2]

Im going to guess bad or stuck relay..!
The fact that your emergency button stops the machine in reverse but not forward leads me to think a relay is staying engaged when power is removed from the circuit but stays running.

If the control relay was sticking, would it also have a problem when in reverse?

 

[Mr Mike]

Think of it like a single pull double throw switch, it can get stuck in one position but works fine in the other, if there are two relays. one for forward one for reverse it can happen..! My Emco 12x36 had 3 relays...

From what you describe a bad relay is my hunch, but without being there to view and test, I can only try to give you optional places to check... your Emergency switch sounds like it kills power to a low voltage relay that energizes a high power relay, when you hit the switch it de-energizes the low power relay, but if the high power relay is stuck closed it will still supply power to the motor, Not a true kill switch.

does the power light go off when you hit emergency stop...?

Hope you find the issue and report back your success.

 

[Dhal22]

Unplug it........

 

[matthewsx]

This is a serious problem, but you should be able to fix it with a little detective work. I’d find a helper who can work the controls while you watch the relays. The fact it’s done this since new might mean it was wired incorrectly to begin with.

Get a wiring diagram and identify the major parts and start checking with a multimeter. Make sure all connections are going to the right place and are energized at the right times, check for shorts too.

Alternatively, you could do like I did with my Samson (Tida 5aa) which is the same machine and install a three phase motor with VFD. You won’t regret it, trust me, and you can do all kinds of cool things besides having variable speed.

Here’s mine:

Samson (Tida) TD-5AA lathe

Just picked this up today. And.... So I can check it against what Mr. Fang found in 1981 :grin: John

www.hobby-machinist.com

John

 

[tq60]

You have a sticky contactor on forward side.

If plug in swap them.

If hard wired you can determine the CONTROL wire and disconnect it, then use a clip lead or just hold it in place, start the lathe then lift it.

If it does not release when lifted the thete is the issue.

Many can be opened and cleaned.

Sent from my SM-G781V using Tapatalk

 

[markba633csi]

It's the forward contactor that's sticking. Not sure where you can buy replacements- you may have to hunt
I see the two contactors look different- one appears to be missing the top cover-? Could that be the bad one?


-Mark

 

[mksj]

If the E-Stop does not work then it would be a faulty contactor that is sticking. This is a serious safety issue. You may be able to get a different brand of contactor and add an auxiliary switch block to the top and configure the same as the ones you have. Label the wires when removing them and note the connections. Contactors are usually interlocked so that when one is active the other is deactivated.

 

[markba633csi]

You might be able to find a replacement contactor on Aliexpress
It has to have a similar footprint and contact arrangement (3 normally open and 1 normally closed contacts) and have a 24 volt ac coil