Replacing lathe motor and controller

[ColeyS1]

Just wondering what your thoughts are with this situation. Years ago I bought an Axminster c6b engineering lathe cheap- it was a customer return.

Skip forward possibly 8-9 years and it's stopped working . It's not a machine that gets alot of use, but it's really useful when it does ! I'd say I haven't used it for more than 15 hours.

I turn the speed control slowly and the motor just turns ever so slightly, buzzes, zaps then stops.

The thing is I'm not sure whether it might be the motor

Or the controller thingymejig

I've found both parts on the sieg website for around 280 quid.

Searching for possible solutions I see alot of other people are replacing the two parts with upgraded versions.
As it's had so little use I'm wondering if I should bite the bullet and try and find something like this

Which hopefully might be a little more heavy duty.

I'd appreciate your thoughts. My heads going around in circles trying to figure out the best solution. By far the easiest would be a straight swap of both parts. If for a little more effort I could have a better motor etc, then perhaps I should go that route ?

Coley

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[CHJ]

If you can source a three phase motor and associated invertor kit to fit then personally that is the route I would go.

Basically a more robust and well proven setup than the brushed motor that was originally fitted.

On the electrical controls front it should not be a problem locating the switches and speed potentiometer in the original locations as opposed to in separate box as shown in your linked image.

 

[ColeyS1]

Thanks for your advice your second paragraph was exactly what I was hoping to here.
It was a great lathe for getting me interested in metal working, but it's always seemed a bit underpowered. It would just cut out after just a little resistance so a beefier more robust motor sounds perfect.
I'm guessing all my speeds would go out the window if I fit an aftermarket setup?
Must admit it sounds a rather daunting task setting up the inverter etc.

Coley

 

[CHJ]

If the invertor is supplied by one of the 'kit' companies it will be good to go for all normal use on your lathe.

Speed calibration is easy, a simple hand made scale on your speed potentiometer is all that is needed.

Cutting speed is best selected for best results with your combination of stock material, tool material and sharpening criteria, no carved in stone speeds apply, they are just guides.

You can use These calibration discs with a mains supplied incandescent lamp to check the speeds.

 

[ColeyS1]

Oh my word !!!!!!! Those discs are amazing !! I was thinking I'd have to use cotton and count how many times it wound around a bar over a certain time. - that's one less thing to worry about.

Thanks

Coley

 

[Togalosh]

Hello Coley,

Have you tried replacing the brushes or running the motor separate from the pcb to diagnose the fault ?

If you want to upgrade your lathe I would recommend https://inverterdrive.com/

I just replaced my 70yr old motor like for like without thinking (3/4 HP, 2pole ?) as I wanted to do away with phaffing with changing pulleys etc & wish I had gone for a 4 pole motor instead as it has the same torque at lower speeds & more torque over all whereas the 2 pole motor loses torque at lower speeds with the inverter.. (not sure the loss of torque is a real problem as I haven't actually got my lathe set up & running yet.. ho hum).

Togs

 

[ColeyS1]

Hi togs. Yeah I fitted new brushes and it made no difference. The motor needs the circuit board to run apparently.
It was such a precious flower when it did work so I think a better motor has to help. I'm waiting to hear from a few people to see if they can supply a motor that fits- seems like a 16mm shank isn't that common.
I'll take a look at the website. Perhaps they've got one the right size.

Cheers

Coley

 

[ColeyS1]

Did you also replace the inverter togs ?
I think I could buy both things easy enough seperately but am struggling to find a kit with the right sizes.
The reason for buying a kit was so hopefully it contains a suitable inverter to drive it.

Coley

 

[Togalosh]

I was upgrading an ML4 with pulleys... I got a new motor as I was looking to buy some type of speed controller & they were cheap & made more sense having a 3ph one.. just annoyed I got it on a whim when collecting the inverter instead of thinking more about it & getting the 4 pole model.

Your duff motor is single phase then why would you need the pcb to test the motor ?..the pcb is the speed controller so it would run at full speed if it worked at all.

You could maybe bush up a smaller shaft to 16mm.. no?

 

[ColeyS1]

To be honest I'm not entirely sure. It's a dc motor and I think it needs some type of controller to work. I think the controller changes it to 180v. It's got green, brown and blue wires.

I took your advice and called a guy from the website you suggested. He was an absolute gent and spent over 15 minutes explaining.......just everything that I needed to know about my situation. He also described what he thought had happened to the old circuit board, describing it's position in the workshop down to a t ! - condensation.
I ordered the bits last night, so think the worst parts done now. He also pointed me to a replacement pulley that would fit straight onto the new motor.
Thanks for suggesting them. Very very helpful man who managed to translate my gobbledegook of motor terminology

Coley

 

[Togalosh]

To be honest I'm not entirely sure. It's a dc motor and I think it needs some type of controller to work. I think the controller changes it to 180v. It's got green, brown and blue wires.

I took your advice and called a guy from the website you suggested. He was an absolute gent and spent over 15 minutes explaining.......just everything that I needed to know about my situation. He also described what he thought had happened to the old circuit board, describing it's position in the workshop down to a t ! - condensation.
I ordered the bits last night, so think the worst parts done now. He also pointed me to a replacement pulley that would fit straight onto the new motor.
Thanks for suggesting them. Very very helpful man who managed to translate my gobbledegook of motor terminology

Coley

Result !...why can't all suppliers be that helpful ?.

Where did you go for a pulley ?

(& as for my suggestions for your old motor I was being REALLY thick there... the pcb inverts the AC voltage to DC.. dehr.. so plugging it in wouldn't have been fun for you. That's embarrassing).

 

[graduate_owner]

I seem to remember reading that one of the weaknesses of these far east imports is the electronic motor speed control.
Regarding the 3 phase inverter, be aware that the basic ones will not tolerate having switches between inverter and motor. You must connect the motor directly to the inverter, so the existing switchgear must be bypassed.

K

 

[ColeyS1]

Where did you go for a pulley ?

Bolton bearings (via ebay) I messaged him the dimensions I needed and he messaged me the two item numbers I needed to fit the new shaft. I've ordered a taper lock pulley so it needed an outside bit and also an inner bush.
Don't worry about the ac dc mix up. I took the entire lathe to a 'motor expert' and he did exactly that - put a 240v plug on the end !! I had a bill for £108 telling me it was still broken he also advised me not to spend any more money on it......
Then there was Axminster who sold me a capacitor for it (after giving them the model number) It doesn't even have one ! I had fun trying to figure out where it fitted though.
It's kinda why I thought it best to try myself. I hate wasting stuff so can't figure out why simply starting afresh with a new motor shouldnt work. The mechanical parts of it are virtually new.
I'm a little worried that since placing/paying for the order I haven't heard anything, I just need to be patient.

Coley

 

[ColeyS1]

I seem to remember reading that one of the weaknesses of these far east imports is the electronic motor speed control.
Regarding the 3 phase inverter, be aware that the basic ones will not tolerate having switches between inverter and motor. You must connect the motor directly to the inverter, so the existing switchgear must be bypassed.

K

That might explain it failing prematurely and cutting out at the smallest amount of pressure. The inverter I've ordered is rated ip66, which should mean it'll handle any condensation. I think it may come with 5 year guarantee which is comforting.
I read the instructions a couple times and think it has input for an external potiometer (twisty speed knob) do you think I'd be better off just using the controls on the inverter then ?

Cheers

Coley

 

[CHJ]

Just ensure the main on/off NVR switch is on the mains side of the inverter input.
The inverter must be permanently wired to the motor, no switches in its 3 output wires.

The invertor will have three connection points you can wire an external potentiometer to for the speed control.
It will also have similar connection points for you to be able to switch motor rotation direction.

The switches and potentiometer can be mounted on the front panel in the place of the existing switches (you may have to fit adaptor plate to take account of hole sizes)


This is a typical circuit connection diagram of an invertor.

Top to bottom highlights:-
Mains in
Speed potentiometer
Motor direction.

 

[graduate_owner]

Hi Coley,
I would definitely connect a remote potentiometer to give you variable speed at a convenient location on the lathe body, also an on/off switch - you don't want to be reaching for the inverter if you need to switch off in a hurry.
I mounted mine (on/off and pot) in a plastic box and glued magnets to the back of the box so I can easily locate the controls on any of the machines I need 3 phase on (I have 4 so it is really handy). The various machine motors connect directly to the inverter output via 3 phase plug and flying lead socket.
As has been emphasised, you must not put any switch or variable resistor between the 3 phase output of the inverter and the motor - all controlling of speed and on/off must be done either at the inverter or via the remote leads.
There will be a load of parameters associated with the inverter, such as increased torque at low speed, ramp up and down times ( so you can have the start up speed gradually increase to full speed giving less strain on the machine) and many others that I don't even pretend to understand but tbe defult settings are likely to be fine on these anyway.

Hope this helps, and good luck with the modifications. Also apologies for any typos, my Hudl has automatically (and very annoyingly) downloaded a new keyboard which is ghastly. I seem to hit a wrong every four or five words, and going over the text to correct them is exceedingly tedious. Autocorrect is even more of a nuisance as you never know what will be on the page then.

K

 

[ColeyS1]

Thanks for all the additional info guy's, it's very much appreciated.
Fingers crossed the motor and inverter should be coming tomorrow and the pulley on Friday.
Reading the instructions I think it's also possible to wire an external on/off toggle type switch. Mine currently uses seperate switches for each so that might be something that needs altering. Providing it spins, I think I can live with a few quirks.

Coley

 

[ColeyS1]

Pleasantly surprised when the postman gave me the vee pulley this morning. TNT just dropped off the motor and inverter.

The inverters much bigger than i imagined, it looks a beast!
First thing will be check the pulley fits, then try and get the motor to fit.
Not sure where I can mount the inverter yet, but pleased all the pieces are here.

Coley

 

[ColeyS1]

Just started stripping the old electrics. Thought I'd take a peak under the cover of the new inverter.

Gulp.
This is gonna be a challenge ! I was expecting to see live neutral and earth in for normal 3 pin plug. Earth u,v and w correspond with the motor so that must be the out.
I'm gonna go back to removing the old electrics, I feel a bit overwhelmed right now :lol:
Coley

 

[DTR]

It's L1 and L2 for live and neutral, I'd imagine. Earth of course is still earth.

Edit: CHJ's diagram further up the thread has L1 as live and L2 as neutral