12 x 36 gearhead lathe

[canuck750]

I have a 12 x 36 gear head lathe, similar to a Grizzly G4003, uses many of the same parts.
The main power electrical contractor keeps tripping when I start the lathe with the control lever in forward or reverse. I have repeatedly tried electrical contact cleaner and blown out the component with compressed air but the contractor keeps tripping. If I hold the electrical contractor pop up button down while switching the machine on the lathe will run. There are three of these contractors in the lathe electrical cabinet, main switch power, forward and reverse. Only the main power contractor is acting up.
Grizzly lists this part as #53 (see attached catalog screenshot) in their online catalogue but this part is currently not in stock.
I have also sprayed electric motor cleaner into the motor and blown it out as well.
Any suggestions on why this unit is tripping, servicing this contractor or where I can purchase a replacement unit?
Thanks
Jim

 

[DavidR8]

Can you swap them around to see if there's an issue elsewhere in the chain that's causing it to trip?
That said, contactors are pretty simple devices and a replacement should be easy to source.

 

[trlvn]

What are the specs on the motor; can you get a picture of the motor tag? Is it connected to 120 or 240 volt supply. Is that circuit shared with anything?

Wild guess: could the machine have been set up for 240 volt operation and converted to 120 volt? If so, was the motor protection adjusted/replaced since it is now seeing 2X the amperage at 1/2 the volts?

Craig

 

[canuck750]

A picture of the problematic contactor, the schematic inside the late electrical panel cover and the motor plate
The machine is running on single phase 220V

 

[TorontoBuilder]

I have a 12 x 36 gear head lathe, similar to a Grizzly G4003, uses many of the same parts.
The main power electrical contractor keeps tripping when I start the lathe with the control lever in forward or reverse. I have repeatedly tried electrical contact cleaner and blown out the component with compressed air but the contractor keeps tripping. If I hold the electrical contractor pop up button down while switching the machine on the lathe will run. There are three of these contractors in the lathe electrical cabinet, main switch power, forward and reverse. Only the main power contractor is acting up.
Grizzly lists this part as #53 (see attached catalog screenshot) in their online catalogue but this part is currently not in stock.
I have also sprayed electric motor cleaner into the motor and blown it out as well.
Any suggestions on why this unit is tripping, servicing this contractor or where I can purchase a replacement unit?
Thanks
Jim

Just order a replacement CJX1-22 from aliexpress and swap it out. They're common as dirt under many different brand names but all quite fungible.

Just be sure to order the correct coil voltage... which on chinese lathes, and from a cursory look at your wiring diagram yours appears to be a 24V control circuit but I'm not attesting to that in any way. Check the old contactor it will say right one it.

22 bucks and delivery in 10 days

At that price it is not worth trying to fix these, and order two to have a spare. You will need it eventually.

CORRECTION:

Order from Amazon Canada, Baomain is the most common brand of CJX1-22 contactor, the price is higher but shipping is a lot cheaper or free with amazon prime.

 

[BaitMaster]

@canuck750 reading the diagram it looks like the things that can get in the way of KM1 running are the Estop button, start button, and FR which appears to be a thermal overload contact for the motor. This could be a separate lead to the motor or a standalone thermal overload block that the motor power circuit runs through. If it’s a standalone block then the designation for the NC contacts on the overload are 95 and 96.

You could test between 95 and 96 with an ohmmeter with all the power off of course. There may also be a manual reset button, usually red, that you could try pushing a handful of times.

You could also test continuity with an ohmmeter on that particular contact of the Estop button. That’s SB1. You could test the NO contacts on SB2 as well labeled E. you will have to press that button while testing on ohms.

You could measure the voltage over the coil of KM1 with a volt meter on volts AC, expecting 24v ac if all is well. This will be terminals labeled A1 and A2. This test obviously will be with power on trying to run (very carefully).

I would do this before ordering a contactor, as a new contactor wont fix the problem if the contactor isn’t being instructed to operate by the control circuit.

Regards.

 

[canuck750]

Toronto Builder and BaitMaster, thank you so much! I will run some tests as per your instructions and order a contractor or two for backup.

 

[Susquatch]

@canuck750 - before I did anything else, I'd meticulously check every connection from one end to the other including grounds.

With stuff like this I often find that the problem is connections, connections, connections.

After that, I agree with both @BaitMaster and @TorontoBuilder. Perhaps it's my old age that makes me check connections first. Too many years of fixing electrical stuff and chasing my tail only to find a loose screw or a bad connector.

 

[TorontoBuilder]

@canuck750 - before I did anything else, I'd meticulously check every connection from one end to the other including grounds.

With stuff like this I often find that the problem is connections, connections, connections.

After that, I agree with both @BaitMaster and @TorontoBuilder. Perhaps it's my old age that makes me check connections first. Too many years of fixing electrical stuff and chasing my tail only to find a loose screw or a bad connector.

Ironically, when you replace the contactor you end up checking every connection through said contactor

I avoid helping diagnose electrical issues so I limited my response to answering the last question the OP posed, where to buy replacement. But as baitmaster said there is a possibility that the issue is related to the overload relay.

 

[canuck750]

Thanks Toronto Builder for suggesting Amazon, I bought two of the contractors for under $60!, a fraction of what Grizzly was asking for them.

I will go through all the wiring to and from the connectors.

 

[Susquatch]

I avoid helping diagnose electrical issues so I limited my response to answering the last question the OP posed, where to buy replacement.

That's actually very good advice....... For me!

I am generally good at diagnosing electrical problems so I like to help those who are not and especially those who are.

But I end up in trouble when the guy on the other end doesn't own a multimeter..... When that happens, I prefer to go off line, and make a phone call so we can go one step at a time, and sometimes to suggest they get close by help.

 

[Susquatch]

I will go through all the wiring to and from the connectors.

I'm not sure what you mean by that. It isn't very often that the problem is in the wire between connections. Not that this never happens but other than pinched or broken wires it's rare. The most common problem is the connection itself. Maybe that's what you mean, but I didn't think I should leave it unsaid.

Connection problems take many forms. But the most common (the big three) are a loose connection, a corroded connection, and a poor wire bond to a terminal. Less common are such things as current limited connections, high resistance connections, stress connections, insulated connections, temperature sensitive connections, etc.

 

[canuck750]

Yep, I meant going through all the connections, I have a pretty good stock of open barrel crimp connections and the matching crimping tools if I need to replace anything

 

[Ironman]

It looks like there is a thermal overload FR in line. I have had the same problem on the FT3 mill and the overload was adjustable, so I wound it up to the 6 amp max setting. This terminated the problem unless I made heavy cuts. Eventually I tossed it out as the VFD offers better protection.

 

[canuck750]

Thanks Ironman, I will check that out.

 

[canuck750]

I replaced the main power contactor and still the magnetic contactor will not close without holding the black button down. I also gave all the contacts a liberal blast of electrical contact cleaner and compressed air and I cleaned the switches (E Stop, power and jog) on the front panel. There is an adjustable resistor below the three contactors in the electrical panel with a reset button attached to the door, the resistor has not tripped. I tried rotating the resistor setting and nothing makes a difference to the main contactor being able to hold closed.
My electrical knowledge is not much above flipping a light switch but I am suspecting the magnetic contact is sensing an overload and the failsafe position is to remain open.
By holding my finger on the black button of the main contact I can run the lathe forward and reverse.
When depress the E-stop button AND hold down the contact black button the lathe will continue to run.

Dazed and confused in Edmonton

Anyone with experience on these systems that has an aha moment?

 

[BaitMaster]

Have you tried vigorously and quickly depressing that little red button on the overload?

If you find the two terminals labeled 95 and 96 on the overload block, and jumper them out with a little piece of wire, then if it is the overload block it will run.

If you were more southerly in alberta I would come and help you out for a song but 6 hours is a bit of a hike.

 

[DPittman]

I replaced the main power contactor and still the magnetic contactor will not close without holding the black button down. I also gave all the contacts a liberal blast of electrical contact cleaner and compressed air and I cleaned the switches (E Stop, power and jog) on the front panel. There is an adjustable resistor below the three contactors in the electrical panel with a reset button attached to the door, the resistor has not tripped. I tried rotating the resistor setting and nothing makes a difference to the main contactor being able to hold closed.
My electrical knowledge is not much above flipping a light switch but I am suspecting the magnetic contact is sensing an overload and the failsafe position is to remain open.
By holding my finger on the black button of the main contact I can run the lathe forward and reverse.
When depress the E-stop button AND hold down the contact black button the lathe will continue to run.

Dazed and confused in Edmonton

Anyone with experience on these systems that has an aha moment?

My electrical knowledge isn't much more than yours sorry, but on myb12x36 it would kick out until I adjusted that dial.

 

[canuck750]

Have you tried vigorously and quickly depressing that little red button on the overload?

If you find the two terminals labeled 95 and 96 on the overload block, and jumper them out with a little piece of wire, then if it is the overload block it will run.

If you were more southerly in alberta I would come and help you out for a song but 6 hours is a bit of a hike.

Thank you for the reply!
I did try and depress the red button in the overload but it just stays in the down position.
I will try jumping the 95 and 96 terminals tomorrow.
Thanks agsin
Jim

 

[canuck750]

Today I held a jumper across what I think are terminals 95 and 96, the components inside my lathe electrical box are not identical to the Grizzly electrical diagram I have.



There was no change, the main power contactor will not hold the black button down while jumping the terminals.

I cleaned the switches on the front panel again hoping something would give but again no change.

In the spring I had replaced the rotary switch as I had thought it was faulty on the reverse setting but it turned out the reverse contractor was dirty. Contact cleaner seemed to resolve the reverse function.